Frequency stabilization of a novel 1.5-μm Er-Yb bulk laser to a39K sub-Doppler line at 770.1 nm

The second harmonic output at 770.1 nm of a novel and compact Er-Yb:glass laser was frequency stabilized against the sub-Doppler linewidth of a crossover line in the ³⁹K 4S_1/2-4P _1/2 transition as obtained by saturation spectroscopy. Efficient frequency doubling, with a conversion efficiency of ~220% W ^-1, and with second harmonic power in excess of 15 μW, was achieved in a waveguide made in a periodically poled lithium niobate crystal. As measured through the analysis of the closed-loop error signal, a laser frequency instability of ~200 Hz was obtained; the Allan standard deviation of the frequency samples was below 4×10^-12 for integration times τ between 100 ms and 100 s, and reached a lowest floor level of 8×10^-13 for 20 s⩽τ⩽100 s. The measured frequency noise spectral density was in good agreement with the analysis performed in the time domain. Compared to previously published data for stabilized solid-state laser sources in this wavelength region, these results represent a significant improvement in the frequency stability     

Model demonstrating the potential for coupled nitrification denitrification in soil aggregates

A model of reactive, multi-species diffusion has been developed to describe N transformations in spherical soil aggregates, emphasizing the effects of irrigation with reclaimed wastewater. Oxygen demand for respiratory activity has been shown to promote the establishment of anaerobic conditions. Aggregate size and soil respiration rate were identified as the most significant parameters governing the existence and extent of the anaerobic volume in aggregates. The inclusion of kinetic models describing mineralization, nitrification, and denitrification facilitated the investigation of coupled nitrification/denitrification (CND), subject to O2 availability. N-transformations are shown to be affected by effluent-borne NH4+-N content, in addition to elevated BOD and pH levels. Their incremental contribution to O2 availability has been found to be secondary to respiratory activity. At the aggregate level, significant differences between apparent and gross rates of N-transformations were predicted (e.g., NH4+ oxidation and N2 formation), resulting from diffusive constraints due to aggregate size. With increasing anaerobic volume, the effective nitrification rate determined at the aggregates level decreases until its contribution to nitrification is negligible. It was found that the nitrification process was predominantly limited to aggregates <0.25 cm. Assuming that nitrification is the main source for NO3- formation, denitrification efficiency is predicted to peak in medium-sized aggregates, where aerobic and anaerobic conditions coexist, supporting CND. In effluent-irrigated soils, the predicted NO2- formation rate in small aggregates is enhanced when compared to freshwater-irrigated soils. The difference vanishes with increasing aggregate size as anaerobic NO2- consumption exceeds aerobic NO2- formation due to the coupling of nitrification and denitrification.     

Fine-tuning Food Safety Objectives and risk assessment

Food Safety Objectives (FSOs) have been proposed as a practical tool to translate public health targets for food safety into tolerable levels of pathogens in a food product. The FSO concept is subject to intensive debate, and has not been developed in detail. We evaluate the proposed definition of FSOs and their implementation from the perspective of Quantitative Microbiological Risk Assessment (QMRA). The relationship between QMRA and FSOs is illustrated by a model for the public health risk of Shiga-producing Escherichia coli in steak tartare. We conclude that the proposed definition of FSOs needs to be modified to properly account for variability in and uncertainty about the contamination of food with pathogenic microorganisms and emphasize that both prevalence and concentration of pathogens must be considered. For this purpose, we propose the P-D equivalence curve, a simple graphical tool to separate "tolerable" from "non-tolerable" combinations of prevalence and concentration (dose).     

HXT5 expression is determined by growth rates in Saccharomyces cerevisiae

In the yeast Saccharomyces cerevisiae, hexose transporter (Hxt) proteins transport glucose across the plasma membrane. The Hxt proteins are encoded by a multigene family with 20 members, of which Hxt1-4p and Hxt6-7p are the major hexose transporters. The remaining Hxt proteins have other or unknown functions. In this study, expression of HXT5 under different experimental set-ups is determined. In glucose-grown batch cultures, HXT5 is expressed prior to glucose depletion. Independent of the carbon source used in batch cultures, HXT5 is expressed after 24 h of growth and during growth on ethanol or glycerol, which indicates that growth on glucose is not necessary for expression of HXT5. Increasing the temperature or osmolarity of the growth medium also induces expression of HXT5. In fed-batch cultures, expression of HXT5 is only observed at low glucose consumption rates, independent of the extracellular glucose concentration. The only common parameter in these experiments is that an increase of HXT5 expression is accompanied by a decrease of the growth rate of cells. To determine whether HXT5 expression is determined by the growth rate, cells were grown in a nitrogen-limited continuous culture, which enables modulation of only the growth rate of cells. Indeed, HXT5 is expressed only at low dilution rates. Therefore, our results indicate that expression of HXT5 is regulated by growth rates of cells, rather than by extracellular glucose concentrations, as is the case for the major HXTs. A possible function for Hxt5p and factors responsible for increased expression of HXT5 upon low growth rates is discussed.     

Forty years later: Long-term consequences of massive traumatization as manifested by Holocaust survivors from the city and the Kibbutz.

The present study explored the differences between male and female Holocaust survivors (n?=?34) who were similar to the survivors but had not been victims of the Holocaust. Half of the respondents were from the city and the other half were from the Kibbutz. The main dependent measures included the CAQ, the TSCS, and a specially designed Centrality of Family scale. Survivors were worse off psychologically than comparison individuals on the quality of emotional life, on emotional expression, and on the quality of interpersonal relations. Also, survivors assigned relatively greater value to their postwar families. City survivors seem to be worse off than Kibbutz survivors, and male survivors from the city had the lowest scores on several key subscales. These data were corroborated and extended by a content analysis of an open-ended interview conducted after the objective measures had been completed. The findings and their implications for understanding the effects of massive traumatization over individuals' life cycles are discussed. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Burnout and risk of cardiovascular disease: Evidence, possible causal paths, and promising research directions.

Burnout is characterized by emotional exhaustion, physical fatigue, and cognitive weariness, resulting from prolonged exposure to work-related stress. The authors review the accumulated evidence suggesting that burnout and the related concept of vital exhaustion are associated with increased risk of cardiovascular disease and cardiovascular-related events. The authors present evidence supporting several potential mechanisms linking burnout with ill health, including the metabolic syndrome, dysregulation of the hypothalamic-pituitary-adrenal axis along with sympathetic nervous system activation, sleep disturbances, systemic inflammation, impaired immunity functions, blood coagulation and fibrinolysis, and poor health behaviors. The association of burnout and vital exhaustion with these disease mediators suggests that their impact on health may be more extensive than currently indicated. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

The CUBE workstation —a 3-D voxel-based graphics environment

TheCUBE workstation is a 3-D versatile graphics system centered around a largecubic frame-buffer ofvoxels. A softwarebased prototype has been integrated on a SUN workstation with a 6-D Polhemus input device. The user interacts directly with the geometric objects and the voxel images, employing inherent 3-D interactive tools. A reduced-resolution hardware prototype has been built and has been running in real-time. The cubic frame buffer is uniquely organized for parallel beam access by three processors which input sampled and synthetic images, manipulate, project, and render them. Projections are speeded-up by a special bus which selects along a beam in onlylog time.This work was supported by the National Science Foundation under grant DCR-86-03603     

When opportunity knocks: Bottom-up priming of goals by means and its effects on self-regulation.

Four studies using general attribute goals or specific task goals revealed that attainment means cognitively activate the goals they are perceived to serve. A range of means replicated this effect including goal-directed activities, specific behavioral strategies, or opportunities, assumed to afford effective goal pursuit. The increased accessibility of a currently pursued goal due to "bottom-up" priming by its attainment means improved task persistence and performance, whereas a similarly increased accessibility of a competing goal impeded task persistence and performance. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Certification of NIST SRM 1962: 3 μm Diameter Polystyrene Spheres

This report describes the certification of SRM 1962, a NIST Standard Reference Material for particle diameter. It consists of an aqueous suspension of monosize 3 (μm polystyrene spheres. Two calibration techniques were used: optical microscopy and electron microscopy. The first one gave a mean diameter of D¯=2.977±0.011 μm and a standard deviation of the size distribution σ_D = 0.020 μm, based on measurement of 4600 spheres. The second technique gave D¯=2.990±0.009 μm, based on measurement of 120 spheres. The reported value covering the two results is D¯=2.983 μm with a maximum uncertainly of 0.016 μm, with σ_D=0.020 μm.