Energy-momentum conservation in pre-metric electrodynamics with magnetic charges

A necessary and sufficient condition for energy-momentum conservation is proved within a topological, pre-metric approach to classical electrodynamics including magnetic as well as electric charges. The extended Lorentz force, consisting of mutual actions by F=(E, B) on the electric current and G=(H, D) on the magnetic current, can be derived from an energy-momentum "potential" if and only if the constitutive relation G=G(F) satisfies a certain vanishing condition. The electric-magnetic reciprocity introduced by Hehl and Obukhov is seen to define a complex structure on the tensor product of 2-form pairs (F,G) which is independent of but consistent with the Hodge star operator defined by any Lorentzian metric. Contrary to a recent claim in the literature, it does not define a complex structure on the space of 2-forms itself.Comment: 8 pages, 1 fugur

Infinite families of superintegrable systems separable in subgroup coordinates

A method is presented that makes it possible to embed a subgroup separable superintegrable system into an infinite family of systems that are integrable and exactly-solvable. It is shown that in two dimensional Euclidean or pseudo-Euclidean spaces the method also preserves superintegrability. Two infinite families of classical and quantum superintegrable systems are obtained in two-dimensional pseudo-Euclidean space whose classical trajectories and quantum eigenfunctions are investigated. In particular, the wave-functions are expressed in terms of Laguerre and generalized Bessel polynomials.Comment: 19 pages, 6 figure

Measurement Properties of the Full and Brief Version of the Work Rehabilitation Questionnaire in Persons with Physical Disabilities

Purpose The Work Rehabilitation Questionnaire (WORQ) is a self-report vocational rehabilitation assessment. A comprehensive (WORQ-FULL) and a brief version (WORQ-BRIEF) are available. The purpose of this study was to investigate measurement properties of both versions in persons with physical disabilities. Methods Cross sectional and test-retest design. Adults with physical disabilities in vocational rehabilitation were included. Internal consistency (Cronbach's alpha), test-retest reliability (intra-class correlation; ICC), agreement between sessions (Bland-Altman Plots), criterion validity (ICC and agreement with Bland-Altman Plots between WORQ-FULL and WORQ-BRIEF) and convergent validity with the Work Ability Index -Single item (WAS) and the EuroQOL 5D-5L were analyzed. Results Out of the 91 individuals who agreed to participate, 74 (81%) returned questionnaire T1 and 49 (54%) participants returned questionnaire T2 within the maximum time interval (= 27 days). At T2, 28 (57%) participants reported no medical changes compared to T1. Median age was 49 (IQR 40-60), 57% were male, 47% had experienced a stroke and 27% a spinal cord injury (n = 49). Internal consistency was good: 0.95/0.95/0.94 for the WORQ-FULL and 0.88/0.89/0.85 for the WORQ-BRIEF (n = 74/n = 48/n = 28, respectively). Test-retest reliabilitywas good: ICC = 0.86/0.85 for the WORQ-FULL and ICC = 0.87/0.86 for the WORQ-BRIEF (n = 49/ n = 28). Bland Altman plots suggested a higher score at T1. As for criterion validity of the WORQ-FULL versus the WORQ-BRIEF, ICC was good (ICC = 0.84; n = 74), however Bland Altman plots indicated potential bias. Correlations with the WAS/EuroQOL 5D-5L were variable: r = -0.24/r = -0.57 (WORQ-FULL) and r = -0.28/-0.65 (WORQ-BRIEF). Conclusions The WORQ showed good internal consistency and test-retest reliability. Agreement demonstrated large score differences are needed to indicate change beyond random chance at individual level, whereas small changes are sufficient at group level. Criterion validity of the WORQ-FULL versus the WORQ-BRIEF was supported, however, agreement demonstrated moderate to large score differences are needed to indicate change beyond random chance at individual level, whereas small changes are sufficient at group level. This indicates the WORQ-FULL and WORQ-BRIEF are better not used interchangeably. Correlation analyses provided better insight in the validity of the WORQ. Convergent validity was supported for the WORQ-BRIEF with the EuroQoL 5D-5L (r = -0.65)

Genome reconstructions indicate the partitioning of ecological functions inside a phytoplankton bloom in the Amundsen Sea, Antarctica

© The Author(s), 2015. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Frontiers in Microbiology 6 (2015): 1090, doi:10.3389/fmicb.2015.01090.Antarctica polynyas support intense phytoplankton blooms, impacting their environment by a substantial depletion of inorganic carbon and nutrients. These blooms are dominated by the colony-forming haptophyte Phaeocystis antarctica and they are accompanied by a distinct bacterial population. Yet, the ecological role these bacteria may play in P. antarctica blooms awaits elucidation of their functional gene pool and of the geochemical activities they support. Here, we report on a metagenome (~160 million reads) analysis of the microbial community associated with a P. antarctica bloom event in the Amundsen Sea polynya (West Antarctica). Genomes of the most abundant Bacteroidetes and Proteobacteria populations have been reconstructed and a network analysis indicates a strong functional partitioning of these bacterial taxa. Three of them (SAR92, and members of the Oceanospirillaceae and Cryomorphaceae) are found in close association with P. antarctica colonies. Distinct features of their carbohydrate, nitrogen, sulfur and iron metabolisms may serve to support mutualistic relationships with P. antarctica. The SAR92 genome indicates a specialization in the degradation of fatty acids and dimethylsulfoniopropionate (compounds released by P. antarctica) into dimethyl sulfide, an aerosol precursor. The Oceanospirillaceae genome carries genes that may enhance algal physiology (cobalamin synthesis). Finally, the Cryomorphaceae genome is enriched in genes that function in cell or colony invasion. A novel pico-eukaryote, Micromonas related genome (19.6 Mb, ~94% completion) was also recovered. It contains the gene for an anti-freeze protein, which is lacking in Micromonas at lower latitudes. These draft genomes are representative for abundant microbial taxa across the Southern Ocean surface.This work was performed with financial support from NSF Antarctic Sciences awards ANT-1142095 to AP

Crohn's disease activity index and Vienna classification - Is it worthwhile to calculate before surgery?

Background: Crohn's disease (CD) patients with increased disease activity may reveal an increased risk for perioperative complications. The `Crohn's disease activity index' (CDAI) and the `Vienna classification' (VC) were developed for standardized disease activity estimations. The significance of these scores to predict extent, type and early outcome of surgery in CD patients was analyzed. Methods: In 179 surgically treated CD patients, the CDAI and VC were assessed from a prospective database. Relations of the scores with CD risk factors, type, number, location and complications of surgery were analyzed. Results: VC behavior and location subtypes were associated with distinct types of surgery (i.e. `strictureplasty' in `stricturing disease', `colon surgery' in `colon involvement'), but not with surgery type and extent or outcome. Surgery extent (i.e. with 5 vs. 3 `surgical sites' 425 +/- 25 vs. 223.3 +/- 25) and complications (357.1 +/- 36.9 (with) vs. 244.4 +/- 13 (without)) were associated with elevated CDAI levels; however, nicotine abuse remained the only significant risk factor for perioperative complications after multiple logistic regression. Conclusion: The significance of VC or CDAI for predicting the extent of surgery or complications is limited. None of the tested variables except preoperative nicotine abuse influenced the likelihood for perioperative complications. Copyright (c) 2006 S. Karger AG, Base

Content validity of the Work Rehabilitation Questionnaire (WORQ) for persons with spinal cord injury:A mixed methods study

STUDY DESIGN: Mixed methods. OBJECTIVES: The aim of our study was to investigate the content validity of the Work Rehabilitation Questionnaire (WORQ) for use in persons with post-acute and chronic spinal cord injury (SCI). SETTING: A university-based Rehabilitation Center in The Netherlands. METHODS: Contents of the WORQ, brief ICF core sets for SCI for post-acute care and for chronic situation were compared with semi-guided interviews with persons with SCI and controlled for relevance by SCI rehabilitation professionals in two group meetings. RESULTS: Fourteen interviews with persons with SCI were performed. Two group meetings with 8 and 9 SCI rehabilitation professionals were held. Thirty seven of the 46 ICF categories (80%) of the WORQ were confirmed by both sources: mentioned in interviews with persons with SCI and considered important by the SCI professionals. The remaining 9 categories (20%) were confirmed by either the persons with SCI or the SCI professionals. Fourteen ICF categories that are part of the brief ICF core set for SCI for acute care and/or chronic situation, however are not part of the WORQ, have revealed importance by persons with SCI and SCI professionals. CONCLUSION: Our study confirms that most categories of the WORQ are important to consider for VR in persons with SCI, however, there are ICF categories that are absent in the WORQ and deemed relevant for use in VR in persons with SCI. Consequently, the content validity of the WORQ without additional items is insufficient for persons with SCI

On possible skewon effects on light propagation

We start from a local and linear spacetime relation between the electromagnetic excitation and the field strength. Then we study the generally covariant Fresnel surfaces for light rays and light waves. The metric and the connection of spacetime are left unspecified. Accordingly, our framework is ideally suited for a search of possible violations of the Lorentz symmetry in the photon sector of the extended standard model. We discuss how the skewon part of the constitutive tensor, if suitably parametrized, influences the Fresnel surfaces and disturbs the light cones of vacuum electrodynamics. Conditions are specified that yield the reduction of the original quartic Fresnel surface to the double light cone structure (birefringence) and to the single light cone. Qualitatively, the effects of the real skewon field can be compared to those in absorbing material media. In contrast, the imaginary skewon field can be interpreted in terms of non-absorbing media with natural optical activity and Faraday effects. The astrophysical data on gamma-ray bursts are used for deriving an upper limit for the magnitude of the skewon field.Comment: Revtex, 29 pages, 10 figures, references added, text as in the published versio

Direct approach to the problem of strong local minima in Calculus of Variations

The paper introduces a general strategy for identifying strong local minimizers of variational functionals. It is based on the idea that any variation of the integral functional can be evaluated directly in terms of the appropriate parameterized measures. We demonstrate our approach on a problem of W^{1,infinity} weak-* local minima--a slight weakening of the classical notion of strong local minima. We obtain the first quasiconvexity-based set of sufficient conditions for W^{1,infinity} weak-* local minima.Comment: 26 pages, no figure