Performance of Microchannel Heat Sink Made of Silicon Material with the Two-Sided Wedge

New designs of the microchannel with a two-sided wedge shape at the base were studied numerically. Five different wedge angles ranging from 3° to 15° were incorporated into the microchannel design. Simulation of this novel microchannel was carried out using Computational Fluid Dynamics (CFD). Three-dimensional models of the microchannel heat sink were created, discretized, and based on Navier–Stokes and energy equations; laminar numerical solutions were obtained for heat transfer and pressure drop. Flow characteristics of water as coolant in a microchannel were studied. It was observed that numerical results are in good agreement with experimental results. It was found that the Nusselt number and friction factor are significantly varied with the increase in Reynolds number. The Nusselt number varies in the following ranges of 5.963–8.521, 5.986–8.550, 6.009–8.568, 6.040–8.609, and 6.078–8.644 at 3°, 6°, 9°, 12°, and 15°, respectively. The microchannel with a wedge angle of 15° was found to be better in terms of Nusselt number and thermo-hydraulic performance. The enhancement in the Nusselt number is found as 1.017–1.036 for a wedge angle of 15°; however, friction factors do not show the perceptible values at distinct values of wedge angle. Moreover, the thermo-hydraulic performance parameters (THPP) were evaluated and found to be maximum in the range of 1.027–1.045 for a wedge angle of 15°. However, minimum THPP was found in the range of 1.005–1.0185 for a wedge angle of 3°.     

Hemagglutinin Subtype Specificity and Mechanisms of Highly Pathogenic Avian Influenza Virus Genesis

Highly Pathogenic Avian Influenza Viruses (HPAIVs) arise from low pathogenic precursors following spillover from wild waterfowl into poultry populations. The main virulence determinant of HPAIVs is the presence of a multi-basic cleavage site (MBCS) in the hemagglutinin (HA) glycoprotein. The MBCS allows for HA cleavage and, consequently, activation by ubiquitous proteases, which results in systemic dissemination in terrestrial poultry. Since 1959, 51 independent MBCS acquisition events have been documented, virtually all in HA from the H5 and H7 subtypes. In the present article, data from natural LPAIV to HPAIV conversions and experimental in vitro and in vivo studies were reviewed in order to compile recent advances in understanding HA cleavage efficiency, protease usage, and MBCS acquisition mechanisms. Finally, recent hypotheses that might explain the unique predisposition of the H5 and H7 HA sequences to obtain an MBCS in nature are discussed.     

Insights into Genetic Characteristics and Virological Features of Endemic Avian Influenza A (H9N2) Viruses in Egypt from 2017–2021

From 2010 to 2013, genotype I avian influenza A(H9N2) viruses of the G1-lineage were isolated from several poultry species in Egypt. In 2014, novel reassortant H9N2 viruses were detected in pigeons designated as genotype II. To monitor the subsequent genetic evolution of Egyptian A(H9N2) viruses, we characterized the full genomes of 173 viruses isolated through active surveillance from 2017 to 2022. In addition, we compared the virological characteristics and pathogenicity of representative viruses. Phylogenetic analysis of the HA indicated that all studied sequences from 2017–2021 were grouped into G1-like H9N2 viruses previously detected in Egypt. Phylogenetic analysis indicated that the Egyptian A(H9N2) viruses had undergone further reassortment, inheriting four genes (PB2, PB1, PA, NS) from genotype II, with their remaining segments deriving from genotype I viruses (these viruses designated as genotype III). Studying the virological features of the two most dominant genotypes (I and III) of Egyptian H9N2 viruses in vitro and in vivo indicated that both replicated well in mammalian cells, but did not show any clinical signs in chickens, ducks, and mice. Monitoring avian influenza viruses through surveillance programs and understanding the genetic and antigenic characteristics of circulating H9N2 viruses are essential for risk assessment and influenza pandemic preparedness.     

Assessment of the Impact of Ionizing Radiation Absorption on the Structural,Mechanical and Biophysical Properties of Textiles Used in Multilayer Space Suit

The article presents research on ergonomics, biophysical comfort and safety of protective clothing. The resistance of the structural, thermal and mechanical properties of five fabrics (CBXS400, GG200T, Twaron CT736, Dyneema HB26 and T1790C), differing in geometry and raw material composition used in space suits, to dangerous ionizing radiation (β and γ) occurring in space was tested. For both types of radiation, four identical one-time doses in the range of 25–100 kGy were used. The effect of the applied absorbed doses of β and γ radiation on the parameters of textiles influencing ergonomics and safety of the cosmonaut’s work was verified by structural tests (micro-computed tomography and optical microcopy), thermal resistance tests (sweating guarded-hotplate) and strength tests (tensile testing machine). Experimental studies of thermal properties are supplemented with heat transport simulations using the finite volume method performed with 3D models of real textiles. The greatest reduction of thermal resistance for Twaron CT736 (−0.0667 m²·°C·W⁻¹ for 100 kGy of β-radiation) and Dyneema HB26 (−0.0347 m²·°C·W⁻¹ for 50 kGy of β-radiation) is observed. Strength tests have shown that all tested textiles are resistant to both types of radiation. Three textiles were selected to create a three-layer assembly with potential application in a cosmonaut’s glove (Extravehicular Activity—EVA).     

热乙醇法提取猪血白蛋白工艺改良的探讨

目的介绍运用热乙醇法提取高纯度猪血白蛋白的改良工艺流程。方法采用热乙醇法,在合适的恒温时间和pH值的条件下,分离提纯猪血清白蛋白。结果猪血白蛋白的纯度〉97％,回收率〉80％。检测结果显示,其理化指标均符合《中国生物制品规程2000年版》的要求,适合扩大到中试生产。结论该法与低温乙醇法、利凡诺法和盐析法相比,具有工艺简单、成本低、纯度和回收率高的特点。     

加热对人肝癌细胞-7721生长规律的影响

目的观察加热对人肝癌细胞-7721生长规律的影响.方法应用人肝癌细胞株-7721(以下简称7721细胞),常规法培养;采用水浴加温法(42.5℃)热疗和热化疗处理细胞后,继续常规法培养;计数1-7d的细胞数,绘制生长曲线、计算细胞倍增时间;观察细胞的电镜下表现.结果加热处理的细胞倍增时间较未处理细胞明显延长,加热处理的细胞发生空泡变性,热化疗处理的细胞胞膜破坏严重、胞浆细胞器外溢明显.结论加热处理可以明显抑制人肝癌细胞-7721的生长能力,原因是加热引起该细胞的某些细胞器变性.     

国医大师禤国维教授滋阴清热法治疗痤疮理论探讨

介绍了国医大师禤国维教授运用滋阴清热法治疗阴虚火旺型痤疮的临床经验。禤老认为现代人患痤疮,其根本原因在于素体肾阴不足,肾之阴阳平衡失调和天癸相火过旺,导致肺胃血热,上熏面部而发痤疮。可采用滋肾泻火、清肺解毒的治疗原则,以二至丸合知柏地黄丸加减组成的消痤汤加减治疗。      

薄荷油湿热敷治疗维持性血液透析患者便秘的疗效观察

目的：探讨薄荷油腹部湿热敷对维持性血液透析患者便秘的疗效。方法将60例维持性血液透析便秘患者随机分为观察组与对照组各30例,观察组患者采用薄荷油腹部湿热敷,对照组给予番泻叶3~6 g泡水顿服,疗程均为2周。观察2组患者的疗效及排便时患者的反应。结果观察组总有效率明显高于对照组,2组比较差异有统计学意义（P〈0.05）。结论薄荷油腹部湿热敷操作简单,无副作用,不仅可以使维持性血液透析患者保持大便通畅,而且可以减少因便秘引起的不适和并发症,进而提高患者的生活质量。     

金属雕塑的历史沿革

人类进入文明社会之际 ,硬度远远高于陶器的青铜器 ,有力地促进了人类的文明进程。铁器的出现和广泛使用 ,极大地促进了社会生产力的发展 ,导致封建社会的建立和奴隶制社会的崩溃。大工业革命的历史巨轮隆隆行驶在用新的金属材质“钢”制成的轨迹上 ,崭新的历史纪元伴随日新月异的现代科学技术的急速发展 ,不断为人类拓展着新的生活空间 ,金属在人类历史上所起的重要作用 ,超越了艺术的领域 ,甚至成为人类社会文明进步的一种标识。     

Study on the Design,Preparation, and Performance Evaluation of Heat-Resistant Interlayer-Polyimide-Resin-Based Neutron-Shielding Materials

Polymers have an excellent effect in terms of moderating fast neutrons with rich hydrogen and carbon, which plays an indispensable role in shielding devices. As the shielding of neutrons is typically accompanied by the generation of γ-rays, shielding materials are developed from monomers to multi-component composites, multi-layer structures, and even complex structures. In this paper, based on the typical multilayer structure, the integrated design of the shield component structure and the preparation and performance evaluation of the materials is carried out based on the design sample of the heat-resistant lightweight polymer-based interlayer. Through calculation, the component structure of the polymer-based materials and the three-layer thickness of the shield are obtained. The mass fraction of boron carbide accounts for 11% of the polymer-based material. Since the polymer-based material is the weak link of heat resistance of the multilayer shield, in terms of material selection and modification, the B₄C/TiO₂/polyimide molded plate was prepared by the hot-pressing method, and characterization analysis was conducted for its structure and properties. The results show that the ball milling method can mix the materials well and realize the uniform dispersion of B₄C and TiO₂ in the polyimide matrices. Boron carbide particles are evenly distributed in the material. Except for Ti, the other elemental content of the selected areas for mapping is in good agreement with the theoretical values of the elemental content of the system. The prepared B₄C/TiO₂/polyimide molded plate presents excellent thermal properties, and its glass transition temperature and initial thermal decomposition temperature are as high as 363.6 °C and 572.8 °C, respectively. In addition, the molded plate has good toughness performs well in compression resistance, shock resistance, and thermal aging resistance, which allows it to be used for a long time under 300 °C. Finally, the prepared materials are tested experimentally on an americium beryllium neutron source. The experimental results match the simulation results well.