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Search Results: 1 - 10 of 5639 matches for " Salvador Contreras "
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An Alternative View to the Cause of Market Failures: A Dynamic Approach  [PDF]
Salvador Contreras
Theoretical Economics Letters (TEL) , 2014, DOI: 10.4236/tel.2014.47069
Abstract:

This paper presents an alternative view to the cause and size of market failures. The work here suggest that the size of the market failure is not man made per se but rather given a full set of initial conditions it is endogenous to the dynamical forces at play. It is shown that the level and variance of market failures is tied to the location of the steady state (i.e. level of development). The paper finds that only changes to the location of the steady state produces changes to the potential level of the market failure. This paper adds to the increasing body of literature the notion that institutional change is not a sufficient condition to sustained economic development.

Descripción del cráneo de Bramocharax caballeroi Contreras & Rivera 1985 (Pisces, Characidae), pez endémico del Lago de Catemaco, Veracruz, México
Valdez-Moreno, Martha Elena;Contreras-Balderas, Salvador;
Hidrobiológica , 2009,
Abstract: the bramocharax genus is distributed from central america to mexico. until now the species known are bramocharax bransfordi collected in nicaragua and costa rica, b. dorioni and b. baileyi from guatemala and b. caballeroi from catemaco lake, veracruz, mexico. the aim of this work is to realize a detailed description of the skull for bramocharax caballeroi from the analysis of 37 different topotypes. the skull of this species has 58 osteological elements, 49 of them coupled. shape is oval in lateral view, because the bones of the snout (ethmoid, vomer, lateral ethmoid, dentary, maxillae, premaxillae, ecto and mesopterygoids) and the frontal and circunorbitals are elongated. the dorsal margin is slightly concave and the anterior part is elongated. in specimens less than 80 mm, all the bones are smoother, with more regular edges. with the age increase, they become more robust with more irregular edges. a comparison of s the skull between b. caballeroi and astyanax mexicanus resulted in 25 bones with differences, while with astyanax fasciatus, main contrasts were the supraoccipital length, the shape of the opercles and the infraorbital 3. in addition there are important differences in the dentition, gill rackers, as well as suspensory pharingeals and pharyngeal plates with respect to astyanax.
Relación entre el peso corporal, medidas corporales y edad en el crecimiento de caprinos mestizos Canarios desde el nacimiento hasta el a?o de edad en el trópico
Salvador,Alejandro; Contreras,Ignacio; Martínez,Gonzalo; Hahn,Martín;
Zootecnia Tropical , 2009,
Abstract: in order to study the relationship between body weight (bw) and some biometric variables in crossbred canarian (from 3/4 to 7/8) growing goats, a study using 383 records was realized with 52 goats from birth up to one year old. the following measurements were recorded monthly: bw, thoracic perimeter (tp), thoracic depth (dp), wither height (wh), and body length (bl). data were analyzed using linear models. model included sex, calving type, and calving number of the dam. calving number of dam was not significant (p>0.05), and the sex and calving type affected all traits. pearson simple correlation between bw and tp, td, wh and bl were estimated. the estimates were 0,96; 0,93; 0,94 y 0,95, respectively (p<0.01). to predict bw a multiple regression equation with two variables (age and a morfometric variable) and a multiple regression equation with all morfometric variables and age were calculated using weights adjusted by calving type. the best predictor of bw was tp using the equation bw = -8,84 + 0,32 (tp) + 0,02 (age) for females (r2 = 0.954) and bw = -12,73 + 0,42 (tp) + 0,03 (age) for males (r2 = 0.962).
Descripción del cráneo de Bramocharax caballeroi Contreras & Rivera 1985 (Pisces, Characidae), pez endémico del Lago de Catemaco, Veracruz, México Description of the skull of Bramocharax caballeroi Contreras & Rivera 1985 (Pisces, Characidae), endemic fish to Catemaco Lake, Veracruz, Mexico
Martha Elena Valdez-Moreno,Salvador Contreras-Balderas
Hidrobiológica , 2009,
Abstract: El género Bramocharax se distribuye del centro-norte de Centro América a México. Hasta este momento se conoce a Bramocharax bransfordi de Nicaragua y Costa Rica, a B. dorioni y B. baileyi de Guatemala y a B. caballeroi del lago de Catemaco, Veracruz, México. El trabajo tuvo por objetivo estudiar detalladamente el cráneo de Bramocharax caballeroi a partir del análisis de 37 topotipos de diferentes tallas y compararlo con otras especies relacionadas. B. caballeroi presenta 58 huesos en su cráneo, de los cuales 49 son elementos pareados. En vista lateral su perfil es ovalado, debido a los huesos que conforman el hocico (etmoides, vómer, etmoides lateral, mandíbula, maxila, premaxila, ecto y mesopterigoides), así como el frontal y los circunorbitales, son alargados. El margen dorsal es ligeramente cóncavo y la parte anterior alargada. En los ejemplares menores a 80 mm todos los huesos son más lisos y conforme los organismos tienen una talla mayor, se hacen más robustos y los bordes de cada hueso se hacen más irregulares. Al comparar el cráneo de B. caballeroi con el de Astyanax mexicanus se encontraron diferencias en 25 huesos, mientras que al hacerlo con A. fasciatus, los principales contrastes fueron la longitud del supraoccipital, la forma del opérculo y del infraorbital 3. Adicionalmente, se encontraron diferencias importantes en la dentición y en las branquiespinas así, como en las placas y suspensores faríngeos con respecto a los Astyanax. The Bramocharax genus is distributed from Central America to Mexico. Until now the species known are Bramocharax bransfordi collected in Nicaragua and Costa Rica, B. dorioni and B. baileyi from Guatemala and B. caballeroi from Catemaco Lake, Veracruz, Mexico. The aim of this work is to realize a detailed description of the skull for Bramocharax caballeroi from the analysis of 37 different topotypes. The skull of this species has 58 osteological elements, 49 of them coupled. Shape is oval in lateral view, because the bones of the snout (ethmoid, vomer, lateral ethmoid, dentary, maxillae, premaxillae, ecto and mesopterygoids) and the frontal and circunorbitals are elongated. The dorsal margin is slightly concave and the anterior part is elongated. In specimens less than 80 mm, all the bones are smoother, with more regular edges. With the age increase, they become more robust with more irregular edges. A comparison of S the skull between B. caballeroi and Astyanax mexicanus resulted in 25 bones with differences, while with Astyanax fasciatus, main contrasts were the supraoccipital length, the shape of the opercles and
In the monarch butterfly the juvenile hormone effect upon immune response depends on the immune marker and is sex dependent  [PDF]
Guadalupe Villanueva, Humberto Lanz-Mendoza, Salvador Hernández-Martínez, Minerva Sánchez Zavaleta, Javier Manjarrez, José M. Contreras-Gardu?o, Jorge Contreras-Gardu?o
Open Journal of Ecology (OJE) , 2013, DOI: 10.4236/oje.2013.31007
Abstract:

In insects, juvenile hormone (JH) decreases or has any effect upon the phenoloxidase (PO) activity, and favors or decreases the Antimicrobial Peptides (AMPs) expression. Although there is no information about the differential effect of such hormone, two possibilities are that it depends on (a) the immune marker recorded and (b) sexual differences. Here, three commonly used immune markers, Phenoloxidase (PO), hydrogen peroxide (H2O2), and lytic activity, were measured 3, 6 and 24 hours after administration of methoprene (JHa, an analog of juvenile hormone) in male and female monarch butterflies (Danaus plexippus). At 3 and 6 h post-JHa administration, the PO activity increased in females but it only increased at 3 h in males, whereas H2O2 levels increased only in females at 3 h. For the remaining times the JHa had a null effect on POand H2O2. On the other hand, the JHa had a null effect for lytic activity in both sexes at 3, 6 and 24 h. To our knowledge, this is the first report of a positive effect of a JHa onPOand H2O2 and suggests that this effect is sex dependent.

DESCRIPCIóN DE LOS PROCESOS COGNOSCITIVOS IMPLICADOS EN LA ESCRITURA DE UN ENSAYO
MENESES BáEZ,ALBA LUCíA; MATA,FRANCISCO SALVADOR; RAVELO CONTRERAS,ERNESTO L.;
Acta Colombiana de Psicología , 2007,
Abstract: the processes of planning, transcription, revision, metacognition and affection involved in the construction of an argumentative essay written by 11 university students were examined. several assessment instruments designed by the authors were administered: the verbal protocol, the essay-writing strategies questionnaire and the self-perception scales on writing efficacy and attitude toward writing. a frequency count per component of the textual data obtained by means of the verbal protocol and based on a content analysis was carried out. later, the percentages within each category were calculated for each subject, based on his/her performance with respect to the group. finally, a descriptive analysis of the self-reports was done. at the time of observation of the above mentioned processes using the verbal protocol, six participants showed evidence of planning, transcription, revision and meta-cognition during the writing process. however, when doing revision, none of them presented revision by others, and on the metacognition component only two participants demonstrated their awareness of the essay structure. with respect to self-reports, the participants expressed moderate to high levels of planning, revision and metacognition strategies, as well as moderate to high scores on attitudes toward writing and self-perception of writing efficacy when elaborating an essay
Efecto de la alimentación con grasa sobrepasante sobre la produccióny composición de leche de cabra en condiciones tropicales
Salvador,Alejandro; Alvarado,Carlos; Contreras Solis,Ignacio; Betancourt,Ricardo; Gallo,Jorge; Caigua,Allan;
Zootecnia Tropical , 2009,
Abstract: effects of supplementation with protected fat and parity on goat milk production and composition were determined with 31 crossbreed canarias goats located in maracay, venezuela. also, effects on body weight changes, body condition, and blood triglycerides and cholesterol concentrations were evaluated. additive linear statistical models with repeated measures of time with proc glm were used and tukey test to detect significant differences. the treatment and the calving number had a highly significant effect (p<0.01) over the total production. goat receiving diets with protected fat showed the longest lactation. neither treatment nor parity affected milk physical characteristics, but the treatment did increase significantly (p<0.01) all milk components in a profitable way. treatment had no significant effect on body weight, body condition or voluntary consumption. the calving number had a significant effect (p<0.01) on the milk components and body weight, all of them increased accordingly up to the 4th calving number. neither treatment nor parity had a significant effect on blood cholesterol or triglyceride concentrations. there were not significant correlations between blood cholesterol and triglyceride levels or between milk production, milk component levels, body weight or body condition.
DESCRIPTION OF COGNITIVE PROCESSES INVOLVED IN ESSAY-WRITING
Meneses Báez, Alba Lucía,Mata, Francisco Salvador,Ravelo Contreras, Ernesto L.
Acta Colombiana de Psicología , 2007,
Abstract: The processes of planning, transcription, revision, metacognition and affection involved in the construction of an argumentative essay written by 11 university students were examined. Several assessment instruments designed by the authors were administered: The Verbal Protocol, The Essay-writing Strategies Questionnaire and the Self-Perception Scales on Writing Efficacy and Attitude Toward Writing. A frequency count per component of the textual data obtained by means of the Verbal Protocol and based on a content analysis was carried out. Later, the percentages within each category were calculated for each subject, based on his/her performance with respect to the group. Finally, a descriptive analysis of the self-reports was done. At the time of observation of the above mentioned processes using the Verbal Protocol, six participants showed evidence of planning, transcription, revision and meta-cognition during the writing process. However, when doing revision, none of them presented revision by others, and on the metacognition component only two participants demonstrated their awareness of the essay structure. With respect to self-reports, the participants expressed moderate to high levels of planning, revision and metacognition strategies, as well as moderate to high scores on attitudes toward writing and self-perception of writing efficacy when elaborating an essay
Preliminary study of slags and slaggy layers on ceramics from the Bronze Age metallurgical site of Pe alosa (Ba os de la Encina, Jaén)
Moreno Onorato, Auxilio,Contreras Cortés, Francisco,Renzi, Martina,Rovira Llorens, Salvador
Trabajos de Prehistoria , 2010,
Abstract: This paper offers a revision of the metallurgical processes carried out at the settlement on the basis of a recent analytical study of slags and slagged metallurgical ceramics. These analyses allowed us to identify the ores processed and the characteristics of this metal production. Therefore, the results obtained provide new perspectives to determining what type of technology was developed and the working conditions of the different processes carried out at the site. In this sense, the use of lead-rich copper ores stands out in explaining the presence of high quantities of lead compounds detected in various metallurgical ceramics and in secondary products, like slags and melting wastes. The present study also includes typological and technological analysis of metallurgical ceramic vessels. Este trabajo ofrece una revisión de los procesos metalúrgicos llevados a cabo en el asentamiento I, de acuerdo con los resultados del reciente estudio analítico realizado sobre los restos de escorias y escorificaciones de cerámicas metalúrgicas. A partir de estos análisis, que nos permiten la identificación de los minerales procesados y de las características de la producción metálica obtenida, se aportan nuevas perspectivas para determinar el tipo de tecnología desarrollada y las condiciones en las que se llevaron a cabo los diferentes procesos. En este sentido destaca la utilización de minerales de cobre muy ricos en plomo, que proporcionan altas cantidades de compuestos de plomo en las vasijas cerámicas y en productos secundarios como escorias y restos de fundición. Se completa el estudio con el análisis de la tipología y tecnología de las vasijas cerámicas de uso metalúrgico.
Endomyocardial fibrosis in infancy
Jatene Marcelo Biscegli,Contreras Ivan Salvador Bonillo,Lameda Laura C. Riera,Oliveira Jr. José de Lima
Arquivos Brasileiros de Cardiologia , 2003,
Abstract: The patient was a 4-month-old infant, who underwent persistent ductus arteriosus interruption with titanium clips at the age of 13 days and, since the age of 2 months, had crises of hypoxia and hypertonicity. After clinical investigation, the presence of pulmonary hypertension was confirmed and left ventricular inflow tract obstruction was suspected. The patient underwent surgical treatment at the age of 4 months, during which right and left ventricular endocardial fibrosis was identified. The fibrosis was resected, but the infant had an unfavorable clinical evolution with significant diastolic restriction and died on the sixth postoperative day. Anatomicopathological and surgical findings suggested endomyocardial fibrosis, although that pathology is very rare at the patient's age.
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