Hyperfine interaction of 25Al in α-Al2O3 and its quadrupole moment

A brief review is presented of recent work with the Precision Penning Trap Mass Spectrometer, formerly at MIT, now at Florida State University. This includes atomic mass comparisons using single trapped ions; mass comparisons using two simultaneously trapped ions alternated between large and small cyclotron radii; and measurement of the dipole moment of a molecular ion using the polarizability-induced shift in cyclotron frequency.     

Fixation of a cholesteric helical structure by the photopolymerization of a cholesteryl derived monomer

A cholesteryl derived monomer was synthesized according to a conventional synthetic route; it exhibits a cholesteric phase above 129°C, and shows a red colour due to selective reflection in the cholesteric phase. Photopolymerization of the monomer was carried out at 135°C in the cholesteric phase. The helical structure of the cholesteric phase of the monomer was frozen by photopolymerization. A peak based on the selective reflection of the cholesteric phase was detected at 615 nm in the transmittance UV-Vis spectrum. Mixtures of the monomer with a binaphthyl derivative were prepared to control the selective reflection wavelength; they all also exhibited a cholesteric phase. The selective reflection wavelength of the mixture was dependent upon the ratio of the binaphthyl derivative in the mixture. This wavelength became shorter with increasing ratio of the binaphthyl derivative. The polymer films obtained by photopolymerization displayed almost the same selective reflection wavelength as the corresponding mixtures before photopolymerization. The selective reflection wavelength of the polymer films did not change up to about 250°C.     

Correlation between proton magnetic resonance spectroscopic lactate measurements and vascular reactivity in chronic occlusive cerebrovascular disease: a comparison with positron emission tomography

The purpose of this study is to investigate the correlation between lactate levels and cerebral vascular reactivity (VR) in regions outside an area of chronic cerebral infarction. Multivoxel proton magnetic resonance spectroscopy ((1)H-MRS) and positron emission tomography (PET) were performed in 11 patients who suffered chronic cerebral infarction. Of these 11 patients, 4 were examined before and after bypass surgery. Two regions-of-interests (ROIs) were placed outside the area of chronic infarction. One ROI was placed within a control region on the contralateral side. A lactate peak area was obtained in all ROIs. An N-acetyl aspartate (NAA) peak area was obtained in the ROI within the control region. The ratio of the lactate peak area and NAA peak area (Lct/NAA) was calculated for normalization of the lactate level, and was found to be 0.13 +/- 0. 10 (range, 0 to 0.43). The VR was recorded at 13.3 +/- 20.7% (range, - 44.3 to 68.9%), utilizing PET and administering acetazolamide. A significant negative correlation was observed between the Lct/NAA ratio and VR (r = - 0.709, p < 0.0001). These results suggest that lactate levels and VR are closely related in regions outside areas of chronic cerebral infarction.     

Photoreduction of polyhalogenated anthraquinones by direct electron transfer from alcohol

Polyhalogenated anthraquinones such as perfluoroanthraquinone, 1,2,3,4-tetrafluoroanthraquinone, and 1,2,3,4-tetrachloroanthraquinone are photoreduced in ethanol via direct electron transfer from ethanol. A dramatic switch-over from hydrogen-atom abstraction to electron transfer is induced by mixing ofππ with nπ^* states in their T₁ state and the enhanced electron-accepting character of polyhalogenated anthraquinones.     

The frequency distribution functions of the crystalline,amorphous and liquid iron

The atomic vibrations in crystalline, amorphous and liquid iron are discussed based on the realistic models simulated in a computer. The frequency distribution functions of amorphous and liquid iron are of double peak and a single peak, respectively.     

Supramolecular Chemistry of Cyclodextrin-Peptide Hybrids: Azobenzene-Tagged Peptides

AC17, which is composed of 17 amino acids and has an azobenzene moiety but has no cyclodextrin (CD) unit in the side chain, exhibits 54% helix content. However, AC17, which has both trans-azobenzene and -CD, shows 82% helix content. This result suggests that the helix structure is stabilized by host (CD)-guest (azobenzene) bridge in the side chain of the peptide. The helix content changed by trans-cis photoisomerization as shown by 64% helix content for AC17 in its cis form. This result suggests that cis-azobenzene unit is excluded from the -CD cavity, thus resulting in the smaller helix content. The helix contents for AC17, which has both azobenzene and -CD, are 94% in the cis form and 87% in the trans form, suggesting that the cis form is included in the -CD cavity. Azobenzene-tagged CD-peptide hybrids with histidine unit were also prepared and photoregulation of catalytic activity in ester hydrolysis was examined.     

g-Factor Measurements of Rotational States in 84,86Zr

The g-factors of the positive parity yrast rotational states in ^84,86Zr have been precisely measured using a TMF-IMPAD method. The measured g factors indicate the proton alignment followed by neutron alignment in the g _9/2 high-j shell for ⁸⁴Zr and the neutron alignment followed by proton alignment for ⁸⁶Zr. The present results also reveal the structure transition at N=46 for Zr isotopes. This revised version was published online in September 2006 with corrections to the Cover Date.     

Hyperfine Interactions of 8Li in Ferromagnetic Single Crystal Fe

The hyperfine interactions of ⁸Li implanted in single crystal Fe have been studied using the β-NMR technique. One kind of hyperfine field B _hf was found. Since no dipolar field was observed, ⁸Li nuclei are suggested to sit in substitutional sites. The B _hf and the spin-lattice relaxation time T ₁ were observed as functions of temperature. The experimental B _hf and T ₁ were compared with the theoretical predictions from the first principles KKR-band-structure calculations. While predicted B _hf for the substitutional site is consistent with the experiment, predicted T ₁ cannot reproduce the experiment well. This revised version was published online in September 2006 with corrections to the Cover Date.     

Hyperfine Interactions of 12B in CaB6

The hyperfine interactions of short-lived β-emitter ¹²B implanted into a CaB₆ crystal have been studied by means of the β-NMR technique. An electric quadrupole splitting has been observed at room temperature from which an electric field gradient of q=−(1.34±0.05)×10²¹ V/m² was determined. From the present result, it was found that the ¹²B nuclei are mainly implanted in the substitutional boron site. This revised version was published online in September 2006 with corrections to the Cover Date.     

基于三维空间域移动通信统计信道的多普勒效应

针对散射体均匀分布以及三维空间域(3 dimension,3D)移动通信环境,提出了3D空间统计信道模型.对在指向性天线覆盖下的室内微小区移动通信环境,模型能够估计多径衰落信道的重要空时信道参数,如波达信号在水平面以及垂直面的信号到达角度(angle of arrival,AOA)以及多普勒效应(Doppler spectra,DS)等.移动台(mobile station,MS)的移动特性会使接收信号产生多普勒效应,根据运动的相对性理论,基站(base station,BS)也会有相对运动,因此也会有多普勒效应产生.本文引入控制变量法导出三维空间域在MS以及BS端的多普勒效应,数值仿真结果与室外3D多径衰落信道对比表明,本模型的信道参数估计结果符合理论和经验,扩展了3D空间统计信道模型的研究和应用.