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71.
A five step synthesis of (±)-bis-homosarkomycin ethyl ester 6 has been achieved starting from commercially available ethyl phosphonoacetate and ethyl 5-bromovalerate. The successful synthetic approach to 6 uses α-methylene pimelate 3 as a key intermediate. 相似文献
72.
Renata Dreos Lassaad Mechi Lucio Randaccio Ennio Zangrando Rached Ben Hassen 《Journal of organometallic chemistry》2006,691(15):3305-3309
The reduction of [Co(III)(tmsalen)(py)2]+ with NaBH4/PdCl2 and the successive oxidative addition of CH2ClI, carried out in neutral methanolic solution and followed by the addition of NaOH, afford a new dinuclear complex. The molecular structure reveals that it is formed by an octahedral [Co(tmsalen)(py)(OH)] unit connected to a β-folded [Co(tmsalenCH2)]+ fragment, in such a way that the latter metal completes the coordination sphere with the hydroxo group and a tmsalen oxygen from the former unit. 相似文献
73.
Jean-Claude Champarnaud-Mesjard Bernard Frit Abdeslam Chagraoui Abdelmjid Taïri 《无机化学与普通化学杂志》1996,622(11):1907-1912
Bi2Te2WO10 crystallises in the monoclinic system (space group C2/c, Z = 4) with a = 12.4972(7) Å, b = 5.6414(3) Å, c = 12.2705(6) Å and β = 91.38(3)°. The structure has been solved by means of single crystal X-ray diffraction data analysis. The reliability factors are R1 = 0.030 and wR2 = 0.065 for 1258 structure factors and 70 parameters. The Bi2Te2WO10 crystal structure can be described as a regular stacking along the Ox axis of polyhedral layers with the stereochemically active lone pairs E of the BiIII and TeIV atoms all located between these layers. The cohesion of the three-dimensional network is therefore only ensured between succesive layers by weak Bi? O(5) bonds. 相似文献
74.
W. Louaer A. -H. Meniai J. -P. E. Grolier 《Journal of Thermal Analysis and Calorimetry》2008,93(2):605-610
Starch is an important natural substance in which the water content has a significant influence on its structure and properties.
In the present study, the effect of the water content on glass transition temperatures T
g and heat capacities C
p of wheat, maize and potato starches were investigated by high-sensitivity differential scanning calorimetry (temperature
modulated TMDSC and conventional DSC). Thermal analysis measurements were performed on starch samples with different water
contents. The exact water mass percentage of each sample was determined using the Karl-Fischer method.
The obtained results show that the water content does influence the starch thermal properties in a systematic and measurable
trend, the higher the water% the lower the glass transition temperature, and the higher the heat capacity jump during gelatinisation.
At this stage possible interpretations of the results are just put forward and should be confirmed through complementary measurements. 相似文献
75.
R. Ben Hassen A. Ben Salah A. Daoud T. Jouini 《Journal of chemical crystallography》1994,27(11):657-660
The crystal structure of monomethylammonium monochlorodibromomercurate (II) was refined from single crystal X-ray data including
the fractional contribution of centrosymmetric domains. The refinement converged toR=0.05 in space groupC2. The fraction of structure and its inverse were detected in the refinement. The structure is one-dimensional consisting of
distorted tetrahedra (HgCl2Br2) connected together by chlorine atoms, The CH3NH
3
+
groups are connected to the chains by hydrogen bonds to the halogen atoms contributing to the cohesion of the crystal. 相似文献
76.
R. Ben Hassen A. Ben Salah A. Daoud T. Jouini 《Journal of chemical crystallography》1997,27(11):657-660
The crystal structure of monomethylammonium monochlorodibromomercurate (II) was refined from single crystal X-ray data including the fractional contribution of centrosymmetric domains. The refinement converged toR=0.05 in space groupC2. The fraction of structure and its inverse were detected in the refinement. The structure is one-dimensional consisting of distorted tetrahedra (HgCl2Br2) connected together by chlorine atoms, The CH3NH 3 + groups are connected to the chains by hydrogen bonds to the halogen atoms contributing to the cohesion of the crystal. 相似文献
77.
In this paper, we consider the generalized Weinstein operator $\Delta_{W}^{d,\alpha,n}$, we introduce new Sobolev-Weinstein spaces denoted $\mathscr H_{\alpha,d,n}^{s}(\mathbb{R}_{+}^{d+1}),$ $s\in\mathbb{R},$ associated with the generalized Weinstein operator and we investigate their properties. Next, as application, we study the extremal functions on the spaces $\mathscr H_{\alpha,d,n}^{s}(\mathbb{R}_{+}^{d+1})$ using the theory of reproducing kernels. 相似文献
78.
79.
80.
Numerical and experimental investigations of the dynamics of micromachined shallow arches (initially curved microbeams) and the possibility of using their dynamic snap-through motion for filtering purposes are presented. The considered MEMS arches are actuated by a DC electrostatic load along with an AC harmonic load. Their dynamics is examined numerically using a Galerkin-based reduced-order model when excited near both their first and third natural frequencies. Several simulation results are presented demonstrating interesting jumps and dynamic snap-through behavior of the MEMS arches and their attractive features for uses as band-pass filters, such as their sharp roll-off from pass-bands to stop-bands and their flat response. Experimental work is conducted to test arches realized of curved polysilicon microbeams when excited by DC and AC loads. Experimental data of the micromachined curved beams are shown for the softening and hardening behavior near the first and third natural frequencies, respectively, as well as dynamic snap-through motion. 相似文献