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991.
992.
A general and efficient methodology has been developed to prepare the C4-substituted dipeptide reverse-turn mimetics unsaturated (9a, 10a) and saturated (11a) azabicyclo[4.3.0] alkane amino acid derivatives. The side chain was introduced by bromination of dehydroamino acid intermediates followed by Suzuki coupling. Hydrogenation of the bicyclic dehydroamino acid 9a afforded saturated bicyclic lactam 11a. This approach can be further explored for the synthesis of a variety of such beta-turn mimetics with aryl and alkyl side chain functionalities. [reaction: see text] 相似文献
993.
Guo JH Luo Y Augustsson A Rubensson JE Såthe C Agren H Siegbahn H Nordgren J 《Physical review letters》2002,89(13):137402
We use x-ray emission spectroscopy to examine the influence of the intermolecular interaction on the local electronic structure of liquid water. By comparing x-ray emission spectra of the water molecule and liquid water, we find a strong involvement of the a(1)-symmetry valence-orbital in the hydrogen bonding. The local electronic structure of water molecules, where one hydrogen bond is broken at the hydrogen site, is separately determined. Our results provide an illustration of the important potential of x-ray emission spectroscopy for elucidating basic features of liquids. 相似文献
994.
Kubo K Akemoto M Anderson S Aoki T Araki S Bane KL Blum P Corlett J Dobashi K Emma P Frisch J Fukuda M Guo Z Hasegawa K Hayano H Higo T Higurashi A Honda Y Iimura T Imai T Jobe K Kamada S Karataev P Kashiwagi S Kim E Kobuki T Kotseroglou T Kurihara Y Kuriki M Kuroda R Kuroda S Lee T Luo X McCormick DJ McKee B Mimashi T Minty M Muto T Naito T Naumenko G Nelson J Nguyen MN Oide K Okugi T Omori T Oshima T Pei G Potylitsyn A Qin Q Raubenheimer T Ross M Sakai H Sakai I Schmidt F Slaton T Smith H 《Physical review letters》2002,88(19):194801
Electron beams with the lowest, normalized transverse emittance recorded so far were produced and confirmed in single-bunch-mode operation of the Accelerator Test Facility at KEK. We established a tuning method of the damping ring which achieves a small vertical dispersion and small x-y orbit coupling. The vertical emittance was less than 1% of the horizontal emittance. At the zero-intensity limit, the vertical normalized emittance was less than 2.8 x 10(-8) rad m at beam energy 1.3 GeV. At high intensity, strong effects of intrabeam scattering were observed, which had been expected in view of the extremely high particle density due to the small transverse emittance. 相似文献
995.
We report a systematic study of the spin polarization of epitaxial CrO2 films at and across an interface using planar junctions with a superconducting counterelectrode. By chemical modification of the CrO2 surface before the deposition of the superconductor, junctions with a wide range of barrier strength were obtained. Analysis of the conductance data on these junctions, especially under Zeeman splitting of the superconducting density of states, yields consistent, close to full spin polarization for CrO2 regardless of the barrier strength. 相似文献
996.
In the framework of the minimal supersymmetric model we examine the Z-peak constraints on the scenario of one light bottom squark (sbottom) ( approximately 2-5.5 GeV) and light gluino (approximately 12-16 GeV), which has been successfully used to explain the excess of bottom quark production in hadron collisions. Such a scenario is found to be severely constrained by the CERN LEP Z-peak observables, especially by R(b), due to the large effect of gluino-sbottom loops. To account for the R(b) data in this scenario, the other mass eigenstate of sbottom, i.e., the heavier one, must be lighter than 125 (195) GeV at 2sigma(3sigma) level, which, however, is disfavored by CERN LEP II experiments. 相似文献
997.
Highly ordered Prussian blue nanowires with diameter of about 50 nm and length up to 4 m have been fabricated by an electrodepositing technology with two-step anodizing anodic aluminum oxide films. The Mössbauer spectra taken between 15 and 300 K indicate that the hyperfine parameters decrease as the temperature increases. The temperature dependence of the quadrupole splitting, the isomer shift and the spectra area are discussed. A decrease of Debye temperature for Prussian blue nanowires was found with respect to that of Prussian blue bulk. 相似文献
998.
999.
LaIl{1Tussalivlts(L.salivus)isleguminouscropcultivatedinlndia,BangladeshandEthiopia,whereitisamajorproteinsourceforpeopleinthelowestincomegroups"'.However,excessiveingestionofthispulsecanleadtoirreversibleparalysisofthelegs-adiseaseknownasneurolathyrisn1orlathyrism.Thecausativeagentwasreportedtobethenon-proteinaminoacid,3-N-L-oxalyl-2,3-diaminopropioniacid(o-ODAP,sometimes,referredtoasBOAA)','.Thea-isomerofODAP,2-N-oxalyl-2,3-diaminopropionicacid,hasbeenshowntobenontoxictochicksandmice… 相似文献
1000.
Xizhang Luo Jiancong Luo Jiayin Qin 《International Journal of Infrared and Millimeter Waves》1999,20(6):1085-1090
The effect of buffer gas N2 on miniature optically pumped NH3 submillimeter wave (SMMW) cavity laser emission at 67.2m was studied theoretically and experimentally. It has been found that: 1. N2 had a positive effect on laser output of 67.2m, 2. sharp absorption in laser spectrum under certain gases mixture pressure corresponded to the threshold of 'bottleneck effect. 相似文献