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排序方式: 共有196条查询结果,搜索用时 46 毫秒
91.
New polyazomethines have been synthesized based on polynuclear dihydroxy quinones (5,8-dihydroxy-1,4-naphthoquinone and 1,4-dihydroxyanthraquinone) and siloxane diamines differing by the siloxane sequence length (1,3-bis(3-aminopropyl)tetramethyldisiloxane and α,ω-bis(3-aminopropyl)oligodimethylsiloxane having about 12 siloxane units/sequence). The structures were verified by spectral analyses. Solubility tests, GPC and viscosity measurements were performed. Some properties of the resulted polymers were investigated by thermal (TGA and DSC), electrical, spectral (UV-Vis) and electrochemical (differential pulse voltammetry) methods. 相似文献
92.
We present an analytical model of Stokes creeping flows in rectangular cavities. In the model, the fluid normal velocity at the wall is zero, while the fluid tangential velocity at the wall differs from the wall velocity. Numerical work is used to validate some of the ideas generated from this realizable model. 相似文献
93.
Elena Badea Giuseppe Della Gatta Petru Budrugeac 《Journal of Thermal Analysis and Calorimetry》2011,104(2):495-506
Our recent developments concerning the assessment of parchments deterioration using DSC are reported. Measurements performed
on samples in excess water conditions, in static air and gas flow provided qualitative and quantitative information on parchment
ageing and deterioration at microscopic and mesoscopic level, when assembly of fibres/fibrils is weakened, partially and eventually
completely lost, and at molecular level, when triple helix uncoiling occurs. A damage ranking scale based on a large collection
of DSC parameters obtained by investigating artificially aged samples was set up. Deconvolution of the DSC thermal denaturation
peaks in excess water enabled evaluating and discriminating stability of parchments with similar damage levels. Further experimental
evidences such as softening of the crystalline fraction of collagen, thermal-oxidation and collagen gelatinisation were detected
by DSC measurements in gas flow and static air, and related to specific deterioration patterns. DSC measurement of wet samples
provided an objective and reliable method for evaluating parchment shrinkage temperature overcoming the limitations of conventional
methods. 相似文献
94.
Zuzana Hricovíniová Miloš Hricovíni Ladislav Petruš 《Journal of carbohydrate chemistry》2013,32(7):827-836
ABSTRACT 2-C-(Hydroxymethyl)-D-erythrose (2) and 2-C-(hydroxymethyl)-D-threose (4) have been stereospecifically synthesized in one-step by a molybdic acid-catalysed isomerization reaction from respective D-xylulose (1) and D-ribulose (3). In the case of interconversion of 1 to 2, the content of the 2-C-branched chain tetrose in the equilibrium mixture can be doubled if boric acid is present in the reaction mixture in addition to the catalyst. 相似文献
95.
96.
We consider the Sobolev space $X = W^{s,p} \left( {\mathbb{S}^m ;\mathbb{S}^{k - 1} } \right)$ . We prove the existence of a robust distributional Jacobian Ju for u ∈ X, provided sp ≥ k ? 1; this generalizes a result of Bourgain, Brezis, and the second author [10] dealing with the case m = k. We identify the image of the map X ? u ? Ju in the critical case sp = k ? 1. This extends a result of Alberti, Baldo, and Orlandi [2] for s = 1 and p = k ? 1. We also present a new, analytical, dipole construction method. 相似文献
97.
Let Ω be a smooth bounded simply connected domain in R2. We investigate the existence of critical points of the energy Eε(u)=1/2∫Ω|∇u|2+1/(4ε2)∫Ω(1−|u|2)2, where the complex map u has modulus one and prescribed degree d on the boundary. Under suitable nondegeneracy assumptions on Ω, we prove existence of critical points for small ε. More can be said when the prescribed degree equals one. First, we obtain existence of critical points in domains close to a disk. Next, we prove that critical points exist in “most” of the domains. 相似文献
98.
O. Petru Balaj Christian B. Berg Stephan J. Reitmeier Vladimir E. Bondybey Martin K. Beyer 《International journal of mass spectrometry》2009,279(1):5-9
A novel design for a temperature-controlled ICR cell is described for use in black-body infrared radiative dissociation (BIRD) studies of weakly bound systems like water clusters. Due to several improved design features, it provides a very uniform black-body radiation environment, and at the same time maintains efficient pumping for a low collision rate on the order of 10?2 s?1. At the lowest temperatures reached, nominally 89 K cell plate temperature, water evaporation effectively ceases, while intracluster reactions in V+(H2O)n with a small activation energy are still observed. BIRD rate constants for Ag+(H2O)n, n = 4–6, are shown in the temperature range T = 160–320 K. For n = 6, a linear Arrhenius plot with R2 = 0.9943 is obtained without any calibration, confirming the suitability of the cell for quantitative BIRD studies. 相似文献
99.
Wutiphol Sintunavarat Adrian Petru?el Poom Kumam 《Rendiconti del Circolo Matematico di Palermo》2012,61(3):361-383
In this paper, we show that the mixed $g$ -monotone property in coupled coincidence point theorems can be replaced by generalized property. Hence, these results can be applied in a much wider class of problems. We also study the condition for the uniqueness of a common coupled fixed point and give some example of nonlinear contraction mappings where the existence of the common coupled fixed point cannot be obtained by the mixed monotone property, but it follows by our results. At the end of this paper, we give an open problems for further investigation. 相似文献
100.
Höckendorf RF Hao Q Sun Z Fox-Beyer BS Cao Y Balaj OP Bondybey VE Siu CK Beyer MK 《The journal of physical chemistry. A》2012,116(15):3824-3835
The chemistry of (H(2)O)(n)(?-), CO(2)(?-)(H(2)O)(n), and O(2)(?-)(H(2)O)(n) with small sulfur-containing molecules was studied in the gas phase by Fourier transform ion cyclotron resonance mass spectrometry. With hydrated electrons and hydrated carbon dioxide radical anions, two reactions with relevance for biological radiation damage were observed, cleavage of the disulfide bond of CH(3)SSCH(3) and activation of the thiol group of CH(3)SH. No reactions were observed with CH(3)SCH(3). The hydrated superoxide radical anion, usually viewed as major source of oxidative stress, did not react with any of the compounds. Nanocalorimetry and quantum chemical calculations give a consistent picture of the reaction mechanism. The results indicate that the conversion of e(-) and CO(2)(?-) to O(2)(?-) deactivates highly reactive species and may actually reduce oxidative stress. For reactions of (H(2)O)(n)(?-) with CH(3)SH as well as CO(2)(?-)(H(2)O)(n) with CH(3)SSCH(3), the reaction products in the gas phase are different from those reported in the literature from pulse radiolysis studies. This observation is rationalized with the reduced cage effect in reactions of gas-phase clusters. 相似文献