Optimized Effective Potentials in Finite Basis Sets

The finite basis optimized effective potential (OEP) method within density functional theory is examined as an ill-posed problem. It is shown that the generation of nonphysical potentials is a controllable manifestation of the use of unbalanced, and thus unsuitable, basis sets. A modified functional incorporating a regularizing smoothness measure of the OEP is introduced. This provides a condition on balanced basis sets for the potential, as well as a method to determine the most appropriate OEP potential and energy from calculations performed with any finite basis set.Comment: 23 pages, 28 figure

Validation of electron density profiles derived from oblique ionograms over the United Kingdom

Inversion algorithms are available to derive the vertical electron density profile at the midpoint of an oblique sounder path. The techniques open up the possibility of monitoring the ionosphere at otherwise inaccessible locations, such as over sea or inhospitable terrain. A new method of monitoring the ionosphere based on radio tomography can be used to create two-dimensional images of electron density. The results in this paper compare midpoint profiles derived from oblique ionograms with corresponding profiles obtained from tomographic images of electron density and from a vertical ionospheric sounder. The comparisons illustrate the oblique sounder inversion technique and its inherent limitations. The results provide useful information on the complementary nature of the separate ionospheric measurement techniques and have implications for the use of these measurements as inputs to real-time ionospheric models

Redefining smoking relapse as recovered social identity – secondary qualitative analysis of relapse narratives

Although many people in the general population manage to quit smoking, relapse is common. Theory underpinning the determinants of smoking relapse is under-developed. This article aims to specify theoretical insight into the process of relapse to smoking, to underpin effective intervention development. Secondary qualitative analysis of extended narratives of smoking relapse (n=23) were inductively coded within our conceptual framework of a socially situated narrative theoretical approach to identity. Smoking relapse is conceptualised as a situated rational response to a ‘disruption’ in individual narrative identity formation, and an attempt to recover a lost social identity. Emotional reactions to relapse, such as pleasure, but also guilt and shame, support this assertion by demonstrating the ambivalence of re-engaging in a behaviour that is situated and rational in terms of individual identity formation, yet ostracised and stigmatised by wider culture

Using Voice Recognition Software to improve communicative writing and social participation in an individual with severe acquired dysgraphia: an experimental single case therapy study

Background Two previous single-case studies have reported that voice recognition software (VRS) can be a powerful tool for circumventing impaired writing in aphasia (Bruce et al, 2003; Estes & Bloom, 2011). However, these studies report mixed results regarding transfer of skills to functional tasks, such as emailing. Method A single-case therapy study was conducted with “Stephen”, a 63 -year old man with fluent aphasia and severe acquired dysgraphia and dyslexia limiting his social participation and ability to return to work. Treatment consisted of 16 one-hour sessions. Stephen was trained to use Dragon NaturallySpeakingRTM VRS to assist writing and Read+WriteGoldRTM text-to-speech software to assist reading, and to develop computer skills required to use email. Outcome measures evaluated writing efficiency and communicative effectiveness, the functional impact of the intervention, and changes in participation. Results Training produced significant gains in the efficiency and communicative effectiveness of Stephen’s writing, despite his underlying writing impairment remaining unchanged. Gains generalised to everyday functional communication, leading to increased social participation with Stephen undertaking a wider range of social activities and increasing his social network following treatment. Gains were maintained at follow-up assessment. Discussion Results indicate that a relatively short training period with assistive technologies achieved extensive generalisation to independent, functional communicative writing. Indeed, for this case, VRS training may have exceeded the degree of improvement in functional text writing that could have been achieved through impairment therapy, since gains were not limited to treated vocabulary. Some challenges were encountered in training Stephen to use VRS but, through adaptations to the training process, were largely overcome. Importantly, regaining independent writing skills resulted in profound and life-changing improvements to social participation. This may have resulted in Stephen reconnecting with important aspects of his pre-stroke identity, and improving his self-esteem. Conclusion This case adds to a small evidence base indicating that training in the use of VRS, in combination with text-to-speech software, may be an effective way to address writing impairments in chronic aphasia for individuals with relatively well-preserved spoken output. Not only can these technologies improve the efficiency and communicative effectiveness of writing, they can also lead to significant gains in functional communication and social participation. Further research is needed trialing this approach with a larger group of people with aphasia

COMT Val158Met Polymorphism, Executive Dysfunction, and Sexual Risk Behavior in the Context of HIV Infection and Methamphetamine Dependence

Catechol-O-methyltransferease (COMT) metabolizes prefrontal cortex dopamine (DA), a neurotransmitter involved in executive behavior; the Val158Met genotype has been linked to executive dysfunction, which might increase sexual risk behaviors favoring HIV transmission. Main and interaction effects of COMT genotype and executive functioning on sexual risk behavior were examined. 192 sexually active nonmonogamous men completed a sexual behavior questionnaire, executive functioning tests, and were genotyped using blood-derived DNA. Main effects for executive dysfunction but not COMT on number of sexual partners were observed. A COMT x executive dysfunction interaction was found for number of sexual partners and insertive anal sex, significant for carriers of the Met/Met and to a lesser extent Val/Met genotypes but not Val/Val carriers. In the context of HIV and methamphetamine dependence, dopaminergic overactivity in prefrontal cortex conferred by the Met/Met genotype appears to result in a liability for executive dysfunction and potentially associated risky sexual behavior

Distribution of time-constants for tunneling through a 1D Disordered Chain

The dynamics of electronic tunneling through a disordered 1D chain of finite length is considered. We calculate distributions of the transmission coefficient T, Wigner delay time and, $\tau_\phi$ and the transport time, $\tau_t=T\tau_\phi$. The central bodies of these distributions have a power-law form, what can be understood in terms of the resonant tunneling through localised states.Comment: 5 pages, 3 figures, submitted to PR

Traveling wave solutions in the Burridge-Knopoff model

The slider-block Burridge-Knopoff model with the Coulomb friction law is studied as an excitable medium. It is shown that in the continuum limit the system admits solutions in the form of the self-sustained shock waves traveling with constant speed which depends only on the amount of the accumulated stress in front of the wave. For a wide class of initial conditions the behavior of the system is determined by these shock waves and the dynamics of the system can be expressed in terms of their motion. The solutions in the form of the periodic wave trains and sources of counter-propagating waves are analyzed. It is argued that depending on the initial conditions the system will either tend to synchronize or exhibit chaotic spatiotemporal behavior.Comment: 12 pages (ReVTeX), 7 figures (Postscript) to be published in Phys. Rev.

Dynamic effect of phase conjugation on wave localization

We investigate what would happen to the time dependence of a pulse reflected by a disordered single-mode waveguide, if it is closed at one end not by an ordinary mirror but by a phase-conjugating mirror. We find that the waveguide acts like a virtual cavity with resonance frequency equal to the working frequency omega_0 of the phase-conjugating mirror. The decay in time of the average power spectrum of the reflected pulse is delayed for frequencies near omega_0. In the presence of localization the resonance width is tau_s^{-1}exp(-L/l), with L the length of the waveguide, l the mean free path, and tau_s the scattering time. Inside this frequency range the decay of the average power spectrum is delayed up to times t simeq tau_s exp(L/l).Comment: 10 pages including 2 figure

Massive Stars: Their Environment and Formation

Cloud environment is thought to play a critical role in determining the mechanism of formation of massive stars. In this contribution we review the physical characteristics of the environment around recently formed massive stars. Particular emphasis is given to recent high angular resolution observations which have improved our knowledge of the physical conditions and kinematics of compact regions of ionized gas and of dense and hot molecular cores associated with luminous O and B stars. We will show that this large body of data, gathered during the last decade, has allowed significant progress in the understanding of the physical processes that take place during the formation and early evolution of massive stars.Comment: Pub. Astron. Soc. of Pacific (Invited Review), 95 pages (Latex), 5 pages (tables, Latex), 11 postscript or gif figure