Forced Oscillations of a Contained Rotating Stratified Fluid

The motion generated by forced oscillations in an incompressible inviscid rotating and/or stratified fluid is examined under linear theory taking the density variation on the inertia terms. The solution consists of numerous internal modes in addition to the mode which oscillates with forcing frequency. Resonance occurs when the forcing frequency is equal to one of the frequencies of the internal modes. Some of these modes grow linearly or exponentially with time rendering the motion unstable and eventually may lead to turbulence. Most of the results discussed here will be missed under Boussinesq approximation.

Flow of a micropolar fluid in a tube with sinusoidal deformation

The flow of a micropolar fluid for sinusoidally deforming boundaries is discussed in detail. The velocity and microrotation fields and the streamfunction are determined and plotted under the assumption of small deformations.

Transport of sugars by the fat body of the silkworm, Bombyx mori

The transport of glucose and α-methyl glucoside into the fat body of the silkworm, Bombyx mori L., has been studied. Glucose is transported into the tissue by a mechanism similar to facilitated diffusion and α-methyl glucoside by a diffusion process. The uptake of these sugars is neither energy dependent nor coupled to a phosphotransferase system.

Building in Israel Overlooking Body of Water

Digital image

Insights into PBDE uptake, body burden, and elimination gained from Australian age–Concentration trends observed shortly after peak exposure

Background Population pharmacokinetic models combined with multiple sets of age– concentration biomonitoring data facilitate back-calculation of chemical uptake rates from biomonitoring data. Objectives We back-calculated uptake rates of PBDEs for the Australian population from multiple biomonitoring surveys (top-down) and compared them with uptake rates calculated from dietary intake estimates of PBDEs and PBDE concentrations in dust (bottom-up). Methods Using three sets of PBDE elimination half-lives, we applied a population pharmacokinetic model to the PBDE biomonitoring data measured between 2002–2003 and 2010–2011 to derive the top-down uptake rates of four key PBDE congeners and six age groups. For the bottom-up approach, we used PBDE concentrations measured around 2005. Results Top-down uptake rates of Σ4BDE (the sum of BDEs 47, 99, 100, and 153) varied from 7.9 to 19 ng/kg/day for toddlers and from 1.2 to 3.0 ng/kg/day for adults; in most cases, they were—for all age groups—higher than the bottom-up uptake rates. The discrepancy was largest for toddlers with factors up to 7–15 depending on the congener. Despite different elimination half-lives of the four congeners, the age–concentration trends showed no increase in concentration with age and were similar for all congeners. Conclusions In the bottom-up approach, PBDE uptake is underestimated; currently known pathways are not sufficient to explain measured PBDE concentrations, especially in young children. Although PBDE exposure of toddlers has declined in the past years, pre- and postnatal exposure to PBDEs has remained almost constant because the mothers’ PBDE body burden has not yet decreased substantially.

Magnetic Field Due to the Self-Gravity-Induced Electric Polarization of a Rotating Massive Body

he notion of the gravity-induced electric field has been applied to an entire self-gravitating massive body. The resulting electric polarization of the otherwise neutral body, when taken in conjunction with the latter's rotation, is shown to generate an axial-magnetic field of the right type and order of magnitude for certain astrophysical objects. In the present treatment the electric polarization is calculated in the ion-continuum Thomas-Fermi approximation while the electrodynamics of the continuous medium is treated in the nonrelativistic approximation.

Unsteady Motion of a Stratified Rotating Viscous Fluid between Two Disks

Abstract is not available.

Investigation of the effects of extracellular osmotic pressure on morphology and mechanical 1 properties of individual chondrocyte

It has been demonstrated that most cells of the body respond to osmotic pressure in a systematic manner. The disruption of the collagen network in the early stages of osteoarthritis causes an increase in water content of cartilage which leads to a reduction of pericellular osmolality in chondrocytes distributed within the extracellular environment. It is therefore arguable that an insight into the mechanical properties of chondrocytes under varying osmotic pressure would provide a better understanding of chondrocyte mechanotransduction and potentially contribute to knowledge on cartilage degeneration. In this present study, the chondrocyte cells were exposed to solutions with different osmolality. Changes in their dimensions and mechanical properties were measured over time. Atomic Force Microscopy (AFM) was used to apply load at various strain-rates and the force-time curves were logged. The thin-layer elastic model was used to extract the elastic stiffness of chondrocytes at different strain-rates and at different solution osmolality. In addition, the porohyperelastic (PHE) model was used to investigate the strain-rate dependent responses under the loading and osmotic pressure conditions. The results revealed that the hypo-osmotic external environment increased chondrocyte dimensions and reduced Young’s modulus of the cells at all strain-rates tested. In contrast, the hyper-osmotic external environment reduced dimensions and increased Young’s modulus. Moreover, by using the PHE model coupled with inverse FEA simulation, we established that the hydraulic permeability of chondrocytes increased with decreasing extracellular osmolality which is consistent with previous work in the literature. This could be due to a higher intracellular fluid volume fraction with lower osmolality.

A note on the application of a radiation condition for a source in a rotating stratified fluid

The motion due to an oscillatory point source in a rotating stratified fluid has been studied by Sarma & Naidu (1972) by using threefold Fourier transforms. The solution obtained by them in the hyperbolic case is wrong since they did not make use of any radiation condition, which is always necessary to get the correct solution. Whenever the motion is created by a source, the condition of radiation is that the sources must remain sources, not sinks of energy and no energy may be radiated from infinity into the prescribed singularities of the field. The purpose of the present note is to explain how Lighthill's (1960) radiation condition can be applied in the hyperbolic case to pick the correct solution. Further, the solution thus obtained is reiterated by an alternative procedure using Sommerfeld's (1964) radiation condition.

Individuals on the Move : Body Condition Dependent Dispersal and Quasi-Local Competition in Metapopulations

Individual movement is very versatile and inevitable in ecology. In this thesis, I investigate two kinds of movement body condition dependent dispersal and small-range foraging movements resulting in quasi-local competition and their causes and consequences on the individual, population and metapopulation level. Body condition dependent dispersal is a widely evident but barely understood phenomenon. In nature, diverse relationships between body condition and dispersal are observed. I develop the first models that study the evolution of dispersal strategies that depend on individual body condition. In a patchy environment where patches differ in environmental conditions, individuals born in rich (e.g. nutritious) patches are on average stronger than their conspecifics that are born in poorer patches. Body condition (strength) determines competitive ability such that stronger individuals win competition with higher probability than weak individuals. Individuals compete for patches such that kin competition selects for dispersal. I determine the evolutionarily stable strategy (ESS) for different ecological scenarios. My models offer explanations for both dispersal of strong individuals and dispersal of weak individuals. Moreover, I find that within-family dispersal behaviour is not always reflected on the population level. This supports the fact that no consistent pattern is detected in data on body condition dependent dispersal. It also encourages the refining of empirical investigations. Quasi-local competition defines interactions between adjacent populations where one population negatively affects the growth of the other population. I model a metapopulation in a homogeneous environment where adults of different subpopulations compete for resources by spending part of their foraging time in the neighbouring patches, while their juveniles only feed on the resource in their natal patch. I show that spatial patterns (different population densities in the patches) are stable only if one age class depletes the resource very much but mainly the other age group depends on it.

Effect of electric arc discharge on hypersonic blunt body drag

Experimental results on the effect of energy deposition using an electric arc discharge, upstream of a 60° half angle blunt cone configuration in a hypersonic flow is reported.Investigations involving drag measurements and high speed schlieren flow visualization have been carried out in hypersonic shock tunnel using air and argon as the test gases; and an unsteady drag reduction of about 50% (maximum reduction) has been observed in the energy deposition experiments done in argon environment. These studies also show that the effect of discharge on the flow field is more pronounced in argon environment as compared to air, which confirms that thermal effects are mainly responsible for flow alteration in presence of the discharge.

Measurement of aerodynamic forces for missile shaped body in hypersonic shock tunnel using 6-component accelerometer based balance system

This paper reports the basic design of a new six component force balance system using miniature piezoelectric accelerometers to measure all aerodynamic forces and moments for a test model in hypersonic shock tunnel (HST2). Since the flow duration in a hypersonic shock tunnel is of the order of $1$ ms, the balance system [1] uses fast response accelerometers (PCB Piezotronics; frequency range of 1-10 kHz) for obtaining the aerodynamic data. The alance system has been used to measure the basic aerodynamic forces and moments on a missile shaped body at Mach $8$ in the IISc hypersonic shock tunnel. The experimentally measured values match well with theoretical predictions.

In vitro degradation of hepatotoxic indospicine in indigofera spicata by camel foregut fluid

Indospicine toxicosis was reported in sheep, goats and cattle fed on Indigofera, a leguminous plant rich in indospicine. Recent death report on dogs as a result of dietary ingestion of indospicine contaminated camel meat has raised concern about the distribution of this toxin in camels fed on Indigofera. This in vitro study aimed at measuring the degradability of indospicine in Indigofera spicata by camel-foregut fluid and attempted at explaining indospicine accumulation in meat tissue. In the first experiment, in vitro dry matter digestibility and indospicine disappearance were evaluated by using foregut fluid from 15 feral camels. Foregut fluid was collected post mortem from a nearby abattoir. In the second experiment, a composite foregut fluid obtained from three feral camels was used to examine the time-dependent degradation of indospicine. Results indicated that 99 of the dietary indospicine was degraded after 48 h of incubation. The time-dependent degradation study showed rapid degradation (11 µg/h) during the first 18 h of incubation, followed by a much slower rate (2 µg/h) between 18-48 h. Results demonstrated the ability of the camel microbiota to degrade indospicine and suggest the presence of a by-pass mechanism that enables the toxin to escape degradation and reaches the intestine.