A component of innate immunity prevents bacterial biofilm development

Antimicrobial factors form one arm of the innate immune system, which protects mucosal surfaces from bacterial infection. These factors can rapidly kill bacteria deposited on mucosal surfaces and prevent acute invasive infections. In many chronic infections, however, bacteria live in biofilms, which are distinct, matrix-encased communities specialized for surface persistence. The transition from a free-living, independent existence to a biofilm lifestyle can be devastating, because biofilms notoriously resist killing by host defence mechanisms and antibiotics. We hypothesized that the innate immune system possesses specific activity to protect against biofilm infections. Here we show that lactoferrin, a ubiquitous and abundant constituent of human external secretions, blocks biofilm development by the opportunistic pathogen Pseudomonas aeruginosa. This occurs at lactoferrin concentrations below those that kill or prevent growth. By chelating iron, lactoferrin stimulates twitching, a specialized form of surface motility, causing the bacteria to wander across the surface instead of forming cell clusters and biofilms. These findings reveal a specific anti-biofilm defence mechanism acting at a critical juncture in biofilm development, the time bacteria stop roaming as individuals and aggregate into durable communities.     

利用线性元件制作圆光栅的原理及方法

运用菲涅耳双棱镜法在单色光中获取干涉条纹的原理,设计圆锥线性元件,并利用线性元件制作圆光栅,给出了光强分布情况和制作条件与步骤．该方法制作效率高,成本低,制作方法便捷,杂散光低、刻划面积大、槽密度高、消像差并在较宽光谱范围内衍射效率变化平稳．     

Structure and mechanism of the S component of a bacterial ECF transporter

The energy-coupling factor (ECF) transporters, responsible for vitamin uptake in prokaryotes, are a unique family of membrane transporters. Each ECF transporter contains a membrane-embedded, substrate-binding protein (known as the S component), an energy-coupling module that comprises two ATP-binding proteins (known as the A and A' components) and a transmembrane protein (known as the T component). The structure and transport mechanism of the ECF family remain unknown. Here we report the crystal structure of RibU, the S component of the ECF-type riboflavin transporter from Staphylococcus aureus at 3.6-? resolution. RibU contains six transmembrane segments, adopts a previously unreported transporter fold and contains a riboflavin molecule bound to the L1 loop and the periplasmic portion of transmembrane segments 4-6. Structural analysis reveals the essential ligand-binding residues, identifies the putative transport path and, with sequence alignment, uncovers conserved structural features and suggests potential mechanisms of action among the ECF transporters.     

褪黑素单克隆抗体的制备及鉴定

为了获得抗褪黑素(MT)高效价的单克隆抗体,用甲醛将MT连结到BSA上,然后用连结物背部皮下多点免疫Balb／c小鼠,用PEG诱导免疫鼠脾细胞与Sp2／0细胞融合,经ELISA法筛选阳性克隆株及测定效价,用抗体与同类物之间的交叉反应进行特异性鉴定．最后获得5株(4C9D7、3E12C7H11E7、3E12A9D7、6A6A3A2C3、1E1E2H2H6)能稳定分泌高效价抗MT的单克隆抗体(McAb)的杂交瘤细胞。     

基于粒子群优化核独立分量的特征降维算法及其应用研究

大型复杂装备的工作过程均表现出较强的非线性,并且受非高斯噪声和各种不确定因素的影响,导致状态监测信息多是高维的非线性、非高斯数据,且计算量随信息维数呈指数增长,若直接用于预测模型则导致计算量异常庞大,不利于完成模型参数估计和实现实时维修。针对上述问题,对核独立分量分析算法中关于核函数参数选择的盲目性,提出了用粒子群优化算法改进核参数选择过程的核独立分量分析算法,实现了高维状态信息的降维。最后,通过对某自行火炮发动机油液监测数据进行特征降维实例分析,验证了所提方法的可行性与有效性。     

高校工科生产实习面临的困境及解决的途径

生产实习是工科大学实践教学过程中一个重要环节,是提高理论与实践综合能力的必经之路。由于学校的扩招及市场经济的转变,生产实习面临很多困难。本文针对目前生产实习存在的问题,基于培养具有实践和应用能力的人才,探索了解决生产实习困境的方法和模式。     

Recognition and plasma clearance of endotoxin by scavenger receptors.

Lipid A is the active moiety of lipopolysaccharide (LPS, also referred to as endotoxin), a surface component of Gram-negative bacteria that stimulates macrophage activation and causes endotoxic shock. Macrophages can bind, internalize and partially degrade LPS, lipid A and its bioactive precursor, lipid IVA. We report here that lipid IVA binding and subsequent metabolism to a less active form by macrophage-like RAW 264.7 cells is mediated by the macrophage scavenger receptor. Scavenger-receptor ligands inhibit lipid IVA binding to, and metabolism by, RAW cells, and lipid IVA binds to type I and type II bovine scavenger receptors on transfected Chinese hamster ovary cells. Although in vitro competition studies with RAW cells indicate that scavenger receptor binding is not involved in LPS or lipid IVA-induced stimulation of macrophages, in vivo studies show that scavenger-receptor ligands greatly inhibit hepatic uptake of lipid IVA in mice. Thus, scavenger receptors expressed on macrophages may have an important role in the clearance and detoxification of endotoxin in animals.     

信息系统组态平台及其构件复用技术

在讨论软件构件技术的基础上,借鉴工业控制自动化领域的组态思想,提出了支持构件复用的信息系统组态平台及其组态开发模式．它面向需求动态变化的最终用户,以组态方式通过可复用构件的动态组合实现应用系统,从而提高应用软件系统的开发速度和效率及其可维护性、可重构性和可扩展性．     

一株堆肥高效解磷菌的筛选、鉴定及其溶磷特性

磷是植物必需的营养元素之一,但大多数耕地土壤中磷素易与Ca²⁺、Fe³⁺、Fe²⁺、Al³⁺等结合成无效态磷,植物难以直接吸收利用。解磷微生物可活化难溶性磷,将其接种于堆肥,有助于提高堆肥产品磷素植物可利用程度。从鸡粪好氧堆肥中筛选获得高效解磷细菌,为生物强化富磷堆肥的制备提供菌种。利用NBRIY培养基初筛获得解磷菌,利用蒙金娜(PVK)培养基复筛获得高效解磷菌株,对其进行16S rDNA分子生物学鉴定,并研究不同碳源、氮源、初始pH、难溶性磷种类、难溶性磷添加量、可溶性磷浓度对菌株溶磷能力的影响。初筛获得7株解磷细菌,分别命名为PSB1～PSB7;复筛后,PSB6的溶磷量最大(126.37 mg/L);其余菌株的溶磷量在50.12～109.56 mg/L。PSB6经16S rDNA初步鉴定为Bacillus sp.(MW513386)。PSB6最适碳源为葡萄糖,最适N源为硫酸铵,最适生长初始pH为7.0,不同难溶性磷中,PSB6对磷酸三钙溶解效果最好,溶磷量为126.37 mg/L。当磷酸三钙添加...     

激光法制备高纯纳米SiC粉体及其产率

以硅烷SiH4和乙烯C2H4为反应原料,采用激光诱导化学气相沉积法(LICVD)制备了高纯、低团聚、近球形的理想纳米SiC粉体.用化学分析、X射线衍射(XRD)、透射电子显微镜(TEM)及比表面积(BET)等分析测试手段对粉体进行了表征,结果表明粉体中SiC含量高于98%,平均粒径为20nm,晶体结构为β-SiC,粉体产率大于200g/h,粉体中氧含量低于1%,且主要是表面的吸附氧;从能量和反应气流量两个方面对粉体产率进行了理论分析,在此基础上推导出了粉体产率公式,与实际粉体产率基本一致.     

煤矸石制备PFASS及其在废水处理中应用

针对煤矸石制备无机混凝剂的问题,采用正交实验法得出了在煤矸石制备聚合硅酸硫酸铁铝(PFASS)过程中用酸浸取铝和用碱提取硅的最佳反应条件,即最佳酸浸条件为:酸浸时间(A)为1．5h,NaCl助溶剂与煤矸石的质量比(B)为0．05:1,固液比(C)为1:10;最佳碱浸条件为:碱浸时间为2 h,碱液浓度为5mol／L,固液比为1:10。并采用单因素实验法分别讨论了混凝剂的碱化度、废水pH值、混凝时间、混凝剂投加量等参数对废水处理效果的影响,实验证明:采用本工艺生产的PFASS,水处理效果好,COD的平均去除率为45％左右,脱色率也在85％以上。     

油田注采诱发地表变形规律及控制方法研究

根据大庆油田南二区大地三维形变测量结果,研究地层压力变化引起地面垂向变形的规律,并提出地表垂向变形计算的数学模型,通过有限元法对大地垂向变形情况进行了数值模拟,数值模拟结果和测量结果对比,显示了模拟方法的可靠性.最后基于数值模拟和现场测量,提出了控制油田地表垂向变形的方法.图3,表5,参8.     

免疫防治在鳖养殖中的应用

从病鳖分离得到四株致病菌菌株,经鉴定为嗜水气单胞菌（Ａｅｒｏｍｏｎａｓ ｈｙｄｒｏｐｈｉｌａ）,豚鼠气单胞菌（Ａｅｒｏｍｏｎａｓ ｃａｖｉａｅ）,温和气单胞菌（Ａｅｒｏｍｏｎａｓ ｓｏｂｒｉｏ）．药敏试验结果：氟嗪酸、环丙沙星、新霉素对四菌株有较强抑菌作用。制备四联菌苗对鳖进行免疫接种,可产生较好的防治结果,卵黄抗体治疗病鳖,治愈率为３７．１％。     

Mathematical approach to sedimentary component partitioning of polymodal sediments and its applications

Most continental sediments are composed of overlapped components, whose grain-size follows a type of distribution function. The components and the function type of a sample are determined on frequency and cumulative curves of grain-size distribution so as to designate the function formula. The function parameters can be estimated by fit ting designated function to measured grain-sized data of the sample, which simultaneously achieves numerical partitioning of the components. Genetic analysis of hydraulic and aeolian sediments demonstrates the following environmental impli cations. Fluvial sediment is composed of isolated saltation and suspension component. The sediment in drainage closed lakes is dominated by suspension silt-clay component, with little portion of saltatory sand. Fine sand conponent makes up a majority of desert sand overlapped with small portion of fine dust. Loess is composed of overlapped short-suspending silt component and long-suspension fine component. Long-suspension fine dust is the unique component of deep-sea aeo lian sediment. The fine component shows constant grain-size distribution and genetic connection from desert sand, loess of Northern China to Northern Pacific Ocean, which is transported mainly by westerly stream and dispersed in whole stratosphere to form the background dust.     

微生物植酸酶对土壤有机磷组分含量及有效性的影响

为提高土壤有机磷素的有效性,并为微生物植酸酶应用于农业生产实践提供理论参考,采用室内培养的方法,研究了不同用量微生物植酸酶菌剂在不同培养时期对土壤有机磷组分含量及有效性的影响.结果表明,添加微生物植酸酶菌剂处理后的土壤活性、中等活性有机磷含量均高于对照,而且与植酸酶菌剂使用量显著相关;其含量随培养时间的延长呈增加趋势,培养至第32d后基本保持平稳;而土壤中稳性和高稳性有机磷含量均低于对照,与植酸酶菌剂使用量显著相关;其含量随培养时间的延长呈减少趋势,培养至第32d后基本保持平稳.添加微生物植酸酶各处理的有机磷总量均低于对照,并随微生物植酸酶添加量的增加而减小;而土壤有效磷含量均高于对照.因此微生物植酸酶可以促进土壤稳定性有机磷向活性有机磷转化,乃至向无机磷转化,从而提高了土壤有机磷素的有效性.