1,500 research outputs found
Barrier Lowering and Field Penetration at Metal-Dielectric Interfaces
We report here photoemission measurements on
Si-SiO_2-Al structures in which the metal-SiO_2
barrier energy has been determined as a function
of the electric field strength E in the dielectric. The
expected barrier lowering is the sum of two terms:
a) the Schottky term, proportional to E^(1/2) and b)
a term due to the penetration of the electric field
into the metal electrode, proportional to E. The
experimental results are in good agreement with
the model, where the Schottky effect involves the
optical value of the dielectric constant of the oxide
and the Thomas-Fermi screening distance in the
metal is 1 Ă
. To our knowledge this represents the
first unambiguous quantitative determination of either effect in a polar dielectric, although the
Schottky effect alone has been observed in silicon
Stability of Solid State Reaction Fronts
We analyze the stability of a planar solid-solid interface at which a
chemical reaction occurs. Examples include oxidation, nitridation, or silicide
formation. Using a continuum model, including a general formula for the
stress-dependence of the reaction rate, we show that stress effects can render
a planar interface dynamically unstable with respect to perturbations of
intermediate wavelength
Using an Escape Room toolbox approach to enhance pharmacology education
Background: Faculty are encouraged to use a variety of teaching/learning strategies to engage nursing students. While simulation and games are now common, there were no reports in the nursing literature using an âescape roomâ concept. Escape rooms use an entertainment approach as teams engage in critical thinking to solve puzzles and find clues to escape a room. In the classroom setting, this concept is modified to solve a mystery by finding various objects through a series of puzzles to locate clues. Some of these games involve finding numerical clues to open locks on a box, such as a toolbox. The purpose of this study was to describe the use of a toolbox gaming strategy based on an escape room concept to help students learn about cardiovascular medications in a pharmacology course. Methods: This pilot study employed a descriptive qualitative method to investigate an approach to pharmacology education. The sample consisted of first semester nursing students. Results: Student responses to criteria-based questions resulted in three themes: engaging, teamwork, and frustration, related to using a toolbox scenario strategy as a pathway to learning. Conclusions: This descriptive study yielded mixed results from the students who were frustrated by time constraints but engaged in the learning experience. Lessons are offered for future improvements
Isoscalar dipole strength in ^{208}_{82}Pb_{126}: the spurious mode and the strength in the continuum
Isoscalar dipole (compression) mode is studied first using schematic
harmonic-oscillator model and, then, the self-consistent Hartree-Fock (HF) and
random phase approximation (RPA) solved in coordinate space. Taking ^{208}Pb
and the SkM* interaction as a numerical example, the spurious component and the
strength in the continuum are carefully examined using the sum rules. It is
pointed out that in the continuum calculation one has to use an extremely fine
radial mesh in HF and RPA in order to separate, with good accuracy, the
spurious component from intrinsic excitations.Comment: 19 pages, 2 figure
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A qualitative study of independent fast food vendors near secondary schools in disadvantaged Scottish neighbourhoods
Background:
Preventing and reducing childhood and adolescent obesity is a growing priority in many countries. Recent UK data suggest that children in more deprived areas have higher rates of obesity and poorer diet quality than those in less deprived areas. As adolescents spend a large proportion of time in school, interventions to improve the food environment in and around schools are being considered. Nutrient standards for school meals are mandatory in the UK, but many secondary pupils purchase foods outside schools at break or lunchtime that may not meet these standards.
Methods:
Qualitative interviews were conducted with fast food shop managers to explore barriers to offering healthier menu options. Recruitment targeted independently-owned shops near secondary schools (pupils aged c.12-17) in low-income areas of three Scottish cities. Ten interviews were completed, recorded, and transcribed for analysis. An inductive qualitative approach was used to analyse the data in NVivo 10.
Results:
Five themes emerged from the data: pride in what is sold; individual autonomy and responsibility; customer demand; profit margin; and neighbourhood context. Interviewees consistently expressed pride in the foods they sold, most of which were homemade. They felt that healthy eating and general wellbeing are the responsibility of the individual and that offering what customers want to eat, not necessarily what they should eat, was the only way to stay in business. Most vendors felt they were struggling to maintain a profit, and that many aspects of the low-income neighbourhood context would make change difficult or impossible.
Conclusions:
Independent food shops in low-income areas face barriers to offering healthy food choices, and interventions and policies that target the food environment around schools should take the neighbourhood context into consideration
Structure and oxidation kinetics of the Si(100)-SiO2 interface
We present first-principles calculations of the structural and electronic
properties of Si(001)-SiO2 interfaces. We first arrive at reasonable structures
for the c-Si/a-SiO2 interface via a Monte-Carlo simulated annealing applied to
an empirical interatomic potential, and then relax these structures using
first-principles calculations within the framework of density-functional
theory. We find a transition region at the interface, having a thickness on the
order of 20\AA, in which there is some oxygen deficiency and a corresponding
presence of sub-oxide Si species (mostly Si^+2 and Si^+3). Distributions of
bond lengths and bond angles, and the nature of the electronic states at the
interface, are investigated and discussed. The behavior of atomic oxygen in
a-SiO2 is also investigated. The peroxyl linkage configuration is found to be
lower in energy than interstitial or threefold configurations. Based on these
results, we suggest a possible mechanism for oxygen diffusion in a-SiO2 that
may be relevant to the oxidation process.Comment: 7 pages, two-column style with 6 postscript figures embedded. Uses
REVTEX and epsf macros. Also available at
http://www.physics.rutgers.edu/~dhv/preprints/index.html#ng_sio
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