Effect of Silicon Nitride and Graphene Nanoplatelets on the Properties of Aluminum Metal Matrix Composites

This research work aims at investigating the influence of a fixed content of silicon nitride (Si₃N₄) and varied contents of graphene nanoplatelets (GNPs) on the physical (density, structural, morphological) and mechanical properties (microhardness, nanoindentation) of Al-Si₃N₄-GNPs composites. The composites were fabricated by a microwave-assisted powder metallurgy route. The Si₃N₄ concentration was fixed at (5 wt.%) in Al-Si₃N₄-GNPs composites while the GNPs concentration was varied between (0 wt.%) to (1.5 wt.%) with an increment of (0.5 wt.%). The structural analysis indicates the formation of phase pure materials with high crystallinity. The microstructural analysis confirmed the presence of the Si₃N₄ and GNPs showing enhanced agglomeration with the increasing amount of GNPs. Moreover, the surface roughness of the synthesized composites increases with an increasing amount of GNPs reaching its maximum value (RMS = 65.32 nm) at 1.5 wt.% of GNPs. The Al-Si₃N₄-GNPs composites exhibit improved microhardness and promising load-indentation behavior during nanoindentation when compared to pure aluminum (Al). Moreover, Al-Si₃N₄-GNPs composites demonstrate higher values of compressive yield strength (CYS) and ultimate compressive strength (UCS) when compared to pure Al despite showing a declining trend with an increasing amount of GNPs in the matrix. Finally, a shear mode of fracture is prevalent in Al-Si₃N₄-GNPs composites under compression loading.     

Fabrication of a Novel Protein Sponge with Dual-Scale Porosity and Mixed Wettability Using a Clean and Versatile Microwave-Based Process

An open-porous protein sponge with mixed wettability is presented made entirely from whey proteins and with promising applications in biomedicine, pharmaceutical, and food industry. The fabrication relies on an additive-free, clean and scalable process consisting of foaming followed by controlled microwave-convection drying. Volumetric heating throughout the matrix induced by microwaves causes fast expansion and elongation of the foam bubbles, retards crust formation and promotes early protein denaturation. These effects counteract collapse and shrinkage typically encountered in convection drying of foams. The interplay of high protein content, tailored gas incorporation and controlled drying result in a dried structure with dual-scale porosity composed of open macroscopic elongated foam bubbles and microscopic pores in the surrounding solid lamellae induced by water evaporation. Due to the insolubility and mixed wettability of the denatured protein network, polar and non-polar liquids are rapidly absorbed into the interconnected capillary system of the sponge without disintegrating. While non-watery liquids penetrate the pores by capillary suction, water diffuses also into the stiff protein matrix, inducing swelling and softening. Consequently, the water-filled soft sponge can be emptied by compression and re-absorbs any wetting liquid into the free capillary space.     

Important Synthesis Parameters Affecting Crystallization of Zeolite T: A Review

Synthesis of zeolite T with a variety of desired characteristics necessitates extensive work in formulation and practical experiments, either by conventional hydrothermal methods or aided with different approaches and synthesis techniques, such as secondary growth or microwave irradiation. The objectives of this review are to adduce the potential work in zeolite T (Offretite-Erionite) synthesis, evaluating determining factors affecting the synthesis and quality of zeolite T crystals. Attention is given to extensive studies that interconnect with other significant findings.     

Analysis of dextromethorphan and dextrorphan in decomposed skeletal tissues by microwave assisted extraction,microplate solid‐phase extraction and gas chromatography‐ mass spectrometry (MAE‐MPSPE‐GCMS)

Analysis of decomposed skeletal tissues for dextromethorphan (DXM) and dextrorphan (DXT) using microwave assisted extraction (MAE), microplate solid‐phase extraction (MPSPE) and gas chromatography‐mass spectrometry (GC‐MS) is described. Rats (n = 3) received 100 mg/kg DXM (i.p.) and were euthanized by CO₂ asphyxiation roughly 20 min post‐dose. Remains decomposed to skeleton outdoors and vertebral bones were recovered, cleaned, and pulverized. Pulverized bone underwent MAE using methanol as an extraction solvent in a closed microwave system, followed by MPSPE and GC‐MS. Analyte stability under MAE conditions was assessed and found to be stable for at least 60 min irradiation time. The majority (>90%) of each analyte was recovered after 15 min. The MPSPE‐GCMS method was fit to a quadratic response (R² > 0.99), over the concentration range 10?10 000 ng?mL^‐1, with coefficients of variation <20% in triplicate analysis. The MPSPE‐GCMS method displayed a limit of detection of 10 ng?mL^‐1 for both analytes. Following MAE for 60 min (80 °C, 1200 W), MPSPE‐GCMS analysis of vertebral bone of DXM‐exposed rats detected both analytes in all samples (DXM: 0.9‐1.5 µg?g^‐1; DXT: 0.5‐1.8 µg?g^‐1). Copyright © 2014 John Wiley & Sons, Ltd.     

Intrinsic Dielectric Loss in Zr0.8Sn0.2TiO4 Ceramics Investigated by Terahertz Time Domain Spectroscopy

Terahertz time-domain spectroscopy (THz-TDS) was employed for estimation of intrinsic dielectric loss of Zr_0.8Sn_0.2TiO₄ (ZST) ceramics. Single-phase ZST dielectric resonators (DRs) with various synthesis parameters and, consequently, different extrinsic losses, were prepared by conventional ceramic technology. Even though the DRs exhibit a similar microstructure, their quality factor (Q is the inverse of dielectric loss tangent) measured in microwave (MW) domain at 6 GHz varies between 2500 and 8400. On the other hand, it was found that the THz dielectric loss is less sensitive to the sample preparation. The intrinsic losses (Q × f ~60 THz) of the ZST ceramics have been derived from THz data.     

超声造影评价经皮微波凝固治疗肝癌的疗效价值

目的探讨超声造影评价经皮微波凝固治疗肝癌近期疗效价值。方法 27例原发性肝癌患者,共31个病灶,对其经皮微波凝固治疗后行常规超声和超声造影检查,评价肿瘤灭活、残存或复发情况。结果 31个病灶中,26个病灶在造影各时相均未见增强,提示肿瘤完全灭活,但其中1个随访2个月增大;5个病灶动脉相治疗区残存增强病灶,门脉相及延迟相造影清退,提示有残存肿瘤,但其中1个随访12个月未见复发;超声造影诊断准确性为93.5%,敏感性为80.0%,特异性为96.1%。结论超声造影可以动态显示局部治疗区域的微循环特点及残存病灶形态,为再次补充治疗提供导向作用。     

通过头发中微量元素的测定探究大学生营养状况

在松江大学城随机抽取200名大学生头发样品,采用微波消解法溶解发样,并用原子吸收分光光度法测定处理液中Mn,Fe,Zn,Cu,Pb含量。结果显示,所测元素含量与文献值基本相符,方法所得回收率在93.70%~104.8%之间,结果较为满意。通过对数据的分析研究,对大学生的营养状况进行了初步评估,并简单分析了导致微量元素偏离的可能原因。     

A novel method to estimate changes in stress-induced salivary α-amylase using heart rate variability and respiratory rate,as measured in a non-contact manner using a single radar attached to the back of a chair

The authors have developed a non-contact system which estimates changes in salivary α-amylase (sAA ratio) induced by stress. Before and after stressful sound exposure, a single 24?GHz compact radar which is attached to the back of a chair measures the low frequency (LF) component of heart rate variability and respiratory rate, α-amylase in the subjects’ buccal secretions was measured by using an α-amylase assay kit. Using multiple regression analysis, sAA ratio was estimated using stress-induced LF change (LF ratio) and stress-induced respiratory rate change (respiratory rate ratio). Twelve healthy subjects were tested (12 males, 22?±?2 years), who were exposed to audio stimuli with a composite tone of 2120?Hz and 2130?Hz sine waves at a sound pressure level of 95?dB after a silent period through a headphone. The result showed that sAA ratio estimated using multiple regression analysis significantly correlated with measured sAA ratio (R?=?0.76, p?相似文献   

遂道式微波对灵芝孢子粉的灭菌实验研究

目的优选遂道式微波对灵芝孢子粉灭菌的工艺参数。方法以灭菌效果、灵芝孢子粉质量为指标,采用单因素试验对润湿剂、物料粒度、物料厚度、微波时间进行考察。结果获得较佳遂道式微波对灵芝孢子粉的灭菌工艺,其工艺参数为:75%乙醇润湿剂,30目筛粒度,1cm物料厚度,10min微波灭菌时间。结论优选的工艺灭菌效果佳,且灵芝孢子粉质量达标,该工艺可应用于工业化生产。     

微波治疗在糖尿病患者腹部术后切口愈合中的应用及护理

目的探讨微波治疗在糖尿病患者腹部术后切口愈合中的应用效果。方法选择2009年10月～2010年10月本院外科行腹部手术的2型糖尿病患者100例,随机分为实验组和对照组,每组各50例。对照组采用常规护理,实验组在此基础上增加微波照射治疗,比较两组患者术后切口愈合情况及各项临床指标的差异。结果两组患者切口愈合情况及愈合时间比较,均P<0.05,差异具有统计学意义,实验组切口愈合情况优于对照组,切口愈合时间短于对照组。结论糖尿病患者腹部手术后切口应用微波照射治疗,可促进切口愈合,提高愈合效果,减轻患者痛苦,从而缩短围手术期时间,促进患者康复。