902 research outputs found
Gauge invariance of parametrized systems and path integral quantization
Gauge invariance of systems whose Hamilton-Jacobi equation is separable is
improved by adding surface terms to the action fuctional. The general form of
these terms is given for some complete solutions of the Hamilton-Jacobi
equation. The procedure is applied to the relativistic particle and toy
universes, which are quantized by imposing canonical gauge conditions in the
path integral; in the case of empty models, we first quantize the parametrized
system called ``ideal clock'', and then we examine the possibility of obtaining
the amplitude for the minisuperspaces by matching them with the ideal clock.
The relation existing between the geometrical properties of the constraint
surface and the variables identifying the quantum states in the path integral
is discussed.Comment: 23 page
C IV BAL disappearance in a large SDSS QSO sample
Broad absorption lines (BALs) in the spectra of quasi-stellar objects (QSOs)
originate from outflowing winds along our line of sight; winds are thought to
originate from the inner regions of the QSO accretion disk, close to the
central supermassive black hole (SMBH). Winds likely play a role in galaxy
evolution and aid the accretion mechanism onto the SMBH. BAL equivalent widths
can change on typical timescales from months to years; such variability is
generally attributed to changes in the covering factor and/or in the ionization
level of the gas. We investigate BAL variability, focusing on BAL
disappearance. We analyze multi-epoch spectra of more than 1500 QSOs -the
largest sample ever used for such a study- observed by different programs from
the Sloan Digital Sky Survey-I/II/III (SDSS), and search for disappearing C IV
BALs. The spectra rest-frame time baseline ranges from 0.28 to 4.9 yr; the
source redshifts range from 1.68 to 4.27. We detect 73 disappearing BALs in the
spectra of 67 sources. This corresponds to 3.9% of disappearing BALs, and 5.1%
of our BAL QSOs exhibit at least one disappearing BAL. We estimate the average
lifetime of a BAL along our line of sight (~ 80-100 yr), which appears
consistent with the accretion disk orbital time at distances where winds are
thought to originate. We inspect properties of the disappearing BALs and
compare them to the properties of our main sample. We also investigate the
existence of a correlation in the variability of multiple troughs in the same
spectrum, and find it persistent at large velocity offsets between BAL pairs,
suggesting that a mechanism extending on a global scale is necessary to explain
the phenomenon. We select a more reliable sample of disappearing BALs following
Filiz Ak et al. (2012), where a subset of our sample was analyzed, and compare
the findings from the two works, obtaining generally consistent results.Comment: 22 pages, 9 figures. Accepted for publication in A&
Role of surgical setting and patients-related factors in predicting the occurrence of postoperative pulmonary complications after abdominal surgery
OBJECTIVE: The aim of this retrospective study was to evaluate the role of surgical setting (urgent vs. elective) and approach (open vs. laparoscopic) in affecting postoperative pulmonary complications (PPCs) prevalence in patients undergoing abdominal surgery.
PATIENTS AND METHODS: After local Ethical Committee approval, 409 patients who had undergone abdominal surgery between January and December 2014 were included in the final analysis. PPCs were defined as the development of one of the following new findings: respiratory failure, pulmonary infection, aspiration pneumonia, pleural effusion, pneumothorax, atelectasis on chest X-ray, bronchospasm or un-planned urgent re-intubation.
RESULTS: PPCs prevalence was greater in urgent (33%) vs. elective setting (7%) (chi(2) with Yates correction: 44; p=0.0001) and in open (6%) vs. laparoscopic approach (1.9%) (chi(2) with Yates correction: 12; p=0.0006). PPCs occurrence was positively correlated with in-hospital mortality (Biserial Correlation r=0.37; p=0.0001). Logistic regression showed that urgent setting (p=0.000), Ariscat (Assess Respiratory Risk in Surgical Patients in Catalonia) score (p=0.004), and age (p=0.01) were predictors of PPCs. A cutoff of 23 for Ariscat score was also identified as determining factor for PPCs occurrence with 94% sensitivity and 29% specificity.
CONCLUSIONS: Patients undergoing abdominal surgery in an urgent setting were exposed to a higher risk of PPCs compared to patients scheduled for elective procedures. Ariscat score fitted with PPCs prevalence and older patients were exposed to a higher risk of PPCs. Prospective studies are needed to confirm these result
River chloride trends in snow-affected urban watersheds: increasing concentrations outpace urban growth rate and are common among all seasons
AbstractChloride concentrations in northern U.S. included in this study have increased substantially over time with average concentrations approximately doubling from 1990 to 2011, outpacing the rate of urbanization in the northern U.S. Historical data were examined for 30 monitoring sites on 19 streams that had chloride concentration and flow records of 18 to 49years. Chloride concentrations in most studied streams increased in all seasons (13 of 19 in all seasons; 16 of 19 during winter); maximum concentrations occurred during winter. Increasing concentrations during non-deicing periods suggest that chloride was stored in hydrologic reservoirs, such as the shallow groundwater system, during the winter and slowly released in baseflow throughout the year. Streamflow dependency was also observed with chloride concentrations increasing as streamflow decreased, a result of dilution during rainfall- and snowmelt-induced high-flow periods. The influence of chloride on aquatic life increased with time; 29% of sites studied exceeded the concentration for the USEPA chronic water quality criteria of 230mg/L by an average of more than 100 individual days per year during 2006–2011. The rapid rate of chloride concentration increase in these streams is likely due to a combination of possible increased road salt application rates, increased baseline concentrations, and greater snowfall in the Midwestern U.S. during the latter portion of the study period
Global phase time and path integral for the Kantowski--Sachs anisotropic univers
The action functional of the anisotropic Kantowski--Sachs cosmological model
is turned into that of an ordinary gauge system. Then a global phase time is
identified for the model by imposing canonical gauge conditions, and the
quantum transition amplitude is obtained by means of the usual path integral
procedure of Fadeev and Popov.Comment: 11 page
Istallazione di una stazione per la rivelazione continua Radon mediante spettrometria alfa nella Solfatara di Pozzuoli
INGV (Istituto Nazionale di Geofisica e Vulcanologia, Sezione di Napoli - Osservatorio Vesuviano)Published1-221.4. TTC - Sorveglianza sismologica delle aree vulcaniche attiveN/A or not JCRrestricte
Optically variable active galactic nuclei in the 3 yr VST survey of the COSMOS field
The analysis of the variability of active galactic nuclei (AGNs) at different
wavelengths and the study of possible correlations among different spectral
windows are nowadays a major field of inquiry. Optical variability has been
largely used to identify AGNs in multivisit surveys. The strength of a
selection based on optical variability lies in the chance to analyze data from
surveys of large sky areas by ground-based telescopes. However the
effectiveness of optical variability selection, with respect to other
multiwavelength techniques, has been poorly studied down to the depth expected
from next generation surveys. Here we present the results of our r-band
analysis of a sample of 299 optically variable AGN candidates in the VST survey
of the COSMOS field, counting 54 visits spread over three observing seasons
spanning > 3 yr. This dataset is > 3 times larger in size than the one
presented in our previous analysis (De Cicco et al. 2015), and the observing
baseline is ~8 times longer. We push towards deeper magnitudes (r(AB) ~23.5
mag) compared to past studies; we make wide use of ancillary multiwavelength
catalogs in order to confirm the nature of our AGN candidates, and constrain
the accuracy of the method based on spectroscopic and photometric diagnostics.
We also perform tests aimed at assessing the relevance of dense sampling in
view of future wide-field surveys. We demonstrate that the method allows the
selection of high-purity (> 86%) samples. We take advantage of the longer
observing baseline to achieve great improvement in the completeness of our
sample with respect to X-ray and spectroscopically confirmed samples of AGNs
(59%, vs. ~15% in our previous work), as well as in the completeness of
unobscured and obscured AGNs. The effectiveness of the method confirms the
importance to develop future, more refined techniques for the automated
analysis of larger datasets.Comment: 21 pages, 10 figures; accepted for publication in A&
Prognostic factors in Krukenberg tumor
BACKGROUND:
Krukenberg tumor (KT) is a rare secondary ovarian tumor. Little is known about clinicopathologic factors affecting prognosis in KT.
OBJECTIVE:
To assess the prognostic value of clinicopathologic factors in KT through a systematic review and meta-analysis.
METHODS:
Electronic databases were searched from their inception to February 2019 for studies assessing the association of clinicopathologic factors with overall survival in KT. Pooled hazard ratio (HR) was calculated for each factor; a p value < 0.05 was considered significant.
RESULTS:
Twenty-three studies with 1743 patients were included. A decreased overall survival was significantly associated with peritoneal involvement (HR 1.944; p = 0.003), ascites (HR 2.055; p = 0.034), synchronous presentation (HR 1.679; p = 0.034) and increased serum CEA levels (HR 1.380; p = 0.010), but not with age > 50 (HR 0.946; p = 0.743), menopausal status (HR 1.565; p = 0.204), gastric origin (HR 1.600; p = 0.201), size > 5 cm (HR 1.292; p = 0.119), size > 10 cm (HR 0.925; p = 0.714), bilateral ovarian involvement (HR 1.113; p = 0.347), non-peritoneal extaovarian metastases (HR 1.648; p = 0.237), liver metastases (HR 1.118, p = 0.555), predominant signet ring cell morphology (HR 1.322; p = 0.208) and levels of CA125 (HR 0.933; p = 0.828) and CA19.9 (HR 0.996; p = 0.992).
CONCLUSION:
Peritoneal involvement, synchronous presentation, ascites and increased serum CEA levels appear as unfavorable prognostic factors in KT and might affect the patient management
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