Computational screening and design of DNA-linked molecular nanowires

DNA can be used as a structural component in the process of making conductive polymers called nanowires. Accurate molecular models could lead to a better understanding of how to prepare these types of materials. Here we present a computational tool that allows potential DNA-linked polymer designs to be screened and evaluated. The approach involves an iterative procedure that adjusts the positions of DNA-linked monomers in order to obtain reasonable molecular geometry compatible with normal DNA conformations and with the properties of the polymer being formed. This procedure has been used to evaluate designs already reported experimentally, as well as to suggest a new design based on pyrrylene vinylene (PV) monomers.     

How does processing affect storage in working memory tasks? Evidence for both domain-general and domain-specific effects.

[Correction Notice: An erratum for this article was reported in Vol 37(3) of Journal of Experimental Psychology: Learning, Memory, and Cognition (see record 2011-08992-004). Chen and Cowan (2009) is correctly cited in the body of the article but the reference at the end of the article is incorrect. The correct reference is in the correction.] Two studies that examine whether the forgetting caused by the processing demands of working memory tasks is domain-general or domain-specific are presented. In each, separate groups of adult participants were asked to carry out either verbal or nonverbal operations on exactly the same processing materials while maintaining verbal storage items. The imposition of verbal processing tended to produce greater forgetting even though verbal processing operations took no longer to complete than did nonverbal processing operations. However, nonverbal processing did cause forgetting relative to baseline control conditions, and evidence from the timing of individuals' processing responses suggests that individuals in both processing groups slowed their responses in order to “refresh” the memoranda. Taken together the data suggest that processing has a domain-general effect on working memory performance by impeding refreshment of memoranda but can also cause effects that appear domain-specific and that result from either blocking of rehearsal or interference. (PsycINFO Database Record (c) 2011 APA, all rights reserved)     

Toxicity of fumonisin from Fusarium verticillioides culture material and moniliformin from Fusarium fujikuroi culture material when fed singly and in combination to growing barrows

The effects of fumonisin B1 (FB1) from Fasarium verticillioides culture material and moniliformin from Fusarum fujikuroi culture material on growing barrows were evaluated. Four groups of six barrows (three replicates of two each; mean body weight, 11.1 kg) were fed diets containing 0 mg of FB1 and 0 mg of moniliformin per kg of feed (control), 100 mg of FB1 per kg of feed, 100 mg of moniliformin per kg of feed, and 100 mg of FB1 plus 100 mg of moniliformin per kg of feed. Barrows were fed these diets for 28 days. Body weight gain, feed efficiency, serum biochemical analytes, and hematological values were adversely affected by the FB1 and the FB1-plus-moniliformin diets. The moniliformin diet decreased body weight gain. Two barrows in the moniliformin diet group died, and two barrows in the FB1-plus-moniliformin diet group died. All deaths occurred during the first 6 days of the study. Mild to moderate lesions were observed microscopically in heart and lung tissues of the groups fed moniliformin and FB1 plus moniliformin and in liver tissues of the groups fed FB1 and FB1 plus moniliformin. Except for the acute mortality associated with the two diets containing moniliformin. clinical disease induced by the combined feeding of these two mycotoxins appears to be additive or less than additive and due primarily to the toxic expression of FB1.     

Effects of sediment-associated extractable metals, degree of sediment grain sorting, and dissolved organic carbon upon Cryptosporidium parvum removal and transport within riverbank filtration sediments, Sonoma County, California

Oocysts of the protozoan pathogen Cryptosporidium parvum are of particular concern for riverbank filtration (RBF) operations because of their persistence, ubiquity, and resistance to chlorine disinfection. At the Russian River RBF site (Sonoma County, CA), transport of C. parvum oocysts and oocyst-sized (3 μm) carboxylate-modified microspheres through poorly sorted (sorting indices, σ(1), up to 3.0) and geochemically heterogeneous sediments collected between 2 and 25 m below land surface (bls) were assessed. Removal was highly sensitive to variations in both the quantity of extractable metals (mainly Fe and Al) and degree of grain sorting. In flow-through columns, there was a log-linear relationship (r(2) = 0.82 at p < 0.002) between collision efficiency (α, the probability that colloidal collisions with grain surfaces would result in attachment) and extractable metals, and a linear relationship (r(2) = 0.99 at p < 0.002) between α and σ(1). Collectively, variability in extractable metals and grain sorting accounted for ～83% of the variability in α (at p < 0.0002) along the depth profiles. Amendments of 2.2 mg L(-1) of Russian River dissolved organic carbon (DOC) reduced α for oocysts by 4-5 fold. The highly reactive hydrophobic organic acid (HPOA) fraction was particularly effective in re-entraining sediment-attached microspheres. However, the transport-enhancing effects of the riverine DOC did not appear to penetrate very deeply into the underlying sediments, judging from high α values (～1.0) observed for oocysts being advected through unamended sediments collected at ～2 m bls. This study suggests that in evaluating the efficacy of RBF operations to remove oocysts, it may be necessary to consider not only the geochemical nature and size distribution of the sediment grains, but also the degrees of sediment sorting and the concentration, reactivity, and penetration of the source water DOC.     

Thermally Sprayed Aluminum (TSA) Coatings for Extended Design Life of 22%Cr Duplex Stainless Steel in Marine Environments

In this article, evaluation of sealed and unsealed thermally sprayed aluminum (TSA) for the protection of 22%Cr duplex stainless steel (DSS) from corrosion in aerated, elevated temperature synthetic seawater is presented. The assessments involved general and pitting corrosion tests, external chloride stress corrosion cracking (SCC), and hydrogen-induced stress cracking (HISC). These tests indicated that DSS samples, which would otherwise fail on their own in a few days, did not show pitting or fail under chloride SCC and HISC conditions when coated with TSA (with or without a sealant). TSA-coated specimens failed only at very high stresses (>120% proof stress). In general, TSA offered protection to the underlying or exposed steel by cathodically polarizing it and forming a calcareous deposit in synthetic seawater. The morphology of the calcareous deposit was found to be temperature dependent and in general was of duplex nature. The free corrosion rate of TSA in synthetic seawater was measured to be ~5-8 μm/year at ~18 °C and ~6-7 μm/year at 80 °C.     

Commitment and effector phases of the physiological cell death pathway elucidated with respect to Bcl-2 caspase, and cyclin-dependent kinase activities

Physiological cell deaths occur ubiquitously throughout biology and have common attributes, including apoptotic morphology with mitosis-like chromatin condensation and prelytic genome digestion. The fundamental question is whether a common mechanism of dying underlies these common hallmarks of death. Here we describe evidence of such a conserved mechanism in different cells induced by distinct stimuli to undergo physiological cell death. Our genetic and quantitative biochemical analyses of T- and B-cell deaths reveal a conserved pattern of requisite components. We have dissected the role of cysteine proteases (caspases) in cell death to reflect two obligate classes of cytoplasmic activities functioning in an amplifying cascade, with upstream interleukin-1beta-converting enzyme-like proteases activating downstream caspase 3-like caspases. Bcl-2 spares cells from death by punctuating this cascade, preventing the activation of downstream caspases while leaving upstream activity undisturbed. This observation permits an operational definition of the stages of the cell death process. Upstream steps, which are necessary but not themselves lethal, are modulators of the death process. Downstream steps are effectors of, and not dissociable from, actual death; the irreversible commitment to cell death reflects the initiation of this downstream phase. In addition to caspase 3-like proteases, the effector phase of death involves the activation in the nucleus of cell cycle kinases of the cyclin-dependent kinase (Cdk) family. Nuclear recruitment and activation of Cdk components is dependent on the caspase cascade, suggesting that catastrophic Cdk activity may be the actual effector of cell death. The conservation of the cell death mechanism is not reflected in the molecular identity of its individual components, however. For example, we have detected different cyclin-Cdk pairs in different instances of cell death. The ordered course of events that we have observed in distinct cases reflects essential thematic elements of a conserved sequence of modulatory and effector activities comprising a common pathway of physiological cell death.     

绿色BIM如何助力绿色设计和建造

近年来,绿色建筑及绿色BIM已经成为建筑业界流行的趋势。BIM用户期待着能在更高水平上应用BIM工具,以实现绿色建筑各种可持续发展的目标。基于此,麦格劳-希尔建筑公司对全美国483家建筑设计和施工企业对绿色BIM应用现状和未来趋势进行了相关的调研,并于2010年发表了此调研报告。该报告探讨了美国建筑公司在绿色项目中如何使用BIM技术以及如何籍此提高项目成果,检视了绿色BIM应用背后的驱动力以及公司采用绿色BIM相关工具的情况,以及对这些BIM工具的满意度。报告还对比绿色BIM公司和非绿色BIM公司之间的差异,并研究了非绿色BIM公司是怎样预计在他们在未来使用绿色BIM的情况,以及什么工具对他们来实现可持续发展目标是最有用处的。总之,该报告提供了一个视角来观察绿色建筑市场的不断增长是怎样如何推动绿色BIM成为在建筑行业中的一支重要力量。     

Use of reference states in predicting transport rates in high-speed turbulent flows with mass transfers

A method tor predicting mass-, momentum-, and energy-transfer rates in turbulent flows is outlined involving (a) a semi-empirical correlation of friction coefficient for injection of air into a low-speed air stream (providing the “constant-property” curve forming the heart of any attempt to predict transfer rates using reference states), (b) modified Reynolds analogies relating mass- and energytransfer coefficients with friction coefficient, and (c) expressions for reference temperature (or enthalpy) and reference composition. The blowing-rate parameter used in the friction-coefficient correlation differs from suggestions of earlier investigators using sublayer theories chiefly in that the geometric average of the friction factor with blowing and the friction factor without blowing is used. The modified Reynolds analogies differ from the analogies of Rubesin and Pappas chiefly in that the specific heat of the mixture is constant with value fixed by the reference state. Since, for flows without mass additions at the wall, the reference-temperature expression used for laminar flows correlates successfully the results for turbulent flows, attempts to correlate data for turbulent flows with mass additions using the reference-state expressions developed by Knuth for laminar flows with mass additions are recommended.

Since no data including dependable measurements of foreign-gas concentration at the surface are available, no verification of the modified Reynolds analogy relating mass and momentum transfer and of the use of the reference-concentration expression is possible at present. Limited available data indicate that (a) for Mach numbers up to 3, the reference-temperature expression developed for laminar flows with mass transfers appears to correlate satisfactorily the data for turbulent flows with mass transfers, and (b) use of the modified Reynolds analogy and the proposed blowingate parameter appears to correlate satisfactorily the skin-friction and heat-transfer data for the case in which the heat capacity of the coolant and main-stream gas are equal. The need for data which are more extensive and more accurate is emphasized.     

Effect of halogens on mercury conversion in SCR catalysts

The effect of halogen acids HCl, HBr and HI on mercury conversion was studied in a laboratory-scale SCR reactor using simulated flue gases, and is presented here. Two types of commercially available SCR catalysts, Honeycomb and Plate type catalysts, were used in these studies. HBr and HI both had shown much stronger effects on mercury conversion than HCl. Both HBr and HI oxidized more than 85% of the gas phase mercury at a low concentration of 2 ppm. The age of the catalyst and the type of catalyst also have an effect on mercury conversion. A larger extent of mercury oxidation was observed in the presence of a Honeycomb catalyst than with the Plate catalyst.