Gases In Cavities Research Articles

Hitna medicinska stanja tokom komercijalnih letova avionom - "Ima li lekara u avionu?"

Almost four billion passengers travel aboard commercial airliners every year. Last year In-flight medical emergencies (IMEs) were relatively common and occurred in a complex environment with limited medical resources. More recent data shows that IMEs occur in one passenger for every 604 flights or 24-130 IMEs for every one million passengers, more often in people over 70 years old. Due to the drop in barometric pressure, there are specific conditions in the aircraft passenger cabin that can affect the occurrence of IMEs. Most importantly it is hypobaric hypoxia, which can lead to the development of hypoxia-related symptoms in chronic patients with respiratory, cardiovascular, and hematological diseases. With reduced barometric pressure gases in body cavities and medical equipment can expand by 30%, this can lead to IMEs in recently operated patients (wound dehiscence, bleeding), middle ear and sinus diseases, subocclusions, and lung problems (pulmonary bulla). Other factors that contribute to the occurrence of IMEs are limited movement (deep vein thrombosis), dry and cold air (dehydration), jet lag, turbulence, and psychological stress. IMEs most commonly involve syncope or near-syncope (32.7%), gastrointestinal (14.8%), respiratory (10.1%), and cardiovascular (7.0%) symptoms. Because of ethical, and in some countries also legal responsibilities, doctor-passengers are a great help in the treatment of IMEs. Emergency landing of the aircraft when an IME occurs happens in an estimated 4.4% of cases. Knowing the influence of the specific ambient conditions in the plane on physiological processes in the body is of great importance for determining the absolute and relative contraindications for flying by plane. Doctor-passengers have an important role in the treatment of IMEs. This work aims to introduce us to the specific ambient conditions in the aircraft cabin and their influence on the physiology of the human body, the most common IMEs that occur under the influence of those conditions, the role of the doctorpassenger as well as the absolute and relative contraindications for flying by plane.

Aerospace registration of hydrocarbon degassing

An active geological study of promising areas for oil and gas is being conducted in areas where geological signs of associated hydrocarbon manifestations are detected. The development of deposits contributes to a developed system of cracks in the surrounding rocks. Fluid supply to fractured reservoirs occurs through the channels of deep faults. Prolonged winter freezing of rocks inhibits the release of gases into the Earth’s atmosphere. The accumulation of hydrocarbon gases in the near-surface cavities creates risks of gas emissions, fires and explosions. Prediction and rapid diagnosis of gas emissions is based on planetary observations from satellites of ozone concentration in the atmosphere. V.L. Syvorotkin experimentally showed a causal relationship between hydrogen degassing and the formation of “Ozone Holes”. Satellite measurements of ozone concentrations in the atmosphere allow daily monitoring of hydrogen degassing sites from the Earth’s surface. The state of the soil surface in the areas of deep degassing is determined by secondary features. These are griffins, soil emissions, ring-shaped structures of gray soil (falling fertility), and hummocks of specific morphology. Such hummocks are formed as a result of the vital activity of “Hydrogen bacteria” and are markers of gas emission on the ground. In combination, methane with hydrogen is capable of detonation at concentrations ranging from 1%. The danger increases in the presence of iron-containing minerals that can catalyze the oxidation reaction. Preventive measures are proposed to prevent the sudden release of flammable gases: by drilling a network of control waste wells with a depth of 100 to 200 meters. Such wells are similar to ventilation wells in areas of coal mining.

Taphonomy of fish concentrations from the Upper Jurassic Solnhofen Plattenkalk of Southern Germany

The density of vertebrate fossils on bedding planes is generally very low in the Upper Jurassic plattenkalks forming the Solnhofen fossil Lagerstatte. There are, however, a few bedding planes where large concentrations of the small fis Leptolepides sprattiformis (BLAINVILLE, 1818) occur. The aim of this paper is to analyse and interpret these f sh concentrations from a taphonomic point of view. For this purpose, the taphonomic features of L. sprattiformis concentrations on three large slabs were semi-quantitatively analysed. The concentrations of individuals on bedding planes are explained as recording local mass mortality events caused by tropical storms that, for short intervals, disrupted the pycnocline which separated hypersaline, oxygen-poor to anoxic bottom waters from normal marine surface waters in the Plattenkalk basins. Mass mortality is supported by tetany features such as gaping jaws, hyperextended branchiostegal rays, and splayed f ns, which occur in the majority of the specimens. The generally excellent preservation of the f sh resulted from lack of postmortem f oatation, rapid burial and/or overgrowth by microbial f lms, and quick re-establishment of the pycnocline with inhospitable conditions on the basin floo. The post-mortem concave-arching of the backbones and various displacements of the vertebral column were most likely caused by varying decay resistance of soft tissues and the pressure of decay gases in the body cavities, respectively. The taphonomic analysis of f sh concentrations can provide very detailed palaeoenvironmental information and serves as an independent line of evidence for palaeoenvironmental reconstructions that complements geochemical and sedimentary data.

Quantum phases of spinful Fermi gases in optical cavities

We explore the quantum phases emerging from the interplay between spin and motional degrees of freedom of a one-dimensional quantum fluid of spinful fermionic atoms, effectively interacting via a photon-mediating mechanism with tunable sign and strength g, as it can be realized in present-day experiments with optical cavities. We find the emergence, in the very same system, of spin- and atomic-density wave ordering, accompanied by the occurrence of superfluidity for g > 0, while cavity photons are seen to drive strong correlations at all g values, with fermionic character for g > 0, and bosonic character for g < 0. Due to the long-range nature of interactions, to infer these results we combine mean-field and exact diagonalization methods supported by bosonization analysis.

Quantum Optical Lattices for Emergent Many-Body Phases of Ultracold Atoms.

Confining ultracold gases in cavities creates a paradigm of quantum trapping potentials. We show that this allows us to bridge models with global collective and short-range interactions as novel quantum phases possess properties of both. Some phases appear solely due to quantum light-matter correlations. Because of a global, but spatially structured, interaction, the competition between quantum matter and light waves leads to multimode structures even in single-mode cavities, including delocalized dimers of matter-field coherences (bonds), beyond density orders as supersolids and density waves.

Thermodynamics of gases in nano cavities

Abstract In nanoscale, gas density is not really homogenous even in thermodynamic equilibrium especially in a region near to the domain boundaries due to the wave character of gas particles. This inhomogeneous region is called quantum boundary layer (QBL) since its thickness goes to zero when the Planck's constant goes to zero. QBL can be neglected and density is assumed to be homogenous as long as thermal de Broglie wavelength (λT) of particles is negligible in comparison with the domain sizes. In nanoscale, however, this condition breaks down and QBL changes the thermodynamic behaviour of gases considerably. In literature, density distribution of a Maxwellian gas has been examined for only a rectangular domain to obtain the analytical results. In this study, density distribution is examined for some regular and irregular domain geometries for which the analytical solution is not possible. It is shown that QBL covers the whole surface of the domain and both thickness and density profile of QBL are independent of the domain geometry. It is concluded that QBL has a universal thickness and density profile for a Maxwellian gas. Furthermore, an effective quantum potential is introduced to explain the inhomogeneous density distribution in thermodynamic equilibrium.

Polaritons and Pairing Phenomena in Bose-Hubbard Mixtures

Motivated by recent experiments on cold atomic gases in ultrahigh finesse optical cavities, we consider the two-band Bose-Hubbard model coupled to quantum light. Photoexcitation promotes carriers between the bands, and we study the interplay between Mott insulating behavior and superfluidity. The model displays a U(1)xU(1) symmetry which supports the coexistence of Mott insulating and superfluid phases and yields a rich phase diagram with multicritical points. This symmetry is shared by several other problems of current experimental interest, including two-component Bose gases in optical lattices and the bosonic BEC-BCS crossover for atom-molecule mixtures induced by a Feshbach resonance. We corroborate our findings by numerical simulations.

On the heat and mass transfer analogy for natural convection of non-dilute binary mixtures of ideal gases in cavities

An extension of a slightly compressible flow model to double-diffusive convection of a binary mixture of ideal gases enclosed in a cavity is presented. The problem formulation is based on a low Mach number approximation and the impermeable surface assumption is not invoked. The main objectives of this paper are the statement of a new problem formulation, and the analysis of some significant results showing the influence of density variations on transient solutions for pure thermal or pure solutal convection. At steady-state, it is shown that the heat and mass transfer analogy may be applied for non-dilute mixtures at parameter ranges larger than those usually considered. To cite this article: H. Sun, G. Lauriat, C. R. Mecanique 337 (2009).

An analysis of the equilibrium adsorption of nitrogen, oxygen, and their mixtures on zeolite NaX at temperatures of from −20 to +30°C

The equilibrium adsorption of oxygen, nitrogen, and their mixtures on zeolite NaX at temperatures of from −20 to +30°C was analyzed by statistical thermodynamics methods on the basis of the data published by Gorbunov et al. [1]. The regularization method was used to calculate the dependence of the internal energy and entropy of pure gases in zeolite cavities on the number of molecules per cavity. This substantially increased the reliability of the functions found. The heat of sorption as a function of the degree of filling and gas mixture composition was analyzed using the dependences obtained and a new algorithm developed for binary adsorption calculations. The trends revealed can be used to model air separation by pressure swing adsorption.

Simulations of the melting of rare-gas inclusions in metals

Molecular dynamics simulations are reported of the melting of small inclusions of rare gases in cavities 10-20 AA in radius in metals containing a few hundred gas atoms. Such systems enable the authors to study the melting phenomena of clusters of atoms constrained by the cavity walls. The authors have looked at the positions of the atoms, the phase diagrams, and the importance of fluctuations for bubbles of different sizes. Melting in these systems takes place over a finite temperature range as in simulations of isolated clusters. The geometric structure factors have been calculated and compared with recent X-ray diffraction measurements of Andersen et al. on krypton inclusions in aluminium. Their inability to reproduce the experimentally observed increase in the transverse diffraction peak width with temperature supports the suggestion of Andersen et al. that this increase is due to a roughening transition of the aluminium facets of the cavities.

Respiratory gas concentrations and temperatures within nest cavities of the northern flicker (Colaptes auratus)

We measured respiratory gas concentrations and air temperatures within nest cavities occupied by the northern flicker. (Colaptes auratus). The means of all measurements of carbon dioxide and oxygen concentrations were 0.37 and 20.42%, respectively. The maximal carbon dioxide level recorded was 2.56%, while the minimal oxygen level was 18.04%. There was a diel cycle in the levels of respiratory gases in nest cavities, with peak carbon dioxide and minimal oxygen levels occurring between 22:00 and 24:00. However, the gaseous conditions within nest cavities remained essentially unchanged throughout the nestling period. Cavity air temperature averaged 21.2 °C, ranging from 10.2 to 33.8 °C, and nearly always exceeded the outside air temperature. The mean difference between inside and outside air temperatures was 7.1 °C and is comparable with those reported in other studies of cavity microenvironments. The elevated cavity temperatures may reduce energy requirements of developing young and also may induce a convective transfer of air between the cavity and free atmosphere that would moderate gaseous conditions within the cavity.

Diffusion controlled breakdown of gases in a rectangular microwave cavity

The boundary-value problem for diffusion-controlled breakdown of gases in microwave cavities is converted to a variational principle for the square of the reciprocal of the ‘effective’ diffusion length. For a rectangular cavity excited in the TEαγ0 mode, the resultant variational principle was minimized by an iterativevariational procedure. This was done using the high-frequency ionization coefficient of Herlin &amp; Brown. However, any other functional dependence on the r.m.s. value of the electric field could have been used for this purpose. The resultant hierarchy of approximations to the variational principle obtained by this iterative-variational procedure for a cavity of square transverse crosssection is applied to the TE110 and TE220 modes of excitation. Adequate convergence is obtained with the first six approximations. Resultant plots of the ratio of the ‘effective’ to the characteristic diffusion length as a function of the Herlin &amp; Brown parameter β, for various ratios of longitudinal to effective transverse cavity dimensions, imply that diffusion loss is greater for the TE220 mode of excitation. Also, from this theoretical investigation it is felt that the first ten approximations to the variational principle should provide adequate convergence for most situations encountered in practice with regard to β, as well as cavity dimensions.

Diffusion-Controlled Breakdown of Gases in Cylindrical Microwave Cavity Excited in the TMn Mode

The boundary-value problem for diffusion-controlled breakdown of gases in microwave cavities is converted to a variational principle for the square of the reciprocal of the ``effective'' diffusion length. For a cylindrical cavity excited in the TM0n0 mode, the resultant variational principle was minimized by an iterative-variational procedure. This was done for an arbitrary functional dependence on the rms value of the electric field. The resultant hierarchy of approximations to the variational principle obtained by this iterative-variational procedure was applied to a cylindrical cavity excited in the TM010 and TM020 modes, respectively, using the high-frequency ionization coefficient of Herlin and Brown. Calculations were carried out and plots of the ratio of the effective to the characteristic diffusion length as a function of the Herlin and Brown parameter β are given for various ratios of cavity depth to radius. From this theoretical investigation, it is felt that the first ten approximations to the variational principle are sufficient to provide adequate convergence for any situation encountered in practice with regard to β as well as cavity dimensions.

Intracrystalline sorption by synthetic mordenites

The inclusion of a number of representative molecules (He, Ne, Ar, Kr, Xe; H 2 , O 2 , N 2 ; n -C 4 H 10 , i -C 4 H 10 , C 6 H 6 , neo-C 5 H 12 ) has been studied for Na- and H- forms of synthetic mor-denite. Filling of the intracrystalline volume in Na-mordenite is limited to some of the permanent gases, and at 25 °C is very incomplete for n -C 4 H 10 . In contrast, in H-mordenite the main channels are nearly filled by molecules as large as benzene and neo-pentane. However, sorption in the sets of small cavities or pockets which line the main channels in mordenite is limited to molecules smaller than n -butane. Heats of inclusion have been determined as functions of amounts sorbed for the inert and the permanent gases. Calculations have been made of heats of inclusion of the rare gases in the small cavities, and compared with observed initial heats in H-mordenite. As in the case of gas hydrates (Barrer &amp; Ruzicka 1962) the London (1930) approximation to the dispersion energy, combined with the Lennard-Jones 12:6 potential, gives better results than the approximation of Kirkwood (1932) and Muller (1936). Estimates have also been made of equilibrium constants of rare gases in the small cavities, which give a reasonable correlation with the measured Henry’s law adsorption constants. Conclusions are drawn from certain of the results about the separability of intracrystalline and inter-particle sorption. There is also reason to believe that stacking faults are not the cause of the molecular sieve character shown by the synthetic Na-mordenite.

鑄鐵の生長に就て

The growth of gray cast iron during repeated heatings and coolings has been studied by many investigators and three different theories were maintained as follows: (1) The permanent elongation is produced by the expansion of the occluded gases in the metal at high temperatures; that is, the gases in minute cavities expand at high temperatures and make the content of the cavities permanently larger, thus giving a great porosity and apparent growth to the metal.(2) The growth of gray cast iron is principally shown to be the result of the oxidations of carbon, silicon as well as iron. (3) The growth of gray cast iron during the first heating through 700°C to 800°C is partly attributable to the decomposition of cementite and the next continuous growth during heating and cooling through the A1 range is the effect of the differential expansion at different microportions of the same casting, numerous fissures or cavities being thus formed, in the region of graphite flakes; and in an oxidising attmosphere, the growth is accelerated by oxides formed and filling the fissures or cavities during Ar1 transformation, thus the effect of oxidation on the growth of cast iron is indirect. In this investigation, the effects of some elements as carbon, silicon, manganese, phosphorus, tin and chromium upon the growth of gray cast iron repeatedly heated were studied and also the growth on black heart malleable cast iron was observed. From these results of the experiments, the authour was discussed the above three theories on the growth of cast iron and given some complements to his previous theory explained in the above term (3)