Effect of SiO2 encapsulation on the nitrogen reorganization in GaNAs/GaAs single quantum well

Effects of SiO2, encapsulation and rapid thermal annealing (RTA) on the optical properties of GaNAs/GaAs single quantum well (SQW) were studied by low temperature photoluminescence (PL). A blueshift of the PL peak energy for both the SiO2-capped region and the bare region was observed. The results were attributed to the nitrogen reorganization in the GaNAs/GaAs SQW. It was also shown that the nitrogen reorganization was obviously enhanced by SiO2 cap-layer. A simple model [1] was used to describe the SiO2-enhanced blueshift of the low temperature PL peak energy.

Photoluminescence characterization of 1.3 mu m In(Ga)As/GaAs islands grown by molecular beam epitaxy

1.3 mum wavelength In(Ga)As/GaAs nanometer scale islands grown by molecular beam epitaxy (MBE) were characterized by photoluminescence (PL) and atomic force microscopy (AFM) measurements. It is shown that inhomogeneous broadening of optical emission due to fluctuation of the In0.5Ga0.5As islands both in size and in compositions can be effectively suppressed by introducing a AlAs layer and a strain reduction In0.2Ga0.8As layer overgrown on top of the islands, 1.3mum emission wavelength with narrower line-width less than 20meV at room temperature was obtained.

New way to enhance the uniformity of self-organized InAs quantum dots

Growth interruption was introduced after the deposition of GaAs cap layer, which is thinner than the mean height of Quantum dots. Uniformity of quantum dots has been enhanced because the full width of half maximum of photoluminescence decrease from 80meV to 27meV in these samples as the interruption time increasing from 0 to 120 second. Meanwhile, we have observed that the peak position of photoluminescence is a function of interruption time. This effect can be used to control the energy level of quantum dots. The phenomena mentioned above can be attributed to the diffusion of In atoms from the top of InAs islands to the top of GaAs cap layer caused by the difference of surface energies between InAs and GaAs.

The enhancement of diffusion by strain of InAs quantum dots in a GaAs matrix

We investigate the annealing behavior of Photoluminescence (PL) from self-assembled InAs quantum dots (QDs) with different thicknesses GaAs cap layers. The diffusion introduced by annealing treatment results in a blue-shift of the QD PL peak, and a decrease in the integrated intensity. The strain present in QDs enhances the diffusion, and the QDs with the cap layers of different thicknesses will experience a strain of different strength. This can lend to a, better understanding of the larger blue-shift of the PL peak of the deeper buried QDs, and the different variance of the full width at half maximum of the luminescence from QDs with the cap layers of different thicknesses.

KOPIDE：长白山北坡阔叶红松林生长与演替的计算机模型

由于森林生态系统的复杂性，过去常用统计回归模型模拟它的各种动态现象。但这样的模型不能揭示森林生态系统的内在规律，故可称之为“黑箱”模型。随着对森林生态系统认识的加深，以及电子计算机技术的广泛应用，用来模仿森林生态系统内在结构与功能规律的各种计算机模型得到了极大发展，从而产生一些不同“灰化”程度的森林动态“仿真”模型。本文建立的阔叶红松林生长与演替计算模型（DOPIDE）就属于这样的“灰箱”模型。KOPIDE（for KOrean PIne'DEciduous mixed forests）是在JABOWA（Botkin, 1972）和FORET（Shugart等，1977）两个模型的基础上建立的，它们都可称为GAP模型。KOPIDE模型共涉及八个树种：红松（Pinus koraiensis）、水曲柳（Fraxinus mandshurica）、紫椴（Tilia amurensis）、春榆（Ulmus japonica）、蒙古柞（Quercus mongolica）、色木（Acer mono）、白桦（Betula platyphylla）、以及山杨（Populus davidiana）。建立该模型的理论基础是森林演替的林窗（CAP）动态理论，它以一年的步长模拟了样地里每株树木的整个生长发育过成（即更新、生长和枯死）。虽然KOPIDE是JABOWA和FORET的直接效仿模型，但它的模拟针对性较强，在模型的结构上有了很大改进。它的运行结果表明，KOPIDE模型在树种生物学特性的描写上、在阔叶红松林动态规律的模拟上、以及在择伐生长的预测上都有较好的可靠性，可用来揭示阔叶红松林长时期的更新、生长和演替规律与特征，也可模拟阔叶红松林的各种经营方式，为决策人提供预测性结果，以供参考。经过KOPIDE模型的反复运行与调试，发现各树种在更新、枯死与林窗大小的关系上很不相同。根据这种现象，可将树种划分为四类：1、在较大的林窗下更新，枯死后不产生大林窗；2、更新不需要林窗，死亡后产生的林窗较大；3、更新需要林窗条件，枯死后不产生林窗；4、不在林窗下更新，死亡后也不产生林窗。尽管这样的建有点绝对化和简单化，但从中可以得出几类树种之间复杂的相互关系网。由此把复杂森林生态系统大范围的动态变化过程视为组成其许多同质或异质小林地单元的动态相嵌。林地单元的同质性，决定了它们动态变化的同步性，从而导致整个林分动态的突性或不稳定性；而林地单元的异质性是决定森林生态系统稳定性的关键性因素。这从另一角度为在东北东部山地和发展阔叶红松林提供了较有说服力的理论基础。

关于固体表面上液体球冠的平衡条件问题——兼评“冷凝器壁面滴状冷凝的热力学机理及最佳接触角”等文章

对于第一类液滴(尺度远大于界面层的厚度),无论是远离固体壁面的液体球或附着在壁面上的球冠,其内外压力差(简称"附加压力")均适用经典Laplace公式,并且特别对球冠情况给出了一种新的整体性证明.还澄清有关争论:指出[曹治党、郭愚1999物理学报481823]一文对附壁面第一类液体球冠所推导出的附加压力与接触角有关的公式是错误的,而[闵敬春2002物理学报512730]是正确的。

Rapid detection of porcine circovirus type 2 by loop-mediated isothermal amplification

A method of loop-mediated isothermal amplification (LAMP) was employed to develop a rapid and simple detection system for porcine circovirus type 2 (PCV2). The amplification could be finished in 60 min under isothermal condition at 64 degrees C by employing a set of four primers targeting the cap gene of PCV2. The LAMP assay showed higher sensitivity than the conventional PCR, with a detection limit of five copies per tube of purified PCV2 genomic DNA. No cross-reactivity was observed from the samples of other related viruses including porcine circovirus type 1 (PCV1), porcine parvovirus (PPV), porcine pseudorabies virus (PRV) and porcine reproductive and respiratory syndrome virus (PRRSV). The detection rate of PCV2 LAMP for 86 clinical samples was 96.5% and appeared greater than that of the PCR method. The LAMP assay reported can provide a rapid yet simple test of PCV2 suitable for laboratory diagnosis and pen-side detection due to ease of operation and the requirement of only a regular water bath or heat block for the reaction. (c) 2008 Elsevier B.V. All rights reserved.

Decomposition of Noncommutative U(1) Gauge Potential

We investigate the decomposition of noncommutative gauge potential (A) over cap (i), and find that it has inner structure, namely, (A) over cap (i) can he decomposed in two parts, (b) over cap (i) and (a) over cap (i), where (b) over cap (i) satisfies gauge transformations while (a) over cap (i) satisfies adjoint transformations, so close the Seiberg-Witten mapping of noncommutative, U(1) gauge potential. By, means of Seiberg-Witten mapping, we construct a mapping of unit vector field between noncommutative space and ordinary space, and find the noncommutative U(1) gauge potential and its gauge field tensor can be expressed in terms of the unit vector field. When the unit vector field has no singularity point, noncommutative gauge potential and gauge field tensor will equal ordinary gauge potential and gauge field tensor

LAS对菲在土壤(柱)中的迁移影响

The migration of phenanthrene and factors affecting its migration in soil in presence of LAS are studied through the simulation of soil column. Results show that:① Through 180 days of leaching, when the LAS concentration is 0.5 or 5mg·L *.1, the phenanthrene residual rate is less than 10 percent and the residue distributes mainly in surface soil(0-5cm);② When LAS concentration is 0.5mg·L *.1, the phenanthrene residual rate in soil is 3-8 times that of LAS concentration being 5mg·L *.1;③ The phenanthrene residual rate in soil is 2.5-6 times that of soil that with organic matter removed.It's shown that the LAS concentration has obvious effect for the phenanthrene residual rate in soil and the organic matter in soil has good cap ability in keeping phenanthrene.

基于传统生态足迹方法和能值生态足迹方法的黑龙江省可持续发展状态比较

运用传统生态足迹方法及其改进方法——能值生态足迹方法,对2005年黑龙江省可持续发展状态进行了分析.结果表明:2005年,采用能值生态足迹方法和传统生态足迹方法计算的黑龙江省生态赤字分别为1.919和0.6256hm2.cap-1.2种方法得到的研究区生态足迹均超过生态承载力,表明该区域经济社会发展处于一种不可持续的发展状态.能值生态足迹方法从能量角度探讨了人类物质需求与生态系统资源供应的关系,并采用能值转换率、能值密度等更加稳定的参数进行计算,一定程度上克服了传统生态足迹方法的缺陷.

Genomic organization, nucleotide sequence analysis of the core histone genes cluster in Chlamys farreri and molecular evolution assessment of the H2A and H2B

This work represents the nucleotide sequence of the core histone gene cluster from scallop Chlamys farreri. The tandemly repeated unit of 5671 bp containing a copy of the four core histone genes H4, H2B, H2A and H3 was amplified and identified by the techniques of homology cloning and genomic DNA walking. All the histone genes in the cluster had the structures in their 3' flanking region which related to the evolution of histone gene expression patterns throughout the cell cycle, including two different termination signals, the hairpin structure and at least one AATAAA polyadenylation signal. In their 5' region, the transcription initiation sites with a conserved sequence of 5'-PyATTCPu-3' known as the CAP site were present in all genes except to H2B, generally 37-45 bp upstream of the start code. Canonical TATA and CAAT boxes were identified only in certain histone genes. In the case of the promoters of H2B and H2A genes, there was a 5'-GATCC-3' element, which had been found to be essential to start transcription at the appropriate site. After this element, in the promoter of H2B, there was another sequence, 5'-GGATCGAAACGTTC-3', which was similar to the consensus sequence of 5'-GGAATAAACGTATTC-3' corresponding to the H2B-specific promoter element. The presence of enhancer sequences (5'-TGATATATG-3') was identified from the H4 and H3 genes, matching perfectly with the consensus sequence defined for histone genes. There were several slightly more complex repetitive DNA in the intergene regions. The presence of the series of conserved sequences and reiterated sequences was consistent with the view that mollusc histone gene cluster arose by duplicating of an ancestral precursor histone gene, the birth-and-death evolution model with strong purifying selection enabled the histone cluster less variation and more conserved function. Meanwhile, the H2A and the H2B were demonstrated to be potential good marks for phylogenetic analysis. All the results will be contributed to the characterization of repeating histone gene families in molluscs.

拓扑异构酶的结构、功能与进化的结构生物信息学研究

拓扑异构酶（topoisomerase）是一类控制和修改双螺旋DNA复制和转录过程中的拓扑结构的酶，是生命活动中最重要的酶。以IA类和II类拓扑异构酶中共存的toprim以及CAP-like结构域为研究对象，对拓扑异构酶中的三大类酶的分子进化情况进行了分析。结果显示在IA类和II类酶之间序列保守性很低，但是具有两个保守的结构域，在IIB类拓扑异构酶中toprim结构域中存在着和其他toprim结构域相同的四个保守位点，而在CAP-like结构域中IA类和II类中存在较大差异，没有明显的序列保守性，IIB类和IIA类的CAP-like结构域在二级结构上非常相似。从toprim结构域系统进化研究中我们发现IIA类和皿类中toprim结构域的进化关系很近，两类酶的toprim结构域在亲缘关系上和primase较远，而以上三者和IA类的进化关系最远。CAP-like结构域的系统进化研究发现IIA类以及IA类的domain4的CAP-like结构域进化关系比较近，IIB类和他们之间关系稍微远一些，IA类的domain3和以上几个结构域的关系较远，这也与他们的二级结构上的一致性是相同的。通过分析，IIA、IIB类起源于类似IA类的古老的拓扑异构酶，'在IA类进化中经过基因复制产生了两个不同的CAP-like结构域。然后祖先拓扑异构酶发生了变化，N'端加入了ATPase结构域和DNAgyrase/Mutlsecond结构域，形成了严格依赖ATP供能的真核生物IIA类，在细菌中断开成为两个亚基的细菌中IIA类。IIB类是祖先细胞的IIA类的一个或者是两个亚单位在古细菌以及真核生物中通过复制、重组和缺失造成的，IIB类中的toprim结构域很接近IIA类，可以认为，llB类中的toPrim结构域直接由IIA类转移而来，而IIB类中的cAP一1汰e结构域较IIA类中产生更早一些，应该是由拓扑异构酶祖先中产生的二级结构为aβaaββ的CAP-like结构域直接进化而来。然而，两个结构域的基因在连接到一起时候发生了不同于一般顺序的拼接，于是nB类中两个结构域形成了不同于现在的IA类和IIA类的顺序。

Synthesis, crystal structure, and magnetic properties of {[Cu(oxbe)]Mn(H2O)[Cu(oxbe)(DMF)]}(n)center dot nDMF center dot nH(2)O: From dissymmetrical mononuclear entities to a 3D heterometallic supramolecular coordination polymer

Self-assembly of the building block [Cu(oxbe)](-) with Mn(II) led to a novel coordination polymer {[Cu(oxbe)]Mn(H2O)(Cu(oxbe)(DMF)]}(n).nDMF.nH(2)O, where H(3)oxbe is a new dissymmetrical ligand N-benzoato-N'-(2-aminoethyl)-oxamido and DMF = dimethylformamide. The crystal forms in the triclinic system, space group P(1)over-bar, with a = 9.260(4) angstorm, b = 12.833(5) angstrom, c = 15.274(6) angstrom , alpha = 76.18(3)degrees, beta = 82.7(3)degrees, gamma = 82.31(3)degrees, and Z = 2. The crystal structure of the title complex reveals that the two-dimensional bimetallic layers are constructed of (CuMnII)-Mn-II-Cu-II chains linked together by carboxylate bridge and hydrogen bonds help to produce a novel three-dimensional channel-like structure. The magnetic susceptibility measurements (5-300 K) were analyzed by means of the Hamiltonian (H)over-cap = -2J(S)over-cap (Mn)((S)over-cap(Cu1) + (S)over-cap(Cu2)), leading to J = -17.4 cm(-1).

Active components and mechanism of isobutane alkylation with butenes in the catalytic system of HPAs plus AcOH

The catalytic active phase (CAP) of a novel liquid catalyst for isobutane alkylation with butenes was investigated, the composition of the CAP was analysized, The components of the catalytic active phase were separated and examined by the methods of FTIR, UV and NMR etc., On the basis of these results, a reaction mechanism based on the formation of protonated heteropolyacid as an intial stage in the isobutane alkylation with butenes was postulated, which is in agreement with the experimental results.

Topographic changes in nascent and early mesoderm in amphioxus embryos studied by Dil labeling and by in situ hybridization for a Brachyury gene

In amphioxus embryos, the nascent and early mesoderm (including chorda-mesoderm) was visualized by expression of a Brachyury gene (AmBra-2). A band of mesoderm is first detected encircling the earliest (vegetal plate stage) gastrula sub-equatorially. Soon thereafter, the vegetal plate invaginates. resulting in a cap-shaped gastrula with the mesoderm localized at the blastoporal lip and completely encircling the blastopore. As the gastrula stage progresses, DiI (a vital dye) labeling demonstrates that the entire mesoderm is internalized by a slight involution of the epiblast into the hypoblast all around the perimeter of the blastopore. Subsequently. during the early neurula stage, the internalized mesoderm undergoes anterior extension mid-dorsally (as notochord) and dorsolaterally (in paraxial regions when segments will later form). By the late neurula stage, AmBra-2 is no longer transcribed throughout the mesoderm as a whole; instead. expression is detectable only in the posterior mesoderm and in the notochord, but not in par axial mesoderm where definitive somites have formed.