Conformational analysis of thiopeptides: free energy calculations on the effects of thio-substitutions on the conformational distributions of alanine dipeptides.

When the oxygen atom in a peptide bond is replaced by a sulfur atom, the restriction in the available conformational space and the ability of thioamides to confer resistance to enzymatic degradation renders thioamides as potentially useful building blocks for drug design and protein engineering. The solvation free energy differences between conformers of the same dipeptide can be high. Yet, previous conformational studies, basing on the (phi, psi) conformational energy maps of thio-substituted dipeptides, neglected both explicit water interactions and free energy considerations. In this paper, the (phi, psi) conformational free energy maps are obtained by single umbrella sampling in an explicit water environment for both alanine dipeptide and the corresponding thioamide derivatives. The phi and psi angles for the minima in the relative energy maps calculated with dielectric of 80 are similar to the corresponding phi and psi angles in the relative free energy maps for both Ac-Ala-NHMe (Ac: acetyl; Ala: alanine) and Act-Alat-NHMe (Act: thio-acetyl; Alat: thio-alanine). However, some large differences between the relative energy and relative free energy of major minima indicate that the consideration of free energy is important in determination of the relative occupancy of particular minima. Free energy maps for both Ac-Ala-NHMe and Act-Alat-NHMe show that thio-substitution favors conformations where phi < 0 because of the deeper beta and alphaR minima. The changes in the position and relative stability of minima were explained in terms of the destabilization of the regions near phi = -120, 0 and 120, psi = 60, -60, 180, which correspond to the increased steric hindrance due to the bulkier sulfur atom.     

The Epilog system-automated long-term EEG monitoring for epilepsy

Epilog, a Unix-based real-time operational support system for electroencephalogram (EEG) waveform acquisition, storage, analysis, display, and printing, is described. The system is designed to be used for diagnosis and surgical planning in a large epilepsy program. The implemented system has two monitoring units consisting of four rooms with their associated computer, video, and medical support systems. A central computer hub performs Epilog services for each unit. Each hub acquires and processes up to 256 channels of EEG 24 h per day, and serves as a control center for much of the automation in the unit. The EEG data structures and data flow used in Epilog are discussed.<>     

遥控钥匙门禁系统的路径损耗

在遥控钥匙门禁(RKE)系统中,可以用钥匙扣上的发射器从远端开锁,发射器将无线编码发送到汽车内的接收机。遥控钥匙门禁(RKE)系统通常工作在ISM频段,包括315MHz和433．92MHz。随着远程启动和带校验的RKE的出现,设计     

CRACK GROWTH IN A TITANIUM ALUMINIDE ALLOY UNDER THERMAL MECHANICAL CYCLING

Abstract— The fatigue crack growth behavior in a titanium aluminide (Ti₃Al) alloy under thermo-mechanical loading as well as under elevated temperature conditions was investigated. The thermal mechanical fatigue crack growth behavior appears, in a general sense, to follow the same trends observed in similar data obtained in tests on nickel-base superalloys. However, crack growth in Ti₃Al appeared to be influenced by blunting of the crack tip due to creep in addition to a cyclic-dependent contribution together with time dependent or environmental enhanced degradation. This complex phenomenon in Ti₃Al is unlike that in nickel-base superalloys where crack growth was found to be due to a linear combination of cycle and time dependent contributions. Thus, the linear cumulative modelling technique is not applicable to the tested Ti₃Al.     

Methods and tools for decision making in engineering design

This paper describes the background to the setting up of the Cambridge Engineering Design Centre. An overview of the design research and applications programme of the Cambridge EDC is given. Four research themes are identified: functional modelling, configuration and manufacturing optimization, materials and process selection, and process interpretation and management. Application areas include aerospace systems, heavy duty vehicles and medical equipment.     

Illness intrusiveness and quality of life in end-stage renal disease: Comparison and stability across treatment modalities.

Examined the impact of illness intrusiveness (ILI) on quality of life (QOL) in 99 patients with end-stage renal disease. Ss were interviewed twice, 6 wks apart, to determine differences in perceived ILI across treatment modalities, life domains, and time. Life domains were affected differentially across treatments. Perceived ILI correlated significantly with treatment time requirements, uremic symptoms, intercurrent nonrenal illnesses, fatigue, and difficulties in daily activities. Significant QOL differences emerged across treatment modalities for satisfaction/happiness and pessimism/illness related concerns but not for depression/distress. Perceived ILI correlated significantly with each of these QOL measures. Findings substantiate the construct of ILI as a mediator of the psychosocial impact of chronic, life-threatening illness. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

A 50-Gb/s IP router

Aggressive research on gigabit-per-second networks has led to dramatic improvements in network transmission speeds. One result of these improvements has been to put pressure on router technology to keep pace. This paper describes a router, nearly completed, which is more than fast enough to keep up with the latest transmission technologies. The router has a backplane speed of 50 Gb/s and can forward tens of millions of packets per second     

Toward global metabolomics analysis with hydrophilic interaction liquid chromatography-mass spectrometry: improved metabolite identification by retention time prediction

Metabolomics is an emerging field of postgenomic biology concerned with comprehensive analysis of small molecules in biological systems. However, difficulties associated with the identification of detected metabolites currently limit its application. Here we demonstrate that a retention time prediction model can improve metabolite identification on a hydrophilic interaction chromatography (HILIC)-high-resolution mass spectrometry metabolomics platform. A quantitative structure retention relationship (QSRR) model, incorporating six physicochemical variables in a multiple-linear regression based on 120 authentic standard metabolites, shows good predictive ability for retention times of a range of metabolites (cross-validated R(2) = 0.82 and mean squared error = 0.14). The predicted retention times improved metabolite identification by removing 40% of the false identifications that occurred with identification by accurate mass alone. The importance of this procedure was demonstrated by putative identification of 690 metabolites in extracts of the protozoan parasite Trypanosoma brucei, thus allowing identified metabolites to be mapped onto an organism-wide metabolic network, providing opportunities for future studies of cellular metabolism from a global systems biology perspective.