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Microstructure and mechanical properties of Ti-6Al-4V-5% hydroxyapatite composite fabricated using electron beam powder bed fusion

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Journal of Materials Science & Technology 2019年第2期35卷 309-321页

作者： César A.Terrazas Lawrence E.Murr Diego bermudez Edel Arrieta David A.Roberson ryan b.wicker W.M.Keck Center for 3D Innovation The University of Texas at El PasoEl PasoTX 79968USA Department of Mechanical Engineering The University of Texas at El PasoTX 79968USA Department of Metallurgical Materials and Biomedical EngineeringThe University of Texas at El PasoTX 79968USA

A novel, Ti-6 Al-4 V(Ti64)/Hydroxyapatite(HA at 5% by weight concentration) metal/ceramic composite has been fabricated using electron beam powder bed fusion(EPbF) additive manufacturing(AM): specifically, the commercial electron beam melting(EbM?) process. In addition to solid Ti64 and Ti64/5% HA samples, four different unit cell(model) open-cellular mesh structures for the Ti64/5% HA composite were fabricated having densities ranging from 0.68 to 1.12 g/cm^3, and corresponding Young's moduli ranging from 2.9 to 8.0 GPa, and compressive strengths ranging from ~3 to 11 MPa. The solid Ti64/5%HA composite exhibited an optimal tensile strength of 123 MPa, and elongation of 5.5% in contrast to a maximum compressive strength of 875 MPa. both the solid composite and mesh samples deformed primarily by brittle deformation, with the mesh samples exhibiting erratic, brittle crushing. Solid, EPbF-fabricated Ti64 samples had a Vickers microindentation hardness of 4.1 GPa while the Ti64/5%HA solid composite exhibited a Vickers microindentation hardness of 6.8 GPa. The lowest density Ti64/5%HA composite mesh strut sections had a Vickers microindentation hardness of 7.1 GPa. Optical metallography(OM) and scanning electron microscopy(SEM) analysis showed the HA dispersoids to be highly segregated along domain or grain boundaries, but homogeneously distributed along alpha(hcp) platelet boundaries within these domains in the Ti64 matrix for both the solid and mesh composites. The alpha platelet width varied from ~5 μm in the EPbF-fabricated Ti64 to ~1.1 m for the Ti64/5%HA mesh strut. The precursor HA powder diameter averaged 5 μm, in contrast to the dispersed HA particle diameters in the Ti64/5%HA composite which averaged 0.5 m. This work highlights the use of EPbF AM as a novel process for fabrication of a true composite structure, consisting of a Ti64 matrix and interspersed and exposed HA domains, which to the authors' knowledge has not been reported before. The results also illu

关键词： Hydroxyapatite (HA) Metal-matrix ceramic composites Open-cellular (mesh) structures Electron-beam powder bed fusion (EPbF) Additive manufacturing (AM) Mechanical properties Microstructure characterization

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Metal Fabrication by Additive Manufacturing Using Laser and Electron beam Melting Technologies

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Journal of Materials Science & Technology 2012年第1期28卷 1-14页

作者： Lawrence E. Murr Sara M. Gaytan Diana A. Ramirez Edwin Martinez Jennifer Hernandez Krista N. Amato Patrick W. Shindo Francisco R. Medina ryan b. wicker Department of Metallurgical and Materials Engineering The University of Texas at El PasoEl Paso TX 79968 USA W.M. Keck Center for 3D Innovation The University of Texas at El PasoEl Paso TX 79968 USA

Lawrence E. Murr is Mr.J Mrs. Macintosh Murehison Professor and Chairman of the Department of Metallurgical and Materials Engineering and Ph.D. Program Director in the Materials Research Technology Institute at The University of Texas at El Paso. Dr. Murr received his ***. in physical science from Albright College, and his b.S.E.E. in electronics, his M.S. in engineering mechanics, and his Ph.D. in solidstate science, all from the Pennsylvania State University. Dr. Murr has published 20 books, over 750 scientific and technical articles in a wide range of research areas in materials science and engineering, environmental science and engineering, manufacturing science and engineering （especially rapid prototype/layered manufacturing）,

关键词： Selective laser melting Electron beam melting Additive manufacturing Microstructures Microstructural architecture

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The impact of attractants on pocket gopher trapping

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Current Zoology 2014年第4期60卷 472-478页

作者： Roger A. bALDWIN ryan MEINERZ Steve b. ORLOFF Department of Wildlife Fish and Conservation Biology University of California-Davis Davis CA 95616 USA University of California Cooperative Extension 1655 South Main Street Yreka CA 96097 USA

Pocket gophers （Geomyidae） have an extensive impact on both natural and agricultural systems. Trapping is a tech- nique often used to sample and manage these populations. The identification of an attractant that increases capture rates of pocket gophers would greatly assist researchers and pest management professionals alike. Therefore, we tested the attractiveness of four attractants （peanut butter, anise, grapefruit attractant, and carrot） plus a control （no attractant） using uncovered and covered trap sets to determine what impact they have on visitation and capture rates of pocket gophers. We also determined how the impact of cover status and attractants differ across varying weights and gender of pocket gophers. We found no direct effect of any attracrant on visitation and capture rates of pocket gophers, nor on the gender of captured individuals. However, when no attractant was used, the mtmber of pocket gophers captured per 100 trap nights was greater when trap sets were uncovered vs. when covered, and capture rates were generally high and consistent when using peanut butter as an attractant. Additionally, we noted that covered trap sets that were baited with peanut butter yielded heavier pocket gopher captures than uncovered trap sets using this same attractant. This is key, given the difficulty associated with capturing older, more experienced individuals. Combined with data from a previous investigation, this suggests that there is no advantage to using any attractant when utilizing uncovered trap sets, but there is likely some benefit to using peanut butter in covered trap sets [Current Zoology 60 （4）： 472-478, 2014].

关键词： Attractant Demographics Pocket gopher Thomomys bottae Thomomys talpoides Trapping

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Anterior segment optical coherence tomography-guided transepithelial phototherapeutic keratectomy for scarring of the central cornea following pterygium excision

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International Journal of Ophthalmology(English edition) 2020年第3期13卷 503-508页

作者： Sloan W.Rush ryan b.Rush Panhandle Eye Group AmarilloTX 79106USA Texas Tech University Health Science Center AmarilloTX 79106USA Southwest Retina Specialists AmarilloTX 79106USA

AIM:To report the outcomes of patients undergoing anterior segment optical coherence tomography-guided transepithelial phototherapeutic keratectomy(ASOCT T-PTK)for central corneal scarring after pterygium ***:The charts of 11 eyes of 10 patients that underwent ASOCT T-PTK following excision of visual axisinvolving pterygia were retrospectively reviewed from a single private practice *** visual outcomes and corneal topographic findings were evaluated 4±1 mo after pterygium excision and 6±2 mo after transepithelial phototherapeutic keratectomy(T-PTK).RESULTS:All 11 eyes tolerated both the pterygium excision and T-PTK procedure well without any significant intraoperative or postoperative *** distance visual acuity(UDVA)and manifest refraction corrected distance visual acuity(CDVA)improved after pterygium excision(P=0.03 and P=0.05,respectively).The UDVA and CDVA improved further after T-PTK(P=0.004 and P=0.002,respectively).The topographic surface asymmetry index,topographic surface regularity index,and topographic projected visual acuity significantly improved after T-PTK(P=0.0092,P=0.0022,and P=0.0002,respectively).None of the subjects lost any lines of CDVA,developed recurrence of pterygia or required keratoplasty during the postoperative ***:ASOCT T-PTK can provide excellent visual and anatomic outcomes in patients with central corneal scarring after excision of visual axis-involving pterygia.

关键词： pediatric penetrating eye injury traumatic endophthalmitis pars plana vitrectomy

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Late immune consequences of combat trauma: A review of trauma-related immune dysfunction and potential therapies

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Military Medical Research 2019年第4期6卷 340-353页

作者： Kelly b.Thompson Luke T.Krispinsky ryan J.Stark Division of Critical Care Medicine Department of PediatricsVanderbilt University School of Medicine2200 Children’s WayNashvilleTN 37232USA Division of Pediatric Critical Care Medicine Department of PediatricsUniformed Services UniversityNaval Medical Center PortsmouthPortsmouthVA 23708USA

With improvements in personnel and vehicular body armor,robust casualty evacuation capabilities,and damage control resuscitation strategies,more combat casualties are surviving to reach higher levels of care throughout the casualty evacuation *** such,medical centers are becoming more accustomed to managing the deleterious late consequences of combat trauma related to the dysregulation of the immune *** this review,we aim to highlight these late consequences and identify areas for future research and therapeutic *** leads to the dysregulation of both the innate and adaptive immune responses,which places the injured at risk for several late consequences,including delayed wound healing,late onset sepsis and infection,multi-organ dysfunction syndrome,and acute respiratory distress syndrome,which are significant for their association with the increased morbidity and mortality of wounded *** mechanisms by which these consequences develop are complex but include an imbalance of the immune system leading to robust inflammatory responses,triggered by the presence of damage associated molecules and other immune-modifying agents following *** strategies to improve outcomes have been difficult to develop as the immunophenotype of injured personnel following trauma is variable,fluid and difficult to *** more information regarding the triggers that lead to immune dysfunction following trauma is elucidated,it may be possible to identify the immunophenotype of injured personnel and provide targeted treatments to reduce the late consequences of trauma,which are known to lead to significant morbidity and mortality.

关键词： Trauma Sepsis Compensatory anti-inflammatory response syndrome Persistent inflammationimmunosuppression and catabolism syndrome Immune dysfunction

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Temperature and mass scaling affect cutaneous and pulmonary respiratory performance in a diving frog

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Integrative Zoology 2021年第5期16卷 712-728页

作者： ryan b.MCWHINNIE Jason P.SCKRAbULIS Thomas R.RAFFEL Department of biological Sciences Oakland UniversityRochesterMichiganUSA

Global climate change is altering patterns of temperature variation,with unpredictable consequences for species and *** Metabolic Theory of Ecology(MTE)provides a powerful framework for predicting climate change impacts on ectotherm metabolic *** postulates that physiological and ecological processes are limited by organism metabolic rates,which scale predictably with body mass and *** purpose of this study was to determine if different metabolic proxies generate different empirical estimates of key MTE model parameters for the aquatic frog Xenopus laevis when allowed to exhibit normal diving *** used a novel methodological approach in combining a flow-through respirometry setup with the open-source Arduino platform to measure mass and temperature effects on 4 different proxies for whole-body metabolism(total O_(2) consumption,cutaneous O_(2) consumption,pulmonary O_(2) consumption,and ventilation frequency),following thermal acclimation to one of 3 temperatures(8℃,17℃,or 26℃).Different metabolic proxies generated different mass-scaling exponents(b)and activation energy(EA)estimates,highlighting the importance of metabolic proxy selection when parameterizing MTE-derived *** acclimated to 17℃ had higher O_(2) consumption across all temperatures,but thermal acclimation did not influence estimates of key MTE parameters EA and *** respiration generated lower MTE parameters than pulmonary respiration,consistent with temperature and mass constraints on dissolved oxygen availability,SA:V ratios,and diffusion distances across *** results show that the choice of metabolic proxy can have a big impact on empirical estimates for key MTE model parameters.

关键词： African clawed frog amphibian pneumotachography thermal biology

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Effect of Melt Scan Rate on Microstructure and Macrostructure for Electron beam Melting of Ti-6Al-4V

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Materials Sciences and Applications 2012年第5期3卷 259-264页

作者： Karina Puebla Lawrence E. Murr Sara M. Gaytan Edwin Martinez Francisco Medina ryan b. wicker University of Texas at El Paso El Paso USA

Microstructure and variations in porosity in Ti-6Al-4V samples built with electron beam melting (EbM) over a range of melt scan speeds, ranging from 100 mm·s-1 to 1000 mm·s-1 were examined. Microstructure was characterized by refinement of α-phase and transformation to α′-martensite. Light optical microscopy, scanning electron microscopy, and transmission electron microscopy were used to observe these phenomena, while corresponding tensile testing and associated macro and microindentation hardness measurements were used to define the microstructural variations. Relative stiffness was observed to be linearly log-log related to relative density, corresponding to ideal porosity associated with open-cellular structures.

关键词： Electron beam Melting Additive Manufacturing α-Phase and α′-Martensite Optical and Electron Microscopy Melt-Scan Rate

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Advances in alcoholic liver disease:An update on alcoholic hepatitis

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World Journal of Gastroenterology 2015年第42期21卷 11893-11903页

作者： Randy Liang Andy Liu ryan b Perumpail Robert J Wong Aijaz Ahmed Department of Medicine Santa Clara Valley Medical Center Albert Einstein College of Medicine Division of Gastroenterology and Hepatology Stanford University School of Medicine Division of Gastroenterology and Hepatology Alameda Health System-Highland Hospital Campus

Alcoholic hepatitis is a pro-inflammatory chronic liver disease that is associated with high short-term morbidity and mortality(25%-35% in one month) in the setting of chronic alcohol use. Histopathology is notable for micro- and macrovesicular steatosis, acute inflammation with neutrophil infiltration, hepatocellular necrosis, perivenular and perisinusoidal fibrosis, and Mallory hyaline bodies found in ballooned hepatocytes. Other findings include the characteristic eosinophilic fibrillar material(Mallory's hyaline bodies) found in ballooned hepatocytes. The presence of focal intense lobular infiltration of neutrophils is what typically distinguishes alcoholic hepatitis from other forms of hepatitis, in which the inflammatory infiltrate is primarily composed of mononuclear cells. Management consists of a multidisciplinary approach including alcohol cessation, fluid and electrolyte correction, treatment of alcohol withdrawal, and pharmacological therapy based on the severity of the disease. Pharmacological treatment for severe alcoholic hepatitis, as defined by Maddrey's discriminant factor ≥ 32, consists of either prednisolone or pentoxifylline for a period of four weeks. The body of evidence for corticosteroids has been greater than pentoxifylline, although there are higher risks of complications. Recently head-to-head trials between corticosteroids and pentoxifylline have been performed, which again suggests that corticosteroids should strongly be considered over pentoxifylline.

关键词： Alcoholic Hepatitis Maddrey discriminant function

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Hepatitis E virus infection in the liver transplant recipients:Clinical presentation and management

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World Journal of Hepatology 2016年第2期8卷 117-122页

作者： Avin Aggarwal ryan b Perumpail Swetha Tummala Aijaz Ahmed Division of Gastroenterology and Hepatology Stanford University School of Medicine

Hepatitis E virus(HEV) is an emerging pathogen and an increasingly recognized cause of graft hepatitis, especially in the post-orthotopic liver transplantation immunocompromised population. The exact incidence and prevalence of HEV infection in this population remains unclear but is certainly greater than historical estimates. Identifying acute HEV infection in this population is imperative for choosing the right course of management as it is very difficult to distinguish histologically from acute rejection on liver biopsy. Current suggested approach to manage acute HEV involves modifying immunosuppression, especially discontinuing calcineurin inhibitors which are the preferred immunosuppressive agents post-orthotopic liver transplantation. The addition of ribavirin monotherapy has shown promising success rates in clearing HEV infection and is used commonly in reported cases.

关键词： Chronic hepatitis E infection Solid organtransplant Immunosuppression Ribavirin Hepatitis Evirus Orthotopic liver transplantation

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Update on hepatitis C: Direct-acting antivirals

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World Journal of Hepatology 2015年第28期7卷 2829-2833页

作者： Leon L Seifert ryan b Perumpail Aijaz Ahmed Department of Transplantation Medicine University Hospital Münster Division of Gastroenterology and Hepatology Stanford University School of Medicine

Hepatitis C virus(HCV) was discovered 26 years ago. For decades, interferon-based therapy has been the mainstay of treatment for HCV. Recently, several direct-acting antivirals(DAAs) have been approved for treatment of HCV-infected patients and to help combat the virus. These drugs have revolutionized the management of HCV as all-oral regimens with favorable side effect profiles and superior rates of sustained virological response. Emerging real-world data are demonstrating results comparable to registration trials for DAA agents. Suddenly, the potential for eradicating HCV is on the horizon.

关键词： Hepatitis C virus Direct-acting antivirals Sustained virologic response Management Treatment

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