Stability and decay of Bloch oscillations in presence of time-dependent nonlinearity

We consider Bloch oscillations of Bose-Einstein condensates in presence of a time-modulated s-wave scattering length. Generically, interaction leads to dephasing and decay of the wave packet. Based on a cyclic-time argument, we find---additionally to the linear Bloch oscillation and a rigid soliton solution---an infinite family of modulations that lead to a periodic time evolution of the wave packet. In order to quantitatively describe the dynamics of Bloch oscillations in presence of time-modulated interactions, we employ two complementary methods: collective-coordinates and the linear stability analysis of an extended wave packet. We provide instructive examples and address the question of robustness against external perturbations.Comment: 15 pages, 8 figures. Slightly amended final versio

A Gas Giant Circumbinary Planet Transiting the F Star Primary of the Eclipsing Binary Star KIC 4862625 and the Independent Discovery and Characterization of the two transiting planets in the Kepler-47 System

We report the discovery of a transiting, gas giant circumbinary planet orbiting the eclipsing binary KIC 4862625 and describe our independent discovery of the two transiting planets orbiting Kepler-47 (Orosz et al. 2012). We describe a simple and semi-automated procedure for identifying individual transits in light curves and present our follow-up measurements of the two circumbinary systems. For the KIC 4862625 system, the 0.52+/-0.018 RJup radius planet revolves every ~138 days and occults the 1.47+/-0.08 MSun, 1.7 +/-0.06 RSun F8 IV primary star producing aperiodic transits of variable durations commensurate with the configuration of the eclipsing binary star. Our best-fit model indicates the orbit has a semi-major axis of 0.64 AU and is slightly eccentric, e=0.1. For the Kepler-47 system, we confirm the results of Orosz et al. (2012). Modulations in the radial velocity of KIC 4862625A are measured both spectroscopically and photometrically, i.e. via Doppler boosting, and produce similar results.Comment: 40 pages, 17 figure

Walking Like Dinosaurs: Chickens with Artificial Tails Provide Clues about Non-Avian Theropod Locomotion

Birds still share many traits with their dinosaur ancestors, making them the best living group to reconstruct certain aspects of non-avian theropod biology. Bipedal, digitigrade locomotion and parasagittal hindlimb movement are some of those inherited traits. Living birds, however, maintain an unusually crouched hindlimb posture and locomotion powered by knee flexion, in contrast to the inferred primitive condition of non-avian theropods: more upright posture and limb movement powered by femur retraction. Such functional differences, which are associated with a gradual, anterior shift of the centre of mass in theropods along the bird line, make the use of extant birds to study non-avian theropod locomotion problematic. Here we show that, by experimentally manipulating the location of the centre of mass in living birds, it is possible to recreate limb posture and kinematics inferred for extinct bipedal dinosaurs. Chickens raised wearing artificial tails, and consequently with more posteriorly located centre of mass, showed a more vertical orientation of the femur during standing and increased femoral displacement during locomotion. Our results support the hypothesis that gradual changes in the location of the centre of mass resulted in more crouched hindlimb postures and a shift from hip-driven to knee-driven limb movements through theropod evolution. This study suggests that, through careful experimental manipulations during the growth phase of ontogeny, extant birds can potentially be used to gain important insights into previously unexplored aspects of bipedal non-avian theropod locomotion.</p

From academic to media capital: To what extent does the scientific reputation of universities translate into Wikipedia attention?

Universities face increasing demands to improve their visibility, public outreach, and online presence. There is a broad consensus that scientific reputation significantly increases the attention universities receive. However, in most cases estimates of scientific reputation are based on composite or weighted indicators and absolute positions in university rankings. In this study, we adopt a more granular approach to assessment of universities' scientific performance using a multidimensional set of indicators from the Leiden Ranking and testing their individual effects on university Wikipedia page views. We distinguish between international and local attention and find a positive association between research performance and Wikipedia attention which holds for regions and linguistic areas. Additional analysis shows that productivity, scientific impact, and international collaboration have a curvilinear effect on universities' Wikipedia attention. This finding suggests that there may be other factors than scientific reputation driving the general public's interest in universities. Our study adds to a growing stream of work which views altmetrics as tools to deepen science-society interactions rather than direct measures of impact and recognition of scientific outputs

Do directionality effects influence expected damage? A case study of the 2017 central Mexico earthquake

We analyze the case of a building that collapsed in a multifamily complex of Tlalpan borough in Mexico City during the 19 September 2017 Central Mexico earthquake. Despite having similar materials and similar structural and geometric properties, this was the only building that collapsed in the complex. A structural analysis of the building and a study of the soils’ predominant periods indicated that resonance effects, if any, would not be significant. However, phenomena related to the anomalous performance of buildings in dense urban areas such as geological soil, soil–structure interaction, and soil–city interaction effects were also investigated. A detailed analysis of the directionality of seismic actions recorded at nearby accelerometric stations and of the azimuths of sound and damaged buildings indicates that directionality effects were responsible for the collapse of the building. Subsequently, a set of 58, two-component acceleration records of the earthquake was used to perform a thorough directionality analysis. The results were then compared with the foreseen uniform hazard response spectra and the design spectra in the city. Seismic actions in the city due to this earthquake were stronger than those corresponding to the uniform hazard response spectra. In addition, although design spectra have been significantly improved in the new 2017 Mexican seismic regulations, they were exceeded in 11 of 58 analyzed spectra. In 4 of these 11 cases, the design spectra were exceeded due to directionality effects. These results confirm the necessity of considering directionality effects in damage assessments, strong-motion prediction equations, and design regulations.Peer ReviewedPostprint (author's final draft

Ecologia reprodutiva e história natural de Kinosternon herrerai (Testudines: Kinosternidae) no centro de sua distribuição

México alberga 10 especies endémicas de tortugas de barro del género Kinosternon, pero hace falta información de historia natural para la mayoría de ellas. Aquí describimos algunas generalidades de la ecología reproductiva e historia natural de una población de la tortuga Casquito de Herrera, endémica mexicana, K. herrerai en Hidalgo, México. Las hembras y los machos fueron similares en masa corporal y longitud del carapacho, además, las tortugas más grandes y pesadas se movieron más que aquellas más pequeñas y livianas. El tamaño de la puesta varió de uno a seis huevos, con un promedio de 3.4 ± 1.7, y la puesta de huevos ocurrió a temperaturas ambientales entre 15 and 21°C (x̅ = 18.6°C). El tiempo total de anidamiento (desde la selección del nido hasta la ovoposición) duró ca. 37 min y el periodo de incubación fue de 75 días in situ. Estos resultados mejoran nuestra comprensión de los aspectos de historia natural de las tortugas de barro Kinosternon, que son necesarios para llevar a cabo acciones de conservación para preservar todas sus poblaciones.Mexico harbors 10 endemic species of mud turtles of genus Kinosternon, but natural history information is lacking for most of them. Herein we describe some generalities of the reproductive ecology and natural history of one population of the Mexican endemic, Herrera’s mud turtle, K. herrerai from Hidalgo, Mexico. Females and males were similar in body mass and carapace length. Additionally, larger and heavier turtles moved more than smaller and lighter ones. Clutch size varied from one to six eggs, with an average of 3.4 ± 1.7, and egg laying occurred at environmental temperatures between 15 and 21°C (x̅ = 18.6°C). Total nesting time (from selection of nesting site to oviposition) lasted ca. 37 min, and the incubation period was 75 days in situ. These results enhance our understanding of natural history aspects of Kinosternon mud turtles, which are necessary to carry out conservation actions to preserve all of its populations.O México abriga 10 espécies endêmicas de tartarugas-de-lama do gênero Kinosternon, mas faltam informações sobre a história natural da maioria delas. Aqui, descrevemos algumas generalidades da ecologia reprodutiva e da história natural de uma população de Hidalgo da tartaruga-de-lama-de-herrera, K. herrerai, endêmica do México. As fêmeas e os machos eram semelhantes em termos de massa corporal e comprimento da carapaça. Além disso, as tartarugas maiores e mais pesadas se movimentavam mais do que as menores e mais leves. O tamanho da ninhada variou de um a seis ovos, com uma média de 3,4 ± 1,7, e a postura dos ovos ocorreu em temperaturas ambientais entre 15 e 21°C (x̅ = 18,6°C). O tempo total de nidificação (desde a seleção do local de nidificação até a ovipostura) durou cerca de 37 min, e o período de incubação foi de 75 dias in situ. Esses resultados aumentam nossa compreensão dos aspectos da história natural das espécies de Kinosternon, que são necessários para realizar ações de conservação para preservar todas as suas populações

Sono- and photoelectrocatalytic processes for the removal of ionic liquids based on the 1-butyl-3-methylimidazolium cation

This Accepted Manuscript will be available for reuse under a CC BY-NC-ND license after 24 months of embargo periodIn this work, sono- and photoelectrolysis of synthetic wastewaters polluted with the ionic liquids 1-Butyl-3-methylimidazolium acetate (BmimAc)and chloride (BmimCl)were investigated with diamond anodes. The results were compared to those attained by enhancing bare electrolysis with irradiation by UV light or with the application of high-frequency ultrasound (US). Despite its complex heterocyclic structure, the Bmim+ cation was successfully depleted with the three technologies that were tested and was mainly transformed into four different organic intermediates, an inorganic nitrogen species and carbon dioxide. Regardless of the technology that was evaluated, removal of the heterocyclic ring is much less efficient (and much slower)than oxidation of the counter ion. In turn, the counter ion influences the rate of removal of the ionic liquid cation. Thus, the electrolysis and photoelectrolysis of BmimAc are much less efficient than sonoelectrolysis, but their differences become much less important in the case of BmimCl. In this later case, the most efficient technology is photoelectrolysis. This result is directly related to the generation of free radicals in the solution by irradiation of the electrochemical system with UV light, which contributes significantly to the removal of Bmim+The authors gratefully appreciate financial support from the Spanish MICINN (CTM2016-76197-R and CTM2016-76564-R, European Union (AEI/FEDER, UE) and Consejería de Educación of the CM (REMTAVARES S2013/MAE-2716). I. F. Mena wishes to thank the Spanish MINECO and the ESF for a research gran

Aplicación de la estrategia de mantenimiento RCM2 al sistema de caldera de la unidad 2 de la planta térmica de generación de energía eléctrica Central Cartagena

El presente trabajo, está enfocado a la aplicación de la metodología RCM2 sistema de la caldera de la unidad 2 de la central térmica de Cartagena – Emgesa S.A E.S.P, inicialmente se realiza una descripción del negocio y el proceso de generación, para posteriormente identificar cuáles son los equipos críticos de la central de generación unidad 2 y comparar estos vs la valoración actual del sistema de caldera. Se continúa con un marco conceptual de los temas a tratar en el desarrollo del trabajo, con el propósito de contextualizar al lector y por último, se incluye el análisis pertinente y la aplicación del la táctica de mantenimiento RCM2 al sistema de caldera. La aplicación de la metodología RCM2 sobre el equipo o sistema de caldera unidad 2 nos ayuda a extractar la experiencia de aproximadamente 20 años de los operadores y mantenedores de la central y plasmar de forma efectiva en el plan de mantenimiento de la central. Esta aplicación genera ahorros a largo plazo para la compañía y maximiza la vida útil de los equipos, garantizando la seguridad de las personas y el medio ambiente.Incluye bibliografía, anexos, glosari

Solanum viarum Dunal (Solanaceae), Primer Reporte para Honduras

La maleza invasora Solanum viarum Dunal (Solanaceae) es reportada por primera vez para Honduras. La planta, nativa de Sudam&eacute;rica, fue localizada en un estacionamiento de la Escuela Agr&iacute;cola Panamericana, El Zamorano, Honduras, el 26 de noviembre de 2007.&nbsp; Esta maleza es altamente invasora en pasturas debido a que el ganado puede transportar semillas en su tracto digestivo.DOI: http://dx.doi.org/10.5377/ceiba.v49i1.30