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排序方式: 共有187条查询结果,搜索用时 9 毫秒
111.
112.
the anomalous part of the specific heat capacity and hte isobaric thermal expansion coefficient of nematic liquid crystals above the transition point are calculated on the basis of the continuum fluctuation theory of de Gennes. 相似文献
113.
Existence of a regular unimodular triangulation of the configuration
, where + is the collection of the positive roots of a root system
and where (0, 0,...,0 ) is the origin of
, will be shown for = B
n
, C
n
, D
n
and BC
n
. Moreover, existence of a unimodular covering of a certain subconfiguration of the configuration A
n+1
+ will be studied. 相似文献
114.
Ihara T Hayamizu Y Yoshita M Akiyama H Pfeiffer LN West KW 《Physical review letters》2007,99(12):126803
Low-temperature photoluminescence-excitation spectra are studied in an n-type modulation-doped T-shaped single quantum wire with a gate to tune electron densities. With a nondegenerate one-dimensional (1D) electron gas, the band-edge absorption exhibits a sharp peak structure induced by the 1D density of states. When the dense 1D electron gas is degenerate at a low temperature, we observe a Fermi-edge absorption onset without many-body modifications. 相似文献
115.
Hayamizu Y Yoshita M Takahashi Y Akiyama H Ning CZ Pfeiffer LN West KW 《Physical review letters》2007,99(16):167403
Optical gain and the Mott transition in GaAs quantum wires were studied via simultaneous measurements of absorption and photoluminescence (PL). We observed well-separated PL peaks assigned to excitons (X) and biexcitons (XX) even at densities where optical gain existed. A sharp optical gain first appeared when the XX peak overtook the X peak, indicating the gain origin of biexciton-exciton population inversion. The XX peak eventually changed to a broad peak of plasma, and a broad gain due to plasma was observed as the Mott transition was completed. 相似文献
116.
Matsui S Masumoto H Hashimoto T 《Journal of magnetic resonance (San Diego, Calif. : 1997)》2007,186(2):238-242
We propose a method of slice selection in solid-state MRI by combining DANTE selective excitation with magic-echo (ME) line narrowing. The DANTE RF pulses applied at the ME peaks practically do not interfere with the ME line narrowing in the combined ME DANTE sequence. This allows straightforward tailoring of the slice profile simply by introducing an appropriate modulation, such as a sinc modulation, into the flip angles of the applied DANTE RF pulses. The utility of the method has been demonstrated by preliminary experiments performed on a test sample of adamantane. 相似文献
117.
Ando Y Niwa K Yamada N Irie T Enomoto T Kubota H Ohmiya Y Akiyama H 《Photochemistry and photobiology》2007,83(5):1205-1210
We have developed a bio/chemiluminescence spectrometer with a cooled charge-coupled-device (CCD) detector to obtain a quantitative luminescence spectrum as the absolute number of all emitted photons at each wavelength. The integrated area of the spectrum divided by the number of reacted substrate molecules gives the quantum yield. Calibration of the absolute sensitivity of the CCD-spectrometer system was performed by using lasers and a tungsten lamp with calibrated powers as primary light standards, and calibration of the light-collection efficiency of the spectrometer with several kinds of cells for liquid samples was achieved by introducing a simple reference double-plate cell. The reference cell is not convenient for final bio/chemiluminescence measurements but is useful for the calibration because it has well-defined angular dependence of light emission, allowing accurate calculation of the light-collection efficiency. Using this CCD-spectrometer system, we re-examined the quantum yield of aqueous luminol chemiluminescence with H2O2 catalyzed by horseradish peroxidase. The quantum yield was constant for a wide range of luminol concentrations, whereas it changed and had an optimum against H2O2 concentrations. The optimum quantum yield was 1.23(+/-0.20)%, which is in good agreement with previously reported values. 相似文献
118.
Hiroyuki Hamazaki Takayuki Abe Hidefumi Yamakawa Tomoyuki Yokota Shiro Shigeta Hiroshi Takaku 《Helvetica chimica acta》2002,85(7):2183-2194
We have demonstrated that a new type of circular dumbbell RNA/DNA chimeric oligonucleotide (CDRDON) with two closed nucleotide or alkyl loop structures (hexa‐ethylene glycol) inhibits influenza virus A replication in MDCK cells. The enzymatic synthesis of circular dumbbell RNA/DNA chimeric oligonucleotides was achieved by enzymatically ligating a self‐complementary phosphorylated oligonucleotide with T4‐RNA ligase. The CDRDON‐Al, with two closed alkyl loop structures, showed higher nuclease resistance, hybridization, and cellular uptake than the anti‐S‐ODN and the CDRDON, with two closed nucleotide hairpin‐loop structures. The circular dumbbell RNA/DNA chimeric oligonucleotide (CDRDON‐Al‐PB2‐as), containing an AUG initiation‐codon sequence as the target of PB2, showed highly inhibitory effects on influenza A virus RNA expression. The limited toxicity of unmodified phosphodiester oligonucleotides and the sequence‐specific binding to target mRNA indicate that circular dumbbell RNA/DNA chimeric phosphodiester oligonucleotides can be used with intact cells, and may prevent viral replication in culture. 相似文献
119.
Masaya Kitamura Kiminori Kawakami Naotoshi Nakamura Kouhei Tsumoto Hidefumi Uchiyama Yoshitaka Ueda Izumi Kumagai Tadao Nakaya 《Journal of polymer science. Part A, Polymer chemistry》1999,37(6):729-736
An expression system for a chemically synthesized gene, encoding a model peptide of marine mussel adhesive protein, was constructed in Escherichia coli under regulation of the T7‐promoter. The model peptide consisted of six repeats of the decapeptide AKPSYPPTYK. Although the product was expressed as an inclusion body, we were able to solubilize it successfully, using acetic acid. The higher‐order structure of this model peptide was investigated using CD spectroscopy and NMR spectroscopy. Using the modified enzyme, mushroom tyrosinase, the tyrosine residue was hydroxylated to 3,4‐dihydoxyphenylalanine (Dopa), and the resulting modified peptide was polymerized, solidified, and insolubilized spontaneously. © 1999 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 37: 729–736, 1999 相似文献
120.
Hidefumi Hirai Yukihide Shiraishi Kazuhiro Saito 《Macromolecular rapid communications》1995,16(1):31-34
The selective carboxylation of 4-biphenylcarboxylic acid with carbon tetrachloride in aqueous alkali to obtain 4,4′-biphenyldicarboxylic acid was achieved by the use of ß-cyclodextrin and copper powder II under mild conditions. 相似文献