Capillary jet instability under the influence of gravity

The focus of this paper is on the effect of gravity stretching on disturbed capillary jet instability. Break-up and droplet formation under low flows are simulated using finite difference solution of a one-dimensional approximation of disturbed capillary jet instability chosen from the work by Eggers and Dupont (J. Fluid Mech. 155 (1994) 289). Experiments were conducted using water and aqueous glycerol solutions to compare with simulations. We use a gravity parameter, G, which quantifies gravity stretching by relating flow velocity, orifice size and acceleration and is the reciprocal of the Fronde number. The optimum disturbance frequency Omega(opt) was found to be inversely proportional to G. However, this relationship appears to be complex for the range of G's investigated. At low G, the relationship between Omega(opt) and G appears to be linear but takes on a weakly decaying like trend as G increases. As flows are lowered, the satellite-free regime decreases, although experimental observation found that merging of main and satellite drops sometimes offset this effect to result in monodispersed droplet trains post break-up. Viscosity did not significantly affect the relationship between the disturbance frequency and G, although satellite drops could be seen more clearly close to the upper limit for instability at high G's. It is possible to define regimes of satellite formation under low flows by considering local wavenumbers at the point of instability. (C) 2004 Elsevier Ltd. All rights reserved.

Influence of body iron store status and cigarette smoking on cadmium body burden of healthy Thai women and men

The influence of cigarette smoking, body iron store status and gender on cadmium (Cd) body burden was examined in a group of 197 healthy Thais with overall mean age of 30.5 year (19-47 year). The lowest, geometric mean, and the highest urinary Cd excretion rate was 0.04, 0.46 and 3.84 mug/g creatinine, respectively. The prevalence of low iron stores (serum ferritin

The head and body lice of humans are genetically distinct (Insecta : Phthiraptera, Pediculidae): evidence from double infestations

Little is known about the population genetics of the louse infestations of humans. We used microsatellite DNA to study 11 double infestations, that is, hosts infested with head lice and body lice simultaneously. We tested for population structure on a host, and for population structure among seven hosts that shared sleeping quarters. We also sought evidence of migration among louse populations. Our results showed that: (i) the head and body lice on these individual hosts were two genetically distinct populations; (ii) each host had their own populations of head and body lice that were genetically distinct to those on other hosts; and (iii) lice had migrated from head to head, and from body to body, but not between heads and bodies. Our results indicate that head and body lice are separate species.

Phosphate forms an unusual tripodal complex with the Fe-Mn center of sweet potato purple acid phosphatase

Purple acid phosphatases (PAPs) are a family of binuclear metalloenzymes that catalyze the hydrolysis of phosphoric acid esters and anhydrides. A PAP in sweet potato has a unique, strongly antiferromagnetically coupled Fe(III)-Mn(II) center and is distinguished from other PAPs by its increased catalytic efficiency for a range of activated and unactivated phosphate esters, its strict requirement for Mn(II), and the presence of a mu-oxo bridge at pH 4.90. This enzyme displays maximum catalytic efficiency (k(cat)/K-m) at pH 4.5, whereas its catalytic rate constant (k(cat)) is maximal at near-neutral pH, and, in contrast to other PAPs, its catalytic parameters are not dependent on the pK(a) of the leaving group. The crystal structure of the phosphate-bound Fe(III)-Mn(II) PAP has been determined to 2.5-Angstrom resolution (final R-free value of 0.256). Structural comparisons of the active site of sweet potato, red kidney bean, and mammalian PAPs show several amino acid substitutions in the sweet potato enzyme that can account for its increased catalytic efficiency. The phosphate molecule binds in an unusual tripodal mode to the two metal ions, with two of the phosphate oxygen atoms binding to Fe(III) and Mn(II), a third oxygen atom bridging the two metal ions, and the fourth oxygen pointing toward the substrate binding pocket. This binding mode is unique among the known structures in this family but is reminiscent of phosphate binding to urease and of sulfate binding to A protein phosphatase. The structure and kinetics support the hypothesis that the bridging oxygen atom initiates hydrolysis.

Mind and body: Concepts of human cognition, physiology and false belief in children with autism or typical development

This study examined theory of mind (ToM) and concepts of human biology (eyes, heart, brain, lungs and mind) in a sample of 67 children, including 25 high functioning children with autism (age 6-13), plus age-matched and preschool comparison groups. Contrary to Baron-Cohen [1989, Journal of Autism and Developmental Disorders, 19(4), 579-600], most children with autism correctly understood the functions of the brain (84%) and the mind (64%). Their explanations were predominantly mentalistic. They outperformed typically developing preschoolers in understanding inner physiological (heart, lungs) and cognitive (brain, mind) systems, and scored as high as age-matched typical children. Yet, in line with much previous ToM research, most children with autism (60%) failed false belief, and their ToM performance was unrelated to their understanding of. human biology. Results were discussed in relation to neurobiological and social-experiential accounts of the ToM deficit in autism.

Media influence on the body image of children and adolescents

To study the media messages portrayed to children, 925 students, from 9 to up to 14 years of age, completed “The Sociocultural Influences Questionnaire.” The media section is the focus of this paper, and the responses from three questions were selected to examine the media's influence to be slimmer, increase weight, or increase muscle size. While the girls and boys exhibited different levels of agreement with each media influence, both genders disagreed that media messages were implying they should gain weight. This is in agreement with the belief that the media perpetuates the ideal of thinness and there is a negative stigma associated with being overweight.

Three-body recombination of ultracold Bose gases using the truncated Wigner method

We apply the truncated Wigner method to the process of three-body recombination in ultracold Bose gases. We find that within the validity regime of the Wigner truncation for two-body scattering, three-body recombination can be treated using a set of coupled stochastic differential equations that include diffusion terms, and can be simulated using known numerical methods. As an example we investigate the behavior of a simple homogeneous Bose gas, finding a very slight increase of the loss rate compared to that obtained by using the standard method.

The influence of natural body sway on neuromuscular responses to an unpredictable surface translation

Previous research has shown that the postural configuration adopted by a subject, such as active leaning, influences the postural response to an unpredictable support surface translation. While those studies have examined large differences in postural conditions, it is of additional interest to examine the effects of naturally occurring changes in standing posture. Thus, it was hypothesized that the normal postural sway observed during quiet standing would affect the responses to an unpredictable support surface translation. Seventeen young adults stood quietly on a moveable platform and were perturbed in either the forward or backward direction when the location of the center of pressure (COP) was either 1.5 standard deviations anterior or posterior to the mean baseline COP signal. Postural responses, in the form of electromyographic (EMG) latencies and amplitudes, were recorded from lower limb and trunk muscles. When the location of the COP at the time of the translation was in the opposite, as compared to the same, direction as the upcoming translation, there was a significantly earlier onset of the antagonists (10-23%, i.e. 15-45 ms) and a greater EMG amplitude (14-39%) in four of the six recorded muscles. Stepping responses were most frequently observed during trials where the position of the COP was opposite to the direction of the translation. The results support the hypothesis that postural responses to unpredictable support surface translations are influenced by the normal movements of postural sway. The results may help to explain the large variability of postural responses found between past studies.

Impact of ethnicity upon body composition assessment in Sri Lankan Australian children

Objectives: Obesity is a disease with excess body fat where health is adversely affected. Therefore it is prudent to make the diagnosis of obesity based on the measure of percentage body fat. Body composition of a group of Australian children of Sri Lankan origin were studied to evaluate the applicability of some bedside techniques in the measurement of percentage body fat. Methods: Height (H) and weight (W) was measured and BMI (W/H-2) calculated. Bioelectrical impedance analysis (BIA) was measured using tetra polar technique with an 800 mu A current of 50 Hz frequency. Total body water was used as a reference method and was determined by deuterium dilution and fat free mass and hence fat mass (FM) derived using age and gender specific constants. Percentage FM was estimated using four predictive equations, which used BIA and anthropometric measurements. Results: Twenty-seven boys and 15 girls were studied with mean ages being 9.1 years and 9.6 years, respectively. Girls had a significantly higher FM compared to boys. The mean percentage FM of boys (22.9 +/- 8.7%) was higher than the limit for obesity and for girls (29.0 +/- 6.0%) it was just below the cut-off. BMI was comparatively low. All but BIA equation in boys under estimated the percentage FM. The impedance index and weight showed a strong association with total body water (r(2)= 0.96, P < 0.001). Except for BIA in boys all other techniques under diagnosed obesity. Conclusions: Sri Lankan Australian children appear to have a high percentage of fat with a low BMI and some of the available indirect techniques are not helpful in the assessment of body composition. Therefore ethnic and/or population specific predictive equations have to be developed for the assessment of body composition, especially in a multicultural society using indirect methods such as BIA or anthropometry.