7,441 research outputs found
Determining the Gamma-Ray Burst Rate as a Function of Redshift
We exploit the 14 gamma-ray bursts (GRBs) with known redshifts z and the 7
GRBs for which there are constraints on z to determine the GRB rate R_{GRB}(z),
using a method based on Bayesian inference. We find that, despite the
qualitative differences between the observed GRB rate and estimates of the SFR
in the universe, current data are consistent with R_{GRB}(z) being proportional
to the SFR.Comment: To appear in Procs. of Gamma-Ray Bursts in the Afterglow Era: 2nd
Workshop, 3 pages, 3 figures, LaTe
Determining the GRB (Redshift, Luminosity)-Distribution Using Burst Variability
We use the possible Cepheid-like luminosity estimator for the long-duration gamma-ray bursts (GRBs) developed by Reichart et al. (2000) to estimate the intrinsic luminosity, and thus the redshift, of 907 long-duration GRBs from the BATSE 4B catalog. We describe a method based on Bayesian inference which allows us to infer the intrinsic GRB burst rate as a function of redshift for bursts with estimated intrinsic luminosities and redshifts. We apply this method to the above sample of long-duration GRBs, and present some preliminary results
An inhibitory effect of D-Mannoheptulose on lactate formation in human whole blood in vitro
NumeraciĂłn errĂłnea en el original
Consolidation of sugaring marble by hydroxyapatite: some recent developments on producing and treating decayed samples
Consolidation of sugaring marble (i.e., marble affected by granular disaggregation) still lacks fully effective solutions. Consequently, the use of an innovative phosphate-based treatment, aimed at bonding calcite grains by formation of hydroxyapatite at grain boundaries, has recently been proposed. In this paper, firstly a novel method for producing artificially decayed marble samples, by contact with a heating plate, is proposed. Then, some results are presented about the effectiveness and the compatibility of two different formulations of the phosphate treatment, differing in terms of concentration of the phosphate precursor (3.0 M or 0.1 M aqueous solutions of diammonium hydrogen phosphate, DAP), possible ethanol addition to the DAP solution and number of DAP solution applications (1 or 2). The results of the study point out that the new weathering method allows to obtain specimens with a gradient in microstructural and mechanical properties with thickness, just like naturally weathered samples. Both phosphate treatments were able to significantly improve marble cohesion, without causing significant changes in thermal behaviour and aesthetic appearance after treatment. The addition of small quantities of ethanol to the DAP solution seems to be a very promising method for favouring HAP formation and improving the treatment performance
Statistical Analysis of Spectral Line Candidates in Gamma-Ray Burst GRB870303
The Ginga data for the gamma-ray burst GRB870303 exhibit low-energy dips in
two temporally distinct spectra, denoted S1 and S2. S1, spanning 4 s, exhibits
a single line candidate at ~ 20 keV, while S2, spanning 9 s, exhibits
apparently harmonically spaced line candidates at ~ 20 and 40 keV. We evaluate
the statistical evidence for these lines, using phenomenological continuum and
line models which in their details are independent of the distance scale to
gamma-ray bursts. We employ the methodologies based on both frequentist and
Bayesian statistical inference that we develop in Freeman et al. (1999b). These
methodologies utilize the information present in the data to select the
simplest model that adequately describes the data from among a wide range of
continuum and continuum-plus-line(s) models. This ensures that the chosen model
does not include free parameters that the data deem unnecessary and that would
act to reduce the frequentist significance and Bayesian odds of the
continuum-plus-line(s) model. We calculate the significance of the
continuum-plus-line(s) models using the Chi-Square Maximum Likelihood Ratio
test. We describe a parametrization of the exponentiated Gaussian absorption
line shape that makes the probability surface in parameter space
better-behaved, allowing us to estimate analytically the Bayesian odds. The
significance of the continuum-plus-line models requested by the S1 and S2 data
are 3.6 x 10^-5 and 1.7 x 10^-4 respectively, with the odds favoring them being
114:1 and 7:1. We also apply our methodology to the combined (S1+S2) data. The
significance of the continuum-plus-lines model requested by the combined data
is 4.2 x 10^-8, with the odds favoring it being 40,300:1.Comment: LaTeX2e (aastex.cls included); 41 pages text, 10 figures (on 11
pages); accepted by ApJ (to be published 1 Nov 1999, v. 525
Debris Cloud Evolution: Mathematical Modeling and Application to Satellite Constellation Design
Orbital break-ups produce a large number of fragments, which constitute an obvious hazard
for other satellites in nearby orbits. Of these fragments, many are too small to be detected by ground-based
facilities: this leads to the need for mathematical modelling as a tool for adequate risk analysis. In this
paper an average spatial density model is presented. It is based on the Gauss analogy and, for unperturbed
Keplerian orbits, it matches the asymptotic density model developed by other authors.
Risk analysis for satellite constellations is an interesting application of debris cloud evolution models:
the survivability of a constellation as a whole following the break-up of one of its satellites is obviously
of primary concern in the constellation design. Risk analysis is conducted over a number of traditional
configurations in order to achieve an additional constraint on the design parameters. Results indicate the
remarkable influence of the fragmentation point position along the orbit; moreover, the higher risk for
low orbit and the advantage of placing more satellites on a limited number of planes are assessed
On-going development of five geochemical monitoring technologies for onshore CCS
A critical aspect of Carbon Capture and Storage (CCS) will be the ability to adequately monitor the injection site, both to ensure public and environmental safety and for “carbon credit auditing”. In the unlikely event of a leakage in the near-surface environment, the study of natural CO2 emanations in volcanic and geothermal environments have shown that the gas will tend to migrate along the path of least resistance and create spatially restricted “hotspot” leaks at the ground surface that can be challenging to find and quantify. For this reason, innovative technologies are required to improve our ability to detect, locate and characterize such features. To address this need our group is developing geochemical monitoring tools that confront the significant challenges associated with spatial, analytical and temporal resolution and sensitivity. Here we describe on-going work focused on increasing the Technology Readiness Level (TRL) of five prototypes and concepts developed by the Tectonics and Fluid Chemistry Lab (TFCL) at Sapienza University of Rome: the GasPro, Mapper, Multipla, Well-Star, and SWiM systems
Blood and sputum biomarkers in COPD and asthma: a review
Chronic obstructive pulmonary disease (COPD) and asthma are lung inflammatory diseases that represent major public health problems. The primary, and often unique, method to evaluate lung function is spirometry, which reflects disease severity rather than disease activity. Moreover, its measurements strictly depend on patient's compliance, physician's expertise and data interpretation. The limitations of clinical history and pulmonary function tests have encouraged focusing on new possible tracers of diseases. The increase of the inflammatory response in the lungs represents an early pathological event, so biological markers related to inflammation may play key roles in earlier diagnosis, evaluation of functional impairment and prognosis. Biomarkers are measurable indicators associated with the presence and/or severity of a biological or pathogenic process, which may predict functional impairment, prognosis and response to therapy. The traditional approach based on invasive techniques (bronchoalveolar lavage and biopsies) may be replaced, at least in part, by using less invasive methods to collect specimens (sputum and blood), in which biomarkers could be measured. Proteomics, by the association between different protein profiles and pathogenic processes, is gaining an important role in pulmonary medicine allowing a more precise discrimination between patients with different outcomes and response to therapy. The aim of this review was to evaluate the use of biomarkers of airway inflammation in the context of both research and clinical practice
On-going and future research at the Sulcis site in Sardinia, Italy. Characterization and experimentation at a possible future CCS pilot
National Italian funding has recently been allocated for the construction of a 350 MWe coal-fired power plant / CCS
demonstration plant in the Sulcis area of SW Sardinia, Italy. In addition, the recently approved EC-funded ENOS project
(ENabling Onshore CO2 Storage in Europe) will use the Sulcis site as one of its main field research laboratories. Site
characterization is already ongoing, and work has begun to design gas injection experiments at 100-200 m depth in a fault. This
article gives an overview of results to date and plans for the future from the Sapienza University of Rome research group
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