气相外延GaN的拉曼散射

测量了在蓝宝石衬底上气相外延生长GaN的拉曼散射谱.除观察到已被确认的两个E2,一个A1(TO)和一个E1(TO)声于振动以外,在734±3cm-1处观察到一个散射峰且从实验上确认其为GaN的纵向光学声子模E1(LO).而且发现其强度与外延层晶体质量密切相关.A1(TO)和高频E2散射峰相对强度变化显示不同生长条件引起的外延层质量的变化.     

Interaction of Trypan Blue with Protein and Application

The microphase adsorption ‐ spectral correction (MPASC) technique has been described and applied to the aggregation of trypan blue (TB) in proteins. The formation of the microelectrostatic field in protein causes the Langmuir monolayer aggregation of TB. The adsorption ratio of TB to bovine serum albumin (BSA), ovalbumin (OVA), hemoglobin (Hb) and human γ‐globulin (γ‐G) was determined to be 14.8, 8.4, 2.8 and 27.6, respectively, and the adsorption constant of the aggregates to be 7.17 × 10⁵, 4.88 × 10⁶, 4.85 × 10⁶ and 2.99 × 10⁶. The adsorption ratio of TB to proteins interestingly indicates almost no relation to the array sequence of amino acid residues. The interaction of TB with proteins is sensitive at pH 3.29, and the reaction was applied to the determination of protein trace with satisfactory results.     

Axial magnetic field contacts with nonuniform distributed axial magnetic fields

It is well known that axial magnetic fields (AMFs) can keep vacuum arc in diffuse mode at high current. According to our recent research and other published papers, it has been found that vacuum arc can be maintained in high-current diffuse mode at much higher current if nonuniform AMF is applied, that the axial magnetic field is higher at contact periphery than at center. The influence of spatial distribution of AMF on vacuum arc is mainly studied in this paper. Furthermore, two types of AMF contacts with new structures to generate nonuniform AMF are presented.     

Bergman空间B_q~p(p>0,q>1)中的Bernstein型不等式

本文在Bergman空间Bqp(p>0,q>1)中得到了关于用多项式本身的模控制其导函数的模的Bernstein型不等式．     

Performance of optical amplifier employing silica host magnesium-aluminum-germanium co-doped erbium-doped fiber

Two silica host magnesium(Mg)-aluminum(Al)-germanium(Ge) co-doped erbium-doped fibers (EDFs)have been fabricated, which have different Mg concentrations. The concentration of all the compositions in the preform is measured through electronics probe micro analysis (EPMA). The maximum Mg concentrations of fibers A and B are 3.98 and 1.28 mol%, respectively. The performance characteristics including absorption spectrum and gain are measured and analyzed. The absorption coefficients of fibers A and B are 13.3 and 14.3 dB/m respectively at wavelength of 1532 nm. The max gains of these two erbium-doped fiber amplifiers (EDFAs) are 30.1 and 35.9 dB with input signal power of -30 dBm and pump power of 100 mW at 980 nm. Fiber B with maximum Mg concentration 1.28 mol% has better performance than fiber A. Fiber B has high absorption coefficient and high gain characteristics. The optimum fiber B length of C-band EDFA is 7 m and that of L-Band EDFA is about 30 m, which is much shorter than standard commercial EDFAs. The result of experiments showed that a few Mg added to silica host EDF can increase the concentration of erbium ions, which will shorten the EDF length much, but not degrade the performance characteristics.     

链间耦合对聚合物中双激子态反向极化的影响

从紧束缚模型出发，研究了链间相互作用对双激子态反向极化的影响.结果发现：加链间耦合后，双激子态仍主要局域在一条链中.当简并破缺较小时，反向极化程度随耦合强度的增加大幅提高；当简并破缺较大时，反向极化程度随耦合强度的增加基本不变. 关键词： 反向极化 双激子态 链间耦合     

Mechanism of the formation of singularities for quasilinear hyperbolic systems with linearly degenerate characteristic fields

One often believes that there is no shock formation for the Cauchy problem of quasilinear hyperbolic systems (of conservation laws) with linearly degenerate characteristic fields. It has been a conjecture for a long time (see Arch. Rational Mech. Anal. 2004; 172 :65–91; Compressible Fluid Flow and Systems of Conservation Laws in Several Space Variables. Springer: New York, 1984) and it is still an open problem in the general situation up to now. In this paper, a framework to justify this conjecture is proposed, and, by means of the concept such as the strict block hyperbolicity, the part richness and the successively block‐closed system, some general kinds of quasilinear hyperbolic systems, which verify the conjecture, are given. Copyright © 2007 John Wiley & Sons, Ltd.     

Thermal degradation kinetics of biodegradable poly(3‐hydroxybutyrate)/layered double hydroxide nanocomposites

The thermal degradation behaviors of biodegradable poly(3‐hydroxybutyrate) (PHB) and PHB/poly(ethylene glycol) phosphonates (PEOPAs)‐modified layered double hydroxide (PMLDH) nanocomposites have been investigated using thermogravimetric analysis. Effects of PMLDH contents on the isothermal degradation kinetics of PHB were explored. These experimental results show that the degradation kinetics of PHB/PMLDH nanocomposites is the chain‐scission process of cyclic β‐elimination reaction with the following autocatalytic reactions, which is very similar to that of pure PHB matrix. Further calculated data based on the autocatalytic model can fit very well with the experimental data. The E_a value of PHB/PMLDH nanocomposites is increased as the content of PMLDH increases. This can be attributed to the incorporation of more PMLDH loading to PHB induced a decrease in the degradation rate and an increase in the residual weight for PHB/PMLDH nanocomposites. © 2008 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 46: 1207–1213, 2008