108 research outputs found
Effetti del lockdown sulla composizione e sulle sorgenti del PM10 nell'area di Roma attraverso source apportionment basato sul frazionamento chimico degli elementi
No full textDurante il lockdown del 2020, sono stati raccolti campioni giornalieri di PM10 in tre siti nell'area di Roma, due siti urbani da traffico (Sapienza e Via Saredo) e uno peri-urbano fortemente impattato da riscaldamento domestico a biomasse (Montelibretti). Il PM10 è stato campionato anche nei periodi precedenti e successivi al lockdown ed è stato analizzato per i macro-elementi, ioni inorganici, EC, OC, levoglucosano ed elementi in traccia. Questi ultimi sono stati frazionati chimicamente per aumentarne la selettività come traccianti di sorgente. I data-set ottenuti sono stati analizzati tramite PMF e sono state identificate sorgenti remote (due diversi contributi di polveri minerali, spray marino fresco, combustione di oli pesanti) e sorgenti locali (traffico veicolare e combustione di biomasse) che sono state fortemente abbattute durante il lockdown. Ciò ha permesso di descrivere chiaramente i profili delle sorgenti remote e di quantificare la riduzione dell'impatto delle fonti antropiche, consentendo di valutare l'efficacia delle misure di mitigazione generalmente adottate per controllare la concentrazione di massa del PM10
Prefazione a "Evolution Equations and Mathematical Models in the Applied Sciences" (EEMMAS)
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Sistema di fissazione esterna ed elastici nella terapia della contrattura del quadricipite femorale nel cane
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Updated Italian checklist of Tenuipalpidae with description of a new species and new worldwide records of the genus Cenopalpus (Pritchard et Baker)
No full textThe family Tenuipalpidae includes agricultural pests that have garnered extensive attention from the global research community. Despite the economic importance of tenuipalpids, due to their ecology and global trade of the infested plants, there has not been any corresponding and comprehensive research on these mites in Italy in recent decades. This study aimed to determine the species composition of tenuipalpid mites in Italy, update the Italian checklist for the taxon, and include new records and host plant associations of the genera Brevipalpus Donnadieu and Cenopalpus Pritchard and Baker worldwide. The study found several new records of tenuipalpid species in Italy, including four Cenopalpus and two Brevipalpus species. Additionally, one new species Cenopalpus ulmifolius De Giosa, Ochoa et de Lillo was added to the list. The research also incorporated new records of Cenopalpus species in different countries and several new host plant associations and the description of novel taxonomic characters were present for the Cenopalpus species studied during this work, since they were the most abundant tenuipalpid collected in the sampled areas. The study’s findings are crucial for developing effective management for tenuipalpid mites, understanding the fauna composition, and constructing preparedness strategies for quarantine purposes
Statistics of spatially structured stochastic processes modeling crystallization of polymers
No full textTopology Optimization of a Femoral Stem in Titanium and Carbon to Reduce Stress Shielding with the FEM Method
No full textArthroplasty is commonly performed to treat advanced osteoarthritis or other degenerative
joint conditions; however, it can also be considered for young patients with severe joint damage that
significantly limits their functionality and quality of life. Young patients are still at risk of aseptic
mobilization and bone resorption due to the phenomenon of stress shielding that causes an uneven
distribution of tensions along the femoral contact surface prosthesis. This phenomenon can be limited
by choosing the material of the prosthesis appropriately or by varying its stiffness, making sure that
its mechanical behavior simulates that of the femur as much as possible. The aim of this study is to
evaluate the mechanical strength of a prosthesis optimized both in shape and material and compare
the results with a standard titanium prosthesis. Methods: Through three-dimensional modeling
and the use of finite element method (FEM) software such as ANSYS, the mechanical behavior of
traditional prosthesis and prosthesis optimized topologically respecting the ASTM F2996-13 standard.
Results: With topological optimization, there is a stress reduction from 987 MPa to 810 MPa with a
mass reduction of 30%. When carbon fiber is used, it is possible to further reduce stress to 509 MPa.
Conclusions: The reduction in stress on the femoral stem allows an optimal distribution of the load
on the cortical bone, thus decreasing the problem of stress shielding
Stochastic modelling and statistics of polymer crystallization process
No full textCrystallization of polymers is modelled as a spatially structured process consisting of a nucleation phase and a growth phase. A counting process approach together with methods of stochastic geometry leads us to the evolution equations of the relevant quantities of the process. In particular we provide local and global convergence of the stochastic growth process to its expected value, thus justifying the use of deterministic models to predict the results of real experiments. Estimates of the relevant parameters of the process are obtained via the maximum likelihood method, and also by a nonparametric method based on the estimation of the hitting function of the associated Boolean model. Asymptotic properties of the estimators are given and computer experiments are reported to show their qualitative behaviour, as a function of the available volume and of time
Source apportionment of PM10 and its oxidative potential by spatially resolved samplings.
No full textIn the last few years, the relevance of high spatial resolution data for PM source apportionment methods has been highlighted. This method allows reducing analytical costs by sampling at various sites for long periods, thus obtaining a PM chemical characterization at high spatial resolution. Furthermore, the variance of concentrations is mainly due to the spatial distribution of the emission sources, with a low contribution of the meteorological conditions and the application of multivariate methods for source apportionment allows obtaining more stable and representative chemical profiles, especially for the local sources.
In this study, automatic and very-low volume samplers were employed to evaluate the spatial variability of PM10 concentration and composition at 9 sampling sites distributed over the Sacco River Valley (southern area of Latium Region). The Valley is characterized by frequent and severe atmospheric stability conditions, by high-density population and by the presence of significant number of industrial settlements that had led to a significant pollution phenomena over the years (Battisti et al., 2022; Donateo et al., 2020; Sozzi et al., 2017).
PM daily limits exceedances are frequently recorded in the Sacco Valley during the cold season, probably due to the low atmospheric mixing properties (ARPA Lazio, 2022; ISPRA, 2020).
At each site, samples have been collected on both quartz and Teflon membranes. Teflon PM filters were subjected to a chemical fractionation procedure (soluble and insoluble fractions), that permits to increase the selectivity of the elements as source tracers (Massimi et al., 2021; Perrino et al., 2010; Canepari et al., 2009). Concentration of elements was determined through a quadrupole inductively coupled plasma mass spectrometer (ICP-MS). The soluble PM10 fraction was also used for the application of three oxidative potential assays (Ascorbic Acid -A A, Dithiothrietol - DTT, Dichlorofluorescein - DCFH) and for the analysis of inorganic ions and levoglucosan (LVG). Quartz membrane filters were instead used for the determination of elemental and organic carbon (EC and OC, respectively).
Positive Matrix Factorization (PMF) was applied to identify and assess the main sources of particulate emissions in the sampling areas and to determine the weight of each emission source on the OPAA, OPDTT and OPDCFH.
Results showed that, during winter, half of PM mass is due to biomass burning (BB) processes; PMF identified two different profiles of BB, characterized by a different tracers ratio, whose relative contributions strongly depends on the monitored site. The first profile (BB1) contains high concentration of OC, EC, LVGSN and K+; the second one (BB2) contains a higher contribute of other inorganic tracers, such as Cs, Rb and Tl in their soluble fraction. Together with LVGS, these last parameters have been demonstrated to be very selective tracers of biomass combustion for domestic heating (biblio). It is reasonably hypothesized that the two contributions correspond to different heating appliance and/or wood material.
The oxidative potential measured by the DCHF method appear to be predominantly associated with the biomass burning (mainly BB1) and the AA assay to the non-exhaust vehicular traffic. OPDTT had significant contributes by both the sources
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