1,832 research outputs found
Effect of electron exchange on atomic ionization in a strong electric field
Hartree-Fock atom in a strong electric static field is considered. It is
demonstrated that exchange between outer and inner electrons, taken into
account by the so-called Fock term affects strongly the long-range behavior of
the inner electron wave function. As a result, it dramatically increases its
probability to be ionized. A simple model is analyzed demonstrating that the
decay probability, compared to the case of a local (Hartree) atomic potential,
increases by many orders of magnitude. As a result of such increase, the ratio
of inner to outer electrons ionization probability became not too small. It is
essential that the effect of exchange upon probability of inner electron
ionization by strong electric field is proportional to the square of the number
of outer electrons. It signals that in clusters the inner electron ionization
by strong field, the very fact of which is manifested by e.g. high energy
quanta emission, has to be essentially increased as compared to this process in
gaseous atomic objects.Comment: 7 pages, 1 figur
Social and cultural origins of motivations to volunteer a comparison of university students in six countries
Although participation in volunteering and motivations to volunteer (MTV) have received substantial attention on the national level, particularly in the US, few studies have compared and explained these issues across cultural and political contexts. This study compares how two theoretical perspectives, social origins theory and signalling theory, explain variations in MTV across different countries. The study analyses responses from a sample of 5794 students from six countries representing distinct institutional contexts. The findings provide strong support for signalling theory but less so for social origins theory. The article concludes that volunteering is a personal decision and thus is influenced more at the individual level but is also impacted to some degree by macro-level societal forces
Self-Sensing Surface Plasmon Resonance for the Detection of Metallic Nanoparticles
Surface plasmon resonance (SPR) is an established technique for label free sensing of bio-molecular species, including time-dependent reaction analysis. Unlike previous research by other workers, who have used gold or silver nanoparticles to enhance sensitivity by inducing LSPR, this study involves the theoretical development of a Localised SPR (LSPR) system where a glass prism is considered with multilayer films to enable the detection of metallic nanoparticles. Silver nanoparticles with a volume concentration 0.25 % can be clearly detected from both amplitude and phase, according to the results of these simulations. The model presented is rigorous in that it accounts for the effect of the Cr or Ti adhesion layers together with a graphene layer at the metal-sensing interface. This enables the direct detection of the presence of nanoparticles from their plasmonic amplitude and phase (self-sensing). Our model also demonstrates that the sensitivity of the sensors can be significantly improved with the introduction of graphene layers
Study of a class of non-polynomial oscillator potentials
We develop a variational method to obtain accurate bounds for the
eigenenergies of H = -Delta + V in arbitrary dimensions N>1, where V(r) is the
nonpolynomial oscillator potential V(r) = r^2 + lambda r^2/(1+gr^2), lambda in
(-infinity,\infinity), g>0. The variational bounds are compared with results
previously obtained in the literature. An infinite set of exact solutions is
also obtained and used as a source of comparison eigenvalues.Comment: 16 page
Commute replacement and commute displacement the rise of part-day home working
Working by telecommunication has been the subject of research attention in transportation studies for many years. Particular consideration has been given to occasional working from home (home working) by (full-time, paid) employees who represent a tangible removal of commute trips on days that people work from home. However, little recognition or attention has been given to the fact that home working not only may be undertaken for part of a week but also may be undertaken for parts of given days. This paper focuses particularly on part-day home working. It defines and uses the term "varied spatiotemporal (VST) working" to describe working days in which at least 30 min of continuous working takes place at home accompanied by work taking place at the workplace. Notably, such home working does not remove the commute trips but can temporally displace one or both of them. The research reported in this paper builds on preceding survey work that had established that the number of people who practice VST working and the number of VST days worked appear to be about double those for full-day home working (which has typically been the focus of research attention). The results presented in this paper are based on 25 in-depth interviews with individuals who practice VST working. The aim of the research was to examine more closely and to understand the nature of VST working and the motivations and constraints for its practice and to consider its potential contribution as a transportation demand management measure
PT symmetric models in more dimensions and solvable square-well versions of their angular Schroedinger equations
For any central potential V in D dimensions, the angular Schroedinger
equation remains the same and defines the so called hyperspherical harmonics.
For non-central models, the situation is more complicated. We contemplate two
examples in the plane: (1) the partial differential Calogero's three-body model
(without centre of mass and with an impenetrable core in the two-body
interaction), and (2) the Smorodinsky-Winternitz' superintegrable harmonic
oscillator (with one or two impenetrable barriers). These examples are solvable
due to the presence of the barriers. We contemplate a small complex shift of
the angle. This creates a problem: the barriers become "translucent" and the
angular potentials cease to be solvable, having the sextuple-well form for
Calogero model and the quadruple or double well form otherwise. We mimic the
effect of these potentials on the spectrum by the multiple, purely imaginary
square wells and tabulate and discuss the result in the first nontrivial
double-well case.Comment: 21 pages, 5 figures (see version 1), amendment (a single comment
added on p. 7
Great Expectations: Voluntary Sports Clubs and Their Role in Delivering National Policy for English Sport
âThe original publication is available at www.springerlink.comâ. Copyright International Society for Third-Sector Research and The Johns Hopkins University. DOI: 10.1007/s11266-009-9095-yVoluntary sports clubs (VSCs) account for about a quarter of all volunteering in England. The volunteers work in a mutual aid, self-production, self-consumption system whose main purpose is identifying and nurturing high-level performers. But the new HMG/Sport England strategies leading to London 2012 expects volunteers to make a major contribution to sustaining and extending participation. The study utilized six focus group sessions with a total of 36 officials and members of 36 clubs across the six counties of Eastern England to assess whether and to what extent government policy objectives can be delivered through the voluntary sector. The study focused on the perceptions and attitudes of club members about being expected to serve public policy and the current pressures they and their clubs face. The results lead the authors to question the appropriateness, sensitivity, and feasibility of current sport policy, particularly the emphasis on VSCs as policy implementers.Peer reviewe
Relativistic supersymmetric quantum mechanics based on Klein-Gordon equation
Witten's non-relativistic formalism of supersymmetric quantum mechanics was
based on a factorization and partnership between Schroedinger equations. We
show how it accommodates a transition to the partnership between relativistic
Klein-Gordon equations. In such a class of models the requirement of
supersymmetry is shown to lead to a certain "exceptional-point" instability of
ground states.Comment: 20 page
Models and metaphors: complexity theory and through-life management in the built environment
Complexity thinking may have both modelling and metaphorical applications in the through-life management of the built environment. These two distinct approaches are examined and compared. In the first instance, some of the sources of complexity in the design, construction and maintenance of the built environment are identified. The metaphorical use of complexity in management thinking and its application in the built environment are briefly examined. This is followed by an exploration of modelling techniques relevant to built environment concerns. Non-linear and complex mathematical techniques such as fuzzy logic, cellular automata and attractors, may be applicable to their analysis. Existing software tools are identified and examples of successful built environment applications of complexity modelling are given. Some issues that arise include the definition of phenomena in a mathematically usable way, the functionality of available software and the possibility of going beyond representational modelling. Further questions arising from the application of complexity thinking are discussed, including the possibilities for confusion that arise from the use of metaphor. The metaphor of a 'commentary machine' is suggested as a possible way forward and it is suggested that an appropriate linguistic analysis can in certain situations reduce perceived complexity
Dynamics of Coronal Bright Points as seen by Sun Watcher using Active Pixel System detector and Image Processing (SWAP), Atmospheric Imaging Assembly AIA), and Helioseismic and Magnetic Imager (HMI)
The \textit{Sun Watcher using Active Pixel system detector and Image
Processing}(SWAP) on board the \textit{PRoject for OnBoard Autonomy\todash 2}
(PROBA\todash 2) spacecraft provides images of the solar corona in EUV channel
centered at 174 \AA. These data, together with \textit{Atmospheric Imaging
Assembly} (AIA) and the \textit{Helioseismic and Magnetic Imager} (HMI) on
board \textit{Solar Dynamics Observatory} (SDO), are used to study the dynamics
of coronal bright points. The evolution of the magnetic polarities and
associated changes in morphology are studied using magnetograms and
multi-wavelength imaging. The morphology of the bright points seen in
low-resolution SWAP images and high-resolution AIA images show different
structures, whereas the intensity variations with time show similar trends in
both SWAP 174 and AIA 171 channels. We observe that bright points are seen in
EUV channels corresponding to a magnetic-flux of the order of Mx. We
find that there exists a good correlation between total emission from the
bright point in several UV\todash EUV channels and total unsigned photospheric
magnetic flux above certain thresholds. The bright points also show periodic
brightenings and we have attempted to find the oscillation periods in bright
points and their connection to magnetic flux changes. The observed periods are
generally long (10\todash 25 minutes) and there is an indication that the
intensity oscillations may be generated by repeated magnetic reconnection
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