Area classification for explosive atmospheres: comparison between European and North American approaches

The object of this paper is to review various methods of determining the extent of hazardous areas in industrial facilities where explosive gas or vapor atmospheres may be present. Three different approaches are analyzed and compared. The first one is recommended in North American Standards, such as API500, API505 and NFPA 497. The second is one of the proposals for the second edition of the International Standard IEC 60079-10-1 (adopted as European standard EN 60079-10-1). The third approach had been previously worked out with the authors‘ contribution and had been adopted by the Italian Guide CEI 31-35 since 2001. The last two approaches are analytical, meanwhile the first one is prescriptive. In the second part of the paper both analytical approaches are applied to the releases which are analyzed in NFPA 497 as practical examples. Resulting hazardous area extents are compared and the differences among the three methods are discusse

Hazardous areas extension in explosive atmospheres caused by free gas jets

This paper regards the validation procedure of the Italian Guide CEI 31-35 formula, used to calculate the hazardous areas extensions in places where explosive gas atmospheres may be present. In industrial activity, a typical event which cause explosive atmosphere consists of damaging and leakage from unions, gaskets, valves of pipes and vessels. At this purpose, in this work it has been taken into account the accidental discharge of flammable gas into a quiescent atmosphere through an orifice. Validation has been performed by comparing calculated values with experimental data. Two gases have been taken into account: methane and hydrogen. Different scenarios have been analyzed, each one differing from the others in the gas release cross section and in the vessel pressure. Results show that the formula fits well not catastrophic industrial accident situation

A fuzzy methodology to evaluate the landslide risk in road lifelines

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Risk of electrocution during fire suppression activities involving photovoltaic systems

Firefighting activities regarding buildings normally require electric power to be disconnected before a water jet is used, in order to minimize the risk of electrocution. As for as concerns Photovoltaic Systems, during a fire event it is not possible to turn off the whole power system in order to guarantee that all the components are de-energized. The object of this paper is to estimate the safe distances to respect during firefighting involving PV Systems. To this end a series of experimental tests have been performed, in order to measure the current flowing through the water stream, under different conditions of nozzle design, jet shape, water pressure and stream length. Experimental results have been compared with data in literature. Moreover, the electrical conductivity of the water streams, which actually consists of water mixed with air, has been evaluate

16S metagenomics reveals dysbiosis of nasal core microbiota in children with chronic nasal inflammation: role of adenoid hypertrophy and allergic rhinitis

Allergic rhinitis (AR) and adenoid hypertrophy (AH) are, in children, the main cause of partial or complete upper airway obstruction and reduction in airflow. However, limited data exist about the impact of the increased resistance to airflow, on the nasal microbial composition of children with AR end AH. Allergic rhinitis (AR) as well as adenoid hypertrophy (AH), represent extremely common pathologies in this population. Their known inflammatory obstruction is amplified when both pathologies coexist. In our study, the microbiota of anterior nares of 75 pediatric subjects with AR, AH or both conditions, was explored by 16S rRNA-based metagenomic approach. Our data show for the first time, that in children, the inflammatory state is associated to similar changes in the microbiota composition of AR and AH subjects respect to the healthy condition. Together with such alterations, we observed a reduced variability in the between-subject biodiversity on the other hand, these same alterations resulted amplified by the nasal obstruction that could constitute a secondary risk factor for dysbiosis. Significant differences in the relative abundance of specific microbial groups were found between diseased phenotypes and the controls. Most of these taxa belonged to a stable and quantitatively dominating component of the nasal microbiota and showed marked potentials in discriminating the controls from diseased subjects. A pauperization of the nasal microbial network was observed in diseased status in respect to the number of involved taxa and connectivity. Finally, while stable co-occurrence relationships were observed within both control- and diseases-associated microbial groups, only negative correlations were present between them, suggesting that microbial subgroups potentially act as maintainer of the eubiosis state in the nasal ecosystem. In the nasal ecosysteminflammation-associated shifts seem to impact the more intimate component of the microbiota rather than representing the mere loss of microbial diversity. The discriminatory potential showed by differentially abundant taxa provide a starting point for future research with the potential to improve patient outcomes. Overall, our results underline the association of AH and AR with the impairment of the microbial interplay leading to unbalanced ecosystems

An Italian Multicenter Study on the Epidemiology of Respiratory Syncytial Virus During SARS-CoV-2 Pandemic in Hospitalized Children

Since the beginning of 2020, a remarkably low incidence of respiratory virus hospitalizations has been reported worldwide. We prospectively evaluated 587 children, aged <12 years, admitted for respiratory tract infections from 1 September 2021 to 15 March 2022 in four Italian pediatric hospitals to assess the burden of respiratory viruses during the COVID-19 pandemic in Italy. At admission, a Clinical Respiratory Score was assigned and nasopharyngeal or nasal washing samples were collected and tested for respiratory viruses. Total admissions increased from the second half of October 2021 to the first half of December 2021 with a peak in early November 2021. The respiratory syncytial virus (RSV) incidence curve coincided with the total hospitalizations curve, occurred earlier than in the pre-pandemic years, and showed an opposite trend with respect to the incidence rate of SARS-CoV-2. Our results demonstrated an early peak in pediatric hospitalizations for RSV. SARS-CoV-2 may exhibit a competitive pressure on other respiratory viruses, most notably RSV

Vaccination coverage in healthcare workers: a multicenter cross-sectional study in Italy

IntroductionIn recent years, a phenomenon known as "vaccine hesitancy" has spread throughout the world, even among health workers, determining a reduction in vaccination coverage (VC). A study aimed at evaluating VC among healthcare workers (HCWs) in 10 Italian cities (L'Aquila, Genoa, Milan, Palermo, Sassari, Catanzaro, Ferrara, Catania, Naples, Messina) was performed.Materials and methodsAnnex 3 of the Presidential Decree n. 445 of 28 December 2000 was used to collect information on the vaccination status of HCWs. The mean and standard deviation (SD) were calculated with regard to the quantitative variable (age), while absolute and relative frequencies were obtained for categorical data (sex, professional profile, working sector, vaccination status). The connection between VC and the categorical variables was evaluated by chi-square method (statistical significance at p<0.05). The statistical analyses were performed by SPSS and Stata software.ResultsA total of 3,454 HCWs participated in the project: 1,236 males and 2,218 females. The sample comprised: physicians (26.9%), trainee physicians (16.1%), nurses (17.2%) and other professional categories (9.8%). Low VC was generally recorded. Higher VC was found with regard to polio, hepatitis B, tetanus and diphtheria, while coverage was very low for measles, mumps, rubella, pertussis, chickenpox and influenza (20-30%). ConclusionsThis study revealed low VC rates among HCWs for all the vaccinations. Measures to increase VC are therefore necessary in order to prevent HCWs from becoming a source of transmission of infections with high morbidity and/or mortality both within hospitals and outside

3D Finite element model of a blast load in a tunnel

This paper presents a 3D finite element analysis of the effect caused by a blast inside a reinforced concrete tunnel. The simulated explosion was caused by the crash of a heavy vehicle transporting inflammable material (LPG). The finite element technique was used to analyze the structural problems on the tunnel reinforced concrete structure considering the fire action and the subsequent explosion (blast) effect, incorporating appropriate material models. Through FEM software the tunnel behavior was described with regard to structural safety. Indeed, tunnels must be designed to withstand damage factors, so it is desirable that if such an explosion did occur, the tunnel should be able to return to service in safety as soon as possible with minor repairs. Therefore, following the presented analysis, the most important factors influencing the dynamic response and the damage of the structure could be identified. The simulation involved aspects of thermal analysis and structural problems and the tensions in the structure generated by the effect of temperature caused by the fire and by the blast overpressure were analyzed. Following this approach, the most important factors influencing the dynamic response and damage of structure can be identified and appropriate preventive measures can be designated

Self-Organizing Map and clustering algorithms for the analysis of occupational accident databases

A data analysis method for occupational accident databases. The approach is based on the joint use of Kohonen’s SOM and k-means clustering. The novelty aspect is the visualization capability offered to the analyst. The method was applied to accidents occurred in the Italian wood processing industry

Finite Element Analysis of Geogrid-Stabilized Unpaved Roads

The need to increase the durability of unpaved roads and the need to improve driver comfort have led to this research: to focus more attention on the use of reinforcements for this type of road. Unpaved roads are created by using an unbound granular base layer placed on compacted cohesive soils. When the subgrade is weak, due to its poor consistency and high compressibility, generally, a geosynthetic reinforcement (geogrid and/or geotextile) is placed over the subgrade, followed by a compacted granular fill layer. The use of geosynthetics can produce several benefits, such as draining, reinforcement, filtering, separation, and proofing. This paper aims to present a numerical investigation using 3-D Finite Element Modeling (FEM) to analyze the improvement, in terms of the rutting reduction of an unpaved road system, reinforced by a geogrid, under repeated traffic loads. 3-D FEM analysis was carried out on two unpaved road sections, one reinforced and the other unreinforced, with both subjected to an impulsive wheel loading. It can be concluded that a significant improvement in pavement behavior is obtained by placing a geogrid layer at the base–subgrade interface. In fact, the obtained results show that geogrid reinforcement can provide a relevant contribution to the reduction of permanent deformations