The deformation mechanisms of binary Ti–Al model alloys (0–13.1 at.% Aluminium) have been investigated with respect to the twinning activity using in-situ loading in combination with neutron ...diffraction as well as detailed post mortem electron backscatter diffraction analysis. A consistent starting grain size and texture was generated for all alloys promoting tensile twinning during compression testing. Long-wavelength neutron diffraction and selected area diffraction transmission electron microscopy analysis were carried out to detect evidence of Aluminium ordering and Ti3Al formation.
It was found that raising the Aluminium content in Titanium does first slightly enhance twinning, with {101¯2}<101¯1> tensile twinning being by far the dominant type, while the critical residual intergranular strains for twin initiation decreases. This suggests that either the lowering of stacking fault energy by Aluminium or its solute solution strengthening effect are important factors. At around 7 at.% Aluminium a turning point in twinning activity was noticed and a further increase in Aluminium did result in a dramatic loss of twinning activity particularly when the material had been exposed to an additional low temperature age. The dramatic decrease of twinning activity is strongly correlated with increasing evidence of short range ordering and also early signs of Ti3Al-formation in case of the highest Aluminium content. In addition, electron backscatter diffraction analysis revealed that the formation of Aluminium ordered zones do severely hinder growth of twin boundaries.
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Reasonably determination of the rolling temperature of the cross wedge rolling (CWR) is the key to o btain the qualified surface of the aluminum alloy shaft parts. In this paper, the 6 082 aluminum ...alloy shaft parts with different section shrinkage rate between 43,75 % and 64 % are taken as examples. The thermal-deformation coupling finite element model (FEM) is established to analyze the effect of the process parameters on the temperature field. The influence law of the temperature field on the surface quality in CWR process is obtained and verified by experiment. The results provide theoretical and experimental basis for temperature selection and surface quality improvement.
Recently there has been reinvigorated interest in the superconducting proximity effect, driven by predictions of the emergence of Majorana fermions. To help guide this search, we have developed a ...phenomenological model for the tunneling spectra in anisotropic superconductor-normal metal proximity devices. We combine successful approaches used in s-wave proximity and standard d-wave tunneling to reproduce tunneling spectra in d-wave proximity devices, and clarify the origin of various features. Different variations of the pair potential are considered, resulting from the proximity-induced superconductivity. Furthermore, the effective pair potential felt by the quasiparticles is momentum-dependent in contrast to s-wave superconductors. The probabilities of reflection and transmission are calculated by solving the Bogoliubov equations. Our results are consistent with experimental observations of the unconventional proximity effect and provide important experimental parameters such as the size and length scale of the proximity induced gap, as well as the conditions needed to observe the reduced and full superconducting gaps.
The Step trial raised the possibility that uncircumcised men with pre-existing Ad5 neutralizing antibodies carried an increased risk of HIV infection after vaccination. Thus, understanding Ad ...seropositivity in humans is important to the development of an AIDS vaccine. Here, we analyze the impact of different Ad5-specific neutralizing antibodies on immune function and clinical outcome.
Ad seropositivity in the Step trial volunteers was analyzed using chimeric rAd5/35 vectors to characterize their specificity for Ad5 fiber and non-fiber external (capsid) proteins. Immune responses and HIV seropositivity were correlated with the specificity of Ad5-neutralizing antibodies. Neutralizing antibodies induced by the vaccine in Ad5 seronegative subjects were directed preferentially to Ad5 capsid proteins, although some fiber-neutralizing antibodies could be detected. Pre-vaccination Ad5 serostatus did not affect the capsid-directed response after three vaccinations. In contrast, anti-fiber antibody titers were significantly higher in volunteers who were Ad5 seropositive prior to vaccination. Those Ad5 seropositive subjects who generated anti-capsid responses showed a marked reduction in vaccine-induced CD8 responses. Unexpectedly, anti-vector immunity differed qualitatively in Ad5 seropositive participants who became HIV-1 infected compared to uninfected case controls; Ad5 seropositive participants who later acquired HIV had lower neutralizing antibodies to capsid. Moreover, Ad35 seropositivity was decreased in HIV-infected subjects compared with uninfected case controls, while seroprevalence for other serotypes including Ad14, Ad28 and Ad41 was similar in both groups.
Together, these findings suggest that the case subjects were less immunologically responsive prior to infection. Subjects infected during the Step trial had qualitative differences in immunity that increased their risk of HIV-1 infection independent of vaccination.
Knowledge of the contribution that individual countries have made to global radiative forcing is important to the implementation of the agreement on "common but differentiated responsibilities" ...reached by the United Nations Framework Convention on Climate Change. Over the past three decades, China has experienced rapid economic development, accompanied by increased emission of greenhouse gases, ozone precursors and aerosols, but the magnitude of the associated radiative forcing has remained unclear. Here we use a global coupled biogeochemistry-climate model and a chemistry and transport model to quantify China's present-day contribution to global radiative forcing due to well-mixed greenhouse gases, short-lived atmospheric climate forcers and land-use-induced regional surface albedo changes. We find that China contributes 10% ± 4% of the current global radiative forcing. China's relative contribution to the positive (warming) component of global radiative forcing, mainly induced by well-mixed greenhouse gases and black carbon aerosols, is 12% ± 2%. Its relative contribution to the negative (cooling) component is 15% ± 6%, dominated by the effect of sulfate and nitrate aerosols. China's strongest contributions are 0.16 ± 0.02 watts per square metre for CO2 from fossil fuel burning, 0.13 ± 0.05 watts per square metre for CH4, -0.11 ± 0.05 watts per square metre for sulfate aerosols, and 0.09 ± 0.06 watts per square metre for black carbon aerosols. China's eventual goal of improving air quality will result in changes in radiative forcing in the coming years: a reduction of sulfur dioxide emissions would drive a faster future warming, unless offset by larger reductions of radiative forcing from well-mixed greenhouse gases and black carbon.
A three-dimensional (3D) hyaluronic acid (HA) nanofibrous scaffold was successfully fabricated to mimic the architecture of natural extracelluar matrix (ECM) based on electrospinning. Thiolated HA ...derivative, 3,3′-dithiobis(propanoic dihydrazide)-modified HA (HA-DTPH), was synthesized and electrospun to form 3D nanofibrous scaffolds. In order to facilitate the fiber formation during electrospinning, Poly (ethylene oxide) (PEO) was added into the aqueous solution of HA-DTPH at an optimal weight ratio of 1:1. The electrospun HA-DTPH/PEO blend scaffold was subsequently cross-linked through poly (ethylene glycol)-diacrylate (PEGDA) mediated conjugate addition. PEO was then extracted in DI water to obtain an electrospun HA-DTPH nanofibrous scaffold. NIH 3T3 fibroblasts were seeded on fibronectin-adsorbed HA-DTPH nanofibrous scaffolds for 24
h in vitro. Fluorescence microscopy and laser scanning confocal microscopy revealed that the 3T3 fibroblasts attached to the scaffold and spread, demonstrating an extended dendritic morphology within the scaffold, which suggests potential applications of HA-DTPH nanofibrous scaffolds in cell encapsulation and tissue regeneration.
We address the controversy over the proximity effect between topological materials and high-T c superconductors. Junctions are produced between Bi2Sr2CaCu2O_{8+\delta }$ and materials with different ...Fermi surfaces (Bi2Te3 and graphite). Both cases reveal tunneling spectra that are consistent with Andreev reflection. This is confirmed by a magnetic field that shifts features via the Doppler effect. This is modeled with a single parameter that accounts for tunneling into a screening supercurrent. Thus the tunneling involves Cooper pairs crossing the heterostructure, showing that the Fermi surface mismatch does not hinder the ability to form transparent interfaces, which is accounted for by the extended Brillouin zone and different lattice symmetries.
Hidden magnetic order in the correlated iridate Sr2Ir1−xRhxO4, x=0.05 and 0.1, has been studied using muon spin relaxation spectroscopy. In zero field (ZF) and weak longitudinal fields (LFs) (≲2mT), ...the muon spin relaxation data indicate that static and dynamic local fields coexist at each muon site, and can be well described by exponentially damped static Lorentzian Kubo-Toyabe functions. The ZF relaxation rate is dominated by the static-field distribution, and a broad relaxation rate maximum at 175 K for x=0.1 in ZF is attributed to muon diffusion and trapping. For LF≳2mT the static rate is completely decoupled, and the exponential decay is due to dynamic spin fluctuations. The temperature dependencies of the relaxation rates exhibit maxima at 215 K (x=0.05) and 175 K (x=0.1), in agreement with previous second harmonic generation and polarized neutron diffraction determinations of transition temperatures to a hidden-order state. The maxima are most likely due to critical slowing down of electronic spin fluctuations. The field dependencies of the dynamic spin fluctuation rates can be well described by the Redfield relation, from which the rms width Blocrms and correlation time τc of the fluctuating field are obtained. Values of τc are in the range of 1.5–4 ns for x=0.1 and shorter than 2 ns for x=0.05, suggesting an increase with increasing Rh concentration. Values of Blocrms are on the order of 1 mT, consistent with the polarized neutron diffraction cross section.
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