鱼类的天然雌核发育

<正> 1.孤雌生殖,雌核发育和杂合发育单性型种群在脊椎动物中是罕见的。尽管如此,到目前为止几乎已在各类脊椎动物中发现了单性型种群。该种群通常涉及3种繁殖方式,即孤雌生殖(parthenogenesis)、雌核发育(gynogenesis)和杂合发育(hybridogenesis)。

Zebrafish peptidoglycan recognition protein SC (zfPGRP-SC) mediates multiple intracellular signaling pathways

Insect PGRPs can function as bacterial recognition molecules triggering proteolytic and/or signal transduction pathways, with the resultant production of antimicrobial peptides. To explore if zebrafish peptidoglycan recognition protein SC (zfPGRP-SC) has such effects, RNA interference (siRNA) and high-density oligonucleotide microarray analysis were used to identify differentially expressed genes regulated by zfPGRP-SC. The mRNA levels for a set of genes involved in Toll-like receptor signaling pathway, such as TLRs, SARM, MyD88, TRAF6 and nuclear factor (NF)-kappa B2 (p100/p52), were examined by quantitative RT-PCR (QT-PCR). The results from the arrays and QT-PCR showed that the expression of 133 genes was involved in signal transduction pathways, which included Toll-like receptor signaling, Wnt signaling, BMP signaling, insulin receptor signaling, TGF-beta signaling, GPCR signaling, small GTPase signaling, second-messenger-mediated signaling, MAPK signaling, JAK/STAT signaling, apoptosis and anti-apoptosis signaling and other signaling cascades. These signaling pathways may connect with each other to form a complex network to regulate not just immune responses but also other processes such as development and apoptosis. When transiently over-expressed in HEK293T cells, zfPGRP-SC inhibited NF-kappa B activity with and without lipopolysacharide (LPS) stimulation. (C) 2008 Elsevier Ltd. All rights reserved.

Characterization of development-related genes for the cestode Bothriocephalus acheilognathi

Differential gene expression of mature and immature Bothriocephalus acheilognathi cestodes was analyzed using the suppression subtractive hybridization technique. Five mature-associated cDNAs were isolated and characterized. Virtual Northern blot and RT-PCR analyses confirmed that four of the five genes were up-regulated in mature parasites. The sequence analysis revealed that one gene encoded the structural protein chorion precursor, and that three encoded functional proteins homologous to yolk ferritin, sodium/hydrogen exchanger and muscin-like protein. Another gene appeared to be specific to B. acheilognathi, encoding a putative metal-bound protein. Although results obtained in the present study are preliminary, the information about the five genes may provide clues for further investigation on the decline in parasite numbers during the maturation of B. acheilognathi.

Sequence of genome segments 1, 2, and 3 of the grass carp reovirus (Genus Aquareovirus, family Reoviridae)

The genome segments 1, 2, and 3 of the grass carp reovirus (GCRV), a tentative species assigned to genus Aquareouirus, family Reouiridae, were sequenced. The respective segments 1, 2, and 3 were 3949, 3877, and 3702 nucleotides long. Conserved moths 5' (GUUAUUU) and 3' (UUCAUC) were found at the ends of each segment. Each segment contains a single ORF and the negative strand does not permit identification of consistent ORFs. Sequence analysis revealed that VP2 is the viral polymerase, while VPI might represent the viral guanyly/methyl transferase (involved in the capping process of RNA transcripts) and VP3 the NTPase/helicase (involved in the transcription and capping of viral RNAs), The highest amino acid identities (26-41%) were found with orthoreovirus proteins. Further genomic characterization should provide insight about the genetic relationships between GCRV, aquareoviruses, and orthoreoviruses, It should also permit to precise the taxonomic status of these different viruses. (C) 2000 Academic Press.

Electronic structure and optical property of semiconductor nanocrystallites

Semiconductor nanostructures show many special physical properties associated with quantum confinement effects, and have many applications in the opto-electronic and microelectronic fields. However, it is difficult to calculate their electronic states by the ordinary plane wave or linear combination of atomic orbital methods. In this paper, we review some of our works in this field, including semiconductor clusters, self-assembled quantum dots, and diluted magnetic semiconductor quantum dots. In semiconductor clusters we introduce energy bands and effective-mass Hamiltonian of wurtzite structure semiconductors, electronic structures and optical properties of spherical clusters, ellipsoidal clusters, and nanowires. In self-assembled quantum dots we introduce electronic structures and transport properties of quantum rings and quantum dots, and resonant tunneling of 3-dimensional quantum dots. In diluted magnetic semiconductor quantum dots we introduce magnetic-optical properties, and magnetic field tuning of the effective g factor in a diluted magnetic semiconductor quantum dot. (C) 2004 Elsevier B.V. All rights reserved.

The quantum tunneling between two-component Bose-Einstein condensates in a double-well configuration

In terms of exact solution of the time-dependent Schrodinger equation. we examine the quantum tunneling process in Bose condensates of two interacting species trapped in a double well configuration. We use the two series of time-dependent SU(2) gauge transformation to diagonalize the Hamilton operator obtain analytic time-evolution formulas of the population imbalance and the berry phase. The particle population imbalance (a(L)(+)a(L) - a(R)(+)a(R)) of species A between the two wells is studied analytically.

Structural and optical properties of InAs/GaAs quantum dots emitting at 1.5 mu m

We have demonstrated 1.5 mum light emission from InAs quantum dots (QDs) capped with a thin GaAs layer. The extension of the emission wavelength can be assigned to the large QD height. We also investigate the effect of growth interruption on the PL properties and the shape of InAs QDs fabricated by migration-enhanced growth (MEG). Contrary to expectation, we observed a remarkable blueshift of the emission energy with the growth interruption in MEG mode. Detailed investigations reveal that the blueshift is related to the reduced island height with the growth interruption, which is confirmed by reflection high-energy electron diffraction (RHEED) patterns and atomic force microscopy (AFM) measurement results. Accordingly, the structure changes of the islands are interpreted in terms of thermodynamic and kinetic theories. (C) 2004 Elsevier B.V. All rights reserved.

Structure optimization of field-plate AlGaN/GaN HEMTs

AlGaN/GaN high electron mobility transistors (HEMTs) on 6H-SiC with varying field-plate length and gate-drain spacing were fabricated and analyzed. The classical small signal FET model and the well-known ColdFET method were used to extract the small signal parameters of the devices. Though the devices with field plates exhibited lower better f(T) characteristic, they did demonstrate better f(max), MSG and power density performances than the conventional devices without field plate. Besides, no independence of DC characteristic on field-plate length was observed. With the increase of the field-plate length and the gate-drain spacing, the characteristic of f(T) and f(max), degraded due to the large parasitic effects. Loadpull method was used to measure the microwave power performance of the devices. Under the condition of continuous wave at 5.4 GHz, an output power density of 4.69 W/mm was obtained for device with field-plate length of 0.5 mu m and gate-drain length of 2 mu m. (c) 2006 Elsevier Ltd. All rights reserved.

In0.25Ga0.75As films growth on the thin GaAs/AlAs buffer layer on the GaAs(001) substrate

Thin GaAs/AlAs and GaAs/GaAs buffer layer structure have been fabricated on the GaAs(001) substrate. The top GaAs buffer layer is decoupled from the host substrate by introduction of a low temperature thin interlayer (AlAs or GaAs), which was mechanically behaved like the compliant substrate. Four hundred nanometer In0.25Ga0.75As films were grown on these substrates and the traditional substrate directly. Photoluminescence (PL), double-crystal X-ray diffraction (DCXRD) and atomic force microscopy (AFM) measurements were used to estimate the quality of the In0.25Ga0.75As layer and the compliant effects of the low temperature buffer layer. All the measurements shown that the qualities of epilayer have been improved and the substrate have been deteriorated severely. The growth technique of the thin GaAs/AlAs structure was found to be simple but very powerful for heteroepitaxy. (C) 2003 Elsevier Science B.V All rights reserved.

Content analyses in GaMnAs by double-crystal X-ray diffraction

A model for analyzing point defects in compound crystals was improved. Based on this modified model, a method for measuring Mn content in GaMnAs was established. A technique for eliminating the zero-drift-error was also established in the experiments of X-ray diffraction. With these methods, the Mn content in GaMnAs single crystals fabricated by the ion-beam epitaxy system was analyzed.

Growing process of CdS nanoclusters in zeolite Y studied by positron annihilation

Zeolite Y has been used as the host to generate CdS nanoclusters. The location of CdS nanoclusters inside zeolite hosts was confirmed by the blue-shifted reflection absorption spectra with respect to that of bulk CdS materials. But which kind of cage inside zeolite Y, sodalite cage or supercage, was preferred for the CdS clusters remained unclear. In this paper, we conducted positron annihilation spectroscopy (PAS) measurements for the first time on a series of CdS/Y zeolite samples and concluded that CdS clusters were not located in supercages but in smaller sodalite cages. The stability of CdS clusters inside the sodalite units was due to the coordination of Cd atoms with the framework oxygen atoms of the double six-ring windows. Moreover, PAS revealed some important information of surface states existing on the interfacial layers between CdS clusters and zeolite Y. (C) 2001 Elsevier Science B,V, All rights reserved.

High-quality-factor EH modes in microcylinder resonators predicted by 3D FDTD simulation

The mode characteristis of a microcylinders with center layer thickness 0.2 mu m and radius 1 mu m are investigated by the three-dimensional (31)) finite-difference time-domain (FDTD) technique and the Pade approximation. The mode quality factor (Q-factor) of the EH71 mode obtained by 3D FDTD increase with the increase of the refractive index of the cladding layer n(2) as n(2) smaller than 3.17, and can be as large as 2.4 x 10(4) as the vertical refractive index distribution is 3.17/3.4/3.17, which is much larger than that of the HE71 mode with the same vertical refractive index distribution.

高效DOM实现的技术研究

DOM是目前为止唯一成为W3C正式标准的XML解析模型。本文充分考虑了DOM模型的特点,设计并实现了一个高性能的支持DOM的XML解析器OnceDOMParser。为了提高DOM实现的性能,我们采用用户堆提高对象管理的效率,减少对象在JVM中创建的数量,并采取了数据的延迟装载策略。OnceDOMParser经过了严格的XML兼容性测试和DOM API兼容性测试,多方面的性能测试表明OnceDOMParser性能优越,其平均吞吐量比目前最流行的XML解析器Xerces高43.7%左右。

MPI同步通信顺序模型死锁静态检测算法

静态检测MPI程序同步通信死锁比较困难,通常需要建立程序模型.顺序模型是其他所有复杂模型的基础.通过一种映射方法将顺序模型转化为字符串集合,将死锁检测问题转化为等价的多队列字符申匹配问题,从而设计并实现了一种MPI同步通信顺序模型的静态死锁检测算法.该算法的性能优于通常的环检测方法,并能适应动态消息流.

笔式界面软件资源管理模型及其实现

针对目前文档管理模式和WIMP界面交互范式对笔式交互的不足,提出了笔式界面软件文档资源管理的统一模型,能够有效地管理笔式界面软件所产生的文档数据,并且根据此模型实现了笔式界面的文档资源管理系统,采用了PIBG交互范式和实物界面.评估结果表明,根据此模型设计的系统,能够提高用户工作效率,降低用户的认知负担.