Stereochemistry of cytochrome P-450-catalyzed epoxidation and prosthetic heme alkylation

Oxidation of 1-octene by cytochrome P-450 results concurrently in formation of 1,2-oxidooctane and in N-alkylation by the catalytically activated olefin of the prosthetic heme group. The stereochemistry of trans-1-[1-2H]octene is retained during both transformations. This alkylation stereochemistry requires addition of the pyrrole nitrogen and the activated oxygen to the same side of the double bond, a reaction geometry opposite to that expected if the heme were alkylated by the epoxide metabolite. Stereochemical analysis shows that the S enantiomer of the epoxide is formed in slight excess over the R enantiomer by oxidation of the re and si faces, respectively, of the olefin, but that heme alkylation only occurs during oxidation of the re face. The stereochemical specificity of epoxidation and heme alkylation requires that (a) the two processes proceed by independent (probably concerted) mechanisms, or (b) the two processes diverge from a common acyclic intermediate.     

Licensure requirements: Have we raised the bar too far?

How do the requirements for entering the profession of psychology compare with those for other professions? Differences in licensure and board certification requirements were examined across 13 professions. Median earnings and the amount of time to complete requirements were compared. Findings indicate that practicing psychologists have a protracted period of preparation coupled with incomes that are not commensurate with training. In order to thrive, the field of psychology must reexamine and redefine credentialing requirements, reengineer curricula for doctoral programs, standardize licensure requirements across states, and broaden career options beyond academia and mental health. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

The recycle of sulfuric acid and xylose in the prehydrolysis of corn stover

Ethanol may be produced from agricultural residues by using a two-stage acid hydrolysis followed by acid recovery, fermentation, and distillation. With sulfuric acid as a catalyst, xylose-rich and glucose-rich streams can be obtained from corn stover in the prehydrolysis and hydrolysis steps, respectively. After acid separation, the sugar solutions are fermented to ethanol and concentrated by distillation.The acid recovery and distillation steps are the most expensive portions of the process; therefore, any reduction in the requirements for these steps will significantly improve the economics of the overall process. One means by which this may be accomplished is the addition of a recycle stream in the prehydrolysis step. The result will be an increased xylose concentration in the the prehydrolyzate fluid, which will reduce the acid recovery and distillation costs for each unit of ethanol produced. Thus, both capital and operating costs can be lowered while the net energy production is increased.In this investigation, the prehydrolysis step was carried out in a batch reactor at a temperature of 100 °C and a reaction time of 80 min. A 2-1. reaction vessel was used for the first two batches, each of which resulted in approx. 600 milliliters (ml) of prehydrolyzate fluid. This fluid, consisting primarily of xylose dissolved in the dilute sulfuric acid solution, was then mixed in varying ratios with fresh acid and used as the acid catalyst in later experiments to determine the effects of recycle on sulfuric acid activity and xylose concentration. In one set of recycle experiments, the activity of the recycled acid was as much as 90% of the activity of fresh acid on a volume per volume basis. Because the recycled fluid contained approx. 3% xylose, the xylose concentrations obtained in these experiments depended on the ratio of recycled acid to fresh acid. Concentrations averaged 27.5 grams per liter (g/l) for an acid residence time of 80min and 51.4 g/l for an acid residence time of 160 min.The effect of the increased concentration of xylose on the economics of a 4.5 × 10⁶ gallon per year ethanol plant were estimated to be a 16% reduction in capital costs and a 17% reduction in operating costs. For corn stalks at $25 per ton and ethanol at $1.185 per gallon (ga), the estimated rate of return on investment would increase from 3.4% without recycle to 18.0% with recycle.     

Beeinflussung des Schwingungsrißkorrosions-Verhaltens verschweißter Proben durch das WIG- und Plasmanachbehandlungsverfahren

Influence of TIG- and plasma post-weld treatment on corrosion fatigue behaviour of welded specimens It has been proven that the treatment of welded seams with the aid of dressing can clearly increase the fatigue performance of welded constructions. In order to determine how the same treatment affects structures, which are subject to corrosion fatigue, welded specimens of EH 36 ship steel were made. TIG and Plasma dressings were used to remelt the transient zone of the weld. The fatigue behaviour of the specimens in air and artificial seawater was examined in comparison to specimens which had not been treated. The optimal parameters for these post-weld heat treatments were determined. The influence of the dressing methods was examined in dynamic and combined dynamic-corrosive tests. Parallel to these hardness-measurements, electrochemical and fractographic tests were also done. The effects of the dressings in constant amplitude corrosion fatigue tests were compared to corrosion fatigue behaviour under random loading. There is only little comparability between the results of the random loading tests and these of the constant amplitude tests. The results of this research show that the positive effect of the dressing methods on only dynamically tested structures is much better than under combined dynamic-corrosive loading. This is clearly due to the fact that the corrosion behaviour of the specimens cannot be influenced in the same way as the fatigue performance. If the corrosive effect is reduced by means of protective methods an increase in the effect of the dressing methods can be expected.     

Axial imaging necessitates loss of lateral shift invariance

We conjecture that the lateral shift invariance of an imaging system must be limited if axial imaging capability is desired. We develop shift-invariance and depth-resolution metrics and demonstrate the trade-off in simple representative systems.     

Nuclear Data Sheets for A = 159

The experimental results available through September 1978 from the various reaction and decay studies leading to nuclides in the A = 159 mass chain have been reviewed. These data are summarized and presented, together with the adopted level schemes and properties.     

An information integration analysis of retail store image.

The process whereby judges form images of retail stores was analyzed with an information integration approach and functional measurement methodology. The study, which involved 59 university students, sought to determine how 4 factors of image information (kind of store, location, price, and clientele) were combined into a resultant image. Dependent variables concerned the Ss' favorability judgments of the stores and their behavioral intentions to shop there. Results show unequal weighting of information and interactions among image attributes. Results are discussed in terms of the usefulness of the information integration approach for owners and advertisers in their attempts to create optimal store images. (15 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Life events and personal causation: Some relationships with satisfaction and distress.

Hypothesized that Ss who engaged in more positive origin activities would rate their lives as more satisfying than Ss who engaged in fewer such activities, and both would be more satisfied than control Ss. After completing a series of questionnaires including a life-event inventory, 3 groups of college students were selected from a pool of 141 and given instructions either to (a) engage in 12 activities from a self-selected list of pleasurable activities, (b) engage in 2 activities from that list, or (c) return after 1 mo for retesting only. Ss were then given a pleasantness-of-events test, an event-frequency test, the Perceived Quality of Life Scale, the Beck Depression Inventory, and a 54-item Symptom Check List. Covariance analyses revealed that Ss instructed to engage in either 2 or 12 pleasurable activities reported greater pleasantness and a higher quality of life than controls; there were no differences between groups on reports of psychiatric distress. Prior negative life change was treated as a factor in the design and was found to interact with the activity instructions: Ss reporting many prior negative changes exhibited less psychiatric distress along with greater pleasantness when instructed to engage in 12 activities rather than 2 or none. Results suggest that pleasant activities increase positive aspects of well-being in general, but may reduce distress only for people experiencing considerable life stress. (28 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Monodisperse polymeric spheres in the micron size range by a single step process

A method for the formation of monodisperse polystyrene (PS) and polymethylmethacrylate (PMMA) spheres, in the micron diameter range, was developed. The polymerisation reaction was carried out in a series of alcohols, using homo- and co-polymers as steric stabilisers in combination with a quaternary ammonium salt which probably acts as an electrostatic co-stabiliser. Monodisperse PS spheres were formed in the particle size range of 1–6 μm, by a single step process. The size range could be extended by further addition of monomer to the reaction mixture during the polymerisation. The solubility parameter of the alcohol used and the nature of the surfactant determine the diameter of the resulting spheres. However, the concentration of surfactant did not seem to affect strongly the size of the spheres but only the dispersity.