A comparative study of Young's modulus of single-walled carbon nanotube by CPMD, MD, and first principle simulations

Carbon nanotubes (CNTs), due to their exceptional magnetic, electrical and mechanical properties, are promising candidates for several technical applications ranging from nanoelectronic devices to composites. Young's modulus holds the special status in material properties and micro/nano-electromechanical systems (MEMS/NEMS) design. The excellently regular structures of CNTs facilitate accurate simulation of CNTs' behavior by applying a variety of theoretical methods. Here, three representative numerical methods, i.e., Car-Parrinello molecular dynamics (CPMD), density functional theory (DFT) and molecular dynamics (MD), were applied to calculate Young's modulus of single-walled carbon nanotube (SWCNT) with chirality (3,3). The comparative studies showed that the most accurate result is offered by time consuming DFT simulation. MID simulation produced a less accurate result due to neglecting electronic motions. Compared to the two preceding methods the best performance, with a balance between efficiency and precision, was deduced by CPMD.

Thermal energy minimisation in papermaking via MD control approach

This paper reports the application of Advanced Process Control (APC) techniques for improving the thermal energy efficiency of a paperboard-making process by regulating the Machine Direction (MD) profile of the basis weight and moisture content of the paper-board. A Model Predictive Controller (MPC) is designed so that the sheet moisture and basis weight tracking errors along with variations of the sheet moisture and basis weight are reduced. Also, the drainage is maximised through improved wet-end stability which can facilitate driving the sheet moisture set-point closer to its upper specification limit over time. It is shown that the proposed strategy can result in reducing steam usage by 8-10%. A simulation study based on a UK board machine is presented to show the effectiveness of the proposed technique. © 2011 Intl Journal of Adv Mechatr.

Butt-Joint Monolithicaily Integrated DFB-LD/EA-MD Light Source for 10Gbit/s Transmission

This paper reports on the design, fabrication, and performance of an integrated electro-absorptive modulated laser based on butt-joint configuration for 10Gbit/s application. This paper mainly aims at two aspects. One is to improve the optical coupling between the laser and modulator; another is to increase the bandwidth of such devices by reducing the capacitance parameter of the modulator. The integrated devices exhibit high static and dynamic characteristics. Typical threshold current is 15mA,with some value as low as 8mA. Output power at 100mA is more than 10mW. The extinction characteristics,modulation bandwidth, and electrical return loss are measured. 3dB bandwidth more than 10GHz is monitored.

Mechanical Behavior of Nanometer Ni by MD Simulation

The indention simulation of the crystal Ni is carried out by molecular dynamics technique (MD) to study the mechanical behavior at nanometer scales, the indenter tips with sphere shape is used. Some defects such as dislocations, point defects are observed. It is found that defects (dislocations, amorphous) nucleated is from local region near the pin tip or the sample surface. The temperature distribution of local region is analyzed and it can explain our MD simulation result.

jλ变换与离散振荡指标Md在海洋机器人控制系统动态综合中的应用

本文给出由连续系统的S域,到离散领域?的转换的通式。并给出了离散传递函数W(?)的基本属性、离散振荡指标Md的基本概念、?变换的稳定判据、二阶无静差数字随动系统的动态综合、Md综合在海洋机器人航向控制中的应用。

Legacy Resource Management Program Archaeological Reconnaissance Survey, United States Naval Academy, Annapolis, MD.

The Archaeological Reconnaissance Survey of United States Naval Academy will provide the Navy with a rich understanding of the history of this property. A National Register of Historic Places District, such as the Academy, deserves a thorough analysis of its past, in order to preserve what exists and to plan for the future. The goal of this project is to investigate the history of the Academy through traditional historic research, innovative computer analysis of historic maps, oral history interviews, and tract histories. This information has been synthesized to provide the Navy with a planning tool for Public Works, a concise look at the cartographic history of the Academy, and reference manual of the vast amounts of information which have been gathered during the course of this project. This information can serve as a reference tool to help the Public Works department comply with Section 106 regulations of the Historic Sites Preservation Act, with regard to construction. It can also serve as a source of cartographic history for those interested in the Academy's physical development, and as a way of preserving the culture of residents in Annapolis. This program and archaeological survey will ultimately serve to add to the rich history of the United States Naval Academy while preserving an important part of our nation's heritage.

What the brain stem tells the frontal cortex. II. Role of the SC-MD-FEF pathway in corollary discharge.

One way we keep track of our movements is by monitoring corollary discharges or internal copies of movement commands. This study tested a hypothesis that the pathway from superior colliculus (SC) to mediodorsal thalamus (MD) to frontal eye field (FEF) carries a corollary discharge about saccades made into the contralateral visual field. We inactivated the MD relay node with muscimol in monkeys and measured corollary discharge deficits using a double-step task: two sequential saccades were made to the locations of briefly flashed targets. To make second saccades correctly, monkeys had to internally monitor their first saccades; therefore deficits in the corollary discharge representation of first saccades should disrupt second saccades. We found, first, that monkeys seemed to misjudge the amplitudes of their first saccades; this was revealed by systematic shifts in second saccade end points. Thus corollary discharge accuracy was impaired. Second, monkeys were less able to detect trial-by-trial variations in their first saccades; this was revealed by reduced compensatory changes in second saccade angles. Thus corollary discharge precision also was impaired. Both deficits occurred only when first saccades went into the contralateral visual field. Single-saccade generation was unaffected. Additional deficits occurred in reaction time and overall performance, but these were bilateral. We conclude that the SC-MD-FEF pathway conveys a corollary discharge used for coordinating sequential saccades and possibly for stabilizing vision across saccades. This pathway is the first elucidated in what may be a multilevel chain of corollary discharge circuits extending from the extraocular motoneurons up into cerebral cortex.

The Plasmodium falciparum Malaria M1 Alanyl Aminopeptidase (PfA-M1): Insights of Catalytic Mechanism and Function from MD Simulations

Malaria caused by several species of Plasmodium is major parasitic disease of humans, causing 1-3 million deaths worldwide annually. The widespread resistance of the human parasite to current drug therapies is of major concern making the identification of new drug targets urgent. While the parasite grows and multiplies inside the host erythrocyte it degrades the host cell hemoglobin and utilizes the released amino acids to synthesize its own proteins. The P. falciparum malarial M1 alanyl-aminopeptidase (PfA-M1) is an enzyme involved in the terminal stages of hemoglobin digestion and the generation of an amino acid pool within the parasite. The enzyme has been validated as a potential drug target since inhibitors of the enzyme block parasite growth in vitro and in vivo. In order to gain further understanding of this enzyme, molecular dynamics simulations using data from a recent crystal structure of PfA-M1 were performed. The results elucidate the pentahedral coordination of the catalytic Zn in these metallo-proteases and provide new insights into the roles of this cation and important active site residues in ligand binding and in the hydrolysis of the peptide bond. Based on the data, we propose a two-step catalytic mechanism, in which the conformation of the active site is altered between the Michaelis complex and the transition state. In addition, the simulations identify global changes in the protein in which conformational transitions in the catalytic domain are transmitted at the opening of the N-terminal 8 angstrom-long channel and at the opening of the 30 angstrom-long C-terminal internal chamber that facilitates entry of peptides to the active site and exit of released amino acids. The possible implications of these global changes with regard to enzyme function are discussed.

Activation of human TLR4/MD-2 by hypoacylated lipopolysaccharide from a clinical isolate of Burkholderia cenocepacia

Lung infection by Burkholderia species, in particular B. cenocepacia, accelerates tissue damage and increase post-lung transplant mortality in cystic fibrosis patients. Host- microbes interplay largely depends on interactions between pathogen specific molecules and innate immune receptors such as the Toll-like receptor 4 (TLR4), which recognizes the lipid A moiety of the bacterial lipopolysaccharide (LPS). The human TLR4/MD-2 LPS receptor complex is strongly activated by hexa-acylated lipid A and poorly activated by underacylated lipid A. Here, we report that B. cenocepacia LPS strongly activates human TLR4/MD-2 despite its lipid A having only five acyl chains. Further, we show that aminoarabinose residues in lipid A contribute to TLR4-lipid A interactions, and experiments in a mouse model of LPS-induced endotoxic shock confirmed the pro- inflammatory potential of B. cenocepacia penta-acylated lipid A. Molecular modeling, combined with mutagenesis of TLR4-MD2 interactive surfaces, suggests that longer acyl chains and the aminoarabinose residues in the B. cenocepacia lipid A allow exposure of the fifth acyl chain on the surface of MD-2 enabling interactions with TLR4 and its dimerization. Our results provide a molecular model for activation of the human TLR4/MD- 2 complex by penta-acylated lipid A, explaining the ability of hypoacylated B. cenocepacia LPS to promote pro- inflammatory responses associated to the severe pathogenicity of this opportunistic bacterium.