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排序方式: 共有219条查询结果,搜索用时 46 毫秒
1.
Shin SatohIwao Matsuyama 《Journal of Non》2002,306(3):300-308
Tantalum-doped silica glass was fabricated by the sol-gel process in order to obtain a glass with a high refractive index for optical use. A crack-free, clear glass rod was successfully prepared from a low-density gel and used as the core material for fabricating optical fibers. Transmission loss in the fabricated fibers was high, in the range of 103-104 dB/km, which may be caused by coloration due to the multivalency of tantalum; however, the loss was reduced by nearly one order of magnitude by heat treatment at 800 °C, that is, to 75 dB/km at a wavelength of 0.8 μm. 相似文献
2.
3.
The average interelectronic is the expectation value of the angle thetaij (0 < or = thetaij < or = pi) subtended by the position vectors ri and rj of a pair of electrons i and j. In the Hartree-Fock theory of atoms, we point out that the angle and its subshell-pair components nl,n'l' are bounded from above and below, where n and l are the principal and azimuthal quantum numbers. The upper bounds for nl,n'l' with 0 < or = l, l' < or = 3 are 9pi/16 (=101.25 degrees), 135pi/256 (approximately 94.922 degrees), 265pi/512 (approximately 93.164 degrees), and 129pi/256 (approximately 90.703 degrees) for sp, pd, df, and sf pairs, respectively, while they are pi/2 (=90 degrees ) for the other ll' pairs, independent of n and n'. A weighted sum of these subshell-pair bounds gives an upper bound to . The lower bounds are pi/2 in all the cases. 相似文献
4.
Sphingomyelinase (SMPLC) from Bacillus cereus was modified with a polyethylene glycol (PEG) derivative, methoxypolyethylene glycol-succinimidyl succinate (ss-PEG). The molecular weight of the ss-PEG-modified SMPLC was calculated to be approx. 150 kDa by gel-filtration whereas that of the native enzyme, was 25 kDa. By this modification, the enzyme increased its thermostability and retained its hydrolytic activity toward 2-(N-hexadecanoylamino)-4-nitrophenylphosphocholine (HNP) and sphingomyelin (SM) in the mixed micelles with the surfactants such as Triton X-100 and sodium deoxycholate (SDC). However, the activity toward liposomal SM was significantly decreased, and all the enzyme activities toward bovine erythrocytes, including membraneous SM-hydrolyzing and hemolytic activities as well as the enzyme adsorption onto the erythrocyte membranes, were completely lost. 相似文献
5.
6.
For 357 subshells of the 53 neutral atoms He through Xe in their ground states, the two-electron intracule (relative motion)
<u
k
>
nl
and extracule (center-of-mass motion) <R
k
>
nl
subshell moments in position space are examined as well as their counterparts <v
k
>
nl
and <P
k
>
nl
in momentum space, where n and l are the principal and azimuthal quantum numbers of the atomic subshell, respectively. It is clarified that between the intracule
and extracule moments the “2
k
-rule” is strictly valid, which means <u
k
>
nl
= 2
k
<R
k
>
nl
and <v
k
>
nl
= 2
k
<P
k
>
nl
for any nl subshell. Theoretical analysis also proves that for a particular case of k = +2, two relations <u
2>
nl
= (N
nl
−1)<r
2>
nl
and <v
2>
nl
= (N
nl
−1)<p
2>
nl
hold exactly, where N
nl
(≥2) is the number of electrons in the subshell nl, and <r
k
>
nl
and <p
k
>
nl
are the familiar one-electron subshell moments in position and momentum spaces, respectively. The latter equality establishes
a new and rigorous relation between the second electron-pair moments in momentum space and the total energy of an atom through
the virial theorem. For k=+1, −1, and −2, the numerical Hartree-Fock results for the 357 subshells show that there are approximate but accurate linear
relations between <u
k
>
nl
and <r
k
>
nl
and between <v
k
>
nl
and <p
k
>
nl
, in which the proportionality constant in each space depends on n,l, and k.
Received: 27 April 1998 / Accepted: 29 May 1998 / Published online: 28 August 1998 相似文献
7.
Motohisa Kaneko Akio Matsuyama Chikayoshi Nagata 《Photochemistry and photobiology》1978,27(3):359-361
Abstract. Photodimerization of thymine in aqueous solution in the presence of tyrosine was studied with monochromatic UV irradiation. The total dimer formation was sensitized in the presence of tyrosine. The action spectrum of sensitized total dimer formation has a peak near 280 nm corresponding to the absorption maximum of tyrosine. Triplet quenchers reduced the sensitization substantially. It seems probable that tyrosine-sensitized photodimerization of thymine occurred via triplet-triplet energy transfer from tyrosine to thymine. 相似文献
8.
Crystal structures of the silver complexes derived from tetrabenzo[16]annulene with AgOTf and AgClO(4) are different, although these two complexes show similar (1)H NMR spectra reflecting a similar clathrate structure in solution. The silver complex of pentabenzo[20]annulene with AgClO(4) adopts a clathrate structure both in the solid state and in solution. 相似文献
9.
A membrane having an amine moiety was prepared by plasma-grafting 2-(N,N-dimethyl)aminoethyl methacrylate (DAMA) onto a microporous polyethylene substrate. Permselectivity of the membrane for CO2 over N2 was achieved in both dry and water swollen conditions. When the CO2 partial pressure in the feed gas was 0.047 atm, the selectivity of CO2 over N2 reached 130 for the highly swollen water containing membrane. This value was found to agree with that obtained with a mobile carrier membrane (supported liquid membrane) using DAMA as the carrier. The effects of several experimental conditions such as degree of grafting, feed partial pressure and temperature on the membrane performance were studied. It was suggested that the membrane acted as a fixed carrier membrane for CO2 facilitated transport in under the dry condition and acted as a fixed reaction site membrane in the water swollen condition. The carrier transport mechanism is discussed for dry and aqueous membranes. 相似文献
10.
Okuma K Koga Y Kojima K Shioji K Matsuyama H Yokomori Y 《The Journal of organic chemistry》2000,65(7):2090-2095
Selenobenzophenone reacts as a diene with dimethyl acetylenedicarboxylate (DMAD) to lead to dimethyl 1H-1-diphenylmethyl-1-phenyl-2-benzoselenopyran-3,4-dicarboxylate (5c) in moderate yield; the initial [4 + 2] cycloaddition is followed by the addition of another 1 mol equiv of selenobenzophenone. The reaction might proceed through carbene insertion of the primary cycloadduct. On the other hand, 4,4'-dimethoxyselenobenzophenone combines as a diene with DMAD furnishing dimethyl 1H-1-p-methoxyphenyl-6-methoxy-2-benzoselenopyran-3,4-dicarboxylate (4a). The reaction of benzoselenopyran derivative (4) with diaryldiazomethanes afforded another type of carbene insertion product. 相似文献