879 research outputs found
Probing the time structure of the quark-gluon plasma with top quarks
The tiny droplets of quark gluon plasma (QGP) created in high-energy nuclear collisions experience fast expansion and cooling with a lifetime of a few fm=c. Despite the information provided by probes such as jet quenching and quarkonium suppression, and the excellent description by hydrodynamical models, direct access to the time evolution of the system remains elusive. We point out that the study of hadronically decaying W bosons, notably in events with a top-antitop quark pair, can provide key novel insight into the time structure of the QGP. This is because of a unique feature, namely a time delay between the moment of the collision and that when the W-boson decay products start interacting with the medium. Furthermore, the length of the time delay can be constrained by selecting specific reconstructed top-quark momenta. We carry out a Monte Carlo feasibility study and find that the LHC has the potential to bring first limited information on the time structure of the QGP. Substantially increased LHC heavy-ion luminosities or future higher-energy colliders would open opportunities for more extensive studies
Proceso de construcci?n de una cultura de paz en los ni?os de transici?n de la instituci?n educativa Armando Romero Lozano de Sevilla Valle, a trav?s de estrategias did?cticas sensibilizadoras
121 p. Recurso Electr?nicoEl presente proyecto de investigaci?n ?proceso de construcci?n de una cultura de paz en los ni?os de preescolar, a trav?s de estrategias did?cticas sensibilizadoras? consiste en visibilizar los alcances en la mejora de las habilidades de resoluci?n de conflictos a trav?s de actividades l?dicas y art?sticas en los ni?os de preescolar de Instituci?n Educativa Armando Romero Lozano del municipio de Sevilla valle.
Todo esto se realiz? partiendo del planteamiento de los objetivos, los cuales permitir?n lograr su cometido; en primer lugar, identificar a partir de los resultados qu? problem?ticas de comportamiento tienen los ni?os, en segundo lugar, implementar un plan de intervenci?n orientado a mejorar las relaciones interpersonales de los ni?os y en tercer lugar, evaluar el impacto generado con el plan de intervenci?n propuesto para tal fin.
En cuanto al marco te?rico, se busc? el soporte en los postulados de diferentes autores, los cuales resultaron pertinentes para el abordaje conceptual de este, ya que hablan del desarrollo de la capacidad creadora, principios, normas y valores que hacen un clima escolar acorde para una educaci?n para la paz y una participaci?n democr?tica, como aspectos importantes a tener en cuenta en esta investigaci?n.
Respecto a la metodolog?a, se desarroll? en base a la investigaci?n la investigaci?n acci?n-participativa y cooperativa, con un enfoque etnogr?fico, dentro del paradigma cualitativo. Tras esto, el resultado que se obtendr? del proceso estudiado, que junto a referentes te?ricos ayuda a explicar los procesos de la pr?ctica escolar estudiada.This research project process of building a culture of peace in preschool children through teaching strategies visible sensitizer is the scope in improving the skills of conflict resolution through recreational and artistic activities preschoolers educational institution Armando Romero Lozano the municipality of Seville valley.
All this was done based on the approach of objectives, which will allow achieve its mission; first identified from the results which problematic behavior have children, secondly, implement an intervention plan aimed at improving interpersonal relationships of children and thirdly, to assess the impact generated with the intervention plan proposed for this purpose.
As for the theoretical framework, support the propositions of different authors, which were relevant to the conceptual approach to this is sought, as they speak of the development of creativity, principles, norms and values that make a chord school climate for education for peace and democratic participation, as important aspects to consider in this research.
Reading methodology was developed based on the research-participatory and cooperative action with an ethnographic approach, within the qualitative research paradigm. After this, the result you get the process under study, which together with theoretical framework helps explain the processes studied school practice
Keywords: skills, peace, transition, norms, values and family
Jet coherence in QCD media: the antenna radiation spectrum
We study the radiation of a highly energetic partonic antenna in a colored
state traversing a dense QCD medium. Resumming multiple scatterings of all
involved constituents with the medium we derive the general gluon spectrum
which encompasses both longitudinal color coherence between scattering centers
in the medium, responsible for the well known Landau-Pomeranchuk-Migdal (LPM)
effect, and transverse color coherence between partons inside a jet, leading,
in vacuum, to angular ordering of the parton shower. We discuss shortly the
onset of transverse decoherence which is reached in opaque media. In this
regime, the spectrum consists of independent radiation off the antenna
constituents.Comment: 15 pages, 2 figures, paper shortened and partly rewritten, references
added, results unchange
Infinitesimal Lyapunov functions for singular flows
We present an extension of the notion of infinitesimal Lyapunov function to
singular flows, and from this technique we deduce a characterization of
partial/sectional hyperbolic sets. In absence of singularities, we can also
characterize uniform hyperbolicity.
These conditions can be expressed using the space derivative DX of the vector
field X together with a field of infinitesimal Lyapunov functions only, and are
reduced to checking that a certain symmetric operator is positive definite at
the tangent space of every point of the trapping region.Comment: 37 pages, 1 figure; corrected the statement of Lemma 2.2 and item (2)
of Theorem 2.7; removed item (5) of Theorem 2.7 and its wrong proof since the
statement of this item was false; corrected items (1) and (2) of Theorem 2.23
and their proofs. Included Example 6 on smooth reduction of families of
quadratic forms. The published version in Math Z journal needs an errat
The Gluonic Field of a Heavy Quark in Conformal Field Theories at Strong Coupling
We determine the gluonic field configuration sourced by a heavy quark
undergoing arbitrary motion in N=4 super-Yang-Mills at strong coupling and
large number of colors. More specifically, we compute the expectation value of
the operator tr[F^2+...] in the presence of such a quark, by means of the
AdS/CFT correspondence. Our results for this observable show that signals
propagate without temporal broadening, just as was found for the expectation
value of the energy density in recent work by Hatta et al. We attempt to shed
some additional light on the origin of this feature, and propose a different
interpretation for its physical significance. As an application of our general
results, we examine when the quark undergoes oscillatory motion,
uniform circular motion, and uniform acceleration. Via the AdS/CFT
correspondence, all of our results are pertinent to any conformal field theory
in 3+1 dimensions with a dual gravity formulation.Comment: 1+38 pages, 16 eps figures; v2: completed affiliation; v3: corrected
typo, version to appear in JHE
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The secretome of alginate-encapsulated limbal epithelial stem cells modulates corneal epithelial cell proliferation
Limbal epithelial stem cells may ameliorate limbal stem cell deficiency through secretion of therapeutic proteins, delivered to the cornea in a controlled manner using hydrogels. In the present study the secretome of alginate-encapsulated limbal epithelial stem cells is investigated. Conditioned medium was generated from limbal epithelial stem cells encapsulated in 1.2% (w/v) calcium alginate gels. Conditioned medium proteins separated by 1-D gel electrophoresis were visualized by silver staining. Proteins of interest including secreted protein acidic and rich in cysteine, profilin-1, and galectin-1 were identified by immunoblotting. The effect of conditioned medium (from alginate-encapsulated limbal epithelial stem cells) on corneal epithelial cell proliferation was quantified and shown to significantly inhibit (P</=0.05) their growth. As secreted protein acidic and rich in cysteine was previously reported to attenuate proliferation of epithelial cells, this protein may be responsible, at least in part, for inhibition of corneal epithelial cell proliferation. We conclude that limbal epithelial stem cells encapsulated in alginate gels may regulate corneal epithelialisation through secretion of inhibitory proteins
Systemic inflammatory response syndrome in adult patients with nosocomial bloodstream infections due to enterococci
BACKGROUND: Enterococci are the third leading cause of nosocomial bloodstream infection (BSI). Vancomycin resistant enterococci are common and provide treatment challenges; however questions remain about VRE's pathogenicity and its direct clinical impact. This study analyzed the inflammatory response of Enterococcal BSI, contrasting infections from vancomycin-resistant and vancomycin-susceptible isolates. METHODS: We performed a historical cohort study on 50 adults with enterococcal BSI to evaluate the associated systemic inflammatory response syndrome (SIRS) and mortality. We examined SIRS scores 2 days prior through 14 days after the first positive blood culture. Vancomycin resistant (n = 17) and susceptible infections (n = 33) were compared. Variables significant in univariate analysis were entered into a logistic regression model to determine the affect on mortality. RESULTS: 60% of BSI were caused by E. faecalis and 34% by E. faecium. 34% of the isolates were vancomycin resistant. Mean APACHE II (A2) score on the day of BSI was 16. Appropriate antimicrobials were begun within 24 hours in 52%. Septic shock occurred in 62% and severe sepsis in an additional 18%. Incidence of organ failure was as follows: respiratory 42%, renal 48%, hematologic 44%, hepatic 26%. Crude mortality was 48%. Progression to septic shock was associated with death (OR 14.9, p < .001). There was no difference in A2 scores on days -2, -1 and 0 between the VRE and VSE groups. Maximal SIR (severe sepsis, septic shock or death) was seen on day 2 for VSE BSI vs. day 8 for VRE. No significant difference was noted in the incidence of organ failure, 7-day or overall mortality between the two groups. Univariate analysis revealed that AP2>18 at BSI onset, and respiratory, cardiovascular, renal, hematologic and hepatic failure were associated with death, but time to appropriate therapy >24 hours, age, and infection due to VRE were not. Multivariate analysis revealed that hematologic (OR 8.4, p = .025) and cardiovascular failure (OR 7.5, p = 032) independently predicted death. CONCLUSION: In patients with enterococcal BSI, (1) the incidence of septic shock and organ failure is high, (2) patients with VRE BSI are not more acutely ill prior to infection than those with VSE BSI, and (3) the development of hematologic or cardiovascular failure independently predicts death
Early-Time Energy Loss in a Strongly-Coupled SYM Plasma
We carry out an analytic study of the early-time motion of a quark in a
strongly-coupled maximally-supersymmetric Yang-Mills plasma, using the AdS/CFT
correspondence. Our approach extracts the first thermal effects as a small
perturbation of the known quark dynamics in vacuum, using a double expansion
that is valid for early times and for (moderately) ultrarelativistic quark
velocities. The quark is found to lose energy at a rate that differs
significantly from the previously derived stationary/late-time result: it
scales like T^4 instead of T^2, and is associated with a friction coefficient
that is not independent of the quark momentum. Under conditions representative
of the quark-gluon plasma as obtained at RHIC, the early energy loss rate is a
few times smaller than its late-time counterpart. Our analysis additionally
leads to thermally-corrected expressions for the intrinsic energy and momentum
of the quark, in which the previously discovered limiting velocity of the quark
is found to appear naturally.Comment: 39 pages, no figures. v2: Minor corrections and clarifications.
References added. Version to be published in JHE
photoproduction on the proton for photon energies from 0.725 to 2.875 GeV
Differential cross sections for the reaction have been
measured with the CEBAF Large Acceptance Spectrometer (CLAS) and a tagged
photon beam with energies from 0.725 to 2.875 GeV. Where available, the results
obtained here compare well with previously published results for the reaction.
Agreement with the SAID and MAID analyses is found below 1 GeV. The present set
of cross sections has been incorporated into the SAID database, and exploratory
fits have been made up to 2.7 GeV. Resonance couplings have been extracted and
compared to previous determinations. With the addition of these cross sections
to the world data set, significant changes have occurred in the high-energy
behavior of the SAID cross-section predictions and amplitudes.Comment: 18 pages, 10 figure
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