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This work reports on the fabrication of a novel two-layer material composed of a porous tantalum core and a dense Ti6Al4V (Ti64) shell by powder metallurgy. The porous core was obtained by mixing Ta particles and salt space-holders to create large pores, the green compact was obtained by pressing. The sintering behavior of the two-layer sample was studied by dilatometry. The interface bonding between the Ti64 and Ta layers was analyzed by SEM, and the pore characteristics were analyzed by computed microtomography. Images showed that two distinct layers were obtained with a bonding achieved by the solid-state diffusion of Ta particles into Ti64 during sintering. The formation of β-Ti and α′ martensitic phases confirmed the diffusion of Ta. The pore size distribution was in the size range of 80 to 500 µm, and a permeability value of 6 × 10−10 m2 was close to the trabecular bones one. The mechanical properties of the component were dominated mainly by the porous layer, and Young's modulus of 16 GPa was in the range of bones. Additionally, the density of this material (6 g/cm3) was much lower than the one of pure Ta, which helps to reduce the weight for the desired applications. These results indicate that structurally hybridized materials, also known as composites, with specific property profiles can improve the response to osseointegration for bone implant applications. [ABSTRACT FROM AUTHOR]

Annual average daily particle number concentrations around a highway were estimated with an atmospheric dispersion model and a land use regression model. The dispersion model was used to estimate particle concentrations along Interstate 10 at 98 locations within El Paso, Texas. This model employed annual averaged wind speed and annual average daily traffic counts as inputs. A land use regression model with vehicle kilometers traveled as the predictor variable was used to estimate local background concentrations away from the highway to adjust the near-highway concentration estimates. Estimated particle number concentrations ranged between 9.8 × 10 3 particles/cc and 1.3 × 10 5 particles/cc, and averaged 2.5 × 10 4 particles/cc (SE 421.0). Estimates were compared against values measured at seven sites located along I10 throughout the region. The average fractional error was 6% and ranged between −1% and −13% across sites. The largest bias of −13% was observed at a semi-rural site where traffic was lowest. The average bias amongst urban sites was 5%. The accuracy of the estimates depended primarily on the emission factor and the adjustment to local background conditions. An emission factor of 1.63 × 10 14 particles/veh-km was based on a value proposed in the literature and adjusted with local measurements. The integration of the two modeling techniques ensured that the particle number concentrations estimates captured the impact of traffic along both the highway and arterial roadways. The performance and economical aspects of the two modeling techniques used in this study shows that producing particle concentration surfaces along major roadways would be feasible in urban regions where traffic and meteorological data are readily available. [ABSTRACT FROM AUTHOR]

Abstract: In this work, colorimetry was used in order to identify the phase transition of BaTiO3 and KNbO3 ceramic. The transition of the structure produces a change of color of the ceramic bulks because their optical properties change. The transition phase was detected with a color sensor and reflectance method on ceramic bulks. CIE L*a*b* and CIE L*u*v* color spaces were used to measure the color changes reported. Experimental results showed that the changes of color are suitable for detecting the phase transition in both perovskite structures. The phase transition in the proposed ferroelectric materials was also measured by means of the dielectric constant method and the results obtained were in agreement with the temperatures reported for phase transition changes on BaTiO3 and KNbO3. Therefore, the colorimetry technique proposed in this paper proved to be suitable for detecting structure changes as a relationship between color properties and temperature. [ABSTRACT FROM AUTHOR]

Nafion-coated bismuth film electrodes (NCBFEs) and Nafion-coated mercury film electrodes (NCMFEs) were used to electrochemically preconcentrate metal analytes for subsequent analysis by inductively coupled plasma-mass spectrometry (ICP-MS). Either type of electrodes is part of a thin-layer electrochemical flow cell that is positioned upstream of a microconcentric nebulizer for the ICP-MS. Performances of these electrodes were compared in terms of the analytical “figures of merit” (e.g., dynamic ranges, reproducibility, hydrodynamic stability, and elimination of matrix effects detrimental to ICP-MS). The coupled technique (ASV-ICP-MS) is found to possess a wide dynamic range (at least 4 to 5 orders of magnitude) and to be reproducible. Both electrodes are much more stable than the thin mercury film electrode (TMFE) traditionally used for ASV-ICP-MS, with the lifetime of the NCBFE exceeding 8 h. Adopting these electrodes for ASV-ICP-MS overcomes the problems associated with a TMFE, the erosion of which decreases the sample throughput, affects the analysis precision, and contaminates conventional glass nebulizers and spray chambers of the spectrometer. The medium exchange procedure inherent in ASV is successfully implemented with a two-valve flow injection system for the accumulation of trace Cd2+ into the electrode from a certified seawater sample, followed by stripping Cd into a solution that is compatible to the ICP-MS operation. [Copyright &y& Elsevier]

Metallothionein (MT), a cysteine-rich metalloprotein that is purported to play an important role in heavy metal accumulation and detoxification, and its related peptidic species were attached onto dithiobissuccinimidyl propionate self-assembled monolayers. The spatially accessible sulfhydryl groups present in these immobilized biomolecules, tagged with N-biotinoyl-N'-[6-maleimidohexanoyl]- hydrazide, were detected voltammetrically at a sensitive level via the use of ferrocene (Fc)-capped gold nanoparticle/ streptavidin conjugates. The method was established first by examining relatively simple peptides (e.g., glutathione). For the hexapeptidic species that resembles the N-terminus of MT with a sequence of Lys-Cys-Thr-Cys-Cys-Ala, concentration levels as low as 0.050 nM can be determined. Such a remarkable sensitivity is attributed to the presence of a large number of Fc caps present at each gold nanoparticle, which enhances the detection of a small number of surface-bound sulfhydryl groups. Microgravimetric measurements, performed with a quartz crystal microbalance, were used in tandem with voltammetry to quantify the number of tagged sulfhydryl groups. Through extraction of the metals present in MT adsorbate, it is demonstrated that this amplified voltammetric detection is also suitable for the investigation of the variation of the number of sulfhydryl groups present at an electrode and sensitive to the change of surface structure of an immobilized biomolecule. This work represents a new method for the determination of sulfhydryl groups inherent in surface-bound proteins or peptides and can facilitate the study on the environmental issues related to MTs. [ABSTRACT FROM AUTHOR]

Valve sparing aortic root replacement remains a complex procedure despite various improvements that have been made to this operation. Specifically, a hemostatic proximal anastomosis is one of the most important factors for successful completion of the operation without complication. Here we describe a double mattress suture line technique, which facilitates a secure and hemostatic proximal suture line. [ABSTRACT FROM AUTHOR]

The present work is focused on developing Ti-xTa porous alloys processed by the space holder method and solid-state sintering. The volume fraction of Ta ranged between 20 and 30 wt.%. The sintering kinetics was evaluated by dilatometry tests. Sintered materials were characterized by SEM, XRD and computed tomography. Porosity features and permeability were determined from 3D images, and their mechanical properties were evaluated from microhardness and compression tests. The sintering behavior and the final microstructure are driven by the Ta diffusion into the Ti, slowing down the densification and modifying the transition temperature of α-to-β. Due to β-stabilization, martensite α′ was obtained after sintering. Mechanical properties are reduced because of the β-stabilization and pore addition, being predominantly the pore effect. Permeability depended on the pore characteristics, finding values close to the human bones. It was concluded that powder metallurgy generates highly TixTa alloys with a combination of α, β and α′ Ti phases as well as remaining Ta particles that are beneficial to improve the biocompatibility and osseointegration of such materials. Being the Ti25Ta40salt alloy the most suitable for orthopedic implants because of its characteristics and properties. [ABSTRACT FROM AUTHOR]

We present a novel Ti64/20Ag highly porous composite fabricated by powder metallurgy for biomedical applications and provide an insight into its microstructure and mechanical proprieties. In this work, the Ti64/20Ag highly porous composites were successfully fabricated by the space holder technique and consolidated by liquid phase sintering, at lower temperatures than the ones used for Ti64 materials. The sintering densification was evaluated by dilatometry tests and the microstructural characterization and porosity features were determined by scanning electron microscopy and computed microtomography. Permeability was estimated by numerical simulations on the 3D real microstructure. Mechanical properties were evaluated by simple compression tests. Densification was achieved by interparticle pore filling with liquid Ag that does not drain to the large pores, with additional densification due to the macroscopical deformation of large pores. Pore characteristics are closely linked to the pore formers and the permeability was highly increased by increasing the pore volume fraction, mainly because the connectivity was improved. As expected, with the increase in porosity, the mechanical properties decreased. These results permitted us to gain a greater understanding of the microstructure and to confirm that we developed a promising Ti64/20Ag composite, showing E of 7.4 GPa, σy of 123 MPa and permeability of 3.93 × 10−11 m2. Enhanced adaptability and antibacterial proprieties due to Ag were obtained for bone implant applications. [ABSTRACT FROM AUTHOR]

Background Context: Symptomatic epidural hematomas after spinal surgery are uncommon and are usually diagnosed within 24 hours after surgery.Purpose: We report a series of delayed epidural hematomas in a subset of patients who awoke from surgery neurologically unchanged and then deteriorated more than 3 days after their index procedure. The goals of this report are to outline the clinical presentation, radiological characteristics and outcome of this uncommon entity.Study Design/setting: We retrospectively reviewed the database of six spine surgeons over a 4-year period, looking for presence of epidural hematomas as a cause of clinical deterioration after an asymptomatic postoperative period of at least 3 days.Patient Sample: We identified a subset of patients who awoke from surgery neurologically unchanged and then deteriorated more than 3 days after spinal surgery. A total of 4,018 patients were identified over the 4-year period of review.Outcome Measures: Presence of spinal epidural hematoma as a cause of clinical deterioration after an asymptomatic period of at least 3 days. The medical records, including the history, physical, preoperative and postoperative neurological examinations, as well as plain radiographs and magnetic resonance images, were reviewed.Methods: We retrospectively reviewed the database of six spine surgeons over a 4-year period. We looked for delayed spinal epidural hematomas as a cause of clinical deterioration after an asymptomatic postoperative period of at least 3 days. We examined potential risk factors for spinal extradural hematomas.Results: Of 4,018 patients, we identified seven with spinal epidural hematoma who presented more than 3 days after their index procedure. The initial presenting symptom, which heralded the subsequent onset of neurological deterioration, consisted of severe sharp pain with radiation to the extremities. The average time to neurological deterioration was 5.3 days. Fifty-seven percent of the patients had multiple previous spinal surgeries at the site of the epidural hematoma. Surgical evacuation of the epidural hematomas resulted in neurological improvement in five patients. Persistent neurological deficits were observed in two patients.Conclusion: Delayed spinal epidural hematomas are an uncommon cause of delayed deterioration after spinal surgery. Previous surgery with attendant scarring that results in impairment of clot resorption may be a contributing factor in the development of the condition. [ABSTRACT FROM AUTHOR]

Background/Objectives Frailty, characterized by low physiological reserves, is strongly associated with vulnerability to adverse outcomes. Features of frailty overlap with those of advanced heart failure, making a distinction between them difficult. We sought to determine whether implantation of a left ventricular assist device ( LVAD) would decrease frailty. Design Prospective, cohort study. Setting Five academic medical centers. Participants Frail individuals (N = 29; mean age 70.6 ± 5.5, 72.4% male). Measurements Frailty, defined as having 3 or more of the Fried frailty criteria, was assessed before LVAD implantation and 1, 3, and 6 months after implantation. Other domains assessed included quality of life, using the Kansas City Cardiomyopathy Questionnaire; mood, using the Patient Health Questionnaire; and cognitive function, using the Trail-Making Test Part B. Results After 6 months, three subjects had died, and one had undergone a heart transplant; of 19 subjects with serial frailty measures, the average number of frailty criteria decreased from 3.9 ± 0.9 at baseline to 2.8 ± 1.4 at 6 months ( P = .003). Improvements were observed after 3 to 6 months of LVAD support, although 10 (52.6%) participants still had 3 or more Fried criteria, and all subjects had at least one at 6 months. Changes in frailty were associated with improvement in QOL but not with changes in mood or cognition. Higher estimated glomerular filtration rate at baseline was independently associated with a decrease in frailty. Conclusion Frailty decreased in approximately half of older adults with advanced heart failure after 6 months of LVAD support. Strategies to enhance frailty reversal in this population are worthy of additional study. [ABSTRACT FROM AUTHOR]

Background Although computed tomography (CT) has become the preferred diagnostic modality, immediate surgical intervention is often required for severely injured patients with minimum preoperative radiographic evaluation. The utility of postoperative CT (postop-CT) for the identification of undiagnosed injuries and its impact on patient management remain unclear. The purpose of this study was to evaluate the utility of postop-CT for the identification of clinically significant injuries in patients who underwent an emergent life-saving procedure. Methods A 5-y retrospective study from 2009 to 2013 was conducted at a high-volume level I trauma center. We included blunt and penetrating trauma patients who underwent an emergent operation (neck exploration, thoracotomy, and laparotomy) without preoperative CT. Postop-CT was obtained within 48 h after the initial operation at the discretion of the attending trauma surgeon. Characteristics of newly diagnosed injuries on postop-CT were analyzed. These injuries were considered clinically significant when the patient required (1) immediate intervention; (2) new consultation from a specialty service; or (3) a higher level of care. Results A total of 89 patients met our inclusion criteria (five neck explorations, 16 thoracotomies, and 74 laparotomies) with the following characteristics: median age of 30 y, 87.6% male, 47.2% penetrating injury, and median injury severity score of 24. New injuries were identified on postop-CT in 59 cases (66%), and clinical management was changed in 51 cases (57%). Patients with an admission Glasgow Coma Scale <15 and solid organ injury identified during the index operation were more likely to have new injuries on postop-CT. Conclusions In patients undergoing an emergent operation before having their full diagnostic workup completed, postop-CT often demonstrates clinically significant injuries. Further prospective study to identify the patients who will benefit from postop-CT is warranted. [ABSTRACT FROM AUTHOR]