基于EPC Class-1 Gen-2标准的防冲突算法与改进

针对RFID读写器识别多标签过程中出现的冲突问题,研究并实现了EPC Class-1 Gen-2标准中的防冲突算法,即时隙随机算法(SR算法),同时针对SR算法的不足提出改进算法。改进算法采用不避让冲突时隙的处理方式,降低了由时隙的随机选取所导致的标签间冲突的概率。实验结果证明,改进后的算法在通信次数和吞吐率方面均优于原算法,有效提高标签识别效率。

HLA-DRB1、-DQB1基因多态性与食管鳞癌遗传关联性

目的　从基因水平探讨食管鳞癌HLA DRB1 , DQB1等位基因的遗传易感性 ,以阐述其免疫遗传学特征。方法　运用序列特异性引物聚合酶链反应技术 ,检测无亲缘关系湖北汉族健康人 1 36例、食管鳞癌患者 42例的HLA DRB1 , DQB1等位基因。结果　湖北汉族人食管鳞癌患者与正常人比较 ,HLA DRB1 0 90 1等位基因分布频率显著增高 (0 .2 50 0比 0 .1 397,P =0 .0 2 8,OR =2 .0 53 ,病因分数 =0 .1 2 82 ) ,HLA DQB1 0 30

The Experimental and Numerical Studies on Gas Production from Hydrate Reservoir by Depressurization

A set of experimental system to study hydrate dissociation in porous media is built and some experiments on hydrate dissociation by depressurization are carried out. A mathematical model is developed to simulate the hydrate dissociation by depressurization in hydrate-bearing porous media. The model can be used to analyze the effects of the flow of multiphase fluids, the kinetic process and endothermic process of hydrate dissociation, ice-water phase equilibrium, the variation of permeability, convection and conduction on the hydrate dissociation, and gas and water productions. The numerical results agree well with the experimental results, which validate our mathematical model. For a 3-D hydrate reservoir of Class 3, the evolutions of pressure, temperature, and saturations are elucidated and the effects of some main parameters on gas and water rates are analyzed. Numerical results show that gas can be produced effectively from hydrate reservoir in the first stage of depressurization. Then, methods such as thermal stimulation or inhibitor injection should be considered due to the energy deficiency of formation energy. The numerical results for 3-D hydrate reservoir of Class 1 show that the overlying gas hydrate zone can apparently enhance gas rate and prolong life span of gas reservoir.

Homologous feeder cells support undifferentiated growth and pluripotency in monkey embryonic stem cells

In the present study, five homologous feeder cell lines were developed for the culture and maintenance of rhesus monkey embryonic stem cells (rESCs). Monkey ear skin fibroblasts (MESFs), monkey oviductal fibroblasts (MOFs), monkey follicular granulosa fibroblast-like (MFG) cells, monkey follicular granulosa epithelium-like (MFGE) cells, and clonally derived fibroblasts from MESF (CMESFs) were established and compared with the ability of mouse embryonic fibroblasts (MEFs) to support rESC growth. MESF, MOF, MFG, and CMESF cells, but not MFGE cells, were as good as or better than MEFs in supporting undifferentiated growth while maintaining the differentiation potential of the rESCs. In an effort to understand the unique properties of supportive feeder cells, expression levels for a number of candidate genes were examined. MOF, MESF, and MEF cells highly expressed leukemia inhibitory factor, ciliary neurotrophic factor, basic fibroblast growth factor, stem cell factor, transforming growth factor PI, bone morphogenetic protein 4, and WNT3A, whereas WNT2, WNT4, and WNT5A were downregulated, compared with MFGE cells. Additionally, all monkey feeder cell lines expressed Dkk1 and LRP6, antagonists of the WNT signaling pathway, but not WNT1, WNT8B, or Dkk2. rESCs grown on homologous feeders maintained normal karyotypes, displayed the characteristics of ESCs, including morphology, alkaline phosphatase, Oct4, the cell surface markers stage-specific embryonic antigen (SSEA)-3, SSEA-4, tumor-related antigen (TRA)-1-60, and TRA-1-81, and formed cystic embryoid bodies in vitro that included differentiated cells representing the three major germ layers. These results indicate that the four homologous feeder cell lines can be used to support the undifferentiated growth and maintenance of pluripotency in rESCs.

人类白细胞抗原-DRB1与胃腺癌及其临床特征和幽门螺杆菌感染的相关性

目的　探讨人类白细胞抗原 (HLA) DRB1等位基因与胃腺癌及其临床特征和幽门螺杆菌(Hp)感染的关联性。方法　运用序列特异性引物聚合酶链反应和等位基因序列分析技术 ,检测无亲缘关系湖北省汉族健康人 136例、胃癌组 6 3例的HLA DRB1基因。内镜活检、Giemsa染色和 (或 )外周血ELISA检查胃黏膜Hp感染情况。SAS软件数据处理。 结果　HLA DRB10 90 1、12等位基因均与湖北省汉族人胃腺癌呈正相关 ;HLA DRB115等位基因则呈负相关。携带及非携带上述各等位基因患者 ,分

Identification and characterization of a new class of human immunodeficiency virus type 1 recombinants comprised of two circulating recombinant forms, CRF07_BC and CRF08_BC, in China

We identified a new class of human immunodeficiency virus type 1 (HIV-1) recombinants (00CN-HH069 and 00CN-HH086) in which further recombination occurred between two established circulating recombinant forms (CRFs). These two isolates were found among 57 HIV-1 samples from a cohort of injecting drug users in eastern Yunnan Province of China. Informative-site analysis in conjunction with bootscanning plots and exploratory tree analysis revealed that these two strains were closely related mosaics comprised of CRF07_BC and CRF08_BC, which are found in China. The genotype screening based on gag-reverse transcriptase sequences if 57 samples from eastern Yunnan identified 47 CRF08_BC specimens (82.5%), 5 CRF07_BC specimens (8.8%), and 3 additional specimens with the novel recombinant structure. These new "second-generation" recombinants thus constitute a substantial proportion (5 of 57; 8.8%) of HIV-1 strains in this population and may belong to a new but yet-undefined class of CRF. This might be the first example of CRFs recombining with each other, leading to the evolution of second-generation inter-CRF recombinants.

HLA-DRB1与胃腺癌临床特征及Hp感染关联性研究

<正> 人类主要组织相容性复合体(major histocompatibility complex,MHC)即人类白细胞抗原(human leucocyte antigen,HLA)复合体,定位于人第6号染色体短臂(6p23)上,具有单倍体(haplotype)遗传、高度多态性(polymorphism)、连锁不平衡(linkage disequilibrium)等遗传特征。我们运用序列特异性引物聚合酶链反应(sequence specific primer based polymerase chain

Syndiotactically enriched 1,2-selective polymerization of 1,3-butadiene initiated by iron catalysts based on a new class of donors

A series of phosphoryl (P=O) contained compounds: triethylphosphate (a), diethyl phenyl phosphate (b), ethyldiphenylphosphate (c) triarylphosphates (d and h-m), triphenylphosphine oxide (e), phenyl diphenylphosphinate (f) and diphenyl phenylphosphonate (g) have been prepared. Iron catalysts, which are generated in situ by mixing the compounds with Fe(2-EHA)(3) and (AlBu3)-Bu-i in hexane, are tested for butadiene polymerization at 50 degrees C. Phosphates donated catalysts have been, unprecedently, found to conduct extremely high syndiotactically (pentad, rrrr=46.1-94.5%) enriched 1,2-selective (1,2-structure content=56.2-94.3%) polymerization of butadiene.

STUDIES ON INCREASING THE ACTIVITY OF SELENIUM-CONTAINING ABZYME .1. SYNTHESIS, CHARACTERIZATION AND PROPERTIES OF HAPTEN AND ANTIGEN

The thiol group of glutathione (GSH) reacts specifically with 2,4-di-ni-trochlorobenzene to give S-substituted dinitrophenyl glutathione (GSH-S-DNP); two carboxyl groups of GSH-S-DNP were further esterified by n-butanol to produce the hapten, multisubstrate analog GSH-S-DNP Butyl Ester (GSH-S-DNP BE). The primary structure of the hapten was characterized by the free. amino group analysis, H-1 NMR, IR determinations and the elemental analysis. The hapten was then conjugated to bovine serum albumin (BSA) in the presence of glutaraldehyde. The reaction mixture was purified by Ultrogel AcA54 colum chromatography to give the antigen. On an average, 25 haptens were bound to each BSA molecule. Electrophoresis analysis showed that the average molecular weight of the antigen was 87 KD. CD spectrum showed that the a-helix content of the antigen increased.

Two-Dimensional Kinetics Of Beta(2)-Integrin And Icam-1 Bindings Between Neutrophils And Melanoma Cells In A Shear Flow

Cell adhesion, mediated by specific receptor-ligand interactions, plays an important role in biological processes such as tumor metastasis and inflammatory cascade. For example, interactions between beta(2)-integrin ( lymphocyte function-associated antigen-1 and/or Mac-1) on polymorphonuclear neutrophils (PMNs) and ICAM-1 on melanoma cells initiate the bindings of melanoma cells to PMNs within the tumor microenvironment in blood flow, which in turn activate PMN-melanoma cell aggregation in a near-wall region of the vascular endothelium, therefore enhancing subsequent extravasation of melanoma cells in the microcirculations. Kinetics of integrin-ligand bindings in a shear flow is the determinant of such a process, which has not been well understood. In the present study, interactions of PMNs with WM9 melanoma cells were investigated to quantify the kinetics of beta(2)-integrin and ICAM-1 bindings using a cone-plate viscometer that generates a linear shear flow combined with a two-color flow cytometry technique. Aggregation fractions exhibited a transition phase where it first increased before 60 s and then decreased with shear durations. Melanoma-PMN aggregation was also found to be inversely correlated with the shear rate. A previously developed probabilistic model was modified to predict the time dependence of aggregation fractions at different shear rates and medium viscosities. Kinetic parameters of beta(2)-integrin and ICAM-1 bindings were obtained by individual or global fittings, which were comparable to respectively published values. These findings provide new quantitative understanding of the biophysical basis of leukocyte-tumor cell interactions mediated by specific receptor-ligand interactions under shear flow conditions.

Evolution and propagation of density waves on galactic disk .1. General evolution equation of wavelet and discussion of its solution

This paper presents a general self-consistent theory of evolution and propagation of wavelets on the galactic disk. A simplified model for this theory, i. e. the thin transition-layer approximation is proposed.There are three types of solutions to the basic equation governing the evolution of wavelets on the disk: (ⅰ) normal propagating type; (ⅱ) swing type; (ⅲ) general evolving type. The results show that the first two types are applicable to a certain domain on the galactic disk and a certain region of the wave number of wavelets. The third is needed to join the other two types and to yield a coherent total picture of the wave motion. From the present theory, it can be seen that the well-known "swing theory" of the G-L sheet model holds only for a certain class of basic states of galaxies.

Study of Interaction Force between Antigen and Antibody Using Flow Chamber Method

A parallel plate flow chamber was used to study the interaction force between human IgG (immobilized on a chip surface as ligand) and goat anti-human IgG (immobilized on microspheres surface as receptor). First, it was demonstrated that the binding force between the microspheres and the chip surface came from the bio-specific interaction between the antigen and the antibody. Secondly, it was obtained that the critical shear rate to detach microspheres from the chip surface increases with the ligand surface concentration. Finally, two models to estimate the antigen-antibody bond strength considering bonds' positions were proposed and analyzed.

Development of arc root attachment in the nozzle of 1 kW N2 and H2-N2 arcjet thrusters

Arc root behavior affects the energy transfer and nozzle erosion in an arcjet thruster. To investigate the development of arc root attachment in 1 kW class N2 and H2-N2 arcjet thrusters from the time of ignition to the stably working condition, a kinetic series of end-on view images of the nozzle obtained by a high-speed video camera was analyzed. The addition of hydrogen leads to higher arc voltage levels and the determining factor for the mode of arc root attachment was found to be the nozzle temperature. At lower nozzle temperatures, constricted type attachment with unstable motions of the arc root was observed, while a fully diffused and stable arc root was observed at elevated nozzle temperatures.

Detection of constitutive heterodimerization of the integrin Mac-1 subunits by fluorescence resonance energy transfer in living cells

Macrophage differentiation antigen associated with complement three receptor function (Mac-1) belongs to beta(2) subfamily of integrins that mediate important cell-cell and cell-extracellular matrix interactions. Biochemical studies have indicated that Mac-1 is a constitutive heterodimer in vitro. Here, we detected the heterodimerization of Mac-1 subunits in living cells by means of two fluorescence resonance energy transfer (FRET) techniques (fluorescence microscopy and fluorescence spectroscopy) and our results demonstrated that there is constitutive heterodimerization of the Mac-1 subunits and this constitutive heterodimerization of the Mac-1 subunits is cell-type independent. Through FRET imaging, we found that heterodimers of Mac-1 mainly localized in plasma membrane, perinuclear, and Golgi area in living cells. Furthermore, through analysis of the estimated physical distances between cyan fluorescent protein (CFP) and yellow fluorescent protein (YFP) fused to Mac-1 subunits, we suggested that the conformation of Mac-1 subunits is not affected by the fusion of CFP or YFP and inferred that Mac-1 subunits take different conformation when expressed in Chinese hamster ovary (CHO) and human embryonic kidney (HEK) 293T cells, respectively. (c) 2006 Elsevier Inc. All rights reserved.

Interaction between single molecules of Mac-1 and ICAM-1 in living cells: An atomic force microscopy study

The interaction between integrin macrophage differentiation antigen associated with complement three receptor function (Mac-1) and intercellular adhesion molecule-1 (ICAM-1), which is controlled tightly by the ligand-binding activity of Mac-1, is central to the regulation of neutrophil adhesion in host defense. Several "inside-out" signals and extracellular metal ions or antibodies have been found to activate Mac-1, resulting in an increased adhesiveness of Mac-1 to its ligands. However, the molecular basis for Mac-1 activation is not well understood yet. In this work, we have carried out a single-molecule study of Mac-1/ICAM-1 interaction force in living cells by atomic force microscopy (AFM). Our results showed that the binding probability and adhesion force of Mac-1 with ICAM-1 increased upon Mac-1 activation. Moreover, by comparing the dynamic force spectra of different Mac-1 mutants, we expected that Mac-1 activation is governed by the downward movement of its alpha 7 helix. (c) 2007 Elsevier Inc. All rights reserved.