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排序方式: 共有438条查询结果,搜索用时 15 毫秒
1.
Yasumitsu Matsuo Takehiko Ijichi Hironori Yamada Junko Hatori Seiichiro Ikehata 《Central European Journal of Physics》2004,2(2):357-366
We have fabricated a field effect transistor (FET) based on an organic ferroelectric insulator and molecular conductor, and
investigated the electrical properties and memory effects on the PEN-FET. We have observed a drastic change in the drain current
at around the coercive electric fieldE
c
of the organic ferroelectric insulator in not only a FET (PEN-FET) based on a pentacene (PEN) film but also a FET (IPEN-FET)
based on an iodine doped PEN film. The magnitude of the change of the drain current for the IPEN-FET is 200 times larger than
that for the PEN-FET. It is expected from these results that the PEN-FET (especially the IPEN-FET) is an improvement in such
devices, since it operates at a low gate electric field accompanied by the appearance of the spontaneous polarization in the
organic ferroelectric insulator. In addition, we have found that the drain current for the PEN-FET does not return to the
initial drain current ofE
G
=0 V/cm for more than one week, even if the gate electric field is changed to 0 V/cm from 500 V/cm(>E
c
). From these results, it is suggested that the PEN-FET becomes a memory device. 相似文献
2.
A simple method to label oligosaccharides with a multifunctional fluorescent group was developed. Oligosaccharides were quantitatively labeled at their reducing termini with pyrene butanoic acid hydrazide. The pyrene-labeled oligosaccharides were successfully applied to fluorescence polarization measurements and ELISA at picomole quantity, which was not previously reached by other procedures. This labeling method should prove to be useful in a variety of aspects in glycobiology. 相似文献
3.
Infrared and nuclear magnetic resonance (NMR) spectroscopies have been applied for quantitative comparison on unsaturated bonds in tetrafluoroethylene (TFE)-propylene (P)-vinylidene fluoride (VdF) terpolymers. These spectroscopies have led to consistent results while they are based on completely different principles. It is shown that the absolute concentration can be evaluated from NMR measurements. The behavior of unsaturation has been discussed in terms of after-treatment such as wet and dry treatments. The result obtained here can give the important information to improve the performance of fluoroelastomer based on TFE-P-VdF terpolymers. 相似文献
4.
Takarada T Yashiro M Komiyama M 《Chemistry (Weinheim an der Bergstrasse, Germany)》2000,6(21):3906-3913
Oligopeptides are efficiently hydrolyzed by Ce(IV) to the corresponding amino acids under mild conditions. The pseudo first-order rate constants for the hydrolysis of H-Gly-Phe-OH and H-Gly-Gly-OH at pH 7.0 and 50 degrees C are 3.5 x 10(-1) and 2.8 x 10(-1) h(-1), with [Ce(NH4)2(NO3)6]0=10mM (the half-lives are 2.0 and 2.5 h). The catalytic activity of the Ce(IV) is far greater than those of other lanthanide ions and non-lanthanide ions. No oxidative cleavage was observed under the reaction conditions. Catalytic turnover of the Ce(IV) was also evidenced. The hydrolysis is fast especially when the substrates have no metal-coordinating side chains. Tripeptides and tetrapeptides are hydrolyzed at the similar rates as the dipeptides. In the hydrolysis of tripeptides, the amide linkage near the N-terminus is preferentially hydrolyzed. Neither the N-carbobenzyloxy derivative nor the amide of H-Gly-Phe-OH is hydrolyzed to a measurable extent, showing that both the terminal amino group and the carboxylate are coordinated to the Ce(IV) ion. This complexation is further confirmed by 1H NMR spectroscopy. The Ce(IV) ion is therefore one of the most active catalysts for peptide hydrolysis. 相似文献
5.
Matsuda H Murakami T Yashiro K Yamahara J Yoshikawa M 《Chemical & pharmaceutical bulletin》1999,47(12):1725-1729
The aqueous methanolic extract of an Indian natural medicine, the roots of Salacia oblonga Wall. (Celastraceae), was found to show inhibitory activity on the increase in serum glucose level in sucrose- and maltose-loaded rats. The water-soluble and ethyl acetate-soluble portions from the aqueous methanolic extract showed inhibitory activities on alpha-glucosidase and aldose reductase, respectively. From the water-soluble portion, potent alpha-glucosidase inhibitors, salacinol and kotalanol, were isolated, together with nine sugar related components, while a new friedelane-type triterpene, kotalagenin 16-acetate, was isolated from the ethyl acetate-soluble portion along with known diterpenes and triterpenes. The structure of kotalagenin 16-acetate was elucidated on the basis of physicochemical evidence. Principal components from this natural medicine were examined in terms of inhibitory activity on aldose reductase, and the diterpene and triterpene constituents, including the new kotalagenin 16-acetate, were found to be responsible components for the inhibitory activity on aldose reductase. 相似文献
6.
One step syntheses of 3-substituted furans by the reactions of a new reagent, lithium di(3-furyl)cuprate , with various substrates and the application of to a total synthesis of dendrolasin are described. 相似文献
7.
Evaluation of the disintegration time of rapidly disintegrating tablets via a novel method utilizing a CCD camera 总被引:6,自引:0,他引:6
Morita Y Tsushima Y Yasui M Termoz R Ajioka J Takayama K 《Chemical & pharmaceutical bulletin》2002,50(9):1181-1186
Many kinds of rapidly disintegrating or oral disintegrating tablets (RDT) have been developed to improve the ease of tablet administration, especially for elderly and pediatric patients. In these cases, knowledge regarding disintegration behavior appears important with respect to the development of such a novel tablet. Ordinary disintegration testing, such as the Japanese Pharmacopoeia (JP) method, faces limitations with respect to the evaluation of rapid disintegration due to strong agitation. Therefore, we have developed a novel apparatus and method to determine the dissolution of the RDT. The novel device consists of a disintegrating bath and CCD camera interfaced with a personal computer equipped with motion capture and image analysis software. A newly developed RDT containing various types of binder was evaluated with this protocol. In this method, disintegration occurs in a mildly agitated medium, which allows differentiation of minor distinctions among RDTs of different formulations. Simultaneously, we were also able to detect qualitative information, i.e., morphological changes in the tablet during disintegration. This method is useful for the evaluation of the disintegration of RDT during pharmaceutical development, and also for quality control during production. 相似文献
8.
Junko Kuwahara Hideo Akisada Tamaki Kato Norikazu Nishino 《Colloid and polymer science》2005,283(7):747-752
A series of peptides containing various hydrophobic amino acids [methionine (Met), leucine (Leu), norleucine (Nle), phenylalanine (Phe), 2-aminooctanoic acid (Aoc), and 2-aminodecanoic acid (Ade)] were synthesized and their conformations were studied using circular dichroism (CD) spectroscopy in different solvents such as water, methanol, and aqueous solution of ammonium tetradecanesulfonate. Peptides containing hydrophobic amino acids with linear side chains formed -sheets in water and methanol. Electrostatic interaction between the charged side chain (lysine) and a micelle consisting of an anionic surfactant, ammonium tetradecanesulfonate, is necessary for the formation of -helices in micellar environments. The conformational transition from -helix to -sheet structure required moderate hydrophobicity and linear side chains. This conformational transition depended on the surfactant concentration. 相似文献
9.
Kei Yoshida Junko Kusaki Katsunobu Ehara Shiro Saka 《Applied biochemistry and biotechnology》2005,123(1-3):795-806
Japanese beech (Fagus crenata Blume), its cell wall components, and model compounds were treated by supercritical water (380°C, 100 MPa) for 5 s using a batch-type reactor to investigate the production behavior of low molecular weight organic acids. It was found that cellulose and hemicellulose were decomposed to formic acid, pyruvic acid, glycolic acid, acetic acid, and lactic acid, whereas lignin was barely decomposed to such organic acids under the given conditions. However, after prolonged treatment (380°C, 100 MPa, 4 min) of lignin, some organic acids were recovered owing perhaps to the decomposition of the propyl side chain of lignin. It was additionally revealed that the predominant organic acid recovered was acetic acid, which might be derived from the acetyl group of hemicellulose in Japanese beech. 相似文献
10.
Otaka A Yukimasa A Watanabe J Sasaki Y Oishi S Tamamura H Fujii N 《Chemical communications (Cambridge, England)》2003,(15):1834-1835
Gamma-acetoxy-alpha,beta-enoates were easily reduced by samarium diiodide (SmI2) in THF to generate samarium dienolates which were kinetically trapped with ease at their alpha-positions by electrophiles (proton, aldehydes or ketones) to yield (E)-alkene dipeptide isosteres or gamma-amino acid derivatives in high chemical yields. 相似文献