61 research outputs found
Soft Pomerons and the Forward LHC Data
Recent data from LHC13 by the TOTEM Collaboration on and
have indicated disagreement with all the Pomeron model predictions by
the COMPETE Collaboration (2002). On the other hand, as recently demonstrated
by Martynov and Nicolescu (MN), the new datum and the unexpected
decrease in the value are well described by the maximal Odderon
dominance at the highest energies. Here, we discuss the applicability of
Pomeron dominance through fits to the \textit{most complete set} of forward
data from and scattering. We consider an analytic
parametrization for consisting of non-degenerated Regge
trajectories for even and odd amplitudes (as in the MN analysis) and two
Pomeron components associated with double and triple poles in the complex
angular momentum plane. The parameter is analytically determined by
means of dispersion relations. We carry out fits to and data on
and in the interval 5 GeV - 13 TeV (as in the MN
analysis). Two novel aspects of our analysis are: (1) the dataset comprises all
the accelerator data below 7 TeV and we consider \textit{three independent
ensembles} by adding: either only the TOTEM data (as in the MN analysis), or
only the ATLAS data, or both sets; (2) in the data reductions to each ensemble,
uncertainty regions are evaluated through error propagation from the fit
parameters, with 90 \% CL. We argument that, within the uncertainties, this
analytic model corresponding to soft Pomeron dominance, does not seem to be
excluded by the \textit{complete} set of experimental data presently available.Comment: 10 pages, 4 figures, 1 table. Two paragraphs and four references
added. Accepted for publication in Phys. Lett.
Proton-proton forward scattering at the LHC
Recently the TOTEM experiment at the LHC has released measurements at
TeV of the proton-proton total cross section, ,
and the ratio of the real to imaginary parts of the forward elastic amplitude,
. Since then an intense debate on the -parity asymptotic nature of the
scattering amplitude was initiated. We examine the proton-proton and the
antiproton-proton forward data above 10 GeV in the context of an eikonal
QCD-based model, where nonperturbative effects are readily included via a QCD
effective charge. We show that, despite an overall satisfactory description of
the forward data is obtained by a model in which the scattering amplitude is
dominated by only crossing-even elastic terms, there is evidence that the
introduction of a crossing-odd term may improve the agreement with the
measurements of at TeV. In the Regge language the
dominant even(odd)-under-crossing object is the so called Pomeron (Odderon).Comment: 5 pages, 2 figures, 1 table. Phenomenological approach revised,
results and conclusions changed, suggesting now the presence of Odderon
effects in forward scattering (once confirmed the TOTEM data at 13 TeV
Soft Pomeron in light of the LHC correlated data
The LHC has released precise measurements of elastic proton-proton scattering
that provide a unique constraint on the asymptotic behavior of the scattering
amplitude at high energies. Recent reanalyses of part of these data indicate
that the central values of some forward quantities would be different than
initially observed. We introduce correlation information between the original
and the reanalyzed data sets in a way suitable for a global fitting analysis of
all data. The careful treatment of correlated errors leads to much less
stringent limits on the uncertainty and sets up the stage for describing
the forward data using a scattering amplitude dominated by only crossing-even
terms. In the light of these correlated data we determine the parameters of the
soft Pomeron from the Regge theory. We use Born-level and eikonalized
amplitudes. In the Born-level case we estimate the contribution of the double
Pomeron exchange, while in the latter case we investigate the role of the
eikonalization in both the one- and two-channel models. The role of the
proton-Pomeron vertex form and of the nearest -channel singularity in the
Pomeron trajectory receives particular attention. We discuss the implications
of our results and present predictions for the total cross section and the
parameter in proton-proton collisions at LHC and cosmic ray energies.Comment: 17 pages, 6 figures, 5 tables, minor typos fixed. Version to be
published in Phys. Rev. D. arXiv admin note: text overlap with
arXiv:1908.0104
Medición de impactos en una terraza verde para la definición de estandares de eficiencia en sistemas de techos verdes intensivos y extensivos en condiciones urbanas. Caso de estudio: Ciudad de Córdoba
Una alternativa para moderar el equilibrio en los ecosistemas urbanos e integrar la vegetación a las ciudades, lo constituyen los techos verdes. Dichos sistemas aportan servicios ecosistemicos, como la mitigación de las variaciones de temperatura entre el exterior y el interior de las unidades habitacionales, contribuyendo a la eficiencia energética de las construcciones edilicias. En el presente proyecto de investigación se evalúa la adecuación de esta tecnología a condiciones constructivas reales; como así también el impacto de los dos tipos de sistemas: el extensivo y el intensivo, comparándolos con un techo blanco como testigo. En dos aulas taller contiguas de la facultad de arquitectura se instaló un sistema extensivo de techos verdes (80 m2) y la otra se pintó la loza de blanco (testigo). En el techo del aula testigo se instalaron 3 cubos de simulación de 1 m3 para simular ambos sistemas (extensivo e intensivo) y comparar con el testigo. Se colocaron sensores exteriores, de loza e interiores tanto en ambas aulas como en los cubos, para evaluar la eficiencia energética y en los cubos además, la escorrentía. Se están procesando y analizando los datos recibidos para estimar las propiedades térmicas, las diferencias de temperaturas en los diferentes espacios, así como el impacto energéticode ambos sistemas. Al mismo tiempo se está analizando la detección y detención de la escorrentía de las lluvias recibidas en ese período. Este proyecto permite medir el impacto positivo del techo verde, establecer comparaciones entre sistemas constructivos, y dimensionar la magnitud de algunos de los servicos ecosistémicos que este mismo presta (e.g. regulación térmica, colecta del agua de lluvia, retención y detención de escorrentía, entre otros). La estimación certera de estos beneficios potenciales permitirá la definición de estándares de eficiencia
Why Are Outcomes Different for Registry Patients Enrolled Prospectively and Retrospectively? Insights from the Global Anticoagulant Registry in the FIELD-Atrial Fibrillation (GARFIELD-AF).
Background: Retrospective and prospective observational studies are designed to reflect real-world evidence on clinical practice, but can yield conflicting results. The GARFIELD-AF Registry includes both methods of enrolment and allows analysis of differences in patient characteristics and outcomes that may result. Methods and Results: Patients with atrial fibrillation (AF) and ≥1 risk factor for stroke at diagnosis of AF were recruited either retrospectively (n = 5069) or prospectively (n = 5501) from 19 countries and then followed prospectively. The retrospectively enrolled cohort comprised patients with established AF (for a least 6, and up to 24 months before enrolment), who were identified retrospectively (and baseline and partial follow-up data were collected from the emedical records) and then followed prospectively between 0-18 months (such that the total time of follow-up was 24 months; data collection Dec-2009 and Oct-2010). In the prospectively enrolled cohort, patients with newly diagnosed AF (≤6 weeks after diagnosis) were recruited between Mar-2010 and Oct-2011 and were followed for 24 months after enrolment. Differences between the cohorts were observed in clinical characteristics, including type of AF, stroke prevention strategies, and event rates. More patients in the retrospectively identified cohort received vitamin K antagonists (62.1% vs. 53.2%) and fewer received non-vitamin K oral anticoagulants (1.8% vs . 4.2%). All-cause mortality rates per 100 person-years during the prospective follow-up (starting the first study visit up to 1 year) were significantly lower in the retrospective than prospectively identified cohort (3.04 [95% CI 2.51 to 3.67] vs . 4.05 [95% CI 3.53 to 4.63]; p = 0.016). Conclusions: Interpretations of data from registries that aim to evaluate the characteristics and outcomes of patients with AF must take account of differences in registry design and the impact of recall bias and survivorship bias that is incurred with retrospective enrolment. Clinical Trial Registration: - URL: http://www.clinicaltrials.gov . Unique identifier for GARFIELD-AF (NCT01090362)
Rationale, study design, and analysis plan of the Alveolar Recruitment for ARDS Trial (ART): Study protocol for a randomized controlled trial
Background: Acute respiratory distress syndrome (ARDS) is associated with high in-hospital mortality. Alveolar recruitment followed by ventilation at optimal titrated PEEP may reduce ventilator-induced lung injury and improve oxygenation in patients with ARDS, but the effects on mortality and other clinical outcomes remain unknown. This article reports the rationale, study design, and analysis plan of the Alveolar Recruitment for ARDS Trial (ART). Methods/Design: ART is a pragmatic, multicenter, randomized (concealed), controlled trial, which aims to determine if maximum stepwise alveolar recruitment associated with PEEP titration is able to increase 28-day survival in patients with ARDS compared to conventional treatment (ARDSNet strategy). We will enroll adult patients with ARDS of less than 72 h duration. The intervention group will receive an alveolar recruitment maneuver, with stepwise increases of PEEP achieving 45 cmH(2)O and peak pressure of 60 cmH2O, followed by ventilation with optimal PEEP titrated according to the static compliance of the respiratory system. In the control group, mechanical ventilation will follow a conventional protocol (ARDSNet). In both groups, we will use controlled volume mode with low tidal volumes (4 to 6 mL/kg of predicted body weight) and targeting plateau pressure <= 30 cmH2O. The primary outcome is 28-day survival, and the secondary outcomes are: length of ICU stay; length of hospital stay; pneumothorax requiring chest tube during first 7 days; barotrauma during first 7 days; mechanical ventilation-free days from days 1 to 28; ICU, in-hospital, and 6-month survival. ART is an event-guided trial planned to last until 520 events (deaths within 28 days) are observed. These events allow detection of a hazard ratio of 0.75, with 90% power and two-tailed type I error of 5%. All analysis will follow the intention-to-treat principle. Discussion: If the ART strategy with maximum recruitment and PEEP titration improves 28-day survival, this will represent a notable advance to the care of ARDS patients. Conversely, if the ART strategy is similar or inferior to the current evidence-based strategy (ARDSNet), this should also change current practice as many institutions routinely employ recruitment maneuvers and set PEEP levels according to some titration method.Hospital do Coracao (HCor) as part of the Program 'Hospitais de Excelencia a Servico do SUS (PROADI-SUS)'Brazilian Ministry of Healt
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