636 research outputs found
Correlations and Renormalization in Lattice Gases
A complete formulation is given of an exact kinetic theory for lattice gases.
This kinetic theory makes possible the calculation of corrections to the usual
Boltzmann / Chapman-Enskog analysis of lattice gases due to the buildup of
correlations. It is shown that renormalized transport coefficients can be
calculated perturbatively by summing terms in an infinite series. A
diagrammatic notation for the terms in this series is given, in analogy with
the diagrammatic expansions of continuum kinetic theory and quantum field
theory. A closed-form expression for the coefficients associated with the
vertices of these diagrams is given. This method is applied to several standard
lattice gases, and the results are shown to correctly predict experimentally
observed deviations from the Boltzmann analysis.Comment: 94 pages, pure LaTeX including all figure
Reverberation in tidal disruption events: dust echoes, coronal emission lines, multi-wavelength cross-correlations, and QPOs
High Energy Astrophysic
ENTRAP and its potential interaction with European networks
AbstractENTRAP comprises a pan-European cooperation of leading scientific institutions and regulatory bodies in the field of nuclear-waste characterization and its quality assurance for the safe disposal of radioactive waste. Here, the scope of this cooperation is presented and explained and links or interfaces for a potential collaboration with partners fulfilling tasks of IDG-TP are pursued
Play&tune: user feedback in the development of a serious game for optimizing hearing aid orientation
Many hearing aid (HA) users are dissatisfied with HA performance in social situations. One way to improve HA outcomes is training the users to understand how HAs work. Play&Tune was designed to provide this training and to foster autonomy in hearing rehabilitation. We carried out two prototype evaluations and a prerelease evaluation of Play&Tune with 71 HA users, using an interview or online survey. Users gave detailed feedback on their experiences with the app. Most participants enjoyed learning about HAs and expressed a desire for autonomy over their HA settings. Our case study reinforces the importance of user feedback during app development
An ultraviolet-optical flare from the tidal disruption of a helium-rich stellar core
The flare of radiation from the tidal disruption and accretion of a star can
be used as a marker for supermassive black holes that otherwise lie dormant and
undetected in the centres of distant galaxies. Previous candidate flares have
had declining light curves in good agreement with expectations, but with poor
constraints on the time of disruption and the type of star disrupted, because
the rising emission was not observed. Recently, two `relativistic' candidate
tidal disruption events were discovered, each of whose extreme X-ray luminosity
and synchrotron radio emission were interpreted as the onset of emission from a
relativistic jet. Here we report the discovery of a luminous
ultraviolet-optical flare from the nuclear region of an inactive galaxy at a
redshift of 0.1696. The observed continuum is cooler than expected for a simple
accreting debris disk, but the well-sampled rise and decline of its light curve
follows the predicted mass accretion rate, and can be modelled to determine the
time of disruption to an accuracy of two days. The black hole has a mass of
about 2 million solar masses, modulo a factor dependent on the mass and radius
of the star disrupted. On the basis of the spectroscopic signature of ionized
helium from the unbound debris, we determine that the disrupted star was a
helium-rich stellar core.Comment: To appear in Nature on May 10, 201
The tomato cytochrome P450 CYP712G1 catalyzes the double oxidation of orobanchol <i>en route</i> to the rhizosphere signaling strigolactone, solanacol
Strigolactones (SLs) are rhizosphere signalling molecules and phytohormones. The biosynthetic pathway of SLs in tomato has been partially elucidated, but the structural diversity in tomato SLs predicts that additional biosynthetic steps are required. Here, root RNA-seq data and co-expression analysis were used for SL biosynthetic gene discovery. This strategy resulted in a candidate gene list containing several cytochrome P450s. Heterologous expression in Nicotiana benthamiana and yeast showed that one of these, CYP712G1, can catalyse the double oxidation of orobanchol, resulting in the formation of three didehydro-orobanchol (DDH) isomers. Virus-induced gene silencing and heterologous expression in yeast showed that one of these DDH isomers is converted to solanacol, one of the most abundant SLs in tomato root exudate. Protein modelling and substrate docking analysis suggest that hydroxy-orbanchol is the likely intermediate in the conversion from orobanchol to the DDH isomers. Phylogenetic analysis demonstrated the occurrence of CYP712G1 homologues in the Eudicots only, which fits with the reports on DDH isomers in that clade. Protein modelling and orobanchol docking of the putative tobacco CYP712G1 homologue suggest that it can convert orobanchol to similar DDH isomers as tomato
Discovery of a Fast Iron Low-ionization Outflow in the Early Evolution of the Nearby Tidal Disruption Event AT2019qiz
We report the results of UV and optical photometric and spectroscopic
analysis on the tidal disruption event (TDE) AT2019qiz. Our follow-up
observations started shortly after (10 days) its optical light begin
to rise and lasted for a period of six months. Our late-time host-dominated
spectrum indicates that the host galaxy likely harbours a weak AGN. The initial
HST spectrum of AT2019qiz exhibits a iron and low-ionization broad absorption
line (FeLoBAL) system that is seen for the first time in a TDE. This spectrum
also bears a striking resemblance to that of Gaia16apd, a superluminous
supernova. Our observations provide insights into the outflow properties in
TDEs and show evidence for a connection between TDEs and engine-powered
supernovae at early phase, as originally suggested in Metzger & Stone (2016).
In a time frame of 50 days, the UV spectra of AT2019qiz started to resemble
previous TDEs with only high-ionization BALs. The change in UV spectral
signatures is accompanied by a decrease in the outflow velocity, which began at
km s and decelerated to km s. A similar
evolution in the H emission line width further supports the speculation
that the broad Balmer emission lines are formed in TDE outflows. In addition,
we detect narrow absorption features on top of the FeLoBAL signatures in the
early HST UV spectrum of AT2019qiz. The measured HI column density corresponds
to a Lyman-limit system whereas the metal absorption lines, such as NV, CIV,
FeII, and MgII, are likely probing the circumnuclear gas and interstellar
medium in the host galaxy.Comment: 24 pages, 13 figures, 3 tables. Submitted to ApJ on Nov 03 202
- …