161 results on '"Tan, Jonathan"'
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2. The effect of myeloablative radiation on urinary bladder mast cells.
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Smith, Jessica, Tan, Jonathan Kah Huat, Short, Christie, O’Neill, Helen, and Moro, Christian
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Radiation-induced cystitis is an inflammatory condition affecting the urinary bladder, which can develop as a side effect of abdominopelvic radiotherapy, specifically external-beam radiation therapy or myeloablative radiotherapy. A possible involvement of mast cells in the pathophysiology of radiation-induced cystitis has been indicated in cases of external-beam radiation therapy; however, there is no evidence that these findings apply to the myeloablative aetiology. As such, this study investigated potential changes to urinary bladder mast cell prevalence when exposed to myeloablative radiation. Lethally irradiated C57BL/6J mice that received donor rescue bone marrow cells exhibited an increased mast cell frequency amongst host leukocytes 1 week following irradiation. By 4 weeks, no significant difference in either frequency or cell density was observed. However mast cell diameter was smaller, and a significant increase in mast cell number in the adventitia was observed. This study highlights that mast cells constitute a significant portion of the remaining host leukocyte population following radiation exposure, with changes to mast cell distribution and decreased cell diameter four weeks following radiation-induced injury. [ABSTRACT FROM AUTHOR]
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- 2024
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3. The identification of diurnal variations on circulating immune cells by finger prick blood sampling in small sample sizes: a pilot study.
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Bushell, Dayna, Tan, Jonathan Kah Huat, Smith, Jessica, and Moro, Christian
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FLOW cytometry , *LEUCOCYTES , *T cells , *ACADEMIC medical centers , *BLOOD testing , *STATISTICAL hypothesis testing , *T-test (Statistics) , *KILLER cells , *SAMPLE size (Statistics) , *IMMUNODIAGNOSIS , *CIRCADIAN rhythms , *DATA analysis software , *TIME , *CELL surface antigens - Abstract
Objective There are well-described impacts of biological rhythms on human physiology. With the increasing push for routine blood tests for preventative medical care and clinical and physiological research, optimizing effectiveness is paramount. This study aimed to determine whether it is feasible to assess diurnal variations of peripheral lymphocyte prevalence using finger prick blood in a small sample size. Methods Using polychromatic flow cytometry, the prevalence of lymphocytes was assessed using 25 µL fingertip blood samples at 8 AM and 5 PM from 8 participants. Results TH cells and B cells showed significantly higher percentages in the 5 PM samples, whereas NK cells demonstrated a significantly higher morning percentage. T cells, leukocytes, and cytotoxic T cells showed no significant changes. Conclusion The detection of diurnal variations demonstrates that small blood volumes can be used to detect lymphocyte variations. The lower blood volume required provides a new testing method for clinical and research settings. [ABSTRACT FROM AUTHOR]
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- 2024
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4. On the Lifetime of Molecular Clouds with the "Tuning-fork" Analysis.
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Koda, Jin and Tan, Jonathan C.
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STELLAR oscillations , *INTERSTELLAR medium , *GALACTIC evolution , *MOLECULAR clouds , *GALAXIES - Abstract
The "tuning-fork" (TF) analysis of CO and H α emission has been used to estimate the lifetimes of molecular clouds in nearby galaxies. With simple model calculations, we show that this analysis does not necessarily estimate cloud lifetimes, but instead captures a duration of the cloud evolutionary cycle, from dormant to star-forming, and then back to a dormant phase. We adopt a hypothetical setup in which molecular clouds (e.g., traced in CO) live forever and form stars (e.g., H ii regions) at some frequency, which then drift away from the clouds. The TF analysis still returns a timescale for the immortal clouds. This model requires drifting motion to separate the newborn stars from the clouds, and we discuss its origin. We also discuss the physical origin of the characteristic spatial separation term in the TF analysis and a bias due to systematic error in the determination of the reference timescale. [ABSTRACT FROM AUTHOR]
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- 2023
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5. Prevalence and burden of diabetes mellitus-related symptoms in patients with type 2 diabetes mellitus: A cross-sectional study.
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Yuet Han Tan, Jonathan and Chirk Jenn Ng
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TYPE 2 diabetes , *SYMPTOM burden , *PATIENT satisfaction , *NON-communicable diseases , *STATISTICAL sampling - Abstract
Introduction: Type 2 diabetes mellitus (T2DM) is a significant non-communicable disease in Malaysia, with a prevalence of 18.1%, per the National Health and Morbidity Survey. This study aimed to determine the prevalence and burden of diabetes mellitus-related symptoms and whether these symptoms were addressed by primary care doctors. Methods: This 1-month cross-sectional study was conducted at an urban hospital-based primary care clinic in Malaysia. Patients with T2DM were recruited using systematic random sampling. Participants answered a self-administered questionnaire adapted from the Diabetes Symptom Checklist-Revised, which evaluated the sociodemographic characteristics, burden of diabetes mellitus-related symptoms in the past month and post-consultation feedback about symptoms. Data were analysed using SPSS. Results: Four hundred eighteen participants were included, yielding a response rate of 97.7%. Hyperglycaemia was the most prevalent symptom, with 48.1% of the participants reporting a frequent need to empty their bladder. Most participants experienced a low symptom burden, so 56.7% did not report their symptoms to their doctors. The participants who reported their symptoms had a higher symptom burden. Among them, 97.5% indicated that their doctors addressed their symptoms. Approximately 78% reported satisfaction and good coping skills when their symptoms were addressed. Conclusion: Hyperglycaemia was the most prevalent diabetes mellitus-related symptom among the patients with T2DM. The symptom burden was generally low, so most patients did not report their symptoms to their doctors. Those who reported their symptoms had a higher symptom burden. Further studies must explore why patients do not report their symptoms and how doctors address patients' symptoms. [ABSTRACT FROM AUTHOR]
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- 2023
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6. Rate of Total Hip Replacement after Legg Calve Perthes Disease in a Canadian Province.
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Tan, Jonathan, Sharma, Anirudh, Bansal, Rohit, Tan, Qier, Prior, Heather J., McRae, Sheila, and McCammon, James R.
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TOTAL hip replacement , *CANADIAN provinces , *MEDICAL care , *HIP fractures , *TENOTOMY , *PEDIATRIC orthopedics , *BLADDER exstrophy - Abstract
Legg Calve Perthes disease is a pediatric hip condition that leads to early hip degeneration. The efficacy of operative and nonoperative treatment is not well defined in the literature. Using the rate of total hip arthroplasty as a surrogate measure for symptomatic hip degeneration, the rate of total hip arthroplasty was compared in Legg Calve Perthes disease patients with and without previous surgical intervention in the province of Manitoba, Canada. A retrospective review was conducted using de-identified, individual-level administrative records of health services for the entire population of Manitoba. Codes for Legg Calve Perthes disease, femoral osteotomies, pelvic osteotomies, adductor tenotomies, and total hip arthroplasty were searched from 1984 to 2018. The rate of total hip arthroplasty in patients with Legg Calve Perthes disease was determined for two groups: (1) patients with earlier surgical intervention and (2) patients with no previous surgical intervention. Of the 202 patients included in the study, 180 had no prior surgery and 22 had prior surgery. The rate of total hip arthroplasty between the previous operative and nonoperative groups was found to be 32% and 40%, respectively (p = 0.458). There was no significant difference in rates of total hip arthroplasty in the operative and nonoperative groups. Further prospective studies are required to elucidate the differences in outcomes between operative and nonoperative treatment groups in patients with Legg Calve Perthes disease. [ABSTRACT FROM AUTHOR]
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- 2023
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7. Organic Biosignature Degradation in Hydrothermal and Serpentinizing Environments: Implications for Life Detection on Icy Moons and Mars.
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Tan, Jonathan S.W., Salter, Tara L., Watson, Jonathan S., Waite, J. Hunter, and Sephton, Mark A.
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NATURAL satellites , *SOLAR system , *ULTRABASIC rocks , *HYDROTHERMAL alteration , *MINERAL waters , *INNER planets - Abstract
Evidence of liquid water is a primary indicator of habitability on the icy moons in our outer solar system as well as on terrestrial planets such as Mars. If liquid water-containing environments host life, some of its organic remains can be fossilized and preserved as organic biosignatures. However, inorganic materials may also be present and water-assisted organic–inorganic reactions can transform the organic architecture of biological remains. Our understanding of the fate of these organic remains can be assisted by experimental simulations that monitor the chemical changes that occur in microbial organic matter due to the presence of water and minerals. We performed hydrothermal experiments at temperatures between 100°C and 300°C involving lipid-rich microbes and natural serpentinite mineral mixtures generated by the subaqueous hydrothermal alteration of ultramafic rock. The products reveal what the signals of life may look like when subjected to water–organic–inorganic reactions. Straight- and branched-chain lipids in unaltered samples are joined by cyclization and aromatization products in hydrothermally altered samples. Hydrothermal reactions produce distinct products that are not present in the starting materials, including small, single-ring, heteroatomic, and aromatic compounds such as indoles and phenols. Hydrothermal reactions in the presence of serpentinite minerals lead to significant reduction of these organic structures and their replacement by diketopiperazines (DKPs) and dihydropyrazines (DHPs), which may be compounds that are distinct to organic–inorganic reactions. Given that the precursors of DKPs and DHPs are normally lost during early diagenesis, the presence of these compounds can be an indicator of coexisting recent life and hydrothermal processing in the presence of minerals. However, laboratory experiments reveal that the formation and preservation of these compounds can only occur within a distinct temperature window. Our findings are relevant to life detection missions that aim to access hydrothermal and serpentinizing environments in the subsurfaces of icy moons and Mars. [ABSTRACT FROM AUTHOR]
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- 2023
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8. Star cluster formation from turbulent clumps – III. Across the mass spectrum.
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Farias, Juan P and Tan, Jonathan C
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STAR formation , *MASS spectrometry , *STELLAR populations , *EARLY stars , *STELLAR evolution , *STAR clusters - Abstract
We study the formation and early evolution of star clusters that have a wide range of masses and background cloud mass surface densities, Σcloud, which help set the initial sizes, densities, and velocity dispersions of the natal gas clumps. Initial clump masses of 300, 3000, and 30 000 M⊙ are considered, from which star clusters are born with an assumed 50 per cent overall star formation efficiency and with 50 per cent primordial binarity. This formation is gradual, i.e. with a range of star formation efficiencies per free-fall time from 1 to 100 per cent, so that the formation time can range from 0.7 Myr for low-mass, high-Σcloud clumps to ∼30 Myr for high-mass, low-Σcloud clumps. Within this framework of the turbulent clump model, for a given Σcloud, clumps of higher mass are of lower initial volume density, but their dynamical evolution leads to higher bound fractions and causes them to form much higher density cluster cores and maintain these densities for longer periods. This results in systematic differences in the evolution of binary properties, degrees of mass segregation, and rates of creation of dynamically ejected runaways. We discuss the implications of these results for observed star clusters and stellar populations. [ABSTRACT FROM AUTHOR]
- Published
- 2023
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9. GMC collisions as triggers of star formation – VIII. The core mass function.
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Hsu, Chia-Jung, Tan, Jonathan C, Christie, Duncan, Cheng, Yu, and O'Neill, Theo J
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STAR formation , *STELLAR collisions , *MAGNETIC flux density , *STAR clusters , *SUPERGIANT stars , *MOLECULAR clouds - Abstract
Compression in giant molecular cloud (GMC) collisions is a promising mechanism to trigger the formation of massive star clusters and OB associations. We simulate colliding and non-colliding magnetized GMCs and examine the properties of pre-stellar cores, selected from projected mass surface density maps, including after synthetic ALMA observations. We then examine core properties, including mass, size, density, velocity, velocity dispersion, temperature, and magnetic field strength. After 4 Myr, ∼1000 cores have formed in the GMC collision, and the high-mass end of the core mass function (CMF) can be fit by a power-law d N /dlog M ∝ M −α with α ≃ 0.7, i.e. relatively top heavy compared to a Salpeter mass function. Depending on how cores are identified, a break in the power law can appear around a few |$\times 10\, \mathrm{M}_\odot$|. The non-colliding GMCs form fewer cores with a CMF with α ≃ 0.8–1.2, i.e. closer to the Salpeter index. We compare the properties of these CMFs to those of several observed samples of cores. Considering other properties, cores formed from colliding clouds are typically warmer, have more disturbed internal kinematics, and are more likely to be gravitational unbound, than cores formed from non-colliding GMCs. The dynamical state of the protocluster of cores formed in the GMC–GMC collision is intrinsically subvirial but can appear to be supervirial if the total mass measurement is affected by observations that miss mass on large scales or at low densities. [ABSTRACT FROM AUTHOR]
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- 2023
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10. Organic geochemistry of in situ thermal-based analyses on Mars: the importance and influence of minerals.
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Sephton, Mark A., Tan, Jonathan S. W., Watson, Jonathan S., Hickman-Lewis, Keyron, and Madariaga, Juan M.
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MARS (Planet) , *SOLAR system , *MINERALS , *ASTROBIOLOGY , *ORGANIC geochemistry - Abstract
A high-priority goal for past, present and future missions to Mars is the search for evidence of past or present life. Some of the most information-rich signals are those represented by organic biomarkers. Thermal extraction has historically been the most popular in situ analysis technique employed on Mars owing to its elegance and ability to liberate both smallounds and large macromolecular networks. The geological record of Mars contains a variety of minerals, some of which can interact with organic matter when subjected to thermal extraction. We discuss the organic records that may be associated with these mineral hosts and the problems encountered when mineral–organic mixtures are analysed by thermal-based methods. We also suggest potential mitigations for future experiments of a similar nature and note that these mitigating steps can be applied not only in situ on Mars, but also after samples are returned to Earth as part of the Mars Sample Return mission, where more resources and time for sample preparation are available. Thematic collection: This article is part of the Astrobiology: Perspectives from the Geology of Earth and the Solar System collection available at: https://www.lyellcollection.org/topic/collections/astrobiology [ABSTRACT FROM AUTHOR]
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- 2023
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11. The SOFIA Massive (SOMA) Star Formation Survey. IV. Isolated Protostars.
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Fedriani, Rubén, Tan, Jonathan C., Telkamp, Zoie, Zhang, Yichen, Yang, Yao-Lun, Liu, Mengyao, De Buizer, James M., Law, Chi-Yan, Beltran, Maria T., Rosero, Viviana, Tanaka, Kei E. I., Cosentino, Giuliana, Gorai, Prasanta, Farias, Juan, Staff, Jan E., and Whitney, Barbara
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STAR formation , *SPECTRAL energy distribution , *PROTOSTARS , *SUPERGIANT stars , *RADIATIVE transfer , *MORPHOLOGY - Abstract
We present ∼10–40 μ m SOFIA-FORCAST images of 11 isolated protostars as part of the SOFIA Massive (SOMA) Star Formation Survey, with this morphological classification based on 37 μ m imaging. We develop an automated method to define source aperture size using the gradient of its background-subtracted enclosed flux and apply this to build spectral energy distributions (SEDs). We fit the SEDs with radiative transfer models, developed within the framework of turbulent core accretion (TCA) theory, to estimate key protostellar properties. Here, we release the sedcreator python package that carries out these methods. The SEDs are generally well fitted by the TCA models, from which we infer initial core masses M c ranging from 20–430 M ⊙, clump mass surface densities Σcl ∼ 0.3–1.7 g cm−2, and current protostellar masses m * ∼ 3–50 M ⊙. From a uniform analysis of the 40 sources in the full SOMA survey to date, we find that massive protostars form across a wide range of clump mass surface density environments, placing constraints on theories that predict a minimum threshold Σcl for massive star formation. However, the upper end of the m *−Σcl distribution follows trends predicted by models of internal protostellar feedback that find greater star formation efficiency in higher Σcl conditions. We also investigate protostellar far-IR variability by comparison with IRAS data, finding no significant variation over an ∼40 yr baseline. [ABSTRACT FROM AUTHOR]
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- 2023
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12. Inside-out planet formation – VII. Astrochemical models of protoplanetary discs and implications for planetary compositions.
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Cevallos Soto, Arturo, Tan, Jonathan C, Hu, Xiao, Hsu, Chia-Jung, and Walsh, Catherine
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ORIGIN of planets , *PLANETARY interiors , *PLANETARY atmospheres , *PROTOPLANETARY disks , *ACCRETION disks , *PEBBLE bed reactors , *CHEMICAL models - Abstract
Inside-out planet formation (IOPF) proposes that the abundant systems of close-in Super-Earths and Mini-Neptunes form in situ at the pressure maximum associated with the dead zone inner boundary (DZIB). We present a model of physical and chemical evolution of protoplanetary disc midplanes that follows gas advection, radial drift of pebbles, and gas-grain chemistry to predict abundances from ∼300 au down to the DZIB near 0.2 au. We consider typical disc properties relevant for IOPF, i.e. accretion rates |$10^{-9}\lt \dot{m}/ (\mathrm{ M}_\odot \:{\rm {yr}}^{-1})\lt 10^{-8}$| and viscosity parameter α = 10−4, and evolve for fiducial duration of 105 yr. For outer, cool disc regions, we find that C and up to |$90{{\ \rm per\ cent}}$| of O nuclei start locked in CO and |$\rm O_2$| ice, which keeps abundances of |$\rm CO_2$| and |$\rm H_2O$| one order of magnitude lower. Radial drift of icy pebbles is influential, with gas-phase abundances of volatiles enhanced up to two orders of magnitude at icelines, while the outer disc becomes depleted of dust. Discs with decreasing accretion rates gradually cool, which draws in icelines closer to the star. At ≲ 1 au, advective models yield water-rich gas with C/O ratios ≲ 0.1, which may be inherited by atmospheres of planets forming here via IOPF. For planetary interiors built by pebble accretion, IOPF predicts volatile-poor compositions. However, advectively enhanced volatile mass fractions of |$\sim 10{{\ \rm per\ cent}}$| can occur at the water iceline. [ABSTRACT FROM AUTHOR]
- Published
- 2022
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13. Poor Sleep Quality Predicts Decline in Physical Health Functioning in Patients with Coronary Heart Disease and Moderating Role of Social Support.
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Shen, Biing-Jiun, Tan, Jonathan Jun Liang, Xu, Yue, and Tay, Hung Yong
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SOCIAL support , *PSYCHOLOGY of cardiac patients , *CORONARY disease , *REGRESSION analysis , *PHYSICAL activity , *SLEEP deprivation , *QUALITY of life , *QUESTIONNAIRES - Abstract
Although sleep problems are common among patients with coronary heart disease (CHD), there is a lack of prospective research examining its influence on health consequences over time. This study investigated whether poor sleep quality predicted patients' decline in physical health functioning over 6 months and whether social support buffered its detrimental effect. Participants were 185 patients with CHD, who completed measures of sleep, psychosocial characteristics, and physical health functioning at baseline and 6 months. Hierarchical regression analyses were conducted to examine whether global sleep index and its subscales, including sleep efficiency, perceived sleep quality, and daily disturbances (sleep disturbances and daytime dysfunction), predicted the decline of physical health functioning at 6 months. Social support was examined for its moderating effect in buffering the negative influence of poor sleep quality on physical health functioning over 6 months. Findings showed that poorer global sleep index, especially subscales of daily disturbances and lower sleep efficiency, significantly predicted greater decline of physical health functioning at 6 months, even after adjusting for covariates, including baseline functioning and depression. Moreover, social support was found to buffer the detrimental impact of poor sleep quality, especially low sleep efficiency, on 6-month physical health functioning. Findings suggest that improving sleep quality for patients with CHD may be promising to facilitate their long-term health maintenance. [ABSTRACT FROM AUTHOR]
- Published
- 2022
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14. Factors associated with family decision-making after pediatric out-of-hospital cardiac arrest.
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Frelinger, Jessica M., Tan, Jonathan M., Klein, Margaret J., Newth, Christopher J.L., Ross, Patrick A., and Winter, Meredith C.
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• Decision-making practices after pediatric out-of-hospital cardiac arrest (OHCA) • Social determinants of health not associated with decision-making after OHCA. • Neurological morbidity associated with family decision-making after OHCA. • Palliative care is critical for family decision-making after OHCA. This study aims to identify demographic factors, area-based social determinants of health (SDOH), and clinical features associated with medical decision-making after pediatric out-of-hospital cardiac arrest (OHCA). This is a retrospective, exploratory, descriptive analysis of patients < 18 years old admitted to the pediatric intensive care unit (ICU) after OHCA from 2011 to 2022 (n = 217) at an urban tertiary care, free-standing children's hospital. Outcomes of interest included: (1) whether a new advance care plan (ACP) (defined as a written advance directive including do not resuscitate and/or do not intubate) was ordered during hospitalization, and (2) whether the patient was discharged with new medical technology (defined as tracheostomy and/or feeding tube). Logistic regression models identified features associated with these outcomes. Of the 217 patients, 78 patients (36%) had a new ACP placed during their admission. Of the survivors, 26% (27/102) were discharged home with new medical technology. Factors associated with ACP were greater change in Pediatric Cerebral Performance Category (PCPC) score (aOR = 1.49, 95% CI [1.28–1.73], p-value < 0.001) and palliative care consultation (aOR = 2.39, 95% CI [1.16–4.89], p-value 0.018). Factors associated with new medical technology were lower change in PCPC score (aOR = 0.76, 95% C.I. [0.61–0.95], p-value = 0.015) and palliative care consultation (aOR = 7.07, 95% CI [3.01–16.60], p-value < 0.001). There were no associations between area-based SDOH and outcomes. Understanding factors associated with decision-making related to ACP after OHCA is critical to optimize counseling for families. Multi-institutional studies are warranted to identify whether these findings are generalizable. [ABSTRACT FROM AUTHOR]
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- 2024
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15. Resistive small bowel bleeding secondary to an arteriovenous malformation.
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Othman, Bushra, Tan, Jonathan Y. C., Friedman, Antony, and Steel, Malcolm
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ARTERIOVENOUS malformation , *SMALL intestine , *HEMORRHAGE - Published
- 2023
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16. Inside–out planet formation: VI. oligarchic coagulation of planetesimals from a pebble ring?
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Cai, Maxwell X, Tan, Jonathan C, and Portegies Zwart, Simon
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PLANETESIMALS , *ORIGIN of planets , *PEBBLES , *INNER planets , *COAGULATION , *PROTOPLANETARY disks - Abstract
Inside–Out Planet Formation (IOPF) is a theory addressing the origin of Systems of Tightly-Packed Inner Planets (STIPs) via in situ formation and growth of the planets. It predicts that a pebble ring is established at the pressure maximum associated with the dead zone inner boundary (DZIB) with an inner disc magnetorotational instability (MRI)-active region. Using direct N -body simulations, we study the collisional evolution of planetesimals formed from such a pebble ring, in particular, examining whether a single dominant planet emerges. We consider a variety of models, including some in which the planetesimals are continuing to grow via pebble accretion. We find that the planetesimal ring undergoes oligarchic evolution, and typically turns into 2 or 3 surviving oligarchs on nearly coplanar and circular orbits, independent of the explored initial conditions or form of pebble accretion. The most massive oligarchs typically consist of about |$70{{\ \rm per\ cent}}$| of the total mass, with the building-up process typically finishing within ∼105 yr. However, a relatively massive secondary planet always remains with |$\sim 30\!-\!65{{\ \rm per\ cent}}$| of the mass of the primary. Such secondary planets have properties that are inconsistent with the observed properties of the innermost pairs of planets in STIPs. Thus, for IOPF to be a viable theory for STIP formation, it needs to be shown how oligarchic growth of a relatively massive secondary from the initial pebble ring can be avoided. We discuss some potential additional physical processes that should be included in the modelling and explored as next steps. [ABSTRACT FROM AUTHOR]
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- 2022
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17. Star Formation in a Strongly Magnetized Cloud.
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Cheng, Yu, Tan, Jonathan C., Caselli, Paola, Fissel, Laura, Arce, Héctor G., Fontani, Francesco, Goodson, Matthew D., Liu, Mengyao, and Galitzki, Nicholas
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STAR formation , *MOLECULAR clouds , *BIPOLAR outflows (Astrophysics) , *DUST measurement , *DEUTERATION , *MAGNETIC fields , *PROTOSTARS - Abstract
We study star formation in the Center Ridge 1 (CR1) clump in the Vela C giant molecular cloud, selected as a high column density region that shows the lowest level of dust continuum polarization-angle dispersion, likely indicating that the magnetic field is relatively strong. We observe the source with the Atacama Large Millimeter/submillimeter Array 7 m array at 1.05 and 1.3 mm wavelengths, which enable measurements of dust temperature, core mass, and astrochemical deuteration. A relatively modest number of 11 dense cores are identified via their dust continuum emission, with masses spanning from 0.17–6.7. Overall CR1 has a relatively low compact dense gas fraction compared with other typical clouds with similar column densities, which may be a result of the strong magnetic field and/or the very early evolutionary stage of this region. The deuteration ratios, , of the cores, measured with (3-2) and (3-2) lines, span from 0.011–0.85, with the latter being one of the highest values yet detected. The level of deuteration appears to decrease with evolution from prestellar to protostellar phase. A linear filament, running approximately parallel with the large scale magnetic field orientation, is seen connecting the two most massive cores, each having CO bipolar outflows aligned orthogonally to the filament. The filament contains the most deuterated core, likely to be prestellar and located midway between the protostars. The observations permit measurement of the full deuteration structure of the filament along its length, which we present. We also discuss the kinematics and dynamics of this structure, as well as of the dense core population. [ABSTRACT FROM AUTHOR]
- Published
- 2021
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18. Applications of food waste-derived black soldier fly larval frass as incorporated compost, side-dress fertilizer and frass-tea drench for soilless cultivation of leafy vegetables in biochar-based growing media.
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Tan, Jonathan Koon Ngee, Lee, Jonathan Tian En, Chiam, Zhongyu, Song, Shuang, Arora, Srishti, Tong, Yen Wah, and Tan, Hugh Tiang Wah
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EDIBLE greens , *VEGETABLE farming , *BOK choy , *ORGANIC waste recycling , *LIQUID fertilizers , *SOIL amendments , *LETTUCE , *FERTILIZERS - Abstract
• Food waste-derived black soldier fly larval frass and waste-wood biochar could substitute for peat compost and soil. • Sidedress application of frass yielded results comparable to those of the liquid inorganic fertilizer control. • The direct application of frass was more effective in promoting plant growth than frass tea application. • Frass and frass tea applications were free of heavy metals and foodborne pathogens. Black soldier fly (BSF) larval bioconversion can recycle nutrients in organic wastes into larval biomass and frass. While the frass has been commonly marketed as a soil amendment, its usefulness in soilless cultivation remains largely unexplored. Growth experiments were conducted to investigate the effectiveness of surplus food-derived and okara-derived BSF larval frass as an incorporated compost, side-dress fertilizer and frass-tea drench for the cultivation of pak choi and lettuce in waste-wood derived biochar growing media. Pak choi yields from treatments with surplus food-derived frass and biochar at a 10:90 (v/v) ratio and inorganic fertilizer were comparable to those of the control which consisted of soil, peat-based compost and inorganic fertilizer. However, yields decreased with increasing frass incorporation rates owing to high salinity and potentially low oxygen conditions in the growing media. When used as a fertilizer on biochar-coir growing media, the direct application of frass as a side-dress fertilizer was 1.6–6.8 times more effective in promoting lettuce growth than the application as a frass-tea drench. Frass fertilizers derived from surplus food outperformed those derived from okara by 1.3–5.3 times. Lettuce yields were not significantly different between the treatment with surplus food-derived frass applied as a side-dress fertilizer and the control of liquid inorganic fertilizer. Variations in fertilizing potential were attributed to nutrient availability and the presence of plant growth promoting microbes in the growing media. BSF larval frass derived from food waste shows promise in partially replacing unsustainable agricultural inputs for leafy vegetable cultivation, including soil and inorganic fertilizers. [ABSTRACT FROM AUTHOR]
- Published
- 2021
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19. A simulation optimization model for portfolio selection problem with quadratic programming technique.
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Tan, Jonathan Huan Jing, Kek, Sie Long, Ibrahim, Siti Nur Iqmal, Ibrahim, Noor Akma, Ismail, Fudziah, Lee, Lai Soon, Leong, Wah June, Midi, Habshah, and Wahi, Nadihah
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RATE of return , *INVESTMENTS , *FINANCIAL management , *STOCK exchanges , *EXPECTED returns - Abstract
Portfolio investment is one of the important topics in financial management. Its aim of having the wealth in a period of time with maximum return and minimum risk has been well-defined in the literature. Specifically, the portfolio selection is arisen to be an interesting investment issue. Since the risk is defined as the probability of losses relative to the expected return in the portfolio investment, the existing risk would influence the rate of return and affect the investment decision. In this paper, the portfolio selection problem is discussed. The aim is to provide an effective quantitative study in managing the portfolio. In the beginning, the rates of return are calculated and it is followed by computing the expected rates of return and the related covariance matrix. Accordingly, the mean-variance optimization model, which is the quadratic programming model, is formulated and solved by the quadratic programming technique. Here, the objective function to be minimized represents the risk of the portfolio selection, while the weights of the portfolio selection, which are defined as the decision variables, are normalized with the total amount of investment, and the expected return is assigned to a certain targeted return. For illustration, a set of historical data on the stock prices in the Financial Times Stock Exchange (FTSE) Bursa Malaysia Kuala Lumpur Composite Index (KLCI) is considered. Through simulation and optimization of the mean-variance portfolio model, the result shows the relationship between risk and return with the various targeted returns. Moreover, by applying the Sharpe ratio, the optimal weight of the portfolio selection, which is the optimal portfolio decision, is properly suggested. In conclusion, the simulation optimization model for the portfolio selection problem is highly recommended. [ABSTRACT FROM AUTHOR]
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- 2020
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20. Pyrolysis of Carboxylic Acids in the Presence of Iron Oxides: Implications for Life Detection on Missions to Mars.
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Royle, Samuel H., Tan, Jonathan S.W., Watson, Jonathan S., and Sephton, Mark A.
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FERRIC oxide , *CARBOXYLIC acids , *IRON oxides , *CARBOXYLIC acids analysis , *GOETHITE , *LIFE on Mars , *MARTIAN surface , *AROMATIZATION - Abstract
The search for, and characterization of, organic matter on Mars is central to efforts in identifying habitable environments and detecting evidence of life in the martian surface and near surface. Iron oxides are ubiquitous in the martian regolith and are known to be associated with the deposition and preservation of organic matter in certain terrestrial environments, thus iron oxide-rich sediments are potential targets for life-detection missions. The most frequently used protocol for martian organic matter characterization (also planned for use on ExoMars) has been thermal extraction for the transfer of organic matter to gas chromatography-mass spectrometry (GC-MS) detectors. For the effective use of thermal extraction for martian samples, it is necessary to explore how potential biomarker organic molecules evolve during this process in the presence of iron oxides. We have thermally decomposed iron oxides simultaneously with (z)-octadec-9-enoic and n-octadecanoic acids and analyzed the products through pyrolysis-GC-MS. We found that the thermally driven dehydration, reduction, and recrystallization of iron oxides transformed fatty acids. Overall detectability of products greatly reduced, molecular diversity decreased, unsaturated products decreased, and aromatization increased. The severity of this effect increased as reduction potential of the iron oxide and inferred free radical formation increased. Of the iron oxides tested hematite showed the least transformative effects, followed by magnetite, goethite, then ferrihydrite. It was possible to identify the saturation state of the parent carboxylic acid at high (0.5 wt %) concentrations by the distribution of n-alkylbenzenes in the pyrolysis products. When selecting life-detection targets on Mars, localities where hematite is the dominant iron oxide could be targeted preferentially, otherwise thermal analysis of carboxylic acids, or similar biomarker molecules, will lead to enhanced polymerization, aromatization, and breakdown, which will in turn reduce the fidelity of the original biomarker, similar to changes normally observed during thermal maturation. [ABSTRACT FROM AUTHOR]
- Published
- 2021
- Full Text
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21. Quantifying Preservation Potential: Lipid Degradation in a Mars-Analog Circumneutral Iron Deposit.
- Author
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Tan, Jonathan S.W. and Sephton, Mark A.
- Subjects
- *
IRON ores , *GALE Crater (Mars) , *HYDROXIDE minerals , *EXTRACTION techniques , *FERRIC hydroxides , *IRON alloys - Abstract
Comparisons between the preservation potential of Mars-analog environments have historically been qualitative rather than quantitative. Recently, however, laboratory-based artificial maturation combined with kinetic modeling techniques have emerged as a potential means by which the preservation potential of solvent-soluble organic matter can be quantified in various Mars-analog environments. These methods consider how elevated temperatures, pressures, and organic–inorganic interactions influence the degradation of organic biomarkers post-burial. We used these techniques to investigate the preservation potential of deposits from a circumneutral iron-rich groundwater system. These deposits are composed of ferrihydrite (Fe5HO8 · 4H2O), an amorphous iron hydroxide mineral that is a common constituent of rocks found in ancient lacustrine environments on Mars, such as those observed in Gale Crater. Both natural and synthetic ferrihydrite samples were subjected to hydrous pyrolysis to observe the effects of long-term burial on the mineralogy and organic content of the samples. Our experiments revealed that organic–inorganic interactions in the samples are dominated by the transformation of iron minerals. As amorphous ferrihydrite transforms into more crystalline species, the decrease in surface area results in the desorption of organic matter, potentially rendering them more susceptible to degradation. We also find that circumneutral iron-rich deposits provide unfavorable conditions for the preservation of solvent-soluble organic matter. Quantitative comparisons between preservation potentials as calculated when using kinetic parameters show that circumneutral iron-rich deposits are ∼25 times less likely to preserve solvent-soluble organic matter compared with acidic, iron-rich environments. Our results suggest that circumneutral iron-rich deposits should be deprioritized in favor of acidic iron- and sulfur-rich deposits when searching for evidence of life with solvent extraction techniques. [ABSTRACT FROM AUTHOR]
- Published
- 2021
- Full Text
- View/download PDF
22. Photodissociation region diagnostics across galactic environments.
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Bisbas, Thomas G, Tan, Jonathan C, and Tanaka, Kei E I
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- *
SPECTRAL energy distribution , *PHOTODISSOCIATION , *GALACTIC halos , *COSMIC rays , *INTERSTELLAR medium , *MOLECULAR clouds , *ENERGY density - Abstract
We present three-dimensional astrochemical simulations and synthetic observations of magnetized, turbulent, self-gravitating molecular clouds. We explore various galactic interstellar medium environments, including cosmic ray ionization rates in the range of ζ CR = 10−17– |$10^{-14}\, {\rm s}^{-1}$| , far-UV intensities in the range of G 0 = 1–103 and metallicities in the range of Z = 0.1– |$2\, {\rm Z}_{\odot }$|. The simulations also probe a range of densities and levels of turbulence, including cases where the gas has undergone recent compression due to cloud–cloud collisions. We examine: (i) the column densities of carbon species across the cycle of C ii , C i , and CO, along with O i , in relation to the H i -to-H2 transition; (ii) the velocity-integrated emission of [C ii ] 158 μm, [13C ii ] 158 μm, [C i ] 609 μm and 370 μm, [O i ] 63 μm and 146 μm, and of the first ten 12CO rotational transitions; (iii) the corresponding Spectral Line Energy Distributions; (iv) the usage of [C ii ] and [O i ] 63 μm to describe the dynamical state of the clouds; (v) the behaviour of the most commonly used ratios between transitions of CO and [C i ]; and (vi) the conversion factors for using CO and C i as H2-gas tracers. We find that enhanced cosmic ray energy densities enhance all aforementioned line intensities. At low metallicities, the emission of [C ii ] is well connected with the H2 column, making it a promising new H2 tracer in metal-poor environments. The conversion factors of X CO and X C i depend on metallicity and the cosmic ray ionization rate, but not on FUV intensity. In the era of ALMA, SOFIA, and the forthcoming CCAT-prime telescope, our results can be used to understand better the behaviour of systems in a wide range of galactic and extragalactic environments. [ABSTRACT FROM AUTHOR]
- Published
- 2021
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- View/download PDF
23. Deuterium chemodynamics of massive pre-stellar cores.
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Hsu, Chia-Jung, Tan, Jonathan C, Goodson, Matthew D, Caselli, Paola, Körtgen, Bastian, and Cheng, Yu
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- *
HEAVY elements , *DEUTERATION , *DEUTERIUM , *COSMIC rays , *MAGNETOHYDRODYNAMICS , *PRODUCTION sharing contracts (Oil & gas) , *GRAVITY - Abstract
High levels of deuterium fractionation of N2H+ (i.e. |$\mathrm{D^{{\mathrm{N_2H^+}}}_{\text{frac}}}$| ≳ 0.1) are often observed in pre-stellar cores (PSCs) and detection of N2D+ is a promising method to identify elusive massive PSCs. However, the physical and chemical conditions required to reach such high levels of deuteration are still uncertain, as is the diagnostic utility of N2H+ and N2D+ observations of PSCs. We perform 3D magnetohydrodynamics simulations of a massive, turbulent, magnetized PSC, coupled with a sophisticated deuteration astrochemical network. Although the core has some magnetic/turbulent support, it collapses under gravity in about one free-fall time, which marks the end of the simulations. Our fiducial model achieves relatively low |$\mathrm{D^{{\mathrm{N_2H^+}}}_{\text{frac}}}$| ∼0.002 during this time. We then investigate effects of initial ortho-para ratio of H2 (|$\mathrm{OPR^{H_2}}$|), temperature, cosmic ray (CR) ionization rate, CO and N-species depletion factors, and prior PSC chemical evolution. We find that high CR ionization rates and high depletion factors allow the simulated |$\mathrm{D^{{\mathrm{N_2H^+}}}_{\text{frac}}}$| and absolute abundances to match observational values within one free-fall time. For |$\mathrm{OPR^{H_2}}$| , while a lower initial value helps the growth of |$\mathrm{D^{{\mathrm{N_2H^+}}}_{\text{frac}}}$| , the spatial structure of deuteration is too widespread compared to observed systems. For an example model with elevated CR ionization rates and significant heavy element depletion, we then study the kinematic and dynamic properties of the core as traced by its N2D+ emission. The core, undergoing quite rapid collapse, exhibits disturbed kinematics in its average velocity map. Still, because of magnetic support, the core often appears kinematically subvirial based on its N2D+ velocity dispersion. [ABSTRACT FROM AUTHOR]
- Published
- 2021
- Full Text
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24. Artificial Maturation of Iron- and Sulfur-Rich Mars Analogues: Implications for the Diagenetic Stability of Biopolymers and Their Detection with Pyrolysis–Gas Chromatography–Mass Spectrometry.
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Tan, Jonathan S.W., Royle, Samuel H., and Sephton, Mark A.
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- *
MARTIAN surface , *MARS (Planet) , *LIFE on Mars , *BIOPOLYMERS , *GEOLOGICAL carbon sequestration - Abstract
Acidic iron- and sulfur-rich streams are appropriate analogues for the late Noachian and early Hesperian periods of martian history, when Mars exhibited extensive habitable environments. Any past life on Mars may have left behind diagnostic evidence of life that could be detected at the present day. For effective preservation, these remains must have avoided the harsh radiation flux at the martian surface, survived geological storage for billions of years, and remained detectable within their geochemical environment by analytical instrument suites used on Mars today, such as thermal extraction techniques. We investigated the detectability of organic matter within sulfur stream sediments that had been subjected to artificial maturation by hydrous pyrolysis. After maturation, the samples were analyzed by pyrolysis–gas chromatography–mass spectrometry (py-GC-MS) to determine whether organic matter could be detected with this commonly used technique. We find that macromolecular organic matter can survive the artificial maturation process in the presence of iron- and sulfur-rich minerals but cannot be unambiguously distinguished from abiotic organic matter. However, if jarosite and goethite are present in the sulfur stream environment, they interfere with the py-GC-MS detection of organic compounds in these samples. Clay reduces the obfuscating effect of the oxidizing minerals by providing nondeleterious adsorption sites. We also find that after a simple alkali and acid leaching process that removes oxidizing minerals such as iron sulfates, oxides, and oxyhydroxides, the sulfur stream samples exhibit much greater organic responses during py-GC-MS in terms of both abundance and diversity of organic compounds, such as the detection of hopanes in all leached samples. Our results suggest that insoluble organic matter can be preserved over billions of years of geological storage while still retaining diagnostic organic information, but sample selection strategies must either avoid jarosite- and goethite-rich outcrops or conduct preparative chemistry steps to remove these oxidants prior to analysis by thermal extraction techniques. [ABSTRACT FROM AUTHOR]
- Published
- 2021
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25. Pancreatic pseudocyst: Dilemma of its recent management (Review).
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TAN, JONATHAN HARTANTO, WENJIE CHIN, SHAIKH, ABDUL LATEEF, and SHUSEN ZHENG
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- *
PANCREATIC cysts , *ENDOSCOPIC ultrasonography , *SURGICAL drainage , *DIAGNOSIS , *DILEMMA , *GASTROENTEROLOGISTS , *CATHETERS - Abstract
Advances in radiological techniques have led to an increase in the number of diagnoses of pancreatic pseudocyst, which is the most common pancreatic cyst lesion disease, accounting for two-thirds of all pancreatic cyst lesions. Historically, the management of pancreatic pseudocyst has been achieved through the use of conservative treatments and surgery; however, due to the complications and recurrence rate associated with these techniques, the management of pancreatic pseudocyst is challenging. Surgeons and gastroenterologists have attempted to determine the optimal management technique to treat pancreatic pseudocyst to reduce complications and the recurrence rate. From these investigations, percutaneous catheter, surgical and endoscopic drainage with ultrasonography guidance have become promising management techniques. The present review aimed to summarize the diagnostic and therapeutic methods used for the management of pancreatic pseudocyst and to compare percutaneous catheter, surgical and endoscopic drainage. [ABSTRACT FROM AUTHOR]
- Published
- 2021
- Full Text
- View/download PDF
26. Measurement Structure of the Pittsburgh Sleep Quality Index and Its Association with Health Functioning in Patients with Coronary Heart Disease.
- Author
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Tan, Jonathan Jun Liang, Tay, Hung Yong, Lim, Cindy Khim Siang, and Shen, Biing-Jiun
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- *
CORONARY disease , *CARDIAC patients , *CONFIRMATORY factor analysis , *STRUCTURAL equation modeling , *SOMNOLOGY - Abstract
Research on the underlying structure of sleep measures in patients with coronary heart disease (CHD) is lacking. Existing research on sleep and health outcomes primarily focused on only one dimension of sleep (e.g., sleep duration), leaving other aspects unexamined. To address this gap, this study examined the measurement structure of Pittsburgh Sleep Quality Index (PSQI) and its associations with health-related quality of life among CHD patients. Participants were 167 CHD patients from a cardiac wellness program. Confirmatory factor analysis revealed that the two-factor structure with sleep efficiency and perceived sleep quality best fitted the data. Concurrent validity analyses with structural equation modeling showed that, when considered simultaneously, perceived sleep quality, but not sleep efficiency, was significantly associated with emotional, physical, and social quality of life. Findings demonstrated that the PSQI consists of two moderately correlated factors that are differentially associated with separate health domains in cardiac patients. [ABSTRACT FROM AUTHOR]
- Published
- 2020
- Full Text
- View/download PDF
27. The SOFIA Massive (SOMA) Star Formation Survey. III. From Intermediate- to High-mass Protostars.
- Author
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Liu, Mengyao, Tan, Jonathan C., De Buizer, James M., Zhang, Yichen, Moser, Emily, Beltrán, Maria T., Jan E. Staff, Tanaka, Kei E. I., Whitney, Barbara, Rosero, Viviana, Yang, Yao-Lun, and Fedriani, Rubén
- Subjects
- *
PROTOSTARS , *STAR formation , *SPECTRAL energy distribution , *RADIATIVE transfer , *RADIATION , *SUPERGIANT stars - Abstract
We present SOFIA–FORCAST images of 14 intermediate-mass protostar candidates as part of the SOFIA Massive (SOMA) Star Formation Survey. We build spectral energy distributions, also using archival Spitzer, Herschel, and IRAS data. We then fit the spectral energy distributions with radiative transfer models of Zhang & Tan, based on turbulent core accretion theory, to estimate key protostellar properties. With the addition of these intermediate-mass sources, based on average properties derived from SED fitting, SOMA protostars span luminosities from , current protostellar masses from , and ambient clump mass surface densities, , from. A wide range of evolutionary states of the individual protostars and of the protocluster environments is also probed. We have also considered about 50 protostars identified in infrared dark clouds that are expected to be at the earliest stages of their evolution. With this global sample, most of the evolutionary stages of high- and intermediate-mass protostars are probed. The best-fitting models show no evidence that a threshold value of the protocluster clump mass surface density is required to form protostars up to. However, to form more massive protostars, there is tentative evidence that needs to be. We discuss how this is consistent with expectations from core accretion models that include internal feedback from the forming massive star. [ABSTRACT FROM AUTHOR]
- Published
- 2020
- Full Text
- View/download PDF
28. Hunting for Runaways from the Orion Nebula Cluster.
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Farias, Juan P., Tan, Jonathan C., and Eyer, Laurent
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ORION Nebula , *STELLAR parallax , *CORONAL mass ejections , *STELLAR activity - Abstract
We use Gaia DR2 to hunt for runaway stars from the Orion Nebula Cluster (ONC). We search a region extending 45° around the ONC and out to 1 kpc to find sources that have overlapped in angular position with the cluster in the last ∼10 Myr. We find ∼17,000 runaway/walkaway candidates that satisfy this 2D traceback condition. Most of these are expected to be contaminants, e.g., caused by Galactic streaming motions of stars at different distances. We thus examine six further tests to help identify real runaways, namely: (1) possessing young stellar object (YSO) colors and magnitudes based on Gaia optical photometry; (2) having IR excess consistent with YSOs based on 2MASS and Wide-field Infrared Survey Explorer photometry; (3) having a high degree of optical variability; (4) having closest approach distances well-constrained to within the cluster half-mass radius; (5) having ejection directions that avoid the main Galactic streaming contamination zone; and (6) having a required radial velocity (RV) for 3D overlap of reasonable magnitude (or, for the 7% of candidates with measured RVs, satisfying 3D traceback). Thirteen sources, not previously noted as Orion members, pass all these tests, while another twelve are similarly promising, except they are in the main Galactic streaming contamination zone. Among these 25 ejection candidates, ten with measured RVs pass the most restrictive 3D traceback condition. We present full lists of runaway/walkaway candidates, estimate the high-velocity population ejected from the ONC, and discuss its implications for cluster formation theories via comparison with numerical simulations. [ABSTRACT FROM AUTHOR]
- Published
- 2020
- Full Text
- View/download PDF
29. Why should majority voting be unfair?
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Breitmoser, Yves and Tan, Jonathan H.W.
- Subjects
- *
PLURALITY voting , *GROUP decision making , *EXPERIMENTAL design - Abstract
The common use of majority rule in group decision making is puzzling. In theory, it inequitably favors the proposer, and paradoxically, it disadvantages voters further if they are inequity averse. In practice, however, outcomes are equitable. The present paper analyzes data from a novel experimental design to identify the underlying social preferences. Our experiment compares one-shot and indefinite horizon versions of random-proposer majority bargaining (the Baron-Ferejohn game) which allow us to disentangle behaviors compatible with altruism, inequity aversion, and reference dependent altruism. Most subjects are classified as reference-dependent altruists, around 10% are inequity averse. Subjects are egoistic when their payoff is below their reference point, they become efficiency concerned when satisfied, and the reference point is either the ex ante expectation or the opponent's payoff. Finally, we successfully test RDA out-of-sample on a number of distribution and bargaining games from three seminal social preference experiments. [ABSTRACT FROM AUTHOR]
- Published
- 2020
- Full Text
- View/download PDF
30. Gas Kinematics of the Massive Protocluster G286.21+0.17 Revealed by ALMA.
- Author
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Cheng, Yu, Tan, Jonathan C., Liu, Mengyao, Lim, Wanggi, and Andersen, Morten
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- *
KINEMATICS , *GAS dynamics , *SPECTRAL lines , *GASES , *VELOCITY - Abstract
We study the gas kinematics and dynamics of the massive protocluster G286.21+0.17 with the Atacama Large Millimeter/submillimeter Array using spectral lines of C18O(2–1), (3–2), (3–2), and (3–2). On the parsec clump scale, C18O emission appears highly filamentary around the systemic velocity, and are more closely associated with the dust continuum, and is strongly concentrated toward the protocluster center, where no or only weak detection is seen for and , possibly due to this region being at a relatively evolved evolutionary stage. Spectra of 76 continuum-defined dense cores, typically a few 1000 au in size, are analyzed to measure their centroid velocities and internal velocity dispersions. There are no statistically significant velocity offsets of the cores among the different dense gas tracers. Furthermore, the majority (71%) of the dense cores have subthermal velocity offsets with respect to their surrounding, lower-density C18O-emitting gas. Within the uncertainties, the dense cores in G286 show internal kinematics that are consistent with being in virial equilibrium. On clump scales, the core-to-core velocity dispersion is also similar to that required for virial equilibrium in the protocluster potential. However, the distribution in velocity of the cores is largely composed of two spatially distinct groups, which indicates that the dense molecular gas has not yet relaxed to virial equilibrium, perhaps due to there being recent/continuous infall into the system. [ABSTRACT FROM AUTHOR]
- Published
- 2020
- Full Text
- View/download PDF
31. Organic Records of Early Life on Mars: The Role of Iron, Burial, and Kinetics on Preservation.
- Author
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Tan, Jonathan and Sephton, Mark A.
- Subjects
- *
LIFE on Mars , *MARTIAN surface , *RIVER sediments , *MICROORGANISM populations , *ORGANIC geochemistry , *IRON alloys - Abstract
Samples that are likely to contain evidence of past life on Mars must have been deposited when and where environments exhibited habitable conditions. Mars analog sites provide the opportunity to study how life could have exploited such habitable conditions. Acidic iron- and sulfur-rich streams are good geochemical analogues for the late Noachian and early Hesperian, periods of martian history where habitable conditions were widespread. Past life on Mars would have left behind fossilized microbial organic remains. These are often-sought diagnostic evidence, but they must be shielded from the harsh radiation flux at the martian surface and its deleterious effect on organic matter. One mechanism that promotes such preservation is burial, which raises questions about how organic biomarkers are influenced by the postburial effects of diagenesis. We investigated the kinetics of organic degradation in the subsurface of Mars. Natural mixtures of acidic iron- and sulfur-rich stream sediments and their associated microbial populations and remains were subjected to hydrous pyrolysis, which simulated the increased temperatures and pressures of burial alongside any promoted organic/mineral interactions. Calculations were made to extrapolate the observed changes over martian history. Our experiments indicate that low carbon contents, high water-to-rock ratios, and the presence of iron-rich minerals combine to provide unfavorable conditions for the preservation of soluble organic matter over the billions of years necessary to produce present-day organic records of late Noachian and early Hesperian life on Mars. Successful sample selection strategies must therefore consider the pre-, syn-, and postburial histories of sedimentary records on Mars and the balance between the production of biomass and the long-term preservation of organic biomarkers over geological time. [ABSTRACT FROM AUTHOR]
- Published
- 2020
- Full Text
- View/download PDF
32. Surgical neonates: A retrospective review of procedures and postoperative outcomes at a quaternary children's hospital.
- Author
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Nelson, Olivia, Rintoul, Natalie E., Tan, Jonathan M., Simpao, Allan F., Chuo, John, Hedrick, Holly L., Duran, Melissa S., Makeneni, Spandana, Devine, Matthew, Cao, Lusha, and Stricker, Paul A.
- Subjects
- *
PREMATURE infants , *CHILDREN'S hospitals , *TREATMENT effectiveness , *NEWBORN infants , *SURGICAL site infections , *SURGICAL indications , *ARACHNOID cysts , *DEEP brain stimulation - Abstract
Introduction: Neonates have a high incidence of respiratory and cardiac perioperative events. Disease severity and indications for surgical intervention often dovetail with an overall complex clinical course and predispose these infants to adverse long‐term neurodevelopmental outcomes and increased length of stay. Our aims were to describe severe and nonsevere early postoperative complications to establish a baseline of care outcomes and to identify subgroups of surgical neonates and procedures for future prospective studies. Methods: Electronic health record data were examined retrospectively for a cohort of patients who had general anesthesia from January 26, 2015 to August 31, 2018. Inclusion criteria were full‐term infants with postmenstrual age less than 44 weeks or premature infants less than 60 weeks postmenstrual age undergoing nonimaging, noncardiac surgery. Severe postoperative complications were defined as mortality, reintubation, positive blood culture, and surgical site infection. Nonsevere early postoperative outcomes were defined as hypoglycemia, hyperglycemia, hypothermia, hyperthermia, and readmission within 30 days. Results: About 2569 procedures were performed in 1842 neonates of which 10.9% were emergency surgeries. There were 120 postoperative severe complications and 965 nonsevere postoperative outcomes. Overall, 30‐day mortality was 1.8% for the first procedure performed, with higher mortality seen on subgroup analysis for patients who underwent exploratory laparotomy (10.3%) and congenital lung lesion resection (4.9%). Postoperative areas for improvement included hyperglycemia (13.9%) and hypothermia (7.9%). Discussion: The mortality rate in our study was comparable to other studies of neonatal surgery despite a high rate of emergency surgery and a high prevalence of prematurity in our cohort. The early outcomes data identified areas for improvement, including prevention of postoperative glucose and temperature derangements. Conclusions: Neonates in this cohort were at risk for severe and nonsevere adverse postoperative outcomes. Future studies are suggested to improve mortality and adverse event rates. [ABSTRACT FROM AUTHOR]
- Published
- 2024
- Full Text
- View/download PDF
33. Carbon-chain chemistry in the interstellar medium.
- Author
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Taniguchi, Kotomi, Gorai, Prasanta, and Tan, Jonathan C.
- Subjects
- *
INTERSTELLAR medium , *INTERSTELLAR molecules , *POLYCYCLIC aromatic hydrocarbons , *GAS dynamics , *ASTROCHEMISTRY , *STARS , *PLANETARY nebulae - Abstract
The presence of carbon-chain molecules in the interstellar medium (ISM) has been known since the early 1970s and > 130 such species have been identified to date, making up ∼ 43 % of the total of detected ISM molecules. They are prevalent not only in star-forming regions in our Galaxy but also in other galaxies. These molecules provide important information on physical conditions, gas dynamics, and evolutionary stages of star-forming regions. Larger species of polycyclic aromatic hydrocarbons (PAHs) and fullerenes (C60 and C70), which may be related to the formation of the carbon-chain molecules, have been detected in circumstellar envelopes around carbon-rich Asymptotic Giant Branch (AGB) stars and planetary nebulae, while PAHs are also known to be a widespread component of the ISM in most galaxies. Recently, two line survey projects toward Taurus Molecular Cloud-1 with large single-dish telescopes have detected many new carbon-chain species, including molecules containing benzene rings. These new findings raise fresh questions about carbon-bearing species in the Universe. This article reviews various aspects of carbon-chain molecules, including observational studies, chemical simulations, quantum calculations, and laboratory experiments, and discusses open questions and how future facilities may answer them. [ABSTRACT FROM AUTHOR]
- Published
- 2024
- Full Text
- View/download PDF
34. Star cluster formation from turbulent clumps. II. Gradual star cluster formation.
- Author
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Farias, Juan P, Tan, Jonathan C, and Chatterjee, Sourav
- Subjects
- *
STAR clusters , *STELLAR evolution , *SUPERNOVAE , *NEUTRON stars , *MOLECULAR clouds - Abstract
We investigate the dynamical evolution of star clusters during their formation, assuming that they are born from a turbulent starless clump of a given mass that is embedded within a parent self-gravitating molecular cloud characterized by a particular mass surface density. In contrast to the standard practice of most N -body studies, we do not assume that all stars are formed at once. Rather, we explore the effects of different star formation rates on the global structure and evolution of young embedded star clusters, also considering various primordial binary fractions and mass segregation levels. Our fiducial clumps studied in this paper have initial masses of |$M_{\rm cl} = 3000\, M_\odot$|, are embedded in ambient cloud environments of Σcloud = 0.1 and 1 g cm−2, and gradually form stars with an overall efficiency of 50 per cent until the gas is exhausted. We investigate star formation efficiencies per free-fall time in the range εff = 0.01–1, and also compare to the instantaneous case (εff = ∞) of Paper I. We show that most of the interesting dynamical processes that determine the future of the cluster, happen during the early formation phase. In particular, the ejected stellar population is sensitive to the duration of star cluster formation: for example, clusters with longer formation times produce more runaway stars, since these clusters remain in a dense state for longer, thus favouring occurrence of dynamical ejections. We also show that the presence of radial age gradients in star clusters depends sensitively on the star formation efficiency per free-fall time, with observed values being matched best by our slowest forming clusters with εff ≲ 0.03. [ABSTRACT FROM AUTHOR]
- Published
- 2019
- Full Text
- View/download PDF
35. formation of supermassive black holes from Population III.1 seeds. I. Cosmic formation histories and clustering properties.
- Author
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Banik, Nilanjan, Tan, Jonathan C, and Monaco, Pierluigi
- Subjects
- *
SUPERMASSIVE black holes , *STAR formation , *DARK matter , *GALACTIC halos , *REDSHIFT - Abstract
We calculate cosmic distributions in space and time of the formation sites of the first, 'Pop III.1' stars, exploring a model in which these are the progenitors of all supermassive black holes (SMBHs), seen in the centres of most large galaxies. Pop III.1 stars are defined to form from primordial composition gas in dark matter minihaloes with |${\sim }10^6\, \mathrm{M}_\odot$| that are isolated from neighbouring astrophysical sources by a given isolation distance, d iso. We assume Pop III.1 sources are seeds of SMBHs, based on protostellar support by dark matter annihilation heating that allows them to accrete a large fraction of their minihalo gas, i.e. |${\sim }10^5\, \mathrm{M}_\odot$|. Exploring d iso from 10 to |$100\, \rm {kpc}$| (proper distances), we predict the redshift evolution of Pop III.1 source and SMBH remnant number densities. The local, |$z$| = 0 density of SMBHs constrains |$d_{\rm {iso}}\lesssim 100\, \rm {kpc}$| (i.e. |$3\, \rm {Mpc}$| comoving distance at |$z$| ≃ 30). In our simulated (|${\sim }60\, \rm {Mpc})^3$| comoving volume, Pop III.1 stars start forming just after |$z$| = 40. Their formation is largely complete by |$z$| ≃ 25–20 for d iso = 100– |$50\, \rm {kpc}$|. We follow source evolution to |$z$| = 10, by which point most SMBHs reside in haloes with |${\gtrsim }10^8\, \mathrm{M}_\odot$|. Over this period, there is relatively limited merging of SMBHs for these values of d iso. We also predict SMBH clustering properties at |$z$| = 10: feedback suppression of neighbouring sources leads to relatively flat angular correlation functions. [ABSTRACT FROM AUTHOR]
- Published
- 2019
- Full Text
- View/download PDF
36. Performance evaluation of Falcon fluidized bowl and ultrafine (UF) bowl concentrators for the recovery of ultrafine scheelite particles.
- Author
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Das, Surya Kanta, Tan, Jonathan, Kundu, Tonmoy, Rath, Swagat S., and Angadi, Shivakumar. I.
- Subjects
- *
SCHEELITE , *MINE waste , *PARTICULATE matter , *INTEGRATED circuits , *CALCITE - Abstract
[Display omitted] • Recovery of ultrafine scheelite particles from a gold mine waste is investigated. • The separation mechanism of particles in the Falcon concentrator is discussed. • Particle size separation limits of both fluidized and UF bowl is examined. • The fluidized bowl can efficiently reject coarse heavy (calcite) particles. • UF bowl can collect fine (10 µm) heavy particles effectively. The recent developments in enhanced gravity concentrators, such as Falcon centrifugal separators, are proven beneficial in treating fine and ultrafine mineral particles. This concentrator is classified into a fluidized bowl concentrator and an ultrafine (UF) bowl concentrator based on the bowl design, which has considerable significance in facilitating the separation process. The present investigation concerns the recovery of ultrafine scheelite particles present in the gold mine tailing with an average WO 3 content of 0.08%. The separation behaviour and application of different bowls concerning various particle sizes have been investigated. It is found that the Falcon UF concentrator can achieve a high recovery while the Falcon fluidized bowl can obtain a higher grade. Further, the fluidized bowl was found more effective at eliminating entrapped calcite mineral particles than the UF bowl. The effectiveness of both bowls is assessed in recovering heavy particles of various sizes, and the results show that the fluidized bowl performs better in recovering coarser heavy particles, while the UF bowl performs better in recovering fine heavy particles. Based on these findings, an integrated circuit (fluidized and UF bowls) has been designed, which resulted in achieving a higher (85%) recovery of WO 3 values compared to individual bowls. [ABSTRACT FROM AUTHOR]
- Published
- 2023
- Full Text
- View/download PDF
37. Origin and Immunological Functions of Spleen Stromal Cells.
- Author
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Golub, Rachel, Tan, Jonathan, Watanabe, Takeshi, and Brendolan, Andrea
- Subjects
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SPLEEN physiology , *STROMAL cells , *IMMUNODEFICIENCY , *REGULATION of hematopoiesis , *LABORATORY mice - Abstract
The mammalian spleen is a peripheral lymphoid organ that plays a central role in host defense. Consequently, the lack of spleen is often associated with immunodeficiency and increased risk of overwhelming infections. Growing evidence suggests that non-hematopoietic stromal cells are central players in spleen development, organization, and immune functions. In addition to its immunological role, the spleen also provides a site for extramedullary hematopoiesis (EMH) in response to injuries. A deeper understanding of the biology of stromal cells is therefore essential to fully comprehend how these cells modulate the immune system during normal and pathological conditions. Here, we review the specificities of the different mouse spleen stromal cell subsets and complement the murine studies with human data when available. [ABSTRACT FROM AUTHOR]
- Published
- 2018
- Full Text
- View/download PDF
38. Ecumenical and Inter-religious Contributions to Asian Liberation Theologies.
- Author
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Tan, Jonathan Y.
- Subjects
- *
PHILOSOPHY of liberation , *INTERFAITH relations , *ATTITUDES of theologians , *ASIAN Christian missions , *SOCIAL justice - Abstract
This essay surveys the varieties of liberation theologies that have emerged in different religious communities across Asia. It explores how Asian liberation theologians from across the major religious traditions of Asia have sought answers from within their own religious traditions and social locations to the endemic persistence of mass poverty, exploitative socio-economic structures, and oppressive political systems that often deny basic human and democratic rights to the poor and marginalized masses in Asia. The article's basic premise is that liberation and social justice are not monopolies of Christianity, but are found across the great religious traditions of Asia, and it highlights examples such as Mahatma Gandhi in Indian Hinduism, B. R. Ambedkar in Indian Buddhism, and Buddhadasa Bhikkhu in Thai Buddhism. Christian examples include Aloysius Pieris (Sri Lanka), Dalit and indigenous tribal theologies from India, and Minjung theology from Korea. [ABSTRACT FROM AUTHOR]
- Published
- 2017
- Full Text
- View/download PDF
39. The formation of supermassive black holes from Population III.1 seeds. II. Evolution to the local universe.
- Author
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Singh, Jasbir, Monaco, Pierluigi, and Tan, Jonathan C
- Subjects
- *
DARK matter , *STATISTICAL correlation , *SUPERMASSIVE black holes , *GALAXY formation , *SEEDS ,UNIVERSE - Abstract
We present predictions for cosmic evolution of populations of supermassive black holes (SMBHs) forming from Population III.1 seeds, i.e. early, metal-free dark matter minihaloes forming far from other sources, parametrized by isolation distance, d iso. Extending previous work that explored this scenario to z = 10, we follow evolution of a |$(60\, {\rm {Mpc}})^3$| volume to z = 0. We focus on evolution of SMBH comoving number densities, halo occupation fractions, angular clustering, and 3D clustering, exploring a range of d iso constrained by observed local number densities of SMBHs. We also compute synthetic projected observational fields, in particular, a case comparable to the Hubble Ultra Deep Field. We compare Pop III.1 seeding to a simple halo mass threshold model, commonly adopted in cosmological simulations of galaxy formation. Major predictions of the Pop III.1 model include that all SMBHs form by z ∼ 25, after which their comoving number densities are near-constant, with low merger rates. Occupation fractions evolve to concentrate SMBHs in the most massive haloes by z = 0, but with rare cases of SMBHs in haloes down to |$\sim 10^8\, M_\odot$|. The d iso scale at epoch of formation, e.g. |$100\,$| kpc-proper at z ∼ 30, i.e. |$\sim 3\,$| Mpc-comoving, is imprinted in the SMBH two-point angular correlation function, remaining discernible as a low-amplitude feature to z ∼ 1. The SMBH 3D two-point correlation function at z = 0 also shows lower amplitude compared to equivalently massive haloes. We discuss prospects for testing these predictions with observational surveys of SMBH populations. [ABSTRACT FROM AUTHOR]
- Published
- 2023
- Full Text
- View/download PDF
40. Insights into secondary reactions occurring during atmospheric ablation of micrometeoroids.
- Author
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Court, Richard W. and Tan, Jonathan
- Subjects
- *
METEOROIDS , *FOURIER transform spectroscopy , *SULFATES analysis , *CARBON dioxide analysis , *ABLATION (Aerothermodynamics) - Abstract
Ablation of micrometeoroids during atmospheric entry yields volatile gases such as water, carbon dioxide, and sulfur dioxide, capable of altering atmospheric chemistry and hence the climate and habitability of the planetary surface. While laboratory experiments have revealed the yields of these gases during laboratory simulations of ablation, the reactions responsible for the generation of these gases have remained unclear, with a typical assumption being that species simply undergo thermal decomposition without engaging in more complex chemistry. Here, pyrolysis-Fourier transform infrared spectroscopy reveals that mixtures of meteorite-relevant materials undergo secondary reactions during simulated ablation, with organic matter capable of taking part in carbothermic reduction of iron oxides and sulfates, resulting in yields of volatile gases that differ from those predicted by simple thermal decomposition. Sulfates are most susceptible to carbothermic reduction, producing greater yields of sulfur dioxide and carbon dioxide at lower temperatures than would be expected from simple thermal decomposition, even when mixed with meteoritically relevant abundances of low-reactivity Type IV kerogen. Iron oxides were less susceptible, with elevated yields of water, carbon dioxide, and carbon monoxide only occurring when mixed with high abundances of more reactive Type III kerogen. We use these insights to reinterpret previous ablation simulation experiments and to predict the reactions capable of occurring during ablation of carbonaceous micrometeoroids in atmospheres of different compositions. [ABSTRACT FROM AUTHOR]
- Published
- 2016
- Full Text
- View/download PDF
41. To Port or Starboard? Why the Supreme Court Might Provide Direction to Those Navigating Choice-of-Law Questions in Maritime-Lien Cases: The 2015 Nicholas J. Mealy Lecture.
- Author
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Davis, Mark S. and Tan, Jonathan T.
- Subjects
- *
MARITIME liens , *MARITIME law , *CONFLICT of laws , *MARITIME shipping , *TORT claims acts , *ADMINISTRATIVE procedure - Abstract
The article reports the need of the U.S. Supreme Court to provide direction to navigating choice-of-law questions in maritime-lien cases. Topics discussed include enactment of Federal Maritime Lien Act in the U.S.; maritime lien concerning contract or tort claims, and the U.S. court case "World Fuel Services Trading, DMCC v. Hebei Prince Shipping Co." on choice-of-law provisions in determining whether to enforce a maritime lien.
- Published
- 2015
42. Voluntary contributions by consent or dissent.
- Author
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Tan, Jonathan H.W., Breitmoser, Yves, and Bolle, Friedel
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- *
GAME theory , *STEADY state conduction , *ECONOMIC equilibrium , *PREDICTION theory , *INFORMATION theory - Abstract
We study games where voluntary contributions can be adjusted until a steady state is reached. In consent games contributions start low and can be increased; in dissent games contributions start high and can be decreased. The equilibrium prediction is free riding in consent games but as much as social efficiency in dissent games. We test it experimentally and confirm that the dissent mechanism yields substantial welfare improvements over the consent mechanism. With experience, subjects contribute on average less than 30% of the endowment in consent games but more than 60% in dissent games. Generally, subjects match the lower of the opponents' contributions: they do not follow when single opponents increase contributions in consent games, but follow when single opponents decrease contributions in dissent games. This asymmetry in the conditional cooperation is predicted by heterogeneity of egoistic and inequity averse types, with individual types being private information. [ABSTRACT FROM AUTHOR]
- Published
- 2015
- Full Text
- View/download PDF
43. Protostellar Feedback Processes and the Mass of the First Stars.
- Author
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Tan, Jonathan C., Smith, Britton D., and O'Shea, Brian W.
- Subjects
- *
DARK matter , *REDSHIFT , *STELLAR initial mass function , *ANNIHILATION reactions , *ACCRETION (Astrophysics) , *COMPUTER simulation , *STAR formation - Abstract
We review theoretical models of Population III.1 star formation, focusing on the proto-stellar feedback processes that are expected to terminate accretion and thus set the mass of these stars. We discuss how dark matter annihilation may modify this standard feedback scenario. Then, under the assumption that dark matter annihilation is unimportant, we predict the mass of stars forming in 12 cosmological minihalos produced in independent numerical simulations. This allows us to make a simple estimate of the Pop III.1 initial mass function and how it may evolve with redshift. [ABSTRACT FROM AUTHOR]
- Published
- 2010
- Full Text
- View/download PDF
44. Star Formation at Zero and Very Low Metallicities.
- Author
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Tan, Jonathan C. and McKee, Christopher F.
- Subjects
- *
STAR formation , *IONIZATION (Atomic physics) , *STELLAR winds , *STELLAR activity , *METAPHYSICAL cosmology , *GALACTIC halos - Abstract
We describe how star formation is expected to proceed in the early metal-free Universe, focusing on the very first generations of stars. We then discuss how the star formation process may change as the effects of metallicity, external radiative feedback, and magnetic and turbulent support of the gas become more important. The very first stars (Pop III. 1) have relatively simple initial conditions set by cosmology and the cooling properties of primordial gas. We describe the evolution of these stars as they grow in mass by accretion from their surrounding gas cores and how the accretion process is affected and eventually terminated by radiative feedback processes, especially H II region expansion and disk photoevaporation. The ability of the protostar and its disk to generate dynamically important magnetic fields is reviewed and their effects discussed. Pop III. 1 star formation is likely to produce massive (∼100–200M⊙) stars that then influence their surroundings via ionization, stellar winds, and supernovae. These processes heat, ionize and metal-enrich the gas, thus altering the initial conditions for the next generation of star formation. Stars formed from gas that has been altered significantly by radiative and/or mechanical feedback, but not by metal enrichment (Pop III.2) are expected to have significantly smaller masses than Pop III.1 stars because of more efficient cooling from enhanced HD production. Stars formed from gas that is metal-enriched to levels that affect the dynamics of the collapse (the first Pop II stars) are also expected to have relatively low masses. We briefly compare the above star formation scenarios to what is known about present-day star formation. [ABSTRACT FROM AUTHOR]
- Published
- 2008
- Full Text
- View/download PDF
45. Mass Limits to Primordial Star Formation from Protostellar Feedback.
- Author
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Tan, Jonathan C. and McKee, Christopher F.
- Subjects
- *
STAR formation , *GALAXY formation - Abstract
How massive were the first stars? This question is of fundamental importance for galaxy formation and cosmic reionization. Here we consider how protostellar feedback can limit the mass of a forming star. For this we must understand the rate at which primordial protostars accrete, how they and their feedback output evolve, and how this feedback interacts with the infalling matter. We describe the accretion rate with an "isentropic accretion" model: ...[sub *], is initially very large (0_03M[sub ⊙] yr[sup -1] when m, = 1M[sub ⊙]) and declines as m[sup -3/7, sub *]. Protostellar evolution is treated with a model that tracks the total energy of the star. A key difference compared to previous studies is allowance for rotation of the infalling envelope. This leads to photospheric conditions at the star and dramatic differences in the feedback. Two feedback mechanisms are considered: HII region breakout and radiation pressure from Lyman-α and FUV photons. Radiation pressure appears to be the dominant mechanism for suppressing infall, becoming dynamically important around 20 M[sub ⊙]. [ABSTRACT FROM AUTHOR]
- Published
- 2003
46. Trans-relativistic supernovae, circumstellar gamma-ray bursts, and supernova 1998bw.
- Author
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Matzner, Christopher D., Tan, Jonathan C., and McKee, Christopher F.
- Subjects
- *
GAMMA ray bursts , *SUPERNOVAE , *RELATIVISTIC astrophysics - Abstract
Supernova (SN) 1998bw and gamma-ray burst (GRB) 980425 offer the first direct evidence that supernovae are the progenitors of some GRBs. However, this burst was unusually dim, smooth and soft compared to other bursts with known afterglows. Whether it should be considered a prototype for cosmological GRBs depends largely on whether the supernova explosion and burst were asymmetrical or can be modeled as spherical. We address this question by treating the acceleration of the supernova shock in the outermost layers of the stellar envelope, the transition to relativistic flow, and the subsequent expansion (and further acceleration) of the ejecta into the surrounding medium. We find that GRB 980425 could plausibly have been produced by a collision between the relativistic ejecta from SN 1998bw and the star's pre-supernova wind; the model requires no significant asymmetry. This event therefore belongs to a dim subclass of GRBs and is not a prototype for jet-like cosmological GRBs. [ABSTRACT FROM AUTHOR]
- Published
- 2001
47. Evaluation of scoring systems and prognostic factors in patients with spinal metastases from nasopharyngeal carcinoma.
- Author
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Kumar, Naresh, Tan, Jonathan J.H., Zaw, Aye S., Lim, Joel L., Wai, Khin L., Malhotra, Rishi, Loh, Thomas K.S., Liu, Gabriel K.P., and Thambiah, Joseph
- Subjects
- *
SPINAL cord cancer , *METASTASIS , *PHARYNGEAL cancer , *MEDICAL decision making , *REGRESSION analysis , *PROGNOSIS , *PATIENTS - Abstract
Background context The decision for operative treatment of patients with spinal metastases is dependent on the patient's predicted survival. Tokuhashi, Tomita, Bauer, and Oswestry scores have been devised for survival prediction; however, none of these systems have been evaluated in nasopharyngeal carcinoma (NPC). Purpose To investigate the accuracy of these scoring systems in predicting survival and to identify prognostic factors for survival of the patients with spinal metastases from NPC. Study design Retrospective analysis of the patients with spinal metastases from NPC who were treated in our institution. Patient sample The study included 87 patients with spinal metastases from NPC. Outcome measures The primary outcome measure was the survival time of these patients. The potential prognostic factors that are known to influence survival such as general condition, extraspinal bone metastases, vertebral bone metastases, visceral metastases, and neurologic assessment based on Frankel score were also studied. Methods The predicted survival according to the four scoring systems were calculated and labeled as “A” scores. These patients were then rescored by assigning NPC as a good prognostic tumor and labeled as “B” scores. The predicted survival of scores A and B were compared with actual survival. Potential prognostic factors of survival were investigated using univariate and multivariate Cox regression analyses. For all scoring systems, Kaplan-Meier survival estimates and log-rank tests were done; the predictive values were calculated using postestimation after Cox regression analyses. Results The median overall survival for the whole cohort was 13 (range 1–120) months. In multivariate analysis, general condition (p<.01), visceral metastases (p<.01), and vertebral metastases (p<.01) showed significant association with survival. The absolute score of all scoring systems was significantly associated with actual survival, which extended to the different prognostic subgroups of each scoring systems. Log-rank test revealed significant differences in survival between the different prognostic subgroups of all scoring systems (p<.01). Predictive value of survival by modified Tokuhashi score was the highest among all four scoring systems. Conclusions Patients with spinal metastases from NPC have relatively good survival prognosis. All four scoring systems could be used to prognosticate these patients. The modified Tokuhashi score is the best in doing so. [ABSTRACT FROM AUTHOR]
- Published
- 2014
- Full Text
- View/download PDF
48. Mapping of Incontinence Quality of Life (I-QOL) scores to Assessment of Quality of Life 8D (AQoL-8D) utilities in patients with idiopathic overactive bladder.
- Author
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Gang Chen, Tan, Jonathan T., Kwong Ng, Iezzi, Angelo, and Richardson, Jeffrey
- Subjects
- *
QUALITY of life , *OVERACTIVE bladder , *ALGORITHMS , *LEAST squares , *URINARY incontinence , *PATIENTS - Abstract
Background The Incontinence Quality of Life (I-QOL) questionnaire is a commonly used and validated incontinence specific QOL instrument. The objective of this study is to develop an algorithm to map I-QOL to the Assessment of Quality of Life (AQoL) 8D utility instrument in patients with idiopathic overactive bladder (iOAB). Methods I-QOL and AQoL-8D scores were collected in a survey of 177 Australian adults with urinary incontinence due to iOAB. Three statistical methods were used for estimation, namely ordinary least squares (OLS) regression, the robust MM-estimator, and the generalised linear models (GLM). Each included a range of explanatory variables. Model performance was assessed using key goodness-of-fit measures in the validation dataset. Results The I-QOL total score and AQoL-8D utility scores were positively correlated (r = 0.50, p < 0.0001). Similarly, the three sub-scales of the I-QOL were correlated with the eight dimensions and two super-dimensions of the AQoL-8D. The GLM estimator, with I-QOL total score as the explanatory variable exhibited the best precision (MAE = 0.15 and RMSE = 0.18) with a mapping function given by AQoL-8D = exp(-1.28666 + 1.011072*I-QOL/100). Conclusions The mapping algorithm developed in this study allows the derivation of AQoL-8D utilities from I-QOL scores. The algorithm allows the calculation of preference-based QOL scores for use in cost-utility analyses to assess the impact of interventions in urinary incontinence. [ABSTRACT FROM AUTHOR]
- Published
- 2014
- Full Text
- View/download PDF
49. Murine Spleen Tissue Regeneration from Neonatal Spleen Capsule Requires Lymphotoxin Priming of Stromal Cells.
- Author
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Tan, Jonathan K. H. and Takeshi Watanabe
- Subjects
- *
SPLEEN , *REGENERATION (Biology) , *TUMOR necrosis factors , *STROMAL cells , *SPLENECTOMY , *MORPHOGENESIS , *LABORATORY mice - Abstract
Spleen is a tissue with regenerative capacity, which allows allotransplantation of human spleen fragments to counteract the effects of splenectomy. We now reveal in a murine model that transplant of neonatal spleen capsule alone leads to the regeneration of full spleen tissue. This finding indicates that graft-derived spleen stromal cells, but not lymphocytes, are essential components of tissue neogenesis, a finding verified by transplant and regeneration of Ragl KO spleen capsules. We further demonstrate that lymphotoxin and lymphoid tissue inducer cells participate in two key elements of spleen neogenesis, bulk tissue regeneration and white pulp organization, identifying a lymphotoxin-dependent pathway for neonatal spleen regeneration that contrasts with previously defined lymphotoxin-independent embryonic spleen organogenesis. [ABSTRACT FROM AUTHOR]
- Published
- 2014
- Full Text
- View/download PDF
50. On the beliefs off the path: Equilibrium refinement due to quantal response and level-k.
- Author
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Breitmoser, Yves, Tan, Jonathan H.W., and Zizzo, Daniel John
- Subjects
- *
ECONOMIC equilibrium , *GAME theory , *MARKOV processes , *ECONOMIC models , *PREDICTION theory , *LEARNING - Abstract
Abstract: The extensive form game we study has multiple perfect equilibria, but it has a unique limiting logit equilibrium (QRE) and a unique level-k prediction as k approaches infinity. The convergence paths of QRE and level-k are different, but they converge to the same limit point. We analyze whether subjects adapt beliefs when gaining experience, and if so whether they take the QRE or the level-k learning path. We estimate transitions between level-k and QRE belief rules using Markov-switching rule learning models. The analysis reveals that subjects take the level-k learning path and that they advance gradually, switching from level 1 to 2, from level 2 to equilibrium, and reverting to level 1 after observing opponents deviating from equilibrium. The steady state therefore contains a mixture of behavioral rules: levels 0, 1, 2, and equilibrium with weights of 2.9%, 16.6%, 37.9%, and 42.6%, respectively. [Copyright &y& Elsevier]
- Published
- 2014
- Full Text
- View/download PDF
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