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For the first time a comparative study of holographic recording in planarly oriented films of nematic and cholesteric azobenzene-containing polymers was performed. The influence of temperature and light intensity on the values of diffraction efficiencies of holographic gratings was investigated. The kinetics of grating relaxation at different temperatures was studied. It was shown that the helical supramolecular structure of cholesteric copolymer causes a significant decrease of the diffraction efficiency in comparison with the one observed for the nematic state of the homopolymer. 相似文献
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Yi Liu David D. Díaz Adrian A. Accurso K. Barry Sharpless Valery V. Fokin M. G. Finn 《Journal of polymer science. Part A, Polymer chemistry》2007,45(22):5182-5189
1,2,3‐Triazole‐based polymers generated from the Cu(I)‐catalyzed cycloaddition between multivalent azides and acetylenes are effective adhesive materials for metal surfaces. The adhesive capacities of candidate mixtures of azide and alkyne components were measured by a modified peel test, using a customized adhesive tester. A particularly effective tetravalent alkyne and trivalent azide combination was identified, giving exceptional strength that matches or exceeds the best commercial formulations. The addition of Cu catalyst was found to be important for the synthesis of stronger adhesive polymers when cured at room temperature. Heating also accelerated curing rates, but the maximum adhesive strengths achieved at both room temperature and high temperature were the same, suggesting that crosslinking reaches the same advanced point in all cases. Polytriazoles also form adhesives to aluminum, but copper is bound more effectively, presumably because active Cu(I) ions may be leached from the surface to promote crosslinking and adhesion. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 5182–5189, 2007 相似文献
5.
Experimental measurements of Tg for two series of lower homologues of polyethyleneoxide. differing in their end-groups, are discussed in terms of existing theories. Simple free-volume considerations predicting linear dependence of Tg on (molecular weight)?1 are inadequate in systems with end-groups capable of specific interactions (hydrogen bonding). Thermodynamic arguments show that the true Tg of infinitely long PEO chain is 220 ± 5°K. Suitable modification of parameters of the Gibbs-DiMarzio equations to account for the dependence of the free volume fraction on the concentration of end-groups results in good fit of the experimental data for hydroxyl-terminated samples and correctly predicts Tg(∞). Analysis of the data for chlorine-substituted oligomers suggests the existence of specific intermolecular interactions in the latter, involving chlorine atoms. 相似文献
6.
The soliton dressing matrices for the higher-order zeros of the Riemann–Hilbert problem for the N -wave system are considered. For the elementary higher-order zero, that is, whose algebraic multiplicity is arbitrary but the geometric multiplicity is 1, the general soliton dressing matrix is derived. The theory is applied to the study of higher-order soliton solutions in the three-wave interaction model. The simplest higher-order soliton solution is presented. In the generic case, this solution describes the breakup of a higher-order pumping wave into two higher-order elementary waves, and the reverse process. In non-generic cases, this solution could describe (i) the merger of a pumping sech wave and an elementary sech wave into two elementary waves (one sech and the other one higher order); (ii) the breakup of a higher-order pumping wave into two elementary sech waves and one pumping sech wave; and the reverse processes. This solution could also reproduce fundamental soliton solutions as a special case. 相似文献
7.
Paul Valery A. Bressler 《Compositio Mathematica》2003,135(3):245-278
We consider a fan as a ringed space (with finitely many points). We develop the corresponding sheaf theory and functors, such as direct image R* ( is a subdivision of a fan), Verdier duality, etc. The distinguished sheaf
, called the minimal sheaf plays the role of an equivariant intersection cohomology complex on the corresponding toric variety (which exists if is rational). Using
we define the intersection cohomology space IH(). It is conjectured that a strictly convex piecewise linear function on acts as a Lefschetz operator on IH(). We show that this conjecture implies Stanley's conjecture on the unimodality of the generalized h-vector of a convex polytope. 相似文献
8.
Oleg G. Salnikov Kirill V. Kovtunov Danila A. Barskiy Valery I. Bukhtiyarov Robert Kaptein Igor V. Koptyug 《Applied magnetic resonance》2013,44(1-2):279-288
Parahydrogen-induced polarization has been successfully used for a kinetic study of propylene hydrogenation over a Pt/Al2O3 catalyst. It was shown that the reaction orders with respect to hydrogen are different for the pairwise and the non-pairwise hydrogen addition and are equal to 0.7 and 0.1, respectively. This observation of different reaction orders confirms the coexistence of different types of active sites which are responsible for the overall and the pairwise hydrogen addition to the propylene C=C double bond. Moreover, 0.7 reaction order with respect to H2 for pairwise hydrogen addition indicates that the contribution of pairwise addition depends on the concentration of molecular hydrogen. Therefore, this observation can be developed into a practical tool for producing fluids with highly polarized nuclear spins by changing the hydrogen concentration. 相似文献
9.
Marta Saiz-Viv Adrin Colomer Carles Fonfría Luis Martí-Bonmatí Valery Naranjo 《Entropy (Basel, Switzerland)》2021,23(7)
Atrial fibrillation (AF) is the most common cardiac arrhythmia. At present, cardiac ablation is the main treatment procedure for AF. To guide and plan this procedure, it is essential for clinicians to obtain patient-specific 3D geometrical models of the atria. For this, there is an interest in automatic image segmentation algorithms, such as deep learning (DL) methods, as opposed to manual segmentation, an error-prone and time-consuming method. However, to optimize DL algorithms, many annotated examples are required, increasing acquisition costs. The aim of this work is to develop automatic and high-performance computational models for left and right atrium (LA and RA) segmentation from a few labelled MRI volumetric images with a 3D Dual U-Net algorithm. For this, a supervised domain adaptation (SDA) method is introduced to infer knowledge from late gadolinium enhanced (LGE) MRI volumetric training samples (80 LA annotated samples) to a network trained with balanced steady-state free precession (bSSFP) MR images of limited number of annotations (19 RA and LA annotated samples). The resulting knowledge-transferred model SDA outperformed the same network trained from scratch in both RA (Dice equals 0.9160) and LA (Dice equals 0.8813) segmentation tasks. 相似文献
10.
Yubing Dong Amand Faessler Thomas Gutsche Valery E. Lyubovitskij 《Few-Body Systems》2013,54(7-10):1011-1014
The new resonances X(3872) and Λ c (2940) are considered as weakly bound states of other hadrons in a molecule scenario using phenomenological Lagrangians. 相似文献