Light bending near non-asymptotically flat black holes

The gravitational deflection of light is a crucial test for modified gravity. A few years ago, Gibbons and Werner introduced a definition of the deflection angle based on the Gauss-Bonnet theorem. A related idea was proposed by Arakida for defining the deflection angle in non-asymptotically flat spacetimes We revisit this idea in the Kottler geometry and in a non-asymptotically flat solution to Horndeski gravity. Our analytic and numerical calculations show that a triangular array of laser beams can be designed so that the proposed definition of deflection angle is sensitive to a cosmological constant, whose contribution is amplified by the black hole mass. Moreover, we find that near the photon sphere, the deflection angle in the Horndeski solution is similar to its Schwarzschild counterpart, and we confirm that the shadows seen by a static observer would be identical. Our results offer insights that could be useful for designing future theoretical or experimental investigations aimed to detect sources of curvature in the universe.Comment: 32+1 pages, 6 figures, 2 table

Strong lensing by DHOST black holes

The deflection of light in the strong field limit is an important test for alternative theories of gravity. However, solutions for the metric that allow for analytic computations are not always available. We implement a hybrid analytic-numerical approximation to determine the deflection angle in static, spherically symmetric spacetimes. We apply this to a set of numerical black hole solutions within the class of theories known as Degenerate Higher Order Scalar-tensor Theories. Comparing our results to a more time consuming full numerical integration, we find that we can accurately describe the deflection angle for light rays passing at arbitrary distances from the photon sphere with a combination of two analytic-numerical approximations. Furthermore, we find a range of parameters where our DHOST black holes predict strong lensing effects whose size is comparable with the uncertainty in the properties of the supermassive black hole in M87 reported by the Event Horizon Telescope, showing that strong lensing is a viable alternative to put constraints on these models

Análisis de Error de Ráfaga Introducidos en un Tráfico Múltiple de los Protocolos TCP Reno, Cubic, Westwood y Vegas en un Modelo de Topología Híbrida

This paper explores the behavior shown by the protocols TCP Reno, Cubic, Vegas and Westwood in presence of errors in bursts occurred in multiple traffic over a hybrid topology. The development is based on the analysis of case studies, where it starts with a mixed topology of two wired and two wireless nodes, with two flows of the same variant of the TCP protocol, subsequently increasing the number of nodes until reaching 8 wired nodes behaving as senders and 8 wireless nodes as receivers. In all cases only one of these flows suffers a burst error and through the tests we analyze how the flow recovers from the burst. For this study, behavioral tests were carried out using the NS-2 network simulator, on a hybrid topology (wired and wireless), also incorporating burst errors of different lengths, typical of wireless links.Este artículo explora el comportamiento mostrado por los protocolos TCP Reno, Cubic, Vegas y Westwood en presencia de errores en ráfagas ocurridas en el tráfico múltiple sobre una topología híbrida. El desarrollo se basa en el análisis de estudios de caso, comenzando con una topología mixta de dos nodos cableados y dos inalámbricos, con dos flujos de una misma variante del protocolo TCP, aumentando el número de nodos hasta alcanzar 8 nodos cableados emisores y 8 nodos inalámbricos receptores. En todos los casos, solo uno de estos flujos sufre un error de ráfaga y, a través de las pruebas, analizamos cómo se recupera el flujo de la ráfaga. Para este estudio, las pruebas de comportamiento se llevaron a cabo utilizando el simulador de red NS-2, en una topología híbrida (cableada e inalámbrica), que también incorporó errores de ráfaga de diferentes longitudes, típicos de los enlaces inalámbricos.Facultad de Informátic

Análisis de Error de Ráfaga Introducidos en un Tráfico Múltiple de los Protocolos TCP Reno, Cubic, Westwood y Vegas en un Modelo de Topología Híbrida

This paper explores the behavior shown by the protocols TCP Reno, Cubic, Vegas and Westwood in presence of errors in bursts occurred in multiple traffic over a hybrid topology. The development is based on the analysis of case studies, where it starts with a mixed topology of two wired and two wireless nodes, with two flows of the same variant of the TCP protocol, subsequently increasing the number of nodes until reaching 8 wired nodes behaving as senders and 8 wireless nodes as receivers. In all cases only one of these flows suffers a burst error and through the tests we analyze how the flow recovers from the burst. For this study, behavioral tests were carried out using the NS-2 network simulator, on a hybrid topology (wired and wireless), also incorporating burst errors of different lengths, typical of wireless links.Este artículo explora el comportamiento mostrado por los protocolos TCP Reno, Cubic, Vegas y Westwood en presencia de errores en ráfagas ocurridas en el tráfico múltiple sobre una topología híbrida. El desarrollo se basa en el análisis de estudios de caso, comenzando con una topología mixta de dos nodos cableados y dos inalámbricos, con dos flujos de una misma variante del protocolo TCP, aumentando el número de nodos hasta alcanzar 8 nodos cableados emisores y 8 nodos inalámbricos receptores. En todos los casos, solo uno de estos flujos sufre un error de ráfaga y, a través de las pruebas, analizamos cómo se recupera el flujo de la ráfaga. Para este estudio, las pruebas de comportamiento se llevaron a cabo utilizando el simulador de red NS-2, en una topología híbrida (cableada e inalámbrica), que también incorporó errores de ráfaga de diferentes longitudes, típicos de los enlaces inalámbricos.Facultad de Informátic

Anti-malarial activity and HS-SPME-GC-MS chemical profiling of Plinia cerrocampanensis leaf essential oil

Plinia cerrocampanensis is an endemic plant of Panama. The leaf essential oil of this plant has shown antibacterial activity. However, anti-malarial activity and chemical profiling by HS-SPME-GC-MS of this essential oil have not been reported before. Anti-malarial activity of the essential oil (EO) was evaluated in vitro against chloroquine-sensitive HB3 and chloroquine-resistant W2 strains of Plasmodium falciparum. Synergistic effect of chloroquine and the EO on parasite growth was evaluated by calculating the combination index. A methodology involving headspace solid phase microextraction and gas chromatography-mPlinia cerrocampanensis is an endemic plant of Panama. The leaf essential oil of this plant has shown antibacterial activity. However, anti-malarial activity and chemical profiling by HS-SPME-GC-MS of this essential oil have not been reported before. Anti-malarial activity of the essential oil (EO) was evaluated in vitro against chloroquine-sensitive HB3 and chloroquine-resistant W2 strains of Plasmodium falciparum. Synergistic effect of chloroquine and the EO on parasite growth was evaluated by calculating the combination index. A methodology involving headspace solid phase microextraction and gas chromatography-

Anti-malarial activity and HS-SPME-GC-MS chemical profiling of Plinia cerrocampanensis leaf essential oil

Plinia cerrocampanensis is an endemic plant of Panama. The leaf essential oil of this plant has shown antibacterial activity. However, anti-malarial activity and chemical profiling by HS-SPME-GC-MS of this essential oil have not been reported before. Anti-malarial activity of the essential oil (EO) was evaluated in vitro against chloroquine-sensitive HB3 and chloroquine-resistant W2 strains of Plasmodium falciparum. Synergistic effect of chloroquine and the EO on parasite growth was evaluated by calculating the combination index. A methodology involving headspace solid phase microextraction and gas chromatography-mPlinia cerrocampanensis is an endemic plant of Panama. The leaf essential oil of this plant has shown antibacterial activity. However, anti-malarial activity and chemical profiling by HS-SPME-GC-MS of this essential oil have not been reported before. Anti-malarial activity of the essential oil (EO) was evaluated in vitro against chloroquine-sensitive HB3 and chloroquine-resistant W2 strains of Plasmodium falciparum. Synergistic effect of chloroquine and the EO on parasite growth was evaluated by calculating the combination index. A methodology involving headspace solid phase microextraction and gas chromatography-

Actividad antimicrobiana de bacterias marinas aisladas del Golfo de México

Currently there is a need for new antibiotics with an alternative mode of action and new chemical structures. Bacterial pathogens are gradually becoming more resistant to conventional antibiotics, generating an emergence of infectious diseases and they are becoming a great problem in the field of public health. In this study, seven different isolated bacteria were obtained from offshore seawater and sediment of the Gulf of Mexico from Campeche, Mexico. They were substance producers which inhibit growth of human pathogens like Staphylococcus aureus and Pseudomonas aeruginosa and one of them was a polymer producer on peptone and glucose culture. They were characterized phenotipically by means of morphological techniques and physiologically by conventional tests. Four of them were Gram-positive bacteria and the Scanning Electron Microscope analysis revealed their size between 0.6 - 1.5 µm. One of seven marine strains, Gram negative, yellow pigmented, slightly curved rods, was identified as Pseudoalteromonas sp. on the analysis of the gen16S rRNA sequence.Hoy en día existe la necesidad de encontrar antibióticos con nuevas estructuras químicas y modos de acción alternativos. Se ha observado que bacterias patógenas comunes progresivamente desarrollan resistencia al tratamiento con antibióticos tradicionales, surgiendo y resurgiendo enfermedades infecciosas que generan un gran problema en salud pública. En este estudio, se obtuvieron siete colonias bacterianas pigmentadas de agua de mar y de sedimento marino procedente de las costas de Campeche, México. Las colonias aisladas produjeron sustancias que inhibieron el crecimiento de bacterias patógenas a humanos como Staphylococcus aureus and Pseudomonas aeruginosa. Las bacterias marinas fueron caracterizadas fenotípicamente de acuerdo a su morfología microscópica y por pruebas fisiológicas convencionales. Cuatro de los aislados resultaron ser bacterias Gram positivas y las otras tres fueron Gram negativas. Cuando se observaron por microscopía electrónica de barrido, su tamaño aproximado fue entre 0,6 - 1,5 µm. Uno de los aislados fue una colonia amarilla con bacilos cortos Gram negativos y ligeramente curvos, identificado por la secuencia del gen16S rRNA como Pseudoalteromonas sp

Análisis de la equidad intra-protocolo de las variantes de TCP Reno, CUBIC, Vegas y Westwood cuando se producen errores en ráfaga en una red heterogénea

En el presente trabajo se estudia el papel que juega la interacción de múltiples flujos de una misma variante de TCP, analizando como el mecanismo de control de flujo resuelve la distribución de los recursos de la red, en particular del ancho de banda disponible. Para esto, se utiliza un modelo simple en el simulador NS2 y se analiza de qué forma los flujos de datos llegan a un estado de equilibrio sobre el canal, teniendo en cuenta que en la actualidad las redes presentan escenarios que implican tener trayectos heterogéneos. Planteado ese modelo se tomaron evidencias para distintas versiones de TCP completándose un análisis comparativo.Sociedad Argentina de Informática e Investigación Operativ