一种快速制作变螺距螺旋面三维立体图的方法

本文提出一种与AutoCAD相结合绘制所需变螺距螺旋面三维立体图的方法，利用AutoLISP语言编程，在AutoCAD2000环境下，根据给定的参数可自动生成变螺距螺旋线的三维图。然后导入3DS MAX中再进行编辑，即可获得所需的变螺距螺旋面立体图。此方法对其他螺旋面的制作也有一定的借鉴。     

香港地区螺旋线虫种类记述

描述了采自香港的５种螺旋属线虫：卡文内斯螺旋线虫、双角螺旋线虫、双宫螺旋线虫、外异螺旋线虫和近凹螺旋线虫，它们均为香港地区首次报道。     

纽带科（Hoplolaimidae）两线虫的鉴定

鉴定了两种纽带科线虫：松拟盘旋线虫及双宫螺旋线虫。松拟盘旋线虫为我国新记录种，分离自上海植物园细辛根围。双宫螺旋线虫为上海常见的螺旋线虫之一，根据观察认为双螺旋线虫的形态与具膜螺旋线虫一致，故提出具膜螺旋线虫为双宫螺旋线虫的同物异名。     

变螺距圆柱螺旋面展开图AutoCAD辅助设计程序算法结构

螺旋面在工程上应用非常广泛,例如螺旋输送器、某些叶轮上的叶片、变螺距的螺旋开沟器等都使用不同类型的螺旋面。变螺距圆柱正螺旋面是一种直纹螺旋曲面,是不可展的,传统方法只能进行近似展开。通过计算机辅助设计实现螺旋面展开图精确自动绘制是非常必要的,本文利用变螺距螺旋线的参数方程推导了变螺距圆柱正螺旋面展开图的AutoCAD辅助设计程序算法结构,通过该算法可在AutoCAD中轻松实现的计算机编程。     

浙江出口盆景上三种螺旋线虫(线虫纲:纽带科)记述(英文)

对采自浙江出口盆景根围的螺旋线虫群体经形态学测量,鉴定出三个种,分别为双宫螺旋线虫（Ｈ．ｄｉｈｙｓｔｅｒａ）,双角螺旋线虫（Ｈ．ｄｉｇｏｎｉｃｕｓ）和可变螺旋线虫（Ｈ．ｖａｒｉａｂｉｌｉｓ）．三种线虫均系浙江省植物寄生线虫的新纪录,其中双角螺旋线虫和可变螺旋线虫系首次在中国盆景上报道．     

香蕉上的螺旋线虫和纽带线虫种类鉴定

从福建省漳州市、福州市、莆田市、南平市、宁德市香蕉园采集的62份香蕉根样本中分离到螺旋线虫和纽带线虫.根据其形态学特征及r DNA-ITS区和28S r DNA-D2/D3区序列分析,将其鉴定为双宫螺旋线虫、多带螺旋线虫和塞氏纽带线虫.多带螺旋线虫和塞氏纽带线虫在福建香蕉上为首次报道.     

淡水田螺缝合线拟合

根据淡水田螺的生物特性,首次研究田螺壳螺旋形几何形状(缝合线)特征及其分布规律。首先,对田螺壳表面螺旋部和缝合螺旋线等形状特征进行逆向扫描和特征统计;其次,通过Origin软件并结合微元法思想拟合出二维螺旋线的数学表达式;在此基础上建立螺壳三维螺旋线的评价指标集。结果表明,拟合出的2种螺旋线的数学表达式与田螺缝合线相似度极高,从而为农业中螺壳形状描述研究与仿生应用提供依据。     

双角螺旋线虫扫描电镜观察

[目的]采用扫描电镜观察双角螺旋线虫（Helicotylenchus digonicus）。[方法]对采自浙江长兴的双角螺旋线虫进行了扫描电镜观察,对光镜下的形态结构进行了确认。[结果]采用戊二醛-锇酸双固定及临界点干燥制备的线虫样本,虫体不皱缩,不变形,形态结构清晰,能够很好地进行扫描电镜观察。[结论]为研究和防治双角螺旋线虫提供了参考。     

浙江出口盆景上三种螺旋线虫（线虫纲：纽带科）记述

对采自浙江出口盆景根围的螺旋线虫群体经形态学测量,鉴定出三个种,分别为双宫螺旋线虫,双角螺旋线虫和可变螺旋线虫,三种线虫均系浙江省植物寄生线虫的新纪录,其中双角螺旋线虫和可变螺线虫系首次在中国盆景上报道。     

安徽省合肥市大蜀山螺旋属线虫多样性

为探索根际植物线虫多样性研究方法,在安徽省合肥市大蜀山麻栎等4个不同建群种区系内按随机取样法采集根际土样。利用Cobb筛法分离土样,在解剖镜下收集螺旋属线虫后,用de Man法测计形态值,比对分类学文献鉴定螺旋线虫种类。记录4个区系内的螺旋线虫的种类数和发生密度。用变异系数（coefficient of variance, CV）评价螺旋线虫种内形态稳定性,用Brillouin指数等比较4个区系的种类多样性。结果表明,在大蜀山共鉴定发现阿布拿马螺旋线虫（Helicotylenchus abunaamai）等7种螺旋属线虫,其中竹螺旋线虫（Helicotylenchus bambesae）为安徽省新纪录;螺旋线虫的阴门位置为该地区最稳定的种内形态,其V值变异系数范围为0.01～0.03;建群种区系之间的螺旋属线虫多样性存在差异,根据Brillouin方法,三角枫区系的线虫种类多样性指数最高,为2.246。     

几种常绿阔叶树在北方地区抗旱适应性评价

以在北京试种成功的5种常绿阔叶树木为材料,以普通大叶黄杨为对照,测定多项水分生理和光合生理指标,探索以多指标综合评价常绿阔叶树木树种间及树龄间的抗旱差异,并对其抗旱能力进行主成分分析及按抗旱力大小进行排序和分类。结果表明:常春藤京8号2龄树木和荚迷抗旱力最强为第一类,常春藤京8号1龄树木和常春藤京9号2龄树木、京10号2龄树木为第二类,日本北海道大叶黄杨树和普通大叶黄杨为第三类。树种间抗旱性排序为荚迷>常春藤>大叶黄杨。同一树种不同栽培品种间排序为常春藤京8号>常春藤京9号>常春藤京10号。     

小叶常春藤扦插繁殖试验初报

【目的】探讨不同种类外源激素、不同处理浓度、不同处理时间对小叶常春藤扦插生根、成活的效果,为小叶常春藤快速繁殖和大面积推广应用提供参考依据。【方法】以当年生、1年生、2年生健壮无病虫害的日本小叶常春藤为试验材料,采用4因素3水平正交试验,研究外源生长激素吲哚乙酸(IBA)、α-萘乙酸(NAA)和ABT生根粉1号(ABT1)不同浓度、不同处理时间和不同插穗类型对日本小叶常春藤扦插生根效果的影响。【结果】外源生长激素种类、浓度、处理时间及插穗类型对小叶常春藤扦插成活率、生根数、根鲜重和平均根长均有显著影响,其中S7处理(ABT1100 mg/L浸泡1年生小叶常春藤插穗12 h)的成活率最高达95.53%,与其他处理差异显著(P<0.05);对插穗扦插成活率的影响大小顺序是:插穗类型>激素种类>激素浓度>处理时间。【结论】影响小叶常春藤扦插成活率的主要因素是插穗类型,以1年生插穗扦插效果最好;选择ABT1100 mg/L浸泡1年生小叶常春藤插穗12 h最易于其生根和成活。     

Association of transfer RNA acceptor identity with a helical irregularity

The aminoacylation specificity ("acceptor identity") of transfer RNAs (tRNAs) has previously been associated with the position of particular nucleotides, as opposed to distinctive elements of three-dimensional structure. The contribution of a G.U wobble pair in the acceptor helix of tRNA(Ala) to acceptor identity was examined with synthetic amber suppressor tRNAs in Escherichia coli. The acceptor identity was not affected by replacing the G.U wobble pair in tRNA(Ala) with a G.A, C.A, or U.U wobble pair. Furthermore, a tRNA(Ala) acceptor identity was conferred on tRNA(Lys) when the same site in the acceptor helix was replaced with any of several wobble pairs. Additional data with tRNA(Ala) show that a substantial acceptor identity was retained when the G.U wobble pair was translocated to another site in the acceptor helix. These results suggest that the G.U wobble pair induces an irregularity in the acceptor helix of tRNA(Ala) to match a complementary structure in the aminoacylating enzyme.     

基于齿面闪温最低的行星斜齿轮优化设计

根据Block闪温理论,通过分别计算某单级行星斜齿轮太阳轮和行星轮及行星轮和内齿圈的闪温曲线,对比了改变压力角、螺旋角及太阳轮变位系数对轮齿最高闪温的影响。通过对比,选择最佳齿面闪温．找到了最佳的齿轮压力角、螺旋角及太阳轮变位系数．实现了提高行星齿轮的胶合承载能力,达到了优化行星齿轮的目的。     

Helix signals in proteins

The alpha helix, first proposed by Pauling and co-workers, is a hallmark of protein structure, and much effort has been directed toward understanding which sequences can form helices. The helix hypothesis, introduced here, provides a tentative answer to this question. The hypothesis states that a necessary condition for helix formation is the presence of residues flanking the helix termini whose side chains can form hydrogen bonds with the initial four-helix greater than N-H groups and final four-helix greater than C-O groups; these eight groups would otherwise lack intrahelical partners. This simple hypothesis implies the existence of a stereochemical code in which certain sequences have the hydrogen-bonding capacity to function as helix boundaries and thereby enable the helix to form autonomously. The three-dimensional structure of a protein is a consequence of the genetic code, but the rules relating sequence to structure are still unknown. The ensuing analysis supports the idea that a stereochemical code for the alpha helix resides in its boundary residues.     

基于三螺旋理论的农业科技协同创新实践探索

文章以三螺旋理论作为协同创新的理论依据,构建了农业科技创新三螺旋结构模型,并对其运行机理与发展趋势进行了分析和验证。在此基础上,总结了江苏省推进落实农业科技协同创新的实践成效与启示,为促进农业领域"政产学研用"深度融合、推动多元创新主体协同发展,积累了宝贵的经验。     

An amylose antiparallel double helix at atomic resolution

In the crystal structure of the polyiodide complex (p-nitrophenyl-alpha-maltohexaose(2)) . Ba(I(3))(2) . 22H(2)O, the maltohexaose units form an antiparallel, left-handed double helix with O-2 ... O-3 and O-6 ... O-6 hydrogen bonding and a central cavity that encloses two triiodide units. This structure contrasts with the parallel, left-handed double helix with no central cavity proposed for the A-and B-starch helix and the left-handed single helix in V-amylose and may be relevant for the stabilization of glycogen Structure.     

Activating mineralocorticoid receptor mutation in hypertension exacerbated by pregnancy

Hypertension and pregnancy-related hypertension are major public health problems of largely unknown causes. We describe a mutation in the mineralocorticoid receptor (MR), S810L, that causes early-onset hypertension that is markedly exacerbated in pregnancy. This mutation results in constitutive MR activity and alters receptor specificity, with progesterone and other steroids lacking 21-hydroxyl groups, normally MR antagonists, becoming potent agonists. Structural and biochemical studies indicate that the mutation results in the gain of a van der Waals interaction between helix 5 and helix 3 that substitutes for interaction of the steroid 21-hydroxyl group with helix 3 in the wild-type receptor. This helix 5-helix 3 interaction is highly conserved among diverse nuclear hormone receptors, suggesting its general role in receptor activation.     

Entropically driven helix formation

The helix is a ubiquitous motif for biopolymers. We propose a heuristic, entropically based model that predicts helix formation in a system of hard spheres and semiflexible tubes. We find that the entropy of the spheres is maximized when short stretches of the tube form a helix with a geometry close to that found in natural helices. Our model could be directly tested with wormlike micelles as the tubes, and the effect could be used to self-assemble supramolecular helices.     

Images of the DNA double helix in water

The scanning tunneling microscope can image uncoated DNA submerged in water. The grooves of the double helix were clearly resolved in images of the 146-base pair fragment extracted from calf thymus nucleosome. In contrast to images obtained with dry DNA, the helix pitch varied only a small amount (36 +/- 5 angstroms). The path of the helix shows considerable variation. It is quite straight when the molecules are densely packed, but it curves and bends in isolated molecules.