Lower bound for energies of harmonic tangent unit-vector fields on convex polyhedra

We derive a lower bound for energies of harmonic maps of convex polyhedra in $\R^3$ to the unit sphere $S^2,$ with tangent boundary conditions on the faces. We also establish that $C^\infty$ maps, satisfying tangent boundary conditions, are dense with respect to the Sobolev norm, in the space of continuous tangent maps of finite energy.Comment: Acknowledgment added, typos removed, minor correction

Strategies for the examination of Alzheimer's disease amyloid precursor protein isoforms.

The principal aim of this research project has been the utilisation of various proteomic techniques in the investigation of the Alzheimer's disease amyloid precursor protein (APP) isoforms, namely APP[695], APP[751] and APP[770]. One of the most noticeable pathological characteristics of Alzheimer's disease is the presence of neuritic plaques in brain tissue. The chief protein constituent of neuritic plaques is the beta amyloid peptide. This peptide is proteolytically cleaved from APP, as such the interest in APP isoforms is great and a rapid detection method for the presence of each isoform would be a huge advantage to the research effort with regards to the determination and concentration in both diseased and non-diseased states. Two-dimensional gel electrophoresis and peptide mass fingerprinting are two of the most important techniques in the proteomics arena and both are investigated fully in this work. Retinoic acid induced Ntera 2 cells, derived from a human teratocarcinoma cell line, were the in vitro source of APP. Initial isolation of APP was performed by immunoprecipitation, using a monoclonal antibody raised to amino acids 1-17 of the beta-amyloid peptide sequence, which is present in all three alpha secretase cleaved isoforms of interest. The next step was to separate whole APP into its isoform components by two-dimensional gel electrophoresis. The resulting protein spots were then subjected to peptide mass fingerprinting employing the different digest reagents, trypsin, endoproteinase Asp-N and formic acid. Initial distinction between the APP isoforms could be seen upon examination of theoretical in silica digests using the various digest reagents mentioned. The in silica digests revealed peptides unique to each isoform that in theory could be used as indicators of isoform presence

Electronic transport through ballistic chaotic cavities: reflection symmetry, direct processes, and symmetry breaking

We extend previous studies on transport through ballistic chaotic cavities with spatial left-right (LR) reflection symmetry to include the presence of direct processes. We first analyze fully LR-symmetric systems in the presence of direct processes and compare the distribution w(T) of the transmission coefficient T with that for an asymmetric cavity with the same "optical" S matrix. We then study the problem of "external mixing" of the symmetry caused by an asymmetric coupling of the cavity to the outside. We first consider the case where symmetry breaking arises because two symmetrically positioned waveguides are coupled to the cavity by means of asymmetric tunnel barriers. Although this system is asymmetric with respect to the LR operation, it has a striking memory of the symmetry of the cavity it was constructed from. Secondly, we break LR symmetry in the absence of direct proceses by asymmetrically positioning the two waveguides and compare the results with those for the completely asymmetric case.Comment: 15 pages, 8 Postscript figures, submitted to Phys. Rev.

Effects of sea temperature and stratification changes on seabird breeding success

As apex predators in marine ecosystems, seabirds may primarily experience climate change impacts indirectly, via changes to their food webs. Observed seabird population declines have been linked to climate-driven oceanographic and food web changes. However, relationships have often been derived from relatively few colonies and consider only sea surface temperature (SST), so important drivers, and spatial variation in drivers, could remain undetected. Further, explicit climate change projections have rarely been made, so longer-term risks remain unclear. Here, we use tracking data to estimate foraging areas for eleven black-legged kittiwake (Rissa tridactyla) colonies in the UK and Ireland, thus reducing reliance on single colonies and allowing calculation of colony-specific oceanographic conditions. We use mixed models to consider how SST, the potential energy anomaly (indicating density stratification strength) and the timing of seasonal stratification influence kittiwake productivity. Across all colonies, higher breeding success was associated with weaker stratification before breeding and lower SSTs during the breeding season. Eight colonies with sufficient data were modelled individually: higher productivity was associated with later stratification at three colonies, weaker stratification at two, and lower SSTs at one, whilst two colonies showed no significant relationships. Hence, key drivers of productivity varied among colonies. Climate change projections, made using fitted models, indicated that breeding success could decline by 21 – 43% between 1961-90 and 2070-99. Climate change therefore poses a longer-term threat to kittiwakes, but as this will be mediated via availability of key prey species, other marine apex predators could also face similar threats

Dressing the nucleon in a dispersion approach

We present a model for dressing the nucleon propagator and vertices. In the model the use of a K-matrix approach (unitarity) and dispersion relations (analyticity) are combined. The principal application of the model lies in pion-nucleon scattering where we discuss effects of the dressing on the phase shifts.Comment: 17 pages, using REVTeX, 6 figure

Nonparametric Information Geometry

The differential-geometric structure of the set of positive densities on a given measure space has raised the interest of many mathematicians after the discovery by C.R. Rao of the geometric meaning of the Fisher information. Most of the research is focused on parametric statistical models. In series of papers by author and coworkers a particular version of the nonparametric case has been discussed. It consists of a minimalistic structure modeled according the theory of exponential families: given a reference density other densities are represented by the centered log likelihood which is an element of an Orlicz space. This mappings give a system of charts of a Banach manifold. It has been observed that, while the construction is natural, the practical applicability is limited by the technical difficulty to deal with such a class of Banach spaces. It has been suggested recently to replace the exponential function with other functions with similar behavior but polynomial growth at infinity in order to obtain more tractable Banach spaces, e.g. Hilbert spaces. We give first a review of our theory with special emphasis on the specific issues of the infinite dimensional setting. In a second part we discuss two specific topics, differential equations and the metric connection. The position of this line of research with respect to other approaches is briefly discussed.Comment: Submitted for publication in the Proceedings od GSI2013 Aug 28-30 2013 Pari

HI in the Outskirts of Nearby Galaxies

The HI in disk galaxies frequently extends beyond the optical image, and can trace the dark matter there. I briefly highlight the history of high spatial resolution HI imaging, the contribution it made to the dark matter problem, and the current tension between several dynamical methods to break the disk-halo degeneracy. I then turn to the flaring problem, which could in principle probe the shape of the dark halo. Instead, however, a lot of attention is now devoted to understanding the role of gas accretion via galactic fountains. The current $\rm \Lambda$ cold dark matter theory has problems on galactic scales, such as the core-cusp problem, which can be addressed with HI observations of dwarf galaxies. For a similar range in rotation velocities, galaxies of type Sd have thin disks, while those of type Im are much thicker. After a few comments on modified Newtonian dynamics and on irregular galaxies, I close with statistics on the HI extent of galaxies.Comment: 38 pages, 17 figures, invited review, book chapter in "Outskirts of Galaxies", Eds. J. H. Knapen, J. C. Lee and A. Gil de Paz, Astrophysics and Space Science Library, Springer, in pres

Quantum mechanics: Myths and facts

A common understanding of quantum mechanics (QM) among students and practical users is often plagued by a number of "myths", that is, widely accepted claims on which there is not really a general consensus among experts in foundations of QM. These myths include wave-particle duality, time-energy uncertainty relation, fundamental randomness, the absence of measurement-independent reality, locality of QM, nonlocality of QM, the existence of well-defined relativistic QM, the claims that quantum field theory (QFT) solves the problems of relativistic QM or that QFT is a theory of particles, as well as myths on black-hole entropy. The fact is that the existence of various theoretical and interpretational ambiguities underlying these myths does not yet allow us to accept them as proven facts. I review the main arguments and counterarguments lying behind these myths and conclude that QM is still a not-yet-completely-understood theory open to further fundamental research.Comment: 51 pages, pedagogic review, revised, new references, to appear in Found. Phy

Persistence of Ebola virus RNA in some body fluids of Ebola virus disease (EVD) survivors – the Nigerian experience

Introduction: Ebola virus (EBOV) has been shown to persist in some body fluids of Ebola Virus Disease (EVD) survivors with implication for future transmission particularly in Nigeria where EVD was experienced for the first time in 2014. Thus, this paper was aimed at providing information on the duration of persistence of EBOV in Nigeria. Materials and Methods: Ten consenting EVD survivors were enrolled. Baseline specimens; urine and semen (males), urine and high vaginal swab (HVS) (females) were obtained within one month after discharge from the Ebola Treatment Centre (ETC) and subsequently every fortnight. Samples were analyzed using quantitative Real-Star Filovirus Screen RT-PCR kit 1.0 at the National Reference Laboratory in Lagos.Results: Ten EVD survivors comprising 4 (40%) males and 6 (60%) females with age ranges of 28 to >33 years (mean age: 33.0 ± 6.9 years) were evaluated. EBOV RNA was not detected in the urine of all the participants and HVS from the females. However, EBOV RNA was detected in the semen of all 4 (100%) male participants at baseline, and at 2 months after discharge from the ETC. Two men were still positive for EBOV RNA 4 months after discharge from the ETC despite persistent negative vireamia. Conclusions: Our data confirm that a negative viremia in the convalescent period is not predictive of the absence of the virus in semen. Despite an early clearance of the virus from the urine and HVS, there was persistence of EBOV RNA in semen of male survivors 4 months after recovery