Características comparativas da estabilidade térmica dos ácidos húmicos dos sapropels da região OB do meio e sul da bacia de OB-Irtysh da Sibéria Ocidental

The study of humic acids has more than a century history with a natural and logical evolution of focuses on their development processes, composition and properties. Despite the considerable material accumulated to date, the nature of this group of organic compounds still has not been sufficiently studied. We have decided that the distinctive features of hydrochemical and hydrobiological factors in the formation of sapropels of the studied lakes will be reflected in the thermal stability of humic acids extracted from them. Thermal analysis of humic acids extracted from the upper layers of bottom sediments of lakes of Kondinsk district of Khanty-Mansi Autonomous okrug and Barabinsk district of the Novosibirsk region, made using modern synchronous thermal analysis, has been resulted in the article. According to the obtained data, it is observed that with increasing of maximum temperature of the thermal effect, the value of Z decreases (the ratio of the mass loss in the low temperature space to the mass loss in the high temperature space), which indicates the increase in thermal stability, formation of humic acids. The indicator of humic acids of sapropels of the Kondinsk lakes varies from 0,56 to 0,67, and these intervals are much wider from 0.45 to 0.75 in the Barabinsk lakes. According to thermogravimetric analysis the only statement of changes in chemical structure is possible, and the direction of the process can be assumed taking into account the data of the structural chemistry in combination with other spectral and chemical analysis methods.El estudio de los ácidos húmicos tiene más de un siglo de historia con una evolución natural y lógica de enfoques en sus procesos de desarrollo, composición y propiedades. A pesar del considerable material acumulado hasta la fecha, la naturaleza de este grupo de compuestos orgánicos aún no ha sido suficientemente estudiada. Hemos decidido que las características distintivas de los factores hidroquímicos e hidrobiológicos en la formación de sapropeles de los lagos estudiados se reflejarán en la estabilidad térmica de los ácidos húmicos extraídos de ellos. El resultado del análisis térmico de los ácidos húmicos extraídos de las capas superiores de los sedimentos del fondo de los lagos del distrito de Kondinsk de Okrug Autónomo de Khanty-Mansi y el distrito de Barabinsk de la región de Novosibirsk, realizado con el moderno análisis térmico sincrónico, ha sido publicado. Según los datos obtenidos, se observa que al aumentar la temperatura máxima del efecto térmico, el valor de Z disminuye (la relación entre la pérdida de masa en el espacio de baja temperatura y la pérdida de masa en el espacio de alta temperatura), lo que indica El aumento de la estabilidad térmica, formación de ácidos húmicos. El indicador de ácidos húmicos de sapropeles de los lagos de Kondinsk varía de 0,56 a 0,67, y estos intervalos son mucho más amplios de 0,45 a 0,75 en los lagos de Barabinsk. Según el análisis termogravimétrico, la única declaración de cambios en la estructura química es posible, y la dirección del proceso se puede asumir teniendo en cuenta los datos de la química estructural en combinación con otros métodos de análisis espectral y químico.O estudo dos ácidos húmicos tem mais de um século de história com uma evolução natural e lógica de focos em seus processos de desenvolvimento, composição e propriedades. Apesar do considerável material acumulado até hoje, a natureza desse grupo de compostos orgânicos ainda não foi suficientemente estudada. Decidimos que as características distintivas dos fatores hidroquímicos e hidrobiológicos na formação de sapropelas dos lagos estudados serão refletidas na estabilidade térmica dos ácidos húmicos extraídos dos mesmos. Análises térmicas de ácidos húmicos extraídos das camadas superiores de sedimentos de fundo dos lagos do distrito de Kondinsk, distrito de Okrug e autônomo de Khanty-Mansi, na região de Novosibirsk, usando análise térmica síncrona moderna, resultaram no artigo. De acordo com os dados obtidos, observa-se que com o aumento da temperatura máxima do efeito térmico, o valor de Z diminui (a razão da perda de massa no espaço de baixa temperatura para a perda de massa no espaço de alta temperatura), o que indica o aumento da estabilidade térmica, formação de ácidos húmicos. O indicador de ácidos húmicos de sapropels dos lagos de Kondinsk varia de 0,56 a 0,67, e estes intervalos são muito mais largos de 0,45 a 0,75 nos lagos de Barabinsk. De acordo com a análise termogravimétrica, a única declaração de alterações na estrutura química é possível, e a direção do processo pode ser assumida levando em conta os dados da química estrutural em combinação com outros métodos de análise espectral e química

Stationary relativistic jets

In this paper we describe a simple numerical approach which allows to study the structure of steady-state axisymmetric relativistic jets using one-dimensional time-dependent simulations. It is based on the fact that for narrow jets with vz≈cvz≈c the steady-state equations of relativistic magnetohydrodynamics can be accurately approximated by the one-dimensional time-dependent equations after the substitution z=ctz=ct. Since only the time-dependent codes are now publicly available this is a valuable and efficient alternative to the development of a high-specialised code for the time-independent equations. The approach is also much cheaper and more robust compared to the relaxation method. We tested this technique against numerical and analytical solutions found in literature as well as solutions we obtained using the relaxation method and found it sufficiently accurate. In the process, we discovered the reason for the failure of the self-similar analytical model of the jet reconfinement in relatively flat atmospheres and elucidated the nature of radial oscillations of steady-state jets

Magnetic field structure of relativistic jets without current sheets

We present an analytical class of equilibrium solutions for the structure of relativistic sheared and rotating magnetized jets that contain no boundary current sheets. We demonstrate the overall dynamical stability of these solutions and, most importantly, a better numerical resistive stability than the commonly employed force-free structures which inevitably require the presence of dissipative surface currents. The jet is volumetrically confined by the external pressure, with no pressure gradient on the surface. We calculate the expected observed properties of such jets. Given the simplicity of these solution we suggest them as useful initial conditions for relativistic jet simulations.Comment: 13 pages, 13 figures, Accepted by MNRA

X-ray and Radio Interactions in the Cores of Cooling Flow Clusters

We present high resolution ROSAT x-ray and radio observations of three cooling flow clusters containing steep spectrum radio sources at their cores. All three systems exhibit strong signs of interaction between the radio plasma and the hot intracluster medium. Two clusters, A133 and A2626, show enhanced x-ray emission spatially coincident with the radio source whereas the third cluster, A2052, exhibits a large region of x-ray excess surrounding much of the radio source. Using 3-D numerical simulations, we show that a perturbed jet propagating through a cooling flow atmosphere can give rise to amorphous radio morphologies, particularly in the case where the jet was ``turned off'' and allowed to age passively. In addition, the simulated x-ray surface brightness produced both excesses and deficits as seen observationally.Comment: 25 pages, 10 figures, accepted for publication in A

Mutations in human genes that increase the risk for severe influenza infection

The system of genetic control of innate immune responses to influenza infection and gene function allows for the development of systemic treatment of influenza with a focus on the phenotype of mutations based on individual genetic susceptibility to severe disease and/or the development of complications.The system of genetic control of innate immune responses to influenza infection and gene function allows for the development of systemic treatment of influenza with a focus on the phenotype of mutations based on individual genetic susceptibility to severe disease and/or the development of complications

A Case for Renewed Activity in the Giant Radio Galaxy J0116-473

We present ATCA radio observations of the giant radio galaxy J0116-473 at 12 and 22 cm wavelengths in total intensity and polarization. The images clearly reveal a bright inner-double structure within more extended edge-brightened lobe emission. The lack of hotspots at the ends of the outer lobes, the strong core and the inner-double structure with its edge-brightened morphology lead us to suggest that this giant radio galaxy is undergoing a renewed nuclear activity: J0116-473 appears to be a striking example of a radio galaxy where a young double source is evolving within older lobe material. We also report the detection of a Mpc-long linear feature which is oriented perpendicular to the radio axis and has a high fractional polarization.Comment: 25 pages, 10 figures, appeared in 2002 ApJ, 565, 25

The effects of spin-down on the structure and evolution of pulsar wind nebulae

We present high resolution spherically symmetric relativistic magnetohydrodynamical simulations of the evolution of a pulsar wind nebula inside the free expanding ejecta of the supernova progenitor. The evolution is followed starting from a few years after the supernova explosion and up to an age of the remnant of 1500 years. We consider different values of the pulsar wind magnetization parameter and also different braking indices for the spin-down process. We compare the numerical results with those derived through an approximate semi-analytical approach that allows us to trace the time evolution of the positions of both the pulsar wind termination shock and the contact discontinuity between the nebula and the supernova ejecta. We also discuss, whenever a comparison is possible, to what extent our numerical results agree with former self-similar models, and how these models could be adapted to take into account the temporal evolution of the system. The inferred magnetization of the pulsar wind could be an order of magnitude lower than that derived from time independent analytic models.Comment: 11 pages, 7 figures, Accepted for publication on A&

Comparison of Radio Observations and Numerical Simulations of the Radio Lobes of Cygnus A

We present a comparison of radio observations of the archetypal powerful radio galaxy Cygnus A and 2-D numerical hydrodynamical simulations. We characterize some global trends in the observed radio properties and compare them with the properties of a simulated radio source. The numerical results are the following. Jets propagating in a constant density atmosphere will decelerate with time. Thus, the estimated dynamical age of the source will be greater than the actual age of the source. For a source similar to Cygnus A the difference will be about a factor of 2. The second moment gives an accurate representation of the "true" width of the simulated source. The Gaussian FWHM tends to be about 40% larger than the true width and can be systematically in error if the surface brightness exhibits multiple peaks. We suggest that the ratio of the Gaussian FWHM to the second moment may be a diagnostic of the emissivity profile in the lobes. The simulations can qualitatively reproduce the overall observed morphology and the behavior of the cross-sections in surface brightness, the decline in surface brightness with distance from the hot spots, and the width of the lobes. This suggests that the 2-D simulations give a reasonable representation of the properties of Cygnus A.Comment: the larger figures are available as gif

MHD models of Pulsar Wind Nebulae

Pulsar Wind Nebulae (PWNe) are bubbles or relativistic plasma that form when the pulsar wind is confined by the SNR or the ISM. Recent observations have shown a richness of emission features that has driven a renewed interest in the theoretical modeling of these objects. In recent years a MHD paradigm has been developed, capable of reproducing almost all of the observed properties of PWNe, shedding new light on many old issues. Given that PWNe are perhaps the nearest systems where processes related to relativistic dynamics can be investigated with high accuracy, a reliable model of their behavior is paramount for a correct understanding of high energy astrophysics in general. I will review the present status of MHD models: what are the key ingredients, their successes, and open questions that still need further investigation.Comment: 18 pages, 5 figures, Invited Review, Proceedings of the "ICREA Workshop on The High-Energy Emission from Pulsars and their Systems", Sant Cugat, Spain, April 12-16, 201

Extragalactic Relativistic Jets and Nuclear Regions in Galaxies

Past years have brought an increasingly wider recognition of the ubiquity of relativistic outflows (jets) in galactic nuclei, which has turned jets into an effective tool for investigating the physics of nuclear regions in galaxies. A brief summary is given here of recent results from studies of jets and nuclear regions in several active galaxies with prominent outflows.Comment: 5 pages; contribution to ESO Astrophysical Symposia, "Relativistic Astrophysics and Cosmology", eds. B. Aschenbach, V. Burwitz, G. Hasinger, B. Leibundgut (Springer: Heidelberg 2006