Enhanced spontaneous emission factor for microcavity lasers

The microcavity and the influence of nonradiative recombination can control spontaneous emission. An analytic resolution of rate equation is studied for microcavity lasers. The relationship between output prop- erties and structural parameters of multi-quantum wells (MQWs) is obtained. One of the most important consequences of the incrcased spontaneous emission factor is the reduction of laser threshold. It is found that the characteristic curve of a "thresholdless" laser is strongly nonradiative depopulation-dependent. The light output is increased by the enhanced well number and the reduced width. In particular, there is an optimal well number corresponding to the lowest threshold current density for MQW structure in the microcavity lasers.     

人肝癌SMMC-7721细胞对低剂量γ射线辐射超敏感性的研究

研究了人肝癌细胞SMMC-7721在低剂量γ射线照射下超敏感性和增强的辐射抗性响应。选用对数生长期细胞接受0—6 Gy不同剂量的^60Coγ射线的照射。利用流式细胞仪对细胞进行分选计数,并用克隆形成法检测细胞存活率。发现SMMC-7721细胞存在低剂量辐射超敏感性和增强的辐射抗性响应,即在0—0．3Gy之间细胞表现出单位剂量杀伤增强现象,在0．3—1Gy细胞表现一定的辐射抗性,在1Gy以上,细胞的存活符合线性平方模型。     

Studies on the Structure and Properties of Cordierite Synthesized by Talc-Magnesite

Homogeneous cordierite has been synthesized at low cost by talc-magnesite and coal gangue as the main raw materials. The mechanism of synthesizing cordierite under such a com- posing system of raw materials, and the effect of temperature on the crystal cell parameters and microstructure and thermal expansion coefficient of cordierite crystal have been studied via testing methods of XRD, SEM, etc. The result shows that the homogeneous cordierite can be synthesized by the systematic composing materials of “talc-magnesite—coal gangue—talc” with heat pre- servation at 1350 ℃ for 1 h; as the keeping time is prolonged, Al3+ and Mg2+ in cordierite crystal are replaced by a few impurity ions such as Fe3+, Fe2+, etc., and the crystal cell parameters of cordierite present an increase trend; as the high-temperature heat preservation is prolonged, the content of glassy phase in the sample is increased, its density is improved, and its thermal expansion coeffi- cient presents an increase trend.     

RADIATION DEGRADATION OF CHITOSAN IN THE PRESENCE OF H2O2

INTRODUCTIONChitosan, poly-β-(1 -?4)-D-glucosamine, can be obtained from chitin by deacetylation with alkali. It is soluble indilute acidic medium due to the presence of amino groups. The use of chitosan in many areas, such as foodprocessing, biochemistry, Pharmaceuticals, medicine, and agriculture has been developed over the pastdecades[1,2].In recent years, it has been reported that many properties of chitosan depend on the molecular weight[3]. Thechitosan oligomers possess better fun…     

MECHANICAL PROPERTIES OF OZONIZED HDPE FILLED WITH SERICITE-TRIDYMITE-CRISTOBALITE

The mechanical properties of ozonized high density polyethylene (HDPE) blended with sericite-tridymite-cristobalite (STC) were studied in this paper. The experimental results show that some oxygen containing polar groups are introduced on the molecular chain of HDPE through ozonization, the compatibility between HDPE and STC is thus improved, the mechanical properties of the blend are markedly enhanced. Compared with untreated HDPE/STC (60/40) blend, the yield strength and notched impact strength of ozonized HDPE/STC (60/40) blend are increased from 27.0MPa to 29.5MPa and from 2.8kJ/m^2 to 13.3kJ/m^2, respectively, the notched impact strength is close to that of HDPE (13.6kJ/m^2),the yield strength is in excess of 3.9MPa of that of HDPE. The yield strength and notched impact strength will be further increased to 30.7MPa and 32.4kJ/m^2 in case the ozonized HDPE is blended with STC pretreated with silane coupling agent.     

STRUCTURAL PHASE TRANSITION OF ALIPHATIC NYLONS VIEWED FROM THE WAXD/SAXS AND VIBRATIONAL SPECTRAL MEASUREMENTS AND MOLECULAR DYNAMICS CALCULATION

The crystalline phase transition of aliphatic nylon 10/10 has been investigated on the basis of the simultaneous measurement of wide-angle and small-angle X-ray scatterings, the infrared spectral measurement and the molecular dynamics calculation. An interpretation of infrared spectra taken for a series of nylon samples and the corresponding model compounds was successfully made, allowing us to assign the infrared bands of the planar-zigzag methylene segments reasonably. As a result the methylene segmental parts of molecular chains were found to experience an order-to-disorder transition in the Brill transition region, where the intermolecular hydrogen bonds are kept alive although the bond strength becomes weaker at higher temperature. The small-angle X-ray scattering data revealed a slight change in lamellar stacking mode in the transition region. The crystal structure has been found to change more remarkably in the temperature region immediately below the melting point, where the conformationally disordered chains experienced drastic rotational and translational motions without any constraints by hydrogen bonds, and the lamellar thickness increased largely along the chain axis. These experimental results were reasonably reproduced by the molecular dynamics calculation performed at the various temperatures.     

Wideband film polarizer design

The reflection and transmittance of s- and p-polarized lights should be treated separately at nonzero angle incidence. By choosing two special film materials whose refractive indices meet the Brewster condition in a given incident angle, the reflection of p-polarized light can be eliminated. When the two materials are fabricated into multilayer stacks, the reflection of s-polarized light can be largely increased while the reflection of p-polarized light keeps low. According to this principle, a film polarizer with bandwidth of 198 nm or even more is designed.     

液氮对含水煤样裂隙疲劳增扩作用的试验研究

为分析液氮注入对含水煤层裂隙疲劳增扩的影响,分别取干燥煤样、50%水饱和煤样和100%水饱和煤样,在室内开展了周期疲劳液氮浸泡试验,利用激光显微镜和声波测试仪测试液氮作用前后煤样表面裂隙结构和波速的变化。结果表明:1)经过液氮浸泡后,干燥煤样裂隙扩展效果不明显,10个浸泡周期后煤样仍完整;2)含水煤样的裂隙主要在垂直节理方向发生扩展;3)饱水程度越高,煤样裂隙扩展越显著;4)饱水程度越高,煤样液氮浸泡破坏所需的浸泡周期越短。煤样的饱水程度对液氮致裂效果影响显著。     

2D-QSAR Studies on Triazolone Compounds Containing Benzenesulfonic Amide

The geometry structures of 6 triazolone compounds containing benzenesulfonic amide were fully optimized with DFT (Density Functional Theory) method at the B3LYP/6-31G level, and the structural and electronic parameters of the compounds were calculated. The hydrophobic and topological parameters of the title compounds were calculated by HyperChem software. The mono-and bi-parametric models between the parameters and biological activity of the compounds were analyzed by Multiple Linear Regression method based on Hansch-Fujita model. The results show that the activities of the title compounds were increased with higher hydrophobic property logP and molecular volume V, lower molecular energy ETOTAL and elec-tronegative of benzene ring Qph.