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81.
Let G be a simply connected Chevalley group of type D
n
, E
n
or G2. In this paper, we show that the minimal representation of G is unique for types D
n
and E
n
and it does not exist for the type G2. 相似文献
82.
Mihaela Singer Dr. 《ZDM》2001,33(6):204-217
Dominating information by formation seems to be the only realistic solution to overcome the crisis generated by the higher and higher accumulation of information in each domain. The paper is proposing a model of building structured knowledge able to generate in the child's mind strategies for efficient processing of information. 相似文献
83.
Karen A. Murphy Jessica M. Eisenhauer Daniel A. Savin 《Journal of Polymer Science.Polymer Physics》2008,46(3):244-252
A series of amphiphilic block copolymers composed of poly(ethylene oxide) and poly(lactide) were synthesized and their solution properties studied using static and dynamic light scattering. These materials self‐assemble in aqueous media with the hydrodynamic radius increasing with increasing hydrophobic fraction in the copolymer. To ascertain the potential for use of these materials as degradable coatings in delivery applications, block copolymers of varying compositions were adsorbed onto a series of colloidal polystyrene particles with varying radii, and the thickness of the adsorbed layer was determined from changes in the hydrodynamic size. The adlayer thicknesses ranged from 3 to 14 nm with varying block copolymer compositions, and colloid radii. The trends fit well with theoretical models for adlayer thickness, with the exception of the smallest colloids. In these systems, we propose that the colloids may become encapsulated into the block copolymer assembly. © 2007 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 46: 244–252, 2008 相似文献
84.
85.
Mihaela Frunza Gabriela Lisa M. I. Popa N. D. Miron Denisa Ileana Nistor 《Journal of Thermal Analysis and Calorimetry》2008,93(2):373-379
The thermal behavior of the new inorganic-organic nanohybrid materials obtained by intercalation of chloramphenicol and salicylate
into layered double hydroxides (LDHs) by direct synthesis method, anion exchange reaction and the reconstruction method was
evaluated by dynamic thermogravimetric analysis in air, at heating rates of 5°C min−1. The XRD patterns of the samples are characteristic for those of well crystallized solids with layered double hydroxide structures.
The FTIR spectroscopy results show the presence of the organic compound within the network structure of the synthesized LDHs.
The kinetic parameters (reaction order (n) apparent activation energy (E
a) and pre-exponential factor (lnA) were calculated by the Coats-Redfern method. The compensation effects were determined. 相似文献
86.
Afonin A. G. Baranov V. T. Barnov E. V. Britvich G. I. Lobanov I. S. Poluektov I. V. Reshetnikov S. F. Savin D. A. Sandomirskiy Yu. E. Smaglyuk D. S. Terekhov V. I. Chesnokov M. Yu. Chesnokov Yu. A. Chirkov P. N. Yanovich A. A. 《JETP Letters》2021,113(4):226-230
JETP Letters - In view of the successful experience in the generation of pion and kaon secondary beams using a focusing crystal, it has been proposed to build at the U-70 accelerator a new-type... 相似文献
87.
88.
Electropolymerization of a new phenothiazine derivative (bis-phenothiazin-3-yl methane, BPhM) on glassy carbon electrodes
leads to electroactive and conducting layers of poly-BPhM. Based on the Laviron method, the kinetic parameters (the heterogeneous
electron transfer rate constants k
s and transfer coefficients α) were calculated out of the experimental and theoretical data. The theoretical data have been
obtained by using the analogical modelling and numerical simulating method. The modified electrodes present high values of
k
s(~50s−1) in phosphate buffer solutions of different pH values. A good correlation of mathematical and numerical simulated kinetic
parameters has been obtained, with the experimental values and the norm of residuals being very close to zero. 相似文献
89.
Cimpoiu C Hosu A Seserman L Sandru M Miclaus V 《Journal of separation science》2010,33(23-24):3794-3799
The aim of this paper is to develop a new simple, fast and economical method for simultaneous quantitative determination of methylxanthine compounds based on TLC combined with image analysis. To obtain certain results, both extraction and chromatographic separation were optimized. The optimum extraction conditions were maceration in ethanol-water 8:2, v/v. The chromatographic separations were done on the silica gel F(254) TLC plates developed with chloroform-dichloromethane-isopropanol, 4:2:1 v/v/v. Detection was performed under UV lamp at 254?nm and the evaluation of the chromatographic plate was based on digital processing of chromatographic images. The developed TLC method was validated for parameters such as specificity, linearity and range, LOD and LOQ, precision, robustness and accuracy. This method was then applied for determination of caffeine, theobromine and theophylline in different types of tea, commercially available. Moreover, the content of methylxanthines detected and determined in commercial tea samples can be used as chemical marker in quality control. 相似文献
90.
Silver meso- and rac-tartrate and silver squarate have been synthesized, and the crystal structure of a new polymorph of the latter is reported.
Three reaction products of these silver salts with pyrazine have been obtained and structurally characterized: From silver
squarate, a chain polymer with linear coordination of Ag(I) by two pyrazine ligands is formed, whereas the silver tartrates
yield solids in which the inner coordination sites around the metal are only partially occupied by N donors; in contrast to
expectation, oxygen coordination prevails. All the four new Ag(I) coordination compounds reported show high packing coefficients
in the range between 0.789 and 0.885. In order to put these results into a meaningful context, packing coefficients for the
crystal structures of almost 30,000 compounds retrieved from the Cambridge Structural Database have been determined. Tartrates
pack significantly closer than pyrazine complexes or metal-containing compounds in general. The exceptionally high packing
coefficient of the new polymorph of silver squarate is due to stacking of anions and concomitant Ag···Ag contacts, both along
the shortest lattice parameter which amounts to only 3.3990(9) ?. 相似文献