VP AND VS DETERMINATION OF THE OUTCROPING ROCK UNITS IN THE MERIDA METROPOLITAN AREA, VENEZUELA

Para los alrededores del área metropolitana de Mérida se determinó, mediante sísmica de refracción, las velocidades de propagación de las ondas P (Vp) y S (Vs) en los afloramientos de los distintos tipos de rocas predominantes de las asociaciones Sierra Nevada, Tostos y Mucuchachí, y las formaciones Palmarito, Sabaneta, La Quinta, Aguardiente, La Luna y San Javier. Para los casos de las asociaciones Sierra Nevada y Tostos, la Vs se calculó a partir de la Vp y el coeficiente de Poisson. La extensión de las líneas sísmicas varió de 24 m a 26 m, utilizando en todos los casos 48 geófonos verticales e igual número de horizontales, y como fuente de energía una mandarria. La adquisición de los registros sísmicos fue llevada a cabo directamente sobre los afloramientos, por lo que en los casos de rocas más competentes no se pudo insertar directamente los geófonos, y como medida alternativa se utilizó la técnica de insertarlos en bloques de concreto. Los arribos de las ondas P se obtuvieron de los registros de los geófonos verticales y los de la S (SH) de los horizontales. Los resultados de este trabajo ofrecen, información de las velocidades de las ondas P y S de las principales tipo de roca en superficie, y puede servir de complemento a investigaciones de sísmica profunda.For the predominant rock type of outcrops in the surroundings of the metropolitan area of Mérida city,compressional (Vp) and shear (Vs) wave velocities were determined using seismic refraction. These outcrops correspond to the Sierra Nevada, Tostos, and Mucuchachí Associations, and Palmarito, Sabaneta, La Quinta, Aguardiente, La Luna, and San Javier formations. Vs values for Sierra Nevada and Tostos Associations were estimated from Vp values and laboratory measured Poisson ratio. The length of the seismic lines ranged from 24 m to 26 m, using for all cases 48 vertical geophones and an equal number of horizontal geophones. A sledgehammer was used as energy source. The seismic acquisition was carried out directly from the outcrops. However, for the cases of more competent rocks, the geophones could not be placed directly, so they were inserted in concrete blocks to keep them firm and vertical. The P waves arrivals were obtained via the vertical geophones and the S (SH) waves arrivals were obtained via the horizontal geophones. The results of this investigation offer information of P and S wave velocities of the main surface rock types, which could be useful as complementary data for future deep seismic sounding studies

VP AND VS DETERMINATION OF THE OUTCROPING ROCK UNITS IN THE MERIDA METROPOLITAN AREA, VENEZUELA

Para los alrededores del área metropolitana de Mérida se determinó, mediante sísmica de refracción, las velocidades de propagación de las ondas P (Vp) y S (Vs) en los afloramientos de los distintos tipos de rocas predominantes de las asociaciones Sierra Nevada, Tostos y Mucuchachí, y las formaciones Palmarito, Sabaneta, La Quinta, Aguardiente, La Luna y San Javier. Para los casos de las asociaciones Sierra Nevada y Tostos, la Vs se calculó a partir de la Vp y el coeficiente de Poisson. La extensión de las líneas sísmicas varió de 24 m a 26 m, utilizando en todos los casos 48 geófonos verticales e igual número de horizontales, y como fuente de energía una mandarria. La adquisición de los registros sísmicos fue llevada a cabo directamente sobre los afloramientos, por lo que en los casos de rocas más competentes no se pudo insertar directamente los geófonos, y como medida alternativa se utilizó la técnica de insertarlos en bloques de concreto. Los arribos de las ondas P se obtuvieron de los registros de los geófonos verticales y los de la S (SH) de los horizontales. Los resultados de este trabajo ofrecen, información de las velocidades de las ondas P y S de las principales tipo de roca en superficie, y puede servir de complemento a investigaciones de sísmica profunda.For the predominant rock type of outcrops in the surroundings of the metropolitan area of Mérida city,compressional (Vp) and shear (Vs) wave velocities were determined using seismic refraction. These outcrops correspond to the Sierra Nevada, Tostos, and Mucuchachí Associations, and Palmarito, Sabaneta, La Quinta, Aguardiente, La Luna, and San Javier formations. Vs values for Sierra Nevada and Tostos Associations were estimated from Vp values and laboratory measured Poisson ratio. The length of the seismic lines ranged from 24 m to 26 m, using for all cases 48 vertical geophones and an equal number of horizontal geophones. A sledgehammer was used as energy source. The seismic acquisition was carried out directly from the outcrops. However, for the cases of more competent rocks, the geophones could not be placed directly, so they were inserted in concrete blocks to keep them firm and vertical. The P waves arrivals were obtained via the vertical geophones and the S (SH) waves arrivals were obtained via the horizontal geophones. The results of this investigation offer information of P and S wave velocities of the main surface rock types, which could be useful as complementary data for future deep seismic sounding studies

Use of a recombinant Salmonella enterica serovar Typhimurium strain expressing C-Raf for protection against C-Raf induced lung adenoma in mice

BACKGROUND: Serine-threonine kinases of the Raf family (A-Raf, B-Raf, C-Raf) are central players in cellular signal transduction, and thus often causally involved in the development of cancer when mutated or over-expressed. Therefore these proteins are potential targets for immunotherapy and a possible basis for vaccine development against tumors. In this study we analyzed the functionality of a new live C-Raf vaccine based on an attenuated Salmonella enterica serovar Typhimurium aroA strain in two Raf dependent lung tumor mouse models. METHODS: The antigen C-Raf has been fused to the C-terminal secretion signal of Escherichia coli α-hemolysin and expressed in secreted form by an attenuated aroA Salmonella enterica serovar Typhimurium strain via the α-hemolysin secretion pathway. The effect of the immunization with this recombinant C-Raf strain on wild-type C57BL/6 or lung tumor bearing transgenic BxB mice was analyzed using western blot and FACS analysis as well as specific tumor growth assays. RESULTS: C-Raf antigen was successfully expressed in secreted form by an attenuated Salmonella enterica serovar Typhimurium aroA strain using the E. coli hemolysin secretion system. Immunization of wild-type C57BL/6 or tumor bearing mice provoked specific C-Raf antibody and T-cell responses. Most importantly, the vaccine strain significantly reduced tumor growth in two transgenic mouse models of Raf oncogene-induced lung adenomas. CONCLUSIONS: The combination of the C-Raf antigen, hemolysin secretion system and Salmonella enterica serovar Typhimurium could form the basis for a new generation of live bacterial vaccines for the treatment of Raf dependent human malignancies

Molecular Identification of Campylobacter concisus

A 1.6-kb DNA fragment isolated from a Campylobacter concisus genomic library gave C. concisus-specific restriction fragment length patterns when it was used as a probe in hybridization studies. All of the strains tested, including type strains and clinical isolates, contained a 0.5-kb HindIII fragment that hybridized to the probe. DNA sequencing of the 1.6-kb fragment identified three open reading frames (ORFs). One of the ORFs encodes the carboxy terminus of GyrB, and the translational products of ORF2 and ORF3 showed similarity to hypothetical proteins, previously identified in Campylobacter jejuni. DNA-DNA hybridization studies with a fragment internal to ORF3 showed that this sequence was responsible for the signal observed with the 0.5-kb HindIII fragment. A rapid PCR assay was developed and evaluated. Primers that annealed to the extremities of the 1.6-kb fragment were used to obtain an amplicon of the correct size from both reference and clinical strains of C. concisus