714 research outputs found
An improved model of vector mesons in holographic QCD
We analyze the sector of dimension-three vector meson operators in the "hard
wall" model of holographic QCD, including the vector and axial currents, dual
to gauge fields in the bulk, and the tensor operator
, dual to a two-form field satisfying a complex
self-duality condition. The model includes the effect of chiral symmetry
breaking on vector mesons, that involves a coupling between the dual gauge
field and the two-form field. We compute the leading logarithmic terms in the
operator product expansion of two-point functions and the leading
non-perturbative contribution to the tensor-vector correlator. The result is
consistent with the operator product expansion of QCD. We also study the
spectrum of vector mesons numerically.Comment: 19 page
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Modern tools to evaluate and optimize fire protection systems
Modern techniques, such as fault tree analysis, can be used to obtain engineering descriptions of specific fire protection systems. The analysis allows establishment of an optimum level of fire protection, and evaluates the level of protection provided by various systems. A prime example: the application to fusion energy experiments
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Example of predictive rather than responsive safety research for fusion energy experiments
A fault tree analysis (FTA) was used to study the fire-management systems of two LLL fusion experiments (2XIIB and SHIVA). This technique identified failure modes of existing system components and indicated what the effects of component failure might be in the event of fire in the protected spaces. This paper describes the results of the initial analytical phase of the project and indicates critical unknown parameters required for further analysis. Moreover, the analytical procedures developed are applicable to most, if not all, safety disciplines and could serve as a basis for the logical reestablishment of the FL/SCC by DOE. (MOW
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Experimental and theoretical study of flame inhibition by bromine-containing compounds
The present paper represents the first effort to date in which a combined experimental and theoretical approach has been used to study the effects of several inhibitors on hydrocarbon-air flames. This work is part of an attempt to build a consistent picture of chemical kinetic flame inhibition, beginning with a simple halogen molecule such as HBr and progressing sequentially towards more complex and more practical inhibitors such as CF/sub 3/Br. Inhibition efficiency can be defined as the rate of flame speed reduction, the amount of flame speed change per unit inhibitor added. Both the numerical model and the flame tube measurements found that the inhibition efficiency gradually decreases as the amount of inhibitor is increased. The present experimental and modeling results are shown, together with earlier data for CF/sub 3/Br-CH/sub 4/-air and CF/sub 3/Br-C/sub 3/H/sub 8/-air as well as HBr-CH/sub 4/-air, CH/sub 3/Br-CH/sub 4/-air and CF/sub 3/Br-CH/sub 4/-air. In the numerical study it was found that a stoichiometric methane-air mixture with up to 8% methyl bromide could support a flame, propagating at a speed of about 5 cm/sec, even though the addition of the first 1% of CH/sub 3/Br had reduced the flame speed from 38 cm/sec to about 26 cm/sec. Extensions of the model to include CF/sub 3/Br are currently under development. The available experimental data suggest that CF/sub 3/Br is somewhat more efficient as an inhibitor than HBr or CH/sub 3/Br
Characterizing the Interplay Between Autism Spectrum Disorder and Comorbid Medical Conditions: An Integrative Review
Co-occurring medical disorders and associated physiological abnormalities in individuals with autism spectrum disorder (ASD) may provide insight into causal pathways or underlying biological mechanisms. Here, we review medical conditions that have been repeatedly highlighted as sharing the strongest associations with ASD—epilepsy, sleep, as well as gastrointestinal and immune functioning. We describe within each condition their prevalence, associations with behavior, and evidence for successful treatment. We additionally discuss research aiming to uncover potential aetiological mechanisms. We then consider the potential interaction between each group of conditions and ASD and, based on the available evidence, propose a model that integrates these medical comorbidities in relation to potential shared aetiological mechanisms. Future research should aim to systematically examine the interactions between these physiological systems, rather than considering these in isolation, using robust and sensitive biomarkers across an individual's development. A consideration of the overlap between medical conditions and ASD may aid in defining biological subtypes within ASD and in the development of specific targeted interventions
Caracterização de frutos de progênies de meios-irmãos de maracujazeiro-amarelo em Rio Branco-Acre.
O presente estudo teve como objetivo avaliar e caracterizar 39 progênies de meios-irmãos de maracujazeiro-amarelo para subsidiar o programa de melhoramento genético desta cultura. O delineamento experimental foi em blocos casualizados, com 39 tratamentos (39 progênies de meios-irmãos), com 2 repetições e 5 plantas por parcela. As avaliações foram feitas no segundo ano de produção. As características avaliadas foram: comprimento e diâmetro do fruto, relação comprimento/diâmetro, massa do fruto, da casca e da polpa, rendimento da polpa (arilo + sementes), espessura da casca, acidez titulável, teor de sólidos solúveis e relação sólidos solúveis /acidez titulável. Com base nas características físico-químicas dos frutos, foi possível fazer uma caracterização das 39 progênies de meios-irmãos avaliadas. Os frutos das progênies 3; 27 e 39 apresentam características desejáveis para o mercado in natura, enquanto os das progênies 9; 10; 16; 17; 32 e 38 têm características importantes para o processamento
Combination of a mitogen‐activated protein kinase inhibitor with the tyrosine kinase inhibitor pacritinib combats cell adhesion‐based residual disease and prevents re‐expansion of FLT3 ‐ITD acute myeloid leukaemia
Minimal residual disease (MRD) in acute myeloid leukaemia (AML) poses a major challenge due to drug insensitivity and high risk of relapse. Intensification of chemotherapy and stem cell transplantation are often pivoted on MRD status. Relapse rates are high even with the integration of first‐generation FMS‐like tyrosine kinase 3 (FLT3) inhibitors in pre‐ and post‐transplant regimes and as maintenance in FLT3 ‐mutated AML. Pre‐clinical progress is hampered by the lack of suitable modelling of residual disease and post‐therapy relapse. In the present study, we investigated the nature of pro‐survival signalling in primary residual tyrosine kinase inhibitor (TKI)‐treated AML cells adherent to stroma and further determined their drug sensitivity in order to inform rational future therapy combinations. Using a primary human leukaemia‐human stroma model to mimic the cell–cell interactions occurring in patients, the ability of several TKIs in clinical use, to abrogate stroma‐driven leukaemic signalling was determined, and a synergistic combination with a mitogen‐activated protein kinase (MEK) inhibitor identified for potential therapeutic application in the MRD setting. The findings reveal a common mechanism of stroma‐mediated resistance that may be independent of mutational status but can be targeted through rational drug design, to eradicate MRD and reduce treatment‐related toxicity
The Baryonic Phase in Holographic Descriptions of the QCD Phase Diagram
We study holographic models of the QCD temperature-chemical potential phase
diagram based on the D3/D7 system with chiral symmetry breaking. The baryonic
phase may be included through linked D5-D7 systems. In a previous analysis of a
model with a running gauge coupling a baryonic phase was shown to exist to
arbitrarily large chemical potential. Here we explore this phase in a more
generic phenomenological setting with a step function dilaton profile. The
change in dilaton generates a linear confining potential and opposes
the screening effect of temperature. We show that the persistence of the
baryonic phase depends on the step size and that QCD-like phase diagrams can be
described. The baryonic phase's existence is qualitatively linked to the
existence of confinement in Wilson loop computations in the background.Comment: 21 pages, 7 figure
Holography of a Composite Inflaton
We study the time evolution of a brane construction that is holographically
dual to a strongly coupled gauge theory that dynamically breaks a global
symmetry through the generation of an effective composite Higgs vev. The D3/D7
system with a background magnetic field or non-trivial gauge coupling (dilaton)
profile displays the symmetry breaking. We study motion of the D7 brane in the
background of the D3 branes. For small field inflation in the field theory the
effective Higgs vev rolls from zero to the true vacuum value. We study what
phenomenological dilaton profile generates the slow rolling needed, hence
learning how the strongly coupled gauge theory's coupling must run. We note
that evolution of our configuration in the holographic direction, representing
the phyiscs of the strong interactions, can provide additional slowing of the
roll time. Inflation seems to be favoured if the coupling changes by only a
small amount or very gently. We speculate on how such a scenario could be
realized away from N=4 gauge theory, for example, in a walking gauge theory.Comment: 13 pages, 12 figures; v2: Added reference
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