排序方式: 共有37条查询结果,搜索用时 15 毫秒
1.
Shanghua Li Zeming He Muhammet S. Toprak Christian Stiewe Eckhard Müller Mamoun Muhammed 《固体物理学:研究快报》2007,1(6):259-261
Maize‐like CoSb3 powders were obtained via the chemical alloying method. After the consolidation of the nanopowder using hot press, the CoSb3 compact shows a higher Seebeck coefficient and lower thermal conductivity. For the investigated CoSb3, a ZT of 0.15 at 673 K is shown. Though the achieved ZT does not reach the optimal value (0.17 to 0.18) for pure CoSb3, due to its lower electrical conductivity, the novel structure fabrication provides an interesting and promising approach to enhancing the thermoelectric performance. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献
2.
Fei Ye Jian Qin Muhammet S. Toprak Mamoun Muhammed 《Journal of nanoparticle research》2011,13(11):6157-6167
Multifunctional core–shell composite nanoparticles (NPs) have been developed by the combination of three functionalities into
one entity, which is composed of a single Fe3O4 NP as the magnetic core, mesoporous silica (mSiO2) with cavities as the sandwiched layer, and thermosensitive poly(N-isopropylacrylamide-co-acrylamide) (P(NIPAAm-co-AAm)) copolymer as the outer shell. The mSiO2-coated Fe3O4 NPs (Fe3O4@mSiO2) are monodisperse and the particle sizes were varied from 25 to 95 nm by precisely controlling the thickness of mSiO2-coating layer. The P(NIPAAm-co-AAm) were then grown onto surface-initiator-modified Fe3O4@mSiO2 NPs through free radical polymerization. These core–shell composite NPs (designated as Fe3O4@mSiO2@P(NIPAAm-co-AAm)) were found to be superparamagnetic with high r
2 relaxivity. To manipulate the phase transition behavior of these thermosensitive polymer-coated NPs for future in vivo applications,
the characteristic lower critical solution temperature (LCST) was subtly tuned by adjusting the composition of the monomers
to be around the human body temperature (i.e. 37 °C), from ca. 34 to ca. 42 °C. The thermal response of the core–shell composite
NPs to the external magnetic field was also demonstrated. Owing to their multiple functionality characteristics, these porous
superparamagnetic and thermosensitive NPs may prove valuable for simultaneous magnetic resonance imaging (MRI), temperature-controlled
drug release, and temperature-programed magnetic targeting and separation applications. 相似文献
3.
Xiaodi Wang Ying Ma Abhilash Sugunan Jian Qin Muhammet S. Toprak Bin Zhu Mamoun Muhammed 《Journal of nanoparticle research》2011,13(11):5879-5885
A facile surfactant-free nonaqueous method is presented to prepare uniform quasi-octahedral ceria, CeO2, mesocrystals, in which only Ce(NO3)3 and octanol were used as the reactants at a reaction temperature of 150 °C. CeO2 sample synthesized using this technique consists of well-dispersed quasi-octahedrons and exhibits an uniform size and morphology.
Based on structural characterization, it is proposed that the CeO2 mesostructure was formed by self-assembly of primary nanocrystals based on unique 3D oriented-attachment mechanism. Optical
characterization exhibited a strong quantum confinement, revealing small size of primary nanocrystals. The thermal stability
and UV–Vis study reveal CeO2 mesocrystal has various potential for high temperature applications and optical apparatus applications. 相似文献
4.
Cai X Burand MW Newman CR da Silva Filho DA Pappenfus TM Bader MM Brédas JL Mann KR Frisbie CD 《The journal of physical chemistry. B》2006,110(30):14590-14597
We report the structural and electrical characterization of thin films of organic semiconductor molecules consisting of an oligothiophene core capped with electron-withdrawing tricyanovinyl (TCV) groups. X-ray diffraction and atomic force microscopy of evaporated films of three different TCV-capped oligothiophenes showed that the films were highly crystalline. Electrical transport was measured in thin film transistors employing silver source and drain contacts and channel probes to correct for contact resistance. Three compounds exhibited n-channel (electron) conduction consistent with cyclic voltametry data that indicated they undergo facile reduction. Maximum electron mobilities were 0.02 cm2/V.s with an on/off current ratio of 10(6). A fourth end-capped molecule, TCV-6T-TCV, which had six thiophene rings, exhibited both p- and n-channel transport. Overall, these results confirm that substitution of oligothiophene cores with electron-withdrawing groups is a useful strategy to achieve electron-transporting materials. 相似文献
5.
Mo S Sydor PK Corre C Alhamadsheh MM Stanley AE Haynes SW Song L Reynolds KA Challis GL 《Chemistry & biology》2008,15(2):137-148
The red gene cluster of Streptomyces coelicolor directs production of undecylprodiginine. Here we report that this gene cluster also directs production of streptorubin B and show that 2-undecylpyrrole (UP) is an intermediate in the biosynthesis of undecylprodiginine and streptorubin B. The redPQRKL genes are involved in UP biosynthesis. RedL and RedK are proposed to generate UP from dodecanoic acid or a derivative. A redK(-) mutant produces a hydroxylated undecylprodiginine derivative, whereas redL(-) and redK(-) mutants require addition of chemically synthesized UP for production of undecylprodiginine and streptorubin B. Fatty acid biosynthetic enzymes can provide dodecanoic acid, but efficient and selective prodiginine biosynthesis requires RedPQR. Deletion of redP, redQ, or redR leads to an 80%-95% decrease in production of undecylprodiginine and an array of prodiginine analogs with varying alkyl chains. In a redR(-) mutant, the ratio of these can be altered in a logical manner by feeding various fatty acids. 相似文献
6.
Alhamadsheh MM Musayev F Komissarov AA Sachdeva S Wright HT Scarsdale N Florova G Reynolds KA 《Chemistry & biology》2007,14(5):513-524
The first step of the reaction catalyzed by the homodimeric FabH from a dissociated fatty acid synthase is acyl transfer from acyl-CoA to an active site cysteine. We report that C1 to C10 alkyl-CoA disulfides irreversibly inhibit Escherichia coli FabH (ecFabH) and Mycobacterium tuberculosis FabH with relative efficiencies that reflect these enzymes' differential acyl-group specificity. Crystallographic and kinetic studies with MeSSCoA show rapid inhibition of one monomer of ecFabH through formation of a methyl disulfide conjugate with this cysteine. Reaction of the second subunit with either MeSSCoA or acetyl-CoA is much slower. In the presence of malonyl-ACP, the acylation rate of the second subunit is restored to that of the native ecFabH. These observations suggest a catalytic model in which a structurally disordered apo-ecFabH dimer orders on binding either the first substrate, acetyl-CoA, or the inhibitor MeSSCoA, and is restored to a disordered state on binding of malonyl-ACP. 相似文献
7.
8.
Transport characterisation of a PIM system used for the extraction of Pb(II) using d2ehpa as carrier
German Salazar-Alvarez Ana Nelly Bautista-Flores Eduardo Rodríguez de San Miguel Mamoun Muhammed Josefina de Gyves 《Journal of membrane science》2005,250(1-2):247-257
The facilitated transport of lead(II) through polymeric inclusion membranes consisting of cellulose triacetate as polymeric support, bis-(2-ethylhexyl)-phosphoric acid (d2ehpa) as carrier, and tris-(2-butoxyethyl)phosphate as plasticiser (tbep), is investigated. The influence of some of the aqueous and membrane components on the permeability of Pb(II) was studied. The maximum flux obtained with these membranes is 3.5×10−6 mol m−2 s−1, which is of the same order of magnitude of those reported for supported liquid membranes and is in the upper range of those reported for polymeric inclusion membranes. Aqueous and membranes resistances were determined from a model that describes the transport mechanism across the membranes using the stoichiometric relationship and the extraction equilibrium constant value of 6.2×10−4 determined independently by solid–liquid extraction. An activation energy of 11 kJ mol−1 was also determined for Pb(II) migration, which suggest that the transport of Pb(II) is controlled by a membrane diffusion mechanism. Membrane characterisation was performed using several techniques including atomic force microscopy, scanning electron microscopy coupled with energy-dispersive spectroscopy, and thermal analysis. 相似文献
9.
[structure: see text] The design, total synthesis, and biological evaluation of two open-chain analogues of epothilone incorporating the critical C1-C8 fragment and the aromatic side chain held together by a small molecular scaffold have been achieved. Biological evaluation revealed that further restraint between the flexible C1-C8 region and the molecular scaffold may be necessary for potent inhibition of cell proliferation. 相似文献
10.
Mamoun A. Muhammed 《Journal of Radioanalytical and Nuclear Chemistry》1976,30(2):411-417
The extraction of hydrochloric acid by trilaurylamine (TLA) dissolved in benzene was studied in the presence and in absence of n-octanol. The extraction of HCl was found to be enhanced by the addition of octanoi to the organic phase. In order to explain this effect by means of the law of mass action, the systems TLA-HCL-benzene and n-octanol-HCl-benzene as well as TLA-octanol-benzene were also studied. It was found that TLA reacts with octanol to form a complex, TLAROH, while the octanol itself associates in benzene to form dimers and tetramers, although it does not extract HCl alone from the dilute solutions used in the present study. The enhancement of the extraction of HCl by TLA upon the addition of n-octanol could be described by the formation of the species TLA·ROH·HCl and its stability constant was determined. 相似文献