3,103 research outputs found
T-violation in decay in a general two-Higgs doublet model
We calculate the transverse muon polarization in the process
arising from the Yukawa couplings of charged Higgs boson in a general two-Higgs
doublet model where spontaneous violation of CP is presentComment: 6 pages, latex, accepted for publication in Phys. Rev.
PIXE and ToF-SIMS analysis of streaker samplers filters
This paper presents methodological innovations introduced in the characterisation of urban aerosol collected in Italy in a recent campaign. Two complementary ion beam analysis (IBA) techniques were used to analyse Nuclepore filters used in continuous streaker samplers to collect airborne particles in four Italian towns. Na to Pb elemental concentrations were obtained by particle induced X-ray emission (PIXE), while time of flight secondary ion mass spectrometry (ToF-SIMS) produced, on the same samples, time trends for several elements and molecular fragments. In addition, light attenuation measurements were used as a tracer for black carbon. The data produced by these three techniques was merged into a unique data set to address the characterisation of particulate matter sources. Correlations between elemental concentration trends (PIXE) and relative trends for molecular fragments (ToF-SIMS) and black carbon (light attenuation) have been studied by cluster and principal component analysis
The faster the narrower: characteristic bulk velocities and jet opening angles of Gamma Ray Bursts
The jet opening angle theta_jet and the bulk Lorentz factor Gamma_0 are
crucial parameters for the computation of the energetics of Gamma Ray Bursts
(GRBs). From the ~30 GRBs with measured theta_jet or Gamma_0 it is known that:
(i) the real energetic E_gamma, obtained by correcting the isotropic equivalent
energy E_iso for the collimation factor ~theta_jet^2, is clustered around
10^50-10^51 erg and it is correlated with the peak energy E_p of the prompt
emission and (ii) the comoving frame E'_p and E'_gamma are clustered around
typical values. Current estimates of Gamma_0 and theta_jet are based on
incomplete data samples and their observed distributions could be subject to
biases. Through a population synthesis code we investigate whether different
assumed intrinsic distributions of Gamma_0 and theta_jet can reproduce a set of
observational constraints. Assuming that all bursts have the same E'_p and
E'_gamma in the comoving frame, we find that Gamma_0 and theta_jet cannot be
distributed as single power-laws. The best agreement between our simulation and
the available data is obtained assuming (a) log-normal distributions for
theta_jet and Gamma_0 and (b) an intrinsic relation between the peak values of
their distributions, i.e theta_jet^2.5*Gamma_0=const. On average, larger values
of Gamma_0 (i.e. the "faster" bursts) correspond to smaller values of theta_jet
(i.e. the "narrower"). We predict that ~6% of the bursts that point to us
should not show any jet break in their afterglow light curve since they have
sin(theta_jet)<1/Gamma_0. Finally, we estimate that the local rate of GRBs is
~0.3% of all local SNIb/c and ~4.3% of local hypernovae, i.e. SNIb/c with
broad-lines.Comment: 15 pages, 8 figures, 1 table. Accepted for publication in MNRA
Bulk Lorentz factors of Gamma-Ray Bursts
Knowledge of the bulk Lorentz factor of GRBs allows us to
compute their comoving frame properties shedding light on their physics. Upon
collisions with the circumburst matter, the fireball of a GRB starts to
decelerate, producing a peak or a break (depending on the circumburst density
profile) in the light curve of the afterglow. Considering all bursts with known
redshift and with an early coverage of their emission, we find 67 GRBs with a
peak in their optical or GeV light curves at a time . For another
106 GRBs we set an upper limit . We show that
is due to the dynamics of the fireball deceleration and not to the passage of a
characteristic frequency of the synchrotron spectrum across the optical band.
Considering the of 66 long GRBs and the 85 most constraining upper
limits, using censored data analysis methods, we reconstruct the most likely
distribution of . All are larger than the time when the prompt emission peaks, and are much larger than the time when the fireball becomes transparent. The reconstructed distribution of
has median value 300 (150) for a uniform (wind) circumburst
density profile. In the comoving frame, long GRBs have typical isotropic
energy, luminosity, and peak energy erg, erg s ,
and keV in the homogeneous (wind) case. We
confirm that the significant correlations between and the rest frame
isotropic energy (), luminosity () and peak energy
() are not due to selection effects. Assuming a typical opening
angle of 5 degrees, we derive the distribution of the jet baryon loading which
is centered around a few .Comment: 19 pages, 11 figures, 6 tables. Accepted for publication on Astronomy
& Astrophysic
Cellular automaton models for time-correlated random walks: derivation and analysis.
Many diffusion processes in nature and society were found to be anomalous, in the sense of being fundamentally different from conventional Brownian motion. An important example is the migration of biological cells, which exhibits non-trivial temporal decay of velocity autocorrelation functions. This means that the corresponding dynamics is characterized by memory effects that slowly decay in time. Motivated by this we construct non-Markovian lattice-gas cellular automata models for moving agents with memory. For this purpose the reorientation probabilities are derived from velocity autocorrelation functions that are given a priori; in that respect our approach is "data-driven". Particular examples we consider are velocity correlations that decay exponentially or as power laws, where the latter functions generate anomalous diffusion. The computational efficiency of cellular automata combined with our analytical results paves the way to explore the relevance of memory and anomalous diffusion for the dynamics of interacting cell populations, like confluent cell monolayers and cell clustering.The authors thank the Centre for Information Services and High Performance Computing (ZIH) at TU Dresden for providing an excellent infrastructure. The authors acknowledge support by the German Research Foundation and the Open Access Publication Funds of the TU Dresden.The authors would like to thank Anja Voß-Böhme, Lutz Brusch, Fabian Rost, Osvaldo Chara, Simon Syga, and Oleksandr Ostrenko for their helpful comments and fruitful discussions. Andreas Deutsch is grateful to the Deutsche Krebshilfe for support. Andreas Deutsch is supported by the German Research Foundation (Deutsche Forschungsgemeinschaft) within the projects SFB-TR 79 “Materials for tissue regeneration within systemically altered bones” and Research Cluster of Excellence “Center for Advancing Electronics Dresden” (cfaed). Haralampos Hatzikirou would like to acknowledge the SYSMIFTA ERACoSysMed grant (031L0085B) for the financial support of this work and the German Federal Ministry of Education and Research within the Measures for the Establishment of Systems Medicine, project SYSIMIT (BMBF eMed project SYSIMIT, FKZ: 01ZX1308D). Josué Manik Nava-Sedeño is supported by the joint scolarship program DAAD-CONACYT-Regierungsstipendien (50017046) by the German Academic Exchange Service and the National Council on Science and Technology of Mexico
The reaction Cl + H2CO yields HCl + HCO: Decreased sensitivity of stratospheric ozone to chlorine perturbations
The absolute rate constant for the reaction Cl + H2CO yields HCl + HCO was determined by the flash-photolysis resonance fluorescence method to be 7.5 plus or minus 0.9 (2 sigma) times 10 to the minus 11th power cu cm/molecule sec at 298 K and to have a negligible temperature dependence. This rate which is more than 2000 times faster than the rate of Cl + CH4 indicates that formaldehyde (H2CO) will compete significantly with methane (CH4) for the conversion of active chlorine in the stratosphere to the inactive reservoir HCl. Chlorine will thus be a less efficient destroyer of stratosphere ozone than previously believed. Ambient stratospheric ozone will depend less on the ambient chlorine amount and the predicted response to chlorine perturbations will be lessened. One-dimensional eddy-diffusion photochemical model calculations indicate a factor of 1.1 less sensitivity to chlorine than recently reported. For a steady-state CFM release at 1975 rates (750,000 tons/year) the eventual ozone depletion is now calculated to be 14%
Development of Anastrepha grandis (Diptera: Tephritidae) under constant temperatures and field validation of a laboratory model for temperature requirements.
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Finite-temperature corrections to the Lorenz ratio at the N = 3 topological Kondo fixed point
We analyze the finite-temperature scaling of the Lorenz ratio at the topological Kondo fixed point realized at a junction of three interacting quantum wires connected to a floating superconducting island. Using the Tomonaga-Luttinger liquid approach to the quantum wires, we derive the full functional dependence of the finite-temperature correction on the Luttinger parameter g
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