Fractal Cosmology in an Open Universe

The clustering of galaxies is well characterized by fractal properties, with the presence of an eventual cross-over to homogeneity still a matter of considerable debate. In this letter we discuss the cosmological implications of a fractal distribution of matter, with a possible cross-over to homogeneity at an undetermined scale R_{homo}. Contrary to what is generally assumed, we show that, even when R_{homo} -> \infty, this possibility can be treated consistently within the framework of the expanding universe solutions of Friedmann. The fractal is a perturbation to an open cosmology in which the leading homogeneous component is the cosmic background radiation (CBR). This cosmology, inspired by the observed galaxy distributions, provides a simple explanation for the recent data which indicate the absence of deceleration in the expansion (q_o \approx 0). Correspondingly the `age problem' is also resolved. Further we show that the model can be extended back from the curvature dominated arbitrarily deep into the radiation dominated era, and we discuss qualitatively the modifications to the physics of the anisotropy of the CBR, nucleosynthesis and structure formation.Comment: 7 pages, no figures, to appear in Europhysics Letter

Gravitational clustering in N-body simulations

In this talk we discuss some of the main theoretical problems in the understanding of the statistical properties of gravity. By means of N-body simulations we approach the problem of understanding the r\^ole of gravity in the clustering of a finite set of N-interacting particles which samples a portion of an infinite system. Through the use of the conditional average density, we study the evolution of the clustering for the system putting in evidence some interesting and not yet understood features of the process.Comment: 5 pages, 1 figur

Polycyclic Aromatic Hydrocarbons Pollution in a Coastal Environment: the Statistical Analysis of Dependence to Estimate the Source of Pollution

Polycyclic Aromatic Hydrocarbons (PAHs) are a group of carcinogenic contaminants widespread in the environment. PAHs are produced by both anthropogenic and natural processes. Difficulties exist in identifying their origins. This paper reports a practical application of Principal Component Analysis (PCA) and Principal Component Regression (PCR) to identify the pyrolytic, petrogenic and diagenesis sources of PAH pollution in the Sarno River and Estuary. Nicknamed "the most polluted river in Europe", the Sarno River originates in south-western Italy and has a watershed of about 715 km(2). PCA indicated that the PAH contamination in the Sarno River and Estuary resulted from a mixed pattern. The first principal component (PC1) had significant positive loading in high molecular weight PAHs. This profile of PAH usually includes products of high temperature combustion/pyrolitic processes, reflecting the effects of traffic pyrolysis. The second principal component (PC2) had significant positive loading in two-to-four ring PAHs. So, PC2 may be considered as components from petrogenic sources. PC3 was characterized by a high loading of perylene, thought to originate from diagenetic alteration of perylenequinone pigment or some other organic matter. Therefore, this factor can be considered as natural-origin PAHs. In the PCR, the regression coefficients for components 1-3 were 66.6, 40.4 and 19.5, respectively. In this application, the PCR was a very useful statistical technique for handling the problem of multicollinearity. Results from the application of PCR have been compared with Partial Least Square (PLS) and no significant differences were reported in the prediction errors and latent variables available by PCR and PLS

Clustering in N-Body gravitating systems

Self-gravitating systems have acquired growing interest in statistical mechanics, due to the peculiarities of the 1/r potential. Indeed, the usual approach of statistical mechanics cannot be applied to a system of many point particles interacting with the Newtonian potential, because of (i) the long range nature of the 1/r potential and of (ii) the divergence at the origin. We study numerically the evolutionary behavior of self-gravitating systems with periodical boundary conditions, starting from simple initial conditions. We do not consider in the simulations additional effects as the (cosmological) metric expansion and/or sophisticated initial conditions, since we are interested whether and how gravity by itself can produce clustered structures. We are able to identify well defined correlation properties during the evolution of the system, which seem to show a well defined thermodynamic limit, as opposed to the properties of the ``equilibrium state''. Gravity-induced clustering also shows interesting self-similar characteristics.Comment: 6 pages, 5 figures. To be published on Physica

Prevalence and molecular characterization of Aereomonas spp. in ready-to-eat foods in Italy

A survey was carried out in Italy to ascertain the prevalence of Aeromonas spp. in ready-to-eat foods (vegetables, cheeses, meat products, and ice creams) and the level of molecular heterogeneity of the isolates found by macrorestriction analysis of genomic DNA with pulsed-field gel electrophoresis (PFGE). In total, 46 (14.4%) of the 320 food samples examined were found positive for Aeromonas spp. The highest percentages of isolation were discovered in vegetables, particularly lettuce (45.0%), endive (40.0%), and rucola (20.0%). Ricotta was the only cheese type analyzed that showed a high frequency of isolation (45.0%). Among meat products, salami and raw ham (25.0% of samples positive) and, to a lesser extent, baloney (5.0%) were found positive for Aeromonas spp. Aeromonas hydrophila was the most common isolate from foods of animal origin, whereas Aeromonas caviae was the dominant species in vegetables. No motile aeromonads were found in ice cream samples. Aeromonas isolates showed a high level of genetic heterogeneity, because 24 PFGE patterns were identified among 27 A. hydrophila strains and 20 PFGE patterns were found in 23 A. caviae isolates. In conclusion, consumers of ready-to-eat foods in Italy are regularly exposed to many genetically distinct strains of A. hydrophila and A. caviae without evident signs of malaise, and therefore, few of these strains, if any, are likely to be pathogenic

Evaluation of the environmental monitoring’s effects on the anaesthetic gases concentrations in the operating theatres

In this study the microbiological, physical and chemical results of an investigation concerning the environmental conditions of operating theatres in 38 public hospitals of the Campania Government are presented. The analysis of the results has been made by considering specific standards suggested by national and international regulations. The results showed that 84% of the operating theatres presented normal microbiological values, in relation to the total bacterial load, while 16% did not. By considering the microclimatic monitoring 55% of the operating theatres showed normal values while 45% at least a microclimatic index did not. In relation to the concentrations of anaesthetics gases the survey pointed out that the nitrous oxides was within non prescribed environmental limits (50 ppm for N2O); while 15% of the halogenated was not in normal values

On the kinematic detection of accreted streams in the Gaia era: a cautionary tale

The $\Lambda$CDM cosmological scenario predicts that our Galaxy should contain hundreds of stellar streams at the solar vicinity, fossil relics of the merging history of the Milky Way and more generally of the hierarchical growth of galaxies. Because of the mixing time scales in the inner Galaxy, it has been claimed that these streams should be difficult to detect in configuration space but can still be identifiable in kinematic-related spaces like the energy/angular momenta spaces, E-Lz and Lperp-Lz, or spaces of orbital/velocity parameters. By means of high-resolution, dissipationless N-body simulations, containing between 25$\times10^6$ and 35$\times10^6$ particles, we model the accretion of a series of up to four 1:10 mass ratio satellites then up to eight 1:100 satellites and we search systematically for the signature of these accretions in these spaces. In all spaces considered (1) each satellite gives origin to several independent overdensities; (2) overdensities of multiple satellites overlap; (3) satellites of different masses can produce similar substructures; (4) the overlap between the in-situ and the accreted population is considerable everywhere; (5) in-situ stars also form substructures in response to the satellite(s) accretion. These points are valid even if the search is restricted to kinematically-selected halo stars only. As we are now entering the 'Gaia era', our results warn that an extreme caution must be employed before interpreting overdensities in any of those spaces as evidence of relics of accreted satellites. Reconstructing the accretion history of our Galaxy will require a substantial amount of accurate spectroscopic data, that, complemented by the kinematic information, will possibly allow us to (chemically) identify accreted streams and measure their orbital properties. (abridged)Comment: Accepted on A&A. A high-resolution version of the paper is available at http://aramis.obspm.fr/~paola/ELZ/Elz.pd

Healthcare personnel and hand decontamination in intensive care units: Knowledge, attitudes, and behaviour in Italy

The purpose of this study was to evaluate knowledge, attitudes, and behaviour regarding hand decontamination in personnel of intensive care units (ICUs) in Italy. All ICU physicians and nurses in 19 and five randomly selected hospitals in Campania and Calabria (Italy) were mailed a questionnaire focusing on demographics and practice characteristics; knowledge about prevention of hospital acquired infection; attitudes and behaviour with respect to hand decontamination; and use of gloves. A total of 413 questionnaires were returned giving a response rate of 66.6%. Overall, 53.2% agreed with the correct responses on knowledge related to infection control, and this knowledge was significantly higher in neonatal and medicine-surgery wards and in larger ICUs. A positive attitude was reported by the large majority who agreed that hand decontamination reduces the risk of infection in patients (96.8%) and personnel (86.2%), and the positive attitude was significantly higher among older and female personnel and in those with a higher level of knowledge. Only 60% always decontaminate hands at the start of a shift, and 72.5% before and after a patient contact. Higher compliance is reported for invasive manoeuvres, such as urinary catheters (96.5%) and intravenous lines (77.1%). Routine hand decontamination between each patient was significantly higher in females, and in neonatal and medicine-surgery ICUs. Our results suggest that interventions should not only be focused on predisposing factors (knowledge), but also on enabling (facilitating) and reinforcing (gratifying) factors