282 research outputs found
Predictive Ansatz for Fermion Masses in SUSY GUTS
We reexamine a succesful fermion mass Ansatz proposed by Giudice for a wide
range of the ratio (where are
the two standard higgs fields), in the context of supersymmetric grand unified
theories. We find that the 7 predictions of the ansatz, and are in good agreement with the experiment when
either {\it i) } or {\it ii)} . A correct
prediction for the bottom mass gives a lower limit on for case
{\it (i)}, in agreement with the previous analysis, while in case {\it (ii)}
.Comment: 8 pages, 3 figures NOT included, available on request, LaTex, IOA
281/92, NTUA 37/92 preprint
High-Temperature Superconducting Level Meter for Liquid Argon Detectors
Capacitive devices are customarily used as probes to measure the level of
noble liquids in detectors operated for neutrino studies and dark matter
searches. In this work we describe the use of a high-temperature
superconducting material as an alternative to control the level of a cryogenic
noble liquid. Lab measurements indicate that the superconductor shows a linear
behaviour, a high degree of stability and offers a very accurate determination
of the liquid volume. This device is therefore a competitive instrument and
shows several advantages over conventional level meters.Comment: 13 pages, 11 figures. Accepted for publication in JINS
From teaching physics to teaching children : beginning teachers learning from pupils
This paper discusses the development of beginning physics teachers' pedagogical content knowledge (PCK) in the context of teaching basic electricity during a one-year Professional Graduate Diploma in Education course (PGDE) and beyond. This longitudinal study used repeated semi-structured interviews over a period of four-and-a-half years. The interview schedule followed a line of development through the secondary school electrical syllabus in Scotland. Fifteen student teachers were interviewed during the PGDE year. Six of them were followed up at the end of the Induction Year (their first year as a newly qualified teacher), and again two-and-a-half years later. Thematic analysis of the interviews showed that before the beginning teachers had taught any classes, their initial focus was on how to transform their own subject matter knowledge (SMK) about electricity into forms that were accessible to pupils. As the beginning teachers gained experience working with classes, they gave vivid descriptions of interacting with particular pupils when teaching electricity which showed the development of their pedagogical knowledge. This played a significant role in the teachers' change of focus from teaching physics to teaching children as they transformed their SMK into forms that were accessible to pupils and developed their general pedagogical knowledge
Convection in colloidal suspensions with particle-concentration-dependent viscosity
The onset of thermal convection in a horizontal layer of a colloidal
suspension is investigated in terms of a continuum model for binary-fluid
mixtures where the viscosity depends on the local concentration of colloidal
particles. With an increasing difference between the viscosity at the warmer
and the colder boundary the threshold of convection is reduced in the range of
positive values of the separation ratio psi with the onset of stationary
convection as well as in the range of negative values of psi with an
oscillatory Hopf bifurcation. Additionally the convection rolls are shifted
downwards with respect to the center of the horizontal layer for stationary
convection (psi>0) and upwards for the Hopf bifurcation (psi<0).Comment: 8 pages, 6 figures, submitted to European Physical Journal
Frequency behavior of Raman coupling coefficient in glasses
Low-frequency Raman coupling coefficient of 11 different glasses is
evaluated. It is found that the coupling coefficient demonstrates a universal
linear frequency behavior near the boson peak maximum and a superlinear
behavior at very low frequencies. The last observation suggests vanishing of
the coupling coefficient when frequency tends to zero. The results are
discussed in terms of the vibration wavefunction that combines features of
localized and extended modes.Comment: 8 pages, 9 figure
Recent Advances in Understanding Particle Acceleration Processes in Solar Flares
We review basic theoretical concepts in particle acceleration, with
particular emphasis on processes likely to occur in regions of magnetic
reconnection. Several new developments are discussed, including detailed
studies of reconnection in three-dimensional magnetic field configurations
(e.g., current sheets, collapsing traps, separatrix regions) and stochastic
acceleration in a turbulent environment. Fluid, test-particle, and
particle-in-cell approaches are used and results compared. While these studies
show considerable promise in accounting for the various observational
manifestations of solar flares, they are limited by a number of factors, mostly
relating to available computational power. Not the least of these issues is the
need to explicitly incorporate the electrodynamic feedback of the accelerated
particles themselves on the environment in which they are accelerated. A brief
prognosis for future advancement is offered.Comment: This is a chapter in a monograph on the physics of solar flares,
inspired by RHESSI observations. The individual articles are to appear in
Space Science Reviews (2011
- …