Ciencia y Tecnología
Socio-Cultural Differences and Intercultural Communication in Social Participation Experiences
Mato, Daniel Alejandro
This article discusses the main theoretical and methodological aspects of the intercultural communication analytical perspective that I have developed to respond to specific research needs. This perspective is based on the idea that institutional and collective social actors are heterogeneous entities because they comprise a variety of internal parties, as I have been able to observe in my field research experience. Intercultural communication involves, therefore, multidimensional exchanges between heterogeneous agents that build meaning and struggle over it within their own group as well as with the other social agents. Meaning is something that is negotiated, transformed, appropriated, and can often be a subject of dispute. For that reason, the study of intercultural communication should center on social processes, not just verbal utterances. Close examination of social practices and relations enable us to understand how differences are articulated and how meaning is transformed.
A new species of Mathevotaenia (cestoda, anoplocephalidae) parasitizing tropidurus spinulosus (reptilia, squamata) from northeastern Argentina
A new species of Mathevotaenia (cestoda, anoplocephalidae) parasitizing tropidurus spinulosus (reptilia, squamata) from northeastern Argentina; Una especie nueva de Mathevotaenia (Cestoda, Anoplocephalidae) parásita de Tropidurus spinulosus (Reptilia, Squamata) del noreste de Argentina
Lunaschi, Lía Inés; Lamas, Matías Fernando; Drago, Fabiana Beatriz
Mathevotaenia chaquensis n. sp. (Cestoda, Anoplocephalidae, Linstowiinae) from a Spiny Lava Lizard, Tropidurus spinulosus, collected in Chaco Province, c Argentina, is described. This is the second species of Mathevotaenia described from Neotropical reptiles. The new species is mainly characterized by having a relatively small strobila, 24 mm in total length, with about 100 craspedote proglottids, and 19-24 testes per proglottid. Among the South American species of Mathevotaenia, M. argentinensis is most similar to the new species by having similar body length and number of testes, but the major differences between both species include the size of suckers, neck, proglottids, testes and egg capsules, and the shape of the genital atrium and ovary (with 10-13 lobules on each side in M. argentinensis, and 4-7 lobules in M. chaquensis n. sp.). A key to the species of the South American members of the Mathevotaenia Akumyan, 1946 is presented.
El operaismo italiano y su historiografía. Introducción a ''Ocho tesis sobre la historia militante'' de Sergio Bologna
El operaismo italiano y su historiografía. Introducción a ''Ocho tesis sobre la historia militante'' de Sergio Bologna
Grigera, Juan Francisco
Traducir un texto de más de 30 años requiere, sin duda, intentar explicar primero por qué publicarlo hoy. Es decir, contar el contexto en que fue producido, para y por quién fue escrito originalmente, y así permitir que se trasluzca del palimpsesto aquello que supo decir y lo que tiene para decirnos a nosotros. Lo cierto es que antes de presentar un texto no muy conocido del operaismo (obrerismo) italiano es justo hacer una aclaración sobre la diversidad de sus miembros y múltiples corrientes, como de las suertes que corrieron. Por una parte, es necesario devolver la imagen de su heterogeneidad, después de que el operaismo se haya vuelto conocido casi exclusivamente por las últimas ideas de Antonio Negri, cuando no filtrado por las lecturas peculiares de Deleuze y Guattari, perdiéndose de vista sus otras tendencias (Wright, 2002: 2) o confundido con el autonomismo de corte situacionista. Pero por otra parte, también es necesaria cierta presentación, pues la corriente italiana ha sufrido peores castigos que la deformación o el sesgo: me refiero al simple olvido, al menos en el habla castellana hoy. Es que el vocablo “obrerismo”, podría designar bastante más que el epíteto descalificador de quienes se obsesionan con las supuestas potencialidades revolucionarias de los trabajadores manufactureros. El “obrerismo” es también una corriente de pensamiento italiana, un producto intelectual original, caracterizado por el desarrollo de, o el énfasis en, un conjunto de conceptos (composición de clase, autonomía, crítica del desarrollo, general intellect), por un número de autores (Panzieri, Tronti, Negri, Alquati, Bologna, entre los más destacados) y de revistas (Quaderni Rossi, Clase Operaia, Primo Maggio). Estos estructuraron conscientemente “el significado y relevancia de cada concepto para el desarrollo inmediato de la clase trabajadora” (Cleaver, 1985: 72), dándole a ésta una importancia soberana como sujeto autónomo de la lógica del capital.
Estrategias empresariales en contextos de alta incertidumbre: Desafíos de una empresa productora de aluminio en la Argentina (1970-2001)
Estrategias empresariales en contextos de alta incertidumbre: Desafíos de una empresa productora de aluminio en la Argentina (1970-2001); Business Strategies in Contexts of High Uncertainty: Challenges of an Aluminum Producer in Argentina (1970-2001)
Rougier, Marcelo Norberto
Este trabajo estudia las estrategias empresariales de la firma Aluminio Argentino desde sus orígenes en 1970 hasta la crisis económica de 2001. La puesta en marcha de la planta fue posible por la ingente ayuda del Estado argentino y coincidió con un período de gran inestabilidad macroeconómica y de fuerte reducción de la demanda doméstica, con el agravante de enfrentar un mercado internacional signado por la recesión que se sostuvo prácticamente hasta los años noventa. El estudio ilustra también las estrategias de los empresarios una vez que el marco regulatorio que le dio origen desapareció y la empresa debió enfrentar un fuerte shock competitivo; This paper examines the business strategies of the firm Aluminio Argentino (Aluar) since its inception in 1970 to the 2001 economic crisis. The commissioning of the plant was made possible by the tremendous support of the State and his performance coincided with a period of great macroeconomic instability and sharp reduction in domestic demand, deal with the aggravation of an international market marked by the recession which was held almost until the nineties. The study also illustrates the strategies of the business once the regulatory framework that gave rise disappeared and the company faced a strong competitive shock.
Estrategias de desarrollo y modalidades de financiamiento en el "Canto de Cisne" de la industrialización argentina
Estrategias de desarrollo y modalidades de financiamiento en el "Canto de Cisne" de la industrialización argentina
Rougier, Marcelo Norberto; Odisio, Juan Carlos
En los años sesenta los economistas argentinos debatieron distintas alternativas para encaminar el desarrollo y la acumulación en el orden interno. Para el logro de ese objetivo, se consideraba necesario impulsar la inversión, para lo que se precisaba diseñar mecanismos de financiamiento adecuados. Partiendo de los mismos, este trabajo pretende mostrar que un importante conjunto de firmas de capital nacional pudo acceder a nuevas formas de fondeo y la política industrial se encaminó cada vez más a impulsar grandes empresas de capital local. Más allá de los vaivenes de cada proyecto, el Estado tuvo relativo éxito en el impulso de grandes obras (que en algunos casos permitieron iniciar la anhelada corriente de exportación manufacturera), a través de mecanismos específicos de canalización de recursos, en la última etapa de la estrategia de industrialización sustitutiva.; In the sixties, several Argentine economists discussed alternatives for directing development and accumulation in the internal order. To achieve this goal, the boost of investment was considered necessary, for what was needed an appropriate design of financing mechanisms. On that basis, this work intends to show that an important set of national capital firms gained access to new forms of funding and the industrial policy increasingly headed to promote huge companies of local capital. Beyond the vagaries of each project, the State had relative success in promoting major projects (that in some cases allowed to initiate the desired flow of manufacturing exports), through specific mechanisms for channeling resources, in the last stage of the substitution industrialization strategy.
Calf tissue oxygenation during exercise in men with and without risk factors for developing peripheral arterial disease
Calf tissue oxygenation during exercise in men with and without risk factors for developing peripheral arterial disease
Miranda, Alberto; Figoni, Stephen F.; Cha, Tha; Flanagan, Terrance; Mandal, Oanh; Silva, Mariana; Scremin, A.M. Erika; Scremin, Oscar Umberto
OBJECTIVE: This study aimed to compare calf tissue oxygenation responses to calf exercise in men without diagnosed peripheral arterial disease but with selected risk factors for peripheral arterial disease with those without risk factors. DESIGN: A cross-sectional quasi-experimental design was used. The no-risk group (n = 20) had none of the risk factors (diabetes, hypertension, hyperlipidemia, obesity, current or 10 pack-yr smoking history, or age >65 yrs). The at-risk group (n = 45) had one to six risk factors. Medial calf tissue oxygenation (percentage saturation) was determined using near-infrared spectroscopy during seven consecutive 5-min test stages: rest, 0-W active plantar/dorsiflexion, rest, 4-W resistive plantar flexion, rest, 8-W resistive plantar flexion, and rest. Resistive exercise was performed on the Stresst'er calf ergometer. RESULTS: Compared with the no-risk group, decrements in calf tissue oxygenation induced by light-to-moderate resistive calf exercise in the at-risk group was significantly greater (by 9% saturation) (4-W: P < 0.001; 8-W: P = 0.002). CONCLUSIONS: Men with risk factors for developing peripheral arterial disease but without such diagnosis demonstrated greater decrements in calf tissue oxygenation during calf exercise compared with men without risk factors. Further development of this test may lead to early diagnosis and intervention to modify risk factors and prevent co-morbidities.
Simple fatigue testing machine for fiber-reinforced polymer composite
Simple fatigue testing machine for fiber-reinforced polymer composite
Pach, Esteban; Korin, Ivan; Perez Ipiña, Juan Elias
Fiber-reinforced polymer (FRP) composites seem to be the best options in many structural applications. Such applications are often exposed to fatigue loads, and therefore, the fatigue behavior of the composites must be studied in order to achieve a proper design. This is fulfilled by means of an experimental characterization, in which a lot of specimens are tested because of the several parameters involved (i.e., fiber/matrix ratio, fiber orientation, staking sequence, etc.). Besides, the fatigue tests must be carried out at low frequencies, in order to avoid temperature increments in the polymer matrix, which would change the mechanical properties of the composite. Consequently, considerable time is consumed to perform a complete set of tests and, when using conventional servohydraulic testing machines, costs rise notably. A machine to perform fatigue tests of composite materials under constant amplitude load cycles and a wide range of load ratios is presented in this paper. This machine exhibits as main goals the fulfillment of the corresponding standard requirements, a very low cost compared to conventional servohydraulic testing machines and, consequently, makes reasonably priced to have several machines testing specimens simultaneously, in order to reduce the necessary time to complete the whole characterization.
On the molecular structure of uranium dicarbide: T-shape versus linear isomers
On the molecular structure of uranium dicarbide: T-shape versus linear isomers
Zalazar, Maria Fernanda; Rayon, Victor M.; Largo, Antonio
A theoretical study of the molecular structure of uranium dicarbide has been carried out employing DFT, coupled cluster, and multiconfigurational methods. A triangular species, corresponding to a 5A 2 electronic state, has been found to be the most stable UC 2 species. A triplet linear CUC species, which has been observed in recent infrared spectroscopy experiments, lies much higher in energy. A topological analysis of the electronic density has also been carried out. The triangular species is shown to be in fact a T-shape structure with a U-C interaction which can be considered to be a closed-shell interaction.
Females prefer good genes: MHC-associated mate choice in wild and captive tuco-tucos
Females prefer good genes: MHC-associated mate choice in wild and captive tuco-tucos
Cutrera, Ana Paula; Fanjul, Maria Sol; Zenuto, Roxana Rita
The major histocompatibility complex (MHC) genes are one of the most suitable candidates for elucidating the genetic bases of mate choice in vertebrates, given the potential benefits in terms of immunocompetence that can be passed to the offspring through MHC-associated mate choice. Female mate choice may favour males that possess particular MHC alleles or those with diverse MHC genotypes (good genes hypothesis), or males that possess MHC genotypes that differ from that of the female (compatibility hypothesis). Our goal was to evaluate mate choice in relation to MHC genotype in the subterranean rodent Ctenomys talarum. Using both laboratory and field analyses, we investigated whether the (1) number of shared MHC alleles between males and females, (2) number of amino acid differences between female and male MHC alleles, (3) MHC heterozygosity of males, (4) number of amino acid differences between male MHC alleles, and (5) frequency of MHC alleles of males differ between preferred and nonpreferred males in the laboratory and between potential sires and random males from the population in the field. In the laboratory, our results indicate that MHC alleles of preferred males differ in fewer amino acids compared to MHC alleles of nonpreferred males. Concomitantly, in the field,MHC alleles of possible sires differed in fewer amino acids than those of random males in the population. Plus, possible sires were more heterozygous and carried distinct MHC alleles compared with random males, thus providing more support to the "good genes" hypothesis. We discuss the possible reasons why MHC-based mate choice was more evident in the field and the implications of such a female mating strategy in the subterranean environment.
Stable isotopes identify age- and sex-specific dietary partitioning and foraging habitat segregation in southern giant petrels breeding in Antarctica and southern Patagonia
Stable isotopes identify age- and sex-specific dietary partitioning and foraging habitat segregation in southern giant petrels breeding in Antarctica and southern Patagonia
Raya Rey, Andrea Nélida; Polito, Michael; Archuby, Diego Ignacio; Coria, Néstor Rubén
We examined the isotopic signatures (δ 13C, δ 15N) of adult body feathers from southern giant petrels Macronectes giganteus collected at two breeding colonies in Antarctica (Potter Peninsula and Cape Geddes) and one in southern Patagonia (Observatorio Island), as well as in whole blood collected from adults of both sexes at each Antarctic colonies and from chicks at Potter Peninsula. As body feather moult is a continuous process in giant petrels, feathers provide an integrated annual signal of an adult's diets and foraging habitats. In contrast, the stable isotope values of adult and chick blood are reflective of their diets during the breeding season. We found that sex-specific dietary segregation in adults breeding in Antarctica was notable during the breeding season (blood samples) but absent when examined across the entire year (feather samples). In addition, blood stable isotope values differed between chicks and adults, indicating that adults provision their offspring with a relatively higher amount of penguin and seal prey that what they consume themselves. This finding confirms previous work that suggests that chicks are preferentially fed with prey of presumably higher nutritional value such as carrion. Finally, based on isotopic differences between major oceanographic zones in the Southern Ocean, our data indicate population-specific differences in foraging distribution, with Antarctic populations move seasonally between Antarctic and subantarctic zones, while Patagonian populations likely forage in subtropical waters and in continental shelf habitats year-round.
Dra. Eugenia Sacerdote de Lustig: la inagotable pasión de una investigadora ejemplar
Dra. Eugenia Sacerdote de Lustig: la inagotable pasión de una investigadora ejemplar
Su historia, al igual que la de millones de inmigrantes europeos que llegaron a Argentina durante la primera mitad del siglo XX, estuvo marcada por el esfuerzo, la lucha y la esperanza de encontrar, en estas tierras, una vida mejor, lejos de las persecuciones y barbaries ocasionadas por dos devastadoras guerras mundiales. A cuatro meses de su fallecimiento, su legado científico y su experiencia de vida se han transformado en una fuente de inspiración para cientos de médicos e investigadores del país que ven en ella un ejemplo para seguir.
Synthesis of the unique angular tricyclic chromone structure proposed for aspergillitine, and its relationship with alkaloid TMC-120B
Synthesis of the unique angular tricyclic chromone structure proposed for aspergillitine, and its relationship with alkaloid TMC-120B
Simonetti, Sebastián Osvaldo; Larghi, Enrique Leandro; Bracca, Andrea Beatriz Juana; Kaufman, Teodoro Saul
The synthesis of the tricyclic angular chromone structure originally assigned to aspergillitine is reported. The synthesis was achieved in 11 steps and 15% overall yield from 2,4-dihydroxypropiophenone, through the intermediacy of 2,3-dimethyl-7-hydroxychromen-4-one. Construction of the nitrogen-bearing heterocyclic ring entailed a Stille cross-coupling reaction with n-Bu3SnCH2CHCH2, followed by double bond isomerization, oximation of the chromone carbonyl, and a final microwave-assisted electrocyclization of the thus formed 6π-electron aza-triene system.
First Century of Chagas' Disease: An Overview on Novel Approaches to Nifurtimox and Benznidazole Delivery Systems
First Century of Chagas' Disease: An Overview on Novel Approaches to Nifurtimox and Benznidazole Delivery Systems
Salomon, Claudio Javier
Hundred years after the discovery of Chagas' disease, there is a lack of effective treatment to control this neglected disease caused by the parasite Trypanosoma cruzi. The transmission is primarily through vector-borne blood transfusion or during pregnancy, producing high mortality and morbidity among poor people in many countries of Latin America. In the last decades, the efforts have been focused mainly on the elimination of vectors. At the same time, screening of blood donors in order to avoid transfusional transmission has been improved all over the world. However, Chagas' disease is still a major public health problem, with estimates of nearly 90 million people at risk of infection and more than eight million infected in 18 endemic countries. Despite the high incidence in endemic regions and the dissemination of neglected diseases in North America and Europe, to date, there are only two drugs developedn and prescribed for the treatment of Chagas' disease, nifurtimox (tablets of 120 mg) and benznidazole (tablets of 100 mg). In this review, different approaches carried out in the last decades for developing novel pharmaceutical formulations for the delivery of nifurtimox and benznidazole are discussed.
ROS enhancement by silicon nanoparticles in X-ray irradiated aqueous suspensions and in glioma C6 cells
ROS enhancement by silicon nanoparticles in X-ray irradiated aqueous suspensions and in glioma C6 cells
David Gara, Pedro Maximiliano; Garabano, Natalia Ines; Llansola Portolés, Manuel Jose; Moreno, Mario Sergio Jesus; Dodat, Diego; Casas, Oscar; Gonzalez, Monica Cristina; Kotler, Monica Lidia
The capability of silicon nanoparticles to increase the yield of reactive species upon 4 MeV X-ray irradiation of aqueous suspensions and C6 glioma cell cultures was investigated. ROS generation was detected and quantified using several specific probes. The particles were characterized by FTIR, XPS, TEM, DLS, luminescence, and adsorption spectroscopy before and after irradiation to evaluate the effect of high energy radiation on their structure. The total concentration of O 2 ·-/HO 2 ·, HO ·, and H 2O 2 generated upon 4-MeV X-ray irradiation of 6.4 μM silicon nanoparticle aqueous suspensions were on the order of 10 μM per Gy, ten times higher than that obtained in similar experiments but in the absence of particles. Cytotoxic 1O 2 was generated only in irradiation experiments containing the particles. The particle surface became oxidized to SiO 2 and the luminescence yield reduced with the irradiation dose. Changes in the surface morphology did not affect, within the experimental error, the yields ofROSgenerated per Gy. X-ray irradiation of glioma C6 cell cultures with incorporated silicon nanoparticles showed a marked production of ROS proportional to the radiation dose received. In the absence of nanoparticles, the cells showed no irradiation- enhanced ROS generation. The obtained results indicate that silicon nanoparticles of <5 nm size have the potential to be used as radiosensitizers for improving the outcomes of cancer radiotherapy. Their capability of producing 1O 2 upon X-ray irradiation opens novel approaches in the design of therapy strategies.
Establishment and development of intestinal microbiota in preterm neonates
Establishment and development of intestinal microbiota in preterm neonates
Arboleya, Silvia; Binetti, Ana Griselda; Salazar, Nuria; Fernández, Nuria; Solís, Gonzalo; Hernández Barranco, Ana; Margolles, Abelardo; de los Reyes Gavilán, Clara G.; Gueimonde, Miguel
Microbial colonization of the infant gut is essential for the development of the intestine and the immune system. The profile of intestinal microbiota in the full-term, vaginally delivered, breast-fed infant is considered as ideally healthy. However, in preterm infants this process is challenging, mainly because of organ immaturity, antibiotics use, and hospital stay. To assist in a proper microbiota development in these infants, a detailed knowledge of the colonization process, and the differences from that of full-term breast-fed infants, is needed. We assessed the establishment of the gut microbiota and its metabolic activity in preterm neonates (n = 21) during the first 3 months of life and compared it with that of vaginally delivered, exclusively breast-fed full-term infants (n = 20) using qualitative and quantitative culture-independent methods. Differences in the gut microbiota composition between both groups were observed. Preterm infants showed higher levels of facultative anaerobic microorganisms and reduced levels of strict anaerobes such as Bifidobacterium, Bacteroides, and Atopobium. Short-chain fatty acids concentrations were lower in preterm infants during the first days of life. Alterations occur in the process of microbiota establishment in preterm infants, indicating the need for intervention strategies to counteract them.
Life history schedule and periodic recruitment of female snow crab (Chionoecetes Opilio) in the eastern Bering sea
Life history schedule and periodic recruitment of female snow crab (Chionoecetes Opilio) in the eastern Bering sea
Ernst, Billy; Armstrong, David A.; Burgos, Julián; Orensanz, Jose Maria
Snow crab (Chionoecetes opilio) populations have fluctuated cyclically in eastern Canada and the eastern Bering Sea, where recruitment to the mature female pool has occurred over a period of three decades (1978-2007) in pulses with a mean period of 7 years. It has been hypothesized that this was the result of a parent-offspring relation between sequentially linked strong cohorts of mature primiparous females, which requires that periodicity matches the time lapsed between egg extrusion by the maternal broodstock and the offspring reaching maturity. We show that female age at maturity (post-settlement) varies between 4.5 and 7.5 years, with most females maturing at 5.5-6.5 years (7-8 years after egg extrusion). Pulses of female recruitment to the mature population do not show a latitudinal trend, consistent with uniformity in age-at-maturity. Results of tracking crab abundance and size-frequency distributions in cod stomach and trawl samples between successive pulses of the cycle are consistent with the hypothesis of serial linkage among pulses. Periodicity is reflected in trends of clutch fullness and average shell condition and in the negative correlation between the strength of primiparous female cohorts and the mean size of their members.
Assembly of Pampia to the SW Gondwana margin: A case of strike-slip docking?
Assembly of Pampia to the SW Gondwana margin: A case of strike-slip docking?
Spagnuolo, Cecilia Mariel; Rapalini, Augusto Ernesto; Astini, Ricardo Alfredo
Different hypotheses have been proposed to account for the geologic evolution of the southwestern margin of Gondwana in the Early Paleozoic, involving accretion and displacement of different terranes in a protracted convergent margin. In order to constrain and understand the kinematic and paleogeographic evolution of the Pampia terrane a paleomagnetic study was carried out in different Cambrian to Devonian units of the Eastern Cordillera (Cordillera Oriental) and the Interandean Zone (Interandino) of NW Argentina. Paleomagnetic poles from the Campanario Formation (Middle to Upper Cambrian): 1.5°N 1.9°E A 95=9.2° K=37.46N=8; and Santa Rosita Formation (Lower Ordovician): 8.6°N 355.3°E A 95=10.1° K=26.78 n=9, representative of the Pampia terrane, are interpreted to indicate a Late Cambrian significant displacement with respect to the Río de la Plata and other Gondwana cratons. A model, compatible with several geological evidences that explains this displacement in the framework of the final stages of Gondwana assembly is presented. We propose a simple dextral strike-slip kinematic model in which Pampia and Antofalla (-Arequipa?) blocks moved during Late Cambrian times from a position at the present southern border of the Kalahari craton into its final position next to the Rio de la Plata craton by the Early Ordovician.
The Impact of Seed Dispersal by Black and Gold Howler Monkeys on Forest Regeneration
The Impact of Seed Dispersal by Black and Gold Howler Monkeys on Forest Regeneration
Bravo, Susana Patricia
In Neotropical humid forest, the majority of tree species have seeds dispersed by vertebrates. Seed deposition by vertebrates is often spatially aggregated and a low per capita survival for seeds and seedlings is predicted. However, mortality factors could be saturated by high densities. I evaluated whether recruitment of saplings of species dispersed by black and gold howlers (Alouatta caraya) in latrines is higher than at control sites: (1) below parent trees, (2) in trees not used by monkeys to sleep, (3) randomly chosen sites within the forest, and determined whether howlers may influence current floristic composition of the Paraná River flooded forest. I recorded saplings several years old in the territories of five monkey groups. In total, I found four times more saplings in latrines than in the other areas, and results suggest that latrines are recruitment foci for most species, though larger samples would be required to assess this for every species. Frequency distribution of the diameter of tallest saplings of more abundant species reflected recruitment over time. I found saplings of more species growing in latrines than outside of them. Saplings higher than 1 m of two species of laurels (Ocotea diospyrifolia and Nectandra megapotamica) and one species of Myrtaceae (Eugenia punicifolia) had higher densities in latrines than below parent trees. Results suggest that mortality factors were saturated in latrines and that sapling may grow at a higher rate in latrines. In relation to the influence on floristic composition E. burkartiana, an uncommon species in the forest, could increase in abundance as consequence of seed dispersal by howlers.
Kinetic study of the partial hydrogenation of 1-heptyne on tungsten oxide supported on alumina
Kinetic study of the partial hydrogenation of 1-heptyne on tungsten oxide supported on alumina
Maccarrone, María Juliana; Torres, Gerardo; Lederhos, Cecilia Rosa; Badano, Juan Manuel; Vera, Carlos Roman; Quiroga, Monica Esther; Yori, Juan Carlos
BACKGROUND: Partial hydrogenation of alkynes have industrial and academic relevance on a large scale; industries such as petrochemical, pharmacology and agrochemical use these compounds as raw material. Typical commercial catalysts contains palladium. Finding an economic, active and selective catalyst for the production of alkenes via partial hydrogenation of alkynes is thus an important challenge. On the other hand, the literature on kinetic studies of partial hydrogenation of heavy alkynes is scarce. So the main objectives of this work were to prepare a cheaper catalyst based on low W loading, and study the kinetic of the partial hydrogenation of 1-heptyne. A pseudo-homogeneous and six heterogeneous kinetic models were analyzed. The catalyst was characterized by ICP, XPS, DRX, TPR and hydrogen chemisorption techniques. RESULTS: The characterization results indicate that only WO x species are present on the alumina surface. The WO x/Al 2O 3 catalyst was active and selective for producing 1-heptene even at low reaction temperatures, the partial hydrogenation of 1-heptyne proceeds via two irreversible reactions in parallel. CONCLUSION: The best fit of the experimental data was achieved with a heterogeneous Langmuir-Hinshelwood-Hougen-Watson model in which the rate controlling step is the dissociative adsorption of hydrogen. The activation energy was estimated as E H2 = 34.8 kJ mol -1.
Impacto de las prácticas de crianza sobre el desarrollo de las funciones ejecutivas durante la infancia: Una revisión de la literatura
Impacto de las prácticas de crianza sobre el desarrollo de las funciones ejecutivas durante la infancia: Una revisión de la literatura; Parenting influences on executive functions development during childhood: A review
Stelzer, Florencia; Cervigni, Mauricio Alejandro; Martino, P.
El término prácticas de crianza (PC) hace referencia a una serie de comportamientos y manifestaciones afectivas de los progenitores y/o responsables del menor, que se caracterizan por estar orientados principalmente a la socialización y al cuidado del infante. Diversas investigaciones han hallado un vínculo entre las PC y el desarrollo de ciertas habilidades cognitivas y emocionales del niño. Entre ellas destacan las funciones ejecutivas (FE), que conforman un conjunto de procesos cognitivos de orden superior, cuyo desarrollo está fuertemente asociado a la plasticidad cerebral dependiente de la experiencia. El presente artículo constituye una revisión del vínculo hallado entre las PC y el desarrollo de las FE durante la infancia. El objetivo de este trabajo es presentar los diferentes diseños utilizados para el estudio de la relación entre ambos constructos, confrontando los resultados de las distintas investigaciones. Se concluye señalando que la diversidad metodológica y operativa de los estudios analizados no permite efectuar una afirmación definitiva respecto del vínculo entre las PC y el desarrollo de FE. Por tal motivo, se plasmarán algunas consideraciones metodológicas que podrían clarificar el vínculo entre ambos constructos.; Parenting practices refer to a set of behavioral and emotional manifestations aimed at the socialization and care of children. Several investigations have found relationships between quality of parenting and children’s cognitive and affective development. Among those cognitive processes, the executive functions are strongly associated with brain plasticity which, in turn, is affected by experience. This article is a review of the main links found between parenting practices and the development of executive processes during childhood. The objective of this work is to present different designs used for the study of the relationship between executive functions and parenting practices and to confront their results. It is concluded that the methodological and operational diversity of the analyzed studies does not support a definitive relationship between parenting practices and the development of executive functions. For this reason, some methodological considerations will be made to clarify the relationships between both constructs.
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