174 research outputs found
Interannual variability of winter precipitation in the European Alps: relations with the North Atlantic Oscillation.
Abstract. The European Alps rely on winter precipitation for various needs in terms of hydropower and other water uses. Major European rivers originate from the Alps and depend on winter precipitation and the consequent spring snow melt for their summer base flows. Understanding the fluctuations in winter rainfall in this region is crucially important to the study of changes in hydrologic regime in river basins, as well as to the management of their water resources. Despite the recognized relevance of winter precipitation to the water resources of the Alps and surrounding regions, the magnitude and mechanistic explanation of interannual precipitation variability in the Alpine region remains unclear and poorly investigated. Here we use gridded precipitation data from the CRU TS 1.2 to study the interannual variability of winter alpine precipitation. We found that the Alps are the region with the highest interannual variability in winter precipitation in Europe. This variability cannot be explained by large scale climate patterns such as the Arctic Oscillation (AO), North Atlantic Oscillation (NAO) or the East Atlantic/West Russia (EA/WR), even though regions below and above the Alps demonstrate connections with these patterns. Significant trends were detected only in small regions located in the Eastern part of the Alps
The assembly of massive galaxies from NIR observations of the Hubble Deep Field South
We use a deep K(AB)<25 galaxy sample in the Hubble Deep Field South to trace
the evolution of the cosmological stellar mass density from z~ 0.5 to z~3. We
find clear evidence for a decrease of the average stellar mass density at high
redshift, 2<z<3.2, that is 15^{+25}_{-5}% of the local value, two times higher
than what observed in the Hubble Deep Field North. To take into account for the
selection effects, we define a homogeneous subsample of galaxies with
10^{10}M_\odot \leq M_* \leq 10^{11}M_\odot: in this sample, the mass density
at z>2 is 20^{+20}_{-5} % of the local value. In the mass--limited subsample at
z>2, the fraction of passively fading galaxies is at most 25%, although they
can contribute up to about 40% of the stellar mass density. On the other hand,
star--forming galaxies at z>2 form stars with an average specific rate at least
~4 x10^{-10} yr, 3 times higher than the z<~1 value. This
implies that UV bright star--forming galaxies are substancial contributors to
the rise of the stellar mass density with cosmic time. Although these results
are globally consistent with --CDM scenarios, the present rendition of
semi analytic models fails to match the stellar mass density produced by more
massive galaxies present at z>2.Comment: Accepted for publication on ApJLetter
Strongly star-forming rotating disks in a complex merging system at z = 4,7 as revealed by ALMA
We performed a kinematical analysis of the [CII] line emission of the BR
1202-0725 system at z~4,7 using ALMA observations. The most prominent sources
of this system are a quasar and a submillimeter galaxy, separated by a
projected distance of about 24 kpc and characterized by very high SFR, higher
than 1000 Msun/yr. However, the ALMA observations reveal that these galaxies
apparently have undisturbed rotating disks, which is at variance with the
commonly accepted scenario in which strong star formation activity is induced
by a major merger. We also detected faint components which, after spectral
deblending, were spatially resolved from the main QSO and SMG emissions. The
relative velocities and positions of these components are compatible with
orbital motions within the gravitational potentials generated by the QSO host
galaxy and the SMG, suggesting that they are smaller galaxies in interaction or
gas clouds in accretion flows of tidal streams. We did not find any clear
spectral evidence for outflows caused by AGN or stellar feedback. This suggests
that the high star formation rates might be induced by interactions or minor
mergers with these companions, which do not affect the large-scale kinematics
of the disks, however. Our kinematical analysis also indicates that the QSO and
the SMG have similar Mdyn, mostly in the form of molecular gas, and that the
QSO host galaxy and the SMG are seen close to face-on with slightly different
disk inclinations: the QSO host galaxy is seen almost face-on (i~15), while the
SMG is seen at higher inclinations (i~25). Finally, the ratio between the black
hole mass of the QSO, obtained from XShooter spectroscopy, and the Mdyn of the
host galaxy is similar to value found in very massive local galaxies,
suggesting that the evolution of black hole galaxy relations is probably better
studied with dynamical than with stellar host galaxy masses.Comment: Accepted for publication in Astronomy and Astrophysic
The evolution of the galaxy luminosity function in the rest frame blue band up to z=3.5
We present an estimate of the cosmological evolution of the field galaxy
luminosity function (LF) in the rest frame 4400 Angstrom B -band up to redshift
z=3.5. To this purpose, we use a composite sample of 1541 I--selected galaxies
selected down to I_(AB)=27.2 and 138 galaxies selected down to K_(AB)=25 from
ground-based and HST multicolor surveys, most notably the new deep JHK images
in the Hubble Deep Field South (HDF-S) taken with the ISAAC instrument at the
ESO-VLT telescope. About 21% of the sample has spectroscopic redshifts, and the
remaining fraction well calibrated photometric redshifts. The resulting blue LF
shows little density evolution at the faint end with respect to the local
values, while at the bright end (M_B(AB)<-20) a brightening increasing with
redshift is apparent with respect to the local LF. Hierarchical CDM models
overpredict the number of faint galaxies by about a factor 3 at z=1. At the
bright end the predicted LFs are in reasonable agreement only at low and
intermediate redshifts (z=1), but fail to reproduce the pronounced brightening
observed in the high redshift (z=2-3) LF. This brightening could mark the epoch
where a major star formation activity is present in the galaxy evolution.Comment: 14 pages, 2 figures, Astrophysical Journal Letters, in pres
A study of the nuclear medium influence on transverse momentum of hadrons produced in deep inelastic neutrino scattering
The influence of nuclear effects on the transverse momentum
distributions of neutrinoproduced hadrons is investigated using the data
obtained with SKAT propane-freon bubble chamber irradiated in the neutrino beam
(with = 3-30 GeV) at Serpukhov accelerator. Dependences of of hadrons (more pronounced for the
positively charged ones) produced in the target fragmentation region at low
invariant mass of the hadronic system (2 4 GeV) or at low energies
transferred to the current quark (2 GeV). At higher or ,
no influence of nuclear effects on is observed. Measurement results
are compared with predictions of a simple model, incorporating secondary
intranuclear interactions of hadrons (with a formation length extracted from
the Lund fragmentation model), which qualitatively reproduces the main features
of the data.Comment: 23 pages, 7 figure
BR1202-0725: An Extreme Multiple Merger at z = 4.7
The radio-quiet quasar BR1202-0725 (z=4.695) is a remarkable source with a
bright Northwest (NW) companion detected at submm and radio wavelengths but
invisible in the optical. In the absence of amplification by gravitational
lensing, BR1202-0725 would be the most luminous binary CO and FIR source in the
Universe. In this paper, we report observations with the IRAM Plateau de Bure
interferometer of BR1202-0725 in the redshifted emission of the CO(5-4) and
(7-6) lines, the [C I](3P2-3P1) line, a high angular resolution (0.3 x 0.8
arcsec) 1.3 mm map of the rest-frame, far-IR dust continuum, and a search for
the CO(11-10) line. We compare these results with recent ALMA data in the [C
II] line. Both the quasar host galaxy and its NW companion are spatially
resolved in the molecular line emission and the dust continuum. The CO profile
of the NW companion is very broad with a full width at half maximum of 1000 +/-
130 km/s, compared to 360 +/- 40 km/s for the quasar host galaxy to the
Southeast (SE). The difference in linewidths and center velocities, and the
absence of any lens candidate or arc-like structure in the field, at any
wavelength, show that the obscured NW galaxy and the SE quasar host galaxy
cannot be lensed images of the same object. Instead, we find morphological and
kinematic evidence for sub-structures in both the NW and SE sources. We
interpret these results as strong indications that the BR1202-0725 complex is a
group of young, interacting, and highly active starburst galaxies.Comment: Minor changes to agree with published versio
Space-time Structure of Initial Parton Production in Ultrarelativistic Heavy Ion Collisions
The space and time evolution of initial parton production in
ultrarelativistic heavy ion collisions is investigated within the framework of
perturbative QCD which includes both initial and final state radiations.
Uncertainty principle is used to relate the life time of a radiating parton to
its virtuality and momentum. The interaction time of each hard or semihard
parton scattering is also taken into account. For central collisions at
GeV, most of the partons are found to be produced within 0.5
fm/c after the total overlap of the two colliding nuclei. The local momentum
distribution is approximately isotropical at that time. The implication on how
to treat correctly the the secondary scattering in an ultimate parton cascading
model is also discussed.Comment: 19 pages in REVTEX with 12 figures in separate uuencoded postscript
files, LBL-3415
Isoscalar resonances with J^{PC}=1^{--} in e^+e^-annihilation
The analysis of the vector isoscalar excitations in the energy range between
1 and 2 GeV of the annihilation is presented for the final states
, , , and
. The effects of both the resonance mixing and the
successive opening of multiparticle channels, with the energy dependent partial
widths, are taken into account. The work extends our previous analysis
hep-ph/9609216 of the vector isovector excitations and is aimed to compare the
existing data with the predictions of the model. It is shown that
this hypothesis does not contradict the data.Comment: 16 pages, revtex, 6 ps figures. Clarifying remarks, a table, and
references are added. Accepted in Phys. Rev.
What research agenda could be generated from the European General Practice Research Network concept of Multimorbidity in Family Practice?
This is the final version of the article. Available from the publisher via the DOI in this record.BACKGROUND: Multimorbidity is an intuitively appealing, yet challenging, concept for Family Medicine (FM). An EGPRN working group has published a comprehensive definition of the concept based on a systematic review of the literature which is closely linked to patient complexity and to the biopsychosocial model. This concept was identified by European Family Physicians (FPs) throughout Europe using 13 qualitative surveys. To further our understanding of the issues around multimorbidity, we needed to do innovative research to clarify this concept. The research question for this survey was: what research agenda could be generated for Family Medicine from the EGPRN concept of Multimorbidity? METHODS: Nominal group design with a purposive panel of experts in the field of multimorbidity. The nominal group worked through four phases: ideas generation phase, ideas recording phase, evaluation and analysis phase and a prioritization phase. RESULTS: Fifteen international experts participated. A research agenda was established, featuring 6 topics and 11 themes with their corresponding study designs. The highest priorities were given to the following topics: measuring multimorbidity and the impact of multimorbidity. In addition the experts stressed that the concept should be simplified. This would be best achieved by working in reverse: starting with the outcomes and working back to find the useful variables within the concept. CONCLUSION: The highest priority for future research on multimorbidity should be given to measuring multimorbidity and to simplifying the EGPRN model, using a pragmatic approach to determine the useful variables within the concept from its outcomes.The study had a Grant of 8000 Euros from the EGPRN
Determination of alphaS from Hadronic Event Shapes in e+e- Annihilation at 192 < sqrt(s) < 208 GeV
Results are presented from a study of the structure of high energy hadronic
events recorded by the L3 detector at sqrt(s)>192 GeV. The distributions of
several event shape variables are compared to resummed O(alphaS^2) QCD
calculations. We determine the strong coupling constant at three average
centre-of-mass energies: 194.4, 200.2 and 206.2 GeV. These measurements,
combined with previous L3 measurements at lower energies, demonstrate the
running of alphaS as expected in QCD and yield alphaS(mZ) = 0.1227 +- 0.0012 +-
0.0058, where the first uncertainty is experimental and the second is
theoretical
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