基于代理的覆盖网组播生成树算法研究

利用覆盖网组播技术构建组播服务平台是一种可行的提供组播服务的方案.基于代理的覆盖网组播兼具覆盖网组播的灵活性和IP组播的高效性的特点.结合节点的带宽、处理延迟和节点间的通信延迟给出一个完善的基于代理的覆盖网组播模型,根据此模型设计了求节点度受限的具有最小平均延迟的组播转发树生成算法.探讨了主机节点在进行数据分组复制转发时的转发顺序对平均延迟的影响,给出并证明了主机节点对数据分组复制转发的最优策略.通过仿真实验验证了所给算法和最优复制转发策略的有效性.     

高效的基于平面的层次化应用层组播树模型

应用层组播在Internet上有着广泛的应用.本文在K-叉树结构的基础上提出了一种K-叉平面结构,同时在平面的组织上结合了分层和分簇的思想.K-叉平面结构降低了子树之间的错误关联度;分层分簇降低了组播树的深度,减少了组播管理上的复杂度;在增加一定冗余的前提下,不同平面的簇与簇之间采用小概率通信,提高了数据恢复和数据传递的效率.整体而言,组播树的健壮性得到了很好的保证.仿真实验结果证明本模型能够很好地对端用户进行管理,提高了因某些结点意外失效造成的数据恢复和应用层组播的转发效率.     

异构结构化P2P网络负载均衡方案

结构化P2P网络由于采用DHT算法导致节点存储资源的不均衡,当前解决方案都是假定节点容量及负载是均匀分布在系统中,而忽略了实际网络存在的节点异构性的影响.本文提出的考虑节点异构性的结构化P2P网络负载均衡方案提出了负载均衡的衡量标准--负载平滑度,采用基于相同资源描述符的资源整体转移方案,以节点的邻居节点为平衡范围,描述了系统在节点加入、离开,资源加入以及节点过载情况下的算法,使得整个系统逐步达到负载均衡.该方案充分考虑了实际网络中存在的异构问题.仿真实验表明,该方案有效地解决了并构P2P网络下的负载均衡问题.     

IP网络多组播流相互影响均衡问题研究

自从20世纪90年代初IP组播概念及试验网络出现以后,IP组播路由一直是互联网路由领域的研究热点,由于互联网规模的急速扩张带来的网络阻塞问题必须在新一代网络中得到较好解决.本文针对动态组播路由条件下多组播流相互影响问题展开研究,建立了多组播流优化均衡模型,并证明模型在总费用的最优解不但存在,而且唯一.简单的算例表明:相对静态组播路由,动态组播路由对网络性能有明显改善,为新一代网络和路由提供算法参考,并扩展到更加复杂网络的路由均衡研究.下一步将在典型的路由设备和具备一定规模的网络上进行验证和应用.     

一种基于链路状态组合度量的无线网状网路由协议

在分析Ad hoc网络中的经典路由协议AODV的基础上,结合无线网状网的特点,提出了基于链路加权的无线网状网路由协议MODVWLS.协议通过节点的可用带宽、缓冲队列和吞吐性能等计算每一跳的代价(即权重),选择从信源到信宿累计权重最小的路径作为路由.对链路权重计算、报文格式、路由发现和维护过程进行了详细阐述,并利用NS2对MODVWLS协议进行了仿真实现.结果表明,MODVWLS协议能合理利用空闲节点和链路资源,较好地均衡网络负载,在数据包转发率、端到端延迟和标准化路由负载等性能上均优于AODV协议.     

树链混合组播源认证协议

源认证是组播通讯面临的一个挑战性问题,必须为大量接受者提供系统开销低、可靠性高的确认数据来源的方法.本文提出了一种有效的组播源认证协议HTC,该方案结合Hash树和多Hash链方法的优点,有效地降低了通讯开销.采用二态马尔科夫丢包模型进行了大量的仿真实验,获得了一个最优的Hash跨度组合1-2-7-11-16-20-25-30.与已有多个认证方案进行比较,说明HTC是一种有效的组播源认证方案.     

基于邻近度的P2P路由算法

邻近度路由技术对P2P网络的路由性能影响很大.本文提出一种新的分布式结构化P2P路由算法FDPNS.FD-PNS路由算法采用邻近度路由技术,节点在转发一个查询请求后触发路由表的维护任务,有针对性地对本次转发使用的路由表项进行优化,以减小搜索和定位的路由延迟,提高系统的整体性能.     

基于组播和P2P的文件分发管理模块的设计与实现

本文对CNGI研究课题"组播与P2P相结合的文件分发系统"进行了简要介绍.通过对该系统文件管理模块的总体设计和详细设计,实现了基于IPv6组播与P2P技术的结合.该系统借助JxTA平台实现P2P的基本功能:节点搜索、节点资源搜索、节点间的通讯和文件的统一管理等,实现了尽量利用可靠的组播并利用P2P实现跨组播域的信息传输.最后通过对管理模块在不同环境下的测试数据进行分析,表明该设计思想的有效性.     

P2P流媒体技术研究

流媒体业务正变得日益流行,然而传统流媒体系统存在着种种不足.最近兴起的P2P技术能够利用客户端节点的资源减轻服务器和骨干网的负担,为解决流媒体内容分发提供了一个新的方向.本文首先阐述了传统流媒体系统的不足之处,以及P2P流媒体系统与之相比的优势,而后通过对P2P流媒体技术研究现状的详细调查,分析了P2P流媒体技术的两个分支--直播与点播的特性要求,并以P2P流媒体系统的典型代表为例说明了当前所采用的主流技术.最后,本文就P2P流媒体技术在应用层拓扑的建立、激励机制、安全性、无线应用以及网络编码等方面的研究进行了讨论,指出了进一步的研究方向.     

一种适用于P2P存储系统的索引管理算法

PB-link Tree通过哈希定位将B 树分布到多个节点上,解决了动态P2P环境中索引的完整性和准确性问题.实验表明,即使节点频繁加入或离开系统,仍能保持数据的可靠性和一致性.而且,PB-link Tree较之传统DB-link Tree在查询过程中数据传输量更小,查询时间更短.     

Poly(lactic acid-glycolic acid) nanoparticles markedly improve immunological protection provided by peptide P10 against murine paracoccidioidomycosis

Background and purpose:

The present study reports on the preparation and testing of a sustained delivery system for the immunomodulatory peptide P10 aimed at reducing the in vivo degradation of the peptide and the amount required to elicit a protective immune response against paracoccidioidomycosis.

Experimental approach:

BALB/c mice were infected with the yeast Paracoccidioides brasiliensis to mimic the chronic form of paracoccidioidomycosis. The animals were treated daily with sulfamethoxazole/trimethoprim alone or combined with peptide P10, either emulsified in Freund''s adjuvant or entrapped in poly(lactic acid-glycolic acid) (PLGA) nanoparticles at different concentrations (1 µg, 5 µg, 10 µg, 20 µg or 40 µg·50 µL⁻¹). Therapeutic efficacy was assessed as fungal burden in tissues and the immune response by quantitative determination of cytokines.

Key results:

Animals given combined chemotherapy and P10 nanotherapy presented a marked reduction of fungal load in the lungs, compared with the non-treated animals. After 30 days of treatment, P10 entrapped within PLGA (1 µg·50 µL⁻¹) was more effective than ‘free’ P10 emulsified in Freund''s adjuvant (20 µg·50 µL⁻¹), as an adjuvant to chemotherapy. After treatment for 90 days, the higher doses of P10 entrapped within PLGA (5 or 10 µg·50 µL⁻¹) were most effective. Treatment with P10 emulsified in Freund''s adjuvant (20 µg·50 µL⁻¹) or P10 entrapped within PLGA (1 µg·50 µL⁻¹) were accompanied by high levels of interferon-gamma in lung.

Conclusions and implications:

Combination of sulfamethoxazole/trimethoprim with the P10 peptide entrapped within PLGA demonstrated increased therapeutic efficacy against paracoccidioidomycosis. P10 incorporation into PLGA nanoparticles dramatically reduced the peptide amount necessary to elicit a protective effect.     

拉玛泽减痛分娩法联合无创接生方案对产妇分娩疼痛及并发症的影响

目的 探讨拉玛泽减痛分娩法联合无创接生方案对产妇分娩疼痛及并发症的影响.方法 选取本院收治的66例自主选择自然分娩的产妇作为研究对象,采用随机数表法分为观察组与对照组,各33例.对照组予以常规分娩方案,观察组实施拉玛泽减痛分娩法联合无创接生方案,比较两组产后临床指标、疼痛评分及并发症发生情况.结果 与对照组相比,观察组产妇下床活动时间、住院时间短,疼痛评分低,差异均有统计学意义(均P＜ 0.05);对照组产妇会阴裂伤发生率为54.54％,明显高于观察组的30.30％,差异有统计学意义(P＜0.05);对照组产妇产后出血、会阴感染及尿潴留等并发症的发生率均显著高于观察组,差异均有统计学意义(均P＜ 0.05).结论 拉玛泽减痛分娩法联合无创接生方案应用于自然分娩中可减轻产妇疼痛及创伤,减少产后并发症的发生情况,能有效缩短住院时间,使产妇获得较好的分娩体验,值得临床广泛推广应用.     

Co-existence of P2Y-and PPADS-insensitive P2U-purinoceptors in endothelial cells from adrenal medulla.

1. We have studied the effects of purinoceptor stimulation on Ca2+ signals in bovine adrenomedullary endothelial cells. [Ca2+]i was determined with the fluorescent probe fura-2 both in population samples and in single, isolated, endothelial cells in primary culture and after subculturing. 2. In endothelial cells, maintained in culture for more than one passage, several purinoceptor agonists elicited clear [Ca2+]i transient peaks that remained in the absence of extracellular Ca2+. Adenosine 5''-triphosphate (ATP) and uridine 5''-triphosphate (UTP) were equipotently active, with EC50 values of 8.5 +/- 0.9 microM and 6.9 +/- 1.5 microM, respectively, whereas 2-methylthioadenosine 5''-triphosphate (2MeSATP), adenosine 5''-(alpha, beta-methylene)triphosphate (alpha, beta-MeATP) and adenosine(5'')tetraphospho(5'')adenosine (Ap4A) were basically inactive. Adenosine 5''-O-(2-thiodiphosphate) (ADP beta S) was a weak agonist. The apparent potency order was UTP = ATP > ADP beta S >> 2MeSATP > alpha, beta-MeATP. 3. Cross-desensitization experiments revealed that UTP or ATP, added sequentially at concentrations of maximal effect, could completely abolish the [Ca2+]i response to the second agonist. ADP beta S exerted only a partial desensitization of the response to maximal ATP, in accordance with its lower potency in raising [Ca2+]i. 4. The effect on [Ca2+]i of 100 microM ATP in subcultured cells was reduced by only 25% with 100 microM suramin pretreatment and was negligibly affected by exposure to 10 microM pyridoxalphosphate-6-azophenyl-2'', 4''-disulphonic acid (PPADS). The concentration-effect curve for ATP was not significantly affected by PPADS, but was displaced to the right by a factor of 6.5 by 100 microM suramin. 5. In primary cultures, clear [Ca2+]i responses were elicited by 2MeSATP. Suramin totally and selectively blocked 2MeSATP responses, whereas UTP-evoked [Ca2+]i transients were mainly unaffected by suramin or PPADS. Over 80% of cells tested showed responses to both 2MeSATP and UTP. The [Ca2+]i response to UTP was not desensitized in the presence of 2MeSATP. 6. ATP and UTP stimulated the release of preloaded [3H]-arachidonic acid ([3H]-AA), both in the presence and in the absence of extracellular Ca2+, by approximately 135% with respect to basal levels. Suramin and PPADS enhanced, rather than inhibited, the [3H]-AA releasing effect of ATP by 2.5 times. Suramin also potentiated the effect of the calcium ionophore A23187. 7. These results indicate that endothelial cells from adrenomedullary capillaries co-express both P2Y- and P2U-purinoceptors. P2Y-purinoceptors are lost in culture with the first passage of the cells. The P2U-purinoceptor subtype present in these cells is insensitive to PPADS and thus similar to that found in aortic endothelial cells.     

P2X and P2Y Receptors Mediate Contraction Induced by Electrical Field Stimulation in Feline Esophageal Smooth Muscle

It is well-known that electrical field stimulation (EFS)-induced contraction is mediated by a cholinergic mechanism and other neurotransmitters. NO, ATP, calcitonin gene-related peptide (CGRP), and substance P are released by EFS. To investigate the purinergic mechanism involved in the EFS-induced contraction, purinegic receptors antagonists were used. Suramine, a non-selective P2 receptor antagonist, reduced the contraction induced by EFS. NF023 (10^-7~10^-4 M), a selective P2X antagonist, inhibited the contraction evoked by EFS. Reactive blue (10^-6~10^-4 M), selective P2Y antagonist, also blocked the contraction in a dose-dependent manner. In addition, P2X agonist α,β-methylene 5''-adenosine triphosphate (αβMeATP, 10^-7~10^-5 M) potentiated EFS-induced contraction in a dose-dependent manner. P2Y agonist adenosine 5''-[β-thio]diphosphate trilithium salt (ADPβS, 10^-7~10^-5 M) also potentiated EFS-induced contractions in a dose-dependent manner. Ecto-ATPase activator apyrase (5 and 10 U/ml) reduced EFS-induced contractions. Inversely, 6-N,N-diethyl-D-β,γ-dibromomethylene 5''-triphosphate triammonium (ARL 67156, 10^-4 M) increased EFS-induced contraction. These data suggest that endogenous ATP plays a role in EFS-induced contractions which are mediated through both P2X-receptors and P2Y-receptors stimulation in cat esophageal smooth muscle.     

P2X4 Receptor Regulates Alcohol-Induced Responses in Microglia

Mounting evidence indicates that alcohol-induced neuropathology may result from multicellular responses in which microglia cells play a prominent role. Purinergic receptor signaling plays a key role in regulating microglial function and, more importantly, mediates alcohol-induced effects. Our findings demonstrate that alcohol increases expression of P2X4 receptor (P2X4R), which alters the function of microglia, including calcium mobilization, migration and phagocytosis. Our results show a significant up-regulation of P2X4 gene expression as analyzed by real-time qPCR (***p?p?CX3CL1) by 75 % following 48 h of treatment compared to control (***p?CX3CL1-dependent migration was confirmed to be P2X4 receptor-dependent using the antagonist 5-BDBD, which reversed the effects as compared to alcohol alone (***p?p?p?相似文献   

Evaluation of outcomes of intravenous to oral antimicrobial conversion initiatives: a literature review

Inappropriate use of antimicrobial agents could result in antimicrobial resistance that could impact clinical cure outcomes (by increasing morbidity in terms of increased adverse events and risk of secondary and hospital-acquired infections and mortality) and increase costs to health care institutions. Thus, appropriate antimicrobial use has become vital for balancing patient safety and costs and is therefore a focus for health care institutions. This is often achieved through efforts of antimicrobial stewardship programs that include intravenous to oral conversion initiatives with clinical pharmacists playing an instrumental role in their development and implementation with medical staff approval. However, the delivery and effectiveness of these programs are quite variable. Therefore, for guiding the successful delivery and evaluations of these programs in the future, the objective of this literature review is to document the impact of intravenous to oral conversion programs in terms of clinical and economic outcomes at various institutions worldwide along with the pharmacist's role in these programs.     

Recent progress in drug delivery of pluronic P123: pharmaceutical perspectives

This review focuses on recent investigations that used Pluronic P123 (P123) as pharmaceutical ingredients in vesicle, micelle, mixed micelle, in situ gel, tablet and emulsion. The main results from these studies show that P123 can significantly increase the stability of incorporated hydrophobic drugs with enhanced in vitro cytotoxicity and cellular uptake of anticancer drugs. Moreover, modified forms of P123 with RGD, folate or other targeted marker have shown its therapeutic potentials in various types of tumors and cancers. Furthermore, modified forms of P123 alone and/or mixed with other copolymers have less toxic effects and more tumor-specific delivery of anticancer drugs. They are promising materials as a nanoplatform for the drug delivery. Finally, the future perspectives of the field are briefly discussed.     

Cytochrome P450 gene-directed enzyme prodrug therapy (GDEPT) for cancer

Several commonly used cancer chemotherapeutic prodrugs, including cyclophosphamide and ifosfamide, are metabolized in the liver by a cytochrome P450 (CYP)-catalyzed prodrug activation reaction that is required for therapeutic activity. Preclinical studies have shown that the chemosensitivity of tumors to these prodrugs can be dramatically increased by P450 gene transfer, which confers the capability to activate the prodrug directly within the target tissue. This P450 gene-directed enzyme prodrug therapy (P450 GDEPT) greatly enhances the therapeutic effect of P450-activated anti-cancer prodrugs without increasing host toxicity associated with systemic distribution of active drug metabolites formed by the liver. The efficacy of P450 GDEPT can be enhanced by further increasing the partition ratio for tumor:liver prodrug activation in favor of increased intratumoral metabolism. This can be achieved by co-expression of P450 with the flavoenzyme NADPH-P450 reductase, which increases P450 metabolic activity, by localized prodrug delivery, or by the selective pharmacologic inhibition of liver prodrug activation. P450 GDEPT prodrug substrates are diverse in their structure, mechanism of action, and optimal prodrug-activating P450 gene; they include both established and investigational anticancer prodrugs, as well as bioreductive drugs that can be activated by P450/P450 reductase in a hypoxic tumor environment. Several strategies may be employed to achieve the tumor-selective gene delivery that is required for the success of P450 GDEPT; these include the use of tumor-targeted cellular vectors and tumor-selective oncolytic viruses. Overall, P450-based GDEPT presents several important, practical advantages over other GDEPT strategies that should facilitate the incorporation of P450 GDEPT into existing cancer treatment regimens. A recent report of clinical efficacy in a P450-based phase I/II gene therapy trial for pancreatic cancer patients supports this conclusion.     

Antioxidant activity and in vitro inhibition of tumor cell growth by leaf extracts from the carob tree (Ceratonia siliqua)

The methanol leaf extracts of female cultivars of the carob tree [Ceratonia siliqua L. (Fabaceae)] and of hermaphrodite and male trees were investigated for their contents of phenolic compounds, their in vitro antioxidant activity, measured by 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical-scavenging and linoleic acid system assays, and their in vitro tumor growth inhibition on HeLa cells. The different cultivars and trees showed high levels of phenols, and considerable variations in the amount of these compounds. The extracts showed significant radical scavenging activity (RSA), which was not significantly affected by the gender of the tree. From the female cultivars tested, Galhosa exhibited the highest RSA. Gender significantly affected the antioxidant activity of the extracts measured by the linoleic acid system assay, and males and hermaphrodites showed the highest activities. The extracts displayed a remarkable ability to inhibit tumor cell proliferation, and their bioactivity varied with different cultivars or trees tested. Extracts from male and hermaphrodite trees exhibited higher capacity to inhibit the proliferation of HeLa cells than the female cultivars.     

基于Fibre Chanel组播的远程数据备份体系结构

数据备份是容灾的基础.本文提出了一种基于FC组播服务的远程数据备份方法,对其工作原理和所涉及到的粗波分复用和流量控制等关键技术进行了研究,对基于FC组播的数据备份系统的性能和所属的容灾层次等内容进行了分析.