Linear maps on the space of all bounded observables preserving maximal deviation

In this paper we determine all the bijective linear maps on the space of bounded observables which preserve a fixed moment or the variance. Nonlinear versions of the corresponding results are also presented.Comment: 27 pages. To appear in J. Funct. Ana

The fate of the Mach cone in covariant transport theory

An intriguing potential signature of hydrodynamic behavior in relativistic A+A reactions at Relativistic Heavy Ion Collider (RHIC) energies is conical flow induced by fast supersonic particles traversing the hot and dense medium. Here I present first results on the evolution of Mach shocks in 2->2 covariant transport theory, in a static uniform medium.Comment: Presentation at CIPANP 2009 (Tenth Conference on the Intersections of Particle and Nuclear Physics), May 26-31, 2009, Torrey Pines, California, US

Freeze out in narrow and wide layers

The freeze out of particles from a layer of finite thickness is discussed in a phenomenological kinetic model. The proposed model, based on the Modified Boltzman Transport Equation, is Lorentz invariant and can be applied equally well for the freeze out layers with space-like and time-like normal vectors. It leads to non-equilibrated post freeze out distributions. The dependence of the resulting distribution on the thickness of the layer is presented and discussed for a space-like freeze out scenario.Comment: Minor corrections to improve the presentation. 4 pages, 2 figures, to appear in the Proceedings of "Quark Matter 2005", August 4-9, 2005, Budapest, Hungar

Covariant kinetic freeze out description through a finite space-time layer

We develop and analyze a covariant FO probability valid for a finite space-time layer.Comment: Proceedings of "Quark Matter 2005", 4 pages, 3 figures, with correction

THE WETTABILITY OF A DNAPL/SURFACTANT SOLUTION ON QUARTZ AND IRON OXIDE SURFACES

DNAPLs in the subsurface may contain surface-active compounds that impact DNAPL migration and distribution. A number of studies to-date have focused on the role surface active compounds play in altering the wettability of quartz sands without examining the implications for other minerals commonly present in the subsurface. This study aims to extend the understanding of DNAPL/surfactant wettability to iron oxide surfaces. Specifically the objective was to compare the changes in the wettability of quartz and iron oxide sands in a tetrachloroethylene/water system containing a representative organic base. Wettability was assessed through: contact angles; Pc-S curves; and a two- dimensional flow cell experiment. It was discovered that quartz and iron oxide surfaces may exhibit different wetting characteristics under similar subsurface conditions. At neutral pH the quartz was strongly NAPL-wetting while the iron oxide remained hydrophilic. This study concludes that the isoelectric point, the pH at which there is a net zero surface charge, plays a major role in governing cationic surfactant sorption

Jet-like correlations between Forward- and Mid- rapidity in p+p, d+Au and Au+Au collisions from STAR at 200 GeV

In this proceedings we present STAR measurements of two particle azimuthal correlations between trigger particles at mid-rapidity ($|\eta|<$ 1) and associated particles at forward rapidities (2.7 $<|\eta|<$ 3.9) in p+p, d+Au and Au+Au collisions at $\sqrt{s_{NN}}$= 200 GeV. Two particle azimuthal correlations between a mid-rapidity trigger particle and forward-rapidity associated particles preferably probe large-x quarks scattered off small-x gluons in RHIC collisions. Comparison of the separate d- and Au-side measurements in d+Au collisions may potentially probe gluon saturation and the presence of Color Glass Condensate. In Au+Au collisions quark energy loss can be probed at large rapidities, which may be different from gluon energy loss measured at mid-rapidity.Comment: Quark Matter 06 Conference proceedings, submitted to Journal of Phys.

Multimode pulsation of the ZZ Ceti star GD 154

We present the results of a comparative period search on different time-scales and modelling of the ZZ Ceti (DAV) star GD 154. We determined six frequencies as normal modes and four rotational doublets around the ones having the largest amplitude. Two normal modes at 807.62 and 861.56 microHz have never been reported before. A rigorous test revealed remarkable intrinsic amplitude variability of frequencies at 839.14 and 861.56 microHz over a 50 d time-scale. In addition, the multimode pulsation changed to monoperiodic pulsation with an 843.15 microHz dominant frequency at the end of the observing run. The 2.76 microHz average rotational split detected led to a determination of a 2.1 d rotational period for GD 154. We searched for model solutions with effective temperatures and log g close to the spectroscopically determined ones. The best-fitting models resulting from the grid search have M_H between 6.3 x 10^-5 and 6.3 x 10^-7 M*, which means thicker hydrogen layer than the previous studies suggested. Our investigations show that mode trapping does not necessarily operate in all of the observed modes and the best candidate for a trapped mode is at 2484 microHz.Comment: 11 pages, 11 figures, accepted for publication in MNRA

Silver Nanoparticle Transport Through Soil: Illuminating the Governing Pore-Scale Processes

Engineered nanoparticles are widely used and will eventually be released to the subsurface environment and contaminate groundwater resources. However, the transport of engineered nanoparticles through soil is currently not well understood and cannot be modelled in any fundamental manner, placing groundwater resources at risk from nanoparticle contamination. This inability to accurately simulate transport is due to a lack of experimental information on nanoparticle interactions in the pore spaces of real soils. This thesis illuminates the pore-scale processes governing silver nanoparticle transport through soil. In addition, it examines the influence of surface chemistry and grain/pore distributions on those processes. For the first study, a method was developed and validated which employs Synchrotron X-ray Computed Microtomography (SXCMT) to experimentally quantify changing concentrations of silver nanoparticles, both spatially and temporally, within real soil pore spaces during transport. For the second study, the SXCMT imaging method was employed to experimentally investigate the role of pore-scale processes on silver nanoparticle transport through different soils representing different surface chemistries and grain distributions. The experiments found that nanoparticle transport and retention is significantly impacted by small regions of low fluid velocity near grain-grain contacts (termed ‘immobile zones’). For the third study, the experimental SXCMT datasets from the second study were coupled with Computational Fluid Dynamics to estimate the pore-scale nanoparticle mass flux and flow rates. The estimated distributions of mass flux and flow rates suggested that the current approach to modelling nanoparticle retention was incapable of considering mass flow in the centers of soil pores, rendering it unable to accurately predict the rate at which nanoparticles will be retained by soil. Overall, this thesis presents the first experimental datasets of pore-scale nanoparticle concentrations during transport. These previously unobtainable datasets provided the first direct confirmation of ‘immobile zones’ and their contribution to anomalous nanoparticle transport behaviour. In addition, they provided some of the first evidence as to why current modelling approaches are unable to predict nanoparticle retention rates