Formation of gullies on Mars by debris flows triggered by CO_2 sublimation

Martian gully landforms resemble terrestrial debris flows formed by the action of liquid water and have thus been interpreted as evidence for potential habitable environments on Mars within the past few millennia. However, ongoing gully formation has been detected under surface conditions much too cold for liquid water, but at times in the martian year when a thin layer of seasonal CO_2 frost is present and defrosting above the regolith. These observations suggest that the CO_2 condensation–sublimation cycle could play a role in gully formation. Here we use a thermo-physical numerical model of the martian regolith underlying a CO_2 ice layer and atmosphere to show that the pores beneath the ice layer can be filled with CO_2 ice and subjected to extreme pressure variations during the defrosting season. The subsequent gas fluxes can destabilize the regolith material and induce gas-lubricated debris flows with geomorphic characteristics similar to martian gullies. Moreover, we find that subsurface CO_2 ice condensation, sublimation and pressurization occurs at conditions found at latitudes and slope orientations where gullies are observed. We conclude that martian gullies can result from geologic dry ice processes that have no terrestrial analogues and do not require liquid water. Such dry ice processes may have helped shape the evolution of landforms elsewhere on the martian surface

Competitive suppression of dengue virus replication occurs in chikungunya and dengue co-infected Mexican infants

Abstract Background Co-circulation of dengue virus (DENV) and chikungunya virus (CHIKV) is increasing worldwide but information on the viral dynamics and immune response to DENV-CHIKV co-infection, particularly in young infants, is scant. Methods Blood samples were collected from 24 patients, aged 2 months to 82 years, during a CHIKV outbreak in Mexico. DENV and CHIKV were identified by RT-PCR; ELISA was used to detect IgM and IgG antibodies. CHIKV PCR products were cloned, sequenced and subjected to BLAST analysis. To address serological findings, HMEC-1 and Vero cells were inoculated with DENV-1, DENV-2 and CHIKV alone and in combination (DENV-2-CHIKV and DENV-1-CHIKV); viral titers were measured at 24, 48 and 72 h. Results Nine patients (38%) presented co-infection, of who eight were children. None of the patients presented severe illness. Sequence analysis showed that the circulating CHIKV virus belonged to the Asian lineage. Seroconversion to both viruses was only observed in the four patients five years or older, while the five infants under two years of age only seroconverted to CHIKV. Viral titers in the CHIKV mono-infected cells were greater than in the DENV-1 and DENV-2 mono-infected cells. Furthermore, we observed significantly increased CHIKV progeny and reduction of DENV progeny in the co-infected cells. Conclusions In our population, DENV-CHIKV co-infection was not associated with increased clinical severity. Our in vitro assay findings strongly suggest that the lack of DENV IgG conversion in the co-infected infants is due to suppression of DENV replication by the Asian lineage CHIKV. The presence of maternal antibody and immature immune responses in the young infants may also play a role

Additional file 1: of Competitive suppression of dengue virus replication occurs in chikungunya and dengue co-infected Mexican infants

Figure S1. Co-infection of DENV-2 and CHIKV in Vero cells, analyzed by flow cytometry: The Vero cells were infected in a 6-well plate with DENV-2 or CHIKV at MOI of 0.25 in both mono-infection and co-infection assays and then evaluated at 48 h. The cells were harvested from each plate, then double stained assay and flow cytometry analysis were performed to confirm cells infected with DENV anti-NS5 (X) and infected cells with CHIKV anti-E2 (Y). (TIFF 917 kb

Obras clásicas de náutica y navegación [Recurso electrónico]

Tipo de archivo: TextoPC 486 ; 8 Mb de memoria RAM; MS-DOS 6.0 y Microsoft Windows 3.1 o superior; Espacio libre en disco superior a 10 Mb; Monitor VGA; Lector de CD-ROMTít. Tomado de la etiquetaAlfonso X El Sabio, Rey de Castilla: Tabule Astronomice: Divi Alfonsi regis romanorum e Castelle. Venecia: Petri Liechtenstein, 1518. -- Cedillo Rujaque, Pedro Manuel: Compendio de la Arte de la Navegación. [Sevilla]: [s. n.], 1730. -- Córdoba, Alfonso: Tabulae astronomice Elisabeth regine.Venecia: [s. n.], 1503. -- Cortés y Albacar, Martín: Breve compendio de la sphera y de la arte de navegar [...]. Sevilla: [s. n.], 1551. -- Escalante De Mendoza, Juan De: Ytinerario de Navegación de los mares y tierras occidentales. [Sevilla]: [s. n.], 1575. -- Falero, Francisco: Tratado de la Esphera y del Arte de marear: con el regimiento de las alturas [...]. Sevilla: Cromberger, 1535. -- Fernández De Enciso, Martín: Suma de geographia que trata de todas las partidas y provincias del mundo [...]. Sevilla: Casa de Andrés de Burgos, 1546. -- Fernández De Navarrete, Martín: Disertación sobre la historia de la Naútica, y de las Ciencias Matemáticas que han contribuido a sus progresos entre los españoles. Madrid: Real Academia de Historia, 1846. -- Fernández De Navarrete, Martín: Biblioteca Marítima Española [2 vol.]. Madrid: Imprenta de la Viuda de Calero, 1851. -- Flores, Lázaro De: Arte de Navegar: navegación astronómica [...]. Madrid: Julián de Paredes, impresor de libros, 1673. -- García De Céspedes, Andrés: Regimiento de Navegación [...]. Madrid: En casa de Juan de la Cuesta, 1606. -- García De Palacio, Diego De: Instrucción Nauthica para el buen uso y regimiento de las Naos [...]. Mexico: Pedro Ocharte, 1587. -- González Cabrera Bueno, José: Navegación especulativa y práctica, con la explicación de algunos instrumentos [...]. Manila: Convento de Nuestra Señora de los Ángeles..., 1734. -- González De Ureña, Juan: Delineación de lo tocante al conocimiento del punto de longitud del globo de tierra y agua y de la causa de las crecientes, menguantes del mar [...]. Madrid: Diego Miguel de Peralta, 1740. -- Juan Santacilla, Jorge: Compendio de Navegación para el uso de los cavalleros Guardias-Marinas. Cádiz: Academia de los mismos Cavalleros, 1757. -- Lavanha, Ioão Baptista: Regimiento naútico. Lisboa: Simão Lopez, 1595. -- Medina, Pedro De: Arte de Navegar [...]. Valladolid: [s. n.], 1545. -- Medina, Pedro De: Regimiento de Navegacion. En que se contienen las reglas, declaraciones y auisos del libro del arte de nauegar. Sevilla: [s. n.], 1552. -- Medina, Pedro De: Regimiento de Navegación: contiene las cosas que los pilotos han de saber [...]. Sevilla: [s. n.], 1563. -- Mendoza y Ríos, Josef De: Tratado de navegación [2 vol.]. Madrid: Imprenta Real, 1787. -- Moreno Zabala, Blas José: Práctica de la Navegación. Madrid: Manuel Román, 1732. -- Nájera, Antonio De: Navegación especulativa y práctica, reformadas sus reglas [...]. Lisboa: Pedro Craesbeeck, 1628. -- Porter y Casanate, Pedro: Reparo a errores de la navegación española al excellentissimo señor Don Fadrique de Toledo. Zaragoza: María de la Torre Ossorio, 1634. -- Poza, Andrés De: Hidrografía: la mas curiosa que hasta aquí ha salido [...]. Bilbao: Mathías Mares, 1585. -- Sacrobusto, Ioannes De: Tractado de la Sphera. [Sevilla]: [s. n.], 1545. -- Sánchez Reciente, Juan: Tratado de Navegación theorica y práctica [...]. Sevilla: Imprenta Castellana, 1749. -- Santa Cruz, Alonso: Libro de las longitudes y manera que hasta agora [...]. Sevilla: Tip. Zarzuela, 1921. -- Seixas y Lobera, Francisco De: Teatro naval hidrographico, de los flvxos, y reflvxos [...]. Madrid: Antonio Zafra, 1688. -- Syria, Pedro De: Arte de la verdadera Navegación: en que se trata de la machina [...]. Valencia: Iuan Chrysostomo Garriz, 1602. -- Tornamira, Francisco Vicente: Chronographia y repertorio de los tiempos: a lo moderno, [...]. Pamplona: Thomas Porralis de Sauoya, 1585. -- Zacut, Abraham: Almanach perpetuus [...]. Venecia: [s. n.], 1502. -- Zamorano, Rodrigo: Compendio del Arte de Navegar. Sevilla: [s. n.], 1581

Competitive suppression of dengue virus replication occurs in chikungunya and dengue co-infected Mexican infants

Abstract Background Co-circulation of dengue virus (DENV) and chikungunya virus (CHIKV) is increasing worldwide but information on the viral dynamics and immune response to DENV-CHIKV co-infection, particularly in young infants, is scant. Methods Blood samples were collected from 24 patients, aged 2 months to 82 years, during a CHIKV outbreak in Mexico. DENV and CHIKV were identified by RT-PCR; ELISA was used to detect IgM and IgG antibodies. CHIKV PCR products were cloned, sequenced and subjected to BLAST analysis. To address serological findings, HMEC-1 and Vero cells were inoculated with DENV-1, DENV-2 and CHIKV alone and in combination (DENV-2-CHIKV and DENV-1-CHIKV); viral titers were measured at 24, 48 and 72 h. Results Nine patients (38%) presented co-infection, of who eight were children. None of the patients presented severe illness. Sequence analysis showed that the circulating CHIKV virus belonged to the Asian lineage. Seroconversion to both viruses was only observed in the four patients five years or older, while the five infants under two years of age only seroconverted to CHIKV. Viral titers in the CHIKV mono-infected cells were greater than in the DENV-1 and DENV-2 mono-infected cells. Furthermore, we observed significantly increased CHIKV progeny and reduction of DENV progeny in the co-infected cells. Conclusions In our population, DENV-CHIKV co-infection was not associated with increased clinical severity. Our in vitro assay findings strongly suggest that the lack of DENV IgG conversion in the co-infected infants is due to suppression of DENV replication by the Asian lineage CHIKV. The presence of maternal antibody and immature immune responses in the young infants may also play a role

Administración pública y gobernanza en la segunda década del siglo XXI

La administración pública constituye una de las ciencias sociales que están en constante transformación y una de las que se encuentran íntimamente vinculadas al contexto regional, nacional y mundial, así lo constatan los cambios que ha manifestado en las tres últimas décadas, tanto en el plano nacional como en el continental. En ese lapso hemos sido testigos de la irrupción y el desarrollo de conceptos, enfoques y campos e conocimiento, tales cómo las políticas públicas o ciencias de políticas, la nueva gestión pública, el neoinstitucionalismo y recientemente el de la gobernanza, para citar a los más visibles; todos, sin embargo, indisolublemente asociados a la Administración Pública, ya sea desde una perspectiva disciplinaria o desde su acción como brazo ejecutor del Estado