Strain energy distribution in a crack-tip region in random fiber networks

A closed form relation for the strain energy density in the vicinity of a macroscopic mode I crack in a random fiber network is derived using an implicit gradient nonlocal continuum field theory. An expression for the characteristic length, used in the nonlocal formulations, in terms of microstructural properties is derived and it is found that the characteristic length is proportional to the average fiber segment length to the power of two. It is illustrated that the crack-tip singularity vanishes for a characteristic length greater than zero. An open fiber structure exhibits a distributed strain energy field in the crack tip vicinity. As the network becomes relatively denser, the characteristic length decreases and the networks mechanical behavior approaches the behavior of a classic elastic continuum. Only for an infinitely dense network is the r ⁻¹-singularity in strain energy field achieved. The theory explains why open network structures have difficulties in localizing failure to macroscopic cracks. It is found that there is a one-to-one relation between characteristic length and size of the smallest crack that can initiate macroscopic failure.     

Accurate wavelength measurements of a putative standard for near-infrared diffuse reflection spectrometry

The diffuse reflection (DR) spectrum of a sample consisting of a mixture of rare earth oxides and talc was measured at 2 cm-1 resolution, using five different accessories installed on five different Fourier transform near-infrared (FT-NIR) spectrometers from four manufacturers. Peak positions for 37 peaks were determined using two peak-picking algorithms: center-of-mass and polynomial fitting. The wavenumber of the band center reported by either of these techniques was sensitive to the slope of the baseline, and so the baseline of the spectra was corrected using either a polynomial fit or conversion to the second derivative. Significantly different results were obtained with one combination of spectrometer and accessory than the others. Apparently, the beam path through the interferometer and DR accessory was different for this accessory than for any of the other measurements, causing a severe degradation of the resolution. Spectra measured on this instrument were removed as outliers. For measurements made on FT-NIR spectrometers, it is shown that it is important to check the resolution at which the spectrum has been measured using lines in the vibration-rotation spectrum of atmospheric water vapor and to specify the peak-picking and baseline-correction algorithms that are used to process the measured spectra. The variance between the results given by the four different methods of peak-picking and baseline correction was substantially larger than the variance between the remaining five measurements. Certain bands were found to be more suitable than others for use as wavelength standards. A band at 5943.13 cm-1 (1682.62 nm) was found to be the most stable band between the four methods and the six measurements. A band at 5177.04 cm-1 (1931.61 nm) has the highest precision between different measurements when polynomial baseline correction and polynomial peak-picking algorithms are used.     

Patch testing with budesonide in serial dilutions: the significance of dose, occlusion time and reading time

Dipeptide transporters in small intestine have a very wide substrate specificity, so that the transporter sometimes serves as a carrier for peptide-like compounds. We have synthesized dipeptide analogues conjugated at an epsilon-amino group of Lys in Val-Lys or Lys-Sar with fluorescent compounds such as fluorescein isothiocyanate and coumarin-3-carboxylic acid. Uptakes of these peptide analogues were examined by measuring intracellular accumulations into monolayers of the human intestinal epithelial cell line Caco-2 expressing the dipeptide transporter PEPT1. Kinetic analysis and effects of addition either of uncoupler (protonophore) or by Gly-Sar, one of the good substrates of PEPT1, revealed that fluorescent dipeptides were taken up by passive diffusion. In contrast, these analogues remarkably inhibited the Gly-Sar uptake by Caco-2 cells. Among the fluorescent analogues synthesized in this paper, Val-Lys(Flu) was the most potent competitive inhibitor against the Gly-Sar uptake with an inhibition constant of 5 microM. This value is the smallest among those ever reported: Val-Lys(Flu) has the highest affinity for PEPT1 among chemicals ever reported. The importance of the hydrophobic part of the substrate was pointed out.     

Technical note: Comparing calibration methods for determination of protein in goat milk by ultraviolet spectroscopy

A rapid spectroscopic method to determine total protein in bovine and buffalo milk using UV spectra of guanidine-hydrochloride mixed milk has previously been reported and validated. The method was based on mixed calibration samples and univariate calibrations of fourth derivative (4D) spectra. In this study the same method was compared and tested for determination of total protein in goat milk. Calculations based on multivariate calibration (partial least squares regression) on full spectra of goat milk were used. The method was tested on 2 UV instruments. The comparison resulted in a significantly more robust (i.e., better) transferability between UV instruments for the partial least squares regression method on full spectra compared with previous univariate calibration of 4D spectra. Local (1 instrument) calibrations gave similar, significantly not different (chi-squared test) cross-validated prediction error results for the 2 methods. It can be concluded that there is no need for fourth derivation. Partial least squares regression on full spectra was equal or superior to using the 4D spectra.     

Critical conditions for onset of mould growth under varying climate conditions

A performance-based service life design format based on climatic exposure on one hand and “resistance” of materials against mould growth on the other hand, is presented in this paper. A limit state for onset of mould growth is defined as the occurrence of traces of mould observed by microscopy. A dose–response model is proposed by which onset of mould growth can be predicted for an arbitrary climate history of combined relative humidity ? and temperature T. The model is calibrated and verified against a comprehensive set of experimental data published by Viitanen et al. [Viitanen H, Ritschkoff A-C. Mould growth in pine and spruce sapwood in relation to air humidity and temperature. Uppsala: Swedish University of Agricultural Sciences, Department of Forest Products; 1991. Report No. 221, 49 p.; Viitanen H. Modelling the time factor in the development of mould fungi – effect of critical humidity and temperature conditions in pine and spruce sapwood. Holzforschung 1997;51(1):6–14; Viitanen H. Modelling the time factor in the development of brown rot decay in pine and spruce sapwood – the effect of critical humidity and temperature conditions. Holzforschung 1997;51(2):99–106; Viitanen H, Bjurman J. Mould growth on wood under fluctuating humidity conditions. Material und Organismen 1995;29(1):27–46] describing mould development on spruce and pine sapwood as a function of climatic exposure. The model is applied to predict time to onset of mould growth under natural outdoor climate (under shelter) as well as mould development in building attics and in crawl space foundations. The predicted response shows reasonable agreement with experimental observations and proven experience, although biological processes of this type display great variability. The results show that a generally applicable, quantitative model can be used as a powerful tool for moisture safe design in practice. The model is designed to facilitate continuous improvement of prediction capability by further laboratory testing of various materials under specified climate conditions. In combination with currently available building physics software the model is suitable for moisture safe design of wood-based components in the building envelope.     

Well-being and organizational attitudes in alternative employment: The role of contract and job preferences.

This study focuses upon the heterogeneity in the contemporary workforce in relation to well-being and organizational attitudes. This heterogeneity may concern (a) the specific type of contract (permanent full-time vs. alternative arrangements; e.g., permanent part-time, fixed-term, and on-call work), (b) job and contract preferences, or (c) specific combinations of contract type and preferences. The authors argue that working in alternative employment, but also being in a nonpreferred contract or job may imply stress and, hence, strain (i.e., poor well-being). This may lead to withdrawal from the organization (i.e., poor organizational attitudes). A combination of the stressors may strengthen these effects. Analyses of questionnaire data from Sweden collected in 2004 (N = 716) reveal that preferences, particularly preferences for the job and partly also for the contract, were associated with the outcomes. Contract heterogeneity was not informative for well-being, while it was for differences in reported organizational attitudes. Type of employment contract interacted with job and contract preferences: for permanent full-time workers, job preferences displayed stronger associations with well-being and attitudes than for workers in alternative employment. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Mesocaval interposition shunting in the treatment of bleeding oesophageal varices

OBJECTIVE: To assess the longterm results of mesocaval interposition shunt in the treatment of bleeding oesophageal varices. DESIGN: Retrospective study. SETTING: University hospital, Sweden. SUBJECTS: 60 patients with bleeding oesophageal varices in all Child's classes. 20 of whom were operated on as emergencies, and 40 as elective cases. INTERVENTIONS: A 14 mm polytetrafluoroethylene graft was used as an interposition shunt between the superior mesenteric vein and the vena cava. MAIN OUTCOME MEASURES: Rebleeding rate, portal blood flow, hepatic encephalopathy, morbidity, mortality, and survival. RESULTS: Rebleeding was rare and occurred mainly during the first 4 months after operation, (n = 5) in 10% of the patients, and at the 24 month follow-up, (n = 4) in 11% of the patients. Portal flow was measured preoperatively in 33 patients and in 22 (67%) it was hepatopetal. During follow-up it was reversed and after 24 months no patient had hepatopetal flow. Hepatic encephalopathy was present in 18 patients (20%) during follow-up. Shunts thrombosed in 9 patients (15%), 8 of which required reoperation. There was no operative mortality, but 4 patients (7%) died within 30 days of surgery. The main late cause of death (18/26) was liver failure. The 1 year survival was 80%, the 3 year survival 70% and the 5 year survival 60%. CONCLUSIONS: The mesocaval interposition shunt gives good longterm results and can be recommended both as an emergency and an elective procedure for patients with portal hypertension and bleeding oesophageal varices that are unresponsive to sclerotherapy.     

Prediction of sensory quality by near infrared reflectance analysis of frozen and freeze dried green peas (Pisum sativum)

Frozen, green peas (Pisum sativum L ) of different varieties and different levels of maturity were evaluated by sensory analysis using a panel of ten trained judges. Two texture variables (hardness and mealiness) and four flavour variables (pea flavour, sweetness, fruity flavour, off flavour) were considered. Near infiared reflectance ( N I R ) analysis was performed with the same material, on both the fiozen and fieeze dried peas. The N I R instrument was calibrated to predict the sensory variables using the multivariate analytical method of principal component regression. Tenderometer readings of the same peas were also calibrated to predict the sensory variables. N I R analysis on the fieeze dried peas showed relative ability of prediction (RAP) values for the sensory variables which were higher than those for the tenderometer readings. The sensory attributes pea flavour and hardness were predicted with higher RAP values by tenderometer readings than by N I R analysis on fiozen peas. For the rest of the attributes, N I R analysis on fiozen peas gave higher RAP values than tenderometer readings. N I R generally gave high RAP values, and this tentative study suggests that N I R analysis could be a useful tool in instrumentally assessing the quality of frozen peas.