Ceramic-reinforced HEA matrix composites exhibiting an excellent combination of mechanical properties.

CoCrFeNi is a well-studied face centered cubic (fcc) high entropy alloy (HEA) that exhibits excellent ductility but only limited strength. The present study focusses on improving the strength-ductility balance of this HEA by addition of varying amounts of SiC using an arc melting route. Chromium present in the base HEA is found to result in decomposition of SiC during melting. Consequently, interaction of free carbon with chromium results in the in-situ formation of chromium carbide, while free silicon remains in solution in the base HEA and/or interacts with the constituent elements of the base HEA to form silicides. The changes in microstructural phases with increasing amount of SiC are found to follow the sequence: fcc → fcc + eutectic → fcc + chromium carbide platelets → fcc + chromium carbide platelets + silicides → fcc + chromium carbide platelets + silicides + graphite globules/flakes. In comparison to both conventional and high entropy alloys, the resulting composites were found to exhibit a very wide range of mechanical properties (yield strength from 277 MPa with more than 60% elongation to 2522 MPa with 6% elongation). Some of the developed high entropy composites showed an outstanding combination of mechanical properties (yield strength 1200 MPa with 37% elongation) and occupied previously unattainable regions in a yield strength versus elongation map. In addition to their significant elongation, the hardness and yield strength of the HEA composites are found to lie in the same range as those of bulk metallic glasses. It is therefore believed that development of high entropy composites can help in obtaining outstanding combinations of mechanical properties for advanced structural applications.

Microstructural evolution and mechanical characterization of a WC-reinforced CoCrFeNi HEA matrix composite.

High entropy alloys (HEAs) are a relatively new class of material that have shown the potential to exhibit excellent combinations of mechanical properties. Various microstructural modifications have been explored to further enhance their mechanical properties for use in demanding structural applications. The main focus of the present work is an investigation of the effect of adding varying amounts of hard ceramic material (WC) to a tough HEA matrix (CoCrFeNi) by arc melting under an argon atmosphere, including microstructural changes, and evaluation of the WC additions on mechanical properties. X-ray diffraction analysis of the HEA-WC composites showed the presence of both fcc and carbide phases. Scanning electron microscope investigations, including energy dispersive spectroscopy, reveal that chromium diffuses from the matrix and interacts with WC to form an alloyed carbide phase. The amount of alloyed carbide was found to increase with increasing amount of WC addition to the HEA matrix. Mechanical characterization revealed that hardness and yield strength of the HEA-WC composites increase with increasing amount of the carbide phase in the matrix. The hardness of HEA-20wt.% WC sample was found to be as high as 3.3 times (593 HV) the hardness of the base HEA (180 HV), while the yield strength increased from 278 MPa for the base HEA to 1098 MPa for the CoCrFeNi-20 wt.% WC composite. The investigated composites also showed excellent values of ductility (~ 50% strain for CoCrFeNi-10 wt% WC and ~ 20% strain for CoCrFeNi-20 wt% WC). It is therefore believed that ceramic-reinforced high entropy matrix composites have the potential to provide outstanding combinations of mechanical properties for demanding structural applications.

Inhibition of soluble epoxide hydrolase offers protection against fructose-induced diabetes and related metabolic complications in rats.

Stabilization of epoxyeicosatrienoic acids (EETs) levels via soluble epoxide hydrolase (sEH) deletion or its pharmacological inhibition have been shown to have beneficial effects on inflammation, ischemia, hypertension and diabetes. Owing to the diverse role of EETs, current study was designed to evaluate the therapeutic potential of 1-trifluoromethoxyphenyl-3-(1-propionylpiperidine-4-yl) urea (TPPU), a novel sEHI against fructose-induced diabetes and related complications in rats. Sprague-Dawley rats (200 - 230 g) were divided into four different groups, each containing 10 animals. One group served as a normal control and received standard diet and drinking water. The second group served as a diseased control and received standard diet, 25% fructose in drinking water and was treated with vehicle only. The third and fourth groups received standard diet, 25% fructose in drinking water and TPPU (2 mg/kg) or metformin (150 mg/kg), respectively. All treatments were given orally for 12 weeks. At the end of the study, blood samples were collected to measure serum insulin levels and other biochemical parameters. Animals were dissected to collect tissue specimens for histological and immunohistochemistry analysis. Animals fed on fructose and treated with vehicle demonstrated elevated blood insulin and glucose levels as well as high levels (P < 0.001) of triglycerides (TGs), cholesterol, low-density lipoprotein (LDL) and homeostatic model assessment of insulin resistance (HOMA-IR) compared to naive rats. Similarly, the levels of alkaline phosphatase (ALP), alanine aminotransferase (ALT), urea and uric acid were significantly (P < 0.001) increased in vehicle treated fructose fed animals. TPPU (2 mg/kg p.o.) and simultaneously fed on fructose for 12 weeks substantially decreased HOMA-IR levels, lowered blood glucose, serum cholesterol, LDLs and TGs) while high-density lipoproteins (HDL) levels were increased compared to untreated animals. Metformin, a standard reference drug showed similar results. Microscopic studies of liver and pancreatic sections of TPPU treated animals showed marked improvement in cellular architecture compared to untreated animals. Current study demonstrated profound therapeutic potential of TPPU against fructose induced-diabetes and related metabolic complications which was evident by its attenuating effect fructose-induced hyperglycemia, hyperlipidemia and impaired renal and hepatic serum markers.

Coercivity Increase of the Recycled HDDR Nd-Fe-B Powders Doped with DyF3 and Processed via Spark Plasma Sintering & the Effect of Thermal Treatments.

The magnetic properties of the recycled hydrogenation disproportionation desorption recombination (HDDR) Nd-Fe-B powder, doped with a low weight fraction of DyF3 nanoparticles, were investigated. Spark plasma sintering (SPS) was used to consolidate the recycled Nd-Fe-B powder blends containing 1, 2, and 5 wt.% of DyF3 grounded powder. Different post-SPS sintering thermal treatment conditions (600, 750, and 900 °C), for a varying amount of time, were studied in view of optimizing the magnetic properties and developing characteristic core-shell microstructure in the HDDR powder. As received, recycled HDDR powder has coercivity (HCi) of 830 kA/m, and as optimally as SPS magnets reach 1160 kA/m, after the thermal treatment. With only 1-2 wt.% blended DyF3, the HCi peaked to 1407 kA/m with the thermal treatment at 750 °C for 1 h. The obtained HCi values of the blend magnet is ~69.5% higher than the starting recycled HDDR powder and 17.5% higher than the SPS processed magnet annealed at 750 °C for 1 h. Prolonging the thermal treatment time to 6 h and temperature conditions above 900 °C was detrimental to the magnetic properties. About ~2 wt.% DyF3 dopant was suitable to develop a uniform core-shell microstructure in the HDDR Nd-Fe-B powder. The Nd-rich phase in the HDDR powder has a slightly different and fluorine rich composition i.e., Nd-O-F2 than in the one reported in sintered magnets (Nd-O-F). The composition of reaction zone-phases after the thermal treatment and Dy diffusion was DyF4, which is more abundant in 5 wt.% doped samples. Further doping above 2 wt.% DyF3 is ineffective in augmenting the coercivity of the recycled HDDR powder, due to the decomposition of the shell structure and formation of non-ferromagnetic rare earth-based complex intermetallic compounds. The DyF3 doping is a very effective single step route in a controlled coercivity improvement of the recycled HDDR Nd-Fe-B powder from the end of life magnetic products.

Effect of EDTA as Chelating Agent in Extender on the Post Thaw Quality of Buffalo Bull Spermatozoa.

BACKGROUND: Spermatozoa are prone to mechanical and biochemical stresses upon freezing. The influx of Ca++ causes early capacitation and production of reactive oxygen species. OBJECTIVE: To evaluate the effect of ethylenediaminetetraacetic acid (EDTA) as a calcium chelator in a semen extender. MATERIALS AND METHODS: The effect of EDTA concentrations (0%, 0.1%, 0.2% and 0.3%) on the post thaw quality of buffalo bull spermatozoa were studied. RESULTS: The extender with 0.2% EDTA improved significantly visual motility, progressive motility and plasma membrane integrity. Sperm kinematics, such as beat cross frequency (BCF), curved line velocity (VCL), straight line velocity (VSL) and average path velocity (VAP), were higher in the extender with 0.2% EDTA. EDTA at 0.2% improves semen parameters (visual motility, supra vital plasma membrane integrity, chromatin integrity and percentage viable spermatozoa with intact acrosome. CONCLUSION: The EDTA supplementation in a semen extender improves the post-thaw quality of Nili-Ravi buffalo bull semen.

Plasmonic Spherical Heterodimers: Reversal of Optical Binding Force Based on the Forced Breaking of Symmetry.

The stimulating connection between the reversal of near-field plasmonic binding force and the role of symmetry-breaking has not been investigated comprehensively in the literature. In this work, the symmetry of spherical plasmonic heterodimer-setup is broken forcefully by shining the light from a specific side of the set-up instead of impinging it from the top. We demonstrate that for the forced symmetry-broken spherical heterodimer-configurations: reversal of lateral and longitudinal near-field binding force follow completely distinct mechanisms. Interestingly, the reversal of longitudinal binding force can be easily controlled either by changing the direction of light propagation or by varying their relative orientation. This simple process of controlling binding force may open a novel generic way of optical manipulation even with the heterodimers of other shapes. Though it is commonly believed that the reversal of near-field plasmonic binding force should naturally occur for the presence of bonding and anti-bonding modes or at least for the Fano resonance (and plasmonic forces mostly arise from the surface force), our study based on Lorentz-force dynamics suggests notably opposite proposals for the aforementioned cases. Observations in this article can be very useful for improved sensors, particle clustering and aggregation.

Comparative efficacy of G6G and Ovsynch protocols on synchronization and pregnancy rate in Nili-Ravi buffalo.

The aim of this work was to evaluate the efficacy of G6G and Ovsynch protocols on synchronization and pregnancy rate in Nili-Ravi buffalo. For this, a total of fifty buffalo were assigned into two treatment groups: (1) G6G (n=25) and (2) Ovsynch (n=25). The blood samples were collected from all the treated buffalo on day (D) 7 (PGF2α injection of Ovsynch) to measure the progesterone (P4). All the buffalo were fixed time inseminated (FTAI) following last GnRH of Ovsynch. Ultrasonography was performed for follicular, corpus luteum (CL) dynamics and pregnancy diagnosis. The results revealed that synchronization rate and response to final PGF2α were significantly (P<0.05) higher in G6G compared to Ovsynch. The ovulation to first GnRH of Ovsynch was higher (P<0.05) in G6G (84%) than Ovsynch (56%). The mean dominant follicle size following last GnRH of Ovsynch showed significantly larger diameter in G6G (11.7±0.2mm) compared to Ovsynch (10.9±0.2mm). Moreover, the higher (P<0.05) P4 concentration was observed in G6G than Ovsynch. The presence of double CL on D 7 was higher (P<0.05) in G6G (64%) than Ovsynch (24%) group. The pregnancy rate (P=0.08) tended to be greater in G6G compared to Ovsynch. In conclusion, G6G treatment showed better ovulatory and luteolytic response to first GnRH and PGF2α compared to Ovsynch treatment. Moreover, the addition of GnRH and PGF2α prior to Ovsynch is helpful to improve synchronization application of Ovsynch protocol in Nili-Ravi buffalo.

Visible-Frequency Metasurface for Structuring and Spatially Multiplexing Optical Vortices.

A multifocus optical vortex metalens, with enhanced signal-to-noise ratio, is presented, which focuses three longitudinal vortices with distinct topological charges at different focal planes. The design largely extends the flexibility of tuning the number of vortices and their focal positions for circularly polarized light in a compact device, which provides the convenience for the nanomanipulation of optical vortices.

Switchable Ultrathin Quarter-wave Plate in Terahertz Using Active Phase-change Metasurface.

Metamaterials open up various exotic means to control electromagnetic waves and among them polarization manipulations with metamaterials have attracted intense attention. As of today, static responses of resonators in metamaterials lead to a narrow-band and single-function operation. Extension of the working frequency relies on multilayer metamaterials or different unit cells, which hinder the development of ultra-compact optical systems. In this work, we demonstrate a switchable ultrathin terahertz quarter-wave plate by hybridizing a phase change material, vanadium dioxide (VO2), with a metasurface. Before the phase transition, VO2 behaves as a semiconductor and the metasurface operates as a quarter-wave plate at 0.468 THz. After the transition to metal phase, the quarter-wave plate operates at 0.502 THz. At the corresponding operating frequencies, the metasurface converts a linearly polarized light into a circularly polarized light. This work reveals the feasibility to realize tunable/active and extremely low-profile polarization manipulation devices in the terahertz regime through the incorporation of such phase-change metasurfaces, enabling novel applications of ultrathin terahertz meta-devices.

Antibiotic de-escalation in bacteremic urinary tract infections: potential opportunities and effect on outcome.

PURPOSE: The aim of this study was to examine the safety and efficacy of antibiotic de-escalation in patients admitted with bacteremic urinary tract infection (UTI). METHODS: A retrospective chart review of patients admitted to a community-hospital in West Texas with bacteremic UTI during the year 2008. Antibiotic de-escalation was defined as changing the intravenous empiric antibiotic regimen to a culture-directed single agent, given intravenously or orally, with a narrower spectrum than the original empiric regimen. RESULTS: Ninety-seven patients were admitted with bacteremic UTI. Thirty-two patients were not eligible for de-escalation. Among the 65 patients who were eligible for de-escalation, the treating physicians failed to de-escalate antibiotics in 31 cases (47.7%). Fluoroquinolones' resistance, bacteria other than Escherichia coli and discharge to long-term care facilities predicted failure to de-escalate antibiotics. On multivariate analysis, discharge to long-term care facility was the only risk factor that predicted failure to de-escalate antibiotics. The difference between mean hospital length of stay and mortality between the above two groups was not statistically significant. CONCLUSION: Antibiotic de-escalation is under-recognized and sporadically practiced. In patients admitted with bacteremic UTI, empiric antibiotic regimen can be changed to a culture-directed single antibiotic without an increase in hospital length of stay or patients' mortality.

In situ microbial treatment of landfill leachate using aerated lagoons.

The aim of this study was to assess the efficiency of leachate treatment by microbial oxidation in four connected on-site aerated lagoons at a landfill site. The landfill site was found to be in an ageing methanogenic state, producing leachate with relatively low COD (mean value 1740 mg l(-1)) and relatively high ammonium concentrations (mean value 1241 mg l(-1)). Removal of COD averaged 75%, with retention times varying from 11 to 254 days. Overall 80% of the N load was removed within the plant, some by volatilisation of ammonium. Microbial community profiling of the water from each lagoon showed a divergent community profile, presumably a reflection of the nutrient status in each lagoon. In municipal solid waste landfills under similar conditions, leachate treatment through a facultative aerobic system in which sequential aerobic and anaerobic microbial oxidations occurred can readily be achieved using a simple two-lagoon system, suggesting this technology can be economic to install and simple to run.

The Heartfile Lodhran CVD prevention project--end of project evaluation

Mainstream preventive interventions often fail to reach poor populations with a high risk of cardiovascular diseases (CVDs) in Pakistan. A community-based CVD primary prevention project aimed at developing approaches to reduce risk factors in such populations was established by Heartfile in collaboration with the National Rural Support Program in the district of Lodhran. The project implemented a range of activities integrated with existing social and health service mechanisms during a three year intervention period 2000/01-03/04. These were targeted in 4 key settings: community health education, mass media interventions, training of health professionals and health education through Lady Health Workers. The project received support from the Department for International Development, U.K. At the community level, a pre-test-post-test quasi-experimental design was used for examining project outcomes related to the community component of the intervention. Pre and post-intervention (training) evaluations were conducted involving all health care providers in randomly selected workshops in order to determine baseline levels of knowledge and the impact of training on knowledge level. In order to assess practices of physician and non-physician health care providers patient interviews, with control comparisons were conducted at each health care facility. Significant positive changes were observed in knowledge levels at a community level in the district of intervention compared with baseline knowledge levels particularly in relation to a heart healthy diet, beneficial level of physical activity, the causes of high blood pressure and heart attack and the effects of high blood pressure and active and passive smoking on health. Significant changes in behaviors at a practice level were not shown in the district of intervention. However the project played a critical role in spurring national action for the prevention and control of non-communicable diseases and introducing sustainable public health interventions for poor communities in Pakistan. (AU)