CP/MAS 13C-NMR技术对桉木浆纤维素微观结构的研究

利用交叉极化结合魔角旋转技术13C 核磁共振法(CP/MAS ¹³C NMR)对桉木浆纤维的微观结构进行研究, 为进一步研究木质纤维素材料开发过程中反应障碍特征奠定基础. 通过对NMR光谱C1区(δ 102～108)进行洛仑兹拟合, 得到桉木浆纤维中纤维素Iα的相对含量为26.92%, 纤维素Iβ的相对含量为52.04%, 主要以纤维素Iβ晶体形式为主. 通过计算纤维素C4结晶区(δ 86～92)和非结晶区(δ 80～86)的相对含量得到桉木浆的纤维素结晶度为47%. 通过洛仑兹和高斯函数的混合模型对NMR光谱C4区(δ 80～92)进行拟合得到基原纤尺寸和微原纤横向尺寸分别为4.0与17.9 nm, 并通过计算不同形态的结晶纤维素的相对含量得到纤维素结晶度为51%, 证实了在微原纤内部次晶纤维素的存在.     

Radiation field eigenstates and its unitary equivalence to coordinate eigenstates

In this paper, we reconstruct the explicit representation of the radiation field eigenstates in Fock space by decomposing the normally ordered Gaussian operator. Then with the help of the technique of integration within an ordered product of operators, the phase-shifting operator in quantum optics has been expressed through the Dirac's representation theory. In addition, the unitarily equivalent relation between the radiation field eigenstates and the coordinate eigenstates has been naturally established by the phase-shifting operator in quantum optics. These results deepen people's understanding to the radiation field eigenstates and phase-shifting operator in quantum optics.     

A comparison of glycans and polyglycans using solid-state NMR and X-ray powder diffraction

Individual polyglycans and their corresponding monomers have been studied separately for several decades. Attention has focused primarily on the modifications of these polyglycans instead of the simple relationship between the polyglycans themselves and their corresponding monomers. Two polyglycans, chitin and chitosan, were examined along with their respective monomeric units, N-acetyl-D-glucosamine (GlcNAc) and (+)D-glucosamine (GlcN) using solid-state proton decoupling Magic Angle Turning (MAT) techniques and X-Ray Powder Diffraction (XRPD). A down-field shift in isotropic (13)C chemical shifts was observed for both polymers in Cross Polarization/Magic Angle Spinning (CP/MAS) spectra. An explanation of misleading peak assignments in previous NMR studies for these polyglycans was determined by comparing sideband patterns of the polymers with their corresponding monomers generated in a 2D FIve pi REplicated Magic Angle Turning (FIREMAT) experiment processed by Technique for Importing Greater Evolution Resolution (TIGER). Structural changes in the crystalline framework were supported by XRPD diffraction data.     

Studies on the adsorption of arsenic on calix[6]arene

p‐tert‐butyl calix[6]arene (PTC6) was synthesized and characterized by solid‐ and liquid‐state NMR and LC‐MS techniques. The adsorption of arsenite and arsenate on calix[6]arene under different pH conditions and adsorbate doses was studied. The maximum adsorption of arsenic species on calix[6]arene was observed around neutral pH and the adsorption density of As (III) was higher than that of As (V). The adsorption of neutral H₃AsO₃ and negatively charged H₂AsO molecules on calix[6]arene was attributed to the condensation reaction between hydroxyl groups of PTC6 and arsenic species. The complexation of arsenite with phenolic oxygen was confirmed by solid‐state ¹³C NMR CP‐MAS. Exo attack mechanism was proposed to describe the interaction of arsenous and arsenic acid molecules with PTC6. The specific interaction between calix[6]arene and arsenic species was further substantiated by zeta‐potential (ζ‐potential) measurements and free energy of adsorption. The free energy of adsorption ( ) estimated from Stern–Grahame equation was found to be 25 kJ/mole for As (III) and 19 kJ/mole for As (V). Copyright © 2010 John Wiley & Sons, Ltd.     

Deviations of the lepton mapping matrix from the Harrison-Perkins- Scott form

We propose a simple set of hypotheses governing the deviations of the leptonic mapping matrix from the Harrison-Perkins-Scott （HPS） form. These deviations are supposed to arise entirely from a perturbation of the mass matrix in the charged lepton sector. The perturbing matrix is assumed to be purely imaginary （thus maximally T-violating） and to have a strength in energy scale no greater （but perhaps smaller） than the muon mass. As we shall show, it then follows that the absolute value of the mapping matrix elements pertaining to the tau lepton deviate by no more than O（（mμ/mτ）^2） ≈ 3.5 ×10^-3 from their HPS values. Assuming that （mμ/mτ）^2 can be neglected, we derive two simple constraints on the four parameters θ12,θ23, θ31, and δ of the mapping matrix. These constraints are independent of the details of the imaginary T-violating perturbation of the charged lepton mass matrix. We also show that the e and μ parts of the mapping matrix have a definite form governed by two parameters α and β; any deviation of order mμ/mτ can be accommodated by adjusting these two parameters.     

Double Charm Decays of B Mesons in mSUGRA Model

Based on the low energy effective Hamiltonian with naive factorization, we calculate the branching ratios (BRs) and CP asymmetries (CPAs) for the twenty three double charm decays B/B_s \to D^{(*)}_{(s)} D^{(*)}_{(s)} in both the standard model (SM) and the minimal supergravity (mSUGRA) model. Within the considered parameter space, we find that (a) the theoretical predictions for the BRs, CPAs and the polarization fractions in the SM and the mSUGRA model are all consistent with the currently available data within±2σ errors; (b) For all the considered decays, the supersymmetric contributions in
the mSUGRA model are very small, less than7% numerically. It may be difficult to observe so small SUSY contributions even at LHC.     

Supersymmetric contributions to BS→K-π+ decay

Recently, the CDF Collaboration has measured the branching fraction and time-integrated direct CP asymmetry of BS→K-π+ decay. The branching ratio is lower than the previous predictions based on QCD factorization. The experimental results favor a large CP asymmetry in BS→K-π+ decay while the standard model prediction is very small. We compute the supersymmetry contributions to BS→K-π+ decay using the mass insertion method, and find that the LR and RL mass insertions could suppress this branching ratio and increase this direct CP asymmetry well in line with the experimental data.     

Electron states in curved quantum structures with varying radius

The influence of size and shape is investigated for quantum-dot electronic states and intra-band oscillator strengths adapting a method originally due to Stevenson. The present work solves the one-band envelope-function problem for conduction-band eigenstates in the framework of theory using general curved coordinates. The eigenstates found are subsequently employed to express intra-band oscillator strengths and emphasis is given to the dependence of oscillator strengths on quantum-dot size and shape. We finally provide four simple examples.     

On q-Commutator in the Case qs+l = 1

In this letter, the representations of q-commutator in the case q^s+l = 1 and the eigenstates of annihilation operator have been discussed.     

Experimental sensitivity on searching for CP violation at BES-III

The CP violation in the D system is predicted to be an unobserved level in the Standard Model. In this paper, we describe the method of searching for CP violation decay processes with the coherently produced D00 mesons from the ψ(3770) decay. The CP violation decay processes can be searched for at the BES-III experiment. The experimental sensitivity for searching for the CP violation can reach about a 10-4 level with a ψ(3770) data sample of about 20 fb-1.