173 results on '"Robert J. Thomas"'
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2. Raspberry Pi nest cameras: An affordable tool for remote behavioral and conservation monitoring of bird nests
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Richard J. Facey, Sara Roda, Laura Astbury, Hannah F. R. Hereward, Robert J. Thomas, Sarah E. Long, Christa L. Emmett, Matthew L. Couldwell, Jodie M. Henderson, Jack J. Devlin, Ben J. Porter, Luke Maggs, Katie H. Shaw, Sean A. Rands, Emma L. Renshaw, Alyssa J. Sargent, Hereward, Hannah FR [0000-0002-1917-1550], Rands, Sean A [0000-0002-7400-005X], Thomas, Robert J [0000-0001-5256-3313], and Apollo - University of Cambridge Repository
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interspecific interactions ,Computer science ,Real-time computing ,Raspberry Pi ,burrow‐nesting ,storm‐petrel ,law.invention ,Raspberry pi ,Nest ,law ,bespoke camera ,Nest box ,QH540-549.5 ,Research Articles ,Ecology, Evolution, Behavior and Systematics ,Bespoke ,Original Research ,Nature and Landscape Conservation ,Flexibility (engineering) ,Ecology ,Bird nest ,Software deployment ,Passive infrared sensor ,nest box ,Animal behavior ,seabirds - Abstract
Funder: Cardiff University, Funder: Project CASE partner ‐ Eco‐explore Community Interest Company, Bespoke (custom-built) Raspberry Pi cameras are increasingly popular research tools in the fields of behavioral ecology and conservation, because of their comparative flexibility in programmable settings, ability to be paired with other sensors, and because they are typically cheaper than commercially built models.Here, we describe a novel, Raspberry Pi-based camera system that is fully portable and yet weatherproof-especially to humidity and salt spray. The camera was paired with a passive infrared sensor, to create a movement-triggered camera capable of recording videos over a 24-hr period. We describe an example deployment involving "retro-fitting" these cameras into artificial nest boxes on Praia Islet, Azores archipelago, Portugal, to monitor the behaviors and interspecific interactions of two sympatric species of storm-petrel (Monteiro's storm-petrel Hydrobates monteiroi and Madeiran storm-petrel Hydrobates castro) during their respective breeding seasons.Of the 138 deployments, 70% of all deployments were deemed to be "Successful" (Successful was defined as continuous footage being recorded for more than one hour without an interruption), which equated to 87% of the individual 30-s videos. The bespoke cameras proved to be easily portable between 54 different nests and reasonably weatherproof (~14% of deployments classed as "Partial" or "Failure" deployments were specifically due to the weather/humidity), and we make further trouble-shooting suggestions to mitigate additional weather-related failures.Here, we have shown that this system is fully portable and capable of coping with salt spray and humidity, and consequently, the camera-build methods and scripts could be applied easily to many different species that also utilize cavities, burrows, and artificial nests, and can potentially be adapted for other wildlife monitoring situations to provide novel insights into species-specific daily cycles of behaviors and interspecies interactions.
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- 2021
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3. Sleep in the Intensive Care Unit through the Lens of Breathing and Heart Rate Variability: A Cross-Sectional Study
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A.R. Hemmige, Luis Paixao, M.B. Westover, S. Rajan, Parimala Velpula Krishnamurthy, Syed A. Quadri, Ezhil Panneerselvam, M. Da Silva Cardoso, Noor Adra, M. A. Ayub, Oluwaseun Akeju, Ryan A. Tesh, Haoqi Sun, B. Coughlin, Yu-Ping Shao, Wolfgang Ganglberger, Elissa Ye, S. Sydney Cash, Abigail A. Bucklin, Michael J. Leone, Robert J. Thomas, B. T. Thompson, David Kuller, and John M. Higgins
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medicine.medical_specialty ,Sleep Stages ,medicine.diagnostic_test ,business.industry ,Actigraphy ,Polysomnography ,Non-rapid eye movement sleep ,Intensive care unit ,Sleep in non-human animals ,law.invention ,law ,Emergency medicine ,Breathing ,Medicine ,Heart rate variability ,business - Abstract
BackgroundFull polysomnography, the gold standard of sleep measurement, is impractical for widespread use in the intensive care unit (ICU). Wrist-worn actigraphy and subjective sleep assessments do not measure sleep physiology adequately. Here, we explore the feasibility of estimating conventional sleep indices in the ICU with heart rate variability (HRV) and respiration signals using artificial intelligence methods.MethodsWe used deep learning models to stage sleep with HRV (through electrocardiogram) and respiratory effort (through a wearable belt) signals in critically ill adult patients admitted to surgical and medical ICUs, and in covariate-matched sleep laboratory patients. We analyzed the agreement of the determined sleep stages between the HRV- and breathing-based models, computed sleep indices, and quantified breathing variables during sleep.ResultsWe studied 102 adult patients in the ICU across multiple days and nights, and 220 patients in a clinical sleep laboratory. We found that sleep stages predicted by HRV- and breathing-based models showed agreement in 60% of the ICU data and in 81% of the sleep laboratory data. In the ICU, deep NREM (N2 + N3) proportion of total sleep duration was reduced (ICU 39%, sleep laboratory 57%, pConclusionsCardiovascular and respiratory signals encode sleep state information, which can be utilized to measure sleep state in the ICU. Using these easily measurable variables can provide automated information about sleep in the ICU.
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- 2021
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4. Performance Evaluation of a Prestressed Belitic Calcium Sulfoaluminate Cement (BCSA) Concrete Bridge Girder
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Robert J. Thomas, Raed Tawadrous, Marc Maguire, Mohammad Mastali, and Nick Markosian
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Materials science ,Geography, Planning and Development ,0211 other engineering and technologies ,TJ807-830 ,020101 civil engineering ,02 engineering and technology ,Management, Monitoring, Policy and Law ,TD194-195 ,creep ,Renewable energy sources ,0201 civil engineering ,law.invention ,prestress losses ,Prestressed concrete ,bridges ,Flexural strength ,law ,Precast concrete ,Girder ,021105 building & construction ,Shear strength ,GE1-350 ,shear strength ,drying and autogenous shrinkage ,Environmental effects of industries and plants ,Renewable Energy, Sustainability and the Environment ,business.industry ,prestressed concrete ,Structural engineering ,sustainability ,Environmental sciences ,Portland cement ,Compressive strength ,Creep ,flexural strength ,business - Abstract
Belitic calcium sulfoaluminate (BCSA) cement is a sustainable alternative to Portland cement that offers rapid setting characteristics that could accelerate throughput in precast concrete operations. BCSA cements have lower carbon footprint, embodied energy, and natural resource consumption than Portland cement. However, these benefits are not often utilized in structural members due to lack of specifications and perceived logistical challenges. This paper evaluates the performance of a full-scale precast, prestressed voided deck slab bridge girder made with BCSA cement concrete. The rapid-set properties of BCSA cement allowed the initial concrete compressive strength to reach the required 4300 psi release strength at 6.5 h after casting. Prestress losses were monitored long-term using vibrating wire strain gages cast into the concrete at the level of the prestressing strands and the data were compared to the American Association of State Highway and Transportation Officials Load and Resistance Factor Design (AASHTO LRFD) predicted prestress losses. AASHTO methods for prestress loss calculation were overestimated compared to the vibrating wire strain gage data. Material testing was performed to quantify material properties including compressive strength, tensile strength, static and dynamic elastic modulus, creep, and drying and autogenous shrinkage. The material testing results were compared to AASHTO predictions for creep and shrinkage losses. The bridge girder was tested at mid-span and at a distance of 1.25 times the depth of the beam (1.25d) from the face of the support until failure. Mid-span testing consisted of a crack reopening test to solve for the effective prestress in the girder and a flexural test until failure. The crack reopen effective prestress was compared to the AASHTO prediction and AASHTO appeared to be effective in predicting losses based on the crack reopen data. The mid-span failure was a shear failure, well predicted by AASHTO LRFD. The 1.25d test resulted in a bond failure, but nearly developed based on a moment curvature estimate indicating the AASHTO bond model was conservative.
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- 2021
5. High Prevalence of Undiagnosed Sleep Apnea in the Intensive Care Unit. Risk Factor Scores Cannot Substitute Objective Measurement
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M.B. Westover, Parimala Velpula Krishnamurthy, Oluwaseun Akeju, Haoqi Sun, Noor Adra, Ryan A. Tesh, Wolfgang Ganglberger, Luis Paixao, M. Da Silva Cardoso, Syed A. Quadri, Y. Ju, B. T. Thompson, R. Subapriya, Abigail A. Bucklin, David Kuller, John M. Higgins, M. A. Ayub, Michael J. Leone, Robert J. Thomas, A.R. Hemmige, and Ezhil Panneerselvam
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medicine.medical_specialty ,High prevalence ,law ,business.industry ,Emergency medicine ,Objective measurement ,medicine ,Sleep apnea ,Risk factor ,business ,medicine.disease ,Intensive care unit ,law.invention - Published
- 2021
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6. Exploring and Expanding Supererogatory Acts: Beyond Duty for a Sustainable Future
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Gareth R. T. White, Anthony Samuel, and Robert J. Thomas
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Economics and Econometrics ,Arts and Humanities (miscellaneous) ,Business and International Management ,Law ,General Business, Management and Accounting - Abstract
Supererogation has gained attention as a means of explaining the voluntary behaviours of individuals and organizations that are done for the benefit of others and which go above what is required of legislation and what may be expected by society. Whilst the emerging literature has made some significant headway in exploring supererogation as an ethical lens for the study of business there remain several important issues that require attention. These comprise, the lack of primary evidence upon which such examinations have been made, attention has been given to only singular pro-social acts of organizations, and the focus has been upon the actions of large organizations. Furthermore, Heyd’s (Supererogation, Cambridge University Press, 1982) original taxonomy of six supererogatory acts, comprising Moral Heroism, Beneficence, Volunteering, Favour, Forgiveness and Forbearance, has been considered to be complete and other forms of supererogatory acts have not yet been explored. In order to address these gaps this study poses the research questions: First, it studies how a single, contemporary SME performs multiple supererogatory acts in its attempts to address its social and environmental goals that go beyond CSR. Second, it seeks to gain a deeper theoretical understanding of Heyd’s (Supererogation, Cambridge University Press, 1982) taxonomy of six forms of supererogation through the capture of primary data. This research makes a three-year case study examination of a single SME that has been formally recognized for its work in addressing social and environmental issues at local, national and global levels. Primary data are acquired of the supererogatory acts that it performs through a three-year participant observation case study, utilizing 61 interviews and 3 focus groups with internal and external stakeholders. In doing so, it addresses the empirical limitations of the extant research, substantiates each of the forms that supererogatory acts may take, and makes a contribution to the theory of supererogation by identifying a further class of act that is ‘Sharing’.
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- 2021
7. Atomic Absorption and Atomic Fluorescence
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Robert J. Thomas
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Atomic fluorescence ,Materials science ,law ,Analytical chemistry ,Atomic absorption spectroscopy ,law.invention - Published
- 2020
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8. Cardiopulmonary coupling-derived sleep quality is associated with improvements in blood pressure in patients with obstructive sleep apnea at high-cardiovascular risk
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Solveig Magnusdottir, Robert J. Thomas, and Hugi Hilmisson
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medicine.medical_specialty ,Physiology ,medicine.medical_treatment ,Blood Pressure ,030204 cardiovascular system & hematology ,law.invention ,03 medical and health sciences ,0302 clinical medicine ,Randomized controlled trial ,law ,Internal medicine ,Internal Medicine ,medicine ,Humans ,030212 general & internal medicine ,Continuous positive airway pressure ,Oxygen saturation (medicine) ,Sleep Apnea, Obstructive ,Sleep hygiene ,business.industry ,Apnea ,medicine.disease ,Obstructive sleep apnea ,Blood pressure ,Cardiovascular Diseases ,Heart Disease Risk Factors ,Cohort ,Cardiology ,medicine.symptom ,Cardiology and Cardiovascular Medicine ,business ,Sleep - Abstract
OBJECTIVE Investigate if changes in objective sleep quality index (SQI) assessed through cardiopulmonary-coupling analysis impacts blood pressure (BP) in patients with obstructive sleep apnea at high-cardiovascular risk. METHODS Secondary analysis of ECG and pulse-oximetry-[oxygen saturation (SpO2)] data from the Heart Biomarker Evaluation in Apnea Treatment study, multicenter, controlled trial in patients with cardiovascular disease and moderate-severe obstructive sleep apnea, randomly assigned to intervention of healthy lifestyle and sleep hygiene education (HLSE; control group), continuous positive airway pressure (CPAP) or nocturnal supplemental oxygen (NSO). Participants with good-quality ECG-signal and SpO2-signal (n = 241) were included. RESULTS CPAP-therapy significantly improved BP, with net average improvement in mean arterial blood pressure during sleep (MAP) when compared with nocturnal supplemental oxygen-therapy or healthy lifestyle and sleep education-therapy, -3.92 (P = 0.012) and -3.83 (P = 0.016), respectively. When stratified on the basis of baseline-SQI, CPAP-therapy improves 24-h MAP -3.02 (P = 0.030) and MAP -5.00 (P = 0.001), in patients with compromised baseline-SQI (SQI
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- 2020
9. Comparison of chloride permeability methods for Alkali-Activated concrete
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Robert J. Thomas, Diego Lezama, Erandi Ariyachandra, and Sulapha Peethamparan
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chemistry.chemical_classification ,Materials science ,Diffusion ,0211 other engineering and technologies ,Slag ,Salt (chemistry) ,02 engineering and technology ,Building and Construction ,021001 nanoscience & nanotechnology ,law.invention ,Chloride permeability ,Portland cement ,chemistry ,law ,Electrical resistivity and conductivity ,visual_art ,Fly ash ,021105 building & construction ,visual_art.visual_art_medium ,General Materials Science ,Composite material ,0210 nano-technology ,Ponding ,Civil and Structural Engineering - Abstract
This paper presents the results of an experimental study of chloride permeability in alkali-activated fly ash, alkali-activated slag, and Portland cement concrete. Test methods include the rapid chloride permeability test (RCPT), AC and DC electrical resistivity, and the 90-day salt ponding test. We hypothesize that differences in pore solution chemistry between alkali-activated and Portland cement binders render electrical methods unable to accurately estimate chloride permeability in alkali-activated concrete. The present study seeks to evaluate this hypothesis by comparing results from electrical tests with diffusion coefficients from salt ponding tests. Contrary to previous claims, the RCPT provided a good estimate of chloride permeability in both alkali-activated slag and alkali-activated fly ash concrete. RCPT results showed excellent correlation with diffusion coefficients determined from salt ponding tests. Resistivity-measurements exhibited poor correlation to diffusion coefficients and overestimated the resistance to chloride ion penetration. Furthermore, AC and DC resistivity measurements showed significant disagreement for alkali-activated concrete. Finally, evidence form salt ponding tests suggests differences in chloride binding potential between alkali-activated and Portland cement concretes.
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- 2018
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10. 666 Sleep Architecture in the Intensive Care Unit As Revealed via Breathing and Heart Rate Variability
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Syed A. Quadri, Parimala Velpula Krishnamurthy, Haoqi Sun, Noor Adra, Wolfgang Ganglberger, Elissa Ye, Oluwaseun Akeju, Abigail A. Bucklin, Taylor Thompson, Madalena Da Silva Cardoso, Ryan A. Tesh, David Kuller, Michael J. Leone, M.B. Westover, and Robert J. Thomas
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medicine.medical_specialty ,medicine.diagnostic_test ,Respiratory rate ,business.industry ,Polysomnography ,Sleep architecture ,Intensive care unit ,law.invention ,law ,Physiology (medical) ,Emergency medicine ,Breathing ,Medicine ,Heart rate variability ,Neurology (clinical) ,Sleep (system call) ,business ,Sleep duration - Abstract
Introduction Sleep in the intensive care unit (ICU) is difficult to measure by conventional polysomnography. We investigated the feasibility of assessing sleep state from readily available ICU signals: heart rate variability (HRV) from electrocardiography and breathing from a wearable respiratory band. We compared findings with an age and sex matched sleep laboratory group. Methods As part of a clinical trial, 102 adult non-ventilated patients in three ICUs in the Massachusetts General Hospital wore a respiratory band. Both heart rate variability (RR-intervals) from ECG, and breathing (respiratory effort waveforms) data for up to seven days per patient were obtained. 220 age- and sex-matched subjects from a sleep lab cohort who wore the same respiratory effort band and ECG were selected for comparison. We staged sleep from the HRV and breathing data using previously published deep neural network models. We defined discordant sleep epochs as those where HRV- and breathing-based models disagreed. Agreement was computed for the following pairs: (R,R),(N1,N1),(N2,N2),(N3,N3),(N1,W),(N1,N2),(N2,N3). Results Demographics: Mean(STD) age: ICU 68(9), sleeplab 68(9); BMI: ICU 27(6), sleeplab 31(6); ICU 40% female, sleeplab 44% female; race: ICU%:Sleeplab% 90:69 White, 5:4 Black, 2:7 Asian. 34% of ICU-subjects were in a medical ICU, 66% in a surgical ICU. Mean total sleep duration in the ICU was 8.9 hours (4.5h concordant, 4.4h discordant sleep). We observed increased amounts of discordant sleep in the ICU compared with the sleeplab cohort (4.4h vs. 1h, p15 group. Conclusion HRV and respiratory-based measures can assess sleep in the ICU. The findings of increased discordant sleep in the ICU might stem from limitations of the models, fundamental changes in sleep biology during critical illness, pharmaceutical drugs, sleep fragmentation, and/or associated pathology in the ICU. Support (if any)
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- 2021
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11. Effect of Specimen Size and Curing Condition on the Compressive Strength of Alkali-Activated Concrete
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Robert J. Thomas and Sulapha Peethamparan
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Cement ,Materials science ,Mechanical Engineering ,0211 other engineering and technologies ,Superplasticizer ,020101 civil engineering ,Polymer concrete ,Sodium silicate ,02 engineering and technology ,0201 civil engineering ,law.invention ,Portland cement ,chemistry.chemical_compound ,Compressive strength ,chemistry ,law ,Fly ash ,021105 building & construction ,Geotechnical engineering ,Composite material ,Curing (chemistry) ,Civil and Structural Engineering - Abstract
Alkali-activated concrete is a rapidly emerging sustainable alternative to portland cement concrete. The compressive strength behavior of alkali-activated concrete has been reported by various studies to a limited extent, but these discussions have been based on minimal evidence. Furthermore, although it is known that specimen size has a distinct effect on the apparent compressive strength of concrete, this effect has yet to be modeled for alkali-activated concrete. This paper presents the results of a comprehensive study of the effects of curing condition (i.e., moist-cured at ambient temperature for 28 days or heat-cured at 50çC for 48 h) and specimen size on the compressive strength of sodium silicate–activated fly ash and slag cement concrete. The heat-cured strength of alkali-activated slag cement concrete was linearly related to the moist-cured strength; the former was about 5% greater than the latter. Heat curing also improved the strength of alkali-activated fly ash concrete, although the effect was greatly magnified for lower-strength mixtures and was much less significant at higher strengths. Existing size effect laws employed for portland cement concrete proved reasonably accurate in describing the effect of specimen size on the apparent strength of alkali-activated slag cement concrete. However, these existing models greatly underestimated the size effect in alkali-activated fly ash concrete; the authors suggest that this finding was the result of significant microcracking in the alkali-activated fly ash concrete.
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- 2017
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12. On drying shrinkage in alkali-activated concrete: Improving dimensional stability by aging or heat-curing
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Robert J. Thomas, Diego Lezama, and Sulapha Peethamparan
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Cement ,Heat curing ,Materials science ,0211 other engineering and technologies ,02 engineering and technology ,Building and Construction ,021001 nanoscience & nanotechnology ,Microstructure ,law.invention ,Portland cement ,law ,Fly ash ,021105 building & construction ,Alkali activated ,General Materials Science ,Composite material ,0210 nano-technology ,Curing (chemistry) ,Shrinkage - Abstract
The problem of excessive drying shrinkage in alkali-activated concrete (AAC) is well-documented in the literature. The magnitude of drying shrinkage is often three or more times that in portland cement concrete. This study investigates the effects of binder type, activator concentration, strength, age, and curing method on the manifestation of drying shrinkage in alkali-activated fly ash and slag cement concrete. Early-age shrinkage strains in excess of 1200 μe (0.12 percent strain) are observed in AAC. This is attributed to delayed hydration, microstructure refinement, and strength development. The resulting damage is far more significant than in portland cement concrete. Shrinkage and resulting damage are greatly reduced when specimens are dried at later age and after heat-curing. Alkali-activated slag cement concrete is more sensitive to water loss than portland cement or alkali-activated fly ash concrete. This results from a finer pore structure in alkali-activated slag binders.
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- 2017
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13. Numerical evaluation of the effects of fire on steel connections; Part 2: Model results
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Robert J. Thomas and Rohola Rahnavard
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020209 energy ,02 engineering and technology ,Welding ,01 natural sciences ,Displacement (vector) ,law.invention ,law ,0202 electrical engineering, electronic engineering, information engineering ,medicine ,Engineering (miscellaneous) ,Fluid Flow and Transfer Processes ,business.industry ,Stiffness ,Structural engineering ,Finite element method ,010406 physical chemistry ,0104 chemical sciences ,Connection (mathematics) ,Moment (mathematics) ,Buckling ,lcsh:TA1-2040 ,medicine.symptom ,business ,lcsh:Engineering (General). Civil engineering (General) ,Geology ,Beam (structure) - Abstract
The resistance of beam-to-column connections to fire is an important consideration for the design of steel moment frames. The authors seek to study the effect of fire on such connections using finite element modeling in ABAQUS. The previously published first part of this paper detailed and validated the simulation technique by comparing model results to experimental results reported elsewhere in the literature. This, the second part of the paper, seeks to demonstrate the performance of four types of connections exposed to thermal loading: (1) bolted end plate, (2) bolted cover plate, (3) bolted tee, and (4) welded cover plate. A numerical study was performed to quantify the effects of thermal loading on beam buckling, displacement, rotation, connection stiffness, and moment-rotation behavior at temperatures between 20 and 900 °C. The bolted end plate connection exhibited the highest resistance to thermal loading with a significantly lower degree of degradation in connection performance compared to the other three connection types. Keywords: Moment connections, Finite element analysis, Bolted tee, Temperature, Cover plate connection
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- 2019
14. Thermal damage thresholds for multiple-pulse porcine skin laser exposures at 1070 nm
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Semih S. Kumru, Aaron F. Hoffman, Adam Boretsky, Morgan S. Schmidt, Michael P. DeLisi, Amanda M. Peterson, Robert J. Thomas, David J. Stolarski, Gary D. Noojin, and Aurora D. Shingledecker
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Paper ,Materials science ,minimum visible lesion ,Infrared Rays ,Swine ,multiple pulse ,Biomedical Engineering ,laser damage ,Radiation Dosage ,law.invention ,Biomaterials ,near-infrared lasers ,law ,Animals ,Multiple pulse ,Laser power scaling ,General ,Skin ,Beam diameter ,Pulse (signal processing) ,Lasers ,Near-infrared spectroscopy ,Dose-Response Relationship, Radiation ,Laser ,Atomic and Molecular Physics, and Optics ,Electronic, Optical and Magnetic Materials ,Wavelength ,Thermography ,Swine, Miniature ,skin injury ,Heat-Shock Response ,Biomedical engineering - Abstract
As solid-state laser technology continues to mature, high-energy lasers operating in the near-infrared (NIR) band have seen increased utilization in manufacturing, medical, and military applications. Formulations of maximum permissible exposure limits establish guidelines for the safe use of these systems for a given set of laser parameters, based on past experimental and analytical studies of exposure thresholds causing injury to the skin and eyes. The purpose of our study is to characterize the skin response to multiple-pulsed laser exposures at the NIR wavelength of 1070 nm, at a constant beam diameter of 1 cm, using anesthetized Yucatan mini-pig subjects. Our study explores three constant total laser-on times of 0.01, 0.1, and 10 s as single- and multiple-pulse sequences. Exposures consisting of 10, 30, and 100 pulses have identical individual pulse durations but different duty cycles in order to include variable degrees of thermal additivity. A plurality of three observers quantifies skin damage with the minimally visible lesion metric, judged at the 1- and 24-h intervals postexposure. Calculation of the median effective dose (ED50) provides injury thresholds for all exposure conditions, based on varying laser power across subjects. The results of this study will provide a quantitative basis for the incorporation of multiple-pulsed laser exposure into standards and augment data contained in the existing ED50 database.
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- 2019
15. Concordance between Optimal Care Pathways and colorectal cancer care: Identifying opportunities to improve quality and reduce disparities
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Robert J. Thomas, Victoria White, Rebecca J Bergin, and Kathryn Whitfield
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Adult ,medicine.medical_specialty ,Referral ,Victoria ,Colorectal cancer ,Concordance ,Colonoscopy ,law.invention ,03 medical and health sciences ,law ,Health care ,medicine ,Humans ,medicine.diagnostic_test ,business.industry ,030503 health policy & services ,Health Policy ,Public Health, Environmental and Occupational Health ,Odds ratio ,medicine.disease ,Intensive care unit ,Cross-Sectional Studies ,Family medicine ,0305 other medical science ,business ,Colorectal Neoplasms ,Health care quality - Abstract
Rationale, aims, and objectives Care pathway policies for cancer aim to reduce variation and improve the quality of patient care, and there is increasing evidence that adherence to such pathways is associated with improved survival and lower health care costs. Australia is implementing Optimal Care Pathways (OCPs) for several cancers, including colorectal cancer, but studies evaluating how well care conforms to OCP recommendations are rare. This study examined concordance between OCP recommendations and colorectal cancer care prior to policy rollout and disparities for vulnerable populations. Method Cross-sectional survey (2012-2014) of cancer registry-identified colorectal cancer patients aged ≥40 approached within 6 months of diagnosis (n = 433), their general practitioner (GP, n = 290), and specialist (n = 144) in Victoria, Australia. We measured concordance with 10 OCP recommendations and variation by geography, socio-economic, and health insurance status using age- and sex-adjusted logistic regression models. Results Use of recommended GP investigations varied from 66% for colonoscopy to 13% for digital rectal exam. Recommended waiting times to receive a colonoscopy, see a specialist after referral, and begin adjuvant chemotherapy were exceeded for around a third of patients. Twenty-eight percent of specialists reported a pretreatment multidisciplinary meeting. Most patients received surgery in a hospital with an intensive care unit (92%) and chemotherapy for high risk disease (84%). In general, care was similar across sociodemographic groups. However, receipt of GP investigations tended to be higher and waiting times longer for rural, low socio-economic, and non-privately insured patients. For example, receiving a colonoscopy within 4 weeks was significantly less likely for rural (51%) than urban (78%) patients (odds ratio = 0.30; 95% confidence interval, 0.11-0.79). Conclusion Prior to implementation, a significant proportion of colorectal cancer patients received care that did not meet OCP recommendations. Low concordance and inequities for rural and disadvantaged populations highlight components of the pathway to target during policy implementation.
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- 2019
16. Simulation-based analysis of arbitrary asymmetric retinal images
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Chad A. Oian, Robert J. Thomas, and Benjamin A. Rockwell
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Hazard (logic) ,Wavelength ,Laser safety ,Computer science ,law ,Acoustics ,Bundle ,Pulse duration ,Axial symmetry ,Laser ,Power (physics) ,law.invention - Abstract
In cases where a laser source produces a pattern that is asymmetric on the retina, a modeling-based approach can be used to calculate a retinal thermal response to predict damage and make meaningful comparisons to exposure limit trends. The SESE (Scalable Effects Simulation Environment) model is a full 3D thermal finite-volume model that can simulate multiple independently controlled laser sources with unique wavelength, spatial profile, pulse duration, and power. The model is well suited to evaluate asymmetric sources since there is not an assumed axial symmetry and the spatial profile of the laser can be adjusted as a function of time. Several examples of asymmetric sources include multi-fiber bundle exposures, scanning beams, and scintillating sources. We use the SESE model to predict trends in retinal injury threshold for these cases and to help inform the laser safety community by providing estimates for safe and unsafe levels of exposure. We also introduce factors that inform hazard levels based on relative exposure conditions.In cases where a laser source produces a pattern that is asymmetric on the retina, a modeling-based approach can be used to calculate a retinal thermal response to predict damage and make meaningful comparisons to exposure limit trends. The SESE (Scalable Effects Simulation Environment) model is a full 3D thermal finite-volume model that can simulate multiple independently controlled laser sources with unique wavelength, spatial profile, pulse duration, and power. The model is well suited to evaluate asymmetric sources since there is not an assumed axial symmetry and the spatial profile of the laser can be adjusted as a function of time. Several examples of asymmetric sources include multi-fiber bundle exposures, scanning beams, and scintillating sources. We use the SESE model to predict trends in retinal injury threshold for these cases and to help inform the laser safety community by providing estimates for safe and unsafe levels of exposure. We also introduce factors that inform hazard levels based on ...
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- 2019
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17. Visible lesion threshold modeling of skin laser exposure at 1070-nm
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Nicholas J. Gamez, Elharith M. Ahmed, Michael P. DeLisi, Benjamin A. Rockwell, Robert J. Thomas, and Chad A. Oian
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Arrhenius equation ,Materials science ,business.industry ,Ranging ,Laser ,law.invention ,Wavelength ,symbols.namesake ,Optics ,law ,Thermal ,Heat transfer ,symbols ,Deposition (phase transition) ,Irradiation ,business - Abstract
Computational models are capable of quantifying the expected thermal response of biological tissue to laser irradiation. A typical laser-tissue model accounts for optical energy deposition, heat transfer, and damage assessment, with the later often represented by calculation of the Arrhenius integral. Previous studies have successfully employed these methods to predict skin damage thresholds at laser wavelengths with high absorption in water, and usually for single continuous-wave exposures. However, there remains a need for a robust and accurate predictive model in low-absorption, high-scattering cases, such as for lasers in the near-infrared (NIR) region near 1 µm, where a large volume of tissue is heated simultaneously. This study presents a framework for modeling laser irradiation of skin tissue at 1070-nm for both continuous-wave and pulsed exposures with durations ranging from 10−2 to 101 seconds. We report the modeled skin thermal responses alongside thermal camera recordings of in-vivo porcine exposures as validation of simulation integrity. Comparisons of modeled damage thresholds calculated by the Arrhenius integral with past experimentally-determined minimum visible lesion ED50 data demonstrate a high degree of accuracy. The techniques outlined by this study provide a useful tool in assessing potentially hazardous near-infrared laser exposure scenarios while informing future investigations into modeling skin laser exposure at these wavelength regions.Computational models are capable of quantifying the expected thermal response of biological tissue to laser irradiation. A typical laser-tissue model accounts for optical energy deposition, heat transfer, and damage assessment, with the later often represented by calculation of the Arrhenius integral. Previous studies have successfully employed these methods to predict skin damage thresholds at laser wavelengths with high absorption in water, and usually for single continuous-wave exposures. However, there remains a need for a robust and accurate predictive model in low-absorption, high-scattering cases, such as for lasers in the near-infrared (NIR) region near 1 µm, where a large volume of tissue is heated simultaneously. This study presents a framework for modeling laser irradiation of skin tissue at 1070-nm for both continuous-wave and pulsed exposures with durations ranging from 10−2 to 101 seconds. We report the modeled skin thermal responses alongside thermal camera recordings of in-vivo porcine exp...
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- 2019
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18. Computational modeling and damage threshold prediction of continuous-wave and multiple-pulse porcine skin laser exposures at 1070 nm
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Michael P. DeLisi, Semih S. Kumru, Nicholas J. Gamez, Benjamin A. Rockwell, Clifton D. Clark, and Robert J. Thomas
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Arrhenius equation ,Materials science ,Biomedical Engineering ,Laser ,Atomic and Molecular Physics, and Optics ,Electronic, Optical and Magnetic Materials ,law.invention ,Computational physics ,symbols.namesake ,Wavelength ,law ,Heat transfer ,Thermography ,symbols ,Deposition (phase transition) ,Continuous wave ,Irradiation ,Instrumentation - Abstract
Computational models are capable of simulating the expected thermal response of biological tissue to laser irradiation. A typical laser tissue model accounts for optical energy deposition, heat transfer, and damage assessment, with the latter often represented by calculation of the Arrhenius integral. Previous studies have successfully employed these methods to predict skin damage thresholds at laser wavelengths with high absorption in water, and usually for single continuous-wave exposures. However, there remains a need for a robust and accurate predictive model in low-absorption, high-scattering cases, such as for exposures in the near-infrared region near 1000 nm. This study presents a framework for modeling laser irradiation of skin tissue at 1070 nm for both continuous-wave and pulsed exposures with durations ranging from 10−2 to 101 s. The authors derive an optical absorption coefficient for the epidermis that agrees with expected chromophore distribution and report the modeled skin thermal responses alongside surface thermography data from in vivo porcine exposures as validation of simulation accuracy. Comparisons of modeled damage thresholds calculated by the Arrhenius integral with documented experimentally determined minimum visible lesion ED50 data exhibit a high degree of agreement. The authors also provide new Arrhenius rate process coefficients of A = 2.74 × 1094 s−1 and Ea = 5.90 × 105 J/mol, determined from experimental thermal profiles with a unique method, that demonstrate more accurate threshold predictions than those used in previous modeling studies. The techniques outlined by this study provide a useful tool in assessing potentially hazardous near-infrared laser exposure scenarios.
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- 2021
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19. Porcine skin damage thresholds for pulsed nanosecond-scale laser exposure at 1064-nm
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Aurora D. Shingledecker, Gary D. Noojin, Michael P. DeLisi, Robert J. Thomas, Morgan S. Schmidt, Amanda J. Tijerina, Amanda M. Peterson, Adam Boretsky, and Semih S. Kumru
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Materials science ,business.industry ,Pulse (signal processing) ,Irradiance ,Nanosecond ,Laser ,01 natural sciences ,law.invention ,010309 optics ,Optics ,law ,Yucatan Miniature pig ,0103 physical sciences ,Porcine skin ,Laser exposure ,Pulse energy ,business - Abstract
Pulsed high-energy lasers operating in the near-infrared (NIR) band are increasingly being used in medical, industrial, and military applications, but there are little available experimental data to characterize their hazardous effects on skin tissue. The current American National Standard for the Safe Use of Lasers (ANSI Z136.1-2014) defines the maximum permissible exposure (MPE) on the skin as either a single-pulse or total exposure time limit. This study determined the minimum visible lesion (MVL) damage thresholds in Yucatan miniature pig skin for the single-pulse case and several multiple-pulse cases over a wide range of pulse repetition frequencies (PRFs) (10, 125, 2,000, and 10,000 Hz) utilizing nanosecond-scale pulses (10 or 60 ns). The thresholds are expressed in terms of the median effective dose (ED50) based on varying individual pulse energy with other laser parameters held constant. The results confirm a decrease in MVL threshold as PRF increases for exposures with a constant number of pulses, while also noting a PRF-dependent change in the threshold as a function of the number of pulses. Furthermore, this study highlights a change in damage mechanism to the skin from melanin-mediated photomechanical events at high irradiance levels and few numbers of pulses to bulk tissue photothermal additivity at lower irradiance levels and greater numbers of pulses. The observed trends exceeded the existing exposure limits by an average factor of 9.1 in the photothermally-damaged cases and 3.6 in the photomechanicallydamaged cases.
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- 2018
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20. Alkali-activated concrete: Engineering properties and stress–strain behavior
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Robert J. Thomas and Sulapha Peethamparan
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Materials science ,Stress–strain curve ,0211 other engineering and technologies ,Young's modulus ,02 engineering and technology ,Building and Construction ,021001 nanoscience & nanotechnology ,Poisson's ratio ,law.invention ,symbols.namesake ,Portland cement ,Compressive strength ,Ground granulated blast-furnace slag ,law ,Fly ash ,021105 building & construction ,Ultimate tensile strength ,symbols ,General Materials Science ,Composite material ,0210 nano-technology ,Civil and Structural Engineering - Abstract
This paper presents an investigation into the tensile strength, modulus of elasticity, Poisson’s ratio, and stress–strain relationships of alkali-activated portland-cement-free concrete made with fly ash or ground granulated blast furnace slag (GGBFS) as the sole binder. Alkali-activated concrete is shown to be stronger in tension and have lower Poisson’s ratio than portland cement concrete. Relationships are proposed to estimate the tensile strength and modulus of elasticity based on the compressive strength of alkali-activated concrete, which are of the same form as those currently employed for portland cement concrete.
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- 2015
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21. Novel coupled-cavity sensing mechanism for on-chip detection of microparticles (Conference Presentation)
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Sara-Jayne Gillgrass, Peter Michael Smowton, and Robert J. Thomas
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Materials science ,Active laser medium ,business.industry ,Microfluidics ,Detector ,Physics::Optics ,Laser ,Particle detector ,law.invention ,Wavelength ,Optics ,law ,business ,Refractive index ,Lasing threshold - Abstract
Coupled-cavity lasers have attracted wide attention in the past, in particular for telecommunication applications where their wavelength tunability and ability for side mode suppression are desirable. The inherent sensitivity of these devices to changes in the optical coupling has also led to their proposed use in optical sensing systems. Small changes to the refractive index of the coupler section can lead to shifts in the resonance frequency of the laser. Here we present an alternative approach to coupled-cavity sensing that exploits changes to the imaginary part of the refractive index of the coupler. An optical loss, introduced to the cavity by the passage of micro-particles, influences the optical loss of the lasing mode and changes the threshold gain requirement of the laser. The sub-linear nature of the gain-current density characteristics of the quantum confined gain medium amplifies this effect, producing an even larger perturbation in output power. We demonstrate this sensing mechanism using a monolithic coupled-cavity particle detector with on-chip capillary fill microfluidics and an in-line photo-detector section for photo-voltage transduction. Both laser and detector are pulsed allowing for a time-resolved measurement to be taken.
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- 2017
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22. 3D micro-lenses for free space intra-chip coupling in photonic-integrated circuits (Conference Presentation)
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Sam Ladak, Peter Michael Smowton, Robert J. Thomas, and Gwilym I. Williams
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Microlens ,Materials science ,business.industry ,Photonic integrated circuit ,Physics::Optics ,Optical computing ,Laser ,law.invention ,Semiconductor laser theory ,Lens (optics) ,Optics ,law ,Optoelectronics ,Electronics ,business ,Lithography - Abstract
The integration of multiple optical elements on a common substrate to create photonic integrated circuits (PIC) has been successfully applied in: fibre-optic communications, photonic computing and optical sensing. The push towards III-Vs on silicon promises a new generation of integrated devices that combine the advantages of both integrated electronics and optics in a single substrate. III-V edge emitting laser diodes offer high efficiency and low threshold currents making them ideal candidates for the optically active elements of the next generation of PICs. Nevertheless, the highly divergent and asymmetric beam shapes intrinsic to these devices limits the efficiency with which optical elements can be free space coupled intra-chip; a capability particularly desirable for optical sensing applications e.g. [1]. Furthermore, the monolithic nature of the integrated approach prohibits the use of macroscopic lenses to improve coupling. However, with the advent of 3D direct laser writing, three dimensional lenses can now be manufactured on a microscopic-scale [2], making the use of micro-lens technology for enhanced free space coupling of integrated optical elements feasible. Here we demonstrate the first use of 3D micro-lenses to improve the coupling efficiency of monolithically integrated lasers. Fabricated from IP-dip photoresist using a Nanoscribe GmbH 3D lithography tool, the lenses are embedded directly onto a structured GaInP/AlGaInP substrate containing arrays of ridge lasers free space coupled to one another via a 200 μm air gap. We compare the coupling efficiency of these lasers with and without micro-lenses through photo-voltage and beam profile measurements and discuss optimisation of lens design.
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- 2017
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23. Direct numerical simulation of microcavitation processes in different bio environments
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Robert J. Thomas, Kevin J. Ly, Sy-Bor Wen, and Morgan S. Schmidt
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Pulsed laser ,Materials science ,Excimer laser ,business.industry ,medicine.medical_treatment ,Direct numerical simulation ,Laser ,01 natural sciences ,law.invention ,010309 optics ,Optics ,Corneal edema ,law ,Cavitation ,0103 physical sciences ,medicine ,Vapor bubble ,010306 general physics ,business ,Microscale chemistry - Abstract
Laser-induced microcavitation refers to the rapid formation and expansion of a vapor bubble inside the bio-tissue when it is exposed to intense, pulsed laser energy. With the associated microscale dissection occurring within the tissue, laserinduced microcavitation is a common approach for high precision bio-surgeries. For example, laser-induced microcavitation is used for laser in-situ keratomileusis (LASIK) to precisely reshape the midstromal corneal tissue through excimer laser beam. Multiple efforts over the last several years have observed unique characteristics of microcavitions in biotissues. For example, it was found that the threshold energy for microcavitation can be significantly reduced when the size of the biostructure is increased. Also, it was found that the dynamics of microcavitation are significantly affected by the elastic modules of the bio-tissue. However, these efforts have not focused on the early events during microcavitation development. In this study, a direct numerical simulation of the microcavitation process based on equation of state of the biotissue was established. With the direct numerical simulation, we were able to reproduce the dynamics of microcavitation in water-rich bio tissues. Additionally, an experimental setup in deionized water and 10% PAA gel was made to verify the results of the simulation for early micro-cavitation formation for 10% Polyacrylamide (PAA) gel in deionized water.
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- 2017
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24. Supra-threshold epidermis injury from near-infrared laser radiation prior to ablation onset
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Gary D. Noojin, Lily A. Lile, Aurora D. Shingledecker, Semih S. Kumru, Justin J. Zohner, Michael P. DeLisi, David J. Stolarski, Robert J. Thomas, and Amanda M. Peterson
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Materials science ,Laser safety ,Pulse (signal processing) ,business.industry ,medicine.medical_treatment ,Radiation ,Ablation ,Laser ,01 natural sciences ,law.invention ,010309 optics ,Lesion ,030207 dermatology & venereal diseases ,03 medical and health sciences ,0302 clinical medicine ,Optics ,medicine.anatomical_structure ,law ,Fiber laser ,0103 physical sciences ,medicine ,Epidermis ,medicine.symptom ,business - Abstract
With continued advancement of solid-state laser technology, high-energy lasers operating in the near-infrared (NIR) band are being applied in an increasing number of manufacturing techniques and medical treatments. Safety-related investigations of potentially harmful laser interaction with skin are commonplace, consisting of establishing the maximum permissible exposure (MPE) thresholds under various conditions, often utilizing the minimally-visible lesion (MVL) metric as an indication of damage. Likewise, characterization of ablation onset and velocity is of interest for therapeutic and surgical use, and concerns exceptionally high irradiance levels. However, skin injury response between these two exposure ranges is not well understood. This study utilized a 1070-nm Yb-doped, diode-pumped fiber laser to explore the response of excised porcine skin tissue to high-energy exposures within the supra-threshold injury region without inducing ablation. Concurrent high-speed videography was employed to assess the effect on the epidermis, with a dichotomous response determination given for three progressive damage event categories: observable permanent distortion on the surface, formation of an epidermal bubble due to bounded intra-cutaneous water vaporization, and rupture of said bubble during laser exposure. ED50 values were calculated for these categories under various pulse configurations and beam diameters, and logistic regression models predicted injury events with approximately 90% accuracy. The distinction of skin response into categories of increasing degrees of damage expands the current understanding of high-energy laser safety while also underlining the unique biophysical effects during induced water phase change in tissue. These observations could prove useful in augmenting biothermomechanical models of laser exposure in the supra-threshold region.
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- 2017
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25. Direct numerical simulation of the initial stage of a thermally induced microcavitation in a water-rich biotissue triggered by a nanosecond pulsed laser
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Robert J. Thomas, Sy-Bor Wen, Morgan S. Schmidt, Arun Bhaskar, and Kevin J. Ly
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Materials science ,Bubble ,Biomedical Engineering ,Direct numerical simulation ,01 natural sciences ,010305 fluids & plasmas ,law.invention ,010309 optics ,Biomaterials ,Optics ,law ,0103 physical sciences ,Thermal ,Pressure ,Physics::Atomic Physics ,Elastic modulus ,business.industry ,Lasers ,Temperature ,Water ,Nanosecond ,Laser ,Atomic and Molecular Physics, and Optics ,Avalanche breakdown ,Electronic, Optical and Magnetic Materials ,Stage (hydrology) ,business - Abstract
A numerical analysis capable of describing the early stage of a thermal microcavitation process in a water-rich biotissue without avalanche breakdown was developed. The analysis successfully reproduced the laser-induced heating, vapor bubble formation, bubble expansion, and shockwave propagation inside a water-rich biotissue during a thermal microcavitation process. Based on the analysis, it was determined that the evolution of the temperature, pressure, and laser-induced shockwave is dependent on the incident laser energy and laser pulse width. On the other hand, the early stage dynamics of the microcavitation process showed little dependence on the elastic modulus of the biotissue for the laser and tissue conditions studied.
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- 2017
26. Multiple-pulse skin damage thresholds at 1070 NM
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David J. Stolarski, Morgan S. Schmidt, Robert J. Thomas, Gary D. Noojin, Aurora D. Shingledecker, Michael P. De Lisi, Semih S. Kumru, Amanda M. Peterson, and Adam Boretsky
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Beam diameter ,Materials science ,Pulse (signal processing) ,Laser ,01 natural sciences ,030218 nuclear medicine & medical imaging ,law.invention ,010309 optics ,03 medical and health sciences ,Wavelength ,0302 clinical medicine ,law ,0103 physical sciences ,Laser exposure ,Laser power scaling ,Multiple pulse ,Skin damage ,Biomedical engineering - Abstract
As solid-state laser technology continues to mature, high-energy lasers operating in the near-infrared (NIR) band are increasingly being utilized in manufacturing, medical, and military applications. Guidelines for the safe use of these systems have been established as formulations of maximum permissible exposure (MPE) limits for a given set of laser parameters, based on past experimental studies of exposure thresholds causing injury to the skin and eyes. However, in the case of skin, these formulations do not take into account the pulse characteristics of the exposure and only utilize the total exposure duration when calculating the MPE. The purpose of this study was to characterize the skin response to multiple-pulsed high-energy laser exposure at the NIR wavelength of 1070 nm, at a constant beam diameter of 1 cm, and using anesthetized Yucatan mini-pig subjects. A constant total laser-on time was explored as single- and multiple-pulse sequences. Multiple-pulse exposures had identical individual pulse durations, and different duty cycles were employed in order to characterize the effect of variable thermal additivity. Skin damage was quantified by the minimally visible lesion (MVL) metric as judged by a plurality of three observers at the 24-hour interval post-exposure. Injury thresholds for all exposure conditions were calculated as the median effective dose (ED50), based on varying laser power across subjects. The results of this study will provide a quantitative basis for the incorporation of multiple-pulsed laser exposure into existing standards and augment data contained in the existing ED50 database.As solid-state laser technology continues to mature, high-energy lasers operating in the near-infrared (NIR) band are increasingly being utilized in manufacturing, medical, and military applications. Guidelines for the safe use of these systems have been established as formulations of maximum permissible exposure (MPE) limits for a given set of laser parameters, based on past experimental studies of exposure thresholds causing injury to the skin and eyes. However, in the case of skin, these formulations do not take into account the pulse characteristics of the exposure and only utilize the total exposure duration when calculating the MPE. The purpose of this study was to characterize the skin response to multiple-pulsed high-energy laser exposure at the NIR wavelength of 1070 nm, at a constant beam diameter of 1 cm, and using anesthetized Yucatan mini-pig subjects. A constant total laser-on time was explored as single- and multiple-pulse sequences. Multiple-pulse exposures had identical individual pulse d...
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- 2017
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27. Estimation of retina thermal response in photochemical damage studies
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Jennifer J. Hunter, Jie Zhang, Chad A. Oian, and Robert J. Thomas
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Retina ,Materials science ,Retinal ,Laser ,Photochemistry ,01 natural sciences ,law.invention ,010309 optics ,03 medical and health sciences ,chemistry.chemical_compound ,0302 clinical medicine ,medicine.anatomical_structure ,chemistry ,law ,In vivo ,0103 physical sciences ,Thermal ,030221 ophthalmology & optometry ,medicine ,Visible band ,Laser exposure ,sense organs ,Temperature response - Abstract
Computational modeling of laser-tissue interaction in the retina can be used to predict the thermal response to a laser exposure. For in vivo photochemical damage threshold experiments, where temperature rise in retinal tissue cannot be conveniently measured, modeling was used to predict retinal temperature response. Laser exposures from sixteen in vivo experiments with wavelengths in the visible band were selected to represent a wide range of powers and exposure durations. It is hypothesized that photochemical damage mechanisms were responsible for changes to subjects’ retinal tissue and that thermal response is not a significant contribution to this observed damage.Results from the model predicted peak temperature responses of less than one Kelvin in the RPE layer of the retina where the largest temperature rise would be expected. These findings support the claim that changes to retinal tissue were not directly caused by a thermally induced mechanism.Computational modeling of laser-tissue interaction in the retina can be used to predict the thermal response to a laser exposure. For in vivo photochemical damage threshold experiments, where temperature rise in retinal tissue cannot be conveniently measured, modeling was used to predict retinal temperature response. Laser exposures from sixteen in vivo experiments with wavelengths in the visible band were selected to represent a wide range of powers and exposure durations. It is hypothesized that photochemical damage mechanisms were responsible for changes to subjects’ retinal tissue and that thermal response is not a significant contribution to this observed damage.Results from the model predicted peak temperature responses of less than one Kelvin in the RPE layer of the retina where the largest temperature rise would be expected. These findings support the claim that changes to retinal tissue were not directly caused by a thermally induced mechanism.
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- 2017
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28. A double-blind, placebo-controlled randomised trial evaluating the effect of a polyphenol-rich whole food supplement on PSA progression in men with prostate cancer—the UK NCRN Pomi-T study
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Robert J. Thomas, Madeleine Williams, H. Sharma, A. Chaudry, and Patricia H. Bellamy
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Male ,Cancer Research ,medicine.medical_specialty ,Urology ,Brassica ,Placebo ,law.invention ,Curcuma ,Double-Blind Method ,Randomized controlled trial ,law ,Internal medicine ,medicine ,Humans ,Adverse effect ,watchful waiting ,Aged ,Aged, 80 and over ,Lythraceae ,Tea ,business.industry ,active surveillance ,Polyphenols ,Prostatic Neoplasms ,Middle Aged ,Prostate-Specific Antigen ,Confidence interval ,Prostate-specific antigen ,nutrition ,Endocrinology ,Blood pressure ,Oncology ,Dietary Supplements ,Disease Progression ,Original Article ,Kallikreins ,Whole food ,business ,Body mass index - Abstract
BACKGROUND: Polyphenol-rich foods such as pomegranate, green tea, broccoli and turmeric have demonstrated anti-neoplastic effects in laboratory models involving angiogenesis, apoptosis and proliferation. Although some have been investigated in small, phase II studies, this combination has never been evaluated within an adequately powered randomised controlled trial. METHODS: In total, 199 men, average age 74 years, with localised prostate cancer, 60% managed with primary active surveillance (AS) or 40% with watchful waiting (WW) following previous interventions, were randomised (2:1) to receive an oral capsule containing a blend of pomegranate, green tea, broccoli and turmeric, or an identical placebo for 6 months. RESULTS: The median rise in PSA in the food supplement group (FSG) was 14.7% (95% confidence intervals (CIs) 3.4–36.7%), as opposed to 78.5% in the placebo group (PG) (95% CI 48.1–115.5%), difference 63.8% (P¼0.0008). In all, 8.2% of men in the FSG and 27.7% in the PG opted to leave surveillance at the end of the intervention (w2 P¼0.014). There were no significant differences within the predetermined subgroups of age, Gleason grade, treatment category or body mass index. There were no differences in cholesterol, blood pressure, blood sugar, C-reactive protein or adverse events. CONCLUSIONS: This study found a significant short-term, favourable effect on the percentage rise in PSA in men managed with AS and WW following ingestion of this well-tolerated, specific blend of concentrated foods. Its influence on decision-making suggests that this intervention is clinically meaningful, but further trials will evaluate longer term clinical effects, and other makers of disease progression.
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- 2014
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29. Quantification of Thermal Lensing Using an Artificial Eye
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Ashley J. Welch, Erica L. Towle, M. Rickman, Robert J. Thomas, and Andrew K. Dunn
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Physics ,Amsler grid ,genetic structures ,business.industry ,Infrared ,Optical power ,eye diseases ,Atomic and Molecular Physics, and Optics ,law.invention ,Lens (optics) ,medicine.anatomical_structure ,Optics ,law ,Thermal ,medicine ,Optoelectronics ,Human eye ,sense organs ,Thermal blooming ,Electrical and Electronic Engineering ,business ,Energy (signal processing) - Abstract
Recent experiments have concluded that it is possible to interrupt the vision of human subjects using infrared (IR) light through an effect known as thermal lensing. While these experiments successfully demonstrated the influence of thermal lensing on an Amsler grid target, little has been done to quantify the amount of visual disruption resulting from this phenomenon. Therefore, an artificial eye system was configured to better quantify the refractive power of the thermal lens generated within the human eye. The influence of 1319 nm energy with power levels from 220 to 630 mW and exposure durations between 0.25 and 1.00 s was evaluated based on changes induced within a visible probe beam (542 nm). Results showed up to a -2.0 D blur could be induced in human subjects using these energy levels. Results also established a relationship between the peak IR power and exposure durations used to determine the strength of the thermal lens.
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- 2014
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30. Alkali-silica reactivity of alkali-activated concrete subjected to ASTM C 1293 and 1567 alkali-silica reactivity tests
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Robert J. Thomas, Sulapha Peethamparan, and Zihui Li
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Materials science ,Scanning electron microscope ,0211 other engineering and technologies ,Alkalinity ,Slag ,02 engineering and technology ,Building and Construction ,021001 nanoscience & nanotechnology ,law.invention ,Cracking ,Portland cement ,Chemical engineering ,law ,Fly ash ,visual_art ,021105 building & construction ,visual_art.visual_art_medium ,Alkali–silica reaction ,General Materials Science ,Reactivity (chemistry) ,0210 nano-technology - Abstract
This paper presents an experimental investigation of the alkali-silica reactivity of alkali-activated concrete (AAC). Some researchers suggest that the high alkalinity of the pore solution could make AAC more susceptible to alkali-silica reaction (ASR) than comparable ordinary Portland cement (OPC) concrete, perhaps even with aggregates that are normally considered non-reactive. Many have further questioned the suitability of standardized ASR test methods for use with AAC. In an attempt to resolve this controversy, the authors subjected OPC, alkali-activated fly ash (AAF), and alkali-activated slag (AAS) concrete made with both reactive and non-reactive aggregates to accelerated and long-term ASR test protocols (ASTM C1567 and C1293). Paradoxically, some AAS mixtures with non-reactive aggregates showed significant expansion while AAF mixtures with reactive aggregates expanded minimally. AAS mixtures with reactive aggregates underwent extremely high expansions. Microstructural evaluation using scanning electron microscopy revealed significant cracking but did not identify ASR gel in the majority of specimens.
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- 2019
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31. Rapid Induction of Liver Regeneration for Major Hepatectomy (REBIRTH): A Randomized Controlled Trial of Portal Vein Embolisation versus ALPPS Assisted with Radiofrequency
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Ana B Fajardo Puerta, Adam E Frampton, Nagy A. Habib, Paul Tait, Mikael H. Sodergren, Ara Darzi, Myura Nagendran, Long R. Jiao, Madhava Pai, Tamara Gall, Robert J. Thomas, Tim D. Pencavel, and Imperial College Healthcare NHS Trust- BRC Funding
- Subjects
Cancer Research ,medicine.medical_specialty ,RALPPS ,medicine.medical_treatment ,Portal vein ,hepatic resection ,portal vein embolisation ,Portal vein ligation ,lcsh:RC254-282 ,Article ,law.invention ,Muscle hypertrophy ,03 medical and health sciences ,0302 clinical medicine ,Randomized controlled trial ,law ,medicine ,Clinical endpoint ,business.industry ,portal vein ligation ,ALPPS-RF ,lcsh:Neoplasms. Tumors. Oncology. Including cancer and carcinogens ,Liver regeneration ,Surgery ,Oncology ,030220 oncology & carcinogenesis ,030211 gastroenterology & hepatology ,ALPPS ,Liver function ,Hepatectomy ,business - Abstract
To avoid liver insufficiency following major hepatic resection, portal vein embolisation (PVE) is used to induce liver hypertrophy pre-operatively. Associating liver partition with portal vein ligation for staged hepatectomy assisted with radiofrequency (RALPPS) was introduced as an alternative method. A randomized controlled trial comparing PVE with RALPPS for the pre-operative manipulation of liver volume in patients with a future liver remnant volume (FLRV) &le, 25% (or &le, 35% if receiving preoperative chemotherapy) was conducted. The primary endpoint was increase in size of the FLRV. The secondary endpoints were length of time taken for the volume gain, morbidity, operation length and post-operative liver function. Between July 2015 and October 2017, 57 patients were randomised to RALPPS (n = 29) and PVE (n = 28). The mean percentage of increase in the FLRV was 80.7 ±, 13.7% after a median 20 days following RALPPS compared to 18.4 ±, 9.8% after 35 days (p <, 0.001) following PVE. Twenty-four patients after RALPPS and 21 after PVE underwent stage-2 operation. Final resection was achieved in 92.3% and 66.6% patients in RALPPS and PVE, respectively (p = 0.007). There was no difference in morbidity, and one 30-day mortality after RALPPS (p = 0.991) was reported. RALPPS is more effective than PVE in increasing FLRV and the number of patients for surgical resection.
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- 2019
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32. Enabling time resolved microscopy with random Raman lasing
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Marlan O. Scully, Brandon Redding, Jonathan V. Thompson, Benjamin A. Rockwell, Dawson T. Nodurft, Joel N. Bixler, Robert J. Thomas, Gary D. Noojin, Vladislav V. Yakovlev, Brett H. Hokr, and Hui Cao
- Subjects
Brightness ,Multidisciplinary ,Materials science ,business.industry ,Physics::Optics ,02 engineering and technology ,Degree of coherence ,021001 nanoscience & nanotechnology ,Laser ,01 natural sciences ,Article ,law.invention ,010309 optics ,symbols.namesake ,Speckle pattern ,Optics ,Raman laser ,law ,0103 physical sciences ,symbols ,Stimulated emission ,0210 nano-technology ,business ,Raman spectroscopy ,Lasing threshold - Abstract
Optical imaging of fast events and processes is essential for understanding dynamics of complex systems. A bright flash of illuminating light is required to acquire sufficient number of photons for superior image quality. Laser pulses can provide extreme brightness and are typically employed to achieve high temporal resolution; however, the high degree of coherence associated with the lasing process degrades the image quality with speckle formation. Random lasers are low-coherence sources of stimulated emission and do not suffer from speckle, but are rather broadband and have a relatively low output power limiting the scope of their potential applications. In this report, we demonstrate the use of random Raman lasing as a novel imaging light source with unprecedented brightness for a speckle-free and narrowband light source. We showcase the advantages of a random Raman laser to image the nanosecond scale dynamics of cavitation formation in water and quantitatively compare these images to those taken with incoherent fluorescent emission and coherent laser light as illumination source.
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- 2016
33. Reconfigurable laser arrays with capillary fill microfluidics for chip-based flow cytometry (Conference Presentation)
- Author
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Robert J. Thomas
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medicine.diagnostic_test ,business.industry ,Computer science ,Microfluidics ,Cell ,Detector ,Nanotechnology ,Laser ,Chip ,law.invention ,Flow cytometry ,Semiconductor laser theory ,medicine.anatomical_structure ,law ,medicine ,Optoelectronics ,Light emission ,business ,Lithography ,Throughput (business) ,Lasing threshold ,Diode - Abstract
Low cost, portable chip based flow cytometry has great potential for applications in resource poor and point of care settings. Typical approaches utilise low cost silicon or glass substrates with light emission and detection performed either off-chip using external equipment or incorporated on-chip using ‘pick and place’ diode lasers and photo-detectors. The former approach adds cost and limits portability while the sub-micron alignment tolerances imposed by the application make the latter impractical for all but the simplest of systems. Use of an optically active semiconductor substrate, on the other hand, overcomes these limitations by allowing multiple laser/detector arrays to be formed in the substrate itself using high resolution lithographic techniques. The capacity for multiple emitters and detectors on a single chip not only enables parallel measurement for increased throughput but also allows multiple measurements to be performed on each cell as it passes through the system. Several different experiments can be performed simultaneously and throughput demand can be reduced with the facility for error checking. Furthermore, the fast switching times inherent with semiconductor lasers allows the active sections of the device to be reconfigured on a sub-microsecond time scale providing additional functionality. This is demonstrated here in a capillary fill system using pairs of laser/detectors that are operated in pulsed mode and alternated between lasing and detecting in an interleaved manner. Passing cells are alternately interrogated from opposing directions providing information that can be used to correct for differences in lateral cell position and ultimately differentiate blood cell type. © (2016) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only.
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- 2016
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34. Lighting up microscopy with random Raman lasing
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Vladislav V. Yakovlev, Benjamin A. Rockwell, Robert J. Thomas, Marlan O. Scully, Dawson T. Nodurft, Gary D. Noojin, Jonathan V. Thompson, Brett H. Hokr, Joel N. Bixler, Hui Cao, and Brandon Redding
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Fluorescence-lifetime imaging microscopy ,Microscope ,Materials science ,business.industry ,Physics::Optics ,02 engineering and technology ,021001 nanoscience & nanotechnology ,Laser ,01 natural sciences ,law.invention ,010309 optics ,symbols.namesake ,Optics ,law ,Temporal resolution ,0103 physical sciences ,Microscopy ,symbols ,Optoelectronics ,Physics::Atomic Physics ,Coherent anti-Stokes Raman spectroscopy ,0210 nano-technology ,Raman spectroscopy ,business ,Lasing threshold - Abstract
Wide-field microscopy, where full images are obtained simultaneously, is limited by the power available from speckle-free light sources. Currently, the vast majority of wide-field microscopes use either mercury arc lamps, or LEDs as the illumination source. The power available from these sources limits wide-field fluorescent microscopy to tens of microseconds temporal resolution. Lasers, while capable of producing high power and short pulses, have high spatial coherence. This leads to the formation of laser speckle that makes such sources unsuitable for wide-field imaging applications. Random Raman lasers offer the best of both worlds by producing laser-like intensities, short, nanosecond-scale, pulses, and low spatial coherence, speckle-free, output. These qualities combine to make random Raman lasers 4 orders of magnitude brighter than traditional wide-field microscopy light sources. Furthermore, the unique properties of random Raman lasers make possible the entirely new possibilities of wide-field fluorescence lifetime imaging or wide-field Raman microscopy. We will introduce the relevant physics that give rise to the unique properties of random Raman lasing, and demonstrate early proof of principle results demonstrating random Raman lasing emission being used as an imaging light source. Finally, we will discuss future directions and elucidate the benefits of using random Raman lasers as a wide-field microscopy light source.
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- 2016
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35. Evidence of Anderson localization effects in random Raman lasing
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Marlan O. Scully, Benjamin A. Rockwell, Vladislav V. Yakovlev, Robert J. Thomas, A. Douglas Stone, Jonathan V. Thompson, Alexander Cerjan, Seng Fatt Liew, Hui Cao, Brett H. Hokr, Gary D. Noojin, Luqi Yuan, and Joel N. Bixler
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Physics ,Anderson localization ,Photon ,Condensed matter physics ,02 engineering and technology ,021001 nanoscience & nanotechnology ,Laser ,01 natural sciences ,Molecular physics ,law.invention ,010309 optics ,symbols.namesake ,Raman laser ,law ,0103 physical sciences ,symbols ,Diffusion (business) ,0210 nano-technology ,Raman spectroscopy ,Lasing threshold ,Raman scattering - Abstract
Anderson localization, also known as strong localization, is the absence of diffusion in turbid media resulting from wave interference. The effect was originally predicted for electron motion, and is widely known to exist in systems of less than 3 dimensions. However, Anderson localization of optical photons in 3 dimensional systems remains an elusive and controversial topic. Random Raman lasing offers the unique combination of large gain and virtually zero absorption. The lack of absorption makes long path length, localized modes preferred. The presence of gain offsets what little absorption is present, and preferentially amplifies localized modes due to their large Q factors compared with typical low Q modes present in complex media. Random Raman lasers exhibit several experimentally measured properties that diverge from classical, particle-like, diffusion. First, the temporal width of the emission being 1 to a few nanoseconds in duration when it is pumped with a 50 ps laser is a full order of magnitude longer than is predicted by Monte Carlo simulations. Second, the random Raman laser emission is highly multi-mode, consisting of hundreds of simultaneous lasing modes. This is in contrast to early theoretical results and back of the envelope arguments that both suggest that only a few modes should be present. We will present the evidence that suggests a divergence from classical diffusion theory. One likely explanation, that is consistent with all of these anomalies, is the presence of high-Q localized modes consistent with Anderson localization.
- Published
- 2016
- Full Text
- View/download PDF
36. Suprathreshold laser injuries in excised porcine skin for millisecond exposures at 1070 nm
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Semih S. Kumru, Lily A. Lile, Chad A. Oian, Amanda M. Peterson, Gary D. Noojin, Robert J. Thomas, David J. Stolarski, Aurora D. Shingledecker, and Michael P. DeLisi
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Materials science ,Laser safety ,Infrared Rays ,Swine ,medicine.medical_treatment ,Biomedical Engineering ,Radiation Dosage ,01 natural sciences ,law.invention ,010309 optics ,Biomaterials ,030207 dermatology & venereal diseases ,03 medical and health sciences ,0302 clinical medicine ,law ,0103 physical sciences ,medicine ,Animals ,Porcine skin ,Radiation Injuries ,Skin ,Millisecond ,Laser ablation ,Skin Injury ,Lasers ,Laser ,Ablation ,Atomic and Molecular Physics, and Optics ,Electronic, Optical and Magnetic Materials ,Laser Therapy ,Liquid bubble ,Biomedical engineering - Abstract
Skin injury response to near-infrared (NIR) laser radiation between the minimum visible lesion threshold and ablation onset is not well understood. This study utilizes a 1070-nm diode-pumped Yb-fiber laser to explore the response of excised porcine skin to high-energy exposures in the suprathreshold injury region without inducing ablation. Concurrent high-speed videography is employed to determine a dichotomous response for three progressive damage categories: observable surface distortion, surface bubble formation due to contained intracutaneous water vaporization, and surface bubble rupture during exposure. Median effective dose (ED50) values are calculated in these categories for 3- and 100-ms pulses with beam diameters (1 / e2) of 3 mm (28, 35, and 49 J / cm2) and 7 mm (96, 141, and 212 J / cm2), respectively. Double-pulse cases are secondarily investigated. Experimental data are compared with the maximum permissible exposure limits and ablation onset simulated by a one-dimensional multiphysics model. Logistic regression analysis predicted injury events with ∼90 % of accuracy. The distinction of skin response into progressive damage categories expands the current understanding of high-energy laser safety while underlining the unique biophysical effects during induced water phase change in tissue. These results prove to be useful in the diagnosis and treatment of NIR laser injuries.
- Published
- 2018
- Full Text
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37. Probabilistic retinal exposure model
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Robert J. Thomas, Elharith M. Ahmed, Paul K. Kennedy, and Edward A. Early
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Retina ,Materials science ,genetic structures ,Laser safety ,business.industry ,Orientation (computer vision) ,Biomedical Engineering ,Probabilistic logic ,Eye movement ,Statistical model ,Retinal ,Laser ,eye diseases ,Atomic and Molecular Physics, and Optics ,Electronic, Optical and Magnetic Materials ,law.invention ,chemistry.chemical_compound ,Optics ,medicine.anatomical_structure ,chemistry ,law ,medicine ,sense organs ,business ,Instrumentation - Abstract
Exposure of retinal tissue to a laser source requires two conditions: the person must be exposed to the laser beam and the laser must be in his/her optical field-of-view. The authors have developed a probabilistic model for the second condition. This model is based on random eye movements, known as saccades, about a look direction. This direction is an input to the model and is known either from head orientation or a task. The model calculates the instantaneous probability that the laser is in the optical field-of-view of the retinal tissues of fovea, macula, and retina. Because of saccades, the location of exposure will change several times a second. The duration of laser exposure for the look direction is then used to calculate the probability that the retinal tissue is exposed at least once, based on independent exposures from the saccades. The concepts and equations of the model are presented, along with example calculations from applying the model to a specific exposure scenario. For a given retinal tissue optical field-of-view, the primary contributor to the probability of exposure is the angle between the look direction and the laser.Exposure of retinal tissue to a laser source requires two conditions: the person must be exposed to the laser beam and the laser must be in his/her optical field-of-view. The authors have developed a probabilistic model for the second condition. This model is based on random eye movements, known as saccades, about a look direction. This direction is an input to the model and is known either from head orientation or a task. The model calculates the instantaneous probability that the laser is in the optical field-of-view of the retinal tissues of fovea, macula, and retina. Because of saccades, the location of exposure will change several times a second. The duration of laser exposure for the look direction is then used to calculate the probability that the retinal tissue is exposed at least once, based on independent exposures from the saccades. The concepts and equations of the model are presented, along with example calculations from applying the model to a specific exposure scenario. For a given retinal ...
- Published
- 2018
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38. Ex-CARS: exotic configuration for coherent anti-Stokes Raman scattering microspectroscopy utilizing two laser sources
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Georgi I. Petrov, Michael L. Denton, Robert J. Thomas, Gary D. Noojin, Vladislav V. Yakovlev, and Corey A. Harbert
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Infrared Rays ,Physics::Optics ,General Physics and Astronomy ,Spectrum Analysis, Raman ,Signal ,Article ,General Biochemistry, Genetics and Molecular Biology ,law.invention ,symbols.namesake ,Optics ,Raman cooling ,law ,General Materials Science ,Physics::Atomic Physics ,Coherent anti-Stokes Raman spectroscopy ,Titanium ,Chemistry ,business.industry ,Lasers ,General Engineering ,General Chemistry ,Laser ,X-ray Raman scattering ,symbols ,Continuous wave ,business ,Raman spectroscopy ,Raman scattering - Abstract
We propose and experimentally demonstrate a new coherent anti-Stokes Raman scattering setting, which relies on a coherent excitation of Raman vibration using a broadband ultrashort laser pulse and signal read-out using a conventional continuous wave laser radiation. Such an exotic arrangement does not require any synchronization of two laser sources and can be used for direct comparison of amplitudes of nonlinear and spontaneous Raman signals. Ex-CARS in time- (top panel) and frequency- (bottom panel) domain.
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- 2010
- Full Text
- View/download PDF
39. Confocal Imaging of Thermal Lensing Induced by Near-IR Laser Radiation in an Artificial Eye
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Ashley J. Welch, Rebecca L. Vincelette, Benjamin A. Rockwell, Jeffrey W. Oliver, and Robert J. Thomas
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Physics ,business.industry ,Physics::Optics ,Radiation ,Laser ,Beam parameter product ,Atomic and Molecular Physics, and Optics ,law.invention ,Lens (optics) ,Wavelength ,Optics ,law ,Optoelectronics ,Thermal blooming ,Laser beam quality ,Electrical and Electronic Engineering ,business ,Equivalent input - Abstract
A custom confocal imaging system was built and used to record a probe beam's spatiotemporal response to a thermal lens induced by a near-IR laser radiation source in a water-filled artificial eye. The IR laser radiation input power levels were varied between 150 and 890 mW at wavelengths of 1110, 1130, 1150 and 1318 nm in order to determine the strength of the resulting thermal lens as a function of time, input power, and wavelength. A high-frame-rate camera captured the probe beam's logarithmic excitation and exponential decay caused by the thermal lens (supplemental video data are provided). Data showed that for equivalent input powers and beam geometries, thermal lensing was strongest for the 1150-nm laser radiation wavelength followed by 1130, 1318 and 1110 nm.
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- 2010
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40. 0572 High Residual Apnea Burden may Contribute to Frequent Outcome Failure in Randomized Controlled Trials of Positive Airway Pressure - a Proof-of-Concept Study
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Christopher N. Schmickl, S Chalise, P V Borker, Robert J. Thomas, and A Strang
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medicine.medical_specialty ,business.industry ,Apnea ,Residual ,Outcome (game theory) ,law.invention ,Randomized controlled trial ,Proof of concept ,law ,Physiology (medical) ,Positive airway pressure ,medicine ,Neurology (clinical) ,medicine.symptom ,Intensive care medicine ,business - Published
- 2018
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41. Internal Curing to Mitigate Cracking in Rapid Set Repair Media
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Marc Maguire, Robert J. Thomas, and Ivan Quezada
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Materials science ,Polymers and Plastics ,0211 other engineering and technologies ,Metals and Alloys ,020101 civil engineering ,02 engineering and technology ,0201 civil engineering ,law.invention ,Slump ,Portland cement ,Cracking ,Compressive strength ,Creep ,Mechanics of Materials ,law ,021105 building & construction ,Ultimate tensile strength ,Materials Chemistry ,Ceramics and Composites ,Composite material ,Curing (chemistry) ,Civil and Structural Engineering ,Shrinkage - Abstract
Rapid hydration and high early strength portland cement and calcium sulfoaluminate (CSA) concretes are commonly used as pavement repair media. Field trials reveal a tendency to crack along the longitudinal axis of the repair. The authors hypothesized that internal curing with saturated lightweight aggregate would prevent or delay restrained shrinkage cracking in the rapid repair media. The fresh properties (slump, setting time), mechanical properties (elastic modulus, compressive and tensile strength), and volume stability (autogenous shrinkage, drying shrinkage, restrained ring shrinkage, creep) of the rapid repair media were evaluated with and without internal curing with saturated lightweight aggregate. Despite delayed hydration and reduced early-age strength, internally cured concretes could retain the requisite minimum 4-hour compressive strength of 4,000 psi. Significant improvements in volume stability were also noted. Drying and autogenous shrinkage were reduced by factors up to 20 % and 50 %. However, detrimentally, creep shrinkage was increased by factors up to 45 %, respectively. The time to cracking in restrained ring shrinkage tests was increased by factors up to 60 %. These results indicate that internal curing can successfully improve volume stability and mitigate restrained shrinkage cracking in rapid repair media without compromising fresh properties or ultimate mechanical strength.
- Published
- 2018
- Full Text
- View/download PDF
42. Stimulated Raman scattering: old physics, new applications
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Georgi I. Petrov, Hao Zhang, Marlan O. Scully, Gary D. Noojin, Michael L. Denton, Vladislav V. Yakovlev, and Robert J. Thomas
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Physics ,business.industry ,technology, industry, and agriculture ,Physics::Optics ,Ultrafast optics ,Nonlinear optics ,Selective excitation ,Laser ,Article ,Atomic and Molecular Physics, and Optics ,law.invention ,symbols.namesake ,Optics ,law ,symbols ,Optoelectronics ,Physics::Atomic Physics ,Stimulated raman ,business ,Raman spectroscopy ,Ultrashort pulse ,Raman scattering - Abstract
Stimulated Raman scattering as a promising way of expanding the tunability of ultrafast lasers and as an exciting new biomedical imaging modality capable of selective excitation and chemically-specific diagnostics of molecular species.
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- 2009
- Full Text
- View/download PDF
43. Trends in retinal damage thresholds from 100-millisecond near-infrared laser radiation exposures: A study at 1,110, 1,130, 1,150, and 1,319 nm
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Benjamin A. Rockwell, Rebecca L. Vincelette, Aurora D. Shingledecker, Robert J. Thomas, Dave J. Stolarski, Kurt J. Schuster, Ashley J. Welch, Gary D. Noojin, Semih S. Kumru, and Jeffrey W. Oliver
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Retina ,Refractive error ,Materials science ,Laser safety ,business.industry ,Dermatology ,Radiation ,Laser ,medicine.disease ,Non-ionizing radiation ,law.invention ,medicine.anatomical_structure ,Optics ,law ,Cornea ,medicine ,Surgery ,business ,Absorption (electromagnetic radiation) - Abstract
Background and Objectives Retinal damage thresholds from 100-millisecond exposures to laser radiation for wavelengths between 1,100 and 1,350 nm have never previously been established. We sought to determine the retinal damage threshold for 100-millisecond exposures of near-infrared (NIR) laser radiation wavelengths at 1,110, 1,130, 1,150, and 1,319 nm. These data were then used to create trends for retinal damage thresholds over the 1,100–1,350 nm NIR region based upon linear absorption of laser radiation in ocular media and chromatic dispersion of the eye. Materials and Methods The paramacula and macula areas of the retina in Macaca mulatta (rhesus) subjects were exposed for 100 milliseconds to NIR laser radiation wavelengths using a Coherent OPO laser for 1,110, 1,130, and 1,150 nm and a Lee laser for 1,319 nm. Probit analysis was used to establish the estimated damage threshold in the retina for 50% of exposures (ED50). Using trends of transmitted energy to the retina, refractive error of the eye and linear absorption of the retina, a scaling factor (SF) method was created to fit the experimental data, predicting retinal damage thresholds over the 1,100–1,350 nm region. Results The experimental retinal damage threshold, ED50, for 100-millisecond exposures for laser radiation wavelengths at 1,110, 1,130, and 1,319 nm were determined to be 193, 270, and 13,713 mW of power delivered to the cornea, respectively. The retinal damage threshold for the 1,150 nm wavelength was statistically undetermined due to laser-power limitations, but was achieved in one out of three subjects tested. Conclusion The SF predicts the experimental 100- millisecond NIR ED50 value for wavelengths between 1,100 and 1,350 nm. Lasers Surg. Med. 41:382–390, 2009. © 2009 Wiley-Liss, Inc.
- Published
- 2009
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44. The Influence of Generator Scheduling and Time-Varying Fault Rates on Voltage Sag Prediction
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Gilsoo Jang, Chang-Hyun Park, and Robert J. Thomas
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Engineering ,business.industry ,Stochastic process ,Energy Engineering and Power Technology ,System testing ,law.invention ,Scheduling (computing) ,Electric power system ,Control theory ,law ,Electrical network ,Voltage sag ,Power electronics ,Electronic engineering ,Electrical and Electronic Engineering ,business ,Voltage - Abstract
This paper discusses the influence of generator scheduling and time-varying fault rates on the stochastic prediction of voltage sags. Typically, in the stochastic prediction of voltage sags, the annual expected sag frequencies (ESFs) at sensitive load points are calculated by assuming that the operating conditions and topology of the power system remain unchanged and fault rates of system components are constant throughout a year. In this paper, in order to obtain reasonable accuracy in predicting the annual ESFs at sensitive load points, the variation of fault rates due to adverse weather and the effect of generator scheduling are considered. The study was performed on the IEEE 30-bus test system. Two buses were randomly selected and the ESFs at the selected buses were calculated for different cases (i.e., with and without incorporation of time-varying fault rates and the operation schedule of generators in the system).
- Published
- 2008
- Full Text
- View/download PDF
45. Dynamic bidirectional reflectance distribution functions: Measurement and representation
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Edward A. Early, Robert J. Thomas, Albert Bailey, Victor Ivan Villavicencio, Kenneth S. Keppler, Justin J. Zohner, George Megaloudis, and Paul K. Kennedy
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Materials science ,Laser safety ,business.industry ,Biomedical Engineering ,Spherical harmonics ,Laser ,Atomic and Molecular Physics, and Optics ,Electronic, Optical and Magnetic Materials ,law.invention ,Optics ,Distribution function ,law ,Radiance ,Specular reflection ,Bidirectional reflectance distribution function ,business ,Instrumentation ,Beam (structure) - Abstract
With high-energy lasers, not only the direct laser beam can pose significant eye and skin hazards, but also light reflecting off material illuminated by the beam. Proper hazard analysis for a material irradiated by a laser relies upon the reflecting properties of the material surface, as these properties determine the magnitude and direction of the reflected laser energy commonly characterized by the bidirectional reflectance distribution function (BRDF). However, a high-energy laser heating and possibly melting a material can change the reflecting properties of that material, so these changes must be included in the hazard analysis. Traditional methods for measuring the BRDFs of materials are not practical for measurement of materials with rapidly-changing surface properties. However, BRDF measurement by imagery of a witness screen allows for practical measurements of the dynamically-changing BRDFs of materials under high-energy laser irradiation. Using this technique, the dynamic BRDFs of stainless stee...
- Published
- 2008
- Full Text
- View/download PDF
46. Performance comparison of Bluetooth scatternet formation protocols for multi-hop networks
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Zhifang Wang, Zygmunt J. Haas, and Robert J. Thomas
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Scatternet ,Computer Networks and Communications ,Computer science ,business.industry ,Distributed computing ,Bluetooth scatternet ,Hop (networking) ,law.invention ,Bluetooth ,Piconet ,law ,Performance comparison ,Electrical and Electronic Engineering ,business ,Information Systems ,Computer network - Abstract
The interest in Bluetooth technology has stimulated much research in algorithms for topology creation and control of networks comprised of large numbers of Bluetooth devices. In particular, the issue of scatternet formation has been addressed by researchers in a number of papers in the technical literature. This paper is an extension of the work presented in [14, 15]. In this paper we present a complete description of what we believe to be a promising scatternet formation protocol --- BlueNet, which was first proposed in [15]. Some modifications and enhancements are made to improve the connectivity of resulting scatternets. The metrics are chosen to evaluate the performance of resulting scatternets, such as the reliability, the routing efficiency, the piconet density, and the information carrying capacity. Based on the chosen metrics, performance is then compared among the scatternet samples generated by BlueNet and other two representative multi-hop scatternet formation protocols, i.e., BlueTrees [16] and LSBS [1]. Finally in the conclusion a discussion is presented on the compared scatternet formation protocols.
- Published
- 2007
- Full Text
- View/download PDF
47. Procedure for the computation of hazards from diffusely scattering surfaces under the Z136.1-2000 American National Standard for Safe Use of Lasers
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R. James Rockwell, Benjamin A. Rockwell, Robert C. Aldrich, Wesley J. Marshall, Mary F. Gorschboth, Sheldon A. Zimmerman, and Robert J. Thomas
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Hazard (logic) ,Engineering ,Laser safety ,business.industry ,Ansi standards ,Computation ,Biomedical Engineering ,Electrical engineering ,Laser ,Atomic and Molecular Physics, and Optics ,Occupational safety and health ,Electronic, Optical and Magnetic Materials ,law.invention ,Reliability engineering ,law ,National standard ,business ,Instrumentation - Abstract
The current national consensus standard for laser safety in the United States is the American National Standard for Safe Use of Lasers (ANSI Z136.1). The most recent standard, Z136.1-2000, incorporates a wealth of recent bioeffects data and established a number of new maximum permissible exposure (MPE) limits for laser safety. The standard also includes recent procedures for the computation of MPE values from large or extended diffusely scattering sources, which must be understood by health physicists, laser safety officers, and others in the field of occupational safety. Here we present the fourth in a series of tutorial articles, written to clarify laser safety analysis procedures under this standard, with an emphasis on the MPE computation methods related to extended sources, and the determination of nominal hazard zones.
- Published
- 2007
- Full Text
- View/download PDF
48. Integrated III–V semiconductor flow cytometer with capillary fill micro-fluidics
- Author
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Sara-Jayne Gillgrass, Peter Michael Smowton, Angela Sobiesierski, Robert J. Thomas, Huw D. Summers, M. Holton, and Denise Barrow
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Materials science ,business.industry ,Capillary action ,Microfluidics ,Nanotechnology ,Laser ,Noise floor ,Photodiode ,law.invention ,Volumetric flow rate ,Flow (mathematics) ,law ,Optoelectronics ,Spiral (railway) ,business - Abstract
The potential of the device is demonstrated through the results of a micro-bead counting experiment. A 0.5 µl sample volume containing 10 µm polystyrene micro-beads in Dl water is deposited into an on-chip inlet reservoir from where it flows, under capillary action, through a buried flow cell. A laser on one side of the cell is forward biased and the opposing laser is operated as a photodiode (Fig. 2(a)). Both are pulsed to provide sub-µs time-resolution of bead transit ‘events’ with a 30 mV noise floor that affords a large dynamic range of over 1.2 V (Fig. 2(b)). After passing through the flow cell the sample fluid is drawn into a spiral patterned exit reservoir that provides sufficient pull through to sustain a continuous flow for over 30 s with flow rate of > 4mm/s.
- Published
- 2015
- Full Text
- View/download PDF
49. Temperature dependence of nanosecond laser pulse thresholds of melanosome and microsphere microcavitation
- Author
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Benjamin A. Rockwell, Paul K. Kennedy, Morgan S. Schmidt, Gary D. Noojin, and Robert J. Thomas
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Materials science ,Infrared Rays ,Biomedical Engineering ,Lasers, Solid-State ,01 natural sciences ,law.invention ,010309 optics ,Biomaterials ,030207 dermatology & venereal diseases ,03 medical and health sciences ,0302 clinical medicine ,Optics ,law ,0103 physical sciences ,Animals ,Irradiation ,Absorption (electromagnetic radiation) ,Melanosome ,Melanosomes ,Pulse (signal processing) ,business.industry ,Near-infrared spectroscopy ,Temperature ,Nanosecond ,Laser ,Atomic and Molecular Physics, and Optics ,Microspheres ,Electronic, Optical and Magnetic Materials ,Biophysics ,Cattle ,business ,Visible spectrum - Abstract
Melanosome microcavitation is the threshold-level retinal pigment epithelium (RPE) damage mechanism for nanosecond (ns) pulse exposures in the visible and near-infrared (NIR). Thresholds for microcavitation of isolated bovine RPE melanosomes were determined as a function of temperature (20 to 85°C) using single ns laser pulses at 532 and 1064 nm. Melanosomes were irradiated using a 1064-nm Q-switched Nd:YAG (doubled for 532-nm irradiation). For comparison to melanosome data, a similar temperature (20 to 65°C) dependence study was also performed for 532 nm, ns pulse exposures of black polystyrene microbeads. Results indicated a decrease in the microcavitation average radiant exposure threshold with increasing sample temperature for both 532- and 1064-nm single pulse exposures of melanosomes and microbeads. Threshold data and extrapolated nucleation temperatures were used to estimate melanosome absorption coefficients in the visible and NIR, and microbead absorption coefficients in the visible, indicating that melanin is a better absorber of visible light than black polystyrene. The NIR melanosome absorption coefficients ranged from 3713 cm−1 at 800 nm to 222 cm−1 at 1319 nm. These data represent the first temperature-dependent melanosome microcavitation study in the NIR and provide additional information for understanding melanosome microcavitation threshold dependence on wavelength and ambient temperature.
- Published
- 2015
50. A narrow-band speckle-free light source via random Raman lasing
- Author
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Vladislav V. Yakovlev, Hui Cao, Brett H. Hokr, Gary D. Noojin, Morgan S. Schmidt, Joel N. Bixler, Brandon Redding, Phillip N. Dyer, Marlan O. Scully, Benjamin A. Rockwell, and Robert J. Thomas
- Subjects
Brightness ,Materials science ,FOS: Physical sciences ,Physics::Optics ,02 engineering and technology ,01 natural sciences ,7. Clean energy ,law.invention ,010309 optics ,symbols.namesake ,Speckle pattern ,Optics ,Light source ,law ,0103 physical sciences ,business.industry ,021001 nanoscience & nanotechnology ,Laser ,Atomic and Molecular Physics, and Optics ,Raman laser ,symbols ,0210 nano-technology ,Raman spectroscopy ,business ,Lasing threshold ,Light-emitting diode ,Optics (physics.optics) ,Physics - Optics - Abstract
Currently, no light source exists which is both narrow-band and speckle-free with sufficient brightness for full-field imaging applications. Light emitting diodes (LEDs) are excellent spatially incoherent sources, but are tens of nanometers broad. Lasers on the other hand can produce very narrow-band light, but suffer from high spatial coherence which leads to speckle patterns which distort the image. Here we propose the use of random Raman laser emission as a new kind of light source capable of providing short-pulsed narrow-band speckle-free illumination for imaging applications.
- Published
- 2015
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