Hydrological controls on river network connectivity

This study proposes a probabilistic approach for the quantitative assessment of reach- and network-scale hydrological connectivity as dictated by river flow space–time variability. Spatial dynamics of daily streamflows are estimated based on climatic and morphological features of the contributing catchment, integrating a physically based approach that accounts for the stochasticity of rainfall with a water balance framework and a geomorphic recession flow analysis. Ecologically meaningful minimum stage thresholds are used to evaluate the connectivity of individual stream reaches, and other relevant network-scale connectivity metrics. The framework allows a quantitative description of the main hydrological causes and the ecological consequences of water depth dynamics experienced by river networks. The analysis shows that the spatial variability of local-scale hydrological connectivity is strongly affected by the spatial and temporal distribution of climatic variables. Depending on the underlying climatic settings and the critical stage threshold, loss of connectivity can be observed in the headwaters or along the main channel, thereby originating a fragmented river network. The proposed approach provides important clues for understanding the effect of climate on the ecological function of river corridors

O conceito de existência em Martin Heidegger e Ernst Tugendhat

This work aims to describe and to reflect on the concepts of existence of the philosophers Martin Heidegger and Ernst Tugendhat. To do so, I expose, in the Introduction, a brief and broad overview of the discussion of the concept of existence in contemporary philosophy and I present the methodology of the present work, based on the concepts of word, concept, problem and philosophical position. In Chapter One, on Heidegger, I try to show that, in Being and Time, we can find three concepts of existence [1] existence as the whole of Dasein's being; [2] existence as one of the constituent moments of care; and [3] existence as ex-sistence. Such conceptual change – and this is my hypothesis – do not reveal an inaccuracy of the hermeneutic-phenomenological method, as stated by some philosophers of analytic branch, but one of its particularities which allows an intersubjective semantic control. I still discuss, in this chapter, the formulations of the concept of existence of the “philosophers of existence”, such as Kierkegaard, Jaspers and Sartre, in order to achieve a better comprehension of Heidegger’s own proposal. In the Second Chapter, I have, as an initial hypothesis, that Tugendhat formulates, in a group of particular works, three concepts of existence: [I] existence as identification; [II] temporal existence; and [III] existence as relation to one own self, and that in all of them there is an intention to comply with the fundamental principle of analytic philosophy. In the end, I try to demonstrate that the third concept can cause doubts about an alignment with this principle. Finally, in the Final Considerations, I return again to the discussion of the methodology of the work, now with the hypothesis of a programmatic attempt of a dialogue between the two philosophical positions and how this could be accomplished.I expose further that the main motivation for us using the concept of existence in contemporary philosophy is the purpose of a philosophical account of the existence of human existence as a unique, irreplaceable and which it must be carried each time by each one. This brings thereby the need for the redevelopment of other concepts, like, for example, truth, freedom, reason, transcendence, time, among others.Este trabalho tem por objetivo explicitar e refletir sobre os conceitos de existência dos filósofos Martin Heidegger e Ernst Tugendhat. Para tanto, exponho, na Introdução, um breve e amplo panorama da discussão sobre o conceito de existência na filosofia contemporânea e apresento a metodologia do trabalho, baseada nos conceitos de palavra, conceito, problema e posição filosófica. No Primeiro Capítulo, sobre Heidegger, procuro demonstrar que, em Ser e Tempo, podemos encontrar três conceitos de existência [1] existência como o todo do ser do Dasein; [2] existência como um dos momentos constitutivos do cuidado; e [3] existência como ex-sistência. Tais modificações conceituais, e esta é minha hipótese, não revelam uma imprecisão do método fenomenológico-hermenêutico, como afirmam certos filósofos de vertente analítica, mas uma de suas particularidades que permite um controle semântico intersubjetivo. Discuto, ainda neste capítulo, as formulações do conceito de existência dos “filósofos da existência”, Kierkegaard, Jaspers e Sartre, com o objetivo de alcançar uma melhor compreensão da proposta do próprio Heidegger. No Segundo Capítulo, tenho como hipótese inicial que Tugendhat elabora, em um grupo de obras específico, três conceitos de existência: [I] existência como identificação; [II] existência temporal; e [III] existência como relacionar-se consigo mesmo, sendo que, em todos eles, há uma pretensão de estar de acordo com o princípio fundamental da filosofia analítica. Ao final, mostrarei que o terceiro conceito pode provocar dúvidas a respeito de uma concordância com tal princípio. Por fim, nas Conclusões Finais, volto, novamente, à discussão da metodologia do trabalho, agora com a hipótese programática de uma tentativa de diálogo entre ambas as posições filosóficas e como isto poderia ser realizado. Como resultado, exponho, ainda, que a principal motivação para utilizarmos o conceito de existência na filosofia contemporânea é o intuito de uma descrição filosófica da existência do ser humano como uma existência singular, finita, insubstituível e que precisa ser levada a cada momento por cada um. Isto traz, por conseqüência, a necessidade de re-elaboração de outros conceitos fundamentais, como, por exemplo, o de verdade, liberdade, transcendência, tempo, entre outros

Relativistic Effects on the Appearance of a Clothed Black Hole

For an accretion disk around a black hole, the strong relativistic effects affect every aspect of the radiation from the disk, including its spectrum, light-curve, and image. This work investigates in detail how the images of a thin disk around a black hole will be distorted, and what the observer will see from different viewing angles and in different energy bands.Comment: 4 pages, 5 figures. Based on the poster presented at the Sixth Pacific Rim Conference on Stellar Astrophysics (Xi'an, China, July 11-17, 2002). Color versions of figures are given separatel

Accretion Disk Illumination in Schwarzschild and Kerr Geometries: Fitting Formulae

We describe the methodology and compute the illumination of geometrically thin accretion disks around black holes of arbitrary spin parameter $a$ exposed to the radiation of a point-like, isotropic source at arbitrary height above the disk on its symmetry axis. We then provide analytic fitting formulae for the illumination as a function of the source height $h$ and the black hole angular momentum $a$. We find that for a source on the disk symmetry axis and $h/M > 3$, the main effect of the parameter $a$ is allowing the disk to extend to smaller radii (approaching $r/M \to 1$ as $a/M \to 1$) and thus allow the illumination of regions of much higher rotational velocity and redshift. We also compute the illumination profiles for anisotropic emission associated with the motion of the source relative to the accretion disk and present the fractions of photons absorbed by the black hole, intercepted by the disk or escaping to infinity for both isotropic and anisotropic emission for $a/M=0$ and $a/M=0.99$. As the anisotropy (of a source approaching the disk) increases the illumination profile reduces (approximately) to a single power-law, whose index, $q$, because of absorption of the beamed photons by the black hole, saturates to a value no higher than $q \gtrsim 3$. Finally, we compute the fluorescence Fe line profiles associated with the specific illumination and compare them among various cases.Comment: 26 pages, 21 b/w figures, accepted for publication in the Astrophysical Journal as of 4/16/200

Processing and qualitative data analysis with views aeromagnetic exploration type hydrothermal deposits lode gold - La Rioja province, Argentina

La interpretación de los datos aeromagnéticos regionales de las Sierras de Chepes y Ulapes- Las Minas requirió el uso de técnicas relevantes de realce para definir con precisión rasgos geológicos que se relacionan con la presencia de yacimientos auríferos en la región. Los nuevos mapas magnéticos: del campo anómalo reducido al polo, filtro pasa alto, derivadas verticales, derivadas fraccionales, amplitud de señal analítica y fase de la señal analítica fueron usados para delinear zonas de cizalla, que en esta región representan el principal control metalogenético.Fil: Gimenez, Mario Ernesto. Universidad Nacional de San Juan. Facultad de Ciencias Exactas, Fisicas y Naturales. Instituto Geofi­sico Sismologico Volponi; ArgentinaFil: Fanton, Gerardo Oscar. Universidad Nacional de San Juan. Facultad de Ciencias Exactas, Fisicas y Naturales. Instituto Geofi­sico Sismologico Volponi; Argentina. Consejo Nacional de Investigaciones Cientificas y Tecnicas. Centro Cientifico Tecnologico San Juan; ArgentinaFil: Martinez, Myriam Patricia. Universidad Nacional de San Juan. Facultad de Ciencias Exactas, Fisicas y Naturales. Instituto Geofisico Sismologico Volponi; Argentin

The relativistic Iron K-alpha line from an accretion disc onto a static non-baryonic compact object

This paper continues the study of the properties of an accretion disc rotating around a non-baryonic (assumed super-massive) compact object. This kind of objects, generically known as boson stars, were earlier proposed as a possible alternative scenario to the existence of super-masive black holes in the center of every galaxy. A dilute boson star has also been proposed as a large part of the non-baryonic dark matter, flattening galactic rotational velocities curves. In this contribution, we compute the profile of the emission lines of Iron; its shape has been for long known as a useful diagnosis of the space-time geometry. We compare with the case of a Schwarzschild black hole, concluding that the differences are observationally distinguishable.Comment: 14 pages, 7 figure

Extremal energy shifts of radiation from a ring near a rotating black hole

Radiation from a narrow circular ring shows a characteristic double-horn profile dominated by photons having energy around the maximum or minimum of the allowed range, i.e. near the extremal values of the energy shift. The energy span of a spectral line is a function of the ring radius, black hole spin, and observer's view angle. We describe a useful approach to calculate the extremal energy shifts in the regime of strong gravity. Then we consider an accretion disk consisting of a number of separate nested annuli in the equatorial plane of Kerr black hole, above the innermost stable circular orbit (ISCO). We suggest that the radial structure of the disk emission could be reconstructed using the extremal energy shifts of the individual rings deduced from the broad wings of a relativistic spectral line.Comment: 9 pages, 5 figures, ApJ accepte

Optics in the Schwarzschild space-time

Realistic modelling of radiation transfer in and from variable accretion disks around black holes requires the solution of the problem: find the constants of motion and equation of motion of a light-like geodesic connecting two arbitrary points in space. Here we give the complete solution of this problem in the Schwarzschild space-time.Comment: 14 pages, 10 figures, type C orbits added, analytic solutions for time of flight of photons for all 3 types of orbits adde