High-density Skyrmion matter and Neutron Stars

We examine neutron star properties based on a model of dense matter composed of B=1 skyrmions immersed in a mesonic mean field background. The model realizes spontaneous chiral symmetry breaking non-linearly and incorporates scale-breaking of QCD through a dilaton VEV that also affects the mean fields. Quartic self-interactions among the vector mesons are introduced on grounds of naturalness in the corresponding effective field theory. Within a plausible range of the quartic couplings, the model generates neutron star masses and radii that are consistent with a preponderance of observational constraints, including recent ones that point to the existence of relatively massive neutron stars with mass M 1.7 Msun and radius R (12-14) km. If the existence of neutron stars with such dimensions is confirmed, matter at supra-nuclear density is stiffer than extrapolations of most microscopic models suggest.Comment: 27 pages, 5 figures, AASTeX style; to be published in The Astrophysical Journa

Constraining phases of quark matter with studies of r-mode damping in neutron stars

The r-mode instability in rotating compact stars is used to constrain the phase of matter at high density. The color-flavor-locked phase with kaon condensation (CFL-K0) and without (CFL) is considered in the temperature range 10^8K < T <10^{11} K. While the bulk viscosity in either phase is only effective at damping the r-mode at temperatures T > 10^{11} K, the shear viscosity in the CFL-K0 phase is the only effective damping agent all the way down to temperatures T > 10^8 K characteristic of cooling neutron stars. However, it cannot keep the star from becoming unstable to gravitational wave emission for rotation frequencies f ~ 56-11 Hz at T ~ 10^8-10^9 K. Stars composed almost entirely of CFL or CFL-K0 matter are ruled out by observation of rapidly rotating neutron stars, indicating that dissipation at the quark-hadron interface or nuclear crust interface must play a key role in damping the instability.Comment: 8 pages, 2 figure

Numerical Simulation of the Hydrodynamical Combustion to Strange Quark Matter

We present results from a numerical solution to the burning of neutron matter inside a cold neutron star into stable (u,d,s) quark matter. Our method solves hydrodynamical flow equations in 1D with neutrino emission from weak equilibrating reactions, and strange quark diffusion across the burning front. We also include entropy change due to heat released in forming the stable quark phase. Our numerical results suggest burning front laminar speeds of 0.002-0.04 times the speed of light, much faster than previous estimates derived using only a reactive-diffusive description. Analytic solutions to hydrodynamical jump conditions with a temperature dependent equation of state agree very well with our numerical findings for fluid velocities. The most important effect of neutrino cooling is that the conversion front stalls at lower density (below approximately 2 times saturation density). In a 2-dimensional setting, such rapid speeds and neutrino cooling may allow for a flame wrinkle instability to develop, possibly leading to detonation.Comment: 5 pages, 3 figures (animations online at http://www.capca.ucalgary.ca/~bniebergal/webPHP/research.php

The Strange Star Surface: A Crust with Nuggets

We reexamine the surface composition of strange stars. Strange quark stars are hypothetical compact stars which could exist if strange quark matter was absolutely stable. It is widely accepted that they are characterized by an enormous density gradient ($~10^{26}$ g/cm$^4$) and large electric fields at surface. By investigating the possibility of realizing a heterogeneous crust, comprised of nuggets of strange quark matter embedded in an uniform electron background, we find that the strange star surface has a much reduced density gradient and negligible electric field. We comment on how our findings will impact various proposed observable signatures for strange stars.Comment: 4 pages, 2 figure

Bremsstrahlung neutrinos from electron-electron scattering in a relativistic degenerate electron plasma

We present a calculation of neutrino pair bremsstrahlung due to electron-electron scattering in a relativistic degenerate plasma of electrons. Proper treatment of the in-medium photon propagator, i.e., inclusion of Debye screening of the longitudinal part and Landau damping of the transverse part, leads to a neutrino emissivity which is several orders of magnitude larger than when Debye screening is imposed for the tranverse part. Our results show that this in-medium process can compete with other sources of neutrino radiation and can, in some cases, even be the dominant neutrino emission mechanism. We also discuss the natural extension to quark-quark bremsstrahlung in gapped and ungapped quark matter.Comment: 15 pages, 7 figure

Quark Matter in Neutron Stars: An apercu

The existence of deconfined quark matter in the superdense interior of neutron stars is a key question that has drawn considerable attention over the past few decades. Quark matter can comprise an arbitrary fraction of the star, from 0 for a pure neutron star to 1 for a pure quark star, depending on the equation of state of matter at high density. From an astrophysical viewpoint, these two extreme cases are generally expected to manifest different observational signatures. An intermediate fraction implies a hybrid star, where the interior consists of mixed or homogeneous phases of quark and nuclear matter, depending on surface and Coulomb energy costs, as well as other finite size and screening effects. In this brief review article, we discuss what we can deduce about quark matter in neutron stars in light of recent exciting developments in neutron star observations. We state the theoretical ideas underlying the equation of state of dense quark matter, including color superconducting quark matter. We also highlight recent advances stemming from re-examination of an old paradigm for the surface structure of quark stars and discuss possible evolutionary scenarios from neutron stars to quark stars, with emphasis on astrophysical observations.Comment: 15 pages, 1 figure. Invited review for Modern Physics Letters

Evaluation of Annual Statice (Limonium sinuatum L.) Cultivars

A field study was conducted during rabi season of 2003-2004 to evaluate the potential of statice cultivars as cut flower crop in the field of Department of Floriculture and Landscape Gardening, K.R.C. College of Horticulture, Arabhavi. The experiment was laid out as a Randomised Block Design with four replications. The panicles of each variety were harvested when calycys of individual flower have mostly opened and showing colour. The cultivar Turbo White recorded maximum plant height (21.78 cm), panicle length (80.94 cm), stem diameter (0.61 cm), no. of leaves (186.60), maximum fresh weight of panicles (530.09 g/plant), plant spread 62.15 cm2 and remained superior over others. The results are in agreement with the findings of Angadi (2000) in China aster. Maximum panicle production per plant (25.64) was recorded in cv. Turbo White, which was on par with the cultivar Turbo Carmine (22.54). The results were in line with the findings of Kumar et al. (1998) in annual statice Turbo White. The cultivar Turbo White was good in quality parameters by recording maximum panicle length, girth and number of branches per panicle. It was also vigorous in vegetative growth. Therefore, the cultivar could produce better quality panicles and found to be suitable for semi arid regions

Proteomic analysis of iron acquisition, metabolic and regulatory responses of \u3cem\u3eYersinia pestis\u3c/em\u3e to iron starvation

BACKGROUND: The Gram-negative bacterium Yersinia pestis is the causative agent of the bubonic plague. Efficient iron acquisition systems are critical to the ability of Y. pestis to infect, spread and grow in mammalian hosts, because iron is sequestered and is considered part of the innate host immune defence against invading pathogens. We used a proteomic approach to determine expression changes of iron uptake systems and intracellular consequences of iron deficiency in the Y. pestis strain KIM6+ at two physiologically relevant temperatures (26°C and 37°C). RESULTS: Differential protein display was performed for three Y. pestis subcellular fractions. Five characterized Y. pestis iron/siderophore acquisition systems (Ybt, Yfe, Yfu, Yiu and Hmu) and a putative iron/chelate outer membrane receptor (Y0850) were increased in abundance in iron-starved cells. The iron-sulfur (Fe-S) cluster assembly system Suf, adapted to oxidative stress and iron starvation in E. coli, was also more abundant, suggesting functional activity of Suf in Y. pestis under iron-limiting conditions. Metabolic and reactive oxygen-deactivating enzymes dependent on Fe-S clusters or other iron cofactors were decreased in abundance in iron-depleted cells. This data was consistent with lower activities of aconitase and catalase in iron-starved vs. iron-rich cells. In contrast, pyruvate oxidase B which metabolizes pyruvate via electron transfer to ubiquinone-8 for direct utilization in the respiratory chain was strongly increased in abundance and activity in iron-depleted cells. CONCLUSIONS: Many protein abundance differences were indicative of the important regulatory role of the ferric uptake regulator Fur. Iron deficiency seems to result in a coordinated shift from iron-utilizing to iron-independent biochemical pathways in the cytoplasm of Y. pestis. With growth temperature as an additional variable in proteomic comparisons of the Y. pestis fractions (26°C and 37°C), there was little evidence for temperature-specific adaptation processes to iron starvation

Proteomic analysis of iron acquisition, metabolic and regulatory responses of Yersinia pestis to iron starvation

<p>Abstract</p> <p>Background</p> <p>The Gram-negative bacterium <it>Yersinia pestis </it>is the causative agent of the bubonic plague. Efficient iron acquisition systems are critical to the ability of <it>Y. pestis </it>to infect, spread and grow in mammalian hosts, because iron is sequestered and is considered part of the innate host immune defence against invading pathogens. We used a proteomic approach to determine expression changes of iron uptake systems and intracellular consequences of iron deficiency in the <it>Y. pestis </it>strain KIM6+ at two physiologically relevant temperatures (26°C and 37°C).</p> <p>Results</p> <p>Differential protein display was performed for three <it>Y. pestis </it>subcellular fractions. Five characterized <it>Y. pestis </it>iron/siderophore acquisition systems (Ybt, Yfe, Yfu, Yiu and Hmu) and a putative iron/chelate outer membrane receptor (Y0850) were increased in abundance in iron-starved cells. The iron-sulfur (Fe-S) cluster assembly system Suf, adapted to oxidative stress and iron starvation in <it>E. coli</it>, was also more abundant, suggesting functional activity of Suf in <it>Y. pestis </it>under iron-limiting conditions. Metabolic and reactive oxygen-deactivating enzymes dependent on Fe-S clusters or other iron cofactors were decreased in abundance in iron-depleted cells. This data was consistent with lower activities of aconitase and catalase in iron-starved <it>vs</it>. iron-rich cells. In contrast, pyruvate oxidase B which metabolizes pyruvate via electron transfer to ubiquinone-8 for direct utilization in the respiratory chain was strongly increased in abundance and activity in iron-depleted cells.</p> <p>Conclusions</p> <p>Many protein abundance differences were indicative of the important regulatory role of the ferric uptake regulator Fur. Iron deficiency seems to result in a coordinated shift from iron-utilizing to iron-independent biochemical pathways in the cytoplasm of <it>Y. pestis</it>. With growth temperature as an additional variable in proteomic comparisons of the <it>Y. pestis </it>fractions (26°C and 37°C), there was little evidence for temperature-specific adaptation processes to iron starvation.</p

Health Systems Global, the new international society for health systems research

I see starting a new international society for health systems research as a step towards renewing our collective commitment to global health goals; in particular I see the proposed society as marking a commitment to equitable universal health care. From my perspective it is important that we are clear on the values that underpin the development of this new society. In addition, the society needs a clear strategy to help achieve this goal, in particular we need to first identify who is the target audience or constituency for the society; and second, the tools through which the society will work and how the society will engage with its audience.Fil: Kraushaar, D.. No especifíca;Fil: Kieny, M. P.. Organizacion Mundial de la Salud; ArgentinaFil: Lazarus, J. V.. Health Systems Global; Estados UnidosFil: Bermejo, R.. University Of The Philippines; FilipinasFil: Abimbola, S.. National Primary Health Care Development Agency; NigeriaFil: Prashanth, N.. Institute Of Public Health; IndiaFil: Flores, W.. Center For The Study Of Equity And Governance In Health; GuatemalaFil: Freddie Ssengooba. Makerere University School Of Public Health; UgandaFil: Maceira, Daniel Alejandro. Centro de Estudios de Estado y Sociedad; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentin