209 research outputs found

    Flow and Fracture Behaviour of Tungsten Fiber Reinforced Superalloy Composites-Effect Of Specimen Geometry

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    The influence of aspect ratio (i.e. width to height ratio) of test specimens on the flow and fracture behaviour of fiber reinforced composites is herein examined. The composite material was prepared by isostatic pressing of a Mar-M200 nickel-base superallov matrix reinforced with 40% tungsten wires. I. niaxial compression forging was performed at a constant true strain rate of 3x10^ S , with temperature as parameter. The aspect ratio (wo/ho) of test blanks was made to vary between 0.3 and 3, loading being always normal to the direction of wire alignment. It is herein established that peak flow stress values of composite material increase significantly with rising aspect ratio while severity of damage is shown to decrease. Furthermore, it is found that the fracture pattern is also influenced by specimen geometry. This may he attributed to some favourable effect of a hydrostatic compressive stress component which seeks to retard void formation and growth. Relevant practical implications are discussed

    Biochemical Evaluation of some Natural Feed Additives against Dexamethasone-induced Metabolic Alterations in Rabbits

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    Glucocorticoid therapy is limited by numerous metabolic adverse effects associated with long term exposure to excess doses. Therefore, the present study aims to determine the possible protective effects of date palm and/or Saccharomyces cerevisiae probiotics on dexamethasone-induced metabolic changes in rabbits. 25 healthy male white New Zealand rabbits were grouped into group 1 (control), group 2 (2 mg/kg bw/day dexamethasone I/M), group 3 (0.5 g/kg/day date palm flesh+2 mg/kg bw/day dexamethasone I/M), group 4 (1g/kg/day S. cerevisiae probiotic + 2 mg/kg bw/day dexamethasone I/M), group 5 (date palm flesh + S. cerevisiae probiotic + dexamethasone at the aforementioned doses). Dexamethasone injection resulted in marked increases (p≤0.05) in hepatic MDA concentration and catalase activity, as well as significant decreases in hepatic GSH concentration and body weight gain. The serum levels of glucose, lipid profile (TG, cholesterol, VLDL, LDL/HDL risk ratio), and liver function biomarkers (serum total proteins, albumin, ALT, ALP) showed significant variations (P≤0.05) between control and dexamethasone treated group. The ameliorative effect of date palm fruit and/or probiotics (S. cerevisiae) was markedly indicated by restoration of these tested parameters to near normalcy. Therefore, the co-treatment with date or S. cerevisiae could be considered of great interest as potential feed additives for reduction of the adverse metabolic effects induced by dexamethasone in rabbits

    Antioxidant Role of Vitamin C in Alleviating the Reproductive Toxicity of Lead Acetate in Male Rats

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    Environmental pollution with heavy metals represents global problem. One of these heavy metals is the lead acetate that emits from many industries such as paint, ceramics, lead containing pipes and plastics led to a manifold rise in the occurrence of free lead in biological systems and the environment. Exposure to lead acetate affects most of the body’s organs especially testes since it has a unique vascular system. Therefore, the present study aimed to evaluate the protective effect of vitamin C against lead acetate induced testicular toxicity in rats. Thirty male adult albino rats were used in this study. They were equally divided into three groups; group I "control group", group II "lead acetate treated group" and group III "lead acetate and vitamin C treated group". Administration of lead acetate (20 mg /kg body weight for 8 successive weeks) resulted in a significant decrease in serum level of testosterone. It also led to a significant increase in the testicular tissue homogenate concentration of MDA and a significant decrease in GSH concentration and catalase activity. Administration of vitamin C (20 mg/kg body weight) with lead acetate for 8 successive weeks succeeded in improving semen quality and antioxidant enzyme concentrations of testes. It can be concluded that lead acetate testicular toxicity in rats led to disturbance in serum level of the main male reproductive hormone and increased testicular contents of oxidative markers and decreased the antioxidant markers. The use of vitamin C improved these changes.  &nbsp

    STEROLS BIOACTIVITY OF RUTA GRAVEOLENS L. AND MURRAYA PANICULATA L.

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    Objective: Ruta graveolens L. (R. graveolens) and Murraya paniculata L. (M. paniculata) are medicinal plants belonging to Rutaceae family have many uses in traditional medicine. The aim of the present study was to investigate sterols bioactivity of the two Rutaceae plant leaves.Methods: Sterols of the two Rutaceae plant leaves were identified using GC/MS. The antioxidant activities of the sterols of these herbs were evaluated by three different methods; free radical scavenging using 2,2′-Azino-bis (3-ethylbenzthiazoline-6-sulfonic acid) (ABTS), 1,1-Diphenyl-2-picryl-hydrazyl (DPPH) and total antioxidant activity. The anticancer activity of the sterols was determined by MTT assay against colorectal cancer HCT116, breast cancer MCF7, liver cancer HepG2 and lung cancer A549 cell lines. Anti-inflammatory activity was evaluated using albumin denaturation assay and antiviral activities against H5N1 virus were carried out using plaque reduction assay.Results: GC/MS assay showed β-Sitosterol (36%) as the most abundant sterols of R. graveolens followed by stigmasterol (18%), while stigmasterol (25.2%) was the most abundant one of M. paniculata steroids. The anti-inflammatory potential of R. graveolens steroids was significantly higher than that of diclofenac sodium (standard drug). M. paniculata sterols have higher antiviral activity (IC50= 0.15 of µg/ml) than R. graveolens sterols (IC50= 7.8 of µg/ml). The sterols of R. graveolens showed anticancer activity against MCF7 and A549 cells with inhibition 84.3 and 81%, at 100 µg/ml respectively. While M. paniculata sterols showed 77.3% inhibition against A549 cells.Conclusion: The current study suggests that the sterols of M. paniculata have more anti-viral activity than R. graveolens sterols which showed more anticancer and anti-inflammatory activities

    Effect of Casting Conditions on the Fracture Strength of Al-5 Mg Alloy Castings

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    During the transient phase of filling a casting running system, surface turbulence can cause the entrainment of oxide films into the bulk liquid. Previous research has suggested that the entrained oxide film would have a deleterious effect on the reproducibility of the mechanical properties of Al cast alloys. In this work, the Weibull moduli for the ultimate tensile strength (UTS) and % elongation of sand cast bars produced under different casting conditions were compared as indicators of casting reliability which was expected to be a function of the oxide film content. The results showed that the use of a thin runner along with the use of filters can significantly eliminate the surface turbulence of the melt during mould filling which would lead to the avoidance of the generation and entrainment of surface oxide films and in turn produce castings with more reliable and reproducible mechanical properties compared to the castings produced using conventional running systems

    Using small-angle X-ray scattering to investigate the compaction behaviour of a granulated clay

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    The compaction behaviour of a commercial granulated clay (magnesium aluminium smectite, gMgSm) was investigated using macroscopic pressure-density measurements, X-ray diffraction (XRD), scanning electron microscopy (SEM), X-ray microtomography (XμT) and small-angle X-ray scattering (SAXS). This material was studied as a potential compaction excipient for pharmaceutical tabletting, but also as a model system demonstrating the capabilities of SAXS for investigating compaction in other situations. Bulk compaction measurements showed that the gMgSm was more difficult to compact than polymeric pharmaceutical excipients such as spheronised microcrystalline cellulose (sMCC), corresponding to harder granules. Moreover, in spite of using lubrication (magnesium stearate) on the tooling surfaces, rather high ejection forces were observed, which may cause problems during commercial tabletting, requiring further amelioration. Although the compacted gMgSm specimens were more porous, however, they still exhibited acceptable cohesive strengths, comparable to sMCC. Hence, there may be scope for using granular clay as one component of a tabletting formulation. Following principles established in previous work, SAXS revealed information concerning the intragranular structure of the gMgSm and its response to compaction. The results showed that little compression of the intragranular morphology occurred below a relative density of 0 · 6, suggesting that granule rearrangements or fragmentation were the dominant mechanisms during this stage. By contrast, granule deformation became considerably more important at higher relative density, which also coincided with a significant increase in the cohesive strength of compacted specimens. Spatially-resolved SAXS data was also used to investigate local variations in compaction behaviour within specimens of different shape. The results revealed the expected patterns of density variations within flat-faced cylindrical specimens. Significant variations in density, the magnitude of compressive strain and principal strain direction were also revealed in the vicinity of a debossed feature (a diametral notch) and within bi-convex specimens. The variations in compaction around the debossed notch, with a small region of high density below and low density along the flanks, appeared to be responsible for extensive cracking, which could also cause problems in commercial tabletting

    Attributes influencing parental decision-making to receive the Tdap vaccine to reduce the risk of pertussis transmission to their newborn – outcome of a crosssectional conjoint experiment in Spain and Italy

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    Pertussis vaccination of parents and household contacts (‘cocooning’) to protect newborn infants is an established strategy in many countries, although uptake may be low. Many aspects may influence such decision-making. We conducted a cross-sectional survey (NCT01890447) of households and other close contacts of newborns aged ≤6 months (or of expectant mothers in their last trimester) in Spain and Italy, using an adaptive discrete-choice experiment questionnaire. Aims were to assess the relative importance of attributes influencing vaccine adoption, and to estimate variation in vaccine adoption rates and the impact of cost on vaccination rates. Six hundred and fifteen participants (Spain, n = 313; Italy, n = 302) completed the survey. Of 144 available questionnaire scenarios, the most frequently selected (14% of respondents in both countries) were infant protection by household vaccination at vaccination center, recommendation by family physician and health authorities, with information available on leaflets and websites. The attribute with highest median relative importance was ‘reduction in source of infection’ in Spain (23.1%) and ‘vaccination location’ in Italy (18.8%). Differences between other attributes were low in both countries, with media attributes showing low importance. Over 80% of respondents indicated a definite or probable response to vaccine adoption (at no-cost) with estimated probability of adoption of 89–98%; applying vaccine costs (25€ per person) would reduce the probability of uptake by 7–20% in definite/probable respondents. Awareness of these determinants is helpful in informing Health Authorities and healthcare practitioners implementing a cocooning strategy for those populations where maternal immunization is not a preferred option

    Rapid evolution of A(H5N1) influenza viruses after intercontinental spread to North America

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    Highly pathogenic avian influenza A(H5N1) viruses of clade 2.3.4.4b underwent an explosive geographic expansion in 2021 among wild birds and domestic poultry across Asia, Europe, and Africa. By the end of 2021, 2.3.4.4b viruses were detected in North America, signifying further intercontinental spread. Here we show that the western movement of clade 2.3.4.4b was quickly followed by reassortment with viruses circulating in wild birds in North America, resulting in the acquisition of different combinations of ribonucleoprotein genes. These reassortant A(H5N1) viruses are genotypically and phenotypically diverse, with many causing severe disease with dramatic neurologic involvement in mammals. The proclivity of the current A(H5N1) 2.3.4.4b virus lineage to reassort and target the central nervous system warrants concerted planning to combat the spread and evolution of the virus within the continent and to mitigate the impact of a potential influenza pandemic that could originate from similar A(H5N1) reassortants

    Accelerated evolution of SARS-CoV-2 in free-ranging white-tailed deer

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    The zoonotic origin of the COVID-19 pandemic virus highlights the need to fill the vast gaps in our knowledge of SARS-CoV-2 ecology and evolution in non-human hosts. Here, we detected that SARS-CoV-2 was introduced from humans into white-tailed deer more than 30 times in Ohio, USA during November 2021-March 2022. Subsequently, deer-to-deer transmission persisted for 2–8 months, disseminating across hundreds of kilometers. Newly developed Bayesian phylogenetic methods quantified how SARS-CoV-2 evolution is not only three-times faster in white-tailed deer compared to the rate observed in humans but also driven by different mutational biases and selection pressures. The long-term effect of this accelerated evolutionary rate remains to be seen as no critical phenotypic changes were observed in our animal models using white-tailed deer origin viruses. Still, SARS-CoV-2 has transmitted in white-tailed deer populations for a relatively short duration, and the risk of future changes may have serious consequences for humans and livestock
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