University of Warsaw

About: University of Warsaw is a education organization based out in Warsaw, Poland. It is known for research contribution in the topics: Population & Large Hadron Collider. The organization has 20832 authors who have published 56617 publications receiving 1185084 citations. The organization is also known as: Uniwersytet Warszawski & Warsaw University.

Curvature and isocurvature perturbations in two-field inflation

Abstract: We study cosmological perturbations in two-field inflation, allowing for non-standard kinetic terms. We calculate analytically the spectra of curvature and isocurvature modes at Hubble crossing, up to first order in the slow-roll parameters. We also compute numerically the evolution of the curvature and isocurvature modes from well within the Hubble radius until the end of inflation. We show explicitly for a few examples, including the recently proposed model of 'roulette' inflation, how isocurvature perturbations affect significantly the curvature perturbation between Hubble crossing and the end of inflation.

Phage as a modulator of immune responses: practical implications for phage therapy

Abstract: Although the natural hosts for bacteriophages are bacteria, a growing body of data shows that phages can also interact with some populations of mammalian cells, especially with cells of the immune system. In general, these interactions include two main aspects. The first is the phage immunogenicity, that is, the capacity of phages to induce specific immune responses, in particular the generation of specific antibodies against phage antigens. The other aspect includes the immunomodulatory activity of phages, that is, the nonspecific effects of phages on different functions of major populations of immune cells involved in both innate and adaptive immune responses. These functions include, among others, phagocytosis and the respiratory burst of phagocytic cells, the production of cytokines, and the generation of antibodies against nonphage antigens. The aim of this chapter is to discuss the interactions between phages and cells of the immune system, along with their implications for phage therapy. These topics are presented based on the results of experimental studies and unique data on immunomodulatory effects found in patients with bacterial infections treated with phage preparations.

Search for heavy neutrinos and W bosons with right-handed couplings in proton-proton collisions at sqrt(s) = 8 TeV

Abstract: A search for heavy, right-handed neutrinos, $$\mathrm {N}_{\ell }$$ ( $$\ell = \mathrm {e}, \mu $$ ), and right-handed $$\mathrm {W}_{\mathrm {R}}$$ bosons, which arise in the left-right symmetric extensions of the standard model, has been performed by the CMS experiment. The search was based on a sample of two lepton plus two jet events collected in proton–proton collisions at a center-of-mass energy of 8 $$\,\text {TeV}$$ corresponding to an integrated luminosity of 19.7 $$\mathrm{fb}^{-1}$$ . For models with strict left-right symmetry, and assuming only one $$\mathrm {N}_{\ell }$$ flavor contributes significantly to the $$\mathrm {W}_{\mathrm {R}}$$ decay width, the region in the two-dimensional $$(M_{\mathrm {W}_{\mathrm {R}}}, M_{\mathrm {N}_{\ell }})$$ mass plane excluded at a 95 % confidence level extends to approximately $$M_{\mathrm {W}_{\mathrm {R}}} = 3.0\,\text {TeV} $$ and covers a large range of neutrino masses below the $$\mathrm {W}_{\mathrm {R}}$$ boson mass, depending on the value of $$M_{\mathrm {W}_{\mathrm {R}}}$$ . This search significantly extends the $$(M_{\mathrm {W}_{\mathrm {R}}}, M_{\mathrm {N}_{\ell }})$$ exclusion region beyond previous results.

Luminosities and mass-loss rates of SMC and LMC AGB stars and red supergiants

Abstract: Context. Mass loss is one of the fundamental properties of Asymptotic Giant Branch (AGB) stars, and through the enrichment of the interstellar medium, AGB stars are key players in the life cycle of dust and gas in the universe. However, a quantitative understanding of the mass-loss process is still largely lacking, particularly its dependence on metallicity. Aims. To investigate the relation between mass loss, luminosity and pulsation period for a large sample of evolved stars in the Small and Large Magellanic Cloud.Methods. Dust radiative transfer models are presented for 101 carbon stars and 86 oxygen-rich evolved stars in the Magellanic Clouds for which 5–35 μ m Spitzer IRS spectra are available. The spectra are complemented with available optical and infrared photometry to construct the spectral energy distribution. A minimisation procedure is used to fit luminosity, mass-loss rate and dust temperature at the inner radius. Different effective temperatures and dust content are also considered. Periods from the literature and from new OGLE-III data are compiled and derived.Results. We derive (dust) mass-loss rates and luminosities for the entire sample. Based on luminosities, periods and amplitudes and colours, the O-rich stars are classified as foreground objects, AGB stars and Red Super Giants. For the O-rich stars silicates based on laboratory optical constants are compared to “astronomical silicates”. Overall, the grain type by Volk & Kwok (1988, ApJ, 331, 435) fits the data best. However, the fit based on laboratory optical constants for the grains can be improved by abandoning the small-particle limit. The influence of grain size, core-mantle grains and porosity are explored. A computationally convenient method that seems to describe the observed properties in the 10 μ m window are a distribution of hollow spheres with a large vacuum fraction (typically 70%), and grain size of about 1 μ m. Relations between mass-loss rates and luminosity and pulsation period are presented and compared to the predictions of evolutionary models, those by Vassiliadis & Wood (1993, ApJ, 413, 641) and their adopted mass-loss recipe, and those based on a Reimers mass-loss law with a scaling of a factor of five. The Vassiliadis & Wood models describe the data better, although there are also some deficiencies, in particular to the maximum adopted mass-loss rate. The derived mass-loss rates are compared to predictions by dynamical wind models and appear consistent with them at a level of a factor 2–4. A better understanding requires the determination of the expansion velocity from future observations from ALMA. The OGLE-III data reveal an O-rich star in the SMC with a period of 1749 days. Its absolute magnitude of makes it a good candidate for a super-AGB star.