17,119 research outputs found
Length matters: keeping atomic wires in check
Dynamical effects of non-conservative forces in long, defect free atomic
wires are investigated. Current flow through these wires is simulated and we
find that during the initial transient, the kinetic energies of the ions are
contained in a small number of phonon modes, closely clustered in frequency.
These phonon modes correspond to the waterwheel modes determined from
preliminary static calculations. The static calculations allow one to predict
the appearance of non-conservative effects in advance of the more expensive
real-time simulations. The ion kinetic energy redistributes across the band as
non-conservative forces reach a steady state with electronic frictional forces.
The typical ion kinetic energy is found to decrease with system length,
increase with atomic mass, and its dependence on bias, mass and length is
supported with a pen and paper model. This paper highlights the importance of
non-conservative forces in current carrying devices and provides criteria for
the design of stable atomic wires.Comment: 6 pages, 5 figures, conference proceedings from 2014 MRS fall meetin
Nonconservative dynamics in long atomic wires
The effect of nonconservative current-induced forces on the ions in a
defect-free metallic nanowire is investigated using both steady-state
calculations and dynamical simulations. Non-conservative forces were found to
have a major influence on the ion dynamics in these systems, but their role in
increasing the kinetic energy of the ions decreases with increasing system
length. The results illustrate the importance of nonconservative effects in
short nanowires and the scaling of these effects with system size. The
dependence on bias and ion mass can be understood with the help of a simple pen
and paper model. This material highlights the benefit of simple preliminary
steady-state calculations in anticipating aspects of brute-force dynamical
simulations, and provides rule of thumb criteria for the design of stable
quantum wires.Comment: 20 pages, 8 figure
Making and mapping Britainās ānew ordinary eliteā
There has been a sharp intensification in public and academic interest in differing conceptions of an urban āeliteā in recent times. However, the concept of social class in the construction and reproduction of urban elites has remained either an implied or unexplored concern. The purpose of this paper is to explore the empirical manifestations and methodological issues surrounding the definition of an elite which arose from the BBC's Great British Class Survey experiment. This paper builds on our commonplace understanding of an elite as economically distinct by focussing on their social resources and patterns of cultural consumption, based upon a Bourdieusianācapitalsā approach to social class, and highlighting dimensions of this cadre which have hitherto received scant attention in recent public and academic debate
Detection of SiO emission from a massive dense cold core
We report the detection of the SiO (J = 2 - 1) transition from the massive
cold dense core G333.125-0.562. The core remains undetected at wavelengths
shorter than 70 micron and has compact 1.2 mm dust continuum. The SiO emission
is localised to the core. The observations are part of a continuing
multi-molecular line survey of the giant molecular cloud G333. Other detected
molecules in the core include 13CO, C18O, CS, HCO+, HCN, HNC, CH3OH, N2H+, SO,
HC3N, NH3, and some of their isotopes. In addition, from NH3 (1,1) and (2,2)
inversion lines, we obtain a temperature of 13 K. From fitting to the spectral
energy distribution we obtain a colour temperature of 18 K and a gas mass of 2
x 10^3 solar mass. We have also detected a 22 GHz water maser in the core,
together with methanol maser emission, suggesting the core will host massive
star formation. We hypothesise that the SiO emission arises from shocks
associated with an outflow in the cold core.Comment: 6 pages, 4 figures, 1 table, to be published in MNRA
Categories of insight and their correlates: An exploration of relationships among classic-type insight problems, rebus puzzles, remote associates and esoteric analogies.
A central question in creativity concerns how insightful ideas emerge. Anecdotal examples of insightful scientific and technical discoveries include Goodyear's discovery of the vulcanization of rubber, and Mendeleev's realization that there may be gaps as he tried to arrange the elements into the Periodic Table. Although most people would regard these discoveries as insightful, cognitive psychologists have had difficulty in agreeing on whether such ideas resulted from insights or from conventional problem solving processes. One area of wide agreement among psychologists is that insight involves a process of restructuring. If this view is correct, then understanding insight and its role in problem solving will depend on a better understanding of restructuring and the characteristics that describe it.
This article proposes and tests a preliminary classification of insight problems based on several restructuring characteristics: the need to redefine spatial assumptions, the need to change defined forms, the degree of misdirection involved, the difficulty in visualizing a possible solution, the number of restructuring sequences in the problem, and the requirement for figure-ground type reversals. A second purpose of the study was to compare performance on classic spatial insight problems with two types of verbal tests that may be related to insight, the Remote Associates Test (RAT), and rebus puzzles. In doing so, we report on the results of a survey of 172 business students at the University of Waikato in New Zealand who completed classic-type insight, RAT and rebus problems
High School Athletic Directors Perceptions of Athletic Trainer\u27s Professional Knowledge and Competence Based on Attire
Very little research is available to identify how attire in the athletic training field impacts perceptions of professional knowledge and competence. The purpose of this study was to identify the effect of attire on high school athletic directorsā perceptions of an athletic trainerās professional knowledge and competence. The researcher emailed a questionnaire to ninety-four high school athletic directors from the state of California. The questionnaire measured the effect of attire on the perceptions of skills, knowledge, approachability, experience, education level, overall competence, and representation of an athletic trainer and focused on the difference between khaki attire, professional attire, and workout attire in relationship to perceived knowledge and competence. The respondents rated khaki attire highest followed by professional attire and workout attire when evaluating skills, approachability, overall competence, experience, and knowledge. Representation and education level rated khaki attire as the highest, followed by professional attire, and workout attire rated the lowest. These results indicate khaki attire as the most appropriate attire for high school athletic trainers to wear to achieve the highest perceptions of competence and knowledge from high school athletic directors
Parametric vision simulation study, part 2 Final report
Effects of landing site redesignation on visibility during manned lunar landin
Elemental Abundances in M31: Alpha and Iron Element Abundances from Low-Resolution Resolved Stellar Spectroscopy in the Stellar Halo
Measurements of [Fe/H] and [/Fe] can probe the minor merging history
of a galaxy, providing a direct way to test the hierarchical assembly paradigm.
While measurements of [/Fe] have been made in the stellar halo of the
Milky Way, little is known about detailed chemical abundances in the stellar
halo of M31. To make progress with existing telescopes, we apply spectral
synthesis to low-resolution DEIMOS spectroscopy (R 2500 at 7000
Angstroms) across a wide spectral range (4500 Angstroms 9100
Angstroms). By applying our technique to low-resolution spectra of 170 giant
stars in 5 MW globular clusters, we demonstrate that our technique reproduces
previous measurements from higher resolution spectroscopy. Based on the
intrinsic dispersion in [Fe/H] and [/Fe] of individual stars in our
combined cluster sample, we estimate systematic uncertainties of 0.11 dex
and 0.09 dex in [Fe/H] and [/Fe], respectively. We apply our
method to deep, low-resolution spectra of 11 red giant branch stars in the
smooth halo of M31, resulting in higher signal-to-noise per spectral resolution
element compared to DEIMOS medium-resolution spectroscopy, given the same
exposure time and conditions. We find [/Fe] = 0.49
0.29 dex and [Fe/H] = 1.59 0.56 dex for our
sample. This implies that---much like the Milky Way---the smooth halo of M31 is
likely composed of disrupted dwarf galaxies with truncated star formation
histories that were accreted early in the halo's formation.Comment: 21 pages, 14 figures, accepted to Ap
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