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排序方式: 共有666条查询结果,搜索用时 15 毫秒
31.
Spherical particles (~3 μm) of copper(II) oxalate were produced in the form of precipitated solids by gently mixing aqueous solutions of oxalic acid and copper nitrate with predetermined concentrations at room temperature. These particles were isolated from the mother liquor and then coated with cobalt basic carbonate. The coating trials involved heating of the aqueous dispersions, containing known amounts of the dispersed copper oxalate particles (cores), urea, and cobalt nitrate, at 70–85 °C for various periods of time with constant stirring. The heating process decomposed urea, increased pH, liberated carbonate ions, which resulted in the precipitation of the dissolved cobalt ions in the form of shells of cobalt basic carbonate around each core particle. The coating process was sensitive to the applied experimental parameters, since uniformly coated particles were obtained under a narrow range of coating mixture composition. In the absence of the cores, the same reactants solutions produced coating precursor particles (cobalt basic carbonate), when subjected to similar heating conditions. Physical and chemical analyses indicated that the coating material of the coated particles and the coating precursor particles had the same chemical compositions. The as-prepared core, coating precursor, and coated particles were converted into oxide forms by heating their dry powders at elevated temperatures under controlled heating conditions. The heat treatment produced obvious changes in the surface morphology of these particles due to loss of material. Moreover, the heat-treated particles preserved shape integrity to a maximum extent, showing their thermal stability. Selected batches of the as-prepared and heat-treated products were characterized by various physical methods. 相似文献
32.
33.
BACKGROUND: Plant breeders have attempted to improve the nutritonal value of lucerne (alfalfa) by selecting for higher protein and lower fibre concentrations. Although targeted at ruminants, such changes could also improve the nutritional value of lucerne for monogastrics. The objective of this study was to determine the effects of graded levels of dehydrated lucerne meal on nutrient digestibility, performance and carcass traits of swine. RESULTS: The digestibility of dry matter, protein and energy declined linearly (P < 0.05) as the level of lucerne meal in the diet increased. Including lucerne meal at levels greater than 75 g kg?1 was detrimental to the growth rate of pigs during the growing period. During the finishing period, inclusion of lucerne meal at 75 and 150 g kg?1 resulted in improvements in weight gain and feed intake. Carcass traits were generally unaffected by lucerne inclusion. CONCLUSION: Lucerne meal may have greater potential for inclusion in diets fed to growing–finishing pigs than previously realized. To maximize pig performance, lucerne meal should be limited to less than 75 g kg?1 diet during the growing period, while it is possible to go as high as 150 g kg?1 diet during the finishing period without detrimental effects on performance. Copyright © 2008 Society of Chemical Industry 相似文献
34.
Attrition behavior of fine particles in a fluidized bed with bimodal particles: Influence of particle density and size ratio 总被引:1,自引:0,他引:1
Zeeshan Nawaz Tang Xiaoping Xiaobo Wei Fei Wei 《Korean Journal of Chemical Engineering》2010,27(5):1606-1612
To process the solid particulates in fluidized bed and slurry phase reactors, attrition is an inevitable consequence and is
therefore one of the preliminary parameters for the catalyst design. In this paper, the mechanical degradation propensity
of the zeolite catalysts (particles) was investigated in a bimodal distribution environment using a Gas Jet Attrition — ASTM
standard fluidized bed test (D-5757). The experimentation was conducted in order to explore parameters affecting attrition
phenomena in a bimodal fluidization. In a bimodal fluidization system, two different types of particles are co-fluidized isothermally.
The air jet attrition index (AJI) showed distinct increases in the attrition rate of small particles in a bimodal fluidization
environment under standard operating conditions, in comparison with single particle. A series of experiments were conducted
using particles of various sizes, with large particles of different densities and sizes. Experimental results suggest that
the relative density and particle size ratio have a significant influence on attrition behavior during co-fluidization. Therefore
a generalized relationship has been drawn using Gwyn constants; those defined material properties of small particles. Moreover,
distinct attrition incremental phenomenon was observed during co-fluidization owing to the change in collision pattern and
impact, which was associated with relative particle density and size ratios. 相似文献
35.
Adnan Khan Bushra Shal Ashraf Ullah Khan Rahim Ullah Muhammad Waleed Baig Ihsan ul Haq Eun Kyoung Seo Salman Khan 《International journal of molecular sciences》2021,22(11)
Vincristine (VCR) is a widely used chemotherapy drug that induced peripheral painful neuropathy. Yet, it still lacks an ideal therapeutic strategy. The transient receptor potential (TRP) channels, purinergic receptor (P2Y), and mitogen-activated protein kinase (MAPK) signaling play a crucial role in the pathogenesis of neuropathic pain. Withametelin (WMT), a potential Phytosteroid isolated from datura innoxa, exhibits remarkable neuroprotective properties. The present investigation was designed to explore the effect of withametelin on VCR-induced neuropathic pain and its underlying molecular mechanism. Initially, the neuroprotective potential of WMT was confirmed against hydrogen peroxide (H2O2)-induced PC12 cells. To develop potential candidates for neuropathic pain treatment, a VCR-induced neuropathic pain model was established. Vincristine (75 μg/kg) was administered intraperitoneally (i.p.) for 10 consecutive days (day 1–10) for the induction of neuropathic pain. Gabapentin (GBP) (60 mg/kg, i.p.) and withametelin (0.1 and 1 mg/kg i.p.) treatments were given after the completion of VCR injection on the 11th day up to 21 days. The results revealed that WMT significantly reduced VCR-induced pain hypersensitivity, including mechanical allodynia, cold allodynia, and thermal hyperalgesia. It reversed the VCR-induced histopathological changes in the brain, spinal cord, and sciatic nerve. It inhibited VCR-induced changes in the biochemical composition of the myelin sheath of the sciatic nerve. It markedly downregulated the expression levels of TRPV1 (transient receptor potential vanilloid 1); TRPM8 (Transient receptor potential melastatin 8); and P2Y nociceptors and MAPKs signaling, including ERK (Extracellular Signal-Regulated Kinase), JNK (c-Jun N-terminal kinase), and p-38 in the spinal cord. It suppressed apoptosis by regulating Bax (Bcl2-associated X-protein), Bcl-2 (B-cell-lymphoma-2), and Caspase-3 expression. It considerably attenuated inflammatory cytokines, oxidative stress, and genotoxicity. This study suggests that WMT treatment suppressed vincristine-induced neuropathic pain by targeting the TRPV1/TRPM8/P2Y nociceptors and MAPK signaling. 相似文献
36.
B. Bhatia H. L. Sarkar D. K. Banerjee Inamul Haq 《The International journal of environmental studies》2013,70(1-2):111-123
Four‐hourly data were collected for 24 hour periods in the months of December (1977), April (1978), July (1978) and December (1978) in respect of some physicochemical characteristics and plankton population in a protected part of the Loktak Lake (Manipur) India. Highly significant correlations, positive as well as negative, were observed between the diurnal and seasonal variations of physicochemical characteristics with those of total phyto or zooplankton of certain species. 相似文献
37.
Haq Nawaz Bhatti Mohammad Hamid Rashid Rakhshanda Nawaz Muhammad Asgher Raheela Perveen Abdul Jabbar 《Food chemistry》2007,103(2):338-343
Thermostable enzymes are currently being investigated to improve industrial processes of starch saccharification. A novel glucoamylase was purified to electrophoretic homogeneity from the culture supernatant of Fusarium solani on a fast protein liquid chromatographic system (FPLC). The recovery of glucoamylase after gel filtration on FPLC was 31.8% with 26.2-fold increase in specific activity. The enzyme had a molecular mass of 40 kDa by SDS-PAGE and 41 kDa by gel filtration. The glucoamylase exhibited optimum activity at pH 4.5. The Kcat and Km were 441/min and 1.9 mg/ml, respectively, for soluble starch, specificity constant (Kcat/Km) was 232. The enzyme was thermally stable at 50 °C and retained 79% activity after 60 min at this temperature. The half-life of the enzyme was 26 min at 60°C. The enzyme was slightly stimulated by Cu2+ and Mg2+ and strongly inhibited by Hg2+, Pb2+, Zn2+, Ni2+ and Fe3+. 相似文献
38.
Saima Rehman Haq Nawaz Bhatti Zafar Iqbal & Umer Rashid 《International Journal of Food Science & Technology》2008,43(2):346-350
The essential oil components of different tea brands were investigated by gas chromatography. The oil yields of dried tea samples were ranged from 0.09% to 0.63%. Twenty-five compounds from Supreme and Lipton Yellow Label tea brands representing 98.0% and 88.0% of the Camellia sinensis oil were identified, respectively. The main ones were β-pinene (51.2%) and α-pinene (30.2%). Nineteen components from Tapal tea brand representing 76.7% of the C. sinensis oil were determined with high contents of muurol-5-en-4-a-ol (10.5%) and muurol-5-en-4-b-ol (31.3%). Fifteen components from Deer and Diana tea brands were identified, accounting for 83.3% and 78.2% of the oil containing α-cadinol and β-pinene. Seventeen components from non-branded teas were determined with high contents of muurol-5-en-4-a-ol and muurol-5-en-4-b-ol. Twenty-one compounds from non-branded Bangladeshi Shezan and Indian teas were also identified. All oils consisted of monoterpenic hydrocarbons, oxygenated monoterpenes and sesquiterpenes. 相似文献
39.
Bulk superconductors of the (Bi1–x
Pb
x
)2Sr2Ca2Cu3O
y
system have been synthesized by changing the Bi/Pb ratio. The effect of Pb substitution onT
c has been studied by standard d.c. resistivity measurements. An appropriate thermal procedure and time for the preparation of the 110 K phase has also been studied at length. The experiments indicate that the best results are obtained forx=0.2 and that a slow cooling process is necessary for a better control of the thermal process. Indexed X-ray diffraction patterns indicate the lattice parameters of low- and high-T
c phases asa
L=0.54004 nm,b
L=0.5445 nm,c
L=3.084 nm anda
H=0.5483 nm,b
H=0.5339 nm,c
H=3.772 nm, respectively. The observed superconducting behaviour is stable on thermal cycling between 77 and 300 K. 相似文献
40.
We present a new charge conserving capacitance model for Gallium-Arsenide (GaAs) metal semiconductor field effect transistors (MESFET's) based on the quasi-static approximation and a proper partitioning of the channel charge between the source and the drain terminals. A total of nine so-called transcapacitances were determined by taking derivatives of the various terminal charges with respect to the voltages at source, drain, and gate. The transcapacitances are nonreciprocal, i.e., Cij≠Cji when i≠j, and can be organized in a 3×3 matrix incorporating Kirchhoff's current law (charge conservation) and independence of reference. The present capacitance model is valid both above and below threshold, and shows good agreement with experimental data over a wide range of gate and drain biases. The model is analytical and suitable for implementation in circuit simulators 相似文献