Stability and Mixing of a Vertical Axisymmetric Buoyant Jet in Shallow Water

The stability, mixing and effect of downstream control on axisymmetric turbulent buoyant jets discharging vertically into shallow stagnant water is studied using 3D Reynolds-averaged Navier–Stokes equations (RANS) combined with a buoyancy-extended k –ε model. The steady axisymmetric turbulent flow, temperature (or tracer concentration) and turbulence fields are computed using the finite volume method on a high resolution grid. The numerical predictions demonstrate two generic flow patterns for different turbulent heated jet discharges and environmental parameters (i) a stable buoyant discharge with the mixed fluid leaving the vertical jet region in a surface warm water layer; and (ii) an unstable buoyant discharge with flow recirculation and re-entrainment of heated water. A stratified counterflow region always appears in the far-field for both stable and unstable buoyant discharges. Provided that the domain radius L exceeds about 6H, the near field interaction and hence discharge stability is governed chiefly by the jet momentum length scale to depth ratio l_M/H, regardless of downstream control. The near field jet stability criterion is determined to be l_M/H = 3.5. A radial internal hydraulic jump always exists beyond the surface impingement region, with a 3- to 6-fold increase in dilution across the jump compared with vertical buoyant jet mixing. The predicted stability category, velocity and temperature/concentration fields are well-supported by experiments of all previous investigators.     

Housing values,census estimates,disequilibrium, and the environmental cost of airport noise: A case study of Atlanta

Two unresolved issues about airport noise-property value studies are addressed. The first issue concerns the comparability of empirical results from aggregate census data vs individual sales values, and the second issue concerns the homogeneity and stability of results from housing price studies over time and across markets. Hedonic price models from two sets of data for a residential area near the Atlanta International Airport are estimated at two points in time 1979–1980 and 1970–1972. The available data yield similar estimates of the noise discount over time, and from the prices of individual house sales vs owner-appraised census block aggregates.     

Threat-sensitive foraging by larval threespine sticklebacks (Gasterosteus aculeatus)

Summary The threat-sensitive predator avoidance hypothesis predicts that prey can assess the relative threat posed by a predator and adjust their behaviour to reflect the magnitude of the threat. We tested the ability of larval threespine sticklebacks to adjust their foraging in the presence of predators by exposing them to conspecific predators of various sizes and recording their foraging and predator avoidance behaviours. Larvae (<30 days post-hatch) displayed predator escape behaviours only towards attacking predators. At 3 weeks post-hatch larvae approached the predator after fleeing, a behaviour which may be the precursor to predator inspection. Larvae reduced foraging and spent less time in the proximity of large and medium-sized predators compared to small predators. The reduction in foraging was negatively correlated to the predator/larva size ratio, indicating that larvae increased their foraging as they increased in size relative to the predator. We conclude that larval sticklebacks can assess the threat of predation early in their ontogeny and adjust their behaviour accordingly.Correspondence to: J.A. Brown     

Prenatal ultrasound diagnosis of rhizomelic chondrodysplasia punctata in a primigravida

Rhizomelic chondrodysplasia punctata (RCDP) is a sublethal autosomal recessive disorder characterized by skeletal dysplasia, microcephaly, mental retardation, congenital cataracts, joint contractures, skin changes, and failure to thrive. Prenatal ultrasound diagnosis has been reported during the second trimester of pregnancy. Prenatal diagnosis is also possible from the first trimester onwards by demonstration of peroxisomal dysfunction in cultured chorionic villous or amniotic fluid cells. In all cases reported hitherto, the prenatal diagnosis was established after the birth of a previous affected child. In contrast to these studies in pregnant multiparous women at risk for RCDP, we report on the first case of prenatal ultrasound diagnosis of RCDP at 19 weeks' gestation in a primigravida. In addition, a complex cardiac malformation associated with hypoplasia of the thymus (DiGeorge anomaly) is described.     

Ultrasonic placental localization in relation to spontaneous abortion after mid-trimester amniocentesis

This paper summarizes our experience with a series of 562 women referred for mid-trimester amniocentesis for prenatal diagnosis. Ultrasonography was utilized for placental localization. Follow-up revealed a fetal loss rate of 3.03 per cent with 1.96 per cent being spontaneous abortions. Patients with an anterior placenta had a fetal loss and spontaneous abortion rate of 4.06 per cent and 3·05 per cent, respectively. No significant difference in the incidence of fetal loss (p > 0·1) or spontaneous abortion (p > 0·5) was found in patients having an anterior versus a posterior placenta. Neither multiple insertions through an anterior placenta nor blood contaminated amniotic fluid from patients with an anterior placenta were associated with an increased incidence of fetal loss or spontaneous abortion.     

In situ remediation of soils contaminated with toxic metal ions using microwave energy

Following onto our work on the in situ remediation of soils contaminated with PAH's, PCB's and other polychlorinated organic compounds using microwave energy, we now report a preliminary investigation on the in situ remediation of soils contaminated with toxic metal ions: Cd(II), Mn(II), Th(IV), Cr(III) and mainly Cr(VI). The soil is partially vitrified in the process, and extraction with hot (70 degrees C) 35% nitric acid for 4.5 h leads to the recovery of very small amounts of the metals which had been spiked into the clean soil: Cd, Mn, and Cr(III) are completely immobilized (unextractable), Th is mostly unextractable, and Cr(VI) partially extractable at very high levels of spiking, but almost completely unextractable using the US EPA Toxicity Characteristic Leaching Procedure. This suggests that contaminated soils which are not going to be used for agricultural purposes can be remediated safely to preset depths without fear of the toxic metal ions leaching out for a long time.     

A graduate level course: Teaching stress management skills to occupational health physicians and practitioners

The WHO Study Group on Training and Evaluation in Occupational Medicine has recently emphasized the importance of incorporating theoretical and practical aspects of stress prevention and management in the professional training of occupational health practitioners. Such a course was developed for the Tel-Aviv University Medical School graduate program in occupational health. The course objectives are consistent with the current call for improved training in psychosocial issues in medical care. Twenty-three occupational health practitioners (physicians, nurses, hygienists and social workers) participated in a bi-semester course. The first part included a stress management and prevention program based on the RET (Rational-Emotive Training) model. The second involved developing and implementing a field project on primary and secondary prevention of stress and its outcomes. Pre-, mid-and post-course questionnaires showed significantly improved psychosocial ability and reduced irrational/dysfunctional thinking, considered a causal factor in stress and burnout. Acquiring such anti-stress resources may benefit practitioners and clients/patients, both potential victims of occupational stress alike. We recommend the inclusion of such extended courses to the professional training of occupational health practitioners.     

A multivariate test of the job characteristics theory of work motivation

This paper reports the results of a multivariate test of the Job Characteristics Theory of Work Motivation using data from employees of a state agency in the United States. A canonical correlation analysis was done first to determine whether there was a statistically significant multivariate relationship among the variables. A hierarchical multiple regression analysis was then done to test main effects and interactions. The results of the study were mostly supportive of predictions from the theory. The interactions with Growth Need Strength were different in form for low and high GNS people. The implications of the results for both the theory and job redesign practice are discussed.     

Quality metrics in design for environment

There is a growing commitment by manufacturers, both in the United States and abroad, to assure environmental responsibility for all of their operations. This trend is driven partly by market demands for “green” products and partly by changes in international standards and regulations. In response, leading companies are demonstrating that environmental improvement can actually increase profitability, and design for environment (DFE) is emerging as an important business practice. The ability to evaluate environmental quality in objective, measurable terms is a key component of an effective DFE capability. In particular, environmental quality metrics are essential to support goal setting, monitoring, and continuous improvement in the design of products and processes. This article describes environmental quality measurement tools and procedures, particularly as they relate to DFE. One of the challenges of performance measurement is to incorporate a life-cycle view of environmental performance into measurement tools that can be easily computed and tracked.