Assembly of chick brain tubulin onto isolated basal bodies of Chlamydomonas reinhardi

Basal bodies isolated from Chlamydomonas reinhardi will serve as initiation centers for the assembly of chick brain microtubule protein subunits (tubulin) into microtubules. The rate of microtubule assembly is tubulin-concentration dependent; this assembly occurs onto both distal and proximal ends of the basal body mnicrotubules, with distal assembly greatly favored. In vitro assembly of brain tubulin also occurs onto the mid-lateral aspects of the basal bodies, presumably onto the fiber connecting the two basal bodies.     

Synthesis of reverse osmosis membranes by plasma polymerization of allylamine

The polymerization of allylamine in a radio-frequency electrodeless plasma to form thin polymer films on microporous filter media provides very effective dry composite membranes for reverse osmosis. Salt and urea rejections as high as 98 percent and 46 percent, respectively, have been achieved from a solution containing 10 grams of sodium chloride per liter and 10 grams of urea per liter. The plasma conditions and polymerization technique are discussed.     

Terminal saccharides on sperm plasma membranes: identification by specific agglutinins

Six specific agglutinins were used to identify the terminal sugar residues in the surface oligosaccharides of rabbit and hamster spermatozoa by specific agglutination. Species differences in epididymal sperm were found in the terminal residues, resembling alpha-D-mannose, D-galactose, N-acetyl-D-glucosamine, and N-acetyl-D-galactosamine. Species similarities were found in terminal residues, resembling L-fucose and N-acetylneuraminic acid. When ejaculated rabbit sperm were compared to epididyimal sperm, the latter were more agglutinable with a specific agglutinin recognizing N-acetyl-D-glucosamine.     

Tissue factor (thromboplastin): localization to plasma membranes by peroxidase-conjugated antibodies

Peroxidase-conjugated antibodies were used to determine the histologic and cytologic localization of bovine and human tissue factor (thromboplastin). Tissue factor antigen was found in highest concentration in the intima of blood vessels, particularly in the plasma membranes of endothelial cells and in human atheromatous plaques. Tissue factor was also found limited to the plasma membranes of many cell types. The presence of tissue factor in the plasma membranes of endothelial cells and atheromata suggests that it may play a significant role in hemostasis and thrombosis.     

Modified superheating of purified water

Purified water, intensively redistilled and allowed to overflow so as to shed residual adsorbate from the container, acquires a limiting thermal sensitivity to additions of long-chain fatty acids and alcohols. Thus two to three molecules of cis-13-docosenoic acid supplied for each 1000 molecules of exposed surface of water held quietly at the normal boiling point increases the superheat, Deltatg, by 10 percent.     

Fossil Canis from the tar pits of La Brea,Peru

New fossil material has been obtained from La Brea, Peru. Included in this material are remains of a large wolflike canid which could not be referred to any living or fossil South American canine genus. Comparison with fossil canids from Rancho La Brea, Calif., shows that it closely resembles Canis (Aenocyon) dirus Leidy.     

工程结构蚀坑的腐蚀疲劳裂纹起始寿命预测

为了研究腐蚀疲劳裂纹在蚀坑处萌生位置差异的本质及预测腐蚀疲劳裂纹起始寿命,采用双参数模型描述点蚀坑形貌,并基于三维有限元模型分析不同点蚀坑形貌下的应力集中情况。基于此,分析了蚀坑深度、深径比及位置等参数对蚀坑不同位置应力集中的影响规律。依据腐蚀疲劳现象学观点,建立了三维双参数点蚀坑腐蚀疲劳裂纹萌生评估模型,分析不同蚀坑形貌下腐蚀疲劳裂纹萌生的临界值。研究表明:控制腐蚀疲劳裂纹萌生的条件主要为蚀坑深度和蚀坑形状;萌生于蚀坑处不同位置的腐蚀疲劳裂纹的临界值均可采用蚀坑临界深度值表示。所建模型的有效性和合理性得到了有效验证,为工程实际中遭受腐蚀疲劳损伤结构的腐蚀疲劳起始寿命预测提供了一种可行性方法。     

Infrared receptors in the facial pits of the Australian python Morelia spilotes

There is a series of pits in the scales of the rostrum and posterior portion of the lower lips in some pythons and boas. In the Australian python Morelia spilotes, these pits are innervated by the maxillary and mandibular branches of the trigeminal nerve. Structural and neurophysiological evidence indicate that in the pits there are receptors that function as detectors of radiant heat flux.     

温室金银花穴盘扦插育苗技术试验

1试验概况1.1试验地点和规模试验在陕西省商洛市农科所连栋温室内进行。温室面积1500m2,配备有内遮阳系统、通风降温系统(风机与湿帘)、微喷系统。1.2试验品种及来源品种为金银花京丰一号,引进山东省优良品种。     

Atomic force microscopy of atomic-scale ledges and etch pits formed during dissolution of quartz

The processes involved in the dissolution and growth of crystals are closely related. Atomic force microscopy (AFM) of faceted pits (called negative crystals) formed during quartz dissolution reveals subtle details of these underlying physical mechanisms for silicates. In imaging these surfaces, the AFM detected ledges <1 nanometer (nm) high that were spaced 10 to 90 nm apart. A dislocation pit, invisible to optical and scanning electron microscopy measurements and serving as a ledge source, was also imaged. These observations confirm the applicability of ledge-motion models to dissolution and growth of silicates; coupled with measurements of dissolution rate on facets, these methods provide a powerful tool for probing mineral surface kinetics.     

贝壳粉对Cd(Ⅱ)的吸附性能研究

为了研究贝壳粉对Cd~(2+)的吸附性能及最佳吸附条件,采用静态吸附实验研究了Cd~(2+)初始浓度、吸附剂用量、温度、pH、吸附时间以及离子强度对贝壳粉吸附Cd~(2+)性能的影响。结果表明:在不同Cd~(2+)初始浓度下,随着吸附剂用量的增加,贝壳粉对Cd~(2+)的吸附量呈现出先强烈吸附后逐渐缓和的趋势,符合准一级动力学模型和准二级动力学方程。Temkin和Langmuir模型均能较好地描述贝壳粉对Cd~(2+)的等温吸附过程,约30 min达到平衡,为自发的吸热反应,最大饱和吸附量为161.75 mg·g~(-1)。随着溶液pH值增加,贝壳粉对Cd~(2+)的吸附性能也随之增大,当pH≥5时趋于稳定。随着Ca~(2+)和Mg~(2+)浓度增大,贝壳粉对Cd~(2+)的吸附性能逐渐减弱,最大降幅分别达到15.19%和14.44%。     

畜禽粪对抗生素的吸持作用

抗生素是畜禽养殖业中常用的一类兽药,经饲料添加用量大,体内代谢率低,主要通过粪便排出体外。当畜禽粪便在养殖场周边堆放或施入农田后,会对生态环境造成一定的污染危害,而这种影响与畜禽粪对其的吸附强弱密切有关。研究了猪粪和鸡粪对土霉素、泰乐菌素、磺胺二甲嘧啶和恩诺沙星等4种常用抗生素的吸附能力。结果表明,畜禽粪对抗生素的吸附强度因抗生素种类的不同可有很大的变化,吸附强度大小为：土霉素>恩诺沙星>泰乐菌素>磺胺二甲嘧啶;鸡粪对抗生素的吸附强度略高于猪粪;从畜禽粪中分离的胶体物质对抗生素的吸附高于相应的畜禽粪。由此可以推断,当畜禽粪便在养殖场周边堆放或施入农田时,磺胺二甲嘧啶与畜禽粪结合较弱,以可溶态形式流失的风险较大,而土霉素、恩诺沙星和泰乐菌素以可溶态的流失风险较小,但它们也可呈胶体结合态随地表径流流失。     

芦苇生物质炭对镉的吸附及机制

为解决重金属废水处理问题,寻求芦苇的新型资源化利用途径,采用限氧热解方法在不同温度下制备芦苇生物质炭（RBC）。在对芦苇生物质炭进行元素分析的基础上,进行吸附动力学实验和等温吸附实验,并通过扫描电镜（SEM）、傅立叶变换红外光谱（FTIR）和X射线衍射（XRD）等表征方法,探究不同热解温度对RBC吸附Cd²⁺的影响及吸附机制。结果表明： RBC对Cd²⁺的吸附过程更符合准二级吸附动力学方程,Langmuir等温吸附模型能更好描述RBC对Cd²⁺的吸附;500℃下制备得到的RBC产率较高,Cd²⁺吸附量最大,理论吸附量可达39.05 mg·g^-1;吸附Cd²⁺后,RBC表面生成粒状结构,XRD谱图出现CdCO₃和CdSiO₃晶型的峰,推断Cd²⁺分别能与CO₃^2-与SiO₃^2-形成沉淀。研究表明,芦苇生物质炭的最优热解温度为500℃,此温度下产率最高,对Cd²⁺的吸附能力最强,吸附Cd²⁺的机制可能为阳离子交换、沉淀吸附、络合和Cd²⁺-π金属键合共同作用。     

虚拟装配在收获机上的应用

虚拟装配是虚拟制造的重要组成部分,利用虚拟装配,可以验证装配设计和操作的正确与否,以便及早地发现装配中的问题,对模型进行修改;并通过可视化显示装配过程,进行装配工艺规划、现场布局、装配操作模拟等。     

Radiocarbon dating of petroleum-impregnated bone from tar pits at Rancho La Brea, California

A liquid-chromatography method has been developed for the separation of amino acids with the same specific activity in radiocarbon from bones impregnated with isotopically dead petroleum compounds found in the La Brea tar pits. This technique permits the application of radiocarbon dating to such bone assemblages.     

Structure of biological membranes

The combined x-ray diffraction and electron microscopic examination of myelin has provided reasonable, but not conclusive, support for its structure as a basically bimolecular leaflet of phospholipid that is partially interspersed with protein. But there is very little basis for extending this concept to biological membranes in general. There is no adequate experimental support for the specific orientation of phospholipids as proposed in the unit membrane theory or for the proposed polar nature of protein-lipid bonds, even in myelin. Membranes differ widely in chemical composition, metabolism, function, enzymatic composition, and even in their electron microscopic image. The only similarity is their general resemblance in electron micrographs, but, until more is known about the chemistry of electron microscopy, this evidence cannot be interpreted with confidence. One positive conclusion to which I have come is that much more chemical evidence must, and can, be obtained. Techniques for the isolation of membranes are improving and protein and lipid chemistry are now highly refined arts. Quantitative analysis of many different membranes is possible and the data can be related in some instances, notably bacterial plasma membranes, to calculations of surface area. Chemical and physical changes induced in membranes of widely different lipid composition by the preparatory procedures of electron microscopy can be determined directly and correlated with the electron microscopic image. Model systems can be assembled whose compositions closely resemble those of biological membranes. Membranes can be disassociated into subunits whose properties can be studied. In particular, x-ray diffraction analysis and electron microscopy by negative staining of reaggregates of lipoproteins isolated from membranes would be very informative. Perhaps most important, the problem of membrane structure must be considered in relation to the problems of membrane function and membrane biosynthesis.