The role of fracture mechanics in the design of fuel tanks in space vehicles

With special reference to design of fuel tanks in space vehicles, the principles of fracture mechanics are reviewed. An approximate but extremely simple relationship is derived among the operating stress level, the length of crack, and the number of cycles of failure. Any one of the variables can be computed approximately from the knowledge of the other two, if the loading schedule (mission of the tank) is not greatly altered. Two sample examples illustrating the procedures of determining the allowable safe operating stress corresponding to a set of assumed loading schedule are included. The selection of sample examples is limited by the relatively meager available data on the candidate material for various stress ratios in the cycling

Thermochemical stability of low-iron, manganese-enriched olivine in astrophysical environments

Low-iron, manganese-enriched (LIME) olivine grains are found in cometary samples returned by the Stardust mission from comet 81P/Wild 2. Similar grains are found in primitive meteoritic clasts and unequilibrated meteorite matrix. LIME olivine is thermodynamically stable in a vapor of solar composition at high temperature at total pressures of a millibar to a microbar, but enrichment of solar composition vapor in a dust of chondritic composition causes the FeO/MnO ratio of olivine to increase. The compositions of LIME olivines in primitive materials indicate oxygen fugacities close to those of a very reducing vapor of solar composition. The compositional zoning of LIME olivines in amoeboid olivine aggregates is consistent with equilibration with nebular vapor in the stability field of olivine, without re-equilibration at lower temperatures. A similar history is likely for LIME olivines found in comet samples and in interplanetary dust particles. LIME olivine is not likely to persist in nebular conditions in which silicate liquids are stable

Neuroimaging evidence implicating cerebellum in support of sensory/cognitive processes associated with thirst.

Recent studies implicate the cerebellum, long considered strictly a motor control structure, in cognitive, sensory, and affective phenomenon. The cerebellum, a phylogenetically ancient structure, has reciprocal ancient connections to the hypothalamus, a structure important in vegetative functions. The present study investigated whether the cerebellum was involved in vegetative functions and the primal emotions engendered by them. Using positron emission tomography, we examined the effects on the cerebellum of the rise of plasma sodium concentration and the emergence of thirst in 10 healthy adults. The correlation of regional cerebral blood flow with subjects' ratings of thirst showed major activation in the vermal central lobule. During the development of thirst, the anterior and posterior quadrangular lobule, lingula, and the vermis were activated. At maximum thirst and then during irrigation of the mouth with water to alleviate dryness, the cerebellum was less activated. However, 3 min after drinking to satiation, the anterior quadrangular lobule and posterior cerebellum were highly activated. The increased cerebellar activity was not related to motor behavior as this did not occur. Instead, responses in ancient cerebellar regions (vermis, fastigal nucleus, archicerebellum) may be more directly related to vegetative and affective aspects of thirst experiences, whereas activity in neocerebellar (posterior) regions may be related to sensory and cognitive aspects. Moreover, the cerebellum is apparently not involved in the computation of thirst per se but rather is activated during changes in thirst/satiation state when the brain is "vigilant" and is monitoring its sensory systems. Some neocerebellar activity may also reflect an intentionality for gratification by drinking inherent in the consciousness of thirst

Asthma in Children and Adults-What Are the Differences and What Can They Tell us About Asthma

Asthma varies considerably across the life course. Childhood asthma is known for its overall high prevalence with a male predominance prior to puberty, common remission, and rare mortality. Adult asthma is known for its female predominance, uncommon remission, and unusual mortality. Both childhood and adult asthma have variable presentations, which are described herein. Childhood asthma severity is associated with duration of asthma symptoms, medication use, lung function, low socioeconomic status, racial/ethnic minorities, and a neutrophilic phenotype. Adult asthma severity is associated with increased IgE, elevated FeNO, eosinophilia, obesity, smoking, and low socioeconomic status. Adult onset disease is associated with more respiratory symptoms and asthma medication use despite higher prebronchodilator FEV1/FVC. There is less quiescent disease in adult onset asthma and it appears to be less stable than childhood-onset disease with more relapses and less remissions

Coulomb Blockade Oscillations of Conductance at Finite Energy Level Spacing in a Quantum Dot

We find an analytical expression for the conductance of a single electron transistor in the regime when temperature, level spacing, and charging energy of a grain are all of the same order. We consider the model of equidistant energy levels in a grain in the sequential tunneling approximation. In the case of spinless electrons our theory describes transport through a dot in the quantum Hall regime. In the case of spin-1/2 electrons we analyze the line shape of a peak, shift in the position of the peak's maximum as a function of temperature, and the values of the conductance in the odd and even valleys.Comment: RevTex, 13 pages, 13 figure

Coupled Enzyme Activity and Thermal Shift Screening of the Maybridge Rule of 3 Fragment Library Against Trypanosoma brucei Choline Kinase; A Genetically Validated Drug Target

In this study we interrogate 630 compounds of the Maybridge Rule of 3 Fragment Library for compounds that interact with, and inhibit TbCK. The Maybridge Rule of 3 Fragment Library is a small collection of quantifiable diverse, pharmacophoric rich, chemical entities that comply with the following criteria; MW ≤ 300, cLogP ≤ 3, H-Bond Acceptors ≤ 3, H-Bond Donors ≤ 3, Rotatable bonds (Flexibility Index) ≤ 3, Polar Surface Area ≤ 60 Å2 and aqueous solubility ≥ 1 mM using LogS and high purity (≥ 95%). Comparisons between two different screening methods, a coupled enzyme activity assay and differential scanning fluorimetry, has allowed identification of compounds that interact and inhibit the T. brucei choline kinase, several of which possess selective trypanocidal activity. Screening of a comparatively small fragment library by two different screening methods has allowed identification of several compounds that interact with and inhibit TbCK, a genetically validated drug target against African sleeping sickness. Some of the inhibitory fragments were also selectively trypanocidal, considering these are relatively simple molecules with no optimization, finding low μΜ inhibitors is very encouraging. Moreover some of the morphological phenotypes of these trypanocidal compounds include cell-cycle arrests similar to those observed for the TbCK conditional knockout grown under permissive conditions

Resonance of relativistic electrons with electromagnetic ion cyclotron waves

Relativistic electrons have been thought to more easily resonate with electromagnetic ion cyclotron (EMIC) waves if the total density is large. We show that, for a particular EMIC mode, this dependence is weak due to the dependence of the wave frequency and wave vector on the density. A significant increase in relativistic electron minimum resonant energy might occur for the H band EMIC mode only for small density, but no changes in parameters significantly decrease the minimum resonant energy from a nominal value. The minimum resonant energy depends most strongly on the thermal velocity associated with the field line motion of the hot ring current protons that drive the instability. High density due to a plasmasphere or plasmaspheric plume could possibly lead to lower minimum resonance energy by causing the He band EMIC mode to be dominant. We demonstrate these points using parameters from a ring current simulation

Charge Renormalization, Effective Interactions, and Thermodynamics of Deionized Colloidal Suspensions

Thermodynamic properties of charge-stabilised colloidal suspensions depend sensitively on the effective charge of the macroions, which can be substantially lower than the bare charge in the case of strong counterion-macroion association. A theory of charge renormalization is proposed, combining an effective one-component model of charged colloids with a thermal criterion for distinguishing between free and associated counterions. The theory predicts, with minimal computational effort, osmotic pressures of deionized suspensions of highly charged colloids in close agreement with large-scale simulations of the primitive model.Comment: 15 pages, 7 figure

Power Balance in Aerodynamic Flows

A control volume analysis of the compressible viscous flow about an aircraft is performed,including integrated propulsors and flow control systems. In contrast to most past analyses which have focused on forces and momentum flow, in particular thrust and drag, the present analysis focuses on mechanical power and kinetic energy flow. The result is a clear identification and quantification of all the power sources, power sinks, and their interactions which are present in any aerodynamic flow. The formulation does not require any separate definitions of thrust and drag, and hence it is especially useful for analysis and optimization of aerodynamic configurations which have tightly integrated propulsion and boundary layer control systems

Integrating Environmental Issues Into Corporate Strategy: A Catalyst for Radical Organizational Innovation

Un étude conduite auprès des entreprises québécoises oeuvrant dans les secteur électrique et électronique permet d'évaluer le niveau d'intégration des préoccupations environnementales dans la stratégie corporative et dans les différentes phases du cycle de développement des produits. Les résultats de l'étude analysent les processus décisionnels sous-jacents ainsi que les bénéfices encourus par les entreprises qui ont privilégié une stratégie environnementale plus intense.This paper presents the results of a study conducted in manufacturing firms operating in the electrical and electronic sectors in Quebec. It investigates the extent to which environmental concerns are integrated into corporate strategy and the entire product development stages. Special attention is paid to the underlying decision process and the benefits derived from being green