Structure and morphology of cellulose in wheat straw

The structure and morphology of cellulose extracted from wheat were studied. It was found that the extraction process is effective and hemicelluloses and lignin can be extracted completely. Cellulose in wheat straw was identified as cellulose I allomorph with low crystallinity and the crystallinity of cellulose from different parts of the wheat straw has little difference. There was no metastable cellulose I crystalline modification found in wheat straw; only the more stable cellulose I crystalline modification existed. Cellulose chains in the epidermis of wheat straw were observed with their orientation along the growth direction of wheat straw, while those in parenchyma were observed with almost no preferred orientation. There are two kinds of morphologies on the surface of wheat straw. One is the fiber structure with fibrils of about 5 m diameter, and the other is the fiber structure with serration morphology at the edge of the fiber, with which the fibers are connected together. The diameter of the latter one is about 10 m. The vascular bundles consist of circular rings while spiral structure cellulose backbones covered with thin cellulose film were also observed.     

Controlled solvothermal synthesis of nanosheets, nanobelts, and ultralong nanobelt arrays with honeycomb-like micropatterns of ZnSe on zinc substrate

Nanosheets, nanobelts, and ultralong nanobelt arrays with honeycomb-like micropatterns of ZnSe were synthesized via a solvothermal reaction of Zn with Se and KBH(4) in ethylenediamine at 200 degrees C for 24 h and subsequent annealing. The control over these nanostructures with different morphologies was achieved by adjusting the KBH(4)/Se molar ratio. The role of KBH(4) in the formation of ZnSe(en)(0.5) nanobelts with different length-to-width ratios was investigated, and a possible mechanism was also proposed to account for the growth and conversion of these precursor nanostructures into ZnSe nanostructures. Current-voltage behaviors of the ultralong nanobelt arrays with honeycomb-like micropatterns were investigated. In addition, variable-aspect ratio ZnS nanosheets and nanowires were also synthesized by adjusting the KBH(4)/thiourea molar ratio in the Zn-thiourea-KBH(4)-ethylenediamine solvothermal system. The results suggest that this method may be employed for the controllable synthesis of other II-VI semiconductor nanostructures such as ZnTe, NiS, MnS, and so forth and provides opportunities for both fundamental research and technological applications.     

Directly Regioselective Protection of Secondary Hydroxyl Group on Ribosides in Aqueous Solution

Selective benzoylation of secondary hydroxyl on sugar moiety of various ribosides including N‐ribosides, O‐ribosides and 2′‐deoxy‐N‐riboside was investigated by using benzoyl chloride and Na₂CO₃ in aqueous CH₃CN. The influence of the aglycone and sugar moiety on the selectivity of benzoylation was discussed as well. A most efficient method for preparation of 2′,3′‐O‐dibenzoylnucleosides was developed.     

Influence of additives on the crystal structure and melting behavior of poly(ethylene‐2,6‐naphthalene dicarboxylate)

The influence of additives on the crystal modification and melting behavior of poly(ethylene‐2,6‐naphthalene dicarboxylate) (PEN) was investigated with wide‐angle X‐ray diffraction and differential scanning calorimetry (DSC). The addition of a nucleating promoter, Ceraflour 993, had no effect on the crystal modification and melting behavior of PEN crystallized under all chosen experimental conditions. However, the addition of a nucleating agent, sodium benzoate (SB), did affect the crystal modification and melting behavior of PEN when PEN/SB was crystallized at a higher temperature, but not at a lower temperature. A mixture of α and β modifications of PEN was obtained, and an overlapped dual melting peak was observed in DSC curves when PEN was crystallized at a higher temperature in the presence of SB, instead of a single crystal form and a single melting peak for the crystallization of pure PEN. © 2003 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 42: 296–301, 2004     

Precise measurement of magnetic moment of short-lived β-emitting nuclei 12B (Iπ= 1+, T1/2 = 20.18 ms)

The spin polarized β-emitting nuclei 12B (Iπ = 1+, T1/2 = 20.18 ms) were produced by the nuclear reaction 11B(d, p) 12B and by the selection technique of the incident deuteron energy and the 12B recoil angle following the nuclear reaction. The nuclear magnetic moment of the short-lived nuclei 12B was measured by β-NMR with the β-NMR and β-NQR setup established for the first time in China. The nuclear magnetic moment of 12B was determined to be μ = 0.99993 ± 0.00048 nm or g = 0.99993 ± 0.00048 after the precise correction of the Knight shift.     

Dynamics of Rossby solitary waves with time-dependent mean flow via Euler eigenvalue model

The investigation on the fluctuations of nonlinear Rossby waves is of great importance for the understanding of atmospheric or oceanic motions. The present paper mainly deals with the well-known atmospheric blocking phenomena through the nonlinear Rossby wave theories and the corresponding methods. Based on the equivalent barotropic potential vorticity model in the β-plane approximation underlying a weak time-dependent mean flow, the multiscale technique and perturbation approximated methods are adopted to derive a new forced Korteweg-de Vries model equation with varied coefficients (vfKdV) for the Rossby wave amplitude. For a further analytical treatment of the obtained model problem, a special kind of basic flow is adopted. The evolution processes of atmospheric blocking are well discussed according to the given parameters according to the dipole blocking theory. The effects of some physical factors, especially the mean flow, on the propagation of atmospheric blocking are analyzed.

     

BRISOL铝同位素放射性核束的产生

北京放射性核束装置在线同位素分离器(BRISOL)采用100 MeV回旋加速器提供的最大200 μA的质子束打靶在线产生放射性核束。在BRISOL上已经使用氧化钙靶、氧化镁靶产生了Na+、K+等放射性核束。为了产生铝同位素放射性核束,研发了碳化硅靶材,开展了碳化硅靶产生铝放射性核束的实验研究。在BRISOL装置上首次产生了铝同位素放射性核束,其中26gAl+的束流强度为8.7×107 pps,23Al+的束流强度为2.2×102 pps,同时将BRISOL靶能承受的质子束流强提升至15 。     

A new model equation for nonlinear Rossby waves and some of its solutions

In this paper, we investigate the $(2+1)$ dimensional nonlinear Rossby waves under non-traditional approximation. Using the asymptotic methods of multiple scales and weak nonlinear perturbation expansions, we derive a new modified Zakharov–Kuznetsov equation from the barotropic potential vorticity equation with the complete Coriolis parameter, the topography and the dissipation. Based on the new auxiliary equation method, new exact solutions of the new mZK equation are obtained when the dissipation is absent. However, the new auxiliary equation method fails to solve the new mZK equation with the dissipative term. Therefore, the weak nonlinear method and the homotopy perturbation method are developed to solve the obtained new mZK equation. Through numerical simulations, the results show the effects of different parameters on Rossby waves.     

Manufacturing and testing of a cubic SiC surface

The free surface and unrotational-symmetric surface optical elements have been applied more and more widely along with the development of optical design technology, although they are still difficult for manufacturing. In this letter, a SiC unrotational-symmetric aspheric surface whose surface equation is z =- 3λ（x^a ＋ y^3） （λ= 0.6328μm） has been introduced. The tilt abstraction is adopted to minimize the material removal. The surface figures are peak-to-valley （PV） value of 0.327A and root-mean-square （RMS） value of 0.023A. A non-null testing method based on digital mask is proposed to test this surface. The accuracy of the method is testified by the experiment of standard sphere testing.