5,838 research outputs found
Blogging in the physics classroom: A research-based approach to shaping students' attitudes towards physics
Even though there has been a tremendous amount of research done in how to
help students learn physics, students are still coming away missing a crucial
piece of the puzzle: why bother with physics? Students learn fundamental laws
and how to calculate, but come out of a general physics course without a deep
understanding of how physics has transformed the world around them. In other
words, they get the "how" but not the "why". Studies have shown that students
leave introductory physics courses almost universally with decreased
expectations and with a more negative attitude. This paper will detail an
experiment to address this problem: a course weblog or "blog" which discusses
real-world applications of physics and engages students in discussion and
thinking outside of class. Specifically, students' attitudes towards the value
of physics and its applicability to the real-world were probed using a
26-question Likert scale survey over the course of four semesters in an
introductory physics course at a comprehensive Jesuit university. We found that
students who did not participate in the blog study generally exhibited a
deterioration in attitude towards physics as seen previously. However, students
who read, commented, and were involved with the blog maintained their initially
positive attitudes towards physics. Student response to the blog was
overwhelmingly positive, with students claiming that the blog made the things
we studied in the classroom come alive for them and seem much more relevant.Comment: 20 pages, 6 figure
Amplitude analysis of four-body decays using a massively-parallel fitting framework
The GooFit Framework is designed to perform maximum-likelihood fits for
arbitrary functions on various parallel back ends, for example a GPU. We
present an extension to GooFit which adds the functionality to perform
time-dependent amplitude analyses of pseudoscalar mesons decaying into four
pseudoscalar final states. Benchmarks of this functionality show a significant
performance increase when utilizing a GPU compared to a CPU. Furthermore, this
extension is employed to study the sensitivity on the mixing
parameters and in a time-dependent amplitude analysis of the decay . Studying a sample of 50 000 events and setting
the central values to the world average of and , the statistical sensitivities of and are determined
to be and .Comment: Proceedings of the 22nd International Conference on Computing in High
Energy and Nuclear Physics, CHEP 201
Negative Refraction and Left-handed electromagnetism in Microwave Photonic Crystals
We demonstrate negative refraction of microwaves in metallic photonic
crystals. The spectral response of the photonic crystal, which manifests both
positive and negative refraction, is in complete agreement with band-structure
calculations and numerical simulations. The negative refraction observed
corresponds to left-handed electromagnetism and arises due to the dispersion
characteristics of waves in a periodic medium. This mechanism for negative
refraction is different from that in metamaterials.Comment: 13 pages, 4 figure
Strongly Temperature Dependent Sliding Friction for a Superconducting Interface
A sudden drop in mechanical friction, between an adsorbed nitrogen monolayer
and a lead substrate, occurs when the lead passes through the superconducting
transition temperature. We attribute this effect to a sudden drop at the
superconducting transition temperature of the substrate Ohmic heating. The
Ohmic heating is due to the electronic screening current that results from the
sliding adsorbed film.Comment: Revte
Static and Dry Friction due to Multiscale Surface Roughness
It is shown on the basis of scaling arguments that a disordered interface
between two elastic solids will quite generally exhibit static and "dry
friction" (i.e., kinetic friction which does not vanish as the sliding velocity
approaches zero), because of Tomlinson model instabilities that occur for small
length scale asperities. This provides a possible explanation for why static
and "dry" friction are virtually always observed, and superlubricity almost
never occurs
Static Friction between Elastic Solids due to Random Asperities
Several workers have established that the Larkin domains for two three
dimensional nonmetallic elastic solids in contact with each other at a
disordered interface are enormously large. This implies that there should be
negligible static friction per unit area in the macroscopic solid limit.
The present work argues that the fluctuations in the heights of the random
asperities at the interface that occur in the Greenwood-Williamson model can
account for static friction.Comment: Contains some improvements in the treatment of the subjec
A map from 1d Quantum Field Theory to Quantum Chaos on a 2d Torus
Dynamics of a class of quantum field models on 1d lattice in Heisenberg
picture is mapped into a class of `quantum chaotic' one-body systems on
configurational 2d torus (or 2d lattice) in Schr\" odinger picture. Continuum
field limit of the former corresponds to quasi-classical limit of the latter.Comment: 4 pages in REVTeX, 1 eps-figure include
Association between cognitive performance and cortical glucose metabolism in patients with mild Alzheimer's disease
Background: Neuronal and synaptic function in Alzheimer's disease (AD) is measured in vivo by glucose metabolism using positron emission tomography (PET). Objective: We hypothesized that neuronal activation as measured by PET is a more sensitive index of neuronal dysfunction than activity during rest. We investigated if the correlations between dementia severity as measured with the Mini Mental State Examination (MMSE) and glucose metabolism are an artifact of brain atrophy. Method: Glucose metabolism was measured using {[}F-18]fluorodeoxyglucose PET during rest and activation due to audiovisual stimulation in 13 mild to moderate AD patients (MMSE score >= 17). PET data were corrected for brain atrophy. Results: In the rest condition, glucose metabolism was correlated with the MMSE score primarily within the posterior cingulate and parietal lobes. For the activation condition, additional correlations were within the primary and association audiovisual areas. Most local maxima remained significant after correcting for brain atrophy. Conclusion: PET activity measured during audiovisual stimulation was more sensitive to functional alterations in glucose metabolism in AD patients compared to the resting PET. The association between glucose metabolism and MMSE score was not dependent on brain atrophy. Copyright (C) 2005 S. Karger AG, Basel
Self-Similarity and Localization
The localized eigenstates of the Harper equation exhibit universal
self-similar fluctuations once the exponentially decaying part of a wave
function is factorized out. For a fixed quantum state, we show that the whole
localized phase is characterized by a single strong coupling fixed point of the
renormalization equations. This fixed point also describes the generalized
Harper model with next nearest neighbor interaction below a certain threshold.
Above the threshold, the fluctuations in the generalized Harper model are
described by a strange invariant set of the renormalization equations.Comment: 4 pages, RevTeX, 2 figures include
The model of dynamo with small number of modes and magnetic activity of T Tauri stars
The model that describes operation of dynamo in fully convective stars is
presented. It is based on representation of stellar magnetic field as a
superposition of finite number of poloidal and toroidal free damping modes. In
the frame of adopted low of stellar differential rotation we estimated minimal
value of dynamo number D, starting from which generation of cyclic magnetic
field in stars without radiative core is possible. We also derived expression
for period of the cycle. It was found that dynamo cycles of fully convective
stars and stars with thin convective envelopes differ in a qualitative way: 1)
distribution of spots over latitude during the cycle is different in these
stars; 2) the model predicts that spot formation in fully convective stars
should be strongly suppressed at some phases of the cycle.
We have analyzed historical lightcurve of WTTS star V410 Tau and found that
long term activity of the star is not periodic process. Rather one can speak
about quasi cyclic activity with characteristic time of yr and chaotic
component over imposed. We concluded also that redistribution of cool spots
over longitude is the reason of long term variations of V410 Tau brightness. It
means that one can not compare directly results of photometric observations
with predictions of our axially symmetric (for simplicity) model which allows
to investigate time evolution of spot's distribution over latitude. We then
discuss what kind of observations and in which way could be used to check
predictions of the dynamo theory.Comment: 18 pages, 5 figures, accepted to Astron. Let
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