A Mathematical Model of the Stability Control of Human Thorax and Pelvis Movements During Walking

A mathematical model is developed to study the human thorax and pelvis movements in the frontal plane during normal walking. The model comprises of two-link base-excited inverted pendulums with one-degree of rotational freedom for each link. Since the linear motion of the pelvis has a significant effect on the upper body stability, this effect is included in the model by having a base point moving in the frontal plane in a general way. Furthermore, because the postural stability is the primary requirement of normal human walking, the control law is developed based on Lyapunov's stability theory, which guarantees the stability of the pendulum system around the up-right position. To evaluate the model, the simulation results, including the angular displacement of each link and the torque applied on each link, are compared with those from gait measurements. It is shown that the simulation results match those from gait measurements closely. These results suggest that the proposed model can provide a useful framework for analysis of postural control mechanisms.     

RNA RECOGNITION BY FLUOR-AROMATIC SUBSTITUTED

RNA exhibits a higher structural diversity than DNA and is an important molecule in the biology of life. It shows a number of secondary structures such as duplexes, hairpin loops, bulges, internal loops, etc. However, in natural RNA, bases are limited to the four predominant structures U, C, A, and G and so the number of compounds that can be used for investigation of parameters of base stacking, base pairing, and hydrogen bond is limited. We synthesized different fluoromodifications of RNA building blocks: 1′-deoxy-1′-phenyl-β-d-ribofuranose (B), 1′-deoxy-1′-(4-fluorophenyl)-β-d-ribofuranose (4 FB), 1′-deoxy-1′-(2,4-difluorophenyl)-β-d-ribofuranose (2,4 DFB), 1′-deoxy-1′-(2,4,5-trifluorophenyl)-β-d-ribofuranose (2,4,5 TFB), 1′-deoxy-1′-(2,4,6-trifluorophenyl)-β-d-ribofuranose, 1′-deoxy-1′-(pentafluorophenyl)-β-d-ribofuranose (PFB), 1′-deoxy-1′-(benzimidazol-1-yl)-β-d-ribofuranose (BI), 1′-deoxy-1′-(4-fluoro-1H-benzimidazol-1-yl)-β-d-ribofuranose (4 FBI), 1′-deoxy-1′-(6-fluoro-1H-benzimidazol-1-yl)-β-d-ribofuranose (6 FBI), 1′-deoxy-1′-(4,6-difluoro-1H-benzimidazol-1-yl)-β-d-ribofuranose (4,6 DFBI), 1′-deoxy-1′-(4-trifluoromethyl-1H-benzimidazol-1-yl)-β-d-ribofuranose (4 TFM), 1′-deoxy-1′-(5-trifluoromethyl-1H-benzimidazol-1-yl)-β-d-ribofuranose (5 TFM), and 1′-deoxy-1′-(6-trifluoromethyl-1H-benzimidazol-1-yl)-β-d-ribofuranose (6 TFM). These amidites were incorporated and tested in a defined A, U-rich RNA sequence (12-mer, 5′-CUU UUC XUU CUU-3′ paired with 3′-GAA AAG YAA GAA-5′). Only one position was modified, marked as X and Y, respectively. UV melting profiles of those oligonucleotides were measured.     

Starch-based spherical aggregates: stability of a model flavouring compound, vanillin entrapped therein

Studies on the stability of the vanillin entrapped within the spherical aggregates obtained from amaranth (Amaranthus paniculatus L.), quinoa (Chenopodium quinoa L.), rice (Oryza sativa L.) and colocasia (Colocasia esculenta L.) in the presence of gum Arabic, carboxymethyl cellulose (CMC) and carrageenan at 0.1–1.0% as bonding agents, were obtained by spray drying a 20% (w/w) starch dispersion at 120 °C. Vanillin was used at 5% based on starch (bos). The loss of vanillin over a 6-week storage period followed a first order kinetics. The stability was evaluated in terms of t_1/2 (weeks) from a semi-log plot of percentage retention of vanillin vs. storage time in weeks. The t_1/2 for the total vanillin and entrapped vanillin within the spherical aggregates prepared from different starches decreased in the order, amaranth>colocasia>chenopodium>rice. The t_1/2 decreased with an increase in the amylose content of the starches, although it was not linear. With respect to the bonding agent the stability decreased in the order, gum Arabic>CMC>carrageenan. While CMC and carrageenan gave an increasing value of t_1/2 with an increase in concentration from 0.5 to 1.0%, gum Arabic surprisingly gave a higher t_1/2 value at 0.5% as compared to 1.0%.     

Molecular Dynamics Simulations of Carbon Nanotube Rolling and Sliding on Graphite

Abstract

Molecular dynamics simulations were carried out to investigate the origin of friction for carbon nanotubes on graphite substrates. In an initial simulation, a (10,10) nanotube was placed in an ‘in-registry’ starting position where the hexagonal lattice of the substrate matched that of the nanotube. In a second simulation, the substrate was oriented 90 degrees to the nanotube. A uniform force was applied to the nanotubes for 500 fs to set them into motion. The simulation was then run until the nanotubes stopped moving relative to the substrate. Only sliding was observed in the out-of-registry simulation, while periodic sliding and rolling was observed in the in-registry simulation. The latter is a result of the relatively larger surface corrugation for the in-registry case and occurs to avoid direct atomic collisions between nanotube and substrate atoms as the nanotube is moved along the substrate. Analysis of the kinetic energy suggests that the transition between sliding and rolling contributes to enhanced energy dissipation and higher net friction. These results are consistent with preliminary experimental observations by Superfine and coworkers.     

杂交水稻结实率稳定性的遗传分析

本文采用三套同核异质不育系与５个恢复力不同的恢复系按Ｐ×Ｑ模式配组、分５期播种的试验设计,在ＡＭＭＩ模型分析结实率稳定性的基础上,进一步剖析了不育胞质、保持系、恢复系及其工作的各种遗传效应。     

The structures and stabilities of small diarsenic-doped silicon clusters

The structures and stabilities of As₂-doped Si_n (n = 1-7) clusters have been investigated at the B3LYP level of theory, incorporating the 6-311+G^∗ basis set. An isosceles triangle is predicted to be the lowest-energy structure of the As₂Si cluster, whereas the global minimum of As₂Si₂ possesses an As-As-butterfly structure. The ground state structures for As₂Si₃, As₂Si₄ and As₂Si₅ are all bipyramids: trigonal, tetragonal and pentagonal, respectively, which could have important applications as building blocks to synthesize silicon nanowires. The most stable isomer of As₂Si₆ possesses a tricapped trigonal bipyramid structure. The lowest energy structure of As₂Si₇ can be viewed as a substitutional structure of the tricapped trigonal prism Si₉ isomer. In the majority of the lowest energy isomers, the two As atoms tend to be separated from each other, in order to maximize the number of Si-As bonds, and therefore locate at the axial vertex or face-capping atomic positions, especially for As₂Si₄-As₂Si₇. According to results of the incremental binding energies, the HOMO-LUMO gaps and the vertical ionization potentials, the As₂Si₃ and As₂Si₆ clusters are relatively stable compared to their neighbors. Natural bond orbital analyses suggest that delocalized electrons and multi-centered bonds play an important role in stabilizing the low-energy As₂Si_n structures.     

On the composition of the nucleolus with special reference to its filamentous structure

Summary Different staining procedures, various digestion methods and autoradiographic techniques were employed to study the structure and composition of the nucleolus and of the nucleolonema, after unmasking the latter by adenosine treatment. The presence of DNA, RNA, protein and lipid in these structures has been shown. It has been demonstrated that the filamentous structure within the nucleolus — the nucleolonema— has a core of DNA, around which RNA and protein have accumulated. The structure of the nucleolonema suggests that it is in a highly active state, in synthesizing ribosomal RNA and protein.We take the opportunity to express our gratefulness to the Director, Prof. Dr. Hans Lettré, for providing facilities to work in this Institute. We like to thank our other colleagues, particularly Dr. N. Paweletz, for their valuable help during the course of the investigations.     

头足类若干结构的形态比较

本文首次系统观察分析比较了中国近海头足类的肉鳍、平衡器、齿舌和漏斗器,并参考世界代表性种类和古生头足类的文献和图,全面研究了这些结构形态的式型和亚型,探讨了它们与生活方式和演化的相互关系。     

The shifting sources of racial definition in Trinidad and Tobago,and Guyana: a research agenda

This comparison of ethnic relations in two countries, Trinidad and Tobago, and Guyana, supplements the research findings of synchronic studies of "the social construction of race" by offering a historically based framework to understand particular and local instances of ethnic relations. Drawing on a long historical study of Trinidad and Tobago, and Guyana, I argue that the institutional sources of definition of key "ethnicities" have shifted through the centuries. "Ethnicities" have been successively defined by the institutions of capital, state and community. While these institutions have overlapped in time they are not equally important at a given moment in the matter of defining "ethnicity". The content of the definitions has also varied significantly. At present political communities and the family are the major social institutions that determine "ethnic" content.     

Marine Conservation versus International Free Trade: Reconciling Dolphins with Tuna and Sea Turtles with Shrimp

During the 1990s, the World Trade Organization (WTO) rejected as impermissible unilateral efforts by the United States to promote conservation of endangered marine species through trade sanctions against other governments. These acts of unilateral economic coercion were held to be discriminatory tactics done in unfair restraint of international trade. But in so doing, the WTO findings aroused the ire of environmentalists worldwide. These findings by the WTO became portrayed not as decisions upholding free trade, but as mandates against marine conservation and environmental protection. Even so, this denial of lawful permissibility to use unilateral economic coercion to protect endangered species internationally does not signal the demise of national efforts to conserve living marine resources. Rather, these WTO findings point up the manner in which potential trade and marine conservation disputes should be handled, i.e., through means of peaceful settlement. The key to future international marine conservation relies on a multilateral rather than a unilateral approach. Thus, environmentally conscious governments, such as the United States, should continue to encourage global adoption of marine conservation policies without impinging on international norms and standards of international commercial transactions.     

Molecular dynamics study of carbon nanotube oscillator on gold surface

We investigated the substrate effect of carbon nanotube (CNT) oscillators using classical molecular dynamics simulations. Double-walled CNT oscillators on {100} gold surface were considered. The nanotube–gold interactions induced the compressive deformations of the outer nanotube and affected the transitional velocity and the energy dissipation of the nanotube oscillator. When the inner nanotube was extruded from the outer nanotube, the central regions of the outer nanotube were compressed by the nanotube–gold interactions and then, these compressive forces pushed out the inner nanotube and finally, the transitional velocity of the inner nanotube was slightly increased at the edges regions. Since the energy dissipation of the nanotube oscillator on gold surface was higher than that in vapor, the decrease of the transitional velocity for the nanotube oscillator on gold surface was greater than that for the nanotube oscillator in vapor.     

Structural and magnetic properties of Ln(III) complexes with diimines and crotonato as a bridging ligand

Five new lanthanide complexes displaying crotonato bridges have been prepared: [Gd₂(crot)₆(H₂O)₄] · 4(bpa) (1); [Ho₂(crot)₇]_n · (Hbpa) (2); [Gd₂(crot)₆(bipy)₂] (3); [Ho₂(crot)₆(bipy)₂] (4) and [Nd₂(crot)₆(H₂O)₃]_n (5), where bipy=2,2^′-bipyridine; bpa=di(2-pyridyl)amine; crot=crotonato. The compounds were characterized by magnetic susceptibility measurements and their crystal structures were determined by single crystal X-ray diffraction. These studies showed complexes 1, 3 and 4 to be dimers while structures 2 and 5 are polymeric in nature.     

氧化钛纳米管对即刻种植骨结合影响的实验研究

目的:评价氧化钛纳米管对犬即刻种植骨结合效果的影响。方法:犬拔牙后即刻将光滑表面(对照组)和氧化钛纳米管表面(实验组)种植体植入拔牙窝内,于12周后处死取材,进行显微CT扫描、组织学染色分析以及生物力学检测。结果:扫描电镜显示经过阳极氧化后,钛表面形成了直径为30-80纳米的纳米管状结构;12周后,显微CT扫描结果提示实验组骨体积分数(BV/TV)、骨小梁数目(Tb.N)、骨小梁厚度(Tb.Th)均显著高于对照组,骨小梁间隙(Tb.Sp)显著低于对照组,差异具有统计学意义(P0.05)。术后12周,实验组与对照组骨结合率分别为49.35±11.76%、31.79±13.07%,最大拔出力分别为105.28±27.87N、79.23±20.46N,实验组均显著高于对照组,差异均具有统计学意义(P0.05)。结论:氧化钛纳米管表面有利于促进即刻种植后骨结合的效果。     

组织蛋白酶及其抑制剂研究进展

组织蛋白酶是半胱氨酸蛋白酶家族的主要成员,在生物界已发现20余种,人体中主要存在11种,它们与人类肿瘤、骨质疏松、关节炎等多种重大疾病密切相关,是近年来备受关注的一类靶标蛋白酶。自从20世纪90年代以来,多种组织蛋白酶的晶体结构陆续明确,有关其研究进展较快。本文以人类组织蛋白酶为重点,主要介绍近15年来组织蛋白酶结构、功能和抑制剂研究方面的一些重要进展。     

Synthesis,characterization and bioactivities of a new covalent copper(II) compound derived from {P2Mo5O23}6− and thiosemicarbazones

In this article, a new compound H₂[{Cu(HL)(H₂O)}₂(P₂Mo₅O₂₃)]·5H₂O (1) (HL = 2-acetylpyrazine thiosemicarbazone) has been synthesized and structurally characterized by single-crystal X-ray diffraction of and other detection techniques. Interestingly, the structure of 1 is different from many reported copper-based complexes, in which the [P₂Mo₅O₂₃]⁶⁻, two Cu²⁺ ions and two HL were directly connected by covalent bands. Biological studies demonstrated that 1 indicated moderate antibacterial activity against Escherichia coli (E. coli) and Staphylococcus aureus (S. aureus), and a better cytotoxicity against human hepatic cancer line (SMMC-7721) than Mitoxantrone (Mito), the current clinical anticancer drug. Besides, the antibacterial mechanisms of 1 have been studied by the membrane integrity disruption, the destructive reactive oxygen species generation (ROS), the glutathione (GSH) depletion and the depressed enzymatic activity of respiratory chain dehydrogenases (RCD). These results revealed that the combination of HL, Cu²⁺, [P₂Mo₅O₂₃]⁶⁻ shows a higher antibacterial and cytotoxic activity.