1,097 research outputs found
Conservation paleobiology as a tool to define reference conditions in naturally stressed transitional settings: Micropaleontological insights from the holocene of the po coastal plain (italy)
The key role of paralic environments as providers of ecosystem services, associated with their increasingly threatened state, led to the definition of international water management policies aimed to improve ecological quality status (EcoQs). Restoration actions rely on the definition of reference conditions, which is a particularly challenging task in naturally stressed transitional environments. In the present work, we apply the diversity index Exp(H\u2019bc ) on benthic foraminifer assemblages from two anthropogenically unimpacted transitional to coastal Holocene sediment successions of the Po coastal plain, in order to assess past EcoQs (PaleoEcoQs). Ostracod ecological groups provided detailed insights on naturally stressful paleoenvironmental conditions. We show that \u201cpoor\u201d to \u201cmoderate\u201d PaleoEcoQs are recorded by biological indicators at reference conditions under fluctuations of chemical-physical parameters and organic matter enrichment. We emphasize the importance of a site-specific paleobiological approach, as significant differences in diversity occur even on a short spatial scale. This study illustrates that early to mid-Holocene sediment successions resulted to be appropriate for conservation paleobiological purposes, providing a high-resolution paleoecological record under the influence of the Holocene sea-level rise in analogy with the present-day global change
Kaon mass in dense matter
The variation of kaon mass in dense, charge-neutral baryonic matter at
beta-equilibrium has been investigated. The baryon interaction has been
included by means of nonlinear Walecka model, with and without hyperons and the
interaction of kaons with the baryons has been incorporated through the
Nelson-Kaplan model. A self-consistant, one-loop level calculation has been
carried out. We find that at the mean field level, the presence of the hyperons
makes the density-dependence of the kaon mass softer. Thus, the kaon
condensation threshold is pushed up in the baryon density. The loop diagrams
tend to lower the kaon condensation point for lower values of . We
also find that the S-wave kaon-nucleon interaction plays the dominant role in
determining the on-set of kaon condensation and the contribution of the P-wave
interaction is insignificant.Comment: Four figures available on reques
Strangeness Production in Neutron Stars
Production of strange quarks in neutron stars is investigated in this work.
Three cases, one in which the energy and neutrinos produced in the strangeness
production reactions are retained in the reaction region, second in which the
neutrinos are allowed to escape the reaction region but the energy is retained
and the third in which both the energy and neutrinos escape the reaction region
are considered. It is shown that the nonleptonic weak process dominates strange
quark production while semileptonic weak processes, which produce neutrinos,
lead to the cooling if the neutrinos escape the reaction region. It is found
that the time required for the saturation of the strangeness fraction is
between and sec, with the shorter time corresponding to the
first two cases. About 0.2 neutrinos/baryon are emitted during the process in
the first two cases where as the neutrino emission is somewhat suppressed in
the last case. The average energy of the neutrinos produced in all the three
cases is found to be several hundred . We also find that a large amount of
energy is released during the strangeness production in the first two cases and
this leads to the heating of the reaction region. Implications of the neutrino
production are investigated.Comment: Latex file. 3 figures available from SKG on request. accepted in Nucl
Phys
A Honeycomb Proportional Counter for Photon Multiplicity Measurement in the ALICE Experiment
A honeycomb detector consisting of a matrix of 96 closely packed hexagonal
cells, each working as a proportional counter with a wire readout, was
fabricated and tested at the CERN PS. The cell depth and the radial dimensions
of the cell were small, in the range of 5-10 mm. The appropriate cell design
was arrived at using GARFIELD simulations. Two geometries are described
illustrating the effect of field shaping. The charged particle detection
efficiency and the preshower characteristics have been studied using pion and
electron beams. Average charged particle detection efficiency was found to be
98%, which is almost uniform within the cell volume and also within the array.
The preshower data show that the transverse size of the shower is in close
agreement with the results of simulations for a range of energies and converter
thicknesses.Comment: To be published in NIM
leap ucd 2017 centrifuge tests at cambridge
As part of the LEAP project the seismic response of a liquefiable 5° slope was modelled at a number of centrifuges around the world. In this paper the two experiments conducted at Cambridge University are discussed. The model preparation is detailed with particular emphasis on the sand pouring, saturation and slope cutting process. The presence of the third harmonic in the input motion is shown and its significance discussed. The potential for wavelet denoising to filter random electrical noise from the pore pressure traces is illustrated. CPT strength profiles are highlighted and a possible softer layer in one of the tests is discussed. Whilst the specifications called for one dense and one loose test, the likelihood that both Cambridge tests were loosely poured is assessed. The PIV technique is used to obtain the displacements of the slope during the test. Finally, the correspondence between the PIV displacements and physical measurements of the marker movements is compared
Pion Freeze-Out Time in Pb+Pb Collisions at 158 A GeV/c Studied via pi-/pi+ and K-/K+ Ratios
The effect of the final state Coulomb interaction on particles produced in
Pb+Pb collisions at 158 A GeV/c has been investigated in the WA98 experiment
through the study of the pi-/pi+ and K-/K+ ratios measured as a function of
transverse mass. While the ratio for kaons shows no significant transverse mass
dependence, the pi-/pi+ ratio is enhanced at small transverse mass values with
an enhancement that increases with centrality. A silicon pad detector located
near the target is used to estimate the contribution of hyperon decays to the
pi-/pi+ ratio. The comparison of results with predictions of the RQMD model in
which the Coulomb interaction has been incorporated allows to place constraints
on the time of the pion freeze-out.Comment: 9 pages, 12 figure
Heavy Quarks and Heavy Quarkonia as Tests of Thermalization
We present here a brief summary of new results on heavy quarks and heavy
quarkonia from the PHENIX experiment as presented at the "Quark Gluon Plasma
Thermalization" Workshop in Vienna, Austria in August 2005, directly following
the International Quark Matter Conference in Hungary.Comment: 8 pages, 5 figures, Quark Gluon Plasma Thermalization Workshop
(Vienna August 2005) Proceeding
Proximity effect at superconducting Sn-Bi2Se3 interface
We have investigated the conductance spectra of Sn-Bi2Se3 interface junctions
down to 250 mK and in different magnetic fields. A number of conductance
anomalies were observed below the superconducting transition temperature of Sn,
including a small gap different from that of Sn, and a zero-bias conductance
peak growing up at lower temperatures. We discussed the possible origins of the
smaller gap and the zero-bias conductance peak. These phenomena support that a
proximity-effect-induced chiral superconducting phase is formed at the
interface between the superconducting Sn and the strong spin-orbit coupling
material Bi2Se3.Comment: 7 pages, 8 figure
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