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排序方式: 共有459条查询结果,搜索用时 15 毫秒
151.
研究了通过有机金属化学气相沉积技术及单源分子前躯体方法制备的Ni/Al2O3纳米复合材料的氢吸附(存储). 在冷壁的有机金属化学气相沉积反应器中,通过降解Ni(acac)2粉末基底上的[H2Al(OtBu)]2制备的Ni/Al2O3纳米复合材料. 通过X射线粉末衍射、扫描电镜、透射电镜以及能量色散型X射线荧光光谱等技术表征该复合材料. 采用自制Sievert's设备研究该复合材料的氢吸附(存储),可以储存约2.9%(重量比)的氢. 相似文献
152.
Hussain J Ullah R Khan A Khan FU Muhammad Z Shah MR 《Natural product communications》2011,6(2):171-173
A new tricyclic clerodane-type diterpenoid, trivially named phlomeoic acid (1), was isolated from the methanolic extract of Phlomis bracteosa, together with two known compounds, ursolic acid and glutinol, isolated for the first time from this species. Their structures were elucidated by means of spectroscopic and mass spectrometric techniques and comparison with literature data. 相似文献
153.
Shakir M Azam M Ullah MF Hadi SM 《Journal of photochemistry and photobiology. B, Biology》2011,104(3):449-456
A novel tetradentate Cu(II) complex of the type, [CuL](NO(3))(2) was synthesized by the interaction of Schiff base ligand, N,N-bis[(E)-2-thienylmethylidene]-1,8-naphthalenediamine, L obtained by the condensation of thiophene-2-carboxaldehyde and 1,8-diaminonaphthalene. The formation of Schiff base ligand, L and its Cu(II) complex was confirmed on the basis of results of elemental analyses, mass, FT-IR, (1)H and (13)C{(1)H} NMR spectral studies. UV-Vis, EPR and magnetic susceptibility data support a square planar environment around Cu(II) ion. However, molar conductance values confirmed 1:2 electrolytic nature for the Cu(II) complex. The electrochemical studies of Cu(II) complex was carried out by using cyclic voltammetry which revealed the complex to exhibit quasi reversible process. The biological activity of Cu(II) complex such as ability to bind DNA and DNA cleavage were studied where the Cu(II) complex was shown to cause considerable DNA cleavage and also generated reactive oxygen species such as superoxide anion. Since it is known that various anticancer drugs act through induction of oxidative stress that is mediated by reactive oxygen species, our results suggest a putative role of Cu(II) complex similar to various anticancer drugs. 相似文献
154.
Syed Qaiser Shah Aakif Ullah Khan Muhammad Rafiullah Khan 《Journal of Radioanalytical and Nuclear Chemistry》2011,288(1):207-213
The labeling of garenoxacin (GXN) with technetium-99m (99mTc) using different concentrations of GXN, sodium pertechnetate (Na99mTcO4), stannous chloride dihydrate (SnCl2·2H2O) at different pH was investigated and evaluated in terms of in-vitro stability in saline, serum, binding with multi-resistant
Staphylococcus aureus (MDRSA) and penicillin-resistant Streptococci (PRSC) and its biodistribution in artificially MDRSA and PRSC infected rats. 99mTc–GXN complex with 97.45 ± 0.18% radiochemical stability was prepared by mixing 3 mg of GXN with 3 mCi of Na99mTcO4 in the presence of 150 μL of SnCl2·2H2O (1 μg/μL in 0.01 N HCl) at a pH 5.6. The radiochemical stability of the complex was evaluated in normal saline up to 240 min
of reconstitution. It was observed that the complex showed maximum RCP values after 30 min of the reconstitution and remained
more than 90% up to 240 min. The complex showed radiochemical stability in normal saline at 37 °C up to 16 h with a 17.80%
de-tagging. The complex showed saturated in-vitro binding with living MDRSA and PRSC as compared to the insignificant binding
with heat killed MDRSA and PRSC. Biodistribution behavior of the complex was assessed in artificially infected with living
and heat killed MDRSA and PRSC rats. It was observed that the accumulation of the complex in the infected (live MDRSA and
PRSC) tissue of the rats was almost five fold than in the inflamed and normal tissue. The high radiochemical stability in
normal saline at room temperature, promising in-vitro stability in serum at 37 °C, saturated in-vitro binding with living
MDRSA and PRSC, specific biodistribution behavior and high infected (target) to normal (non-target) tissue and low inflamed
(non-target) to normal (non-target) tissue ratios we recommend 99mTc–GXN complex for in-vivo localization of infection caused by MDRSA and PRSC effective stains. 相似文献
155.
Fazal Haq Muhammad Ijaz Khan Sami Ullah Khan Khadijah M Abualnaja and M A El-Shorbagy 《中国物理 B》2022,31(8):84703-084703
This research presents the applications of entropy generation phenomenon in incompressible flow of Jeffrey nanofluid in the presence of distinct thermal features. The novel aspects of various features, such as Joule heating, porous medium, dissipation features, and radiative mechanism are addressed. In order to improve thermal transportation systems based on nanomaterials, convective boundary conditions are introduced. The thermal viscoelastic nanofluid model is expressed in terms of differential equations. The problem is presented via nonlinear differential equations for which analytical expressions are obtained by using the homotopy analysis method (HAM). The accuracy of solution is ensured. The effective outcomes of all physical parameters associated with the flow model are carefully examined and underlined through various curves. The observations summarized from current analysis reveal that the presence of a permeability parameter offers resistance to the flow. A monotonic decrement in local Nusselt number is noted with Hartmann number and Prandtl number. Moreover, entropy generation and Bejan number increases with radiation parameter and fluid parameter. 相似文献
156.
Spray cooling is an effective tool to dissipate high heat fluxes from hot surfaces. This article thoroughly investigates the effect of thickness of a hot stainless steel plate on the cooling time, cooling rate, heat flux, and heat transfer coefficient under constant mass flow rate maintained at 1 MPa using water as the coolant. Cylindrical samples of stainless steel with constant diameter (D = 25 mm) and thickness (δ = 7.5, 12, 16.5, and 21 mm) were used in the present study. Critical droplet diameter to achieve an ultra-fast cooling rate of 300°C/s was estimated by using an analytical model for samples of varying thicknesses. The analytical model (one side spray cooling) showed good agreement with experimental results with a relative error of 3.2% in the plate thickness range of 1–12 mm. An increasing trend in maximum heat flux was found with increasing thickness of the plate. Maximum heat flux as high as 1,800 kW/m2 was achieved for a 21-mm-thick sample. Heat transfer coefficients in the range 0.092–96.24 kW/m2K, 0.111–98.9 kW/m2K, 0.074–63.4 kW/m2K, and 0.127–55.63 kW/m2K were reported for sample of varying thicknesses in the present study. Limited published work is available with reference to water spray cooling dynamics and thickness of stainless steel plate. Therefore, the present study focuses on the correlation between the thickness of the plate and spray dynamics of water spray cooling. 相似文献
157.
Muhammad Usman Ghani Muhammad Sagir Muhammad Bilal Tahir Sami Ullah Mohammed Ali Assiri 《International journal of quantum chemistry》2024,124(3):e27340
Halide base perovskite LiCdX3 (X = F, Cl) is tested by CASTEP (Cambridge Serial Total Energy Package) based on density function theory (DFT). The presented discussion is to explore the structural, electronic, and optical properties of LiCdX3 (X = F, Cl). The calculated values of the lattice parameter are found to be 3.8 Å and 5.27 Å of LiCdF3 and LiCdCl3 respectively. The ideal structure of LiCdX3 (X = F, Cl) is cubic and dynamically stable. Electronic properties show that materials are semiconductors. The results from band structure are further evaluated by the total and partial density of states. The partial and total density of states confirms the degree of localization of electrons. In optical properties, the highest absorption coefficient is observed in LiCdCl3. The material is half metallic and has a narrow indirect band gap which may be used in photovoltaic applications. 相似文献
158.
R Dai Z Liu Y Liang F Geng C Ge K Ullah F Lv Y Zhang Y Deng 《Journal of separation science》2012,35(16):NA
DOI: 10.1002/jssc.201200247 A thermoresponsive chromatographic material was prepared through a simple method and employed for the temperature-modulated separation of peptides in an aqueous mobile phase. At 10°C, the grafted polymer chains are hydrophilic and in the form of extended coil. In this case, the peptides were unable to be separated and showed a single peak in chromatograms. In contrast, the polymer is hydrophobic and in the form of collapsed globule at 50°C. In this case, the peptides were completely separated because of the enhanced hydrophobic interaction of peptides and stationary phase. 相似文献
159.
Syed Naeem Razzaq Islam Ullah Khan Irfana Mariam Syed Saleem Razzaq 《Chemistry Central journal》2012,6(1):1-10
Background
Obtaining new pharmaceutical materials with enhanced properties by using natural compounds and environment-friendly methods is a continuous goal for scientists. Ficaria verna Huds. is a widespread perennial plant with applications in the treat of haemorrhoids and to cure piles; it has also anti-inflammatory, astringent, and antibiotic properties. The goal of the present study is the obtaining and characterization of new F. verna extract/??-cyclodextrin complexes by using only natural compounds, solvents, and environment-friendly methods in order to increase the quality and acceptability versus toxicity indicator. Thus, the flavonoid content (as quercetin) of Ficaria verna Huds. flowers and leaves from the West side of Romania was determined and correlated with their antioxidant activity. Further, the possibility of obtaining ??-cyclodextrin supramolecular systems was studied.Results
F. verna flowers and leaves extracts were obtained by semi-continuous solid-liquid extraction. The raw concentrated extract was spectrophotometrically analyzed in order to quantify the flavonoids from plant parts and to evaluate the antioxidant activity of these extracts. The F. verna extracts were used for obtaining ??-cyclodextrin complexes; these were analyzed by scanning electron microscopy and Karl Fischer water titration; spectrophotometry was used in order to quantifying the flavonoids and evaluates the antioxidant activity. A higher concentration of flavonoids of 0.5% was determined in complexes obtained by crystallisation method, while only a half of this value was calculated for kneading method. The antioxidant activity of these complexes was correlated with the flavonoid content and this parameter reveals possible controlled release properties.Conclusions
The flavonoid content of F. verna Huds. from the West side of Romania (Banat county) is approximately the same in flowers and leaves, being situated at a medium value among other studies. ??-Cyclodextrin complexes of F. verna extracts are obtained with lower yields by crystallisation than kneading methods, but the flavonoids (as quercetin) are better encapsulated in the first case most probably due to the possibility to attain the host-guest equilibrium in the slower crystallisation process. F. verna extracts and their ??-cyclodextrin complexes have antioxidant activity even at very low concentrations and could be used in proper and valuable pharmaceutical formulations with enhanced bioactivity. 相似文献160.
Ullah H. Davoudi B. Mariampillai A. Hussain G. Ikram M. Vitkin I. A. 《Laser Physics》2012,22(4):797-804
The increase of glucose levels in blood changes the viscosity of flowing fluids and shape of the erythrocytes. Both of these
can affect the details of light scattering as can be quantified via decorrelation times measured by optical coherence tomography
(OCT). The relative contributions of these competing effects have been studied by examining the motion dynamics of deformable
asymmetrical (red blood cells, RBCs with ∼7 μm diameter and ∼2 μm thickness) and non deformable symmetrical (polystyrene microspheres,
PSM with 1.4 μm diameter) flowing scattering particles. The fluid flow under the action of gravity was modulated by changing
the glucose concentrations. Quantitative analysis of the OCT’s M-mode autocorrelation functions enabled the derivations of
the translational diffusion coefficients. These systematic studies are aimed at eventual tissue imaging scenarios with speckle-variance
OCT to obtain local glucose concentrations maps. 相似文献