A search for hydrogenated fullerenes in fullerene-containing planetary nebulae

Detections of C60 and C70 fullerenes in planetary nebulae (PNe) of the Magellanic Clouds and of our own Galaxy have raised the idea that other forms of carbon such as hydrogenated fullerenes (fulleranes like C60H36 and C60H18), buckyonions, and carbon nanotubes, may be widespread in the Universe. Here we present VLT/ISAAC spectra (R ~600) in the 2.9-4.1 microns spectral region for the Galactic PNe Tc 1 and M 1-20, which have been used to search for fullerene-based molecules in their fullerene-rich circumstellar environments. We report the non-detection of the most intense infrared bands of several fulleranes around ~3.4-3.6 microns in both PNe. We conclude that if fulleranes are present in the fullerene-containing circumstellar environments of these PNe, then they seem to be by far less abundant than C60 and C70. Our non-detections together with the (tentative) fulleranes detection in the proto-PN IRAS 01005+7910 suggest that fulleranes may be formed in the short transition phase between AGB stars and PNe but they are quickly destroyed by the UV radiation field from the central star.Comment: Accepted for publication in Astronomy & Astrophysics (7 pages, 3 figures, and 3 Tables

Large quantum nonlinear dynamic susceptibility of single-molecule magnets

The nonlinear dynamical response of Mn$_{12}$ single-molecule magnets is experimentally found to be very large, quite insensitive to the spin-lattice coupling constant, and displaying peaks reversed with respect to classical superparamagnets. It is shown that these features are caused by the strong field dependence of the relaxation rate due to the detuning of energy levels between which tunneling takes place. The nonlinear susceptibility technique, previously overlooked, is thus proposed as a privileged probe to ascertain the occurrence of quantum effects in mesoscopic magnetic systems.Comment: 4 pages, 4 figure

Hypoxic Cell Waves around Necrotic Cores in Glioblastoma: A Biomathematical Model and its Therapeutic Implications

Glioblastoma is a rapidly evolving high-grade astrocytoma that is distinguished pathologically from lower grade gliomas by the presence of necrosis and microvascular hiperplasia. Necrotic areas are typically surrounded by hypercellular regions known as "pseudopalisades" originated by local tumor vessel occlusions that induce collective cellular migration events. This leads to the formation of waves of tumor cells actively migrating away from central hypoxia. We present a mathematical model that incorporates the interplay among two tumor cell phenotypes, a necrotic core and the oxygen distribution. Our simulations reveal the formation of a traveling wave of tumor cells that reproduces the observed histologic patterns of pseudopalisades. Additional simulations of the model equations show that preventing the collapse of tumor microvessels leads to slower glioma invasion, a fact that might be exploited for therapeutic purposes.Comment: 29 pages, 9 figure

Venus Atmosphere Profile from a Maximum Entropy Principle

The variational method with constraints recently developed by Verkley and Gerkema to describe maximum-entropy atmospheric profiles is generalized to ideal gases but with temperature-dependent specific heats. In so doing, an extended and non standard potential temperature is introduced that is well suited for tackling the problem under consideration. This new formalism is successfully applied to the atmosphere of Venus. Three well defined regions emerge in this atmosphere up to a height of $100 km$ from the surface: the lowest one up to about $35 km$ is adiabatic, a transition layer located at the height of the cloud deck and finally a third region which is practically isothermal.Comment: 6 pages, 3 figure

Economy and Environmental Problems in the Mexican Coastal States

A canonical correspondence analysis (CCA) for environmental and economic variables was performed for 17 Mexican coastal states. The ordination method allowed us to identify three groups, namely hydroelectric energy generation (I), pollution (II) and harbours (III), which were associated to different human activities. Furthermore, CCA is efficient to help us generate hypotheses for future research. It is therefore advised that CCA should be used for routine analyses into economics.Coastal States of Mexico, Canonical Correspondence Analysis, Diversity Index, Economic Development, Environmental Variables.

El estudio de la asociación genética dentro del modelo psicobiológico de personalidad de Zuckerman

Following Zuckerman's psychobiological personality model, a series of genetic association hypotheses between some polymorphisms of Serotonin, Testosterone, Dopamine, MAO-A and COMT, and three temperamental traits (Impulsive Unsocialized Sensation Seeking, Neuroticism, and Extroversion-Sociability) were tested. In order to surpass previous limitations of this kind of studies: 1) the measurement of the phenotype was improved by using eight personality scales, and 2) some statistical analyses were conducted to test conjointly the effects of the considered polymorphisms. 252 participants from two samples (147 male inmates, and 105 male healthy volunteers) were analyzed. A tendency in the theoretical expected direction is reported when several polymorphisms are considered conjointly. The discussion section recommends applying more integrative frameworks to explore the complex paths from genetics to behavior.Partiendo del modelo de personalidad psicobiológico de Zuckerman se planean una serie de hipótesis de la asociación genética de diferentes polimorfismos de la serotonina, testosterona, dopamina, MAO-A y COMT, y tres rasgos temperamentales (Búsqueda impulsiva de sensaciones no socializada, Neuroticismo y Extroversión-sociabilidad). Para superar limitaciones anteriores de este tipo de estudios: 1) la medida fenotípica se mejoró usando ocho escalas para medir los constructos de personalidad, y 2) algunos análisis estadísticos fueron usados para estudiar conjuntamente los efectos de los polimorfismos. La muestra analizada se compuso de 252 participantes de dos muestras de hombres, una de 147 presos y otra de 105 voluntarios sanos. Los resultados informan que cuando se consideran conjuntamente todos los polimorfismos estu-diados se observa una tendencia en la dirección de las hipótesis formuladas. La sección de la discusión recomienda aplicar variables más integradoras para explorar los caminos complejos de las genéticas a la conducta

A new species of \u3cem\u3eAnanteris\u3c/em\u3e Thorell, 1891 from Cordillera Central in Colombia, with some notes on the taxonomy of the genus (Scorpiones: Buthidae)

A new species of Ananteris Thorell, 1891 is herein described from a single locality placed in the Cordillera Central of Colombia, which represents the first record of this genus for Tolima department. This new taxon exhibits several singular features, and apparently represents a relict population inside an urbanized area. Also, some aspects on the taxonomy of the genus are briefly discussed, and its diagnosis is emended. With this addition, the total of Ananteris species described from Colombia is raised to six

Undecidability as solution to the problem of measurement: fundamental criterion for the production of events

In recent papers we put forth a new interpretation of quantum mechanics, colloquially known as ``the Montevideo interpretation''. This interpretation is based on taking into account fundamental limits that gravity imposes on the measurement process. As a consequence one has that situations develop where a reduction process is undecidable from an evolution operator. When such a situation is achieved, an event has taken place. In this paper we sharpen the definition of when and how events occur, more precisely we give sufficient conditions for the occurrence of events. We probe the new definition in an example. In particular we show that the concept of undecidability used is not ``FAPP'' (for all practical purposes), but fundamental.Comment: 10 pages, contributed to the Castagnino Festschrif