Second-site suppressors of the bacteriophage P1 virs mutant reveal the interdependence of the c4, icd, and ant genes in the P1 immI operon

The immI operon of phage P1 contains the genes c4, icd, and ant, which are transcribed in that order from the same constitutive promoter, P51b. The gene c4 encodes an antisense RNA which inhibits the synthesis of an antirepressor by acting on a target ant mRNA. Interaction depends on the complementarity of two pairs of short sequences encompassing virs+ and the ribosome-binding site involved in ant expression. Accordingly, in a P1 virs mutant phage, antirepressor is synthesized constitutively. We have isolated lysogen-proficient, second-site suppressors of P1 virs in order to evaluate the interdependence of the immI-specific genes. From a total of 17 suppressors analyzed, 15 were found to be located in the icd gene. They were identified as frameshift mutations, containing base insertions or deletions in tandem repeats of a single base pair. One suppressor was identified as a P51b promoter-down mutation; the second site of another suppressor was found to be located in the c4 gene. Furthermore, it was shown that virs cannot be suppressed by ant (icd+) suppressors. The results confirm the model that the immI operon is transcribed as a unit, that the icd and ant genes are translationally coupled, and that the constitutive synthesis of Icd protein alone is lethal to the bacterial cell. The existence of a c4 suppressor of virs, whose effect is not yet known, points to a still more complex regulation of antirepressor synthesis than was anticipated from the model.     

Environmental assessment in early process development

A short‐cut method for environmental assessment during process development is presented. The method can deal with data uncertainties in early phases, includes all relevant environmental impacts, and is simple and easy to apply. Therefore, it can be used in early phases of process development. The environmental relevance of each substance is represented by the Environmental Factors. These factors are derived from 14 impact categories, where each compound is classified using an ABC methodology. The impact categories are then grouped into six impact groups: Resources, Grey Input, Component Risk, Organisms, Air and Water/Soil. From these, input and output environmental factors are deduced. This factor is combined with mass balance data to yield a number of indices that can be used to optimize the environmental performance of a process in an integrated manner. The method is applied to three case studies: a comparison of chemical and biotechnological production of 6‐aminopenicillanic acid, a comparison of two process alternatives in the enzymatic production of α‐cyclodextrin and the development of a new process for the fermentative production of pyruvate. Copyright © 2004 Society of Chemical Industry     

A reinvestigation of the thermal decomposition of aluminum carbide and the constitution of the Al-C system

The Al-C binary system was reinvestigated. Al₄C₃, the only intermediate phase, melts incongruently at 1990 ± 20 °C. The liquid dissolves up to -30 at % C and evaporates incongruently at 2250 ± 20 °C. The composition at which congruent vaporization occurs is close to Al₈₀C₂₀. The phase diagram is presented, and plausible reasons are suggested for the discrepancies in the literature.     

Indexing systematic rater agreement with a latent-class model.

A latent-class model of rater agreement is presented for which 1 of the model parameters can be interpreted as the proportion of systematic agreement. The latent classes of the model emerge from the factorial combination of the "true" category in which a target belongs and the ease with which raters are able to classify targets into the true category. Several constrained cases of the model are described, and the relations to other well-known agreement models and kappa-type summary coefficients are explained. The differential quality of the rating categories can be assessed on the basis of the model fit. The model is illustrated using data from diagnoses of psychiatric disorders and classifications of individuals in a persuasive communication study. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

A directed-graph classifier of semiconductor wafer-test patterns

A technique for training an expert system for semiconductor wafer fabrication process diagnosis is described. The technique partitions an existing set of electrically tested semiconductor wafers into groups so that all wafers within each group have similar spatial distributions of the electrical test data across selected die sites. The spatial distribution of test data from the selected die sites on each wafer is referred to as the test pattern of that wafer. A directed graph that is developed by the partitioning algorithm then efficiently classifies a new incoming wafer to one of the groups established during partitioning on the basis of its test pattern. The distribution of known processing histories of wafers within the group to which the new incoming wafer is classified provides a provisional diagnosis of the incoming wafer's process history     

Kinetic mechanism of Escherichia coli asparagine synthetase B

Escherichia coli asparagine synthetase B (AS-B) catalyzes the synthesis of asparagine from aspartate, glutamine, and ATP. A combination of kinetic, isotopic-labeling, and stoichiometry studies have been performed to define the nature of nitrogen transfer mediated by AS-B. The results of initial rate studies were consistent with initial binding and hydrolysis of glutamine to glutamate plus enzyme-bound ammonia. The initial velocity results were equally consistent with initial binding of ATP and aspartate prior to glutamine binding. However, product inhibition studies were only consistent with the latter pathway. Moreover, isotope-trapping studies confirmed that the enzyme-ATP-aspartate complex was kinetically competent. Studies using 18O-labeled aspartate were consistent with formation of a beta-aspartyl-AMP intermediate, and stoichiometry studies revealed that 1 equiv of this intermediate formed on the enzyme in the absence of a nitrogen source. Taken together, our results are most consistent with initial formation of beta -aspartyl-AMP intermediate prior to glutamine binding. This sequence leaves open many possibilities for the chemical mechanism of nitrogen transfer.     

用信息取代规制:寻找塑造城市设计的另一种方式

本文的写作目的既不是为了展示研究成果,也不是为了批评(或表扬)规制(regulation).我的目的是提出两个问题:有没有替代规制的可行方法?如果有,我们能在哪里找到模型?我建议通过关注一个领域来完成这个任务.     

Progress and needs in the experimental analysis of drug and alcohol dependence.

Examines the literature on drug dependence from a behavioral viewpoint. Dependence on drugs and alcohol results from an interaction between the individual and the substance within precipitating environmental conditions. Animals and humans self-administer the same drugs, suggesting the biological normality of chemical dependency and the value of laboratory research on the generation and alleviation of such dependencies. Functional or behavioral toxicity can be a serious social problem, and research is needed on why many individuals do not become addicted to drugs and alcohol to which they are exposed, and how social processes can be used to increase an individual's resistance to substance abuse. The cost effectiveness of drug research and treatment is also discussed. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Investigation of phase equilibria related to fusion reactor materials: II. The ternary system Hf-Al-N

Phase equilibria in the ternary system Hf-Al-N are investigated. At 1273 K, the ternary phase Hf₃AlN (isotypic with Zr₃AlN, monoclinic, a = 0.59011 nm, 6 = 0.88646 nm, c = 0.33185 nm, β = 106.33°) coexists with HfN_1−x, A1N, Hf₂Al₃, HfAl, Hf₄Al₃, Hf₃Al₃ and -Hf(s.s.). At 1673 K, a second ternary phase Hf₅Al₃N (isotypic with Zr₅Al₃N_1−x, hexagonal, a = 0.8062 nm, c = 0.5603 nm) occurs. A1N in contact with hafnium or hafnium-rich Hf-Al alloys decomposes at this temperature into HfN_1−x and HfAl₂. No ternary solubilities are observed further to the extended solid solutions of -Hf.