Proposed satellite position determination systems and techniques for Geostationary Synthetic Aperture Radar

This paper proposes two different calibration techniques for Geostationary Synthetic Aperture Radar (GEOSAR) missions requiring a high precision positioning, based on Active Radar Calibrators and Ground Based Interferometry. The research is enclosed in the preparation studies of a future GEOSAR mission providing continuous monitoring at continental scale.Peer ReviewedPostprint (author's final draft

First isolation and further characterization of enteropathogenic Escherichia coli (EPEC) O157:H45 strains from cattle

BACKGROUND: Enteropathogenic Escherichia coli (EPEC), mainly causing infantile diarrhoea, represents one of at least six different categories of diarrheagenic E. coli with corresponding distinct pathogenic schemes. The mechanism of EPEC pathogenesis is based on the ability to introduce the attaching-and-effacing (A/E) lesions and intimate adherence of bacteria to the intestinal epithelium. The role and the epidemiology of non-traditional enteropathogenic E. coli serogroup strains are not well established. E. coli O157:H45 EPEC strains, however, are described in association with enterocolitis and sporadic diarrhea in human. Moreover, a large outbreak associated with E. coli O157:H45 EPEC was reported in Japan in 1998. During a previous study on the prevalence of E. coli O157 in healthy cattle in Switzerland, E. coli O157:H45 strains originating from 6 fattening cattle and 5 cows were isolated. In this study, phenotypic and genotypic characteristics of these strains are described. Various virulence factors (stx, eae, ehxA, astA, EAF plasmid, bfp) of different categories of pathogenic E. coli were screened by different PCR systems. Moreover, the capability of the strains to adhere to cells was tested on tissue culture cells. RESULTS: All 11 sorbitol-positive E. coli O157:H45 strains tested negative for the Shiga toxin genes (stx), but were positive for eae and were therefore considered as EPEC. All strains harbored eae subtype α1. The gene encoding the heat-stable enterotoxin 1 (EAST1) was found in 10 of the 11 strains. None of the strains, however, carried ehx A genes. The capability of the strains to adhere to cells was shown by 10 strains harbouring bfp gene by localized adherence pattern on HEp-2 and Caco-2 cells. CONCLUSION: This study reports the first isolation of typical O157:H45 EPEC strains from cattle. Furthermore, our findings emphasize the fact that E. coli with the O157 antigen are not always STEC but may belong to other pathotypes. Cattle seem also to be a reservoir of O157:H45 EPEC strains, which are described in association with human diseases. Therefore, these strains appear to play a role as food borne pathogens and have to be considered and evaluated in view of food safety aspects

Serotypes, intimin variants and other virulence factors of eae positive Escherichia coli strains isolated from healthy cattle in Switzerland. Identification of a new intimin variant gene (eae-η2)

BACKGROUND: Enteropathogenic Escherichia coli (EPEC) and Shigatoxin-producing Escherichia coli (STEC) share the ability to introduce attaching-and-effacing (A/E) lesions on intestinal cells. The genetic determinants for the production of A/E lesions are located on the locus of enterocyte effacement (LEE), a pathogenicity island that also contains the genes encoding intimin (eae). This study reports information on the occurrence of eae positive E. coli carried by healthy cattle at the point of slaughter, and on serotypes, intimin variants, and further virulence factors of isolated EPEC and STEC strains. RESULTS: Of 51 eae positive bovine E. coli strains, 59% were classified as EPEC and 41% as STEC. EPEC strains belonged to 18 O:H serotypes, six strains to typical EPEC serogroups. EPEC strains harbored a variety of intimin variants with eae-β1 being most frequently found. Moreover, nine EPEC strains harbored astA (EAST1), seven bfpA (bundlin), and only one strain was positive for the EAF plasmid. We have identified a new intimin gene (η2) in three bovine bfpA and astA-positive EPEC strains of serotype ONT:H45. STEC strains belonged to seven O:H serotypes with one serotype (O103:H2) accounting for 48% of the strains. The majority of bovine STEC strains (90%) belonged to five serotypes previously reported in association with hemolytic uremic syndrom (HUS), including one O157:H7 STEC strain. STEC strains harbored four intimin variants with eae-ε1 and eae-γ1 being most frequently found. Moreover, the majority of STEC strains carried only stx1 genes (13 strains), and was positive for ehxA (18 strains) encoding for Enterohemolysin. Four STEC strains showed a virulence pattern characteristic of highly virulent human strains (stx2 and eae positive). CONCLUSION: Our data confirm that ruminants are an important source of serologically and genetically diverse intimin-harboring E. coli strains. Moreover, cattle have not only to be considered as important asymptomatic carriers of O157 STEC but can also be a reservoir of EPEC and eae positive non-O157 STEC, which are described in association with human diseases

Prevalence and characteristics of non-O157 shiga toxin-producing Escherichia coli (STEC) and Escherichia coli O157 in fattening pigs at slaughter in Switzerland

Feacal samples from 630 slaughtered healthy pigs were examined with the aim: (i) to monitor the shedding of non-O157 STEC and E. coli O157; (ii) to further characterize isolated strains; and (iii) to discuss the results obtained with their relevance to food safety. The percentage of the 630 samples testing positive for STEC by polymerase chain reaction was 22.2%. The 32 isolated stx positive strains (31 sorbitol-positive) belonged to non-O157 STEC and comprised ten serotypes. Stx1, stx2, and both toxin genes were detected in 3%, 97%, and 0% of strains. Among stx2-positive strains, 29 were positive for stx2e, one for stx2/stx2e, and one for stx2c/stx2e. The percentage of the 630 samples testing positive for E. coli O157 by polymerase chain reaction was 7.5%. The 31 isolated rfbE PCR positive strains tested negative for stx genes. However, four strains harbored eae and were classified as EPEC

Multiscale modeling for complex chemical systems: Highlights about the Nobel Prize in Chemistry 2013

The Nobel Prize in Chemistry 2013 was awarded jointly to Martin Karplus, Michael Levitt and Arieh Warshel for the development of multiscale models for complex chemical systems. From the simplest approximation of molecular mechanics (MM) to quantum mechanics (QM), computational techniques allow simulating a great variety ofchemical systems. Combined QM/MM methodologies, however, are the best consensus for treating complex biological systems. Herein we review the theoretical basis of QM/MM methods and their applications during the last twenty years.

Catolicismo y nación en el Centenario.

En el marco del avance del proceso de secularización y a medida que fue arreciando el enfrentamiento entre católicos y anticlericales, los temas de la nación y del nacionalismo poco a poco fueron incorporándose de manera cada vez más destacada a la agenda en disputa. Desde una perspectiva fuertemente esencialista, que buscaba imbricar de manera indisoluble las nociones de "Dios y Patria", la Iglesia Católica y sus distintos actores procuraron durante ese largo período terciar en forma protagónica en las controversias suscitadas a propósito de la forja polémica de la conciencia nacional de los uruguayos. Se trataba de una vieja discusión que hundía sus raíces en el siglo XIX pero que por múltiples motivos acrecentó su voltaje y su significación a partir del 900 y muy especialmente durante los fastos del Centenario. Las páginas que siguen apuntan a registrar en forma más sistemática los itinerarios de las posturas de distintos actores del catolicismo uruguayo de la época en torno al tema, desde los tiempos de Mons. Jacinto Vera hasta los años de las fiestas centenarias, auténticamente decisivos para el tema que nos ocupa. Como telón de fondo, por detrás de estas trayectorias católicas cuya consideración se privilegia, aparecen los ecos de los debates suscitados por la acción reformista del "primer batllismo", los conflictos interpartidarios a propósito de las ideas de nación y del uso público del pasado, así como las tensiones emergentes de un proceso de secularización complejo y diverso, que por cierto no culminó en todas sus facetas con la separación constitucional de la Iglesia y del Estado a partir de 1919

¿CÓMO ENSEÑAR UNA QUÍMICA INORGÁNICA MENOS MEMORÍSTICA Y DESCRIPTIVA?

La Química Inorgánica es una de las ramas fundamentales de la Química, que con el mismo nombre, sus contenidos se modelan e imparten como asignatura o disciplina en muchos centros de estudios universitarios. La experiencia ha demostrado, que en ocasiones, los estudiantes no comprenden la esencia de esta disciplina, porque no se enseña a partir de determinadas regularidades que son de vital importancia para poder entender la misma. En este trabajo se presenta un modelo didáctico para enseñar la Química Inorgánica, que tiene como fundamento dos regularidades a tener en cuenta para estructurar e impartir los contenidos de esta disciplina. Se explica, el fundamento del modelo didáctico para el estudio de la Química Inorgánica con un enfoque menos descriptivo. Las ideas para elaborar la propuesta tienen su origen, a partir de la determinación de las tendencias históricas de la enseñanza de esta disciplina en diferentes universidades nacionales e internacionales,PALABRAS CLAVE: Modelo Didáctico; Regularidades; Química Inorgánica; metodología de la enseñanza.HOW TO TEACH AN INORGANIC CHEMISTRY LESS MEMORISTIC AND DESCRIPTIVE?ABSTRACTInorganic Chemistry is one of the fundamental branches of Chemistry, which witch the same name, its contents are modeled and taught ac subject is discipline in many university centers. The experience has demonstrated that in some occasions, the students don´t understand the essence of this discipline because it isn´t taught taking into account some regularities that are considered very important to understand it. In this work the author presents a didactic model for teaching Inorganic Chemistry which has as main ground two regularities to take into account for structuring and teaching the content of this discipline. Otherwise, it is explained the main reference of the didactic model, with a less descriptive approach. The suggestions for the elaboration of the proposal have their bases on the historical tendencies of the teaching of this discipline in national as well as international universities.KEYWORDS: Didactic model; Regularities; Inorganic Chemistry; teaching methodology

Radiative transfer and spectroscopic databases: A line-sampling Monte Carlo approach

Issu de : Eurotherm conference n° 105 - Computational thermal radiation in participating media V, Albi, FRANCE, 1-3 April 2015International audienceDealing with molecular-state transitions for radiative transfer purposes involves two successive steps that both reach the complexity level at which physicists start thinking about statistical approaches: (1) constructing line-shaped absorption spectra as the result of very numerous state-transitions, (2) integrating over optical-path domains. For the first time, we show here how these steps can be addressed simultaneously using the null-collision concept. This opens the door to the design of Monte Carlo codes directly estimating radiative transfer observables from spectroscopic databases. The intermediate step of producing accurate high-resolution absorption spectra is no longer required. A Monte Carlo algorithm is proposed and applied to six one-dimensional test cases. It allows the computation of spectrally integrated intensities (over 25 cm−1 bands or the full IR range) in a few seconds, regardless of the retained database and line model. But free parameters need to be selected and they impact the convergence. A first possible selection is provided in full detail. We observe that this selection is highly satisfactory for quite distinct atmospheric and combustion configurations, but a more systematic exploration is still in progress