Perception, Personal Issues, and Environment of E-Learning: A Causal Model on Student Attitude Towards Online Learning

This study determined the best-fit model for attitude towards online learning of grade 12 students in Region XI based on perception on e-learning, personal issues on e-learning, and the environment of e-learning. This study employed a causal study design and a stratified sampling technique in selecting the 400 respondents. With the electronic survey facility through Google Forms, data were collected utilizing standardized adapted questionnaires. The study utilized the mean, standard deviation, Pearson’s product-moment correlation, regression analysis, and structural equation model as statistical tools. Results revealed that the level of student perception on e-learning was high; the level of their personal issues on e-learning was high; the level of e-learning environment was high; and the level of attitude towards online learning was high. Moreover, a significant relationship existed between the exogenous and endogenous variables. Furthermore, perception on e-learning, personal issues on e-learning, and the e-learning environment influence the attitude towards online learning. Finally, among the five generated models, Model 5 best-fitted student attitude towards online learning in terms of interest in computers and adoption of online learning and ease-ness in using online learning, with perception on e-learning in terms of perceived usefulness of e-learning and perceived self-efficacy of using e-learning; personal issues on e-learning in terms of health, conflict resolution, and motivation; and environment of e-learning in terms of ethics and professionalism, and program effectiveness. Keywords:educational management, perception on e-learning, personal issues on e-learning, e-learning environment, attitude towards online learning, structural equation model, Philippines DOI: 10.7176/JEP/14-15-08 Publication date:May 31st 202

Decoupling of supersymmetric particles

The possibility of a heavy supersymmetric spectrum at the Minimal Supersymmetric Standard Model is considered and the decoupling from the low energy electroweak scale is analyzed in detail. The formal proof of decoupling of supersymmetric particles from low energy physics is stated in terms of the effective action for the particles of the Standard Model that results by integrating out all the sparticles in the limit where their masses are larger than the electroweak scale. The computation of the effective action for the standard electroweak gauge bosons W^{+-}, Z and \gamma is performed by integrating out all the squarks, sleptons, charginos and neutralinos to one-loop. The Higgs sector is not considered in this paper. The large sparticle masses limit is also analyzed in detail. Explicit analytical formulae for the two-point functions of the electroweak gauge bosons to be valid in that limit are presented. Finally, the decoupling of sparticles in the S, T and U parameters is studied analitically. A discussion on how the decoupling takes place in terms of both the physical sparticle masses and the non-physical mass parameters as the \mu-parameter and the soft-breaking parameters is included.Comment: 50 pages, LaTeX + 2 postscript figures. Figures added, some points clarified, one section added, references updated. Accepted to Eur. Phys. J.

Minimal model for calcium alternans due to SR release refractoriness

In the heart, rapid pacing rates may induce alternations in the strength of cardiac contraction, termed pulsus alternans. Often, this is due to an instability in the dynamics of the intracellular calcium concentration, whose transients become larger and smaller at consecutive beats. This alternation has been linked experimentally and theoretically to two different mechanisms: an instability due to (1) a strong dependence of calcium release on sarcoplasmic reticulum (SR) load, together with a slow calcium reuptake into the SR or (2) to SR release refractoriness, due to a slow recovery of the ryanodine receptors (RyR2) from inactivation. The relationship between calcium alternans and refractoriness of the RyR2 has been more elusive than the corresponding SR Ca load mechanism. To study the former, we reduce a general calcium model, which mimics the deterministic evolution of a calcium release unit, to its most basic elements. We show that calcium alternans can be understood using a simple nonlinear equation for calcium concentration at the dyadic space, coupled to a relaxation equation for the number of recovered RyR2s. Depending on the number of RyR2s that are recovered at the beginning of a stimulation, the increase in calcium concentration may pass, or not, over an excitability threshold that limits the occurrence of a large calcium transient. When the recovery of the RyR2 is slow, this produces naturally a period doubling bifurcation, resulting in calcium alternans. We then study the effects of inactivation, calcium diffusion, and release conductance for the onset of alternans. We find that the development of alternans requires a well-defined value of diffusion while it is less sensitive to the values of inactivation or release conductance.Postprint (author's final draft

Pressure dependence of the melting mechanism at the limit of overheating in Lennard-Jones crystals

We study the pressure dependence of the melting mechanism of a surface free Lennard-Jones crystal by constant pressure Monte Carlo simulation. The difference between the overheating temperature($T_{OH}$) and the thermodynamical melting point($T_M$) increase for increasing pressure. When particles move into the repulsive part of the potential the properties at $T_{OH}$ change. There is a crossover pressure where the volume jump becomes pressure-independent. The overheating limit is pre-announced by thermal excitation of big clusters of defects. The temperature zone where the system is dominated by these big clusters of defects increases with increasing pressure. Beyond the crossover pressure we find that excitation of defects and clusters of them start at the same temperature scale related with $T_{OH}$.Comment: 6 pages, 5 figures. Accepted for publication in Physical Review

Diamagnetic interactions in superheated-superconducting microgranules under an external magnetic field

L'estudi de les transicions produïdes en conjunts de grànuls superconductors metastables té nterès tant per a la física fonamental com per a aplicacions com ara els detectors de partícules. L'estudi teòric d'aquest problema ha estat obstaculitzat per la dificultat del tractament de les interaccions diamagnètiques entre grànuls. En aquesta revisió descrivim el comportament d'aquests sistemes, desenvolupem el mètode numèric del tractament i presentem uns quants resultats experimentals i numèrics.The study of the phase transitions produced in ensembles of metastable superconducting granules by magnetic field variations is important both for fundamental physics and for applications in particle detectors. Theoretical study of the problem has long been hampered by the difficulty in dealing with the diamagnetic interactions between granules. In this review we describe the behaviour of such systems, develop numerical procedures to deal with them, and present some experimental and numerical results

Nueva metodología para el cálculo de transformadores en convertidores de potencia multinivel

(Eng) This paper presents a new methodology for the correct design of transformers used in power multilevel inverters common source type. The proposed methodology represents a solution to the problems of distortion in the waveform, voltage drop and loss of efficiency caused by the miscalculation of the transformer using conventional methodology. To validate the methodology two prototypes under different perspectives were built, conventional and proposed, in order to verify the results, which support the solution to the problems described and shown an improvement in performance of the power converter.(Spa) En este trabajo se presenta una nueva metodología para el correcto diseño de transformadores utilizados en inversores de potencia multinivel tipo fuente común. La metodología propuesta representa una solución a los problemas de distorsión en la forma de onda, decaimiento de pulsos en la tensión y pérdida de rendimiento causada por el cálculo del transformador utilizando la metodología convencional. Para validar la metodología se construyen dos prototipos bajo diferentes perspectivas, convencional y propuesta, con el fin de verificar de forma experimental la solución a los problemas descritos y mostrar la mejoría en el rendimiento del convertidor de potencia

Search Space Calculation to Improve Parameter Estimation of Excitation Control Systems

En este artículo se presenta un método para calcular el espacio de búsqueda de cada parámetro del modelo de un sistema de control de excitación. Con el espacio de búsqueda calculado se pretende reducir el número de conjuntos de parámetros solución que pueden ser encontrados por el algoritmo de estimación, reduciendo su tiempo de procesamiento. El método considera un rango de la constante de tiempo del generador sincrónico entre 4s y 10s, un índice de desempeño del sistema de control de excitación, una técnica de diseño de controladores y la estructura del modelo del sistema de control de excitación. Cuando se usa el espacio de búsqueda obtenido para estimar los parámetros, el algoritmo toma menos tiempo de procesamiento y los parámetros estimados son cercanos a los parámetros de referencia.A method to calculate the search space for each parameter in an excitation control system is presented in this paper. The calculated search space is intended to reduce the number of parameter solution sets that can be found by an estimation algorithm, reducing its processing time. The method considers a synchronous generator time constant range between 4s and 10s, an excitation control system performance index, a controller design technique, and the excitation control system model structure. When the obtained search space is used to estimate the parameters, less processing time is used by the algorithm. Also the estimated parameters are closer to the reference ones

Prevalence of parasite intestinal infections in a rural community of the Caribbean north of Colombia

Objectives: To estimate the prevalence of protozoan and helminth infections in a rural town of the Caribbean coast of Colombia and to identify potential risk factors. Methods: The study was conducted in Santa Catalina, a town and municipality located in the Bolívar during 2014. Parasitological analyses were done using 0.85% saline solution and lugol staining. A questionnaire was applied to participants in order to identify possible risk factors for parasite infections. Results: Mean age of sample population (N = 685) was 29.8 SD 622.46 and 68% were females. There is no sewage access in this town. Most of them were infected by any protozoan species (80%) or soil-transmitted helminthes (71%). The most common protozoan found was Entamoeba coli (53%) followed by Giardia duodenalis (13%), Blastocistys hominis (4%) and E. histolytica 82%). Ascaris lumbricoides was the most prevalent helminth (63%) followed by Trichuris trichuria (36%), hookworms (2%), Taenia sp (2%) and Hymenolepys nana (2%). Frequency rates of protozoan and helminthic infections were significantly lower in those living in a house build made of bricks (versus wood or "bahereque") or with a floor material distinct from soil/earth. Drinking boiled water was associated only with lower rates of trichuriasis (aOR: 0.59 95%CI: 0.41-0.78), but not ascariasis. Almost half of of subjects (56%) reported to have received deworming treatment in the last year, but this was not associated with having any parasite infection. In a sub-group of 109 with available data, Ascaris infection was associated with lower hemoglobin levels (B=0.75, SE: 0.25, p = 0.003, adjusted by age and gender). Conclusions: The prevalence of protozoan and helminth infections in this town, representative of the rural area of the Caribbean coast of Colombia, is high. Indicators of poverty and lower hygienic conditions are positively associated with parasite infections