916 research outputs found
The SU(2) X U(1) Electroweak Model based on the Nonlinearly Realized Gauge Group
The electroweak model is formulated on the nonlinearly realized gauge group
SU(2) X U(1). This implies that in perturbation theory no Higgs field is
present. The paper provides the effective action at the tree level, the Slavnov
Taylor identity (necessary for the proof of unitarity), the local functional
equation (used for the control of the amplitudes involving the Goldstone
bosons) and the subtraction procedure (nonstandard, since the theory is not
power-counting renormalizable). Particular attention is devoted to the number
of independent parameters relevant for the vector mesons; in fact there is the
possibility of introducing two mass parameters. With this choice the relation
between the ratio of the intermediate vector meson masses and the Weinberg
angle depends on an extra free parameter. We briefly outline a method for
dealing with \gamma_5 in dimensional regularization. The model is formulated in
the Landau gauge for sake of simplicity and conciseness: the QED Ward identity
has a simple and intriguing form.Comment: 19 pages, final version published by Int. J. Mod. Phys. A, some typos
corrected in eqs.(1) and (41). The errors have a pure editing origin.
Therefore they do not affect the content of the pape
Comments on the Equivalence between Chern-Simons Theory and Topological Massive Yang-Mills Theory in 3D
The classical formal equivalence upon a redefinition of the gauge connection
between Chern-Simons theory and topological massive Yang-Mills theory in
three-dimensional Euclidean space-time is analyzed at the quantum level within
the BRST formulation of the Equivalence Theorem. The parameter controlling the
change in the gauge connection is the inverse of the topological
mass. The BRST differential associated with the gauge connection redefinition
is derived and the corresponding Slavnov-Taylor (ST) identities are proven to
be anomaly-free. The Green functions of local operators constructed only from
the (-dependent) transformed gauge connection, as well as those of
BRST invariant operators, are shown to be independent of the parameter
, as a consequence of the validity of the ST identities. The relevance
of the antighost-ghost fields, needed to take into account at the quantum level
the Jacobian of the change in the gauge connection, is analyzed. Their role in
the identification of the physical states of the model within conventional
perturbative gauge theory is discussed.Comment: 19 pages, LATEX, to appear in Journal of High Energy Physic
Design and Construction of NBRRI Pozzolana Cement Pilot Plant Access Road
Nigerian Building and Road Research Institute (NBRRI), in trying to solve the menace of housing deficit ravaging the country, established a Pozzolana Cement Pilot Plant at its Laboratory Complex, Ota, Ogun State. When the plant is fully in operation, it would bring respite/succour to the low-medium class citizenry as the cost of pozzolana cement will be affordable to build a light weight/bungalow structures. This gave rise to the birth of this access road, as it became imperative to design and construct an access road to the Pozzolana Cement Plant using a ‘’stage construction’’ approach. The ‘’stage construction’’ approach/method was adopted to construct a 300m long by 7m wide roadway, where the subgrade (poorly graded sand and clay) was stabilized by proportioning technique of mechanical stabilization with well graded lateritic sub-base and base layers of 100mm thickness each. With the development of the bitumen sprayer by the Engineering Material Research Department, the pozzolana access road was used to test the effectiveness and efficiency of the innovation. The combined lateritic road surfacing of 200mm thickness was overlaid with 80mm thick stone-dust (8mm; ø) interface which was smeared with a thin layer of bitumen MC1. The bitumen surface was then covered with a 100mm thick granite (10mm; ø) layer. All the layers were well compacted using a 730kg pedestrian roller to an average of 20 passes on each layer. However, when the plant is fully operational, the road would facilitate the movement of goods/ NBRRI Pozzolana cements in and out of the Institute (NBRRI) as this would contribute greatly to the economy of the nation after being adopted/accepted by the larger masses as an affordable alternative to conventional Ordinary Portland Cement (OPC) to erect their light weight concrete structures. Keywords: Pozzolana cement, Subgrade, Subbase, Base, Pedestrian roller, Light weight, Stabilization, Ordinary Portland Cement (OPC), Bitumen MC1
A Massive Yang-Mills Theory based on the Nonlinearly Realized Gauge Group
We propose a subtraction scheme for a massive Yang-Mills theory realized via
a nonlinear representation of the gauge group (here SU(2)). It is based on the
subtraction of the poles in D-4 of the amplitudes, in dimensional
regularization, after a suitable normalization has been performed. Perturbation
theory is in the number of loops and the procedure is stable under iterative
subtraction of the poles. The unphysical Goldstone bosons, the Faddeev-Popov
ghosts and the unphysical mode of the gauge field are expected to cancel out in
the unitarity equation. The spontaneous symmetry breaking parameter is not a
physical variable. We use the tools already tested in the nonlinear sigma
model: hierarchy in the number of Goldstone boson legs and weak power-counting
property (finite number of independent divergent amplitudes at each order). It
is intriguing that the model is naturally based on the symmetry SU(2)_L local
times SU(2)_R global. By construction the physical amplitudes depend on the
mass and on the self-coupling constant of the gauge particle and moreover on
the scale parameter of the radiative corrections. The Feynman rules are in the
Landau gauge.Comment: 44 pages, 1 figure, minor changes, final version accepted by Phys.
Rev.
A two-component signal-transduction cascade in Carnobacterium piscicola LV17B:two signaling peptides and one sensor-transmitter
In the lactic acid bacterium Carnobacterium piscicola LV17B a peptide-pheromone dependent quorum-sensing mode is involved in the regulation of bacteriocin production. Bacteriocin CB2 was identified as an environmental signal that induces bacteriocin production. Here, we demonstrate that a second 24 amino acid peptide (CS) also induces bacteriocin production. Transcription activation of several carnobacteriocin operons is triggered by CB2 or CS via a two-component signal transduction system composed of CbnK and CbnR. (C) 2001 Elsevier Science Inc. All rights reserved
What Can Self-Admitted Technical Debt Tell Us About Security? A Mixed-Methods Study
Self-Admitted Technical Debt (SATD) encompasses a wide array of sub-optimal
design and implementation choices reported in software artefacts (e.g., code
comments and commit messages) by developers themselves. Such reports have been
central to the study of software maintenance and evolution over the last
decades. However, they can also be deemed as dreadful sources of information on
potentially exploitable vulnerabilities and security flaws. This work
investigates the security implications of SATD from a technical and
developer-centred perspective. On the one hand, it analyses whether security
pointers disclosed inside SATD sources can be used to characterise
vulnerabilities in Open-Source Software (OSS) projects and repositories. On the
other hand, it delves into developers' perspectives regarding the motivations
behind this practice, its prevalence, and its potential negative consequences.
We followed a mixed-methods approach consisting of (i) the analysis of a
preexisting dataset containing 8,812 SATD instances and (ii) an online survey
with 222 OSS practitioners. We gathered 201 SATD instances through the dataset
analysis and mapped them to different Common Weakness Enumeration (CWE)
identifiers. Overall, 25 different types of CWEs were spotted across commit
messages, pull requests, code comments, and issue sections, from which 8 appear
among MITRE's Top-25 most dangerous ones. The survey shows that software
practitioners often place security pointers across SATD artefacts to promote a
security culture among their peers and help them spot flaky code sections,
among other motives. However, they also consider such a practice risky as it
may facilitate vulnerability exploits. Our findings suggest that preserving the
contextual integrity of security pointers disseminated across SATD artefacts is
critical to safeguard both commercial and OSS solutions against zero-day
attacks.Comment: Accepted in the 21th International Conference on Mining Software
Repositories (MSR '24
Heme Induction with Delta-Aminolevulinic Acid Stimulates an Increase in Water and Electrolyte Excretion
Purpose. Studies were performed to examine hemodynamic and renal function before and after acute induction of the endogenous CO system with delta-aminolevulinic acid (DALA), which drives HO activity. Methods. In vivo studies were conducted on Inactin-anesthetized male Sprague Dawley rats (250–300 g) either with or without chronic pretreatment with L-NAME (50 mg/Kg, q12 hours x4d). Results. DALA (80 μmol/Kg, IV bolus) administration acutely increased endogenous CO production and HO-1 protein. In untreated and L-NAME-pretreated rats, DALA did not alter BP, GFR, or RBF but increased UF, UNaV, and UKV (untreated: Δ108.8 ± 0.28%, 172.1 ± 18.4%, and 165.2 ± 45.9%; pretreated: Δ109.4 ± 0.29%, 187.3 ± 26.9%, and 197.2 ± 45.7%). Acute administration of biliverdin (20 mg/kg, IV) and bilirubin (30 mg/kg, IV) to similarly treated animals did not alter UF, UNaV, and UKV. Conclusion. These results demonstrate that heme oxygenase induction increases urine and electrolyte excretion and suggest a direct tubular action of endogenous carbon monoxide
Slavnov-Taylor Parameterization for the Quantum Restoration of BRST Symmetries in Anomaly-Free Gauge Theories
It is shown that the problem of the recursive restoration of the
Slavnov-Taylor (ST) identities at the quantum level for anomaly-free gauge
theories is equivalent to the problem of parameterizing the local approximation
to the quantum effective action in terms of ST functionals, associated with the
cohomology classes of the classical linearized ST operator. The ST functionals
of dimension <=4 correspond to the invariant counterterms, those of dimension
>4 generate the non-symmetric counterterms upon projection on the action-like
sector. At orders higher than one in the loop expansion there are additional
contributions to the non-invariant counterterms, arising from known lower order
terms. They can also be parameterized by using the ST functionals. We apply the
method to Yang-Mills theory in the Landau gauge with an explicit mass term
introduced in a BRST-invariant way via a BRST doublet. Despite being
non-unitary, this model provides a good example where the method devised in the
paper can be applied to derive the most general solution for the action-like
part of the quantum effective action, compatible with the fulfillment of the ST
identities and the other relevant symmetries of the model, to all orders in the
loop expansion. The full dependence of the solution on the normalization
conditions is given.Comment: 23 pages. Final version published in the journa
The Most Massive Galaxies at 3.0<z<4.0 in the NEWFIRM Medium-Band Survey: Properties and Improved Constraints on the Stellar Mass Function
[Abridged] We use the NEWFIRM Medium-Band Survey (NMBS) to characterize the
properties of a mass-complete sample of 14 galaxies at 3.0<z<4.0 with
M_star>2.5x10^11 Msun, and to derive more accurate measurements of the
high-mass end of the stellar mass function (SMF) of galaxies at z=3.5, with
significantly reduced contributions from photometric redshift errors and cosmic
variance to the total error budget of the SMF. The typical very massive galaxy
at z=3.5 is red and faint in the observer's optical, with median r=26.1, and
rest-frame U-V=1.6. About 60% of the sample have optical colors satisfying
either the U- or the B-dropout color criteria, although ~50% of these galaxies
have r>25.5. About 30% of the sample has SFRs from SED modeling consistent with
zero. However, >80% of the sample is detected at 24 micron, with total infrared
luminosities in the range (0.5-4.0)x10^13 Lsun. This implies the presence of
either dust-enshrouded starburst activity (with SFRs of 600-4300 Msun/yr)
and/or highly-obscured active galactic nuclei (AGN). The contribution of
galaxies with M_star>2.5x10^11 Msun to the total stellar mass budget at z=3.5
is ~8%. We find an evolution by a factor of 2-7 and 3-22 from z~5 and z~6,
respectively, to z=3.5. The previously found disagreement at the high-mass end
between observed and model-predicted SMFs is now significant at the 3sigma
level. However, systematic uncertainties dominate the total error budget, with
errors up to a factor of ~8 in the densities, bringing the observed SMF in
marginal agreement with the predicted SMF. Additional systematic uncertainties
on the high-mass end could be introduced by either 1) the intense
star-formation and/or the very common AGN activities as inferred from the MIPS
24 micron detections, and/or 2) contamination by a significant population of
massive, old, and dusty galaxies at z~2.6.Comment: 20 pages, 11 figures. Accepted in ApJ. Minor changes to colors of
figures to match accepted versio
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