Extreme objects with arbitrary large mass, or density, and arbitrary size

We consider a generalization of the interior Schwarzschild solution that we match to the exterior one to build global C^1 models that can have arbitrary large mass, or density, with arbitrary size. This is possible because of a new insight into the problem of localizing the center of symmetry of the models and the use of principal transformations to understand the structure of space.Comment: 20 pages, 6 figures. Fixed one reference. Added a new equatio

Quantum dynamics of local phase differences between reservoirs of driven interacting bosons separated by simple aperture arrays

We present a derivation of the effective action for the relative phase of driven, aperture-coupled reservoirs of weakly-interacting condensed bosons from a (3+1)-D microscopic model with local U(1) gauge symmetry. We show that inclusion of local chemical potential and driving velocity fields as a gauge field allows derivation of the hydrodynamic equations of motion for the driven macroscopic phase differences across simple aperture arrays. For a single aperture, the current-phase equation for driven flow contains sinusoidal, linear, and current-bias contributions. We compute the renormalization group (RG) beta function of the periodic potential in the effective action for small tunneling amplitudes and use this to analyze the temperature dependence of the low-energy current-phase relation, with application to the transition from linear to sinusoidal current-phase behavior observed in experiments by Hoskinson et al. \cite{packard} for liquid $^{4}$He driven through nanoaperture arrays. Extension of the microscopic theory to a two-aperture array shows that interference between the microscopic tunneling contributions for individual apertures leads to an effective coupling between apertures which amplifies the Josephson oscillations in the array. The resulting multi-aperture current-phase equations are found to be equivalent to a set of equations for coupled pendula, with microscopically derived couplings.Comment: 16 pages, 5 figures v2: typos corrected, RG phase diagram correcte

Western European Populations of the Ichneumonid Wasp Hyposoter didymator Belong to a Single Taxon

Hyposoter didymator (Hymenoptera, Ichneumonidae) is a generalist solitary endoparasitoid of noctuid larvae. In the present work, we tested whether populations of H. didymator were divided in several genetically distinct taxa as described for many other generalist parasitoid species, and whether differences in H. didymator parasitism rates were explained by the insect host species and/or by the plant on which these hosts were feeding on. The genetic analysis of natural populations collected in different regions in France and Spain on seven different insect hosts and seven different host plants (775 individuals) showed that H. didymator populations belong to a unique single taxon. However, H. didymator seems to be somewhat specialized. Indeed, in the fields it more often parasitized Helicoverpa armigera compared to the other host species collected in the present work. Also, H. didymator parasitism rates in field conditions and semi-field experimental studies were dependent on the host plants on which H. armigera larvae are feeding. Still, H. didymator can occur occasionally on non-preferred noctuid species. One hypothesis explaining the ability of H. didymator to switch hosts in natura could be related to fluctuating densities of the preferred host over the year; this strategy would allow the parasitoid to avoid seasonal population collapses

Analysis of Virion Structural Components Reveals Vestiges of the Ancestral Ichnovirus Genome

Many thousands of endoparasitic wasp species are known to inject polydnavirus (PDV) particles into their caterpillar host during oviposition, causing immune and developmental dysfunctions that benefit the wasp larva. PDVs associated with braconid and ichneumonid wasps, bracoviruses and ichnoviruses respectively, both deliver multiple circular dsDNA molecules to the caterpillar. These molecules contain virulence genes but lack core genes typically involved in particle production. This is not completely unexpected given that no PDV replication takes place in the caterpillar. Particle production is confined to the wasp ovary where viral DNAs are generated from proviral copies maintained within the wasp genome. We recently showed that the genes involved in bracovirus particle production reside within the wasp genome and are related to nudiviruses. In the present work we characterized genes involved in ichnovirus particle production by analyzing the components of purified Hyposoter didymator Ichnovirus particles by LC-MS/MS and studying their organization in the wasp genome. Their products are conserved among ichnovirus-associated wasps and constitute a specific set of proteins in the virosphere. Strikingly, these genes are clustered in specialized regions of the wasp genome which are amplified along with proviral DNA during virus particle replication, but are not packaged in the particles. Clearly our results show that ichnoviruses and bracoviruses particles originated from different viral entities, thus providing an example of convergent evolution where two groups of wasps have independently domesticated viruses to deliver genes into their hosts

Stellar structure and compact objects before 1940: Towards relativistic astrophysics

Since the mid-1920s, different strands of research used stars as "physics laboratories" for investigating the nature of matter under extreme densities and pressures, impossible to realize on Earth. To trace this process this paper is following the evolution of the concept of a dense core in stars, which was important both for an understanding of stellar evolution and as a testing ground for the fast-evolving field of nuclear physics. In spite of the divide between physicists and astrophysicists, some key actors working in the cross-fertilized soil of overlapping but different scientific cultures formulated models and tentative theories that gradually evolved into more realistic and structured astrophysical objects. These investigations culminated in the first contact with general relativity in 1939, when J. Robert Oppenheimer and his students George Volkoff and Hartland Snyder systematically applied the theory to the dense core of a collapsing neutron star. This pioneering application of Einstein's theory to an astrophysical compact object can be regarded as a milestone in the path eventually leading to the emergence of relativistic astrophysics in the early 1960s.Comment: 83 pages, 4 figures, submitted to the European Physical Journal

Photoperiodic Modulation of Circadian Clock and Reproductive Axis Gene Expression in the Pre-Pubertal European Sea Bass Brain

The acquisition of reproductive competence requires the activation of the brain-pituitary-gonad (BPG) axis, which in most vertebrates, including fishes, is initiated by changes in photoperiod. In the European sea bass long-term exposure to continuous light (LL) alters the rhythm of reproductive hormones, delays spermatogenesis and reduces the incidence of precocious males. In contrast, an early shift from long to short photoperiod (AP) accelerates spermatogenesis. However, how photoperiod affects key genes in the brain to trigger the onset of puberty is still largely unknown. Here, we investigated if the integration of the light stimulus by clock proteins is sufficient to activate key genes that trigger the BPG axis in the European sea bass. We found that the clock genes clock, npas2, bmal1 and the BPG genes gnrh, kiss and kissr share conserved transcription factor frameworks in their promoters, suggesting co-regulation. Other gene promoters of the BGP axis were also predicted to be co-regulated by the same frameworks. Co-regulation was confirmed through gene expression analysis of brains from males exposed to LL or AP photoperiod compared to natural conditions: LL fish had suppressed gnrh1, kiss2, galr1b and esr1, while AP fish had stimulated npas2, gnrh1, gnrh2, kiss2, kiss1rb and galr1b compared to NP. It is concluded that fish exposed to different photoperiods present significant expression differences in some clock and reproductive axis related genes well before the first detectable endocrine and morphological responses of the BPG axis.European Community [222719 - LIFECYCLE]; Foundation for Science and Technology of Portugal (FCT) [SFRH/BPD/66742/2009, PEst-C/MAR/LA0015/2011]; Valencian Regional Goverment [Prometeo II/2014/051]; Spanish Ministry of Science and Innovation (MICINN) [CSD 2007-0002]info:eu-repo/semantics/publishedVersio

Exact Hypersurface-Homogeneous Solutions in Cosmology and Astrophysics

A framework is introduced which explains the existence and similarities of most exact solutions of the Einstein equations with a wide range of sources for the class of hypersurface-homogeneous spacetimes which admit a Hamiltonian formulation. This class includes the spatially homogeneous cosmological models and the astrophysically interesting static spherically symmetric models as well as the stationary cylindrically symmetric models. The framework involves methods for finding and exploiting hidden symmetries and invariant submanifolds of the Hamiltonian formulation of the field equations. It unifies, simplifies and extends most known work on hypersurface-homogeneous exact solutions. It is shown that the same framework is also relevant to gravitational theories with a similar structure, like Brans-Dicke or higher-dimensional theories.Comment: 41 pages, REVTEX/LaTeX 2.09 file (don't use LaTeX2e !!!) Accepted for publication in Phys. Rev.

Research on information systems failures and successes: Status update and future directions

The final publication is available at Springer via http://dx.doi.org/10.1007/s10796-014-9500-yInformation systems success and failure are among the most prominent streams in IS research. Explanations of why some IS fulfill their expectations, whereas others fail, are complex and multi-factorial. Despite the efforts to understand the underlying factors, the IS failure rate remains stubbornly high. A Panel session was held at the IFIP Working Group 8.6 conference in Bangalore in 2013 which forms the subject of this Special Issue. Its aim was to reflect on the need for new perspectives and research directions, to provide insights and further guidance for managers on factors enabling IS success and avoiding IS failure. Several key issues emerged, such as the need to study problems from multiple perspectives, to move beyond narrow considerations of the IT artifact, and to venture into underexplored organizational contexts, such as the public sector. © 2014 Springer Science+Business Media New York

A comprehensive transcriptome and immune-gene repertoire of the lepidopteran model host Galleria mellonella

<p>Abstract</p> <p>Background</p> <p>The larvae of the greater wax moth <it>Galleria mellonella </it>are increasingly used (i) as mini-hosts to study pathogenesis and virulence factors of prominent bacterial and fungal human pathogens, (ii) as a whole-animal high throughput infection system for testing pathogen mutant libraries, and (iii) as a reliable host model to evaluate the efficacy of antibiotics against human pathogens. In order to compensate for the lack of genomic information in <it>Galleria</it>, we subjected the transcriptome of different developmental stages and immune-challenged larvae to next generation sequencing.</p> <p>Results</p> <p>We performed a <it>Galleria </it>transcriptome characterization on the Roche 454-FLX platform combined with traditional Sanger sequencing to obtain a comprehensive transcriptome. To maximize sequence diversity, we pooled RNA extracted from different developmental stages, larval tissues including hemocytes, and from immune-challenged larvae and normalized the cDNA pool. We generated a total of 789,105 pyrosequencing and 12,032 high-quality Sanger EST sequences which clustered into 18,690 contigs with an average length of 1,132 bases. Approximately 40% of the ESTs were significantly similar (<it>E </it>≤ e^-03) to proteins of other insects, of which 45% have a reported function. We identified a large number of genes encoding proteins with established functions in immunity related sensing of microbial signatures and signaling, as well as effector molecules such as antimicrobial peptides and inhibitors of microbial proteinases. In addition, we found genes known as mediators of melanization or contributing to stress responses. Using the transcriptomic data, we identified hemolymph peptides and proteins induced upon immune challenge by 2D-gelelectrophoresis combined with mass spectrometric analysis.</p> <p>Conclusion</p> <p>Here, we have developed extensive transcriptomic resources for <it>Galleria</it>. The data obtained is rich in gene transcripts related to immunity, expanding remarkably our knowledge about immune and stress-inducible genes in <it>Galleria </it>and providing the complete sequences of genes whose primary structure have only partially been characterized using proteomic methods. The generated data provide for the first time access to the genetic architecture of immunity in this model host, allowing us to elucidate the molecular mechanisms underlying pathogen and parasite response and detailed analyses of both its immune responses against human pathogens, and its coevolution with entomopathogens.</p