A Nonextensive Approach to Bose-Einstein Condensation of Trapped Interacting Boson Gas

In the Bose-Einstein condensation of interacting atoms or molecules such as ⁸⁷Rb, ²³Na and ⁷Li, the theoretical understanding of the transition temperature is not always obvious due to the interactions or zero point energy which cannot be exactly taken into account. The S-wave collision model fails sometimes to account for the condensation temperatures. In this work, we look at the problem within the nonextensive statistics which is considered as a possible theory describing interacting systems. The generalized energy U _q and the particle number N _q of boson gas are given in terms of the nonextensive parameter q. q>1 (q<1) implies repulsive (attractive) interaction with respect to the perfect gas. The generalized condensation temperature T _cq is derived versus T _c given by the perfect gas theory. Thanks to the observed condensation temperatures, we find q≈0.1 for ⁸⁷Rb atomic gas, q≈0.95 for ⁷Li and q≈0.62 for ²³Na. It is concluded that the effective interactions are essentially attractive for the three considered atoms, which is consistent with the observed temperatures higher than those predicted by the conventional theory.      

MCM-41 deposition on alumina ceramic foams

Alumina-based macro-porous ceramic foams were successfully coated with MCM-41 meso-porous materials using an in-situ one step hydrothermal synthesis. Low H₂O/NaOH ratio in the starting mixture leads to a not uniform deposition of the meso-porous materials. Using higher H₂O/NaOH ratio and two cycles of deposition, a CF with a continuous and thick layer of well-ordered MCM-41 material coating was produced.     

大型长廊阻抗式调压室三维非线性数值分析

采用三维非线性有限元分析方法，结合泸定水电站调压室的开挖，模拟了大型长廊阻抗式调压室开挖和支护的施工过程。利用改进的锚杆单元模拟支护结构中锚杆的作用。分别从围岩稳定和衬砌结构的受力特性两个方面对调压室进行了分析，给出了围岩支护和结构设计的基本分析方法．可为类似工程提供借鉴。     

Compound Size Effect in Composite Beams with Softening Connectors.?I: Energy Approach

The size effect on the nominal strength of steel-concrete composite beams caused by shear failures of connectors such as welded studs is analyzed by two different approaches: (1) In this paper (Part I) by a fracture type analysis of the energy release caused by propagation of the zone of failed connectors along the beam; and (2) in a companion paper (Part II) by a direct solution of the load-deflection diagrams from the differential equations of beam bending theory. The former can capture the large size asymptotic size effect and yields simple formulas suitable for design, whereas the latter can provide the solution for small beam sizes for which the connector failure zone is not much shorter than the span. The force-slip diagram of the connectors exhibits postpeak softening, which engenders an energetic size effect on the nominal strength of the connector. If the connectors are geometrically scaled with the beam, the size effect in the shear failure of connectors (mesoscale) is superimposed on the size effect due to propagation of the zone of connector failures along the beam (macroscale), producing in the beam as a whole a compound size effect that is stronger than in linear elastic failure mechanics. If the connector sizes and the interface area per connector are not scaled with the overall dimensions of the composite beam, the size effect law proposed by Ba?ant in 1984 is applicable. Comparisons with available test results are presented in Part II.     

Strict regulation of c-Raf kinase levels is required for early organogenesis of the vertebrate inner ear

Regulation of organogenesis involves a dynamic balance of the mechanisms regulating cell division, differentiation and death. Here we have investigated the pattern of expression of c-Raf kinase in the inner ear during early developmental stages and the consequences of manipulating c-Raf levels by misexpression of c-raf viral vectors in organotypic cultures of otic vesicle explants. We found that otic vesicles expressed c-Raf and its level remained constant during embryonic days 2 and 3 (E2-E3). c-Raf activity was increased in response to insulin like growth factor-I (IGF-I) and the activation by IGF-I of the c-Raf kinase pathway was a requirement to turn on cell proliferation in the otic vesicle. Overexpression of c-raf in E2.5 explants increased the proliferative response to low serum and IGF-I and blocked differentiation induced by retinoic acid. The increase in c-Raf levels also prevented nerve growth factor (NGF)-dependent induction of programmed cell death. Consistent with these results, the expression of a dominant negative c-Raf mutant potentiated retinoic acid action and decreased the rate of cell proliferation. We conclude that a strict control of c-Raf levels is essential for the co-ordination of the biological processes that operate simultaneously during early inner ear development.     

How to visualize the spider mite silk?

Tetranychus urticae (Acari: Tetranychidae) is a phytophagous mite that forms colonies of several thousand individuals. Like spiders, every individual produces abundant silk strands and is able to construct a common web for the entire colony. Despite the importance of this silk for the biology of this worldwide species, only one previous study suggested how to visualize it. To analyze the web structuration, we developed a simple technique to dye T. urticae'silk on both inert and living substrates. Fluorescent brightener 28 (FB) (Sigma F3543) diluted in different solvents at different concentrations regarding the substrate was used to observe single strands of silk. On glass lenses, a 0.5% dimethyl sulfoxide solution was used and on bean leaves, a 0.1% aqueous solution. A difference of silk deposit was observed depending the substrate: rectilinear threads on glass lenses and more sinuous ones on bean leaves. This visualizing technique will help to carry out future studies about the web architecture and silk used by T. urticae. It might also be useful for the study of other silk-spinning arthropods. Microsc. Res. Tech. 2009. © 2009 Wiley-Liss, Inc.     

Fracture Mechanics of ASR in Concretes with Waste Glass Particles of Different Sizes

Using waste glass as an aggregate in concrete can cause severe damage because of the alkali-silica reaction (ASR) between the alkali in the cement paste and the silica in the glass. Recent accelerated 2-week tests, conducted according to ASTM C 1260, revealed that the damage to concrete caused by expansion of the ASR gel, which is manifested by strength reduction, depends in these tests strongly on the size of the glass particles. As the particle size decreases, the tensile strength first also decreases, which is expected because of the surface-to-volume ratio of the particles, and thus their chemical reactivity increases. However, there exists a certain worst (pessimum) size below which any further decrease of particle size improves the strength, and the damage becomes virtually nonexistent if the particles are small enough. The volume dilatation due to ASR is maximum for the pessimum particle size and decreases with a further decrease of size. These experimental findings seem contrary to intuition. This paper proposes a micromechanical fracture theory that explains the reversal of particle size effect in the accelerated 2-week test by two opposing mechanisms: (1) The extent of chemical reaction as a function of surface area, which causes the strength to decrease with a decreasing particle size; and (2) the size effect of the cracks produced by expansion of the ASR gel, which causes the opposite. The pessimum size, which is about 1.5 mm, corresponds to the case where the effects of both mechanisms are balanced. For smaller sizes the second mechanism prevails, and for sizes <0.15 mm no adverse effects are detectable. Extrapolation of the accelerated test (ASTM C 1260) to real structures and full lifetimes will require coupling the present model with the modeling of the reaction kinetics and diffusion processes involved.     

Dependence of pancreatic amylase secretion on the amylolytic activity of the duodenal contents

Pancreatic amylase secretion stimulated by intraduodenal administration of acidified (up to pH 2.0) hydrolysine was evaluated in acute experiments on dogs. Bicarbonates, protein, amylase, lipase, and proteinase were assayed in the juice. Renal excretion of amylase and amylolytic activity of blood plasma were determined during the experiment. Intraduodenal administration of pancreatic amylase decreased amylase secretion by the pancreas and did not influence the secretion of bicarbonates and other enzymes. Administration into the duodenum of amylase with its inhibitor eliminated the effect of selective inhibition of pancreatic amylase secretion. Amylolytic activity of the blood was unchanged, while the renal amylase excretion increased.     

Continuous Relaxation Spectrum for Concrete Creep and its Incorporation into Microplane Model M4

Efficient numerical finite-element analysis of creeping concrete structures requires the use of Kelvin or Maxwell chain models, which are most conveniently identified from a continuous retardation or relaxation spectrum, the spectrum in turn being determined from the given compliance or relaxation function. The method of doing that within the context of solidification theory for creep with aging was previously worked out by Ba?ant and Xi in 1995 but only for the case of a continuous retardation spectrum based on the Kelvin chain. The present paper is motivated by the need to incorporate concrete creep into the recently published Microplane Model M4 for nonlinear triaxial behavior of concrete, including tensile fracturing and behavior under compression. In that context, the Maxwell chain is more effective than the Kelvin chain, because of the kinematic constraint of the microplanes used in M4. The paper shows how to determine the continuous relaxation spectrum for the Maxwell chain, based on the solidification theory for aging creep of concrete. An extension to the more recent microprestress-solidification theory is also outlined and numerical examples are presented.