764 research outputs found
Ultraviolet light curves of U Geminorum and VW Hydri
Ultraviolet light curves were obtained for the quiescent dwarf novae U Gem and VW Hyi. The amplitude of the hump associated with the accretion hot spot is much smaller in the UV than in the visible. This implies that the bright spot temperature is roughly 12000 K if it is optically thick. The flux distribution of U Gem in quiescence cannot be fitted by model spectra of steady state, viscous accretion disks. The absolute luminosity, the flux distribution, and the far UV spectrum suggest that the primary star is visible in the far UV. The optical UV flux distribution of VW Hyi can be matched roughly by the model accretion disks
The 1981 outburst of the old nova GK Persei
Old nova GK Per was observed in 1981 with the IUE, during its rise, maximum, and subsequent return to minimum. In outburst, GK Per is luminous but much redder than dwarf novae or standard model accretion disks. The observed spectrum can be explained qualitatively with the Ghosh and Lamb (1979) model for the interaction of an accretion disk with the magnetic field of the accreting white dwarf. The N V and He2 are enhanced relative to other emission lines during outburst. This can be understood with photoionization by very soft X-rays having a luminosity comparable to that of the hard X-rays
Making video communication mobile by using a small humanoid social assistive robot
There is a high need among older persons to maintain their social contacts and to stay involved in social life. In this area of social communication ICT and assistive technology can bring a significant support provided that the actual needs and preferences of the user groups are actually met. The paper describes an innovative solution consisting of a mobile video communication facility using a LED projector which is integrated in a social assistive robot system developed in the framework of the KSERA project
Making video communication mobile by using a small humanoid social assistive robot
There is a high need among older persons to maintain their social contacts and to stay involved in social life. In this area of social communication ICT and assistive technology can bring a significant support provided that the actual needs and preferences of the user groups are actually met. The paper describes an innovative solution consisting of a mobile video communication facility using a LED projector which is integrated in a social assistive robot system developed in the framework of the KSERA project
Fly ash-derived MCM-41 as a low-cost silica support for polyethyleneimine in post-combustion CO2 capture
The mesoporous silicate molecular sieve, MCM-41, has been synthesized from pulverized coal fly ash (PFA), where the silicate filtrate used is a by-product from hydrothermal zeolite production. Rice husk ash was also used for comparison but fusion with sodium hydroxide was used to prepare the silicate filtrate, along similar lines to earlier reports of using PFA as a precursor for MCM-41 synthesis. The MCM-41 samples are chemically and mineralogically similar to a commercially available sample, but with higher pore volumes dominated by mesopores (0.92–1.13 cf. 0.88 cm3 g−1). After polyethyleneimine (PEI) impregnation for CO2 capture, the ash derived MCM-41 samples displayed higher uptakes than the commercial sample with the maximum achievable PEI loading of 60 Wt.% PEI (dry basis) before particle agglomeration occurs, approximately 13 compared to 11 Wt.%, respectively, the latter being comparable to earlier reports in the literature. The PFA sample that displays the fastest kinetics to achieve 90% of the equilibrium uptake had the largest mesopore volume of 1.13 cm3 g−1. Given the PFA-derived MCM-41 uses a waste silicate solution for hydrothermal preparation and no prior preparation is needed, production costs are estimated to be considerable lower where silicate solutions need to be prepared by base treatment, even if ash is used, as for the RHA derived MCM-41 used here
Microwave Background Anisotropies and Nonlinear Structures I. Improved Theoretical Models
A new method is proposed for modelling spherically symmetric inhomogeneities
in the Universe. The inhomogeneities have finite size and are compensated, so
they do not exert any measurable gravitational force beyond their boundary. The
region exterior to the perturbation is represented by a
Friedmann-Robertson-Walker (FRW) Universe, which we use to study the anisotropy
in the cosmic microwave background (CMB) induced by the cluster. All
calculations are performed in a single, global coordinate system, with
nonlinear gravitational effects fully incorporated. An advantage of the gauge
choices employed here is that the resultant equations are essentially Newtonian
in form. Examination of the problem of specifying initial data shows that the
new model presented here has many advantages over `Swiss cheese' and other
models. Numerical implementation of the equations derived here is described in
a subsequent paper.Comment: 10 pages, 4 figures; Monthly Notices of the Royal Astronomical
Society (MNRAS), in pres
Microwave background anisotropies and non-linear structures II. Numerical computations
A new method for modelling spherically symmetric inhomogeneities is applied
to the formation of clusters in an expanding Universe. We impose simple initial
velocity and density perturbations of finite extent and we investigate the
subsequent evolution of the density field. Photon paths are also calculated,
allowing a detailed consideration of gravitational lensing effects and
microwave background anisotropies induced by the cluster. We apply the method
to modelling high-redshift clusters and, in particular, we consider the
reported microwave decrement observed towards the quasar pair PC1643+4631 A&B.
We also consider the effect on the primordial microwave background power
spectrum due to gravitational lensing by a population of massive high-redshift
clusters.Comment: 15 pages, 23 figures; Monthly Notices of the Royal Astronomical
Society (MNRAS), in pres
Recommended from our members
The CCL2-CCR4 axis promotes Regulatory T cell trafficking to canine glioma tissues
PurposeSpontaneously occurring glioma in pet dogs is increasingly recognized as a valuable translational model for human glioblastoma. Canine high-grade glioma and human glioblastomas share many molecular similarities, including the accumulation of immunosuppressive regulatory T cells (Tregs) that inhibit anti-tumor immune responses. Identifying in dog mechanisms responsible for Treg recruitment may afford to target the cellular population driving immunosuppression, the results providing a rationale for translational clinical studies in human patients. Our group has previously identified C-C motif chemokine 2 (CCL2) as a glioma-derived T-reg chemoattractant acting on chemokine receptor 4 (CCR4) in a murine orthotopic glioma model. Recently, we demonstrated a robust increase of CCL2 in the brain tissue of canine patients bearing high-grade glioma.MethodsWe performed a series of in vitro experiments using canine Tregs and patient-derived canine glioma cell lines (GSC 1110, GSC 0514, J3T-Bg, G06A) to interrogate the CCL2-CCR4 signaling axis in the canine.ResultsWe established a flow cytometry gating strategy for identifying and isolating FOXP3+ Tregs in dogs. The canine CD4 + CD25high T-cell population was highly enriched in FOXP3 and CCR4 expression, indicating they are bona fide Tregs. Canine Treg migration was enhanced by CCL2 or by glioma cell line-derived supernatant. Blockade of the CCL2-CCR4 axis significantly reduced migration of canine Tregs. CCL2 mRNA was expressed in all glioma cell lines, and expression increased when exposed to Tregs but not CD4 + helper T-cells.ConclusionOur study validates CCL2-CCR4 as a bi-directional Treg-glioma immunosuppressive and tumor-promoting axis in canine high-grade glioma
Generating --cosmologies with perfect fluid in dilaton gravity
We present a method for generating exact diagonal -cosmological
solutions in dilaton gravity coupled to a radiation perfect fluid and with a
cosmological potential of a special type. The method is based on the symmetry
group of the system of -field equations. Several new classes of explicit
exact inhomogeneous perfect fluid scalar-tensor cosmologies are presented.Comment: 10 pages, LaTe
- …