Self-similar collapse of collisional gas in an expanding Universe

Similarity solutions are found for the adiabatic collapse of density perturbations $\delta M/M \propto r^{-s}$ $(s>0)$ in a flat universe containing collisional gas only. The solutions are obtained for planar, cylindrical, and spherical perturbations with zero initial pressure. For adiabatic index $\gamma\ge 4/3$, a shock develops at a fixed fraction of the current turnaround distance. Near the center of a spherical perturbations with $\gamma>4/3$ and $s>1/2$, the gas is in quasi-hydrostatic equilibrium (pressure supported) and has an asymptotic power law density profile, $\rho\sim r^{-3s/(s+1)}$, independent of $\gamma$. For $s\le 1/2$, the profile depends on $\gamma$, the pressure is finite, the temperature decreases inward, and gravity dominates pressure causing a continuous inward flow. Although for $1/2<s<2$ the temperature decreases at the center, the gas is pressure supported. The pressure is finite in cylindrical perturbations for $s\le 2(\gamma-1)/(3\gamma-4)$, and in planar perturbations for any $s>0$. We also derive the asymptotic behaviour of the gas variables near the center in a universe dominated by collisionless matter. In such a universe, the gas in a spherical perturbation with $s<2$ cannot be pressure supported and the temperature approaches a constant near the center. The solutions and the asymptotic behaviour are relevant for modelling the gas distribution in galaxy clusters and pancake-like superclusters, and determining the structure of haloes of self-interacting dark matter with large interaction cross section.Comment: version accepted for publication in the MNRA

Relic abundance of mass-varying cold dark matter particles

In models of coupled dark energy and dark matter the mass of the dark matter particle depends on the cosmological evolution of the dark energy field. In this note we exemplify in a simple model the effects of this mass variation on the relic abundance of cold dark matter.Comment: 5 pages, no figures. Version published in PL

A proangiogenic signaling axis in myeloid cells promotes malignant progression of glioma

Tumors are capable of coopting hematopoietic cells to create a suitable microenvironment to support malignant growth. Here, we have demonstrated that upregulation of kinase insert domain receptor (KDR), also known as VEGFR2, in a myeloid cell sublineage is necessary for malignant progression of gliomas in transgenic murine models and is associated with high-grade tumors in patients. KDR expression increased in myeloid cells as myeloid-derived suppressor cells (MDSCs) accumulated, which was associated with the transformation and progression of low-grade fibrillary astrocytoma to high-grade anaplastic gliomas. KDR deficiency in murine BM-derived cells (BMDCs) suppressed the differentiation of myeloid lineages and reduced granulocytic/monocytic populations. The depletion of myeloid-derived KDR compromised its proangiogenic function, which inhibited the angiogenic switch necessary for malignant progression of low-grade to high-grade tumors. We also identified inhibitor of DNA binding protein 2 (ID2) as a key upstream regulator of KDR activation during myeloid differentiation. Deficiency of ID2 in BMDCs led to downregulation of KDR, suppression of proangiogenic myeloid cells, and prevention of low-grade to high-grade transition. Tumor-secreted TGF-β and granulocyte-macrophage CSF (GM-CSF) enhanced the KDR/ID2 signaling axis in BMDCs. Our results suggest that modulation of KDR/ID2 signaling may restrict tumor-associated myeloid cells and could potentially be a therapeutic strategy for preventing transformation of premalignant gliomas.This study was supported by the Department of Defense Con- gressionally Directed Medical Research Programs (DOD CDMRP, CA120318 to Y. Huang), Elizabeth’s Hope (J. Greenfield), the Starr Foundation, the Paduano Foundation, the Champalimaud Foun- dation, the Malcolm Hewitt Wiener Foundation, the POETIC Foundation, the Sohn Foundation, the Hartwell Foundation, and the Children’s Cancer and Blood Foundation (all to D. Lyden). Address correspondence to: David Lyden, Department of Pediatrics, Weill Medical Medicine, 413 E. 69th Street, Box 284, New York, New York 10021, USA. Phone: 646.962.6238; E-mail: [email protected]. Or to: Jeffrey P. Greenfield, Department of Neurological Surgery, Weill Cornell Medicine, 525 E 68th Street, Box 99, New York, New York 10065, USA. Phone: 212.746.2363; E-mail: [email protected]. HP’s present address is: Microenvironment and Metastasis Group, Department of Molecular Oncology, Spanish National Cancer Research Center (CNIO), Madrid, Spain.S

Astrophysical Constraints on Dark Matter

Astrophysics gives evidence for the existence of Dark Matter and puts constraints on its nature. The Cold Dark Matter model has become "standard" cosmology combined with a cosmological constant. There are indications that "Cold" Dark Matter could be "warmer" than initially discussed. This paper reviews the main information on the Cold/Warm nature of Dark Matter.Comment: Proceedings of the 3rd International conference on Directional Detection of Dark Matter (CYGNUS 2011), Aussois, France, 8-10 June 201

Inversion of the Lyman-α\alpha forest: 3D investigation of the intergalactic medium

We discuss the implementation of Bayesian inversion methods in order to recover the properties of the intergalactic medium from observations of the neutral hydrogen Lyman-$\alpha$ absorptions observed in the spectra of high redshift quasars (the so-called Lyman-$\alpha$ forest). We use two complementary schemes (i) a constrained Gaussian random field linear approach and (ii) a more general non-linear explicit Bayesian deconvolution method which offers in particular the possibility to constrain the parameters of the equation of state for the gas. While relying on prior assumption for the two-point correlation functions, we show how to recover, at least qualitatively, the 3D topology of the large scale structures in redshift space by inverting a suitable network of adjacent, low resolution lines of sight. We also discuss the inversion of single lines of sight observed at high spectral resolution. Our preliminary investigations suggest that the explicit Bayesian method can be used to derive quantitative information on the physical state of the gas. Redshift distortion is considered by simultaneous constrained reconstruction of the velocity and the density field in real space while assuming statistical correlation between the two fields. The method seems to work well in the strong prior regime where peculiar velocities are assumed to be the most likely realization in the density field. Finally, we investigate the effect of line of sight separation and number of lines of sight. Our analyses suggest that multiple low resolution lines of sight could be used to improve most likely velocity reconstruction on a high resolution line of sight.Comment: 24 pages, 9 figures, LateX (MN format), accepted for publication in MNRA

Quasiparticle interference and strong electron-mode coupling in the quasi-one-dimensional bands of Sr2RuO4

The single-layered ruthenate Sr$_2$RuO$_4$ has attracted a great deal of interest as a spin-triplet superconductor with an order parameter that may potentially break time reversal invariance and host half-quantized vortices with Majorana zero modes. While the actual nature of the superconducting state is still a matter of controversy, it has long been believed that it condenses from a metallic state that is well described by a conventional Fermi liquid. In this work we use a combination of Fourier transform scanning tunneling spectroscopy (FT-STS) and momentum resolved electron energy loss spectroscopy (M-EELS) to probe interaction effects in the normal state of Sr$_2$RuO$_4$. Our high-resolution FT-STS data show signatures of the \beta-band with a distinctly quasi-one-dimensional (1D) character. The band dispersion reveals surprisingly strong interaction effects that dramatically renormalize the Fermi velocity, suggesting that the normal state of Sr$_2$RuO$_4$ is that of a 'correlated metal' where correlations are strengthened by the quasi 1D nature of the bands. In addition, kinks at energies of approximately 10meV, 38meV and 70meV are observed. By comparing STM and M-EELS data we show that the two higher energy features arise from coupling with collective modes. The strong correlation effects and the kinks in the quasi 1D bands may provide important information for understanding the superconducting state. This work opens up a unique approach to revealing the superconducting order parameter in this compound

Is vaccine the magic bullet for malaria elimination? A reality check

Malaria remains a major health burden especially for the developing countries. Despite concerted efforts at using the current control tools, such as bed nets, anti malarial drugs and vector control measures, the disease is accountable for close to a million deaths annually. Vaccines have been proposed as a necessary addition to the armamentarium that could work towards elimination and eventual eradication of malaria in view of their historical significance in combating infectious diseases. However, because malaria vaccines would work differently depending on the targeted parasite stage, this review addresses the potential impact various malaria vaccine types could have on transmission. Further, because of the wide variation in the epidemiology of malaria across the endemic regions, this paper proposes that the ideal approach to malaria control ought to be tailor-made depending on the specific context. Finally, it suggests that although it is highly desirable to anticipate and aim for malaria elimination and eventual eradication, many affected regions should prioritize reduction of mortality and morbidity before aspiring for elimination

Forecasting drug utilization and expenditure in a metropolitan health region

<p>Abstract</p> <p>Background</p> <p>New pharmacological therapies are challenging the healthcare systems, and there is an increasing need to assess their therapeutic value in relation to existing alternatives as well as their potential budget impact. Consequently, new models to introduce drugs in healthcare are urgently needed. In the metropolitan health region of Stockholm, Sweden, a model has been developed including early warning (horizon scanning), forecasting of drug utilization and expenditure, critical drug evaluation as well as structured programs for the introduction and follow-up of new drugs. The aim of this paper is to present the forecasting model and the predicted growth in all therapeutic areas in 2010 and 2011.</p> <p>Methods</p> <p>Linear regression analysis was applied to aggregate sales data on hospital sales and dispensed drugs in ambulatory care, including both reimbursed expenditure and patient co-payment. The linear regression was applied on each pharmacological group based on four observations 2006-2009, and the crude predictions estimated for the coming two years 2010-2011. The crude predictions were then adjusted for factors likely to increase or decrease future utilization and expenditure, such as patent expiries, new drugs to be launched or new guidelines from national bodies or the regional Drug and Therapeutics Committee. The assessment included a close collaboration with clinical, clinical pharmacological and pharmaceutical experts from the regional Drug and Therapeutics Committee.</p> <p>Results</p> <p>The annual increase in total expenditure for prescription and hospital drugs was predicted to be 2.0% in 2010 and 4.0% in 2011. Expenditures will increase in most therapeutic areas, but most predominantly for antineoplastic and immune modulating agents as well as drugs for the nervous system, infectious diseases, and blood and blood-forming organs.</p> <p>Conclusions</p> <p>The utilisation and expenditure of drugs is difficult to forecast due to uncertainties about the rate of adoption of new medicines and various ongoing healthcare reforms and activities to improve the quality and efficiency of prescribing. Nevertheless, we believe our model will be valuable as an early warning system to start developing guidance for new drugs including systems to monitor their effectiveness, safety and cost-effectiveness in clinical practice.</p