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Thermal Instability behind a Shock Wave in HI and Molecular Clouds  [PDF]
Takuhiro Aota,Tsuyoshi Inoue,Yuri Aikawa
Physics , 2013, DOI: 10.1088/0004-637X/775/1/26
Abstract: We performed one-dimensional hydrodynamic simulations with detailed cooling, heating and chemical processes to examine the thermal stability of shocked gas in cold neutral medium (CNM) and molecular clouds. We find that both CNM and molecular clouds can be thermally unstable in the cooling layer behind the shock wave. The characteristic wavelength of the thermal instability ranges from 10^-5 pc to 0.1 pc in the CNM, and from 10^-7 pc to 0.1 pc in the molecular clouds. This coincides with the size of observed tiny scale structures in the CNM and molecular clouds, indicating that the thermal instability in the shocked gas could be a formation mechanism of these tiny structures in the interstellar medium. We have also calculated the e-folding number of the thermal instability to estimate the amplification of the density fluctuation in the shocked gas. Density perturbations in the CNM grow by a factor of exp(5)~150, whereas the perturbations in the molecular clouds grow only by a factor of a few behind a high Mach number shock. The amplification factor is larger at lower densities and higher velocities. Formation of very small-scale structures by thermal instability in shocked gas is more effective in lower densities.
Discovery of 5000 Active Galactic Nuclei behind the Magellanic Clouds  [PDF]
Szymon Kozlowski,Christopher S. Kochanek
Physics , 2009, DOI: 10.1088/0004-637X/701/1/508
Abstract: We show that using mid-IR color selection to find active galactic nuclei (AGN) is as effective in dense stellar fields such as the Magellanic Clouds as it is in extragalactic fields with low stellar densities using comparisons between the Spitzer Deep, Wide-Field Survey data for the NOAO Deep Wide Field Survey Bootes region and the SAGE Survey of the Large Magellanic Cloud. We use this to build high purity catalogs of ~ 5000 AGN candidates behind the Magellanic Clouds. Once confirmed, these quasars will expand the available astrometric reference sources for the Clouds and the numbers of quasars with densely sampled, long-term (>decade) monitoring light curves by well over an order of magnitude and potentially identify sufficiently bright quasars for absorption line studies of the interstellar medium of the Clouds.
Andrzej Teodorczyk
Bulletin of the Institute of Heat Engineering , 1992,
Abstract: A detailed description of the computational model of thermodynamic parameters of the combustion products behind overdriven detonation wave is presented. The model is based on one-dimensional steady flow model with the negligence of body forces, without heat addition and without heat and momentum losses. The model calculates chemical and thermodynamic equilibrium state of the combustion products for the combustion of hydrogen or any hydrocarbon in oxygen. A detailed description of the iterative solution procedure of the model and computer program DEFAST executing this solution are given. Illustrative example of the overdriven detonation wave in stoichiometric hydrogen-oxygen mixture with the initial pressure 0.1 MPa and temperature 293 К is also presented.
A Structuralist Reading of ifeoma Okoye’s Behind the Clouds.
IJ Ogbazi
UJAH: Unizik Journal of Arts and Humanities , 2010,
Abstract: A distinctive quality of humans throughout history has been the continuous quest to unravel meanings out of the multifarious, stupendous, marvelous and immense gifts of nature. Man has continued to search for meaning in life – trying to comprehend both his world and himself better. As a result, the human mind has consistently expressed itself in various forms in order to articulate nature more correctly. Structuralism emanated out of one of those natural currents of human thought. This paper attempts a structuralist reading of Ifeoma Okoye’s Behind The Clouds. It first creates the background by explicating structuralism and its salient features as a critical concept in literary studies. It discusses the structuralist major interests and pre-occupations in the course of interpreting literary works. It then moves on to analyze Behind The Clouds by investigating the operational structures the writer has constructed within the narrative. It explores the systems by highlighting the narrative’s functional units and interpreting their significations and relationships. The paper essentially argues that the narrative is premised on a feminist framework and therefore marked by gender perspectives which are mediated by African culture. It concludes by endorsing the continued relevance of structuralism in the interpretation of literary works even in the 21st century irrespective of the ever-rapid shifts in thought.
The Thermodynamic Models of Molecular Chemical Compound Distribution in the Giant Molecular Clouds Medium  [cached]
Mihail Jurevich Dolomatov,Nadezhda Aleksandrovna Zhuravleva
Applied Physics Research , 2012, DOI: 10.5539/apr.v4n4p149
Abstract: The new equilibrium thermodynamic distribution model of organic and bio-organic substances in giant molecular clouds, including simple organic molecules and amino acids and nucleic acid components was developed. The model basis comprises of the equilibrium composition distribution functions construction by the standard enthalpy of formation and free energy (Helmholtz energy) of formation, which are calculated by means of standard methods. Based on these models the organic molecules resources forecast within the Metagalaxy was performed. The significant amount of biologically active substances existence possibility is indicated: amino acids, nucleobases.
Numerical Study of the Dynamic, Thermodynamic and Microstructural Parameters of Convective Clouds  [PDF]
Vitaly A. Shapovalov, Alexander V. Shapovalov, Boris P. Koloskov, Ruslan Kh. Kalov, Valery N. Stasenko
Natural Science (NS) , 2018, DOI: 10.4236/ns.2018.102006
Abstract: On the basis of a three-dimensional non stationary model of a convective cloud with detailed description of dynamic, thermodynamic and microphysical processes, numerical experiments were conducted to study the formation of parameters of convective clouds under unstable stratification of the atmosphere. Numerical experiments have been carried out to study the formation of convective processes in the atmosphere. The thermo hydrodynamic parameters in the zone of a thunderstorm cloud are determined, and regions with a vortex motion of air are identified. The main flows feeding the convective cloud in the mature stage are determined. Due to the means of visualization, the areas of formation and growth of precipitation particles are identified. In a three-dimensional form, the interaction of dynamic and thermodynamic processes is analyzed. The interaction of fields is manifested in the form of deformation of fields of thermodynamic parameters under the influence of dynamic processes. Trajectories of air streams around a cloud and the trajectories of drops in a cloud are determined. The results of numerical experiments confirm that dynamic processes significantly influence the formation of fields of thermodynamic parameters in the cloud, which also determine the course of microphysical processes and the nature of the growth of precipitation particles.
The Magellanic Quasars Survey. III. Spectroscopic Confirmation of 758 AGNs Behind the Magellanic Clouds  [PDF]
Szymon Kozlowski,Christopher A. Onken,Christopher S. Kochanek,Andrzej Udalski,M. K. Szymanski,M. Kubiak,G. Pietrzynski,I. Soszynski,L. Wyrzykowski,K. Ulaczyk,R. Poleski,P. Pietrukowicz,J. Skowron,M. Meixner,A. Z. Bonanos
Physics , 2013, DOI: 10.1088/0004-637X/775/2/92
Abstract: The Magellanic Quasars Survey (MQS) has now increased the number of quasars known behind the Magellanic Clouds by almost an order of magnitude. All survey fields in the Large Magellanic Cloud (LMC) and 70% of those in the Small Magellanic Cloud (SMC) have been observed. The targets were selected from the third phase of the Optical Gravitational Lensing Experiment (OGLE-III) based on their optical variability, mid-IR and/or X-ray properties. We spectroscopically confirmed 758 (565 LMC and 193 SMC) quasars behind the Clouds, of which 94% (527 LMC and 186 SMC) are newly identified. The MQS quasars have long-term (12 years and growing for OGLE), high-cadence light curves, enabling unprecedented variability studies of quasars. The MQS quasars also provide a dense reference grid for measuring both the internal and bulk proper motions of the Clouds, and 50 quasars are bright enough (I<18 mag) for absorption studies of the interstellar/galactic (ISM/IGM) medium of the Clouds.
Stochastic process behind nonlinear thermodynamic quantum master equation  [PDF]
Hans Christian ?ttinger
Physics , 2010,
Abstract: We propose a piecewise deterministic Markovian jump process in Hilbert space such that the covariance matrix of this stochastic process solves the thermodynamic quantum master equation. The proposed stochastic process is particularly simple because the normalization of the vectors in Hilbert space is preserved only on average. As a consequence of the nonlinearity of the thermodynamic master equation, the construction of stochastic trajectories involves the density matrix as a running ensemble average. We identify a principle of detailed balance and a fluctuation-dissipation relation for our Markovian jump process.
Behind the Clouds: Teaching and Researching Anthropology in Tertiary Institutions in Nigeria
E Anugwom
African Anthropologist , 2007,
Abstract: The paper focuses on teaching and researching of anthropology as a culture centred discipline in Nigeria. It notes that in spite of decades of emergence as a university discipline, anthropology has not been able to break through the negative clouds of colonialism and subjugation to its twin discipline, sociology. Factors responsible for the poor state of teaching and research in anthropology in Nigeria include institutional and structural incapacities and limitations, a curriculum that fails to address both the aspirations of the students and the role of the discipline in national development as well as the inability of the anthropologists themselves to rise up to the dynamic challenges of contemporary Nigerian society. In view of the foregoing, there is need for a serious rethinking and fundamental restructuring of the discipline focusing essentially on the curriculum, professionalism and development values of the discipline. It is only through the above that teaching and researching in anthropology would be more fruitful to both theoretical and practical concerns as an authentic narrative and imagery of African cultural realities.
New quasars behind the Magellanic Clouds. Spectroscopic confirmation of near-infrared selected candidates  [PDF]
Valentin D. Ivanov,Maria-Rosa L. Cioni,Kenji Bekki,Richard de Grijs,Jim Emerson,Brad K. Gibson,Devika Kamath,Jacco Th. van Loon,Andres E. Piatti,Bi-Qing For
Physics , 2015,
Abstract: Quasi--stellar objects (quasars) located behind nearby galaxies provide an excellent absolute reference system for astrometric studies, but they are difficult to identify because of fore- and background contamination. Deep wide--field, high angular resolution surveys spanning the entire area of nearby galaxies are needed to obtain a complete census of such quasars. We embarked on a program to expand the quasar reference system behind the Large and the Small Magellanic Clouds, the Magellanic Bridge, and the Magellanic Stream, connecting the Clouds with the Milky Way. Hundreds of quasar candidates were selected based on their near--infrared colors and variability properties from the ongoing public ESO VISTA Magellanic Clouds survey. A subset of 49 objects was followed up with optical spectroscopy. We confirmed the quasar nature of 37 objects (34 new identifications), four are low redshift objects, three are probably stars, and the remaining three lack prominent spectral features for a secure classification; bona fide quasars, judging from their broad absorption lines are located, as follows: 10 behind the LMC, 13 behind the SMC, and 14 behind the Bridge. The quasars span a redshift range from z~0.5 to z~4.1. Upon completion the VMC survey is expected to yield a total of ~1500 quasars with Y<19.32 mag, J<19.09 mag, and Ks<18.04 mag.
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