Redesigning the active site of Geotrichum candidum lipase

Attempts to engineer enzymes with unique catalytic propertieshave largely focused on altering the existing specificitiesby reshaping the substrate binding pockets. Few experimentshave aimed at modifying the configuration of the residues essentialfor catalysis. The difference in the topological location ofthe triad acids of Geotrichum candidum lipase (GCL) and thecatalytic domain of human pancreatic lipase (HPL), despite greatsimilarities in their topologies and 3-D structures, suggestthat these are related enzymes whose catalytic triads have beenrearranged in the course of evolution (Schrag et aL, 1992).In this study we prepared a double mutant GCL in which the catalytictriad acid is shifted to the position equivalent to the locationof the triad acid of HPL. The double mutant maintains 10% ofthe wild type activity against triglycerides and the fluorogenicester 4-methylumbelliferyl-oleate. The only significant differencesbetween the 3-D structures of the double mutant and wild typeGCL are at the mutated sites. Even the water structure in theregion of the triad is unchanged. The hydrogen bonding patternof the catalytic triad of the double mutant is very similarto that of pancreatic lipase. The acid of the double mutantis stabilized by only two hydrogen bonds, whereas three hydrogenbonds are observed in the wild type enzyme. These results stronglysupport the hypothesis that the pancreatic Upases are evolutionaryswitchpoints between the two observed arrangements of the catalytictriads supported by the /ß hydrolase fold and suggestthat this fold provides a stable protein core for engineeringenzymes with unique catalytic properties.     

Aromaticity as a Quantitative Concept. 2. Sixteen familiar five- and six-membered monocyclic heterocycles

Restudy of an almost complete data set of 12 characteristics for 16 common heterocycles confirms the previous conclusion [1] of the independence of „classical”︁ and of „magnetic”︁ aromaticity. The scores for the individual heterocycles correlate well with their chemical structure.     

Designing and optimization of parameters of delta‐4 parallel manipulator for a given workspace

In the paper, the algorithm of designing some geometrical parameters of a Delta parallel manipulator has been described. The manipulator is to work in a specified workspace, which is given as a set of points. The first step of the algorithm seeks the possible solutions, and because there are an infinite number of them, the objective of the second step is to limit the number by an optimization. Owing to this, it is possible to find parameters of the manipulator, whose workspace contains the specified points. © 2003 Wiley Periodicals, Inc.     

Prospective safety performance evaluation on construction sites

This paper presents a systematic Structural Equation Modeling (SEM) based approach for Prospective Safety Performance Evaluation (PSPE) on construction sites, with causal relationships and interactions between enablers and the goals of PSPE taken into account. According to a sample of 450 valid questionnaire surveys from 30 Chinese construction enterprises, a SEM model with 26 items included for PSPE in the context of Chinese construction industry is established and then verified through the goodness-of-fit test. Three typical types of construction enterprises, namely the state-owned enterprise, private enterprise and Sino-foreign joint venture, are selected as samples to measure the level of safety performance given the enterprise scale, ownership and business strategy are different. Results provide a full understanding of safety performance practice in the construction industry, and indicate that the level of overall safety performance situation on working sites is rated at least a level of III (Fair) or above. This phenomenon can be explained that the construction industry has gradually matured with the norms, and construction enterprises should improve the level of safety performance as not to be eliminated from the government-led construction industry. The differences existing in the safety performance practice regarding different construction enterprise categories are compared and analyzed according to evaluation results. This research provides insights into cause–effect relationships among safety performance factors and goals, which, in turn, can facilitate the improvement of high safety performance in the construction industry.     

Particulate Matter size distribution in the exhaust gas of a modern diesel Engine fuelled with a biodiesel blend

The characteristics of particulate mater size distribution in the exhaust gas of an automotive diesel engine have been studied for a biodiesel blend of 30% rapeseed methyl ester (RME) and 70% ultra low sulphur diesel (ULSD) by volume (B30). The engine, a twin-turbo charged V6 equipped with a common rail fuel injection system, was operated on 16 steady-state points extracted from a corresponding New European Driving Cycle test with no engine system modification and a fast differential mobility spectrometer was used to determine the particulate number concentration and distribution. It is shown that the number-size distribution is dependent on engine operating conditions including the rate of exhaust gas recirculation (EGR). Compared with ULSD, B30 leads to a 41% smaller average size of the particles with EGR but gives rise to a higher number concentration under certain engine operating conditions, with the differences varying between nucleation and accumulation mode. The calculated particle total mass for B30 combustion aerosol is lower than the value with ULSD for all the engine operating conditions tested. The average B30 aerosol was 28% smaller in size on mass basis, compared to ULSD aerosol. For both fuels, the relationship between the particle total number and total mass has been found to be directly correlated and both the number and the mass of particles increase when the mean diameters of particles increase.     

An ergonomic analysis framework for construction tasks

This paper presents a new methodology for obtaining a quantitative measure of human task performance complexity and effort on the construction site. An example application of the developed methodology to the analysis of concrete placement tasks is provided. The developed method can be used to aid construction equipment manufacturers in understanding and assessing the automation potential for a variety of construction work tasks.     

Decision support analysis for safety control in complex project environments based on Bayesian Networks

This paper presents a novel and systemic decision support model based on Bayesian Networks (BN) for safety control in dynamic complex project environments, which should go through the following three sections. At first, priori expert knowledge is integrated with training data in model design, aiming to improve the adaptability and practicability of model outcome. Then two indicators, Model Bias and Model Accuracy, are proposed to assess the effectiveness of BN in model validation, ensuring the model predictions are not significantly different from the actual observations. Finally we extend the safety control process to the entire life cycle of risk-prone events in model application, rather than restricted to pre-accident control, but during-construction continuous and post-accident control are included. Adapting its reasoning features, including forward reasoning, importance analysis and background reasoning, decision makers are provided with systematic and effective support for safety control in the overall work process. A frequent safety problem, ground settlement during Wuhan Changjiang Metro Shield Tunnel Construction (WCMSTC), is taken as a case study. Results demonstrate the feasibility of BN model, as well as its application potential. The proposed model can be used by practitioners in the industry as a decision support tool to increase the likelihood of a successful project in complex environments.     

Influence of Plasma Waves on the Photoacoustic Signal of Silicon Samples

This article presents the results of theoretical and experimental studies of the influence of plasma waves on the photoacoustic signals of Si samples. The aim of these investigations was to find and examine the sensitive measurement configurations and the configurations of the sample in the photoacoustic cell for detection and measurement of the lifetime of excess carriers. Two measurement configurations were examined: transmission and phase lag and two configurations of the sample in the photoacoustic cell. This article demonstrates that both configurations for samples with differently prepared surfaces are effective for observation and detection of plasma waves with the photoacoustic method.     

用于电子政府的数字签名-一种长期的安全结构

The framework of digital signature based on qualified certificates and X.509 architecture is known to have many security risks. Moreover, the fraud prevention mechanism is fragile and does not provide strong guarantees that can be necessary for flow of legal documents. Mediated signatures have been proposed as a mechanism to effectively disable signature cards. In this paper we propose further mechanisms that can be applied on top of mediated RSA, compatible with the standard format, but providing security guarantees even in the case when RSA becomes broken or the keys are compromised. The solution is immune tokleptographic attacks as only deterministic algorithms are used on user's side.     

Design and investigation of a partial admission radial 2.5-kW organic Rankine cycle micro-turbine

In recent years, organic Rankine cycle (ORC) micro-turbine distributed energy systems have become increasingly popular. Design methods for this type of fluid-flow machinery are still being developed. In this paper, a 2.5-kW radial-flow four-stage ORC micro-turbine with HFE7100 is experimentally and numerically analysed. CFX ANSYS was used for the numerical analysis as well as a computational fluid dynamics (CFD) in-house code based on finite volume discretisation with Godunov-type upwind differencing, a high-resolution essentially non-oscillatory (ENO) scheme and a turbulence model with two-equation shear stress transport (SST). The experimental stand and measurements are described. The numerical results are compared with experimental ones and prove to be satisfactory. The developed micro-turbine does not require the use of any traditional lubricant (oil-free technology) because the bearings are lubricated with the vapour of the low-boiling HFE7100. The developed micro-turbine is an innovative solution providing maintenance-free operation and high durability with low friction losses. The experimental studies have also confirmed a considerable reduction in noise and vibration levels.