Product Distributions of Cytochrome P450 OleTJE with Phenyl-Substituted Fatty Acids: A Computational Study

There are two types of cytochrome P450 enzymes in nature, namely, the monooxygenases and the peroxygenases. Both enzyme classes participate in substrate biodegradation or biosynthesis reactions in nature, but the P450 monooxygenases use dioxygen, while the peroxygenases take H₂O₂ in their catalytic cycle instead. By contrast to the P450 monooxygenases, the P450 peroxygenases do not require an external redox partner to deliver electrons during the catalytic cycle, and also no external proton source is needed. Therefore, they are fully self-sufficient, which affords them opportunities in biotechnological applications. One specific P450 peroxygenase, namely, P450 OleT_JE, reacts with long-chain linear fatty acids through oxidative decarboxylation to form hydrocarbons and, as such, has been implicated as a suitable source for the biosynthesis of biofuels. Unfortunately, the reactions were shown to produce a considerable amount of side products originating from C^α and C^β hydroxylation and desaturation. These product distributions were found to be strongly dependent on whether the substrate had substituents on the C^α and/or C^β atoms. To understand the bifurcation pathways of substrate activation by P450 OleT_JE leading to decarboxylation, C^α hydroxylation, C^β hydroxylation and C^α–C^β desaturation, we performed a computational study using 3-phenylpropionate and 2-phenylbutyrate as substrates. We set up large cluster models containing the heme, the substrate and the key features of the substrate binding pocket and calculated (using density functional theory) the pathways leading to the four possible products. This work predicts that the two substrates will react with different reaction rates due to accessibility differences of the substrates to the active oxidant, and, as a consequence, these two substrates will also generate different products. This work explains how the substrate binding pocket of P450 OleT_JE guides a reaction to a chemoselectivity.     

Superlattice and Quantum Dot Unipolar Barrier Infrared Detectors

We report device performance and provide theoretical analysis of a modified long-wavelength complementary barrier infrared detector structure that incorporates a double tunnel junction contact designed for simpler material growth while retaining the robustness for processing. We also provide analysis of a mid-wavelength quantum dot barrier infrared detector and explain its spectral shape and turn-on characteristics.     

Cellulose filter coated with m‐aramid for water disinfection

Cellulose filters were dipped and padded with m‐aramid dissolved in N,N‐dimethylacetamide followed by coagulation in distilled water. The coated filters were then chlorinated in a hypochlorite solution. The liquid permeability of the m‐aramid‐coated cellulose filters was examined. The resulting chlorinated and unchlorinated filters were assessed for their ability to disinfect contaminated water. The chlorinated m‐aramid‐coated cellulose filter produced 5 log reductions of Escherichia coli and Staphylococcus aureus, which was much higher than that observed on the unchlorinated m‐aramid‐coated cellulose filter. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Two visual systems in monitoring of dynamic traffic: Effects of visual disruption

Studies from neurophysiology and neuropsychology provide support for two separate object- and location-based visual systems, ventral and dorsal. In the driving context, a study was conducted using a change detection paradigm to explore drivers’ ability to monitor the dynamic traffic flow, and the effects of visual disruption on these two visual systems. While driving, a discrete change, such as vehicle location, color, or identity, was occasionally made in one of the vehicles on the road ahead of the driver. Experiment results show that without visual disruption, all changes were detected very well; yet, these equally perceivable changes were disrupted differently by a brief blank display (150 ms): the detection of location changes was especially reduced. The disruption effects were also bigger for the parked vehicle compared to the moving ones. The findings support the different roles for two visual systems in monitoring the dynamic traffic: the “where”, dorsal system, tracks vehicle spatiotemporal information on perceptual level, encoding information in a coarse and transient manner; whereas the “what”, ventral system, monitors vehicles’ featural information, encoding information more accurately and robustly. Both systems work together contributing to the driver's situation awareness of traffic. Benefits and limitations of using the driving simulation are also discussed.     

Hydroxylamine production: will a QRA help you decide?

The recent publication by the US Chemical Safety Board (CSB) concerning its findings on the Concept Sciences Inc. (CSI) incident involving hydroxylamine (HA) has raised issues with regard to safe production of HA. This CSI incident was followed by another incident that destroyed the Nissin Chemical HA plant in Japan, and today BASF is the sole commercial producer of HA. HA is an important solvent in the pharmaceutical industry and is used as an etching agent in the semi-conductor industry.This paper discusses a Quantitative Risk Assessment of a generic HA production plant, which integrates the findings of the CSB report and the knowledge of potential HA reactivity hazards based on research at the Mary Kay O'Connor Process Safety Center. The intent is to highlight safety concerns and major risk factors in the production and handling of HA and to provide risk assessment guidelines for potential manufacturers. These guidelines are also applicable to the production strategies for other hazardous chemicals.     

Millimeter wave generation on nonlinear transmission lines

In recent years, nonlinear transmission lines (nltls) have successfully been used to generate ultrashort electrical pulses and transients from a sinusoidal input signal. In the frequency domain, this pulse compression results from the generation of a large number of harmonics with suitable phase relationships. In this paper, special examples of nltls are studied which are capable to produce millimeter wave signals at selected frequencies, here by second and third harmonic generation and nonlinear active wave propagation effects. Bi-modal transmission lines are particular discussed which provide the necessary dispersion for high conversion efficiencies.     

Time continuity in cohesive finite element modeling

We introduce the notion of time continuity for the analysis of cohesive zone interface finite element models. We focus on ‘initially rigid’ models in which an interface is inactive until the traction across it reaches a critical level. We argue that methods in this class are time discontinuous, unless special provision is made for the opposite. Time discontinuity leads to pitfalls in numerical implementations: oscillatory behavior, non‐convergence in time and dependence on nonphysical regularization parameters. These problems arise at least partly from the attempt to extend uniaxial traction–displacement relationships to multiaxial loading. We also argue that any formulation of a time‐continuous functional traction–displacement cohesive model entails encoding the value of the traction components at incipient softening into the model. We exhibit an example of such a model. Most of our numerical experiments concern explicit dynamics. Copyright © 2003 John Wiley & Sons, Ltd.     

以GIS为基础的城市能源供给设施风险信息系统

本文主要介绍了一种可以对危害城市公共安全的主要灾害进行控制的风险信息系统(RIS).风险信息系统主要为城市内危险设施,如石油液化气(LPG)储存地或加油站点等,提供灾害评价、紧急措施和重建程序方面的信息;主要包括应急规划信息系统、风险评估信息系统和地理信息系统三个子系统.本文通过仁川市液化石油气储备站的一个案例来说明该系统在实际运用中的具体操作.     

无赖的逻辑

人生的职业生涯是很漫长的过程，但是其中的五个阶段被誉为黄金阶段，让我们来一起分享一下。首先是二十四岁到二十九岁．我称做工作试用期。在此期间要尽量去摸索、尝试各种工作，毕竟实际理论与理想总会有所差距，常听一些刚入社会的年轻人抱怨：这份工作没有前途、根本学不到东西。甚至一些年纪已不小的人，