796 research outputs found
Recommended from our members
Composite scalars at CERN LEP: Constraining technicolor theories
LEPI and LEPII data can be used to constrain technicolor models with light,
neutral pseudo-Nambu-Goldstone bosons, Pa. We use published limits on branching
ratios and cross sections for final states with photons, large missing energy,
jet pairs, and b bbar pairs to constrain the anomalous Pa Z0 Z0, Pa Z0 photon,
and Pa photon photon couplings. From these results, we derive bounds on the
size of the technicolor gauge group and the number of technifermion doublets in
models such as Low-scale Technicolor
Water-soaked porous evidence:a comparison of processing methods
This study compared the U.K. Home Office formulation for physical developer (PD) against Oil Red O (ORO) and a modified formulation of physical developer (MPD) that uses Tween 20 instead of Synperonic-N for enhancing fingermarks. Three different donors deposited fingermarks on porous surfaces (white paper, leaflets, and cardboard), with aging periods varying from 7 to 28 days. None of the techniques that were tested provided enhancement of latent fingermarks on leaflets, whereas poor-quality enhancement was observed on cardboard. In contrast, all techniques were more successful on white paper surfaces. The results obtained on white paper suggested that PD and MPD performed similarly, with PD detecting 82.3% of the deposited fingermarks and MPD detecting 86.5% of the deposited fingermarks. PD yielded a higher percentage (38.5%) of fingermarks with fine ridge detail (i.e., those with grade 2 or above) than MPD (35.4%). ORO, however, yielded poor results, enhancing only 4.5% of latent fingermarks, but showed no ridge detail in any of the enhancements (i.e., only showed grade 1 enhancements.
A new methodology for the quantitative visualization of coherent flow structures in alluvial channels using multibeam echo-sounding (MBES)
In order to investigate the interactions between turbulence and suspended sediment transport in natural aqueous environments, we ideally require a technique that allows simultaneous measurement of fluid velocity and sediment concentration for the whole flow field. Here, we report on development of a methodology using the water column acoustic backscatter signal from a multibeam echo sounder to simultaneously quantify flow velocities and sediment concentrations. The application of this new technique is illustrated with reference to flow over the leeside of an alluvial sand dune, which allows, for the first time in a field study, quantitative visualization of large-scale, whole flow field, turbulent coherent flow structures associated with the dune leeside that are responsible for suspending bed sediment. This methodology holds great potential for use in a wide range of aqueous geophysical flows
The density of critical percolation clusters touching the boundaries of strips and squares
We consider the density of two-dimensional critical percolation clusters,
constrained to touch one or both boundaries, in infinite strips, half-infinite
strips, and squares, as well as several related quantities for the infinite
strip. Our theoretical results follow from conformal field theory, and are
compared with high-precision numerical simulation. For example, we show that
the density of clusters touching both boundaries of an infinite strip of unit
width (i.e. crossing clusters) is proportional to .
We also determine numerically contours for the density of clusters crossing
squares and long rectangles with open boundaries on the sides, and compare with
theory for the density along an edge.Comment: 11 pages, 6 figures. Minor revision
Invasion of winter moth in New England: Effects of defoliation and site quality on tree mortality.
Abstract
Widespread and prolonged defoliation by the European winter moth, Operophtera brumata L., has occurred in forests of eastern Massachusetts for more than a decade and populations of winter moth continue to invade new areas of New England. This study characterized the forests of eastern Massachusetts invaded by winter moth and related the duration of winter moth defoliation estimated using dendrochronology to observed levels of tree mortality and understory woody plant density. Quercus basal area mortality in mixed Quercus and mixed Quercus-Pinus strobus forests in eastern Massachusetts ranged from 0-30%; mortality of Quercus in these forests was related to site quality and the number of winter moth defoliation events. In addition, winter moth defoliation events lead to a subsequent increase in understory woody plant density. Our results indicate that winter moth defoliation has been an important disturbance in New England forests that may have lasting impacts
Moderate-Luminosity Growing Black Holes From 1.25 < z < 2.7: Varied Accretion In Disk-Dominated Hosts
We compute black hole masses and bolometric luminosities for 57 active
galactic nuclei (AGN) in the redshift range 1.25 < z < 2.67, selected from the
GOODS-South deep multi-wavelength survey field via their X-ray emission. We
determine host galaxy morphological parameters by separating the galaxies from
their central point sources in deep HST images, and host stellar masses and
colors by multi-wavelength SED fitting. 90% of GOODS AGN at these redshifts
have detected rest-frame optical nuclear point sources; bolometric luminosities
range from 2e43 - 2e46 erg/s. The black holes are growing at a range of
accretion rates, with at least 50% of the sample having L/L_Edd < 0.1. 70% of
host galaxies have stellar masses M* > 1e10 M_sun, with a range of colors
suggesting a complex star formation history. We find no evolution of AGN
bolometric luminosity within the sample, and no correlation between AGN
bolometric luminosity and host stellar mass, color or morphology. Fully half
the sample of host galaxies is disk-dominated, with another 25% having strong
disk components. Fewer than 15% of the systems appear to be at some stage of a
major merger. These moderate-luminosity AGN hosts are therefore inconsistent
with a dynamical history dominated by mergers strong enough to destroy disks,
indicating minor mergers or secular processes dominate the co-evolution of
galaxies and their central black holes at z ~ 2.Comment: 11 pages, 6 figures, accepted to ApJ. Sersic indices, AGN/galaxy
luminosity ratios, stellar masses etc. provided in Table
Major Mergers Host the Most Luminous Red Quasars at z ~ 2: A Hubble Space Telescope WFC3/IR Study
We used the Hubble Space Telescope WFC3 near-infrared camera to image the
host galaxies of a sample of eleven luminous, dust-reddened quasars at z ~ 2 --
the peak epoch of black hole growth and star formation in the Universe -- to
test the merger-driven picture for the co-evolution of galaxies and their
nuclear black holes. The red quasars come from the FIRST+2MASS red quasar
survey and a newer, deeper, UKIDSS+FIRST sample. These dust-reddened quasars
are the most intrinsically luminous quasars in the Universe at all redshifts,
and may represent the dust-clearing transitional phase in the merger-driven
black hole growth scenario. Probing the host galaxies in rest-frame visible
light, the HST images reveal that 8/10 of these quasars have actively merging
hosts, while one source is reddened by an intervening lower redshift galaxy
along the line-of-sight. We study the morphological properties of the quasar
hosts using parametric Sersic fits as well as the non-parametric estimators
(Gini coefficient, M_{20} and asymmetry). Their properties are heterogeneous
but broadly consistent with the most extreme morphologies of local merging
systems such as Ultraluminous Infrared galaxies. The red quasars have a
luminosity range of log(L_bol) = 47.8 - 48.3 (erg/s) and the merger fraction of
their AGN hosts is consistent with merger-driven models of luminous AGN
activity at z=2, which supports the picture in which luminous quasars and
galaxies co-evolve through major mergers that trigger both star formation and
black hole growth.Comment: Submitted to ApJ. This version includes the response to the referee
repor
- …