p-sd Shell gap reduction in neutron-rich systems and cross-shell excitations in 20 O

Excited states in 20O were populated in the reaction 10Be(14C,alpha) at Florida State University (FSU). Charged particles were detected with a particle telescope consisting of 4 annularly segmented Si surface barrier detectors and gamma radiation was detected with the FSU gamma detector array. Five new states were observed below 6 MeV from the alpha-gamma and alpha-gamma-gamma coincidence data. Shell model calculations suggest that most of the newly observed states are core-excited 1p-1h excitations across the N=Z=8 shell gap. Comparisons between experimental data and calculations for the neutron-rich O and F isotopes imply a steady reduction of the p-sd shell gap as neutrons are added.     

Structures and Dynamics of Secondary and Tertiary Alkylphosphine Oxides Adsorbed on Silica

The three secondary phosphine oxides [CH₂=CH(CH₂)₄]₂HPO ( 1 ), [CH₂=CH(CH₂)₅]₂HPO ( 2 ), and [CH₂=CH(CH₂)₆]₂HPO ( 3 ), and two diphosphine dioxides, {[CH₂=CH(CH₂)₆]₂PO(CH₂)₇}₂ ( 4 ) and {[CH₂=CH(CH₂)₆]₂PO(CH₂)₄}₂ ( 5 ), incorporating long methylene chains, are described. The single crystal X‐ray structures of 1 , 2 , and 5 have been determined. The phosphine oxides 3 , 4 , and 5 have been adsorbed on silica in submonolayer quantities to give 3 a – 5 a . The ¹H, ¹³C, and ³¹P solid‐state NMR spectra of polycrystalline 3 – 5 have been analyzed and compared with those of 3 a – 5 a . The changes of the solid‐state NMR characteristics upon adsorption and the surface mobilities of the phosphine oxides are discussed.     

Comparison of connective tissue invaded by Lewis lung carcinoma to healthy connective tissue by means of micro‐Raman spectroscopy

We have measured the micro‐Raman spectra of mouse tissues invaded by Lewis lung carcinoma (LLC). We have also carried out categorical principal component analysis (CATPCA) on the acquired spectra. The results indicate that the tumor tissues can be well discriminated from normal tissues by the first two principal components extracted from the spectra. Furthermore, we have found that the concentrations of nucleic acids and lipids/fatty acids in the tumor are considerably higher than those in the normal tissue, whereas the collagen concentration is lower. These differences can be detected and characterized by Raman images using the 788 cm⁻¹ DNA/RNA band and the 1301 cm⁻¹ lipid/fatty acid band. Copyright © 2009 John Wiley & Sons, Ltd.     

Astrophysical reaction rate for the neutron-generator reaction 13C(alpha,n)16O in asymptotic giant branch stars

The reaction 13C(alpha,n) is considered to be the main source of neutrons for the s process in asymptotic giant branch stars. At low energies, the cross section is dominated by the 1/2+ 6.356 MeV subthreshold resonance in (17)O whose contribution at stellar temperatures is uncertain by a factor of 10. In this work, we performed the most precise determination of the low-energy astrophysical S factor using the indirect asymptotic normalization (ANC) technique. The alpha-particle ANC for the subthreshold state has been measured using the sub-Coulomb alpha-transfer reaction ((6)Li,d). Using the determined ANC, we calculated S(0), which turns out to be an order of magnitude smaller than in the nuclear astrophysics compilation of reaction rates.     

Mechanism of THz emission from asymmetric double quantum wells

Impulsive interband optical excitation of the lowest two conduction subbands of a suitably engineered GaAs/AlGaAs double quantum well can lead to coherent THz emission. We demonstrate that, contrary to previous expectations, the dominant emission mechanism can involve the beating of either continuum or exciton states, depending on excitation conditions. The coherence of the continuum beats persists for several picoseconds even for excitation an optical phonon energy above the band edge. We attribute this to the small energy difference between the component eigenstates, which substantially reduces the number of relevant scattering events.     

Monometallic Ni0 and Heterobimetallic Ni0/AuI Complexes of Tripodal Phosphine Ligands: Characterization in Solution and in the Solid State and Catalysis

The tridentate chelate nickel complexes [(CO)Ni{(PPh₂CH₂)₃CMe}] ( 2 ), [(CO)Ni{(PPh₂CH₂CH₂)₃SiMe}] ( 6 ), and [Ph₃PNi{(PPh₂CH₂CH₂)₃SiMe}] ( 7 ), as well as the bidentate complex [(CO)₂Ni{(PPh₂CH₂)₂CMeCH₂PPh₂}] ( 3 ) and the heterobimetallic complex [(CO)₂Ni{(PPh₂CH₂)₂CMeCH₂Ph₂PAuCl}] ( 4 ), have been synthesized and fully characterized in solution. All ¹H and ¹³C NMR signal assignments are based on 2D‐NMR methods. Single crystal X‐ray structures have been obtained for all complexes. Their ³¹P CP/MAS (cross polarization with magic angle spinning) NMR spectra have been recorded and the isotropic lines identified. The signals were assigned with the help of their chemical shift anisotropy (CSA) data. All complexes have been tested regarding their catalytic activity for the cyclotrimerization of phenylacetylene. Whereas complexes 2 – 4 display low catalytic activity, complex 7 leads to quantitative conversion of the substrate within four hours and is highly selective throughout the catalytic reaction.     

教师教学水平的时齐马尔可夫链评估方法

采用时齐马尔可夫链方法给出了一种评估教师教学水平的方法,对文［１］所给方法做了适当的改进,拓宽了该方法的应用范围,在多民族院校,使用本法可以克服由于学生基础不同等多方面的原因造成难以比较教师教学水平的难题．