1,165 research outputs found
Natural Salinity Removal Processes in Reservoirs
A small but significant amount of salinity removal has been reported by various authors to occur in mainstem Colorado River reservoirs. Recalculation of some of these salinity budgets, together with a review of the data bases used, usggests taht removal has not often been conclusively demonstrated. Laboratory microcosm experiments and field data indicate that calcium carbonate precipitation, perhaps with some coprecipitation of magnesium carbonate, is the mechanism responsible for most of the salinity removal in Oneida Reservoir, Idaho. Coprecipitation processes (including ion exchange), coagulation, and bioassimilation do not appear to be important natural salinity removal mechanisms. Finally, loss of calcium, relative to monovalent cations, may decrease water quality for irrigation purposes through increasing the sodium adsorption ratio (SAR), despite a pross decrease in the TDS. The potential role of various reservoir operation options in managing natural salinity removal processes and the value of such removal is discussed
Quantum master equations from classical Lagrangians with two stochastic forces
We show how a large family of master equations, describing quantum Brownian
motion of a harmonic oscillator with translationally invariant damping, can be
derived within a phenomenological approach, based on the assumption that an
environment can be simulated by two classical stochastic forces. This family is
determined by three time-dependent correlation functions (besides the frequency
and damping coefficients), and it includes as special cases the known master
equations, whose dissipative part is bilinear with respect to the operators of
coordinate and momentum.Comment: 10 pages, no figure
Semi-Hard Scattering Unraveled from Collective Dynamics by Two-Pion Azimuthal Correlations in 158 A GeV/c Pb + Au Collisions
Elliptic flow and two-particle azimuthal correlations of charged hadrons and
high- pions ( 1 GeV/) have been measured close to mid-rapidity in
158A GeV/ Pb+Au collisions by the CERES experiment. Elliptic flow ()
rises linearly with to a value of about 10% at 2 GeV/. Beyond
1.5 GeV/, the slope decreases considerably, possibly indicating
a saturation of at high . Two-pion azimuthal anisotropies for
1.2 GeV/ exceed the elliptic flow values by about 60% in mid-central
collisions. These non-flow contributions are attributed to near-side and
back-to-back jet-like correlations, the latter exhibiting centrality dependent
broadening.Comment: Submitted to Phys. Rev. Letters, 4 pages, 5 figure
Deformation quantization of linear dissipative systems
A simple pseudo-Hamiltonian formulation is proposed for the linear
inhomogeneous systems of ODEs. In contrast to the usual Hamiltonian mechanics,
our approach is based on the use of non-stationary Poisson brackets, i.e.
corresponding Poisson tensor is allowed to explicitly depend on time. Starting
from this pseudo-Hamiltonian formulation we develop a consistent deformation
quantization procedure involving a non-stationary star-product and an
``extended'' operator of time derivative , differentiating
the -product. As in the usual case, the -algebra of physical
observables is shown to admit an essentially unique (time dependent) trace
functional . Using these ingredients we construct a complete and
fully consistent quantum-mechanical description for any linear dynamical system
with or without dissipation. The general quantization method is exemplified by
the models of damped oscillator and radiating point charge.Comment: 14 pages, typos correcte
Classification of phase transitions and ensemble inequivalence, in systems with long range interactions
Systems with long range interactions in general are not additive, which can
lead to an inequivalence of the microcanonical and canonical ensembles. The
microcanonical ensemble may show richer behavior than the canonical one,
including negative specific heats and other non-common behaviors. We propose a
classification of microcanonical phase transitions, of their link to canonical
ones, and of the possible situations of ensemble inequivalence. We discuss
previously observed phase transitions and inequivalence in self-gravitating,
two-dimensional fluid dynamics and non-neutral plasmas. We note a number of
generic situations that have not yet been observed in such systems.Comment: 42 pages, 11 figures. Accepted in Journal of Statistical Physics.
Final versio
Lambda production in 40 A GeV/c Pb-Au collisions
During the 1999 lead run, CERES has measured hadron and electron-pair
production at 40 A GeV/c beam momentum with the spectrometer upgraded by the
addition of a radial TPC. Here the analysis of lambda and antilambda will be
presented.Comment: 8 pages, 8 figures. 6th International Conference on Strange Quarks in
Matter, Frankfurt 200
e+e--pair production in Pb-Au collisions at 158 GeV per nucleon
We present the combined results on electron-pair production in 158 GeV/n
{Pb-Au} (= 17.2 GeV) collisions taken at the CERN SPS in 1995 and
1996, and give a detailed account of the data analysis. The enhancement over
the reference of neutral meson decays amounts to a factor of 2.31 for semi-central collisions (28%
) when yields are integrated over 200 MeV/ in
invariant mass. The measured yield, its stronger-than-linear scaling with
, and the dominance of low pair strongly suggest an
interpretation as {\it thermal radiation} from pion annihilation in the
hadronic fireball. The shape of the excess centring at 500
MeV/, however, cannot be described without strong medium modifications of
the meson. The results are put into perspective by comparison to
predictions from Brown-Rho scaling governed by chiral symmetry restoration, and
from the spectral-function many-body treatment in which the approach to the
phase boundary is less explicit.Comment: 39 pages, 40 figures, to appear in Eur.Phys.J.C. (2005
Recent results from Pb-Au collisions at 158 GeV/c per nucleon obtained with the CERES spectrometer
During the 1996 lead run time, CERES has accumulated 42 million events,
corresponding to a factor of 5 more statistics than in 1995 and 2.5 million
events of a special photon-run. We report on the results of the low-mass
ee-pair analysis. Since the most critical item is the poor
signal-to-background ratio we also discuss the understanding of this
background, in absolute terms, with the help of a detailed Monte Carlo
simulation. We show preliminary results of the photon analysis and summarize
the results of the hadron analysis preliminarily reported on already at QM'97Comment: 10 pages, 9 figures, Proceedings of the XIV Int. Conf. on
Nucleus-Nucleus Collisions,Quark Matter 99, Torino, Italy, May 10 - 15, 199
Evaluating ‘enhancing pragmatic language skills for young children with social communication impairments’ (E-PLAYS): protocol for a feasibility randomised controlled trial study
Background: A number of children experience difficulties with social communication and this has long-term deleterious effects on their mental health, social development and education. The proposal presented in this article describes a feasibility study for a trial to test an intervention (‘E-PLAYS’) aimed at supporting children with social communication impairments. E-PLAYS harnesses technology in the form of a novel computer game in order to develop collaborative and communication skills. Preliminary studies by the authors show that when E-PLAYS was administered by the research team, children with social communication impairments showed improvements on communication test scores and on observed collaborative behaviours. The study described here is a pragmatic trial to test the application of E-PLAYS delivered by NHS speech and language therapists together with schools.
Methods: This protocol outlines a two-arm feasibility cluster-randomised controlled trial of the E-PLAYS intervention with treatment as usual control arm, with randomisation at the level of the speech and language therapist. The aim of this study is to ascertain whether it will be feasible to progress to running a full-scale definitive trial to test the effectiveness of E-PLAYS in an NHS setting. Data relating to recruitment and retention, the appropriateness of outcomes and the acceptability of E-PLAYS to participants will be collected.
Speech and language therapists will select suitable children (ages 4–7 years old) from their caseloads and deliver either the E-PLAYS intervention (experimental group) or treatment as usual (control group). Assessments will include blinded language measures and observations, non-blinded teacher-reported measures of peer relations and classroom behaviour and parent-reported use of resources and quality of life. There will also be a qualitative process evaluation.
Discussion: The findings of this study will inform the decision as to whether to progress to a full-scale definitive randomised controlled trial to test the effectiveness of E-PLAYS when delivered by speech and language therapists and teaching assistants within schools. The use of technology in game form is a novel approach in an area where there are currently few available interventions
Flow and non-flow event anisotropies at the SPS
A study of differential elliptic event anisotropies (v_2) of charged
particles and high-pt pions in 158 AGeV/c Pb+Au collisions is presented.
Results from correlations with respect to the event plane and from two-particle
azimuthal correlations are compared. The latter give systematically higher v_2
values at pt>1.2GeV/c providing possibly an evidence of a non-flow semihard
component.Comment: 4 pages, 6 figures, Quark Matter 2002, Nantes, to appear in Nucl.
Phys.
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