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51.
Omar Kammoun Nouha Loulou Walid Rekik Houcine Na?li Tahar Mhiri Thierry Bataille 《Journal of chemical crystallography》2012,42(2):103-110
Abstract
The new hybrid material, cobalt selenate templated by 1,4-diazabicyclo[2.2.2]octane (abbreviated dabco), has been synthesised by the slow evaporation method at room temperature. Its crystal structure was investigated using single crystal X-ray diffraction data. It crystallises in the monoclinic system (space group P21/c) with the following unit-cell parameters: a = 12.9169(2) ?, b = 11.9101(2) ?, c = 12.4951(2) ?, β = 108.484(1)°, V = 1823.10(5) ?3 and Z = 4. The supramolecular structure of (C6H14N2)[Co(H2O)6](SeO4)2 consists of isolated [Co(H2O)]2+ and (C6H14N2)2+ cations and (SeO4)2− anions linked together by three dimensional hydrogen-bond network. The infrared spectroscopy confirmed the presence of these different entities. The thermal behaviour of the precursor, studied by thermodiffractometry and thermogravimetric analyses, indicates that its decomposition proceeds through three stages giving rise to the cobalt oxide. 相似文献52.
Mouna Hnaien Walid Mohamed Hassen Adnane Abdelghani Stéphane Cotte Didier Leonard François Bessueille Nicole Jaffrezic-Renault 《Electrochemistry communications》2009,11(1):165-168
A conductometric enzyme biosensor using proteinase K was developed and then tested to relate its electrical signal to the number of proteinase K hydrolysis sites in bovine serum albumin (BSA) and angiotensin, a ten amino acid peptide, with one cleaving site.The conductometric sensor presents a large linear range of response for BSA and angiotensin ranging from 0.5 to 8 mg/l and from 4 to 8 mg/l, respectively. For a same tested concentration (mg/l), the response for native BSA is 12 times higher than for angiotensin. Aspartam was used as negative test and no response was obtained with the proteinase K biosensor. The conductometric sensor permitted also to detect difference on enzyme activity on native and non-native BSA, a response three times higher was obtained for non-native BSA. 相似文献
53.
Walid Fakhfakh Slim Kaddeche Ali Abdennadher Daniel Henry Hamda Ben Hadid 《Comptes Rendus Mecanique》2006,334(5):332-339
A numerical study is conducted in order to determine the influence of a vertical magnetic field, the Reynolds number and a temperature stratification on the instabilities occurring in the Hartmann flow heated from below. For and , the results show that the vertical magnetic field has a stabilizing effect on both transverse oscillatory travelling waves and longitudinal stationary rolls . The temperature stratification is responsible of a destabilization of the transverse modes and the appearance of longitudinal modes non-existent for the isothermal Hartmann flow. Moreover, the extent of the domains of Re where the transverse modes prevail is found to narrow when Ha increases and to widen when Ra increases for a given value of Ha. On the other hand, for the modes, the extent of the domains of Re where they prevail increases when Ha grows. To cite this article: W. Fakhfakh et al., C. R. Mecanique 334 (2006). 相似文献
54.
Fathalla A. Rihan 《Numerical Methods for Partial Differential Equations》2010,26(6):1556-1571
This article is concerned with ?‐methods for delay parabolic partial differential equations. The methodology is extended to time‐fractional‐order parabolic partial differential equations in the sense of Caputo. The fully implicit scheme preserves delay‐independent asymptotic stability and the solution continuously depends on the time‐fractional order. Several numerical examples of interest are included to demonstrate the effectiveness of the method. © 2009 Wiley Periodicals, Inc. Numer Methods Partial Differential Eq 2010 相似文献
55.
Walid Rekik Houcine Na?li Tahar Mhiri Thierry Bataille 《Journal of chemical crystallography》2007,37(2):147-155
The crystal structure of manganese sulfate templated by 1,4-diaza-bicyclo[2.2.2]octane (abbreviated dabco), (C6H14N2)[Mn(H2O)6](SO4)2, was investigated using single crystal X-ray diffraction data. It crystallises in the monoclinic system (space group P21/c) with the following unit-cell parameters: a = 12.1392(2) ?, b = 12.3117(2) ?, c = 12.2765(2) ?, β = 104.607(1)°, V = 1775.47(5) ?3 and Z = 4. The structure has been solved using direct methods and refined by least-squares analysis [R
1 = 0.0381, wR
2 = 0.1082]. The crystal structure of the title compound is built from isolated [Mn(H2O)6]2+ octahedral cations, 1,4-diaza-bicyclo[2.2.2]octandiium cations (C6H14N2)2+ and sulfate anions (SO4)2− connected by a three-dimensional hydrogen-bond network. The thermal decomposition of the precursor, studied by thermogravimetry
and temperature-dependent X-ray powder diffraction, proceeds through four stages giving rise to the mixture of Mn2O3and Mn3O4.
Supplementary Material CCDC 620298 contains the supplementary crystallographic data for this paper. These data can be obtained free of charge from
The Cambridge Crystallographic Data Centre via www.ccdc.cam.ac.uk/data_request/cif. 相似文献
56.
We study the time evolution of a periodically driven quantum-mechanical system coupled to several reservoirs of free fermions
at different temperatures. This is a paradigm of a cyclic thermodynamic process. We introduce the notion of a Floquet Liouvillean
as the generator of the dynamics of the coupled system on an extended Hilbert space. We show that the time-periodic state
which the state of the coupled system converges to after very many periods corresponds to a zero-energy resonance of the Floquet
Liouvillean. We then show that the entropy production per cycle is (strictly) positive, a property that implies Carnot's formulation
of the second law of thermodynamics. 相似文献
57.
Hydrophobically modified silica nanocomposites have been prepared using a low temperature sol-gel process. In this study, an alkyltriethoxysilane derivative, hexdecyltrimethoxysilane (HDTMS), was co-condensed with tetraethoxyorthosilicate (TEOS) with and without a cross-linking agent, 3-glycidoxypropyltrimethoxysilane (GPTMS), to produce the modified composites. The hydrophobic properties were determined using contact angle measurement. FESEM observations revealed a semispherical nanostructure of the composites with grain size of about 50-75 nm in diameter. The chemical modification was studied by FTIR and EDX, whereas the physicothermal properties were analyzed by DSC and TGA. These long-chain alkyl modified silica nanocomposites are promising materials for use in hydrophobic and water-resistant applications. 相似文献
58.
The key intermediates allyloxyquinoxaline 2a–c and N‐allylquinoxaline 3a–c were used to synthesize a number of acyclonucleosides whose chemical modifications include quinoxaline ring and the acyclic part is either N1‐propanediol or 3‐hydroxy‐ propyl substituents and their O‐analogues. These compounds were characterized by elemental analysis, MALDI MS, and NMR data. © 2006 Wiley Periodicals, Inc. Heteroatom Chem 17:280–288, 2006; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/hc.20203 相似文献
59.
Yi‐He Zhang Zhi‐Min Dang John H. Xin Walid A. Daoud Jun‐Hui Ji Yuyang Liu Bin Fei Yuanqing Li Juntao Wu Shiyong Yang Lai‐Feng Li 《Macromolecular rapid communications》2005,26(18):1473-1477
Summary: Polyimide‐mica hybrid films were prepared via ultrasonic dispersion and in situ polymerization process from a solution of a polyimide precursor and mica in N,N‐dimethylacetamide, and their structure was characterized by FTIR and XRD techniques. The dependence of dielectric properties, such as dielectric constant and electrical breakdown strength, of the hybrid films on the content of mica was studied at room and cryogenic temperatures. The results show that the dielectric constant of PI‐mica hybrid films decreases with the increase of the mica content at temperatures from −150 to 150 °C and at frequency range from 1 kHz to 1 MHz. It was found that the cryogenic electrical breakdown strength of the PI‐mica hybrid films could meet the requirements of cryogenic insulating materials.
60.
Stachybotrys microspora is a filamentous fungus secreting multiple β-glucosidases. Two of them were characterized. The third one, named bglG, was also characterized and used for various investigations. The current work undertakes the plausible role played by some cultural conditions and physico-chemical properties to improve bglG time course synthesis and also its catalytic efficiency. Indeed, bglG time course synthesis is slightly affected by light, but it is clearly affected by aeration and presence of baffle. On the same case, optimization of substrate and enzyme concentration contributes to the improvement of the catalytic efficiency of bglG. This biocatalyst tolerates a high ionic strength during its activity assay; β-mercaptoethanol increases the enzymatic rate. BglG has the capacity to hydrolyse efficiently oleuropéin, with a recovery of 88 %. 相似文献