3,925 research outputs found
Study of high altitude plume impingement
Computer program has been developed as analytical tool to predict severity of effects of exhaust of rocket engines on adjacent spacecraft surfaces. Program computes forces, moments, pressures, and heating rates on surfaces immersed in or subjected to exhaust plume environments. Predictions will be useful in design of systems where such problems are anticipated
Environmental, developmental, and genetic factors controlling root system architecture
A better understanding of the development and architecture of roots is essential to develop strategies to increase crop yield and optimize agricultural land use. Roots control nutrient and water uptake, provide anchoring and mechanical support and can serve as important storage organs. Root growth and development is under tight genetic control and modulated by developmental cues including plant hormones and the environment. This review focuses on root architecture and its diversity and the role of environment, nutrient, and water as well as plant hormones and their interactions in shaping root architecture
QCD
We discuss QCD studies that will be possible at LEP2. We examine both
experimental and theoretical aspects of jets, fragmentation functions,
multiplicities and particle spectra.Comment: 44 pages, Latex, epsfig, 18 figures, to appear on the Report of the
Workshop on Physics at LEP2, CERN 96-01, vol. 1, 199
CO line emission in the halo of a radio galaxy at z=2.6
We report the detection of luminous CO(3-2) line emission in the halo of the
z=2.6 radio galaxy (HzRG) TXS0828+193, which has no detected counterpart at
optical to mid-infrared wavelengths implying a stellar mass < few x10^9 M_sun
and relatively low star-formation rates. With the IRAM PdBI we find two CO
emission line components at the same position at ~80 kpc distance from the HzRG
along the axis of the radio jet, with different blueshifts of few 100 km s^-1
relative to the HzRG and a total luminosity of ~2x10^10 K km s^-1 pc^2 detected
at 8 sigma significance. HzRGs have significant galaxy overdensities and
extended halos of metal-enriched gas often with embedded clouds or filaments of
denser material, and likely trace very massive dark-matter halos. The CO
emission may be associated with a gas-rich, low-mass satellite galaxy with
little on-going star formation, in contrast to all previous CO detections of
galaxies at similar redshifts. Alternatively, the CO may be related to a gas
cloud or filament and perhaps jet-induced gas cooling in the outer halo,
somewhat in analogy with extended CO emission found in low-redshift galaxy
clusters.Comment: MNRAS Letters, accepte
Quantifying the anisotropy in the infrared emission of powerful AGN
We use restframe near- and mid-IR data of an isotropically selected sample of
quasars and radio galaxies at 1.0 \leq z \leq 1.4, which have been published
previously, to study the wavelength-dependent anisotropy of the IR emission.
For that we build average SEDs of the quasar subsample (= type 1 AGN) and radio
galaxies (= type 2 AGN) from ~1-17 {\mu}m and plot the ratio of both average
samples. From 2 to 8 {\mu}m restframe wavelength the ratio gradually decreases
from 20 to 2 with values around 3 in the 10{\mu}m silicate feature. Longward of
12{\mu}m the ratio decreases further and shows some high degree of isotropy at
15 {\mu}m (ratio ~1.4). The results are consistent with upper limits derived
from the X-ray/mid-IR correlation of local Seyfert galaxies. We find that the
anisotropy in our high-luminosity radio-loud sample is smaller than in
radio-quiet lower-luminosity AGN which may be interpreted in the framework of a
receding torus model with luminosity-dependent obscuration properties. It is
also shown that the relatively small degree of anisotropy is consistent with
clumpy torus models.Comment: 6 pages, 2 figures; accepted by Ap
The Effect of Planarization on Width
We study the effects of planarization (the construction of a planar diagram
from a non-planar graph by replacing each crossing by a new vertex) on
graph width parameters. We show that for treewidth, pathwidth, branchwidth,
clique-width, and tree-depth there exists a family of -vertex graphs with
bounded parameter value, all of whose planarizations have parameter value
. However, for bandwidth, cutwidth, and carving width, every graph
with bounded parameter value has a planarization of linear size whose parameter
value remains bounded. The same is true for the treewidth, pathwidth, and
branchwidth of graphs of bounded degree.Comment: 15 pages, 6 figures. To appear at the 25th International Symposium on
Graph Drawing and Network Visualization (GD 2017
What is the probability of connecting two points ?
The two-terminal reliability, known as the pair connectedness or connectivity
function in percolation theory, may actually be expressed as a product of
transfer matrices in which the probability of operation of each link and site
is exactly taken into account. When link and site probabilities are and
, it obeys an asymptotic power-law behavior, for which the scaling factor
is the transfer matrix's eigenvalue of largest modulus. The location of the
complex zeros of the two-terminal reliability polynomial exhibits structural
transitions as .Comment: a few critical polynomials are at the end of the .tex source fil
Jet vetoing and Herwig++
We investigate the simulation of events with gaps between jets with a veto on
additional radiation in the gap in Herwig++. We discover that the
currently-used random treatment of radiation in the parton shower is generating
some unphysical behaviour for wide-angle gluon emission in QCD 2 to 2
scatterings. We explore this behaviour quantitatively by making the same
assumptions as the parton shower in the analytical calculation. We then modify
the parton shower algorithm in order to correct the simulation of QCD
radiation.Comment: 18 pages, 11 figure
(Total) Vector Domination for Graphs with Bounded Branchwidth
Given a graph of order and an -dimensional non-negative
vector , called demand vector, the vector domination
(resp., total vector domination) is the problem of finding a minimum
such that every vertex in (resp., in ) has
at least neighbors in . The (total) vector domination is a
generalization of many dominating set type problems, e.g., the dominating set
problem, the -tuple dominating set problem (this is different from the
solution size), and so on, and its approximability and inapproximability have
been studied under this general framework. In this paper, we show that a
(total) vector domination of graphs with bounded branchwidth can be solved in
polynomial time. This implies that the problem is polynomially solvable also
for graphs with bounded treewidth. Consequently, the (total) vector domination
problem for a planar graph is subexponential fixed-parameter tractable with
respectto , where is the size of solution.Comment: 16 page
Elevated estuary water temperature drives fish gut dysbiosis and increased loads of pathogenic vibrionaceae
Marine water temperatures are increasing globally, with eastern Australian estuaries warming faster than predicted. There is growing evidence that this rapid warming of coastal waters is increasing the abundance and virulence of pathogenic members of the Vibrionaceae, posing a significant health risk to both humans and aquatic organisms. Fish disease, notably outbreaks of emerging pathogens in response to environmental perturbations such as heatwaves, have been recognised in aquaculture settings. Considerably less is known about how rising sea surface temperatures will impact the microbiology of wild fish populations, particularly those within estuarine systems that are more vulnerable to warming. We used a combination of Vibrio-specific quantitative PCR and amplicon sequencing of the 16S rRNA and hsp60 genes to examine seawater and fish (Pelates sexlineatus) gut microbial communities across a quasi-natural experimental system, where thermal pollution from coal-fired power stations creates a temperature gradient of up to 6 °C, compatible with future predicted temperature increases. At the warmest site, fish hindgut microbial communities were in a state of dysbiosis characterised by shifts in beta diversity and a proliferation (71.5% relative abundance) of the potential fish pathogen Photobacterium damselae subsp. damselae. Comparable patterns were not identified in the surrounding seawater, indicating opportunistic proliferation within estuarine fish guts under thermal stress. A subsequent evaluation of predicted future warming-related risk due to pathogenic Vibrionaceae in temperate estuarine fish demonstrated that warming is likely to drive opportunistic pathogen increases in the upper latitudinal range of this estuarine fish, potentially impacting adaptations to future warming. These findings represent a breakthrough in our understanding of the dynamics of emerging pathogens in populations of wild aquatic organisms within environments likely to experience rapid warming under future climate change
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