Rotationally Inelastic Collisions of CN⁻ with He: Computing Cross Sections and Rates in the Interstellar Medium

A newly calculated ab initio potential energy surface is used to compute collision-driven state-changing cross sections and rate coefficients over a range from 5 to 100 K for CN−(1Σ), the smallest anion detected in the interstellar medium, interacting with He, an abundant species in this environment. We compare our presently computed rate coefficients with those previously published for the similar and important systems CN–He, CN-H2, and CN−–H2 to illustrate the broader network of inelastic, state-changing processes for these four systems. We also discuss the size-scaling effects that occur when changing partners from He to H2. We further analyze the differences in size between collision-driven rate coefficients when going from neutral CN to its anion. All the present results are discussed in detail, to provide accurate and realistic data for chemical networks that wish to include the CN− anion in their modeling of astrochemical environments

Rotational state-changing collisions of C2H− and C2N− anions with He under interstellar and cold ion trap conditions: A computational comparison

We present an extensive range of quantum calculations for the state-changing rotational dynamics involving two simple molecular anions that are expected to play some role in the evolutionary analysis of chemical networks in the interstellar environments, C2H− (X1Σ+) and C2N− (X3Σ−), but for which inelastic rates are only known for C2H−. The same systems are also of direct interest in modeling selective photo-detachment experiments in cold ion traps where the He atoms function as the chief buffer gas at the low trap temperatures. This study employs accurate, ab initio calculations of the interaction potential energy surfaces for these anions, treated as rigid rotors, and the He atom to obtain a wide range of state-changing quantum cross sections and rates at temperatures up to about 100 K. The results are analyzed and compared for the two systems to show differences and similarities between their rates of state-changing dynamics

Collision-driven state-changing efficiency of different buffer gases in cold traps: He(¹S), Ar(¹S) and p-H₂(¹Σ) on trapped CN-(¹Σ)

We employ potential energy surfaces (PES) from ab initio quantum chemistry methods to describe the interaction of the CN^{-}({1}^Σ) molecule, one of the small anions often studied at low temperatures, with other possible gases which can be employed as buffer in cold ion traps: the He and Ar atoms and the p-H-{2} molecule. These PESs are used to calculate from quantum multichannel dynamics the corresponding state-changing rate constants between the populated rotational states of the anion, the latter being in its electronic and vibrational ground states. The different cross sections for the collision-driven quenching and excitation processes at low temperatures are compared and further used to model CN^{-} cooling (de-excitation) efficiency under different trap conditions. The interplay of potential coupling strength and mass-scaling effects is discussed to explain the differences of behaviour among the buffer gases. The advantages of being able to perform collisional cooling at higher trap temperatures when using Ar and p-H_{2} as buffer gases are also discussed

Vibrational quenching of CN− in collisions with He and Ar

The vibrational quenching cross sections and corresponding low-temperature rate constants for the ν = 1 and ν = 2 states of CN− ( 1Σ + ) colliding with He and Ar atoms have been computed ab initio using new three-dimensional potential energy surfaces. Little work has been carried out so far on low-energy vibrationally inelastic collisions for anions with neutral atoms. The cross sections and rates calculated at energies and temperatures relevant for both ion traps and astrochemical modeling are found by the present calculations to be even smaller than those of the similar C− 2 /He and C− 2 /Ar systems, which are in turn of the order of those existing for the collisions involving neutral diatom–atom systems. The implications of our finding in the present case mainly focus on the possible role of small computed rate constants in the dynamics of molecular cooling and the evolution of astrochemical modeling networks

Similarity solutions of Fokker-Planck equation with time-dependent coefficients

In this work, we consider the solvability of the Fokker-Planck equation with both time-dependent drift and diffusion coefficients by means of the similarity method. By the introduction of the similarity variable, the Fokker-Planck equation is reduced to an ordinary differential equation. Adopting the natural requirement that the probability current density vanishes at the boundary, the resulted ordinary differential equation turns out to be integrable, and the probability density function can be given in closed form. New examples of exactly solvable Fokker-Planck equations are presented, and their properties analyzed.Comment: 13 pages, 8 figures. Version to appear in Ann. Phys. Presentation improved. Discussions and figures of easy examples remove

Complete larval development of the hermit crabs Clibanarius aequabilis and Clibanarius erythropus (Decapoda : Anomura : Diogenidae), under laboratory conditions, with a revision of the larval features of genus Clibanarius

The complete larval development (four zoeae and one megalopa) of Clibanarius aequabilis and C. erythropus, reared under laboratory conditions, is described and illustrated. The larval stages of the two northeastern Atlantic Clibanarius species cannot be easily differentiated. Their morphological characters are compared with those of other known Clibanarius larvae. The genus Clibanarius is very homogeneous with respect to larval characters. All Clibanarius zoeae display a broad and blunt rostrum, smooth abdominal segments and an antennal scale without a terminal spine. Beyond the second zoeal stage, the fourth telson process is present as a fused spine, and the uropods are biramous. In the fourth larval stage all species display a mandibular palp. The Clibanarius megalopa presents weakly developed or no ocular scales, symmetrical chelipeds, apically curved corneous dactylus in the second and third pereiopods, and 5-11 setae on the posterior margin of the telson. Apart from the number of zoeal stages, Clibanarius species may be separated, beyond the second zoeal stage, by the telson formula and the morphology of the fourth telson process.info:eu-repo/semantics/publishedVersio

Nonlinear dynamics of Bose-condensed gases by means of a low- to high-density variational approach

We propose a versatile variational method to investigate the spatio-temporal dynamics of one-dimensional magnetically-trapped Bose-condensed gases. To this end we employ a \emph{q}-Gaussian trial wave-function that interpolates between the low- and the high-density limit of the ground state of a Bose-condensed gas. Our main result consists of reducing the Gross-Pitaevskii equation, a nonlinear partial differential equation describing the T=0 dynamics of the condensate, to a set of only three equations: \emph{two coupled nonlinear ordinary differential equations} describing the phase and the curvature of the wave-function and \emph{a separate algebraic equation} yielding the generalized width. Our equations recover those of the usual Gaussian variational approach (in the low-density regime), and the hydrodynamic equations that describe the high-density regime. Finally, we show a detailed comparison between the numerical results of our equations and those of the original Gross-Pitaevskii equation.Comment: 11 pages, 12 figures, submitted to Phys. Rev. A, January 200

Conservation strategies for understanding and combating the primate bushmeat trade on Bioko Island, Equatorial Guinea

© 2017 Wiley Periodicals, Inc. Bioko Island, Equatorial Guinea is among the important places in Africa for the conservation of primates, but a cultural preference for bushmeat and a lack of effective law enforcement has encouraged commercial bushmeat hunting, threatening the survival of the remaining primate population. For over 13 years, we collected bushmeat market data in the Malabo market, recording over 35,000 primate carcasses, documenting “mardi gras” consumption patterns, seasonal carcass availability, and negative effects resulting from government intervention. We also conducted forest surveys throughout Bioko's two protected areas in order to localize and quantify primate populations and hunting pressure. Using these data, we were able to document the significant negative impact bushmeat hunting had on monkey populations, estimate which species are most vulnerable to hunting, and develop ecological niche models to approximate the distribution of each of Bioko's diurnal primate species. These results also have allowed for the identification of primate hotspots, such as the critically important southwest region of the Gran Caldera Scientific Reserve, and thus, priority areas for conservation on Bioko, leading to more comprehensive conservation recommendations. Current and future efforts now focus on bridging the gap between investigators and legislators in order to develop and effectively implement a management plan for Bioko's Gran Caldera Scientific Reserve and to develop a targeted educational campaign to reduce demand by changing consumer attitudes toward bushmeat. Using this multidisciplinary approach, informed by biological, socioeconomic, and cultural research, there may yet be a positive future for the primates of Bioko

Microrreservas marinas artificiales en la línea de costa. Hacia un nuevo modelo de gestión de la biodiversidad en áreas litorales

Recientemente se ha propuesto a la comunidad científica la nueva figura de protección MRMA (Microrreserva Marina Artificial; AMMR en inglés) la cual también ha sido formalmente solicitada a la UNESCO para que esta institución considere reconocerla y consecuentemente, validarla. Se expone la contribución de las MRMAs a la preservación de especies protegidas, particularmente a las consideradas en peligro de extinción que propendan, de forma natural, a establecerse en escolleras y diques de abrigo de instalaciones costeras. Se mencionan las especies protegidas localizadas en las MRMAs, así como sus figuras de protección y disposiciones oficiales que les conciernen. Se exponen criterios generales de designación de MRMAs, posibles vías de solución ante problemas previsibles que puedan surgir (entendimiento entre administraciones, calidad de aguas, medidas de contingencia ante vertidos accidentales, etc.) y se deja entrever las potencialidades de las MRMAs como activo ecológico, medioambiental, urbanístico y educativo, así como el futuro papel que desempeñarán las MRMAs en la gestión del medio litoral y en el campo de la biología de la conservación. Finalmente, se establece una revisión de la legislación actual que más pudiera concernirles, destacándose los aspectos más importantes que en ellas pudieran influir. Al respecto, se destaca que ley 41/2010 de Protección del Medio Marino (Artº 26) establece que podrán formar parte de la red de Áreas Marinas Protegidas “ las áreas protegidas por instrumentos internacionales, sin perjuicio de que su declaración y gestión se ajustará a lo dispuesto en su correspondiente normativa internacional ” por lo que, si la nueva figura de protección “Microrreserva Marina Artificial” consiguiera marchamo UNESCO, aquélla podría incorporarse a la legislación española sin ninguna dificultad especial