159 research outputs found
Beyond the Solar Circle â Trends in Massive Star Formation Between the Inner and Outer Galaxy
We have compiled the most complete compact and ultracompact HâII region catalogue to date via multiwavelength inspection of survey data. We utilize data from the recently available SASSy 850âÎŒm survey to identify massive star-forming clumps in the outer Galaxy (RGC > 8.5âkpc) and cross-match with infrared and radio data of known UC HâII regions from the RMS database. For the inner Galaxy sample (RGC < 8.5âkpc), we adopt the compact HâII regions from previous works that used similar methods to cross-match ATLASGAL with either CORNISH or RMS, depending on the location within the Galactic plane. We present a new UC HâII region catalogue that more than doubles the original sample size of previous work, totalling 536 embedded HâII regions and 445 host clumps. We examine the distance independent values of NLy/M and Lbol/M as proxies for massive star formation efficiency and overall star formation efficiency, respectively. We find a significant trend showing that Lbol/M decreases with increasing RGC, suggesting that the overall star formation per unit mass is less in the outer Galaxy
The production of species-specific highly unsaturated fatty acyl-containing LCOs from Rhizobium leguminosarum bv. trifolii is stringently regulated by nodD and involves the nodRL genes
Microbial Biotechnolog
Flavonoids synthesized in cortical cells during nodule initiation are early developmental markers in white clover
Plant science
Nonlinear dynamics of soft boson collective excitations in hot QCD plasma III: bremsstrahlung and energy losses
Within of the framework of semiclassical approximation a general formalism
for deriving an effective current generating bremsstrahlung of arbitrary number
of soft gluons (longitudinal or transverse ones) in scattering of higher-energy
parton off thermal parton in hot quark-gluon plasma with subsequent extension
to two and more scatterers, is obtained. For the case of static color centers
an expression for energy loss induced by usual bremsstrahlung of lowest-order
with allowance for an effective temperature-induced gluon mass and finite mass
of the projectile (heavy quark), is derived. The detailed analysis of
contribution to radiation energy loss associated with existence of effective
three-gluon vertex induced by hot QCD medium, is performed. It is shown that in
general, the bremsstrahlung associated with this vertex have no sharp direction
(as in the case of usual bremsstrahlung) and therefore here, we can expect an
absence of suppression effect due to multiple scattering. For the case of two
color static scattering centers it was shown that the problem of calculation of
bremsstrahlung induced by four-gluon hard thermal loop (HTL) vertex correction
can be reduced to the problem of the calculation of bremsstrahlung induced by
three-gluon HTL correction. It was shown that for limiting value of soft gluon
occupation number all higher processes of
bremsstrahlung of arbitrary number of soft gluons become of the same order in
coupling, and the problem of resummation of all relevant contributions to
radiation energy loss of fast parton, arises. An explicit expression for matrix
element of two soft gluon bremsstrahlung in small angles approximation is
obtained.Comment: 68 pages, 9 EPS figures; added new sections 8, 10 and reference
Face morphology: Can it tell us something about body weight and fat?
This paper proposes a method for an automatic extraction of geometric features, related to weight parameters, from 3D facial data acquired with low-cost depth scanners. The novelty of the method relies both on the processing of the 3D facial data and on the definition of the geometric features which are conceptually simple, robust against noise and pose estimation errors, computationally efficient, invariant with respect to rotation, translation, and scale changes. Experimental results show that these measurements are highly correlated with weight, BMI, and neck circumference, and well correlated with waist and hip circumference, which are markers of central obesity. Therefore the proposed method strongly supports the development of interactive, non-obtrusive systems able to provide a support for the detection of weight-related problems
Experimental and Theoretical Challenges in the Search for the Quark Gluon Plasma: The STAR Collaboration's Critical Assessment of the Evidence from RHIC Collisions
We review the most important experimental results from the first three years
of nucleus-nucleus collision studies at RHIC, with emphasis on results from the
STAR experiment, and we assess their interpretation and comparison to theory.
The theory-experiment comparison suggests that central Au+Au collisions at RHIC
produce dense, rapidly thermalizing matter characterized by: (1) initial energy
densities above the critical values predicted by lattice QCD for establishment
of a Quark-Gluon Plasma (QGP); (2) nearly ideal fluid flow, marked by
constituent interactions of very short mean free path, established most
probably at a stage preceding hadron formation; and (3) opacity to jets. Many
of the observations are consistent with models incorporating QGP formation in
the early collision stages, and have not found ready explanation in a hadronic
framework. However, the measurements themselves do not yet establish
unequivocal evidence for a transition to this new form of matter. The
theoretical treatment of the collision evolution, despite impressive successes,
invokes a suite of distinct models, degrees of freedom and assumptions of as
yet unknown quantitative consequence. We pose a set of important open
questions, and suggest additional measurements, at least some of which should
be addressed in order to establish a compelling basis to conclude definitively
that thermalized, deconfined quark-gluon matter has been produced at RHIC.Comment: 101 pages, 37 figures; revised version to Nucl. Phys.
Search for a W' boson decaying to a bottom quark and a top quark in pp collisions at sqrt(s) = 7 TeV
Results are presented from a search for a W' boson using a dataset
corresponding to 5.0 inverse femtobarns of integrated luminosity collected
during 2011 by the CMS experiment at the LHC in pp collisions at sqrt(s)=7 TeV.
The W' boson is modeled as a heavy W boson, but different scenarios for the
couplings to fermions are considered, involving both left-handed and
right-handed chiral projections of the fermions, as well as an arbitrary
mixture of the two. The search is performed in the decay channel W' to t b,
leading to a final state signature with a single lepton (e, mu), missing
transverse energy, and jets, at least one of which is tagged as a b-jet. A W'
boson that couples to fermions with the same coupling constant as the W, but to
the right-handed rather than left-handed chiral projections, is excluded for
masses below 1.85 TeV at the 95% confidence level. For the first time using LHC
data, constraints on the W' gauge coupling for a set of left- and right-handed
coupling combinations have been placed. These results represent a significant
improvement over previously published limits.Comment: Submitted to Physics Letters B. Replaced with version publishe
Search for the standard model Higgs boson decaying into two photons in pp collisions at sqrt(s)=7 TeV
A search for a Higgs boson decaying into two photons is described. The
analysis is performed using a dataset recorded by the CMS experiment at the LHC
from pp collisions at a centre-of-mass energy of 7 TeV, which corresponds to an
integrated luminosity of 4.8 inverse femtobarns. Limits are set on the cross
section of the standard model Higgs boson decaying to two photons. The expected
exclusion limit at 95% confidence level is between 1.4 and 2.4 times the
standard model cross section in the mass range between 110 and 150 GeV. The
analysis of the data excludes, at 95% confidence level, the standard model
Higgs boson decaying into two photons in the mass range 128 to 132 GeV. The
largest excess of events above the expected standard model background is
observed for a Higgs boson mass hypothesis of 124 GeV with a local significance
of 3.1 sigma. The global significance of observing an excess with a local
significance greater than 3.1 sigma anywhere in the search range 110-150 GeV is
estimated to be 1.8 sigma. More data are required to ascertain the origin of
this excess.Comment: Submitted to Physics Letters
- âŠ