2,938 research outputs found
Semimetallic behavior in Heusler-type Ru2TaAl and thermoelectric performance improved by off-stoichiometry
We report a study of the temperature-dependent electrical resistivity, Seebeck coefficient, thermal conductivity, specific heat, and Al27 nuclear magnetic resonance (NMR) in Heusler-type Ru2TaAl, to shed light on its semimetallic behavior. While the temperature dependence of the electrical resistivity exhibits semiconductorlike behavior, the analysis of low-temperature specific heat reveals a residual Fermi-level density of states (DOS). Both observations can be realized by means of a semimetallic scenario with the Fermi energy located in the pseudogap of the electronic DOS. The NMR Knight shift and spin-lattice relaxation rate show activated behavior at higher temperatures, attributing to the thermally excited carriers across a pseudogap in Ru2TaAl. From the first-principles band structure calculations, we further provide a clear picture that an indirect overlap between electron and hole pockets is responsible for the formation of a pseudogap in the vicinity of the Fermi level of Ru2TaAl. In addition, an effort for improving the thermoelectric performance of Ru2TaAl has been made by investigating the thermoelectric properties of Ru1.95Ta1.05Al. We found significant enhancements in the electrical conductivity and Seebeck coefficient and marked reduction in the thermal conductivity via the off-stoichiomet ric approach. This leads to an increase in the figure-of-merit ZT value from 6.1×10-4 in Ru2TaAl to 3.4×10-3 in Ru1.95Ta1.05Al at room temperature. In this respect, a further improvement of thermoelectric performance based on Ru2TaAl through other off-stoichiometric attempts is highly probable
Macrophage-derived human resistin is induced in multiple helminth infections and promotes inflammatory monocytes and increased parasite burden.
Parasitic helminth infections can be associated with lifelong morbidity such as immune-mediated organ failure. A better understanding of the host immune response to helminths could provide new avenues to promote parasite clearance and/or alleviate infection-associated morbidity. Murine resistin-like molecules (RELM) exhibit pleiotropic functions following helminth infection including modulating the host immune response; however, the relevance of human RELM proteins in helminth infection is unknown. To examine the function of human resistin (hResistin), we utilized transgenic mice expressing the human resistin gene (hRetnTg+). Following infection with the helminth Nippostrongylus brasiliensis (Nb), hResistin expression was significantly upregulated in infected tissue. Compared to control hRetnTg- mice, hRetnTg+ mice suffered from exacerbated Nb-induced inflammation characterized by weight loss and increased infiltration of inflammatory monocytes in the lung, along with elevated Nb egg burdens and delayed parasite expulsion. Genome-wide transcriptional profiling of the infected tissue revealed that hResistin promoted expression of proinflammatory cytokines and genes downstream of toll-like receptor signaling. Moreover, hResistin preferentially bound lung monocytes, and exogenous treatment of mice with recombinant hResistin promoted monocyte recruitment and proinflammatory cytokine expression. In human studies, increased serum resistin was associated with higher parasite load in individuals infected with soil-transmitted helminths or filarial nematode Wuchereria bancrofti, and was positively correlated with proinflammatory cytokines. Together, these studies identify human resistin as a detrimental factor induced by multiple helminth infections, where it promotes proinflammatory cytokines and impedes parasite clearance. Targeting the resistin/proinflammatory cytokine immune axis may provide new diagnostic or treatment strategies for helminth infection and associated immune-mediated pathology
Mesoscale modeling and simulation of microstructure evolution during dynamic recrystallization of a Ni-based superalloy
Microstructural evolution and plastic flow characteristics of a Ni-based superalloy were investigated using a simulative model that couples the basic metallurgical principle of dynamic recrystallization (DRX) with the twodimensional (2D) cellular automaton (CA). Variation of dislocation density with local strain of deformation is considered for accurate determination of the microstructural evolution during DRX. The grain topography, the grain size and the recrystallized fraction can be well predicted by using the developed CA model, which enables to the establishment of the relationship between the flow stress, dislocation density, recrystallized fraction volume, recrystallized grain size and the thermomechanical parameters
The Unmet Need for Interpreting Provision in UK Primary Care
Background: With increasing globalisation, the challenges of providing accessible and safe healthcare to all are great. Studies show that there are substantial numbers of people who are not fluent in English to a level where they can make best use of health services. We examined how health professionals manage language barriers in a consultation.Methods and Findings: This was a cross-sectional study in 41 UK general practices. Health professionals completed a proforma for a randomly allocated consultation session. Seventy-seven (63%) practitioners responded, from 41(59%) practices. From 1008 consultations, 555 involved patients who did not have English as a first language; 710 took place in English; 222 were in other languages, the practitioner either communicating with the patient in their own language/using an alternative language. Seven consultations were in a mixture of English/patient's own language. Patients' first languages numbered 37 (apart from English), in contrast to health practitioners, who declared at least a basic level of proficiency in 22 languages other than English. The practitioner's reported proficiency in the language used was at a basic level in 24 consultations, whereas in 21, they reported having no proficiency at all. In 57 consultations, a relative/friend interpreted and in 6, a bilingual member of staff/community worker was used. Only in 6 cases was a professional interpreter booked. The main limitation was that only one random session was selected and assessment of patient/professional fluency in English was subjective.Conclusions: It would appear that professional interpreters are under-used in relation to the need for them, with bilingual staff/family and friends being used commonly. In many cases where the patient spoke little/no English, the practitioner consulted in the patient's language but this approach was also used where reported practitioner proficiency was low. Further research in different setting is needed to substantiate these findings
Ancient evolutionary origin of vertebrate enteric neurons from trunk-derived neural crest
The enteric nervous system of jawed vertebrates arises primarily from vagal neural crest cells that migrate to the foregut and subsequently colonize and innervate the entire gastrointestinal tract. Here we examine development of the enteric nervous system in the basal jawless vertebrate the sea lamprey (Petromyzon marinus) to gain insight into its evolutionary origin. Surprisingly, we find no evidence for the existence of a vagally derived enteric neural crest population in the lamprey. Rather, labelling with the lipophilic dye DiI shows that late-migrating cells, originating from the trunk neural tube and associated with nerve fibres, differentiate into neurons within the gut wall and typhlosole. We propose that these trunk-derived neural crest cells may be homologous to Schwann cell precursors, recently shown in mammalian embryos to populate post-embryonic parasympathetic ganglia, including enteric ganglia. Our results suggest that neural-crest-derived Schwann cell precursors made an important contribution to the ancient enteric nervous system of early jawless vertebrates, a role that was largely subsumed by vagal neural crest cells in early gnathostomes
Performance of the CMS Cathode Strip Chambers with Cosmic Rays
The Cathode Strip Chambers (CSCs) constitute the primary muon tracking device
in the CMS endcaps. Their performance has been evaluated using data taken
during a cosmic ray run in fall 2008. Measured noise levels are low, with the
number of noisy channels well below 1%. Coordinate resolution was measured for
all types of chambers, and fall in the range 47 microns to 243 microns. The
efficiencies for local charged track triggers, for hit and for segments
reconstruction were measured, and are above 99%. The timing resolution per
layer is approximately 5 ns
Caveolin-1 protects B6129 mice against Helicobacter pylori gastritis.
Caveolin-1 (Cav1) is a scaffold protein and pathogen receptor in the mucosa of the gastrointestinal tract. Chronic infection of gastric epithelial cells by Helicobacter pylori (H. pylori) is a major risk factor for human gastric cancer (GC) where Cav1 is frequently down-regulated. However, the function of Cav1 in H. pylori infection and pathogenesis of GC remained unknown. We show here that Cav1-deficient mice, infected for 11 months with the CagA-delivery deficient H. pylori strain SS1, developed more severe gastritis and tissue damage, including loss of parietal cells and foveolar hyperplasia, and displayed lower colonisation of the gastric mucosa than wild-type B6129 littermates. Cav1-null mice showed enhanced infiltration of macrophages and B-cells and secretion of chemokines (RANTES) but had reduced levels of CD25+ regulatory T-cells. Cav1-deficient human GC cells (AGS), infected with the CagA-delivery proficient H. pylori strain G27, were more sensitive to CagA-related cytoskeletal stress morphologies ("humming bird") compared to AGS cells stably transfected with Cav1 (AGS/Cav1). Infection of AGS/Cav1 cells triggered the recruitment of p120 RhoGTPase-activating protein/deleted in liver cancer-1 (p120RhoGAP/DLC1) to Cav1 and counteracted CagA-induced cytoskeletal rearrangements. In human GC cell lines (MKN45, N87) and mouse stomach tissue, H. pylori down-regulated endogenous expression of Cav1 independently of CagA. Mechanistically, H. pylori activated sterol-responsive element-binding protein-1 (SREBP1) to repress transcription of the human Cav1 gene from sterol-responsive elements (SREs) in the proximal Cav1 promoter. These data suggested a protective role of Cav1 against H. pylori-induced inflammation and tissue damage. We propose that H. pylori exploits down-regulation of Cav1 to subvert the host's immune response and to promote signalling of its virulence factors in host cells
Nanomechanical investigation of soft biological cell adhesion using atomic force microscopy
Mechanical coupling between living cells is a complex process that is important for a variety of biological processes. In this study the effects of specific biochemical treatment on cell-to-cell adhesion and single cell mechanics were systematically investigated using atomic force microscopy (AFM) single cell force spectroscopy. Functionalised AFM tipless cantilevers were used for attaching single suspended cells that were brought in contact with substrate cells. Cell-to-cell adhesion parameters, such as maximum unbinding force (F max) and work or energy of detachment (W D), were extracted from the retraction force–displacement (F–d) curves. AFM indentation experiments were performed by indenting single cells with a spherical microbead attached to the cantilever. Hertzian contact model was applied to determine the elastic modulus (E) of single cells. Following treatment of the cells with neutralising antibody for epithelial (E)-cadherin, F max was increased by 25%, whereas W D decreased by 11% in response to a 43% increase in E. The results suggest that although the adhesion force between cells was increased after treatment, the energy of adhesion was decreased due to the reduced displacement separation as manifested by the loss of elastic deformation. Conclusively, changes in single cell mechanics are important underlying factors contributing to cell-to-cell adhesion and hence cytomechanical characterization is critical for cell adhesion measurements
Assessing Walking Ability in People with HTLV-1-Associated Myelopathy Using the 10 Meter Timed Walk and the 6 Minute Walk Test
Five to ten million persons, are infected by HTLV-1 of which 3% will develop HTLV-1-associated myelopathy (HAM) a chronic, disabling inflammation of the spinal cord. Walking, a fundamental, complex, multi-functional task is demanding of multiple body systems. Restricted walking ability compromises activity and participation levels in people with HAM (pwHAM). Therapy aims to improve mobility but validated measures are required to assess change.Prospective observational study.To explore walking capacity in pwHAM, walking endurance using the 6 minute walk (6MW), and gait speed, using the timed 10m walk (10mTW).Out-patient setting in an inner London Teaching hospital.Prospective documentation of 10mTW and 6MW distance; walking aid usage and pain scores measured twice, a median of 18 months apart.Data analysis was completed for twenty-six pwHAM, (8♂; 18♀; median age: 57.8 years; median disease duration: 8 years). Median time at baseline to: complete 10m was 17.5 seconds, versus 21.4 seconds at follow up; 23% completed the 6MW compared to 42% at follow up and a median distance of 55m was covered compared to 71m at follow up. Using the 10mTW velocity to predict the 6MW distance, overestimated the distance walked in 6 minutes (p<0.01). Functional decline over time was captured using the functional ambulation categories.The 10mTW velocity underestimated the degree of disability. Gait speed usefully predicts functional domains, shows direction of functional change and comparison with published healthy age matched controls show that these patients have significantly slower gait speeds. The measured differences over 18 months were sufficient to reliably detect change and therefore these assessments can be useful to detect improvement or deterioration within broader disability grades. Walking capacity in pwHAM should be measured using the 10mTW for gait speed and the 6MW for endurance
High major histocompatibility complex class I polymorphism despite bottlenecks in wild and domesticated populations of the zebra finch ()
Background
Two subspecies of zebra finch, Taeniopygia guttata castanotis and T. g. guttata are native to Australia and the Lesser Sunda Islands, respectively. The Australian subspecies has been domesticated and is now an important model system for research. Both the Lesser Sundan subspecies and domesticated Australian zebra finches have undergone population bottlenecks in their history, and previous analyses using neutral markers have reported reduced neutral genetic diversity in these populations. Here we characterize patterns of variation in the third exon of the highly variable major histocompatibility complex (MHC) class I α chain. As a benchmark for neutral divergence, we also report the first mitochondrial NADH dehydrogenase 2 (ND2) sequences in this important model system.
Results
Despite natural and human-mediated population bottlenecks, we find that high MHC class I polymorphism persists across all populations. As expected, we find higher levels of nucleotide diversity in the MHC locus relative to neutral loci, and strong evidence of positive selection acting on important residues forming the peptide-binding region (PBR). Clear population differentiation of MHC allele frequencies is also evident, and this may be due to adaptation to new habitats and associated pathogens and/or genetic drift. Whereas the MHC Class I locus shows broad haplotype sharing across populations, ND2 is the first locus surveyed to date to show reciprocal monophyly of the two subspecies.
Conclusions
Despite genetic bottlenecks and genetic drift, all surveyed zebra finch populations have maintained high MHC Class I diversity. The diversity at the MHC Class I locus in the Lesser Sundan subspecies contrasts sharply with the lack of diversity in previously examined neutral loci, and may thus be a result of selection acting to maintain polymorphism. Given uncertainty in historical population demography, however, it is difficult to rule out neutral processes in maintaining the observed diversity. The surveyed populations also differ in MHC Class I allele frequencies, and future studies are needed to assess whether these changes result in functional immune differences
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