Actitudes de los estudiantes de ingeniería hacia la química.

This study uses a mixed methods approach —quantitative followed by qualitative— to explore engineering students’ attitudes towards chemistry (N=115). The first phase used a questionnaire to ascertain the perspectives of students and their peers about the chemistry course, course’s relevant aspects, and factors contributing to course difficulty. Contrary to findings reported in other studies, results indicated that most participants had a neutral attitude towards the discipline. The second phase used interviews to explore students’ reasons for having a particular attitude towards chemistry. Participants focused their attention on factors that contribute to their success or failure in the course: time, professor, motivation, academic term, and schedule. How to Cite: Olivo-Delgado, C. J., & Bonilla-Rodríguez, V. E. (2009). Engineering Students’ Attitudes Towards Chemistry. Cuaderno de Investigación en la Educación, 24, 183-212. Retrieved from https://revistas.upr.edu/index.php/educacion/article/view/13555Este estudio utilizó una metodología mixta —cuantitativa seguida por cualitativa— para explorar las actitudes de los estudiantes de ingeniería hacia la química (N=115). La primera fase utilizó un cuestionario para examinar las perspectivas de los estudiantes y sus compañeros acerca del curso de química, aspectos relevantes del curso y factores que contribuyen al nivel de dificultad del mismo. Contrario a los hallazgos de otros estudios, los resultados indicaron que la mayoría de los participantes posee una actitud neutral hacia la disciplina. La segunda fase utilizó entrevistas para explorar las razones de los estudiantes para tener una actitud determinada. Los participantes centraron su atención en factores que contribuyen al éxito o fracaso en el curso: tiempo, profesor, motivación, trimestre y horario. Cómo citar: Olivo-Delgado, C. J., & Bonilla-Rodríguez, V. E. (2009). Engineering Students’ Attitudes Towards Chemistry. Cuaderno de Investigación en la Educación, 24, 183-212. Recuperado de https://revistas.upr.edu/index.php/educacion/article/view/1355

The Black Creole Cuban Pig: origin, evolution and present status

The origin of the Cuban Creole Black pig is under a controversy, but the majority of authors locate their procedure in the ancient Spanish Iberian branches. Others hypothesis point out a possible influence of pre-hispanic Black Canarian pig, and also the early influence of Duroc and Hampshire breeds. Coinciding with all the Cuban farming development, this breed increase greatly their census from the beginning of the colonisation to the first half of the XVIIIth century, when their decreasing started as a consequence of the big expansion of tobacco and sugar Cain agriculture. In the present century this breed was in risk of extinction because the competence of improved foreign breeds, but presently this bred has gain god perspectives, because her role in the Cuban sustainable development.El origen del Cerdo Negro Criollo Cubano sigue siendo discutido, aunque la mayoría de los autores atribuyen su procedencia de los antiguos troncos ibéricos de España. Otras hipótesis plantean una posible influencia de los cerdos canarios prehispánicos e incluso el aporte reciente de sangre de las razas Duroc y Hampshire. Esta raza, coincidiendo con todo el desarrollo ganadero cubano, incrementó enormemente sus censos desde el inicio de la colonización hasta la primera mitad del siglo XVIII donde comenzó su declive a consecuencia de la gran expansión de la explotación tabacalera y de la caña de azúcar. En el presente siglo ha peligrado su conservación por la competencia de las razas selectas extranjeras aunque en la actualidad presenta unas excelentes perspectivas de recuperación dentro del desarrollo sostenible de Cuba

Preliminary study of the genetic differentiation between two variety of cuban creole pig

It is admitted an Iberian origin for the Cuban Creole Pig breed. Inside this breed there exist varieties morphologically very well defined, as the Unhaired and Middlehaired types. The existence of these types is traditionally admitted by Cuban producers, researchers and by the society in general. To confirmate the genetic differentiation of these two morphological types, we have analyzed 93 samples of the breed, with representation of the middlehaired (MD) type (58 animals) and unhaired (UH) type (35 animals) taken from several Cuba provinces. We have used a test of 20 microsatellites of the recommended by FAO/ISAG. The obtained values for the parameters GST (0.74 and 0.12 percent) are extremely low. All these results are showing a no existence of varieties inside the Cuban Creole Pig breed.Al cerdo Criollo Cubano (cCC) se le atribuye un origen ibérico. Dentro de este último existen variedades bien definidas, como la Lampiña y la Entrepelada, las cuales han tenido representación al menos morfológica dentro del cCC. La existencia de estos dos tipos es aceptada en Cuba por productores, investigadores y por la sociedad en general. Con el objetivo de determinar la existencia o no de diferenciación genética entre ellos, se analizaron 93 animales, de ellos, 58 entrepelados y 35 lampiños. Se emplearon 20 microsatélites recomendados por la FAO/ISAG (International Society of Animal Genetics) para estudios de biodiversidad porcina. Los microsatélites se amplificaron mediante la Reacción en Cadena de la Polimerasa (PCR) y los fragmentos amplificados se separaron mediante electroforesis en un secuenciador automático. Los valores que se obtienen en los parámetros GST, 0,74 p.100 y 0,12 p.100 son extremadamente bajos, lo que demuestra que dentro del cCC no existe subdivisión varietal

Electromagnetic multipole moments of elementary spin-1/2, 1, and 3/2 particles

We study multipole decompositions of the electromagnetic currents of spin-1/2, 1, and 3/2 particles described in terms of Lagrangians designed to reproduce representation specific wave equations which are second order in the momenta and which emerge within the recently elaborated Poincar\'e covariant projector method. We calculate the electric multipoles of the above spins for the spinor, the four-vector, and the four-vector--spinor representations, attend to the most general non-Lagrangian spin-3/2 currents which are allowed by Lorentz invariance to be of third order in the momenta and construct the linear current equivalent of identical multipole moments of one of them. We conclude that such non-Lagrangian currents are not necessarily more general than the two-term currents emerging within the covariant projector method. We compare our results with those of the conventional Proca-, and Rarita-Schwinger frameworks. Finally, we test the representation dependence of the multipoles by placing spin-1 and spin-3/2 in the respective (1,0)$\oplus$(0,1), and (3/2,0)$\oplus$(0,3/2) single-spin representations. We observe representation independence of the charge monopoles and the magnetic dipoles, in contrast to the higher multipoles, which turn out to be representation dependent. In particular, we find the bi-vector $(1,0)\oplus (0,1)$ to be characterized by an electric quadrupole moment of opposite sign to the one found in $(1/2,1/2)$, and consequently, to the $W$ boson. Our finding points toward the possibility that the $\rho$ meson could transform as part of an antisymmetric tensor with an $a_{1}$ meson-like state as its representation companion.Comment: 27 pages, 2 figure

Behaviour of the descendent of cuban creole pigs

The present work was proposed to study the behaviour of the Cuban’s pig descendent derived of 27 sow and 5 boar and yours descendent from 93 calving. The animals were exploration by intensive system with lower quality supplements and sweet by sugarcane. The reproductive method utilised was the assisted mount. The results from piglets was: 7.52 total piglet was born; 6.77 piglets was born live; 6.42 weaning piglets; 0.912 kg means of the weight piglets was born live and 6.42 means of piglets weaning. The means of the Cubans Pigs observed in this study was similar with others Cuban and Spanish authors that study this kind of animals. There are differences between the Cubans Pigs and Iberians Pigs, were the Iberians Pigs showed the best weight was born.En este trabajo se estudió el comportamiento de las descendencias de un rebaño de cerdos Criollos Cubanos en pureza, formado por 27 cerdas y 5 sementales y sus descendencias procedentes de 93 partos, explotados en un sistema de crianza estabulado y con un régimen de alimentación basándose en pienso B de baja calidad y suplementados con mieles de caña de azúcar. El método reproductivo empleado fue la monta dirigida. Los resultados del comportamiento de algunos indicadores de camada fueron los siguientes: total de crías nacidas, 7,52; crías nacidas vivas, 6,77; crías destetadas, 6,42; peso promedio de las crías al nacer 0,912 kg y peso promedio de las crías al destete, 6,03 kg. En cuanto al comportamiento medio de las crías nacidas vivas y destetadas se corresponde con reportes de otros autores cubanos que estudian el Cerdo Criollo Cubano y con autores españoles respecto a las variedades del Ibérico. Las diferencias con los animales de este tronco se aprecian al comparar los pesos al nacimiento y a los 30 días de edad, donde el Criollo Cubano se ve superado por las distintas variedades de animales que le dieron origen

Predicción de amputación mediante MESS (Mangled Extremity Severity Score) en pacientes con lesión traumática vascular grave

En este estudio retrospectivo y ciego se analizan las historias clínicas de 60 pacientes (63 miembros inferiores), que ingresaron en nuestro hospital desde 1978 a 1992 a causa de una lesión traumática vascular grave; en este grupo no se incluyeron los pacientes con traumatismo vascular localizado por encima de la cadera o debajo del tobillo. El objetivo del estudio ha sido investigar si el MESS (Mangled extremity severity score) es un sistema útil para decidir entre la amputación precoz o el intento de reconstrucción en este tipo de pacientes. De 36 miembros que terminaron en amputación, 34 tuvieron un MESS de 7 o más, demostrando una sensibilidad del test del 94,4%. De 27 miembros que se salvaron, 22 tuvieron un MESS de 6 o menos, demostrando una especificidad del 81,4%. Así pues, el MESS es un test útil para predecir la necesidad o no de amputar un miembro con lesión vascular traumática grave, pero no es absolutamente fiable. Parece más fiable cuando se aplica a pacientes con traumatismo vascular grave que cuando se aplica a pacientes con traumatismo, tengan o no lesión vascular.60 patients (63 limbs) suffering from a severe vascular injury of the lower extremities between 1978-1992 have been retrospectively reviewed. Those cases wherein vascular injury was located above the hip level or under the ankle level were not included. The aim of this study was to investígate whether the Mangled Extremity Severity Score (MESS) is a useful test to decide between limb salvage or early amputation in this type of patients. Among 36 amputated limbs. 34 had a score equal or greater than 7, the rate of sensitivity of the test was 94,4%. Among 27 salvaged limbs, 22 had a score equal or lower than 6, showing a rate of specificity of 81,4%. The MESS seems to be a very useful test for prediction of limb salvage versus amputation with severe vascular injury, although it is not totally reliable. It seems better when applied to patients with vascular injury, rather than to those with mangled extremity, with or without vascular injury

Valorization of Hemp Core Residues: Impact of NaOH Treatment on the Flexural Strength of PP Composites and Intrinsic Flexural Strength of Hemp Core Fibers

Hemp core is a lignocellulosic residue in the production chain of hemp strands. Huge amounts of hemp core are gathered annually in Europe (43,000 tons) with no major application end. Such lignocellulosic wastes have potential as filling or reinforcing material to replace synthetic fibers and wood fibers in polymer composites. In this study, hemp core biomass was treated under different NaOH concentrations and then defibrated by means of Sprout Waldron equipment to obtain single fibers. Polypropylene matrix was reinforced up to 50 wt.% and the resulting hemp core fibers and the flexural properties were investigated. The results show that the flexural strength of composites increased with the intensity of NaOH treatment. The effect of NaOH was attributed to the removal of extractives and lignin in the fiber cell wall leading to improved interfacial adhesion characteristics. Besides, a methodology was established for the estimation of the intrinsic flexural strength of hemp core fibers. The intrinsic flexural strength of hemp core fibers was calculated to be 940 MPa for fibers treated at 10 wt.% of NaOH. In addition, a relationship between the lignin content and the intrinsic strength of the fibers was established

Co-application of activated carbon and compost to contaminated soils: toxic elements mobility and PAH degradation and availability

This work assesses the suitability of three commercial activated carbons (ACs) and their combination with olive mill waste compost (AC + C) as amendments for the remediation of two different contaminated soils. The treatments were applied to a mining soil, and their ability to immobilize trace elements was evaluated. Besides, the efficiency of the amendments to degrade and reduce the availability of polycyclic aromatic hydrocarbons (PAHs) was investigated in a soil from a wood creosote treatment plant. To this aim, trace elements mobility and PAH degradation and availability were evaluated. Ecotoxicological assays were performed to assess potential toxicity risks in the untreated and the amended soils. In the mining soil, the ACs were able to immobilize metals and As, but the AC + C treatments were more effective than AC. In the PAH-polluted soil, AC treatments promoted the degradation of high molecular weight PAH, but the AC + C amendments further enhanced the degradation of total PAH and reduced the availability of those with 3-rings. The ecotoxicological tests demonstrated an improvement of soil quality when AC and compost were applied together. In conclusion, the co-application of AC and compost reduces the mobility of potentially toxic elements in the polluted mine soil and enhances PAH degradation and reduces PAH availability in the creosote-contaminated soilThis work was fnancially supported by the Ministry of Economy and Competitiveness of Spain, projects CTM2013-47874-C2-R and CTM2013-48697-C2-

Estudio óptico del tamaño y forma de las partículas de polvos de talco

Sorne dusting powders tale have been studied by optic methods. The investigation of the shapes and sizes of the particles, has served to establish two index, which we are named roundish rate and fmeness rateo. These results are very interesting at the topie aplication of the dusting powders tale, because they permit to appreciate a possible irritative action in the skin.Han sido estudiados algunos polvos de talco por métodos opticos. La investigación de las formas y tamaños de las partículas, ha servido para establecer dos índices que hemos denominado, grado de redondearniento y grado de finura. Estos resultados son muy interesantes en la aplicación tópica de los polvos de talco, porque permiten la estimación de una posible acción irritante de la piel