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911.
Sinoj Abraham Larry D. Unsworth 《Journal of polymer science. Part A, Polymer chemistry》2011,49(5):1051-1060
Biomaterials generally suffer from rapid nonspecific protein adsorption, which initiates many deleterious host responses, and complex chemistries that are employed to facilitate cellular interactions. A chemical approach that, based upon current literature, combines a nonfouling architecture with a biomemtic cell‐adhesive end‐group, is presented. Namely, surface‐initiated polymerization of zwitterionic [poly (carboxybetaine methacrylamide)] brushes, with controlled charge densities and phosphonate head groups. Nitroxide mediated free radical polymerization (NMFRP) was employed for various reasons: reduces presence of potentially cytotoxic organometallic catalysts common in atom transfer radical polymerization (ATRP); and it allows a phosphonate end‐group instead of the common brominated end‐group. Thermally oxidized silicon wafers were covalently functionalized with diethyl‐(1‐(N‐(1‐(3‐(trimethoxysilyl)propylcarbamoyl)ethoxy)‐N‐tert‐butylamino)ethyl)phosphonate. NMFRP was used to graft zwitterionic carboxybetaine methacrylamide monomers of varying inter‐charge separation. The resulting thin films were characterized using Attenuated Total Reflectance‐Fourier Transform Infrared (ATR‐FTIR) and X‐ray photoelectron (XPS) spectroscopy, ellipsometry, water contact angle analysis, and thermo gravimetric analysis (TGA). The effect of spacer group on the surface charge density was determined using zeta potential techniques. It is thought that this stratagem will facilitate the ability to tailor systematically both the interior and terminal polymer properties, providing a platform for further understanding how these conditions affect protein adsorption as well as cell‐surface interactions. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2011 相似文献
912.
Hierarchical structure in polymer‐based drug delivery systems as probed by calorimetric measurements
Pascale Valot Nathalie Sintes‐Zydowicz Jean‐Marie Nedelec Mohamed Baba 《Journal of Polymer Science.Polymer Physics》2010,48(18):1939-1945
Thermoporosimetry (TPM), a differential scanning calorimetry technique that relies on the shift of transition temperatures caused by the confinement of liquids, was applied to elucidate the complex morphology of drug‐loaded polymeric microcapsules prepared by the emulsion solvent evaporation method. For the very first time, TPM has been applied simultaneously with two liquids as structural probes. It was found that Miglyol, which dissolves the selected drug (Ibuprofen), is confined inside vesicles having a mean radius of 26.3 nm, whereas water, which is the continuous phase, is trapped inside a swollen polymeric network of Eudragit with an average mesh radius of 1.7 nm. A proposed hierarchical structure is given, which predicts that Eudragit microcapsules are formed from a collection of inert oil vesicles partitioned by polymeric Eudragit membranes swollen by water. © 2010 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 48: 1939–1945, 2010 相似文献
913.
914.
915.
K. V. Kostousov 《Algebra and Logic》2008,47(2):118-124
We point out a countable set of pairwise nonisomorphic Cayley graphs of the group ℤ4 that are limit for finite minimal vertex-primitive graphs admitting a vertex-primitive automorphism group containing a regular
Abelian normal subgroup.
Supported by RFBR grant No. 06-01-00378.
__________
Translated from Algebra i Logika, Vol. 47, No. 2, pp. 203–214, March–April, 2008. 相似文献
916.
Free energies of transfer (ΔGt) of RibonucleaseA (RNaseA) from water to aqueous solutions of urea (4 M, 6 M and 8 M), a protein denaturing solvent as well as ΔGt of RibonucleaseA, β‐Lactoglobulin, α‐Chymotripsin and ChymotrypsinogenA from water to aqueous glycerol (10%, 20%, 30% and 40%), a protein stabilizing solvent has been dissected into cavity term [ΔGt(cav)] and interaction term [ΔGt(int)]. The interaction free energy includes all types of interactions like hard‐soft, hydrogen bonding, electrostatic, etc. The cavity forming free energies have been calculated using the standard version of scaled particle theory (SPT) with well‐reported SPT parameters. It has been found that transfer free energies of cavity terms ΔGt(cav) for native protein from water to urea‐water and water to aqueous glycerol follow almost opposite trends. This primarily indicates there may be some correlation between cavity creation energies and protein denaturing and stabilizing ability of a solvent. The results are in agreement with those obtained from preferential binding coefficient studies in these media. 相似文献
917.
918.
The interposition of surfactants between polymer and liquid crystal (LC) droplets was theoretically predicted by the positive spreading coefficient (0 < λ31) and utilized to interpret the morphology, grating formation kinetics, diffraction efficiency, and switching of the holographic polymer dispersed liquid crystal (HPDLC), prepared from various types (octanoic acid, poly oxyethylene octyl phenyl ether, and perfluoro‐1‐butanesulfonyl fluoride) and amounts (0–9 wt%) of surfactant and molecular weights of polyol (PPG). Regardless of the surfactant type, diffraction efficiency increased with the addition and increasing amount of surfactant, a tendency consistent with increasing value of spreading coefficient, which is determined by the formulations of grating formation. In contrast, diffraction efficiency showed a maximum with the polypropylene glycol (PPG) molecular weight. Surfactant effectively reduced the anchoring energy and electrically drove the film which otherwise was not driven. Overall, surfactant with greater λ31 gave smaller droplet, greater diffraction efficiency, driving voltage, contrast ratio, and smaller response time. Copyright © 2008 John Wiley & Sons, Ltd. 相似文献
919.
Using actions of free monoids and free associative algebras, we establish some Schreier-type formulas involving ranks of actions and ranks of subactions in free actions or Grassmann-type relations for the ranks of intersections of subactions of free actions. The coset action of the free group is used to establish a generalization of the Schreier formula in the case of subgroups of infinite index. We also study and apply large modules over free associative and free group algebras. 相似文献
920.
Kwang Ik KIM Zu Han LIU 《数学学报(英文版)》2008,24(1):75-86
We study the minimizers of the Ginzburg-Landau model for variable thickness, superconducting, thin films with high k, placed in an applied magnetic field hex, when hex is of the order of the "first critical field", i.e. of the order of |lnε|. We obtain the asymptotic estimates of minimal energy and describe the possible locations of the vortices. 相似文献