Constraining the onset of viscous hydrodynamics

We derive two general criteria that can be used to constrain the initial time of the onset of 2nd-order conformal viscous hydrodynamics in relativistic heavy-ion collisions. We show this explicitly for 0+1 dimensional viscous hydrodynamics and discuss how to extend the constraint to higher dimensions.Comment: 2 pages, 2 figures - To appear in the conference proceedings for Quark Matter 2009, March 30 - April 4, Knoxville, Tennessee. Selected Poster for the Flash Talk Session at QM09. v3: typos corrected, minor format changes and updated reference

Lattice QCD and Hydro/Cascade Model of Heavy Ion Collisions

We report here on a recent lattice study of the QCD transition region at finite temperature and zero chemical potential using domain wall fermions (DWF). We also present a parameterization of the QCD equation of state obtained from lattice QCD that is suitable for use in hydrodynamics studies of heavy ion collisions. Finally, we show preliminary results from a multi-stage hydrodynamics/hadron cascade model of a heavy ion collision, in an attempt to understand how well the experimental data (e.g. particle spectra, elliptic flow, and HBT radii) can constrain the inputs (e.g. initial temperature, freezeout temperature, shear viscosity, equation of state) of the theoretical model.Comment: 10 pages, 12 figures. Proceedings for the 26th Winter Workshop on Nuclear Dynamics, Ocho Rios, Jamaica, Jan 2-9, 201

Potential of nonlocally filtered pursuit monostatic TanDEM-X data for coastline detection

This article investigates the potential of nonlocally filtered pursuit monostatic TanDEM-X data for coastline detection in comparison to conventional TanDEM-X data, i.e. image pairs acquired in repeat-pass or bistatic mode. For this task, an unsupervised coastline detection procedure based on scale-space representations and K-medians clustering as well as morphological image post-processing is proposed. Since this procedure exploits a clear discriminability of "dark" and "bright" appearances of water and land surfaces, respectively, in both SAR amplitude and coherence imagery, TanDEM-X InSAR data acquired in pursuit monostatic mode is expected to provide a promising benefit. In addition, we investigate the benefit introduced by a utilization of a non-local InSAR filter for amplitude denoising and coherence estimation instead of a conventional box-car filter. Experiments carried out on real TanDEM-X pursuit monostatic data confirm our expectations and illustrate the advantage of the employed data configuration over conventional TanDEM-X products for automatic coastline detection

Relating different approaches to nuclear broadening

Transverse momentum broadening of fast partons propagating through a large nucleus is proportional to the average color field strength in the nucleus. In this work, the corresponding coefficient is determined in three different frameworks, namely in the color dipole approach, in the approach of Baier et al. and in the higher twist factorization formalism. This result enables one to use a parametrization of the dipole cross section to estimate the values of the gluon transport coefficient and of the higher twist matrix element, which is relevant for nuclear broadening. A considerable energy dependence of these quantities is found. In addition, numerical calculations are compared to data for nuclear broadening of Drell-Yan dileptons, J/psi and Upsilon mesons. The scale dependence of the strong coupling constant leads to measurable differences between the higher twist approach and the other two formalisms.Comment: 11 pages, 3 figures; v2: some changes in presentation, reference added, accepted for publication in PL

Hardwiring of fine synaptic layers in the zebrafish visual pathway

<p>Abstract</p> <p>Background</p> <p>Neuronal connections are often arranged in layers, which are divided into sublaminae harboring synapses with similar response properties. It is still debated how fine-grained synaptic layering is established during development. Here we investigated two stratified areas of the zebrafish visual pathway, the inner plexiform layer (IPL) of the retina and the neuropil of the optic tectum, and determined if activity is required for their organization.</p> <p>Results</p> <p>The IPL of 5-day-old zebrafish larvae is composed of at least nine sublaminae, comprising the connections between different types of amacrine, bipolar, and ganglion cells (ACs, BCs, GCs). These sublaminae were distinguished by their expression of cell type-specific transgenic fluorescent reporters and immunohistochemical markers, including protein kinase Cβ (PKC), parvalbumin (Parv), zrf3, and choline acetyltransferase (ChAT). In the tectum, four retinal input layers abut a laminated array of neurites of tectal cells, which differentially express PKC and Parv. We investigated whether these patterns were affected by experimental disruptions of retinal activity in developing fish. Neither elimination of light inputs by dark rearing, nor a D, L-amino-phosphono-butyrate-induced reduction in the retinal response to light onset (but not offset) altered IPL or tectal lamination. Moreover, thorough elimination of chemical synaptic transmission with <it>Botulinum </it>toxin B left laminar synaptic arrays intact.</p> <p>Conclusion</p> <p>Our results call into question a role for activity-dependent mechanisms – instructive light signals, balanced <it>on </it>and <it>off </it>BC activity, Hebbian plasticity, or a permissive role for synaptic transmission – in the synaptic stratification we examined. We propose that genetically encoded cues are sufficient to target groups of neurites to synaptic layers in this vertebrate visual system.</p

Color-Singlet and Color-Octet Contributions to J/ψJ/\psi Photoproduction

I discuss the impact of color-octet contributions and higher-order QCD corrections on the cross section for inelastic $J/\psi$ photoproduction. The theoretical predictions are compared with recent experimental data obtained at HERA.Comment: LaTeX, 10 pages, 6 figures. Talk presented at the Workshops `QED and QCD in Higher Orders', Rheinsberg, Germany, April 21-26 and `Quarkonium Physics', Chicago, USA, June 13-15, 1996; to appear in the proceeding

Infrared Surface Brightness Fluctuations of the Coma Elliptical NGC 4874 and the Value of the Hubble Constant

We have used the Keck I Telescope to measure K-band surface brightness fluctuations (SBFs) of NGC 4874, the dominant elliptical galaxy in the Coma cluster. We use deep HST WFPC2 optical imaging to account for the contamination due to faint globular clusters and improved analysis techniques to derive measurements of the SBF apparent magnitude. Using a new SBF calibration which accounts for the dependence of K-band SBFs on the integrated color of the stellar population, we measure a distance modulus of 34.99+/-0.21 mag (100+/-10 Mpc) for the Coma cluster. The resulting value of the Hubble constant is 71+/-8 km/s/Mpc, not including any systematic error in the HST Cepheid distance scale.Comment: ApJ Letters, in press. Uses emulateapj5.st

A holistic multi-scale approach to using 3D scanning technology in accident reconstruction

Three-dimensional scanning and documentation methods are becoming increasingly employed by law enforcement personnel for crime scene and accident scene recording. Three-dimensional documentation of the victim’s body in such cases is also increasingly used as the field of forensic radiology and imaging is expanding rapidly. These scanning technologies enable a more complete and detailed documentation than standard autopsy. This was used to examine a fatal pedestrian-vehicle collision where the pedestrian was killed by a van whilst crossing the road. Two competing scenarios were considered for the vehicle speed calculation: the pedestrian being projected forward by the impact or the pedestrian being carried on the vehicle’s bonnet. In order to assist with this, the impact area of the accident vehicle was scanned using laser surface scanning, the victim was scanned using postmortem CT and micro-CT and the data sets were combined to virtually match features of the vehicle to injuries on the victim. Micro-CT revealed additional injuries not previously detected, lending support to the pedestrian-carry theory

Identification of cDNAs from Japanese pufferfish (Fugu rubripes) and Atlantic salmon (Salmo salar) coding for homologues to tetrapod prion proteins

AbstractWe identified cDNAs coding for homologues to tetrapod prion proteins (PrPs) in Atlantic salmon (Salmo salar) and Japanese pufferfish (Fugu rubripes), which were termed ‘similar to PrPs’ (stPrPs). Besides significant sequence homologies the fish stPrPs display characteristic structural features in common with tetrapod PrPs. In addition, two stPrPs were shown to be highly expressed in brain tissue. None of the so far identified PrP-homologues of fish resembles doppel. Hence, the duplication of the PrP gene, which generated doppel, may have occurred not in fish but later in the tetrapod lineage. The identification of fish PrPs provides a basis to address concerns about a possible susceptibility of fish to prion infections