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排序方式: 共有338条查询结果,搜索用时 203 毫秒
331.
Ivopoulos P Sotiropoulou M Bokias G Staikos G 《Langmuir : the ACS journal of surfaces and colloids》2006,22(22):9181-9186
Comb-type copolymers of poly(acrylic acid) grafted with poly(2-acrylamido-2-methylpropanesulfonic acid) (PAMPSA) side chains form with poly(ethylene glycol), at low pH, water-soluble hydrogen-bonding interpolymer complexes. Turbidimetry, viscometry, and dynamic light scattering measurements suggest that compact, negatively charged, colloidal nanoparticles are formed at pH<3.75. The influence of the structure of the graft copolymers and of the ionic strength of the solution on the size of these nanoparticles was investigated. It was found that their hydrodynamic radius decreases by increasing the molecular mass of the PAMPSA side chains of the graft copolymer and increases with increasing the ionic strength of the solution. 相似文献
332.
We have performed a variety of high-level electronic structure calculations on two moderately sized organic molecules and found considerable sensitivity of the intramolecular potential energy surface to the method employed. The gas-phase structure of tyrosine-glycine varies qualitatively between B3LYP and MP2 optimizations, producing different close contacts between the tyrosine ring and the glycine moiety. The relative energies of the 2-(acetylamino)benzamide conformations found in its two polymorphs can vary by over 20 kJ mol-1 between MP2 and B3LYP calculations, using the same basis set. It is shown by a novel analysis that the intramolecular equivalent of basis set superposition error competes with the errors in the intramolecular dispersion in causing this sensitivity. 相似文献
333.
Lancaster RW Karamertzanis PG Hulme AT Tocher DA Covey DF Price SL 《Chemical communications (Cambridge, England)》2006,(47):4921-4923
A computational prediction that mixing the synthetic mirror image of progesterone with its natural form would produce a specific racemic crystal structure was validated. 相似文献
334.
Panagiotis Sidiropoulos Nikos Nikolaidis Ioannis Pitas 《Chaos, solitons, and fractals》2009,42(5):2667-2674
Fragile watermarking is a popular method for image authentication. In such schemes, a fragile signal that is sensitive to manipulations is embedded in the image, so that it becomes undetectable after any modification of the original work. Most algorithms focus either on the ability to retrieve the original work after watermark detection (invertibility) or on detecting which image parts have been altered (localization). Furthermore, the majority of fragile watermarking schemes suffer from robustness flaws. We propose a new technique that combines localization and invertibility. Moreover, watermark dependency on the original image and the non-linear watermark embedding procedure guarantees that no malicious attacks will manage to create information leaks. 相似文献
335.
Nikolaos Panagiotis Souris 《Mathematische Nachrichten》2023,296(6):2609-2625
We study the geodesic equation for compact Lie groups G and homogeneous spaces , and we prove that the geodesics are orbits of products of one-parameter subgroups of G, provided that a simple algebraic condition for the Riemannian metric is satisfied. For the group , we relate this type of geodesics to the free motion of a symmetric top. Moreover, by using series of Lie subgroups of G, we construct a wealth of metrics having the aforementioned type of geodesics. 相似文献
336.
337.
Dimitra Kourti Anastasia Kanioura Theodore Manouras Maria Vamvakaki Panagiotis Argitis Margarita Chatzichristidi Sotirios Kakabakos Panagiota Petrou 《Macromolecular bioscience》2023,23(1):2200301
Surfaces for guided cell adhesion and growth are indispensable in several diagnostic and therapeutic applications. Towards this direction, four diblock copolymers comprising polyethylene glycol (PEG) and poly(2-tetrahydropyranyl methacrylate) (PTHPMA) are synthesized employing PEG macroinitiators of different chain lengths. The copolymer with a 5000 Da PEG block and a PEG-PTHPMA comonomers weight ratio of 43–57 provides a film with the highest stability in the culture medium and the strongest cell repellent properties. This copolymer is used to develop a positive photolithographic material and create stripe patterns onto silicon substrates. The highest selectivity regarding smooth muscle cell adhesion and growth and the highest fidelity of adhered cells for up to 3 days in culture is achieved for stripe patterns with widths between 25 and 27.5 µm. Smooth muscle cells cultured on such patterned substrates exhibit a decrease in their proliferation rate and nucleus area and an increase in their major axis length, compared to the cells cultured onto non-patterned substrates. These alterations are indicative of the adoption of a contractile rather than a synthetic phenotype of the smooth muscle cells grown onto the patterned substrates and demonstrate the potential of the novel photolithographic material and patterning method for guided cell adhesion and growth. 相似文献