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Search Results: 1 - 10 of 483536 matches for " Luis A.; "
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Introducing Engineering Students to Historical/Cultural Perspectives through Story-Centered On-Line Learning  [PDF]
Luis A Godoy
Creative Education (CE) , 2011, DOI: 10.4236/ce.2011.22009
Abstract: Several authors argued that history of science should be an integral part of science education; however, there are many obstacles to carry out an implementation within this approach, including that lecturers normally lack a necessary historical background (a situation that is largely aggravated in engineering faculties), and the impossi- bility of including new courses or credits in an already tight curriculum. The development of on-line modules that engineering students can work outside their normal schedule of classes, introducing historical/cultural per- spectives, is presented in this paper. E-learning and knowledge management strategies are used in the context of science education at undergraduate and graduate levels. The approach is based on learning-by-doing in a virtual environment, and specifically presents story-centered activities, in which the student is faced with a problem and plays the role of an expert to provide a solution to the case. The specific case considered develops in the form of a controversy concerning the origin of the studies of column buckling. Two sets of information are available for navigation in the module: specific information that the student can explore (containing historical material di- rectly connected to the case provided), and more general information (providing the historical/cultural context to the problem). A first application has been made with civil engineering students, who had to write a two-page white paper as a consequence of their work on the problem. The interest generated in the participating students and the positive evaluation of their experience seems to indicate that this type of activity can serve to enhance traditional engineering lectures by incorporating a historical dimension. The present web-based approach could be extended to tackle similar conflicts in fields for which there is ample documentation available in the literature or in other historical episodes which may lead to rich discussions.
Positron Emission Tomography-Computed Tomography (PET-CT) in Head and Neck Pathology  [PDF]
Luis A. Tamara, Ines Velez, Claudia Tamara
Open Journal of Radiology (OJRad) , 2011, DOI: 10.4236/ojrad.2011.11002
Abstract: Cancer of the head and neck is often devastating and the morbidity associated with its treatment is substantial. Positron Emission Tomography-Computed Tomography (PET-CT) combines the power of biological / molecular imaging with the anatomic detail of CT in order to provide a very sensitive and specific imaging tool for the evaluation of head and neck pathology. PET can aid the clinician in establishing diagnosis, staging, (It has been shown to be more accurate than CT), assessing, prognosis and determining response to therapy. Lymphoma, melanoma, multiple myeloma, leukemia, salivary gland tumors, odontogenic carcinomas, soft tissue sarcomas, thyroid, parathyroid, lacrimal gland and bone / cartilage tumors are some of the entities where PET-CT may be useful. (Tumors of salivary glands and of odontogenic tissue are particularly difficult to diagnose due to the relative infrequency when compared with other tumors and the extremely vast histologic variation).It is important to note that carcinoma metastasis, is the most common malignancy found within the mandibular bone. PET-CT and skeletal scintigraphy are both very sensitive and specific in these types of patients.
Replacement of Soybean Meal with Lupin or Chickpea Seed Meal in Diets for Fattening Iberian Pigs Promotes a Healthier Ileal Microbiota Composition  [PDF]
Luis A. Rubio, M. Jesús Peinado
Advances in Microbiology (AiM) , 2014, DOI: 10.4236/aim.2014.49055

Five castrated male Iberian pigs (100 ± 2 kg b.w.) fitted with T-shaped ileal cannulas at the terminal ileum were used to determine the effects of legume feeding on intestinal microbiota composition. The diets were based on defatted soybean (Glycine max), lupin (Lupinus angustifolius) or chickpea (Cicer arietinum) seed meals and contained similar amounts of digestible energy (14.2 - 15.1 MJ·kg-1) and protein (107 g·kg-1). A hydrolyzed casein diet was used to determine the bacterial counts in pigs fed on a vegetable-free diet. The composition of the intestinal microbiota at the terminal ileum was analysed by q-PCR. Higher (P < 0.05) lactobacilli log10 number of copies was determined in the ileal contents of pigs fed on lupin- or chickpea-based diets with respect to those fed on the soybean-based diet. Bacteroides and the Clostridium coccoides/Eubacterium rectale group log10 number of copies was lower (

Structural Patterns of Immunoreactivity to Cytokeratin 18 in Normal Prostate and Benign Prostate Hyperplasia: Global and Local Differences  [PDF]
Luis Santamaría, Ildefonso Ingelmo, Fernando Teba
Open Journal of Pathology (OJPathology) , 2017, DOI: 10.4236/ojpathology.2017.72004
Abstract: Background: Benign prostate hyperplasia (BPH) is the most common benign disease of the human prostate. The comparison between global versus local changes in spatial patterns of pathological lesions provoked a growing interest in some fields such as neuropathology. To date, there is little data on this subject in prostatic pathology. Given the interest of local parameters to distinguish between normal and pathological structures, the present study will apply first and second order stereological tools to find out if the cytokeratin18 (ck18) immunoexpression shows relevant local changes in BPH compared to normal prostate, independently if global estimates were similar in both groups. Methods: To verify if the global and local changes in immuno-expression of ck18 are relevant to ascertain differences between normal (CTR) and BPH cases, the following parameters will be applied: Volume fraction of epithelium immunostained for ck18 (VV ck18), both in global and local estimates; dispersion indices of VV ck18; estimates of local variance of VV ck18 (positional and of scale) using wavelet analysis; and lacunarity analysis to measure the tissue heterogeneity. Then, the set of values from the parameters studied that show significant differences between CTR and BPH will be employed to perform stepwise linear discriminant analyses to determine if locally estimated parameters were able to classify accurately the cases in CTR and BPH groups. Results and Conclusions: The findings of the present study indicate that changes in the expression of ck18 by the hyperplastic prostatic epithelium are not homogeneous. This limits the use of a single biopsy based markers to predict biological behavior in BPH. On the other hand, the local changes in the expression of ck18 are more evident in terms of VV ck18 and its local variability, whereas other parameters that are useful in other pathologies, such as lacunarity, are less relevant In prostatic hyperplasia.
Nitrogen Injection in Molten Aluminum in a Tank Degasser  [PDF]
Luis A. Maldonado, Miguel A. Barron, Dulce Y. Miranda
World Journal of Engineering and Technology (WJET) , 2018, DOI: 10.4236/wjet.2018.64044
Abstract: The injection of nitrogen in molten aluminum through a static impeller in a tank degassing unit is studied. Using basic principles of fluid mechanics, it is analyzed the influence of the nozzle diameter on the bubble diameter and the mean residence time of the bubbles in the molten aluminum. By means of transient isothermal 2D Computational Fluid Dynamics (CFD) simulations, the influence of the nitrogen volumetric flow rate on the phase distributions and the tank degasser dynamics is studied. Finally, an adiabatic CFD simulation is carried out in order to elucidate the changes in the molten aluminum temperature due to the injection of nitrogen at ambient temperature. This simulation shows that molten aluminum does not suffer drastic temperature reductions given that, in spite?that?the nitrogen is fed at ambient temperature, the mass of nitrogen is relatively small compared with the mass of aluminum.
Sobre la estructura de las analogías en ciencias
Godoy,Luis A;
Interciencia , 2002,
Abstract: this work presents an analysis about the nature of analogies in scientific practice. several perspectives of study are considered, together with functions and the structures of the analogies in science. a structure of analysis is proposed that includes the limitations of the analogical relation and the consequences that result from the analogy. furthermore, a classification is proposed to identify analogies according to the structure and the limitations found.
Acta Biológica Colombiana , 2011,
Abstract: the temporal scale of our daily life is a small fraction of the evolutionary history of organisms, including the humans. the planet age is estimated in 4.5 billion years, in which profound changes in the position of continents and the climate of the earth occurred. nevertheless, most drastic changes arose just in the last 500 million years. the genetics has been a fundamental tool to infer the organismal change throughout billions, thousands and millions of years, for example through the estimation of divergence times. living organisms share the genetic material as a molecular fingerprint to trace changes in the past. thus, by using dna and protein sequences, scientists may understand how the living organisms have evolved, when important evolutionary novelties arose, how genes interact, and determine the evolutionary relationships between past and contemporary forms. the relationships among organisms are inferred by simple similarity (phenetic relationships), by sharing unique features and throughout mathematical models that describe how dna sequences or proteins evolve (phylogenetic relationships). genetics also evidences the dynamics of genomes (duplication, transposition, recombination, inversions) that results in gene gain and loss, new functions, and horizontal gene transfer, mechanisms that increase today?s existing diversity. although the environment is fundamental in the evolution of organisms, it is essential to recognize that there is a very thin and strong thread that connects us inevitably to those first molecules formed in the distant past.
Conflictos en los servicios esenciales: fijación de los servicios mínimos. Aspectos conflictivos. Doctrina judicial
Raffaghelli,Luis A;
Gaceta Laboral , 2007,
Abstract: this study presents a review of different legislative aspects and their jurisprudential interpretation regarding problems generated by fixing minimum services for essential services in collective labor conflicts. during a conflict, the character of rendering services for activities considered essential displaces the axis of the company-worker relationship in order to preserve indispensable services for the community. minimal services should be fixed by the authority of an impartial third entity, since it is not possible to leave this responsibility to the company. minimum services do not alter the nature of the work performed, but they do cease responding to the contractual synallagma, since the work-for-salary exchange goes to the service for protecting the community?s fundamental rights. when the company designates personal for minimal shifts, it should adjust to what is agreed on in the collective agreement, act by governmental delegation, comply with the impartial third-party entity directive, and not be able to exercise in kind its power of management.
Aproximación al diagnóstico diferencial de las quemaduras intencionales en los ni?os
Ceballos García,Luis;
Gaceta Médica de Caracas , 2005,
Abstract: the diagnosis of intentional burning may be too difficult to do, and because of these difficulties the serious problem of the battered child syndrome is often not recognized by the attendant physicians. the omission of the opportune diagnosis may be deleterious for the victims if they come back home. another problem regarding the same difficulties is the overdiagnosis of maltreatment. so, innocent people may be unjustly accused and prosecuted. this paper considers the differential diagnosis of intentional and non-intentional burns, and of certain pathological conditions that may mimic maltreatment.
Comités Escolares de Prevención de Accidentes y Lesiones (COMPALES)
Ceballos García,Luis;
Gaceta Médica de Caracas , 2005,
Abstract: the teaching learning pattern that is presented as an educational strategy for the prevention of accidents and unintentional injuries in children and in adolescents has, as action axis, the binomial home-school, transforming the teachers into facilitators of the program, the students in receivers and promoters of the information, and the parents in companions of the process. it incorporates statistical indicators of accidentally to incentives in the educational communities, the competition for the achievement of the best numbers of student hours without accidents. in order to stimulate the learning of the basic concepts of prevention, we appeal to the use of poetical resources
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