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

Spatio-temporal variability of micro-, nano- and pico-phytoplankton in the Mediterranean Sea from satellite ocean colour data of SeaWiFS

Abstract. The seasonal and year-to-year variability of the phytoplankton size class (PSC) spatial distribution has been examined in the Mediterranean Sea by using the entire time series of Sea-viewing Wide Field-of-view Sensor (SeaWiFS) space observations (1998–2010). Daily maps of PSCs have been determined using an empirical model based on a synoptic relationship between surface chlorophyll a and diagnostic pigments referred to different taxonomic groups. The analysis of micro-, nano- and pico-phytoplankton satellite time series (1998–2010) describes, quantitatively, the algal assemblage structure over the basin and reveals that the main contribution to chlorophyll a in most of the Mediterranean Sea comes from the pico-phytoplankton component, especially in nutrient-poor environments. Regions with different and peculiar features are the Northwestern Mediterranean Sea, the Alborán Sea and several coastal areas, such as the North Adriatic Sea. In these areas, local interactions between physical and biological components modulate the composition of the three phytoplankton size classes. It results that, during the spring bloom season, micro-phytoplankton dominates in areas of intense vertical winter mixing and deep/intermediate water formation, while in coastal areas micro-phytoplankton dominates in all seasons because of the nutrient supply from the terrestrial inputs. In the Alborán Sea, where the Atlantic inflow modulates the nutrient availability, any predominance of one class over the other two has been observed. The nano-phytoplankton component instead remains widespread over the entire basin along the year, and its contribution to chlorophyll a is of the order of 30–40 %. The largest inter-annual signal occurs in the Northwestern Mediterranean Sea, driven by the year-to-year variation in intensity and extension of the spring bloom, followed by the Alborán Sea, in which the inter-annual variability is strongly modulated by the Atlantic inflow. In absence of sufficient in situ data of community composition, the satellite-based analysis demonstrated that pico-, nano- and micro-phytoplankton classes often coexist. The predominance of one group over the other ones is strongly dependent on the physical and biological processes occurring at the mesoscale. These processes directly influence the nutrient and light availability, which are the principal forcing for the algae growth

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

Corona Virus Disease 19 (CoViD-19) impact on cardiovascular disease in a non-CoViD-19 emergency setting

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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

Discovery of a Thirty-Degree Long Ultraviolet Arc in Ursa Major

Our view of the interstellar medium of the Milky Way and the universe beyond is affected by the structure of the local environment in the Solar neighborhood. Here, we present the discovery of a thirty-degree long arc of ultraviolet emission with a thickness of only a few arcminutes: the Ursa Major Arc. It consists of several arclets seen in the near- and far-ultraviolet bands of the GALEX satellite. A two-degree section of the arc was first detected in the H{\alpha} optical spectral line in 1997; additional sections were seen in the optical by the team of amateur astronomers included in this work. This direction of the sky is known for very low hydrogen column density and dust extinction; many deep fields for extra-galactic and cosmological investigations lie in this direction. Diffuse ultraviolet and optical interstellar emission are often attributed to scattering of light by interstellar dust. The lack of correlation between the Ursa Major Arc and thermal dust emission observed with the Planck satellite, however, suggests that other emission mechanisms must be at play. We discuss the origin of the Ursa Major Arc as the result of an interstellar shock in the Solar neighborhood.Comment: Accepted by A&A on April 3, 202