Stress relaxation in the interface between creep particle and elastic matrix-strengthening mechanism

The effect of a power law creep particle on interface behavior between the particle and elastic matrix is investigated by stress analysis. Using the results obtained through the stress analysis, the forces due to interaction of an applied stress and stress concentration with an edge dislocation are determined. The direct interaction between the edge dislocation and the creeping particle is studied under fully relaxed stress conditions. Through the investigation the following results are derived. Stress relaxation in the interface can be caused by power law creep along or by diffusion, or a combination of both mechanisms. The degree of stress relaxation caused by diffusion can be defined in terms of the relaxation time for both boundary diffusion and volume diffusion. The amount of stress relaxation caused by the power law creep particle is characterized by the quantity ₂ which is a function of Γ₀ = 2(1/√3)^{1 + m} × (σ_∞/2μ)^m(σ₀/σ_∞t^m), where m is strain rate hardening exponent, σ_∞ is applied stress, μ is the shear modulus, σ₀ is the material constant of the power law creep particle, and t is elapsed time. The value ₂ = 1.0 corresponds to the fully relaxed condition and ₂ = −0.6 corresponds to the initial state. The time to reach a fully relaxed condition is very sensitive to the strain rate exponent, with the smaller m values leading to longer times. The stress state of complete relaxation in the elastic matrix is equivalent to the solution of a void in an elastic matrix superposed on the solution of positive surface traction on the void. This result is identical to that obtained by Srolovitz et al. [Acta. Metall.32, 1979 (1984)]. When the stress is completely relaxed in the particle, all stress components (σ_r, σ_θand σ_rθ) are relaxed, while in the matrix relaxations are observed only for σ_rand σ_θ. The critical resolved shear stress and critical stress to climb the dislocation in the neighborhood of the particle exceed the Orowan stress. Also, the particle attracts the dislocation. Therefore the strengthening of a power law creep particle in an elastic matrix is caused by the Orowan mechanism and by attraction of the dislocation.     

Enhanced biodegradation of iopromide and trimethoprim in nitrifying activated sludge

Iopromide (an X-ray contrast agent) and trimethoprim (an antibacterial drug) are frequently detected pharmaceuticals in effluents of wastewater treatment plants (WWTPs) and in surface waters due to their persistence and high usage. Laboratory-scale experiments showed that a significantly higher removal rate in nitrifying activated sludge as compared to conventional activated sludge was observed for both iopromide and trimethoprim. When the activity of the nitrifying bacteria was inhibited, the percent removal of iopromide decreased from 97 to 86% while trimethoprim removal decreased from 70 to 25%. The metabolite of iopromide identified when nitrification was not inhibited was a dehydroxylated iopromide at the two side chains. However, when the nitrifying bacteria were inhibited the metabolite identified was a carboxylate, formed during the oxidation of the primary alcohol on the side chain of iopromide. These results suggest that the nitrifying bacteria are important in the observed biodegradation of iopromide in the activated sludge with higher solid retention time (SRT). Results from the laboratory-scale study were corroborated by the observed removal efficiencies in a full-scale municipal WWTP, which showed that iopromide (ranging from 0.10 to 0.27 microg/L) and trimethoprim (ranging from 0.0.08 to 0.53 microg/L) were removed more effectively in the nitrifying activate sludge which has a higher SRT (49 days) than in the conventional activated sludge (SRT of 6 days). In nitrifying activated sludge, the percent removal of iopromide in the WWTP reached 61%, while in conventional activated sludge, average removal was negligible. For trimethoprim, removal was limited to about 1% in the conventional activated sludge, while in the nitrifying activated sludge, the removal was increased to 50%.     

Interference effects between modes in open resonators

Interference effects between modes in open-resonators may seriously modify the resonance characteristics. Constructive and destructive interference may take place. For multimode conditions many path lengths exhibit resonance modification.     

Reference range and repeatability of a combined intestinal permeability and function test in clinically healthy Irish setter dogs

We investigated the influence of nutrition and exercise interventions within cognitive/behavioral and public health formats on weight and blood lipid profiles in obese children. Compliance was also examined as well as the relationship of the compliance measures with clinical outcome variables. Three conditions were compared over 16 sessions: nutrition and eating-habit change followed by exercise (NE), exercise followed by nutrition and eating-habit change (EN), and an information control (INFO). NE and EN were presented in a cognitive/ behavioral framework which focused on the development of self-regulation whereas the INFO condition received the same material in a public health/educational model. NE and EN participants evidenced modest, yet significant, reductions in weight and blood lipids, and the impact of these two interventions endured at a five-year follow-up. In contrast, INFO participants displayed stable weight and blood lipids during the course of the program, and most remained morbidly obese at follow-up. Improved nutrition, increased physical activity and fitness were significantly correlated with weight and lipid reductions.     

High-level expression of bovine beta-lactoglobulin in Pichia pastoris and characterization of its physical properties

Bovine beta-lactoglobulin (BLG) variant A has been expressed in the methylotropic yeast Pichia pastoris by fusion of the cDNA to the sequence coding for the alpha-mating factor prepro-leader peptide from Saccharomyces cerevisiae. P. pastoris Mut+ transformants were obtained by single cross-over integration of the BLG-containing vector into the AOX1 locus. In a fed-batch fermenter, a cell density of approximately 300 mg/ml was achieved by controlled glycerol feeding for a total of 24 h. After 72 h of methanol induction, the secreted BLG reached levels of > 1 g/l. The secreted protein could be purified to homogeneity by ion-exchange chromatography. Amino-terminal sequencing of the secreted BLG revealed that the Glu-Ala spacer repeats inserted between the mature protein and the alpha-factor prepro-leader were still present. The purified protein was characterized by a number of methods, including CD spectroscopy, guanidine-HCl unfolding, crystallization and two-dimensional 1H-NMR spectroscopy. By all of these measures, the physical characteristics of recombinant BLG were indistinguishable from those of the native purified bovine BLG, making it useful as a model for protein folding and other biophysical studies.     

Design and implementation of a strategy to reduce bacteriophage infection of dairy starter cultures

Bacteriophages can cause a significant economic loss for the dairy industry which uses lactic starter cultures to produce fermented dairy products including cheeses and yoghurt. Over the past 25 years, a number of different approaches have been explored and implemented to reduce the problems of bacteriophage infection in part through the development of bacteriophage resistant lactic acid starter culture strains. A strategy employing antisense RNA designed against essential bacteriophage replication functions has proven to be a unique system for engineering bacteriophage resistant Lactococcus lactis starter cultures. Resistance to a class of bacteriophages has been achieved, for example, by expression of an antisense RNA targeted against a conserved yet cryptic bacteriophage gene. This approach may prove useful for engineering a set of truly isogenic strains to be used in a starter culture rotation plan.     

Selectivity of anion exchange chromatography and capillary gel electrophoresis for the analysis of phosphorothioate oligonucleotides

The complementary nature of anion exchange chromatography and capillary gel electrophoresis for oligonucleotide analysis is demonstrated by evaluating a comprehensive series of authentic deletion sequences and partial phosphodiester analogs of five phosphorothioate oligonucleotides of different base composition and sequence. While anion exchange HPLC is sensitive to differences in backbone length of phosphorothioate oligonucleotides, oligomers with length difference of one base unit are not resolved. Capillary gel electrophoresis, on the other hand, has excellent single-base resolution while being relatively insensitive to phosphate in the phosphorothioate backbone. The data definitively establish the necessity of employing both separation techniques for adequate characterization of lower order process-related impurities potentially found in synthetic phosphorothioate oligonucleotides.     

The relationship between problem solving and activity level in the elderly

Research stemming from disengagement and activity theory has recently focused on individual differences in establishing and maintaining interpersonal relationships. A specific intervening variable which has been hypothesized to be related to social activity level is interpersonal cognitive problem solving skills (ICPS). The present study identified two groups of elderly veterans on the basis of their ICPS skills. Those who generated a high number of solutions to interpersonal problems reported significantly more time spent in social and isolated goal-directed tasks than the group generating fewer solutions when age, educational level, and length of institutionalization had been covaried. The results suggest the potential usefulness of the ICPS approach as a means of identifying socially active individuals and as an intervention or training technique for less able institutionalized residents.     

Open resonator operating at 337 ?m wavelength

Open-resonator techniques are investigated at the sub-millimetre wavelength of 337 ?m A folded spherical resonator with periodic variation of intermirror separation is excited at 33 ?m using an HCN laser. Initial results show that the theoretically expected form of resonance spectra can be obtained experimentally, and that the method should be applicable for dielectric-property and scattering-cross-section measurements in this wavelength range.     

Total body water volumes for adult males and females estimated from simple anthropometric measurements

Individual total body water volumes for 458 adult males and 265 adult females obtained from dilution studies, together with their height, weight, and age have been selected from the literature. These values were used to derive total body water prediction equations for adults of any age. The equations that gave the best fit were for males: formula (see text) and for females: formula (see text). Numerous other linear regression equations to predict total body water from anthropometric measurements have been reported in the literature. Most apply only to restricted age groups. These, and the equations from the present study were tested on completely independent data. In all cases the equations from the present study gave the best overall results, though for women one equation designed for a specific age group, gave for that age group a marginally better fit.