Strain Softening Induced by High Pressure Torsion in Copper Alloys

Three kinds of Cu-Al alloys and a pure Cu sample with different stacking fault energies (SFEs) are deformed using room temperature rolling (RR) and high pressure torsion (HPT), respectively. The microstructure is analysed by means of transaction electron microscopy and X-ray diffraction. It is found that HIPT is more feasible to obtain nanocrystals and profuse twins. Tailoring the SFE can promote sample strength without sacrificing the ductility of the Cu alloys. The tensile properties of samples processed by HPT and RR are compared. It is discovered that the HPT process leads to the strain softening phenomenon in samples with relatively high SFE. The excellent mechanical properties can be obtained in samples deformed by HPT with a SFE of 6 mJ/m(2), in which strain softening was restrained and strain hardening played a dominant role in the deformation process. The relationship between tensile properties and microstructures of the deformed metals is also investigated.110Ysciescopu

Electrical Conductivity Studies on Individual Conjugated Polymer Nanowires: Two-Probe and Four-Probe Results

<p>Abstract</p> <p>Two- and four-probe electrical measurements on individual conjugated polymer nanowires with different diameters ranging from 20 to 190 nm have been performed to study their conductivity and nanocontact resistance. The two-probe results reveal that all the measured polymer nanowires with different diameters are semiconducting. However, the four-probe results show that the measured polymer nanowires with diameters of 190, 95&#8211;100, 35&#8211;40 and 20&#8211;25 nm are lying in the insulating, critical, metallic and insulting regimes of metal&#8211;insulator transition, respectively. The 35&#8211;40 nm nanowire displays a metal&#8211;insulator transition at around 35 K. In addition, it was found that the nanocontact resistance is in the magnitude of 10⁴&#937; at room temperature, which is comparable to the intrinsic resistance of the nanowires. These results demonstrate that four-probe electrical measurement is necessary to explore the intrinsic electronic transport properties of isolated nanowires, especially in the case of metallic nanowires, because the metallic nature of the measured nanowires may be coved by the nanocontact resistance that cannot be excluded by a two-probe technique.</p

Confinement-induced phonon softening and hardening in Sb2Te3 thin films

Scaling effects in Sesqui-chalcogenides are of major interest to understand and optimize their performance in heavily scaled applications, including topological insulators and phase-change devices. A combined experimental and theoretical study is presented for molecular beam epitaxy-grown films of antimony-telluride (Sb2Te3). Structural,vibrational, optical, and bonding properties upon varying confinement are studied for thicknesses ranging from 1.3 to 56 nm. In ultrathin films, the low-frequency coherent phonons of A(1g)(1) symmetry are softened compared to the bulk (64.5 cm(-1) at 1.3 nm compared to 68 cm(-1) at 55.8 nm). A concomitant increase of the high-frequency A(1g)(2) Raman mode is seen. X-ray diffraction analyses unravel an accompanying out of plane stretch by 5%, mainly stemming from an increase in the Te-Te gap. This conclusion is supported by density functional theory slab models, which reveal a significant dependency of chemical bonding on film thickness. Changes in atomic arrangement, vibrational frequencies, and bonding extend over a thickness range much larger than observed for other material classes. The finding of these unexpectedly pronounced thickness-dependent effects in quasi-2D material Sb2Te3 allows tuning of the film properties with thickness. The results are discussed in the context of a novel bond-type, characterized by a competition between electron localization and delocalization

Effect of dietary arginine supplementation on reproductive performance of mice with porcine circovirus type 2 infection

The objective of this study was to investigate whether supplemental dietary arginine increases reproductive performance in mice infected with porcine circovirus type2 (PCV2). A total of 50KM female mice were allotted randomly to the arginine group (0.6% arginine + gestation diet) and control group (1.22% alanine + gestation diet). All the mice began to mate after 14 days of treatment with our prepared feed and challenged with PCV2 at the dose of 100 TCID50 (50% tissue culture infection dose, TCID50) after 7 days of pregnancy. Abortion rate, litter number, litter birth weight, the daily weight gain in the first 7 days and survival rate in the first 2 weeks of the neonates were calculated. The serum progesterone, estrogen, nitric oxide and superoxide dismutase (SOD) activity and total antioxidant capacity (T-AOC) on the 14th day of pregnancy were measured. Arginine supplementation decreased the abortion rate of pregnant mice and mortality of neonates caused by PCV2 infection. Further, litter number, litter birth weight and the daily weight gain of neonates increased in the arginine group compared to the control group. Arginine supplementation increased significantly the serum progesterone (P < 0.01) and nitric oxide levels (P < 0.05), but had little effect on the serum estrogen level. SOD activity and T-AOC in the arginine group were significantly higher (P < 0.01) than the control group. In conclusion, arginine supplementation partially reversed the reproductive failure in mice caused by PCV2 infection

R-process enrichment from a single event in an ancient dwarf galaxy

Elements heavier than zinc are synthesized through the (r)apid and (s)low neutron-capture processes. The main site of production of the r-process elements (such as europium) has been debated for nearly 60 years. Initial studies of chemical abundance trends in old Milky Way halo stars suggested continual r-process production, in sites like core-collapse supernovae. But evidence from the local Universe favors r-process production mainly during rare events, such as neutron star mergers. The appearance of a europium abundance plateau in some dwarf spheroidal galaxies has been suggested as evidence for rare r-process enrichment in the early Universe, but only under the assumption of no gas accretion into the dwarf galaxies. Cosmologically motivated gas accretion favors continual r-process enrichment in these systems. Furthermore, the universal r-process pattern has not been cleanly identified in dwarf spheroidals. The smaller, chemically simpler, and more ancient ultra-faint dwarf galaxies assembled shortly after the first stars formed, and are ideal systems with which to study nucleosynthesis events such as the r-process. Reticulum II is one such galaxy. The abundances of non-neutron-capture elements in this galaxy (and others like it) are similar to those of other old stars. Here, we report that seven of nine stars in Reticulum II observed with high-resolution spectroscopy show strong enhancements in heavy neutron-capture elements, with abundances that follow the universal r-process pattern above barium. The enhancement in this "r-process galaxy" is 2-3 orders of magnitude higher than that detected in any other ultra-faint dwarf galaxy. This implies that a single rare event produced the r-process material in Reticulum II. The r-process yield and event rate are incompatible with ordinary core-collapse supernovae, but consistent with other possible sites, such as neutron star mergers.Comment: Published in Nature, 21 Mar 2016: http://dx.doi.org/10.1038/nature1742

Magnetoelectric interaction and transport behaviours in magnetic nanocomposite thermoelectric materials

How to suppress the performance deterioration of thermoelectric materials in the intrinsic excitation region remains a key challenge. The magnetic transition of permanent magnet nanoparticles from ferromagnetism to paramagnetism provides an effective approach to finding the solution to this challenge. Here, we have designed and prepared magnetic nanocomposite thermoelectric materials consisting of BaFe12O19 nanoparticles and Ba0.3In0.3Co4Sb12 matrix. It was found that the electrical transport behaviours of the nanocomposites are controlled by the magnetic transition of BaFe12O19 nanoparticles from ferromagnetism to paramagnetism. BaFe12O19 nanoparticles trap electrons below the Curie temperature (TC) and release the trapped electrons above the TC, playing an ‘electron repository’ role in maintaining high figure of merit ZT. BaFe12O19 nanoparticles produce two types of magnetoelectric effect—electron spiral motion and magnon-drag thermopower—as well as enhancing phonon scattering. Our work demonstrates that the performance deterioration of thermoelectric materials in the intrinsic excitation region can be suppressed through the magnetic transition of permanent magnet nanoparticles

Improving "color rendering" of LED lighting for the growth of lettuce

Light plays a vital role on the growth and development of plant. On the base of white light with high color rendering to the benefit of human survival and life, we proposed to improve “color rendering” of LED lighting for accelerating the growth of lettuce. Seven spectral LED lights were adopted to irradiate the lettuces under 150 μmol·m−2·s−1 for a 16 hd−1 photoperiod. The leaf area and number profiles, plant biomass, and photosynthetic rate under the as-prepared LED light treatments were investigated. We let the absorption spectrum of fresh leaf be the emission spectrum of ideal light and then evaluate the “color rendering” of as-prepared LED lights by the Pearson product-moment correlation coefficient and CIE chromaticity coordinates. Under the irradiation of red-yellow-blue light with high correlation coefficient of 0.587, the dry weights and leaf growth rate are 2-3 times as high as the sharp red-blue light. The optimized LED light for lettuce growth can be presumed to be limited to the angle (about 75°) between the vectors passed through the ideal light in the CIE chromaticity coordinates. These findings open up a new idea to assess and find the optimized LED light for plant growth

Non-solvolytic synthesis of aqueous soluble TiO2 nanoparticles and real-time dynamic measurements of the nanoparticle formation.

Highly aqueously dispersible (soluble) TiO2 nanoparticles are usually synthesized by a solution-based sol-gel (solvolysis/condensation) process, and no direct precipitation of titania has been reported. This paper proposes a new approach to synthesize stable TiO2 nanoparticles by a non-solvolytic method - direct liquid phase precipitation at room temperature. Ligand-capped TiO2 nanoparticles are more readily solubilized compared to uncapped TiO2 nanoparticles, and these capped materials show distinct optical absorbance/emission behaviors. The influence of ligands, way of reactant feeding, and post-treatment on the shape, size, crystalline structure, and surface chemistry of the TiO2 nanoparticles has been thoroughly investigated by the combined use of X-ray diffraction, transmission electron microscopy, UV-visible (UV-vis) spectroscopy, and photoluminescence (PL). It is found that all above variables have significant effects on the size, shape, and dispersivity of the final TiO2 nanoparticles. For the first time, real-time UV-vis spectroscopy and PL are used to dynamically detect the formation and growth of TiO2 nanoparticles in solution. These real-time measurements show that the precipitation process begins to nucleate after an initial inhibition period of about 1 h, thereafter a particle growth occurs and reaches the maximum point after 2 h. The synthesis reaction is essentially completed after 4 h.RIGHTS : This article is licensed under the BioMed Central licence at http://www.biomedcentral.com/about/license which is similar to the 'Creative Commons Attribution Licence'. In brief you may : copy, distribute, and display the work; make derivative works; or make commercial use of the work - under the following conditions: the original author must be given credit; for any reuse or distribution, it must be made clear to others what the license terms of this work are

Controlled Growth of Carbon Spheres Through the Mg-Reduction Route

Hollow spheres, hollow capsules and solid spheres of carbon were selectively synthesized by Mg-reduction of hexachlorobutadiene at appropriate reaction conditions. X-ray powder diffraction and Raman spectra reveal that the as-prepared materials have a well-ordered structure. A possible formation mechanism has been proposed

Biophysical Assessment of Single Cell Cytotoxicity: Diesel Exhaust Particle-Treated Human Aortic Endothelial Cells

Exposure to diesel exhaust particles (DEPs), a major source of traffic-related air pollution, has become a serious health concern due to its adverse influences on human health including cardiovascular and respiratory disorders. To elucidate the relationship between biophysical properties (cell topography, cytoskeleton organizations, and cell mechanics) and functions of endothelial cells exposed to DEPs, atomic force microscope (AFM) was applied to analyze the toxic effects of DEPs on a model cell line from human aortic endothelial cells (HAECs). Fluorescence microscopy and flow cytometry were also applied to further explore DEP-induced cytotoxicity in HAECs. Results revealed that DEPs could negatively impair cell viability and alter membrane nanostructures and cytoskeleton components in a dosage- and a time-dependent manner; and analyses suggested that DEPs-induced hyperpolarization in HAECs appeared in a time-dependent manner, implying DEP treatment would lead to vasodilation, which could be supported by down-regulation of cell biophysical properties (e.g., cell elasticity). These findings are consistent with the conclusion that DEP exposure triggers important biochemical and biophysical changes that would negatively impact the pathological development of cardiovascular diseases. For example, DEP intervention would be one cause of vasodilation, which will expand understanding of biophysical aspects associated with DEP cytotoxicity in HAECs