22,112 research outputs found
Influence of Lorentz- and CPT-violating terms on the Dirac equation
The influence of Lorentz- and CPT-violating terms (in "vector" and "axial
vector" couplings) on the Dirac equation is explicitly analyzed: plane wave
solutions, dispersion relations and eigenenergies are explicitly obtained. The
non-relativistic limit is worked out and the Lorentz-violating Hamiltonian
identified in both cases, in full agreement with the results already
established in the literature. Finally, the physical implications of this
Hamiltonian on the spectrum of hydrogen are evaluated both in the absence and
presence of a magnetic external field. It is observed that the fixed
background, when considered in a vector coupling, yields no qualitative
modification in the hydrogen spectrum, whereas it does provide an effective
Zeeman-like splitting of the spectral lines whenever coupled in the axial
vector form. It is also argued that the presence of an external fixed field
does not imply new modifications on the spectrum.Comment: 13 pages, no figures, revtex4 styl
IBM: parameter symmetry, hidden symmetries and transformations of boson operators
A symmetry of the parameter space of interacting boson models IBM-1 and IBM-2
is studied. The symmetry is associated with linear canonical transformations of
boson operators, or, equivalently, with the existence of different realizations
of the symmetry algebras of the models. The relevance of the parameter symmetry
to physical observables is discussed.Comment: LATEX, 11 pages including 1 eps figure and 1 table prepared as an eps
figure; a talk given by A. M. Siirokov at XXII Symposium on Nuclear Physics,
Oaxtepec, Morelos, M\'exico, 5--8 January, 1999; to be published in Revista
Mex. Fi
Evolution of YidC/Oxa1/Alb3 insertases: three independent gene duplications followed by functional specialization in bacteria, mitochondria and chloroplasts
Members of the YidC/Oxa1/Alb3 protein family facilitate the insertion, folding and assembly of proteins of the inner membranes of bacteria and mitochondria and the thylakoid membrane of plastids. All homologs share a conserved hydrophobic core region comprising five transmembrane domains. On the basis of phylogenetic analyses, six subgroups of the family can be distinguished which presumably arose from three independent gene duplications followed by functional specialization. During evolution of bacteria, mitochondria and chloroplasts, subgroup-specific regions were added to the core domain to facilitate the association with ribosomes or other components contributing to the substrate spectrum of YidC/Oxa1/Alb3 proteins
Just for To-Night / music by Frank O. French; words by Frank O. French
Cover: photo of Jos. E. Blamphin the phenomenal tenor of Al. G. Fields Minstrels, Botanical Illustration; Publisher: M. Witmark and Sons (New York)https://egrove.olemiss.edu/sharris_b/1033/thumbnail.jp
Dual Band Electrodes in Generator-Collector Mode: Simultaneous Measurement of Two Species
A computational model for the simulation of a double band collector-generator
experiment is applied to the situation where two electrochemical reactions
occur concurrently. It is shown that chronoamperometric measurements can be
used to take advantage of differences in diffusion coefficients to measure the
concentrations of both electroactive species simultaneously, by measuring the
time at which the collection efficiency reaches a specific value. The
separation of the electrodes is shown to not affect the sensitivity of the
method (in terms of percentage changes in the measured time to reach the
specified collection efficiency), but wider gaps can provide a greater range of
(larger) absolute values of this characteristic time. It is also shown that
measuring the time taken to reach smaller collection efficiencies can allow for
the detection of smaller amounts of whichever species diffuses faster. The case
of a system containing both ascorbic acid and opamine in water is used to
exemplify the method, and it is shown that mole fractions of ascorbic acid
between 0.055 and 0.96 can, in principle, be accurately measured.Comment: 34 pages, 8 figure
Experiences of living with chronic back pain: The physical disabilities
Purpose. Back-related functional limitations are largely assessed using lists of activities, each scored on a yes/no basis and the scores then summed. This provides little information about how chronic back pain (CBP) patients live with their condition. This study describes the consequences of living day-to-day with CBP and documents the 'insider' accounts of its impact on daily life.
Method. Unstructured interviews, using the 'Framework' approach with topic guide, were recorded and transcribed verbatim. Subjects were sampled for age, sex, ethnicity and occupation from new referrals with back pain to a rheumatology outpatient clinic. Eleven subjects (5 male, 6 female) were interviewed either in English (n = 9) or their preferred language (n = 2). Interviews were read in-depth twice to identify the topics. Data were extracted in phrases and sentences using thematic content analysis.
Results. Four themes emerged: sleep/rest, mobility, independence and leisure. All subjects reported issues about sleep and rest, nine about mobility, seven about independence and six on leisure. Most descriptions concerned loss and limitation in daily life. Strategies for coping with sleep disruption and physical limitations were described.
Conclusions. Subjects provided graphic 'in-depth' descriptions of experiences living with CBP every day; expressed regret at the loss of capabilities and distress at the functional consequences of those losses. Facilitating 'adjustment' to 'loss' may be more helpful than inferring the potential for a life free of pain as a result of therapeutic endeavours
The pain experiences of powered wheelchair users
Copyright © 2012 Informa UK, Ltd. This is the author's accepted manuscript. The final published article is available from the link below.Purpose: To explore the experience of pain and discomfort in users of electric-powered indoor/outdoor wheelchairs (EPIOCs) provided by a National Health Service. Methods: EPIOC users receiving their chair between February and November 2002 (N=74) were invited to participate in a telephone questionnaire/interview and 64 (aged 1081 years) agreed. Both specific and open-ended questions examined the presence of pain/discomfort, its severity, minimizing and aggravating factors, particularly in relation to the EPIOC and its use. Results: Most EPIOC users described experiences of pain with 17% reporting severe pain. Over half felt their pain was influenced by the wheelchair and few (25%) considered their chair eased their symptoms. The most common strategy for pain relief was taking medication. Other self-help strategies included changing position, exercise and complementary therapies. Respondents emphasized the provision of backrests, armrests, footrests and cushions which might alleviate or exacerbate pain, highlighting the importance of appropriate assessment for this high dependency group. Conclusions: Users related pain to their underlying medical condition, their wheelchair or a combination of the two. User feedback is essential to ensure that the EPIOC meets health needs with minimal pain. This becomes more important as the health condition of users changes over time
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