P2P网络安全综述

围绕节点信任问题、节点通信安全问题和版权问题,分析其研究现状并总结了一些解决策略,如建立信任模型、安全通信模型以及基于数字版权保护技术的系统和软件,展望了P2P网络安全未来的研究方向。     

浅析P2P技术在校园网中的应用

P2P技术是一种新型的网络模型,分析了P2P技术的概念和工作原理,阐述了P2P技术在校园网中的应用及存在的问题和解决办法。     

P2P在教育资源建设中的应用研究

P2P技术是目前新一代网络研究的活跃领域,它引导网络计算机从集中式向分布式偏移,网络应用的核心从中央服务器向网络边缘的终端设备扩散,将P2P引入到网络教育资源建设领域,尝试解决资源共享、资源建设、信息服务的智能化等其发展中遇到的问题。     

一种基于P2P的Botnet防御模型

僵尸网络已经成为当前网络中的主要安全威胁,特别是随着对等网络技术的发展,僵尸网络在技术上充分采用结构化对等网络的组网技术,使得僵尸网络的鲁棒性大大提高,给人们带来的安全威胁也前所未有。为了更好地降低基于P2P的僵尸网络所带来的安全威胁,研究提出了一种基于P2P的Botnet防御模型PBDM,PBDM模型有四个部分构成,分别是检测、分析、入侵、反制。最后通过实验表明,PBDM模型具有很高的防御成功率。     

基于多元回归估算残留P

The remaining phosphorus （Prem）, P concentration that remains in solution after shaking soil with 0.01 mol L-1 CaCl2 containing 60μg mL-1 P, is a very useful index for studies related to the chemistry of variable charge soils. Although the Prem determination is a simple procedure, the possibility of estimating accurate values of this index from easily and/or routinely determined soil properties can be very useful for practical purposes. The present research evaluated the Prem estimation through multiple regression analysis in which routinely determined soil chemical data, soil clay content and soil pH measured in 1 mol L-1 NaF （pHNaF） figured as Prem predictor variables. The Prem can be estimated with acceptable accuracy using the above-mentioned approach, and pHNaF not only substitutes for clay content as a predictor variable but also confers more accuracy to the Prem estimates.     

Growth and rhizosphere P pools of legume–wheat rotations at low P supply

Legume pre-crops may increase P uptake of the following wheat, but the mechanisms behind this effect are unclear. A rotation study was carried out to assess the concentrations of rhizosphere P pools of three grain legumes and wheat (phase 1) and their effects on P uptake and P pools in the rhizosphere of the following wheat (phase 2). Faba bean, chickpea, white lupin and wheat were grown for 10 weeks in a loamy sand soil with low P availability. The following wheat was grown in the pre-crop soil with and without addition of pre-crop residues. Among the pre-crops, white lupin had the strongest effect on the P pools; it depleted the labile P pools, resin P and NaHCO₃-Pi and also the less labile P pools, NaOH-Pi and residual P; whereas the concentration of NaHCO₃-Po was higher than that in the rhizosphere of the other pre-crops. White lupin had a smaller biomass compared to faba bean which depleted the P pools to a lesser extent. Phosphorus uptake of the following wheat was greatest in white lupin pre-crop soil. Chickpea increased P uptake of the following wheat when residues were added. In the presence of residues, wheat after legumes depleted labile P pools to a greater extent than wheat after wheat, but this coincided with greater P uptake only in wheat after chickpea and white lupin, which may be explained by the small root biomass of wheat after faba bean. The results show that the greater P uptake of the following wheat induced by pre-crops may be due to two mechanisms: P mobilisation (white lupin) or P addition with legume residues (chickpea). This study further showed that P uptake by a crop is only partly a function of the depletion of P in the rhizosphere; another important factor is the ability to exploit a large soil volume.     

COPPER EFFECTS ON PRUNUS PERSICA IN TWO DIFFERENT GRAFTING COMBINATIONS (P. PERSICA × P. AMYGDALUS AND P. CERASIFERA)

Growth, chlorophyll content, biomass dry weight (DW), nutrient uptake and copper (Cu) accumulation were evaluated in BigTop® peach (Prunus persica L. Batsch) grafted onto two different rootstocks [GF677 (P. persica × P. amygdalus) and Mr.S2/5 (P. cerasifera)] when grown in the presence of 0.1, 10 or 100 μM copper sulfate (CuSO₄). Although scion shoot length varied significantly in response to Cu concentration only with Mr.S2/5 rootstock (40%reduction at 100 μM Cu compared with control), Cu concentration in the scion grafted on GF677 was higher (18.2 mg kg^?1) compared to that grafted on Mr.S2/5 (10.5 mg kg^?1). In both graft combinations, the Cu concentrations in leaves were not statistically different although values ranged between 4.7 and 8.1 mg kg^?1. The DW of leaves and stems was not statistically different from control plants in both graft combinations. On the contrary, root DW of Mr.S2/5 increased, about 13% at 10 μM Cu and 43% at 100 μM Cu. In contrast, DW of GF677 roots at higher Cu treatment was significant lower than control. Chlorophyll reduction Cu induced was not found, suggesting that the degradation of these pigments is maintained at low levels. The uptake of sodium (Na), zinc (Zn), and iron (Fe) changed during Cu stress. The different behavior observed between GF677 and Mr.S2/5 regarding Cu accumulation proves that these two rootstocks have a different ability in translocation and accumulation of Cu in presence of this heavy metal. The use of GF677 rootstocks, in substrates particularly rich of Cu, insures a better development of scion growth when compared to Mr.S2/5, but determines a higher Cu concentration in the stem, while Mr.S2/5 seems to be able to stabilize the Cu concentrations in the scion.     

Addition of organic and inorganic P sources to soil – Effects on P pools and microorganisms

Phosphorus deficiency is wide-spread due to the poor solubility of soil P and the rapid formation of poorly available P after P addition. Microbes play a key role in soil P dynamics by P uptake, solubilisation and mineralisation. Therefore a better understanding of the relationship between type of P amendment, microbial activity and changes in soil P pools is important for a better management of soil P. A P deficient soil was amended with two composts (low P or high P), two crop residues (low P or high P), and inorganic P (KH₂PO₄) at low and high P, and incubated for 56 days. Composts were added at 20 g kg⁻¹ resulting in a total P addition of 4.1 mg kg⁻¹ soil with the low P compost and 33.2 mg kg⁻¹ soil with the high P compost. The same amount of P was added with the other amendments (residues and inorganic P). All amendments increased cumulative respiration, but microbial biomass and the abundance of bacteria and fungi (assessed by phospholipid fatty acid analysis) increased significantly only in soils with organic amendments, with greater increases with residues. The concentration of the inorganic P pools NaHCO₃-P_i, NaOH-P_i and HCl-P increased significantly within 5 h after amendment, particularly with high P amendments. Over the following 56 days, labile inorganic P was converted mainly into non-labile inorganic P with inorganic P addition whereas labile and non-labile organic P was formed with organic amendments. It is concluded that organic P sources, particularly those with high P concentration can stimulate the formation of organic P forms in soils which may provide a long-term slow release P source for plants and soil organisms.     

生物细胞色素P450的研究进展

简要介绍了生物细胞色素P450分布的多样性、P450的功能、P450在不同领域的研究现状与进展。鉴于P450的研究无论在理论上探索生物的生理代谢、选择进化和 生物与环境的关系方面，或在环境保护、农业生态、生物防治、作物基础工程和医药卫生等应用方面，都有广泛的实践意义，因此，应该受到更大的关注和重视。     

热带地区地下排水措施P因子的确定

1981年~1987年,在美国路易斯安那州的Baton Rong地区,进行了地下排水防蚀试验研究。研究结果表明:地下排水措施可减少土壤侵蚀42%,地下排水作为水土保持措施P=0.60,在常规耕作条件下,青贮作物地的土壤流失率为0.11。试验结果还表明:在该地区的冬季气候凉爽,降雨充沛,地下排水措施可通过降低水位从而有效地减少土壤侵蚀。     

SRBSDV结构蛋白P10和非结构蛋白P9-1抗体的制备及应用

为丰富南方水稻黑条矮缩病毒(Southern rice black-streaked dwarf virus,SRBSDV)的预测预报体系,本研究利用Gateway原核表达系统,将SRBSDV结构蛋白P10和非结构蛋白P9-1进行了大量表达,纯化的表达蛋白分别免疫新西兰大白兔(Oryctolagus cuniculus)获得抗血清,抗血清的间接酶联免疫吸附分析(indirect enzyme-linked immunosorbent assay,in-ELISA)效价分别为1∶6 400和1∶3 200,Western blot检测结果表明,制备的2种抗体均具特异性.利用免疫捕获RT-PCR(immunocapture RT-PCR,IC-RT-PCR)和斑点酶联免疫吸附分析(dot enzyme-linked immunosorbent assay,dot-ELISA)方法比较两种抗体检测水稻(Oryza sativa)和白背飞虱(Sogatella furcifera,WBPH)带毒率的应用效果,结果表现一致,说明SRBSDV结构蛋白P10和非结构蛋白P9-1均可用于病毒的田间检测,为病害的预测预报奠定了基础.     

Can phosphorus (P)-releasing bacteria and earthworm (Eisenia fetida L.) co-enhance soil P mobilization and mycorrhizal P uptake by maize (Zea mays L.)?

Journal of Soils and Sediments - Both earthworm (Eisenia fetida L.) and phosphorus (P)-releasing (PR) bacteria, including organic P-mineralizing (OPM) and inorganic P-solubilizing (IPS), are able...     

Evaluation of Soil Labile Phosphorus Using a Double—Labeling （^32P and ^33P） Technique

Isotopic exchangeability of phosphorus in four Chinese soils with and without P application was studied by ^32P and ^33P double-labeling technique in relation to routine chemical extractions.The results showed that Bray-I and Bray-Ⅱ reagents could extract most of the fast exchangeable P.Not all of the Olsen-P belonged to fast exchangeable P,but it was about the same quantity of fast exchangeable P in a calcareous soil and a neutral soil without P application.Sequential fractionation of the soil phosphorus showed that most of the added radioisotopes in high P fixation red soils were tightly held by iron and aluminium oxides,which could be totally extracted only by 0.1M NaOH solution.In the neutral and calcareous soils most of the radioisotopes added were loosely held on the surface of soil particles and could be extracted by anion exchange resin.Phosphate application increased the resin-P fraction significantly for all the soils studied.     

水体苯胺、N和P生物修复研究

利用水培试验研究了6种常见适于水栽植物和EM菌在处理含苯胺、N、P废水的效果。结果表明对水体苯胺修复效率为50.7%～97.3%。植物对苯胺、N、P的修复能力因植物不同而异。植物修复苯胺的能力排序为蕹菜〉水葫芦〉水浮莲〉美人蕉〉水花生〉香蒲,而植物修复N的能力排序为水花生〉水葫芦〉蕹菜〉香蒲〉美人蕉〉水浮莲。美人蕉和蕹菜对P修复能力高于其他植物。抗生素抑菌试验表明,水体中原有微生物在苯胺修复中起了显著作用。EM菌的加入增加对水体N的去除能力。EM菌对水体P修复无直接作用,EM菌促进水浮莲和水葫芦吸收P。     

不同肥力黄绵土在施肥条件下的土壤供N,P能力和N,P肥的效应

经过６年长期施用不同肥料定位试验，使其同一土壤形成肥力上的差异，在此土壤上，进行盆栽试验，分析和研究了不同基础肥力土壤供肥能力，以及施用Ｎ、Ｐ肥的增产效应和作物吸Ｎ、Ｐ量的反映。结果表明，基础肥力以施ＭＮＰ肥土壤供Ｎ、Ｐ能力最强，其次为施ＭＰ肥处理，单施Ｎ肥土壤供Ｎ、Ｐ能力最差。     

Einfluss Langjährig unterschiedlicher Düngung auf P‐Entzug und P‐Gehalte in einer Tieflehm‐Fahlerde

In einem Dauerfeldversuch auf Tieflehm‐Fahlerde in Groß Kreutz, bei Potsdam, wurde der Einfluß differenzierter organischer und mineralischer Düngung auf P‐Entzug und ‐Ausnutzung sowie auf die Veränderungen der P‐Gehalte im Boden untersucht.

Die P‐Ausnutzung (Differenzmethode) nimmt mit steigender P‐Zufuhr ab. Sie liegt bei der geringsten P‐Zufuhr [xbar] bei 36%, bei der höchsten P‐Anwendung bei 12%. Zwischen der Höhe der P‐Zufuhr und dem Gehalt des Bodens an laktatlöslichem P konnten keine Beziehungen nachgewiesen werden. Schärfere Extraktions‐verfahren (kalte 1,5nHCl, heiße 1,5nHCl, 2nH₂SO₄ und Glühen des Bodens mit anschließender Extraktion mit 2nH₂SO₄) spiegeln die Beziehungen zur P‐Zufuhr besser wider. Unabhängig von Art und Höhe der P‐Düngung liegt das Verhältins P_min: P_org bei 4:1.     

NDV-F基因稳定表达P815细胞株的建立

在成功地构建NDV-F基因真核表达载体pCDNA3-NDV-F的基础上,应用脂质体LipofectamineTM2000介导使其转染小鼠肥大细胞瘤细胞株（P815）,以G418加压筛选（600μg/ ml）得到稳定的克隆并扩大培养成系。应用Trizol法提取细胞RNA,经RT-PCR鉴定,转染细胞在1600bp处出现目的条带。收集转染细胞,经Western blot和免疫荧光法检测到目的蛋白的表达。进一步将获得的细胞株在液氮中冻存6个月以检测其稳定性,实验证明该细胞株仍能很好的表达F基因。本实验采用脂质体法已成功建立了能够稳定表达NDV-F基因细胞株,为进一步研究ND核酸疫苗的效果奠定良好的实验基础。     

N、P输出与土地利用类型相关性研究

在于桥水库流域内,进行人工降雨,产流,Ｎ,Ｐ负荷输出实验研究。结果表明,土地利用类型深刻地影响着Ｎ,Ｐ输出特征,Ｎ,Ｐ输出量耕地最多,林地最少,荒坡菖 中等。不同程度的水土流失地域Ｎ,Ｐ输出有明显差异,各种形态的Ｎ,Ｐ输出之间存在着正相关性。