Influence of controlled fluid shear on nucleation rates in glycine aqueous solutions

The nucleation of glycine was investigated in supersaturated aqueous solutions exposed to well-controlled fluid shear under isothermal conditions. Shear rates between 25 s-1 and 1000 s-1 were studied using Couette and capillary flow devices. Induction times were obtained from imaging, transmission and scattering measurements, or visual monitoring. Great care was taken to eliminate any seeding in order to avoid secondary nucleation preceding formation of first crystals through primary nucleation. The observed induction times of sheared solutions were considerably lower than those of unsheared solutions. Increasing the average shear rate was found to reduce the mean induction time through a power law relationship. A detailed statistical analysis showed that the number of experimental repetitions used was sufficient to obtain statistically significant trends for the system studied. Induction times appeared to closely follow a probability distribution based on a previously published model of Jiang and ter Horst. Using their model, where the induction time is related to the rate of formation of primary nuclei and the time it takes them to grow to the size where the secondary nucleation becomes significant, it was found that both the primary nucleation rate and the growth time were strongly dependent on the shear rate imposed

Genetic Evolution of a Helicobacter pylori Acid-Sensing Histidine Kinase and Gastric Disease

Helicobacter pylori is the strongest risk factor for gastric adenocarcinoma, which develops within a hypochlorhydric environment. We sequentially isolated H. pylori (strain J99) from a patient who developed corpus-predominant gastritis and hypochlorhydia over a 6-year interval. Archival J99 survived significantly better under acidic conditions than recent J99 strains. H. pylori arsRS encodes a 2-component system critical for stress responses; recent J99 isolates harbored 2 nonsynonymous arsS mutations, and arsS inactivation abolished acid survival. In vivo, acid-resistant archival, but not recent J99, successfully colonized high-acid-secreting rodents. Thus, genetic evolution of arsS may influence progression to hypochlorhydia and gastric cancer

Physoxia Influences Global and Gene-Specific Methylation in Pluripotent Stem Cells

The work described in this paper was principally funded by the Iraqi Ministry of Higher Education and Scientific Research, University of Baghdad, RMKAJ (S1453), Baghdad, Iraq. We also wish to thank the Turkish Ministry of National Education for their support.Peer reviewedPublisher PD

Discriminating semi-continuous HMM for speaker verification

This paper describes the use of a multiple codebook SCHMM speaker verification system, which uses a novel technique for discriminative hidden Markov modelling known as discriminative observation probabilities (DOP). DOP can easily be added to a multiple codebook HMM system and require minimal additional computation and no additional training. The DOP technique can be applied to both speech and speaker recognition. Results are presented for text-dependent experiments on isolated digits from 27 true speakers and 84 casual imposters, recorded over the public telephone network in the United Kingdom. DOP are shown to significantly improve speaker verification performance for several commonly used parameter sets

Self-Presentational Determinants of Sex Differences in Leadership Behavior

Men and women placed in leadership positions communicated information about their skills and abilities to their subordinates. Although leaders’ perceptions of their abilities, group members’ knowledge of their leader’s abilities, and the specific skills needed by the leader were all manipulated in the experimental setting, self-presentations of ability were primarily determined by sex role stereotypes rather than by situational factors. Results indicated that (1) male leaders emphasized their social influence and task abilities; (2) female leaders emphasized their interpersonal, socioemotional abilities; and (3) group members felt task ability, as compared to interpersonal ability, was a far more important skill for a leader to possess. It was concluded that sex differences in male and female leadership behavior may be due to self-presentational conformity to sex roles, and that this conformity enhances males’ leadership effectiveness while detracting from females’ leadership effectiveness

Estimates of the impacts of invasive alien plants on water flows in South Africa

The adverse impacts of alien plant invasions on water flows have been a prime motivation for South Africa’s Working for Water Programme. The approach used in this study builds on a previous national assessment in 1998 by incorporating factors that limit plant water-use, information from recent research and improved flow reduction models. The total reduction in flows is estimated to be 1 444 million m3·yr−1 or 2.9% of the naturalised mean annual runoff (MAR), less than half of the 3 300 million m3·yr−1 estimated in 1998. Two main factors account for this difference: (a) a decrease in the estimated unit-area flow reduction to 970 m3·ha−1·yr−1 compared with 1 900 m3·ha−1·yr−1 estimated in 1998, largely due to the new model being based on more representative reduction factors; and (b) the updated estimate of the condensed invaded area of 1.50 million ha (previously 1.76 million ha), although the taxa mapped for this assessment only accounted for 1.00 million of the 1.76 million ha reported in 1998. Reductions due to invasions in Lesotho are estimated to be about 161 million m3·yr−1 and those in Swaziland about 193 million m3·yr−1. The taxon with the greatest estimated impact was wattles (Acacia mearnsii, A. dealbata, A. decurrens) with 34.0% of the total reductions, followed by Pinus species (19.3%) and Eucalyptus species (15.8%). The revised estimate is considered on the low side largely because the extent and impacts of riparian invasions have been underestimated. If the current estimates that 4–6% of Acacia mearnsii, Eucalyptus, Populus and Salix invasions are riparian, are adjusted to a more representative 20%, 50%, 80% and 80%, respectively, the total reductions increase by nearly 70% to ~2 444 million m3·yr−1. Producing these estimates involved a number of assumptions and extrapolations, and further research is needed to provide more robust estimates of the impacts.Keywords: plant water-use, flow reduction, mean annual runoff, riparian invasions, Working for Water Programm

Suppression of Integrin Activation: A Novel Function of a Ras/Raf-Initiated MAP Kinase Pathway

AbstractRapid modulation of ligand binding affinity (“activation”) is a central property of the integrin cell adhesion receptors. Using a screen for suppressors of integrin activation, we identified the small GTP-binding protein, H-Ras, and its effector kinase, Raf-1, as negative regulators of integrin activation. H-Ras inhibited the activation of integrins with three distinct α and β subunit cytoplasmic domains. Suppression was not associated with integrin phosphorylation and was independent of both mRNA transcription and protein synthesis. Furthermore, suppression correlated with activation of the ERK MAP kinase pathway. Thus, regulation of integrin affinity state is a novel, transcription-independent function of a Ras-linked MAP kinase pathway that may mediate a negative feedback loop in integrin function