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排序方式: 共有1375条查询结果,搜索用时 15 毫秒
41.
Design optimization of an encapsulated carbon composite thermal control (TC) system is presented. The composite TC system consists of multiple phase change materials (PCM) doped with carbon nanotubes and enclosed in a casing of carbon/carbon composite sheets. Using the concept of global thermal resistance an analytical model was formulated to predict the transient temperature distribution through the composite system. The temperature data was then used to estimate maximum energy storage and heat dissipation rates. A substantial reduction in weight and size of the TC composite was observed corresponding to the optimized design. The use of carbon nanotubes both as additives with optimal loading and as a thermal interface material significantly reduced the maximum junction temperatures for different constant power loads for the multiple PCM composite as compared to its original size used for the experimental work. The optimized composite minimized the total thermal resistance through the composite sample and thereby increased its thermal response as indicated by approximately 4 times increase in the heat dissipation rate. 相似文献
42.
Sana Ghayas Muhammad Harris Shoaib Faaiza Qazi Rabia Bushra Fatima Ramzan Ali Madiha Maboos Farah Khalid 《Polymer Bulletin》2020,77(3):1281-1306
This work is based on formulating and optimizing controlled release (CR) valsartan (160 mg) tablets using different viscosity grades of the cellulosic polymer. The objective was to develop an effective once-daily drug delivery system of this cardiovascular agent. Central composite design was used for designing the formulations. Polymers used were Methocel® K4M, K15M and K100M. Compatibility of excipients with active was studied through FT-IR. Micromeritic properties were determined and formulations exhibiting appropriate flow characteristics were compressed. Swelling behavior and in vitro buoyancy effect were studied and response surface curves were constructed to optimize the formulation. Multi-point dissolution profiles of valsartan CR tablets at pH 1.2, 4.5 and 6.8 were obtained. Model-dependent and model-independent methods were performed including f2, stability test as per ICH guidelines and ANOVA. FT-IR studies revealed the compatibility of valsartan with all excipients. Formulation K4T9 (containing 25% K4M polymer) was selected to be the best optimized trial, based on physical properties and controlled release profile (23% at 4 h, 82% at 16 h and 100% at 24 h). Results of buoyancy and swelling behavior indicated that HPMC-K4M polymer exhibited excellent floating lag time and swelling indexes. In vitro drug release kinetics showed that formulation K4T9 displayed Korsmeyer–Peppas drug release pattern with r value > 0.99. The manufacturing process of K4T9 was also found to be reproducible with a shelf life period of 41 and 36 months at room temperature and accelerated conditions, respectively. Valsartan CR matrix-based formulation was successfully prepared with Methocel K4M retardant. 相似文献
43.
A Al-Othman S Al-Musharaf NM Al-Daghri S Yakout KM Alkharfy Y Al-Saleh OS Al-Attas MS Alokail O Moharram S Sabico S Kumar GP Chrousos 《Nutrition journal》2012,11(1):56
ABSTRACT: BACKGROUND: Coffee and tea consumption was hypothesized to interact with variants of vitamin D-receptor polymorphisms, but limited evidence exists. Here we determine for the first time whether increased coffee and tea consumption affects circulating levels of 25-hydroxyvitamin D in a cohort of Saudi adolescents. METHODS: A total of 330 randomly selected Saudi adolescents were included. Anthropometrics were recorded and fasting blood samples were analyzed for routine analysis of fasting glucose, lipid levels, calcium, albumin and phosphorous. Frequency of coffee and tea intake was noted. 25-hydroxyvitamin D levels were measured using enzyme-linked immunosorbent assays. RESULTS: Improved lipid profiles were observed in both boys and girls, as demonstrated by increased levels of HDL-cholesterol, even after controlling for age and BMI, among those consuming 9--12 cups of coffee/week. Vitamin D levels were significantly highest among those consuming 9--12 cups of tea/week in all subjects (p-value 0.009) independent of age, gender, BMI, physical activity and sun exposure. CONCLUSION: This study suggests a link between tea consumption and vitamin D levels in a cohort of Saudi adolescents, independent of age, BMI, gender, physical activity and sun exposure. These findings should be confirmed prospectively. 相似文献
44.
Lina M. Shaker Waleed Khalid Al-Azzawi Ahmed Al-Amiery Mohd S. Takriff Wan Nor Roslam Wan Isahak 《乙烯基与添加剂工艺杂志》2023,29(6):1023-1035
Biocompatible polymers such as poly(vinyl alcohol) (PVA) and poly(vinyl pyrrolidone) are used to prepare hydrogels for biomedical applications, including optical applications such as the manufacture of sensing devices, cosmetic and smart, and medical contact lenses, among others. In this study, three contact lenses were prepared by doping PVP-PVA supportive hydrogel with 0.1, 0.5, and 1 wt% of laboratory-manufactured Ag NPs. The work demonstrates the evaluation of vision correction through each lens and the effect of changing the concentration of silver on its refractive index. The simulation involved the design and simulation of an aberrated human eye based on the Liou and Brennan model (LBM), and the insertion of the contact lenses for vision correction using the ZEMAX optical design program. This work also included a study of the antimicrobial properties of the resulting hydrogel contact lenses doped with Ag NPs. The resulting refractive index of one PVP-PVA-Ag lens was relatively high at 532 nm = 1.604, which made the lens provide the highest image contrast (the lowest MTF curve degradation) of 0.883 ± 0.027 at 20 cycles/mm and an RMS nearly the Airy disc diameter of 3.983 μm. PVA was used in combination with PVP for stabilizing Ag NPs to give the contact lenses an antibacterial property. Finally, the optimum contact lens with a 1 wt% Ag NPs concentration showed the highest inhibition activity. 相似文献
45.
Karim Chkirate Gamal Al Ati Khalid Karrouchi Saad Fettach Hind Chakchak Joel T. Mague Smaail Radi N. N. Adarsh My El Abbes Faouzi El Mokhtar Essassi Yann Garcia 《Chembiochem : a European journal of chemical biology》2023,24(20):e202300331
Three dinuclear coordination complexes generated from 1-n-butyl-2-((5-methyl-1H-pyrazole-3-yl)methyl)-1H-benzimidazole ( L ), have been synthesized and characterized spectroscopically and structurally by single crystal X-ray diffraction analysis. Reaction with iron(II) chloride and then copper(II) nitrate led to a co-crystal containing 78 % of [Cu(NO3)(μ-Cl)( L’ )]2 ( C1 ) and 22 % of [Cu(NO3)(μ-NO3)( L’ )]2 ( C2 ), where L was oxidized to a new ligand L’ . A mechanism is provided. Reaction with copper chloride led to the dinuclear complex [Cu(Cl)(μ-Cl)( L) ]2 ( C3 ). The presence of N−H⋅⋅⋅O and C−H⋅⋅⋅O intermolecular interactions in the crystal structure of C1 and C2 , and C−H⋅⋅⋅N and C−H⋅⋅⋅Cl hydrogen bonding in the crystal structure of C3 led to supramolecular structures that were confirmed by Hirshfeld surface analysis. The ligands and their complexes were tested for free radical scavenging activity and ferric reducing antioxidant power. The complex C1 / C2 shows remarkable antioxidant activities as compared to the ligand L and reference compounds. 相似文献
46.
The dynamics of a gas‐solid fluidized bed containing Geldart Group D particles mixed with a small proportion of Geldart Group B particles are investigated using pressure fluctuations data. Time series analysis, using a variety of nonlinear dynamics tools, shows that the slugging present with Group D particles can be suppressed by the addition of a small proportion of Group B particles. The power spectra and the auto‐correlation function are used for a preliminary evaluation of dominant slug frequencies. It is shown that the bed fluidized with the mixture of Group D and B particles behaves in a less periodic manner and is dominated by more random bubble motion. On the other hand, the correlation integral is used to analyze the chaotic behaviour of the flow, through evaluation of the fractal structure of the reconstructed attractors. It is shown that the bed fluidized with Group D particles is characterized by a combination of steady slug motion and irregular particles motion. The behaviour of the fluidized bed of Group D/B particles mixture is characterized by a single correlation dimension for a wide range of fluidization velocities. 相似文献
47.
Summary The synthesis of telechelic monodispersed diols produced from the radical telomerization of an excess of undecylenol with commercialy available , -dithiols HSC2H4XC2H4SH (X=0, S or CH2) initiated by peroxides is presented. In each case, the diols were obtained selectively and quantitatively and they were characterized by both 1H and 13C NMR. Their physical characteristics (Tg, Tm and decomposition temperatures) were determined. Such compounds are thermally more stable than polydispersed telechelic commercially available diols. 相似文献
48.
49.
Nonhypothesis Analysis of a Mutagenic Soybean (Glycine max [L.]) Population for Protein and Fatty‐Acid Composition 下载免费PDF全文
James Anderson Naoufal Lakhssassi Stella K. Kantartzi Khalid Meksem 《Journal of the American Oil Chemists' Society》2018,95(4):461-471
Soybean is a major source of oil for food, feed, and biofuel production. Mutagenesis is a tool for creating unique traits useful in breeding programs. The aim of this study is to use nonhypothesis statistical testing methods to make decisions about a mutagenic population. To this end, a total of 1037 mutation lines and 28 wild‐type lines were analyzed for fatty‐acid composition and protein content. Principal component analysis (PCA) was used to analyze the fatty acid profile, multivariate analysis of variance (MANOVA) to build a selection model for seed weight per plant and weight per 10 seeds, and clustering in conjunction with power analysis to determine the minimum number of individuals needed to create a MANOVA selection model for the oil to protein content. Five of the 35 possible entries were identified by PCA analysis for stearic acid and four of 16 possible entries for oleic acid. Interestingly, most of the selected mutants were validated genetically. In fact, selected mutants with high seed stearic acid or high seed oleic acid contents were verified to carry mutations on GmFAD2‐1A, GmFAD2‐1B, and GmSACPD‐C genes. This shows a promising method of identifying smaller portion of the population to screen for desired mutations. 相似文献
50.
Fabrication of ceramic nanofibers using polydimethylsiloxane and polyacrylonitrile polymer blends 下载免费PDF全文
Nanofibers with several hundred of nanometers were successfully fabricated using electrospinning process and a mixture of two types of polymers which are: polydimethylsiloxane and polyacrylonitrile as precursors. After stabilization and carbonization at 1000 °C, three phases which are: silicon carbide (SiC), carbon, and oxy‐SiC were presented. Spectroscopic and microscopic techniques had confirmed the presence of nanocrystalline SiC and turbostratic carbons. These phases formed an intertwined network at the nanometric scale. In addition, the resulted fibers showed a core‐skin effect with skin richer in carbon and a core mainly dominated by silicon‐based phases in the form SiC or Si? O? C ceramics. A significant improvement was observed in both tensile strength and elastic modulus in these hybrid fibers. In term of crystallography, these nanofibers seem to exhibit similar microstructure that was observed in Nicalon fiber. However, it was difficult to determine the ratio of these phases and their influence on the physical properties of these hybrid fibers. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 45967. 相似文献