1,487 research outputs found
Path Integral Solution by Sum Over Perturbation Series
A method for calculating the relativistic path integral solution via sum over
perturbation series is given. As an application the exact path integral
solution of the relativistic Aharonov-Bohm-Coulomb system is obtained by the
method. Different from the earlier treatment based on the space-time
transformation and infinite multiple-valued trasformation of
Kustaanheimo-Stiefel in order to perform path integral, the method developed in
this contribution involves only the explicit form of a simple Green's function
and an explicit path integral is avoided.Comment: 13 pages, ReVTeX, no figure
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National culture and on-line trust: a study of internet Egyptian users
This research-in-progress investigates cultural issues in e-commerce trust. An experiential survey was conducted with three hundred and seventy Egyptian Internet users, exploring two book-seller web sites. Structure equation modeling analysis suggested that, for the target sample, perceived reputation and perceived familiarity with an Internet store have significant effect on building trust for that store. The paper discusses the importance of these two factors within the Egyptian culture
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Multimodal and ubiquitous computing systems: supporting independent-living older users
We document the rationale and design of a multimodal interface to a pervasive/ubiquitous computing system that supports independent living by older people in their own homes. The Millennium Home system involves fitting a resident’s home with sensors – these sensors can be used to trigger sequences of interaction with the resident to warn them about dangerous events, or to check if they need external help. We draw lessons from the design process and conclude the paper with implications for the design of multimodal interfaces to ubiquitous systems developed for the elderly and in healthcare, as well as for more general ubiquitous computing applications
Algebraic entropy for algebraic maps
We propose an extension of the concept of algebraic entropy, as introduced by Bellon and Viallet for rational maps, to algebraic maps (or correspondences) of a certain kind. The corresponding entropy is an index of the complexity of the map. The definition inherits the basic properties from the definition of entropy for rational maps. We give an example with positive entropy, as well as two examples taken from the theory of Backlund transformations
Thermal Conductivity of Single Wall Carbon Nanotubes: Diameter and Annealing Dependence
The thermal conductivity, k(T), of bulk single-wall carbon nanotubes (SWNT's)
displays a linear temperature dependence at low T that has been attributed to
1D quantization of phonons. To explore this issue further, we have measured the
k(T) of samples with varying average tube diameters. We observe linear k(T) up
to higher temperatures in samples with smaller diameters, in agreement with a
quantization picture. In addition, we have examined the effect of annealing on
k(T). We observe an enhancement in k(T) for annealed samples which we attribute
to healing of defects and removal of impurities. These measurements demonstrate
how the thermal properties of an SWNT material can be controlled by
manipulating its intrinsic nanoscale properties.Comment: Proc. of the XV. Int. Winterschool on Electronic Properties of Novel
Materials, Kirchberg/Tirol, Austria, 200
Thermal transport measurements of individual multiwalled nanotubes
The thermal conductivity and thermoelectric power of a single carbon nanotube
were measured using a microfabricated suspended device. The observed thermal
conductivity is more than 3000 W/K m at room temperature, which is two orders
of magnitude higher than the estimation from previous experiments that used
macroscopic mat samples. The temperature dependence of the thermal conductivity
of nanotubes exhibits a peak at 320 K due to the onset of Umklapp phonon
scattering. The measured thermoelectric power shows linear temperature
dependence with a value of 80 V/K at room temperature.Comment: 4 pages, figures include
Backlund transformations for many-body systems related to KdV
We present Backlund transformations (BTs) with parameter for certain
classical integrable n-body systems, namely the many-body generalised
Henon-Heiles, Garnier and Neumann systems. Our construction makes use of the
fact that all these systems may be obtained as particular reductions
(stationary or restricted flows) of the KdV hierarchy; alternatively they may
be considered as examples of the reduced sl(2) Gaudin magnet. The BTs provide
exact time-discretizations of the original (continuous) systems, preserving the
Lax matrix and hence all integrals of motion, and satisfy the spectrality
property with respect to the Backlund parameter.Comment: LaTeX2e, 8 page
Inverse problems associated with integrable equations of Camassa-Holm type; explicit formulas on the real axis, I
The inverse problem which arises in the Camassa--Holm equation is revisited
for the class of discrete densities. The method of solution relies on the use
of orthogonal polynomials. The explicit formulas are obtained directly from the
analysis on the real axis without any additional transformation to a "string"
type boundary value problem known from prior works
Socioeconomic and racial/ethnic inequalities in depression prevalence and the treatment gap in Brazil: A decomposition analysis.
Depression is a major global health burden and there are stark socioeconomic inequalities in both the prevalence of depression and access to treatment for depression. In Brazil, racial/ethnic inequalities are of particular concern, but the factors contributing to these inequalities remain mostly unknown. This paper firstly explores determinants of depression and the treatment gap (i.e., untreated afflicted individuals) in Brazil and identifies if socio-economic and health system factors explain changes over time. Secondly, it analyses income and racial/ethnic inequalities in depression and the treatment gap and identifies factors explaining inequalities through decomposition methods. Data from two waves (2013 and 2019) of a representative household-based survey are used. In 2019, 10.8% of adults were depressed, but over 70% of depressed adults did not receive care. Black or brown/mixed Brazilians were more likely to have untreated depression, and region of residence was the most important determinant of these racial/ethnic inequalities. Notably, 44.6% of the difference in the treatment gap between white individuals and black and brown/mixed individuals was not explained by differences in observables, which could potentially be due to discrimination or difficulties in accessing treatment due to other non-observable characteristics. Employment, age, exposure to violence and physical activity are the main contributing factors to income inequalities in depression. These results suggest that policies aimed at improving the levels of exposure of lower-income individuals to risk factors may positively impact mental health and mental health inequalities, while addressing inequalities in service provision and resourcing for mental health and tackling barriers to access stemming from discrimination are essential to bridge the treatment gap equitably
Ac Stark Effects and Harmonic Generation in Periodic Potentials
The ac Stark effect can shift initially nonresonant minibands in
semiconductor superlattices into multiphoton resonances. This effect can result
in strongly enhanced generation of a particular desired harmonic of the driving
laser frequency, at isolated values of the amplitude.Comment: RevTeX, 10 pages (4 figures available on request), Preprint
UCSBTH-93-2
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