725 research outputs found
A new class of copulas with tail dependence and a generalized tail dependence estimator
We present a new family of copulas (generalized mean copulas) which is positive comprehensive and allows for upper tail dependence. It includes the Spearman copula and a specific Fréchet copula as special cases. Some properties and a generalized tail dependence estimator are derived. Finally, a small simulation study is conducted. --Geometric mean,arithmetic mean,copula,tail dependence
Towards a Unified Quark-Hadron Matter Equation of State for Applications in Astrophysics and Heavy-Ion Collisions
We outline an approach to a unified equation of state for quark-hadron matter
on the basis of a derivable approach to the generalized Beth-Uhlenbeck
equation of state for a cluster decomposition of thermodynamic quantities like
the density. To this end we summarize the cluster virial expansion for nuclear
matter and demonstrate the equivalence of the Green's function approach and the
derivable formulation. For an example, the formation and dissociation of
deuterons in nuclear matter is discussed. We formulate the cluster
derivable approach to quark-hadron matter which allows to take into
account the specifics of chiral symmetry restoration and deconfinement in
triggering the Mott-dissociation of hadrons. This approach unifies the
description of a strongly coupled quark-gluon plasma with that of a
medium-modified hadron resonance gas description which are contained as
limiting cases. The developed formalism shall replace the common two-phase
approach to the description of the deconfinement and chiral phase transition
that requires a phase transition construction between separately developed
equations of state for hadronic and quark matter phases. Applications to the
phenomenology of heavy-ion collisions and astrophysics are outlined.Comment: 35 pages, 3 figures, Special Issue "Compact Stars in the QCD Phase
Diagram
Measuring the temperature and heating rate of a single ion by imaging
We present a technique based on high resolution imaging to measure the
absolute temperature and the heating rate of a single ion trapped at the focus
of a deep parabolic mirror. We collect the fluorescence light scattered by the
ion during laser cooling and image it onto a camera. Accounting for the size of
the point-spread function and the magnification of the imaging system, we
determine the spatial extent of the ion, from which we infer the mean phonon
occupation number in the trap. Repeating such measurements and varying the
power or the detuning of the cooling laser, we determine the anomalous heating
rate. In contrast to other established schemes for measuring the heating rate,
one does not have to switch off the cooling but the ion is always maintained in
a state of thermal equilibrium at temperatures close to the Doppler limit
Foreword
Early Middle Cambrian bituminous coquinoid limestones from a tectonically isolated outcrop in southwestern Kyrgyzstan yield a remarkably diverse fauna, with stem-group cnidarians, trilobites, rhynchonelliformean brachiopods, and other shelly fossils. The fossil site is in the northern foothills of the Turkestan Range and thus forms part of the westernmost extension of the South Tien Shan. The fauna includes two fairly well known trilobite species, Glabrella ventrosa Lermontova, 1940 and Dorypyge richthofeniformis Lermontova, 1940, that provide confident support for an Amgan age of the rocks. New described taxa include the stem-group cnidarian Cambroctoconus kyrgyzstanicus Peel sp. nov., the trilobite Olenoides sagittatus Geyer sp. nov., and the helcionelloid Manasoconus bifrons Peel gen. et sp. nov. Additional fossils within the samples include the trilobites Olenoides sp. A, Kootenia sp., and Pseudoeteraspis? sp.; the rhynchonelliform brachiopods Narynella cf. ferganensis (Andreeva, 1962), Narynella? sp., Austrohedra? sp. nov., and two species of uncertain generic affinity; the tommotiid Tesella sp.; the hyolithelminth Hyolithellus sp.; and the palaeoscolecid Hadimopanella oezgueli Gedik, 1977. Of particular interest is Cambroctoconus kyrgyzstanicus with an octagonal corallum and a sparsely septate calyx
Diapycnal oxygen supply to the tropical North Atlantic oxygen minimum zone
The replenishment of consumed oxygen in the
open ocean oxygen minimum zone (OMZ) off northwest Africa is accomplished by oxygen transport across and along density surfaces, i.e. diapycnal and isopycnal oxygen supply.
Here the diapycnal oxygen supply is investigated using a large observational set of oxygen profiles and diapycnal mixing data from years 2008 to 2010. Diapycnal mixing is inferred from different sources: (i) a large-scale tracer release experiment, (ii) microstructure profiles, and (iii) shipboard
acoustic current measurements plus density profiles.
From these measurements, the average diapycnal diffusivity in the studied depth interval from 150 to 500m is estimated to be 1×10−5 m2 s−1, with lower and upper 95%confidence
limits of 0.8×10−5 m2 s−1 and 1.4×10−5 m2 s−1.
Diapycnal diffusivity in this depth range is predominantly caused by turbulence, and shows no significant vertical gradient.
Diapycnal mixing is found to contribute substantially to the oxygen supply of the OMZ. Within the OMZ core, 1.5 μmol kg−1 yr−1 of oxygen is supplied via diapycnal mixing,
contributing about one-third of the total demand. This oxygen which is supplied via diapycnal mixing originates from oxygen that has been laterally supplied within the upper
CentralWater layer above the OMZ, and within the Antarctic Intermediate Water layer below the OMZ. Due to the existence of a separate shallow oxygen minimum at about 100m
depth throughout most of the study area, there is no net vertical oxygen flux from the surface layer into the Central Water layer. Thus all oxygen supply of the OMZ is associated with remote pathways
Variability of turbulent mixing and diapycnal solute fluxes in the Peruvian upwelling region: First results from Meteor Cruise M92
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