140 research outputs found
About the determination of critical exponents related to possible phase transitions in nuclear fragmentation
We introduce a method based on the finite size scaling assumption which
allows to determine numerically the critical point and critical exponents
related to observables in an infinite system starting from the knowledge of the
observables in finite systems. We apply the method to bond percolation in 2
dimensions and compare the results obtained when the bond probability p or the
fragment multiplicity m are chosen as the relevant parameter.Comment: 12 pages, TeX, 4 figure
Early onset pauciarticular arthritis is the major risk factor for naproxen-induced pseudoporphyria in juvenile idiopathic arthritis
Pseudoporphyria (PP) is characterized by skin fragility, blistering and scarring in sun-exposed skin areas without abnormalities in porphyrin metabolism. The phenylpropionic acid derivative group of nonsteroidal anti-inflammatory drugs, especially naproxen, is known to cause PP. Naproxen is currently one of the most prescribed drugs in the therapy of juvenile idiopathic arthritis (JIA). The prevalence of PP was determined in a 9-year retrospective study of children with JIA and associated diseases. In addition, we prospectively studied the incidence of PP in 196 patients (127 girls and 69 boys) with JIA and associated diseases treated with naproxen from July 2001 to March 2002. We compared these data with those from a matched control group with JIA and associated diseases not treated with naproxen in order to identify risk factors for development of PP. The incidence of PP in the group of children taking naproxen was 11.4%. PP was particularly frequent in children with the early-onset pauciarticular subtype of JIA (mean age 4.5 years). PP was associated with signs of disease activity, such as reduced haemoglobin (<11.75 g/dl), and increased leucocyte counts (>10,400/μl) and erythocyte sedimentation rate (>26 mm/hour). Comedications, especially chloroquine intake, appeared to be additional risk factors. The mean duration of naproxen therapy before the onset of PP was 18.1 months, and most children with PP developed their lesions within the first 2 years of naproxen treatment. JIA disease activity seems to be a confounding factor for PP. In particular, patients with early-onset pauciarticular JIA patients who have significant inflammation appear to be prone to developing PP upon treatment with naproxen
Breakup Conditions of Projectile Spectators from Dynamical Observables
Momenta and masses of heavy projectile fragments (Z >= 8), produced in
collisions of 197Au with C, Al, Cu and Pb targets at E/A = 600 MeV, were
determined with the ALADIN magnetic spectrometer at SIS. An analysis of
kinematic correlations between the two and three heaviest projectile fragments
in their rest frame was performed. The sensitivity of these correlations to the
conditions at breakup was verified within the schematic SOS-model. The data
were compared to calculations with statistical multifragmentation models and to
classical three-body calculations. Classical trajectory calculations reproduce
the dynamical observables. The deduced breakup parameters, however, differ
considerably from those assumed in the statistical multifragmentation models
which describe the charge correlations. If, on the other hand, the analysis of
kinematic and charge correlations is performed for events with two and three
heavy fragments produced by statistical multifragmentation codes, a good
agreement with the data is found with the exception that the fluctuation widths
of the intrinsic fragment energies are significantly underestimated. A new
version of the multifragmentation code MCFRAG was therefore used to investigate
the potential role of angular momentum at the breakup stage. If a mean angular
momentum of 0.75/nucleon is added to the system, the energy fluctuations
can be reproduced, but at the same time the charge partitions are modified and
deviate from the data.
PACS numbers: 25.70.Mn, 25.70.Pq, 25.75.Ld, 25.75.-qComment: 38 pages, RevTeX with 21 included figures; Also available from
http://www-kp3.gsi.de/www/kp3/aladin_publications.htm
Record high solar irradiance in Western Europe during first COVID-19 lockdown largely due to unusual weather
Spring 2020 broke sunshine duration records across western Europe. The
Netherlands recorded the highest surface irradiance since 1928, exceeding the
previous extreme of 2011 by 13 %, and the diffuse fraction of the irradiance
measured a record low percentage (38 %). The coinciding irradiance extreme and
a reduction in anthropogenic pollution due to COVID-19 measures triggered the
hypothesis that cleaner-than-usual air contributed to the record. Based on
analyses of ground-based and satellite observations and experiments with a
radiative transfer model, we estimate a 1.3 % (2.3 W m) increase in
surface irradiance with respect to the 2010-2019 mean due to a low median
aerosol optical depth, and a 17.6 % (30.7 W m) increase due to several
exceptionally dry days and a very low cloud fraction overall. Our analyses show
that the reduced aerosols and contrails due to the COVID-19 measures are far
less important in the irradiance record than the dry and particularly
cloud-free weather.Comment: 21 pages, 12 figures, submitted to Communications Earth and
Environmen
Pion radii in nonlocal chiral quark model
The electromagnetic radius of the charged pion and the transition radius of
the neutral pion are calculated in the framework of the nonlocal chiral quark
model. It is shown in this model that the contributions of vector mesons to the
pion radii are noticeably suppressed in comparison with a similar contribution
in the local Nambu--Jona-Lasinio model. The form-factor for the process
gamma*pi+pi- is calculated for the -1 GeV^2<q^2<1.6 GeV^2. Our results are in
satisfactory agreement with experimental data.Comment: 7 pages, 7 figure
Multiplicity correlations of intermediate-mass fragments with pions and fast protons in 12C + 197Au
Low-energy pi+ (E < 35 MeV) from 12C+197Au collisions at incident energies
from 300 to 1800 MeV per nucleon were detected with the Si-Si(Li)-CsI(Tl)
calibration telescopes of the INDRA multidetector. The inclusive angular
distributions are approximately isotropic, consistent with multiple
rescattering in the target spectator. The multiplicity correlations of the
low-energy pions and of energetic protons (E > 150 MeV) with intermediate-mass
fragments were determined from the measured coincidence data. The deduced
correlation functions 1 + R \approx 1.3 for inclusive event samples reflect the
strong correlations evident from the common impact-parameter dependence of the
considered multiplicities. For narrow impact-parameter bins (based on
charged-particle multiplicity), the correlation functions are close to unity
and do not indicate strong additional correlations. Only for pions at high
particle multiplicities (central collisions) a weak anticorrelation is
observed, probably due to a limited competition between these emissions.
Overall, the results are consistent with the equilibrium assumption made in
statistical multifragmentation scenarios. Predictions obtained with
intranuclear cascade models coupled to the Statistical Multifragmentation Model
are in good agreement with the experimental data.Comment: 9 pages, 11 figures, subm. to EPJ
Specificity protein 2 (Sp2) is essential for mouse development and autonomous proliferation of mouse embryonic fibroblasts
Background: The zinc finger protein Sp2 (specificity protein 2) is a member of the glutamine-rich Sp family of transcription factors. Despite its close similarity to Sp1, Sp3 and Sp4, Sp2 does not bind to DNA or activate transcription when expressed in mammalian cell lines. The expression pattern and the biological relevance of Sp2 in the mouse are unknown. Methodology/Principal Findings: Whole-mount in situ hybridization of mouse embryos between E7.5 and E9.5 revealed abundant expression in most embryonic and extra-embryonic tissues. In order to unravel the biological relevance of Sp2, we have targeted the Sp2 gene by a tri-loxP strategy. Constitutive Sp2null and conditional Sp2cko knockout alleles were obtained by crossings with appropriate Cre recombinase expressing mice. Constitutive disruption of the mouse Sp2 gene (Sp2null) resulted in severe growth retardation and lethality before E9.5. Mouse embryonic fibroblasts (MEFs) derived from Sp2null embryos at E9.5 failed to grow. Cre-mediated ablation of Sp2 in Sp2cko/cko MEFs obtained from E13.5 strongly impaired cell proliferation. Conclusions/Significance: Our results demonstrate that Sp2 is essential for early mouse development and autonomous proliferation of MEFs in culture. Comparison of the Sp2 knockout phenotype with th
Isotopic Dependence of the Nuclear Caloric Curve
The A/Z dependence of projectile fragmentation at relativistic energies has
been studied with the ALADIN forward spectrometer at SIS. A stable beam of
124Sn and radioactive beams of 124La and 107Sn at 600 MeV per nucleon have been
used in order to explore a wide range of isotopic compositions. Chemical
freeze-out temperatures are found to be nearly invariant with respect to the
A/Z of the produced spectator sources, consistent with predictions for expanded
systems. Small Coulomb effects (\Delta T \approx 0.6 MeV) appear for residue
production near the onset of multifragmentation.Comment: 11 pages, 3 figures, accepted for publ. in Phys. Rev. Let
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