Shear stress and sediment transport calculations for sheet flow under waves

A simple method is provided for calculating transport rates of not too fine (d(50) greater than or equal to 0.20 mm) sand under sheet flow conditions. The method consists of a Meyer-Peter-type transport formula operating on a time-varying Shields parameter, which accounts for both acceleration-asymmetry and boundary layer streaming. While velocity moment formulae, e.g.., = Constant x calibrated against U-tube measurements, fail spectacularly under some real waves (Ribberink, J.S., Dohmen-Janssen, C.M., Hanes, D.M., McLean, S.R., Vincent, C., 2000. Near-bed sand transport mechanisms under waves. Proc. 27th Int. Conf. Coastal Engineering, Sydney, ASCE, New York, pp. 3263-3276, Fig. 12), the new method predicts the real wave observations equally well. The reason that the velocity moment formulae fail under these waves is partly the presence of boundary layer streaming and partly the saw-tooth asymmetry, i.e., the front of the waves being steeper than the back. Waves with saw-tooth asymmetry may generate a net landward sediment transport even if = 0, because of the more abrupt acceleration under the steep front. More abrupt accelerations are associated with thinner boundary layers and greater pressure gradients for a given velocity magnitude. The two real wave effects are incorporated in a model of the form Q(s)(t) = Q(s)[theta(t)] rather than Q(S)(t) = Q(S)[u(infinity)(t)], i.e., by expressing the transport rate in terms of an instantaneous Shields parameter rather than in terms of the free stream velocity, and accounting for both streaming and accelerations in the 0(t) calculations. The instantaneous friction velocities u(*)(t) and subsequently theta(t) are calculated as follows. Firstly, a linear filter incorporating the grain roughness friction factor f(2.5) and a phase angle phi(tau) is applied to u(infinity)(t). This delivers u(*)(t) which is used to calculate an instantaneous grain roughness Shields parameter theta(2.5)(t). Secondly, a constant bed shear stress is added which corresponds to the streaming related bed shear stress -rho ($) over bar((u) over tilde(w) over tilde)(infinity) . The method can be applied to any u(infinity)(t) time series, but further experimental validation is recommended before application to conditions that differ strongly from the ones considered below. The method is not recommended for rippled beds or for sheet flow with typical prototype wave periods and d(50) < 0.20 turn. In such scenarios, time lags related to vertical sediment movement become important, and these are not considered by the present model. (C) 2002 Elsevier Science B.V. All rights reserved.

Refinements in stress echocardiographic techniques improve inter-institutional agreement in interpretation of dobutamine stress echocardiograms

Aims To determine the degree of inter-institutional agreement in the assessment of dobutamine stress echocardiograms using modern stress echo cardiographic technology in combination with standardized data acquisition and assessment criteria. Method and Results Among six experienced institutions, 150 dobutamine stress echocardiograms (dobutamine up to 40 mug.kg(-1) min(-1) and atropine up to I mg) were performed on patients with suspected coronary artery disease using fundamental and harmonic imaging following a consistent digital acquisition protocol. Each dobutamine stress echocardiogram was assessed at every institution regarding endocardial visibility and left ventricular wall motion without knowledge of any other data using standardized reading criteria. No patients were excluded due to poor image quality or inadequate stress level. Coronary angiography was performed within 4 weeks. Coronary angiography demonstrated significant coronary artery disease (less than or equal to50% diameter stenosis) in 87 patients. Using harmonic imaging an average of 5.2+/-0.9 institutions agreed on dobutamine stress echocardiogram results as being normal or abnormal (mean kappa 0.55; 95% CI 0.50-0.60). Agreement was higher in patients with no (equal assessment of dobutamine stress echocardiogram results by 5.5 +/- 0.8 institutions) or three-vessel coronary artery disease (5.4 +/- 0.8 institutions) and lower in one- or two- vessel disease (5.0 +/- 0.9 and 5.2 +/- 1.0 institutions, respectively-, P=0.041). Disagreement on test results was greater in only minor wall motion abnormalities. Agreement on dobutamine stress echocardiogram results was lower using fundamental imaging (mean kappa 0.49; 95% CI 0.44-0.54; P

Evolution of the secondary structure of the rRNA internal transcribed spacer 2 (ITS2) in hard ticks (Ixodidae, Arthropoda)

ITS2 sequences are used extensively in molecular taxonomy and population genetics of arthropods and other animals yet little is known about the molecular evolution of ITS2. We studied the secondary structure of ITS2 in species from each of the six main lineages of hard ticks (family Ixodidae). The ITS2 of these ticks varied in length from 679 bp in Ixodes scapularis to 1547 bp in Aponomma concolor. Nucleotide content varied also: the ITS2 of ticks from the Prostriata lineage (Ixodes spp.) had 46-49% GC whereas ITS2 sequences of ticks from the Metastriata lineage (all other hard ticks) had 61-62% GC. Despite variation in nucleotide sequence, the secondary structure of the ITS2 of all of these ticks apparently has five domains. Stems 1, 3, 4 and 5 of this secondary structure were obvious in all of the species studied. However, stem 2 was not always obvious despite the fact that it is flanked by highly conserved sequence motifs in the adjacent stems, stems 1 and 3. The ITS2 of hard ticks has apparently evolved mostly by increases and decreases in length of the nucleotide sequences, which caused increases, and decreases in the length of stems of the secondary structure. This is most obvious when stems of the secondary structures of the Prostriata (Ixodes spp.) are compared to those of the Metastriata (all other hard ticks). Increases in the size of the ITS2 may have been caused by replication slippage which generated large repeats, like those seen in Haemaphysalis humerosa and species from the Rhipicepalinae lineage, and the small repeats found in species from the other lineages of ticks.

Virulence of Streptococcus pneumoniae: PsaA mutants are hypersensitive to oxidative stress

psaA encodes a 37-kDa pneumococcal lipoprotein which is part of an ABC Mn(II) transport complex. Streptococcus pneumoniae D39 psaA mutants have previously been shown to be significantly less virulent than wild-type D39, but the mechanism underlying the attenuation has not been resolved. In this study, we have shown that psaA and psaD mutants are highly sensitive to oxidative stress, i.e., to superoxide and hydrogen peroxide, which might explain why they are less virulent than the wild-type strain. Our investigations revealed altered expression of the key oxidative-stress response enzymes superoxide dismutase and NADH oxidase in psaA and psaD mutants, suggesting that PsaA and PsaD may play important roles in the regulation of expression of oxidative-stress response enzymes and intracellular redox homeostasis.

Acute stress hyperglycemia in cats is associated with struggling and increased concentrations of lactate and norepinephrine

We characterized the changes in blood glucose concentrations in healthy cats exposed to a short stressor and determined the associations between glucose concentrations, behavioral indicators of stress, and blood variables implicated in stress hyperglycemia (plasma glucose, lactate, insulin, glucagon, cortisol, epinephrine, and norepinephrine concentrations). Twenty healthy adult cats with normal glucose tolerance had a 5-minute spray bath. Struggling and vocalization were the most frequent behavioral responses. There was a strong relationship between struggling and concentrations of glucose and lactate. Glucose and lactate concentrations increased rapidly and significantly in all cats in response to bathing, with peak concentrations occurring at the end of the bath (glucose baseline 83 mg/dL, mean peak 162 mg/dL; lactate baseline 6.3 mg/dL, mean peak 64.0 mg/dL). Glucose response resolved within 90 minutes in 12 of the 20 cats. Changes in mean glucose concentrations were strongly correlated with changes in mean lactate (r =.84; P

Modelling of microstructure formation and evolution during solidification

A comprehensive probabilistic model for simulating microstructure formation and evolution during solidification has been developed, based on coupling a Finite Differential Method (FDM) for macroscopic modelling of heat diffusion to a modified Cellular Automaton (mCA) for microscopic modelling of nucleation, growth of microstructures and solute diffusion. The mCA model is similar to Nastac's model for handling solute redistribution in the liquid and solid phases, curvature and growth anisotropy, but differs in the treatment of nucleation and growth. The aim is to improve understanding of the relationship between the solidification conditions and microstructure formation and evolution. A numerical algorithm used for FDM and mCA was developed. At each coarse scale, temperatures at FDM nodes were calculated while nucleation-growth simulation was done at a finer scale, with the temperature at the cell locations being interpolated from those at the coarser volumes. This model takes account of thermal, curvature and solute diffusion effects. Therefore, it can not only simulate microstructures of alloys both on the scale of grain size (macroscopic level) and the dendrite tip length (mesoscopic level), but also investigate nucleation mechanisms and growth kinetics of alloys solidified with various solute concentrations and solidification morphologies. The calculated results are compared with values of grain sizes and solidification morphologies of microstructures obtained from a set of casting experiments of Al-Si alloys in graphite crucibles.

Development of the HIV/AIDS stress scale

Development of a self-report measure of stress specific to HIV/AIDS is needed to advance our understanding of the role of stress in adaptation to HIV/AIDS: hence, the aim of this study was the development of the HIV/AIDS Stress Scale. A total of 132 homosexual/bisexual men with HIV/AIDS v ere interviewed and completed the HIV/AIDS Stress Scale and measures of coping strategies, appraisal, social support and adjustment (global distress, depression, social adjustment, number of HIV symptoms, and subjective health status) at three time points. Thirty-nine primary caregivers were interviewed and completed measures of stress and adjustment. Exploratory factor analyses of the HIV/AIDS Stress Scale items revealed three factors: Social, Instrumental and Emotional/Existential Stress. Factors had adequate internal reliabilities and were stable over 12 months. Construct validation data are consistent with recent stress/coping research that links higher levels of stress with more HIV symptoms. reliance on emotion-focused coping, lower social support, poorer levels of adjustment and higher levels of caregiver stress. Results extend this research by revealing new differential relations between various stress dimensions and stress/coping variables. Convergent validation data suggest that the HIV/AIDS Stress Scale shares conceptual similarity with threat appraisal. and differs from control liability and challenge appraisals. The HIV/AIDS Stress Scale shows potential for the elucidation of the role of stress in coping and adaptation to HIV/AIDS and disease progression in both research and clinical applications.

Adjustment of homeless adolescents to a crisis shelter: Application of a stress and coping model

The present study examined the utility of a stress and coping model of adaptation to a homeless shelter among homeless adolescents. Seventy-eight homeless adolescents were interviewed and completed self-administered scales at Time 1 (day of shelter entry) and Time 2 (day of discharge). The mean duration of stay at the shelter was 7.23 days (SD = 7.01). Predictors included appraisal (threat and self-efficacy), coping resources, and coping strategies (productive, nonproductive, and reference to others coping). Adjustment outcomes were Time I measures of global distress, physical health, clinician-and youthworker- rated social adjustment, and externalizing behavior and Time 2 youthworker-rated social adjustment and goal achievement. Results of hierarchical regression analyses indicated that after controlling for the effects of relevant background variables (number of other shelters visited, sexual, emotional, and physical abuse), measures of coping resources, appraisal, and coping strategies evidenced distinct relations with measures of adjustment in ways consistent with the model's predictions with few exceptions. In cross-sectional analyses better Time I adjustment was related to reports of higher levels of coping resources, self-efficacy beliefs, and productive coping strategies, and reports of lower levels of threat appraisal and nonproductive coping strategies. Prospective analyses showed a link between reports of higher levels of reference to others coping strategies and greater goal achievement and, unexpectedly, an association between lower self-efficacy beliefs and better Time 2 youthworker-rated social adjustment. Hence, whereas prospective analyses provide only limited support for the use of a stress and coping model in explaining the adjustment of homeless adolescents to a crisis shelter, cross-sectional findings provide stronger support.

Relationship between stress-induced martensitic transformation and impact toughness in low carbon austenitic steels

The effect of test temperature, which controls the stability of austenite, on the impact toughness of a low carbon Fe-Ni-Mn-C austenitic steel and 304 stainless steel, has been investigated. Under impact conditions, stress-induced martensitic transformation occurred, in a region near the fracture surface, at test temperatures below 80degreesC for the Fe-Ni-Mn-C steel and below -25degreesC for 304 stainless steel. The former shows significant transformation toughening and the highest impact toughness was obtained at 10degreesC, which corresponds to the maximum amount of martensite formed by stress-induced transformation above the Ms temperature. The stress-induced martensitic transformation contributes negatively to the impact toughness in the 304 stainless steel. Increasing the amount of stress-induced transformation to martensite, lowered the impact toughness. The experimental results can be well explained by the Antolovich theory through the analysis of metallography and fractography. The different effect of stress-induced transformation on the impact toughness in Fe-Ni-Mn-C steel and 304 stainless steel has been further understood by applying the crystallographic model for stress-induced martensitic transformation to these two steels. (C) 2002 Kluwer Academic Publishers.

Osmoregulative capacity in birdseed millet under conditions of water stress. I. Variation in Setaria italica and Panicum miliaceum

Experiments involving 14 accessions of Panicum miliaceum L. (Proso millet) and 11 accessions of Setaria italica L. (Foxtail millet) have demonstrated variability in the degree of osmoregulative capacity among these accessions. Birdseed millet is generally claimed to be sensitive to drought stress, apparently because of a shallow root system. Accessions with high osmoregulative capacity demonstrate at least some drought tolerance. Osmoregulative capacity was measured on flag leaves of headed millet plants in pots undergoing water stress in a controlled environment chamber. Osmoregulative capacity was determined from the relationship between osmotic potential and leaf water potential; and the logarithmic relationship between osmotic potential and relative water content. The group of accessions of S. italica showed an overall level of osmoregulative capacity which was greater than that observed for the group of P. miliaceum accessions. Four accessions of S. italica (108042, 108463, 108541 and 108564) and one accession of P. miliaceum (108104) demonstrated high osmoregulative capacity. Differences of 1.05 MPa or more between observed and estimated osmotic potential were found at relative water contents of 80 % among these accessions. The extent of osmoregulative capacity was associated with osmotic potential at full turgor and the rate of decline in osmotic potential as leaf water potentail declined.

Ross River virus disease in tropical Queensland: evolution of rheumatic manifestations in an inception cohort followed for six months

Objective: To describe the natural history of rheumatic manifestations of Ross River virus (RRV) disease. Design: Prospective longitudinal clinical review. Setting: North Queensland local government areas of Cairns, Douglas, Mareeba and Atherton during January to May 1998. Participants: General practice patients diagnosed with RRV disease on the basis of symptoms and a positive RRV IgM result. Main outcome measures: Rheumatic symptoms and signs assessed as soon as possible after disease onset and on two subsequent occasions (up to 6.5 months after onset). Results: 57 patients were recruited, 47 of whom were reviewed three times (at means of 1.1, 2.4 and 3.6 months after disease onset). Results are reported for these 47: 46 (98%) complained of joint pain at first review, with the ankles, wrists, fingers, knees and metacarpophalangeal joints (II-IV) most commonly involved. Prevalence of joint pain decreased progressively on second and third reviews, both overall (92% and 68% of patients, respectively), and in the five joints most commonly affected. The prevalence of other common rheumatic symptoms and signs, and use of non-steroidal anti-inflammatory drugs, also progressively declined over the three reviews. Conclusions: Earlier studies may have overestimated the prevalence and duration of symptoms in RRV disease. Progressive resolution over 3-6 months appears usual.

Harmful drinking in military veterans with post-traumatic stress disorder: Association with the D2 dopamine receptor A1 allele

Aims: The frequency of the Taq I A alleles (A1 and A2) of the D2 dopamine receptor (DRD2) gene was examined in Caucasian post-traumatic stress disorder (PTSD) patients and controls. Results: In 91 PTSD patients, the frequency of the A1 allele was higher (P = 6.12 x 10(-3)) than in the 51 controls. In the 38 PTSD harmful drinkers (greater than or equal to60 g alcohol/day), A1 allelic frequency was higher (P = 3.91 x 10(-2)) than in the 53 non-harmful drinkers (

Distribution and evolution of the Anopheles punctulatus group (Diptera : Culicidae) in Australia and Papua New Guinea

The members of the Anopheles punctulatus group are major vectors of malaria and Bancroftian filariasis in the southwest Pacific region. The group is comprised of 12 cryptic species that require DNA-based tools for species identification. From 1984 to 1998 surveys were carried out in northern Australia, Papua New Guinea and on islands in the southwest Pacific to determine the distribution of the A. punctulatus group. The results of these surveys have now been completed and have generated distribution data from more than 1500 localities through this region. Within this region several climatic and geographical barriers were identified that restricted species distribution and gene flow between geographic populations. This information was further assessed in light of a molecular phylogeny derived from the ssrDNA (18S). Subsequently, hypotheses have been generated on the evolution and distribution of the group so that future field and laboratory studies may be approached more systematically. This study suggested that the ability for widespread dispersal was found to have appeared independently in species that show niche-specific habitat preference (Anopheles farauti s.s. and A. punctulatus) and conversely in species that showed diversity in their larval habitat (Anopheles farauti 2). Adaptation to the monsoonal climate of northern Australia and southwest Papua New Guinea was found to have appeared independently in A. farauti s.s., A. farauti 2 and Anopheles farauti 3. Shared or synapomorphic characters were identified as saltwater tolerance (A. farauti s.s. and Anopheles farauti 7) and elevational affinities above 1500 m (Anopheles farauti 5, Anopheles farauti 6 and A. farauti 2). (C) 2002 Australian Society for Parasitology Inc. Published by Elsevier Science Ltd. All rights reserved.