Interactive Dynamics of Cell Volume and Cell Death in Human Erythrocytes Exposed to α-Hemolysin from Escherichia coli

α-hemolysin (HlyA) of E. coli binds irreversibly to human erythrocytes and induces cell swelling, ultimately leading to hemolysis. We characterized the mechanism involved in water transport induced by HlyA and analyzed how swelling and hemolysis might be coupled. Osmotic water permeability (P_f) was assessed by stopped-flow light scattering. Preincubation with HlyA strongly reduced P_f in control- and aquaporin 1-null red blood cells, although the relative P_f decrease was similar in both cell types. The dynamics of cell volume and hemolysis on RBCs was assessed by electrical impedance, light dispersion and hemoglobin release. Results show that HlyA induced erythrocyte swelling, which is enhanced by purinergic signaling, and is coupled to osmotic hemolysis. We propose a mathematical model of HlyA activity where the kinetics of cell volume and hemolysis in human erythrocytes depend on the flux of osmolytes across the membrane, and on the maximum volume that these cells can tolerate. Our results provide new insights for understanding signaling and cytotoxicity mediated by HlyA in erythrocytes.     

Concentration quenching of Tb3+ luminescence in LaOBr and Gd2O2S phosphors

The concentration quenching of trivalent terbium ${}^5\text{D}{}_{\mathrm{3,4}}\text{→}{}^7\text{F}{}_{\mathrm{J}}$ emissions from UV-excited (La, Tb) OBr and (Gd, Tb)₂O₂S phosphors was studied. The activation concentration x was varied from 5·10^?5 to 0.2 for (La_1?xTb_x) OBr and from 10^?3 to 0.1 for (Gd_1?xTb_x)₂O₂S. ${}^5\text{D}{}_3\text{→}{}^7\text{F}{}_{\mathrm{J}}$ emissions (blue) were observed to quench first and the Tb³⁺ concentration giving rise to maximum intensity was 0.003 in (La, Tb) OBr and between 0.005 and 0.01 in (Gd, Tb)₂O₂S. The optimum concentration for ${}^5\text{D}{}_4\text{→}{}^7\text{F}{}_{\mathrm{J}}$ (green) emissions was 0.05 in (La, Tb) OBr and 0.03 in (Gd, Tb)₂O₂S. Dipole-dipole and dipole-quadrupole interactions are possible mechanisms for the quenching of emissions from the ⁵D₃ and ⁵D₄ levels.A method for determining the Tb³⁺ concentration in these phosphors, based on the intensity ratios of the ${}^5\text{D}{}_3\text{→}{}^7\text{F}{}_{\mathrm{J}}$ and ${}^5\text{D}{}_4\text{→}{}^7\text{F}{}_{\mathrm{J}}$ transitions, is also presented.     

Intrauterine ectopic pregnancy. A case report

Ratings and tests for the effectiveness of sunscreens are becoming more consistent and scientifically based. This reflects the growing recognition of the health hazards from sunburn and excessive tanning. Health professionals should be aware of the classic six skin types and their susceptibility to burning. As well as Sun Protection Factors (SPFs), long-wave ultra-violet radiation needs to be taken into account. UVA rays cause long-term damage to the skin. No agreed test for UVA protection exists as yet, but some manufacturers have introduced a star rating system for UVA protection. The more UVA stars, the greater the protection. Children's skin is more vulnerable to burning so they need special protection and a high SPF and UVA rating. The first line of defence is avoiding strong sunlight and covering the head and body. Remember that sunscreens need reapplying after swimming. Always follow the manufacturers' directions carefully.     

Development of crystallinity and morphology in hafnium dioxide thin films grown by atomic layer epitaxy

The structural development of HfO₂ thin films grown from HfCl₄ and water onto glass substrates by atomic layer epitaxy at 500 °C was studied with X-ray diffraction, atomic force microscopy and scanning electron microscopy. The films were found to contain two regions of different crystallinity: a thin amorphous starting layer and a subsequent preferentially oriented polycrystalline layer. The films were built up of densely packed grains. Substantial surface roughening occurred along with increasing film thickness. The films were chlorine free as analyzed by Rutherford backscattering spectrometry.     

Mechanical exposure implications of rationalization: a comparison of two flow strategies in a Swedish manufacturing plant

The aim of this case study was to (1) investigate differences in mechanical exposure (i.e. mechanical forces arising in the body of the operator) between two production strategies: long-cycle parallelised flow assembly (OLD) and conventional serial flow assembly (NEW), and (2) estimate potential changes in job exposure as a consequence of waste reduction when rationalising a line system. Data on postures, movements and whole body exposure were collected during an ordinary working shift, by means of video recordings synchronised to direct technical measurements of six professional operators. The results revealed the machine paced NEW system to have slower movements with less time spent in movements of high velocity compared to the self-paced OLD system. No significant differences were found between time-median posture levels. 'Disturbances' in the NEW system offered lower mechanical risk exposures compared to direct assembly work. Modelling the removal of wasteful 'disturbances' revealed both an increase in risk-implying fast movements and decrease in recovery-implying periods at low velocity - effectively isolating a work intensification. This study helps expose the complex relationship between rationalizations and mechanical exposure for system operators.     

Modelling lidar-derived boreal forest canopy cover with SPOT 4 HRVIR data

Forest canopy cover (C) is needed in forest area monitoring and for many ecological models. Airborne scanning lidar sensors can produce fairly accurate C estimates even without field training data. However, optical satellite images are more cost-efficient for large area inventories. Our objective was to use airborne lidar data to obtain accurate estimates of C for a set of sample plots in a boreal forest and to generalize C for a large area using a satellite image. The normalized difference vegetation index (NDVI) and reduced simple ratio (RSR) were calculated from the satellite image and used as predictors in the regressions. RSR, which combines information from the red, near-infrared, and shortwave infrared bands, provided the best performance in terms of absolute root mean square error (RMSE) (7.3%) in the training data. NDVI produced a markedly larger RMSE (10.0%). However, in an independent validation data set, RMSE increased (13.0–17.1%) because the systematic sample of validation plots contained more variation than the training plots. Our results are better than those reported earlier, which is probably explained by more consistent C estimates derived from the lidar. Our approach provides an efficient method for creating C maps for large areas.