Kelvin-Helmholtz versus Hall Magneto-shear instability in astrophysical flows

We study the stability of shear flows in a fully ionized plasma. Kelvin-Helmholtz is a well known, macroscopic and ideal shear-driven instability. In sufficiently low density plasmas, also the microscopic Hall magneto-shear instability can take place. We performed three-dimensional simulations of the Hall-MHD equations where these two instabilities are present, and carried out a comparative study. We find that when the shear flow is so intense that its vorticity surpasses the ion-cyclotron frequency of the plasma, the Hall magneto-shear instability is not only non-negligible, but it actually displays growth rates larger than those of the Kelvin-Helmholtz instability

Quantum magnons of the intermediate phase of half-doped manganite oxides

At half doping, the ground state of three-dimensional manganite perovskite oxides like R$_{1-x}$Ca$_x$MnO$_3$, where R is a trivalent ion such as La, Pr, etc, is still unclear. Many experimental findings agree better with the combined magnetic, charge, and orbital order characteristic of the "intermediate phase", introduced by Efremov et al. in 2004 [Nature Mats. 3, 853]. This phase consists of spin dimers (thus incorporating aspects of the Zener polaron phase (ZP) proposed in 2002 by Daoud-Aladine et al. [Phys. Rev. Lett. 89, 097205]), though formed by a pair of parallel Mn spins of different magnitude, in principle (thereby allowing for a degree of Mn charge disproportionation: not necessarily as large as that of Mn$^{3+}$-Mn$^{4+}$ in Goodenough's original CE phase [Phys. Rev. 100, 564 (1955)]). In the intermediate phase, consecutive spin dimers localed along the planar zig-zag chains are oriented at a constant relative angle $\Phi$ between them. Varying Mn-charge disproportionation and $\Phi$, the intermediate phase should allow to continuously interpolate between the two limiting cases of the CE phase and the dimer phase denoted as "orthogonal intermediate $\pi/2-$phase". It is not easy to find a microscopic model able to describe the phenomenological intermediate phase adequately for the spin, charge, and orbital degrees of freedom simultaneously. Here, we study the quantum spin excitations of a planar model of interacting localized spins, which we found can stabilize the intermediate phase classically. We compare the quantum magnons of the intermediate phase with those of the CE and orthogonal $\pi/2$ phases, in the context of recent experimental results.Comment: 5 pages, 8 figures Manuscript accepted 29 April 2013, by IEEE - Transactions on Magnetic

Un urbanismo depredador

La inseguridad en el diseño y la construcción generan consecuencias en la ciudad, ocasionando un impacto perjudicial de múltiples aspectos. Esto me hace reflexionar sobre las medidas que debieran tomarse junto a un cambio de mentalidad en la incorporación de valores perdidos, bajo una mirada ética del diseño y de su entorno. Lentamente se ha ido desarrollando una caótica resultante en la infraestructura urbanística, una omisión en la toma de medidas a ejecutarse, tanto desde el aspecto, edilicio, vial, así como de los servicios en general, proceso que hoy toma sólo la forma de un enlentecimiento casi inmanejable del tránsito pero que a futuro, con la puesta en marcha de estas construcciones, se verá afectada seguramente la calidad de vida de los que habitan dentro de las áreas urbanas. La calle Hipólito Irigoyen de la ciudad de Mendoza, es un borde urbano que define la diferencia de jurisdicciones entre la comuna de Godoy Cruz y de Capital. La puesta en práctica de los FOT y FOS actuales, marca la clara intención de lograr una mayor densificación, hecho visible en dicho encuentro, volviéndose un claro ejemplo de estos interrogantes, sobre los que tanto la arquitectura como la ingeniería debieran reflexionarThe uncertainty in the design and construction, move their consequences to the city generating a negative impact on the city comes from it. This makes me reflect about measures that would be taken along with a change of mind on the incorporation of missing values, under an ethical view of design and its environment. Slowly, it has developed a chaotic urban infrastructure, resulting in a failure to take measures to run both road appearance, building, and the services in general, a process that today takes the form of an almost slowing unmanageable traffic and in the future, with the commissioning of these buildings (energy intensive) will be affected the quality of life of those living in urban areas nearby. Hipólito Irigoyen street is an urban edge that makes the difference of jurisdiction between the district of Godoy Cruz and Capital. The implementation of the FOT and FOS makes a clear intention to achieve higher density, a fact that impacts differently in that meeting and becomes the visible example of these questionsPeer Reviewe

MIXED METHOD ANALYSIS IN ASSESSING THE EFFECTIVENESS OF INTENTIONAL LEARNING INSTRUMENTS IN TEACHING CIRCUITS

Research results on Intentional Learning proved positive implications in the teaching and learning processes.  In this study, the researcher analyzed data gathered from the implementation of Intentional Learning Questionnaire in Electric Circuit (ILQ-EC) and Intentional Learning Module (ILM) as the intentional learning instruments. The over-all study involves implementation of ILQ-EC, development of ILM and testing its effectiveness using quantitative and qualitative research analysis. Previous research used ILQ-EC in identifying motivation and learning strategies factors which were highly correlated and predictive to conceptual understanding of student respondents. These factors served as the benchmark in the development and testing of ILM for this present study. Results for both quantitative and qualitative analysis showed that high gainers tend to be more intentional, specifically, more critical thinker and with higher perceived competence than low gainers. Moreover, average normal gains of the student-participants after using ILM was higher compared to previous research results using different learning approaches. ILM evaluation based on student responses also confirmed the influence of ILM in their learning gains. Thus, enhancing intentionality proved significant effect in the teaching and learning process

Tendencia contra tendencia

Peer Reviewe

GRAPHIC ORGANIZER: A LEARNING TOOL IN TEACHING PHYSICAL SCIENCE

The integration of the effective study techniques could still be a relevant education research topic if we are to consider the changing demand for skills brought about by technological advancements. Thus, Graphic Organizer as a teaching tool was developed and implemented to promote conceptual understanding in the solution processes of algorithmic related topics in Physical Science. Specifically, the study determined the level of academic achievement of the participants in the pretest and posttest assessment of a quasi-experimental research design. Further, this study also determined which group (control or experimental) performed better after applying the intervention. Results showed that the control and experimental groups pretest scores do not meet expected proficiency level, however, there was a significant improvement in their posttests scores described respectively as satisfactory and very satisfactory. It was found out further that participants from experimental group achieved significantly better than the participants from the control group. As observed, the participants have confidently and actively indulged themselves in graphic organizer guided activities resulting to a deeper understanding of concepts, retention, and mastery of contents.&nbsp

Stripping the 21st Century Classroom Naked: Treachery or Technique?

Some things at a glance though not desirable could be tolerated and ignored in this 21st century regarding the outlook of a typical classroom but not a naked classroom The paradigm shift in the age of the technology driven instructional delivery is a classroom equipped with modern technological tools for enhancing teaching and learning The new age schools and educational institutions pride themselves as having learning delivered by state-of-the-art technology thus classrooms having the touch of information and communication technology equipment and teachers who are trained in the art students as digital natives etc Anyone who thinks otherwise stripping classroom naked must be living in the past would be the immediate response to such postulation This paper take a critical look at a naked classroom in bid to unravel whether so doing has any relevance a technique or a fallacy The paper makes conclusion and recommendations amongst others that our classrooms should be reserved for useful face-to-face discussions and engaging students by using technology outside the classroo