170,274 research outputs found
Il trattamento con imipemen-cilastatina o pefloxacina delle sovrainfezioni ad eziologia batterica in corso di infezione da HIV (gruppo 3° o 4°)
No full textSulle cause idrauliche di innesco dei fenomeni di instabilità dei rilevati arginali
No full textIl presente lavoro analizza alcuni degli aspetti che possono compromettere la stabilità di un argine. Più in particolare, avvalendosi di modelli matematici già disponibili in letteratura, vengono presi in esame sia problemi di equilibrio limite che problemi di erosione interna (piping) connessi con l’instaurarsi di un regime di moti di filtrazione all’interno del rilevato arginale. Il lavoro consta di due parti: nella prima parte viene descritto un approccio razionale per lo studio della stabilità arginale rispetto a problemi di equilibrio limite, e vengono proposti una serie di abachi che consentono un’agevole verifica, rispetto a tale problematica, della progettazione eseguita; nella seconda parte viene invece descritto un approccio razionale per lo studio dell’innesco del piping, e viene fornito un modello interpretativo di analisi che, calibrato alla luce dei pochi dati sperimentali sin qui disponibili in letteratura, sembra meglio prestarsi, rispetto a quelli proposti da altri autori, alla valutazione del carico idraulico critico per l’innesco dei fe-nomeni di pipin
Ottimizzazione, su base probabilistica, delle reti di distribuzione idrica mediante l’uso di algoritmi genetici
No full textIl problema dell’ottimizzazione di una rete idrica, ovvero della ricerca del più idoneo set di diametri da utilizzare al fine di ridurre, compatibilmente con l’esigenza di garantire predeterminati livelli di servizio, il costo di realizzazione e, eventualmente, di gestione di una rete di distribuzione idrica, rappresenta una scelta progettuale importante, che l’ingegnere può oggi affrontare con l’ausilio di approcci innovativi che, già da qualche anno, sono stati proposti in campo scientifico, ma che appaiono ormai maturi per essere utilizzati anche in campo tecnico. A tale scopo, nel presente lavoro viene proposta una nuova metodologia per il corretto dimensionamento dei diametri dei lati di una rete di distribuzione idrica, volta ad individuare quella combinazione di diametri in grado di minimizzarne il costo e, contemporaneamente, capace di soddisfare i vincoli di pressione desiderati. Più in particolare, la metodologia proposta è basata, da un lato, su un approccio probabilistico in grado di portare in conto la componente stocastica della richiesta idrica dell’utenza e, dall’altro, su un algoritmo di ottimizzazione, a sua volta basato su una applicazione degli Algoritmi Genetici. Per quanto riguarda il primo aspetto, ossia quello relativo alla variabilità semialeatoria della richiesta, facendo riferimento ad un approccio già precedentemente utilizzato da uno degli autori (Gargano & Pianese, 2000), si considera, per motivi di semplicità e di chiarezza espositiva, la sola componente aleatoria della richiesta da parte dell’utenza, e si prende in esame la sola condizione di punta giornaliera. Per quanto riguarda, invece, l’algoritmo genetico utilizzato per la procedura di ottimizzazione, che viene effettuata per ciascuna richiesta da parte dell’utenza, esso è analogo a quello a suo tempo proposto da altri autori (Savic & Walters, 1997) differenziandosi da questo per le modalità di selezione del set originario di diametri (una rank selection di tipo esponenziale in luogo di quella lineare adottata dai suddetti autori) e per la procedura utilizzata per l’implementazione dell’elitismo (Arnò & Mazzola, 2000). Vengono, infine, illustrati i risultati di alcuni esempi numerici volti a mostrare la concreta applicabilità dell’approccio proposto a casi reali
Terrestrial-marine continuum of sedimentary natural organic matter in a mid-latitude estuarine system
No full textAbstract
Purpose Humic acids (HA) have several environmental roles, but are particularly important in aquatic environments, being
recognized as redox active natural organic matter (NOM) components.We examined NOM in recent sediments of a low-energy
coastal environment which is free from inputs of dissolved terrestrial HA as their solubility is suppressed by bonding with Ca2+
ions. Our aim is to investigate the contribution of autochthonous versus terrestrial C sources to HA and their fractions along a
river-coastal lagoon transect.
Materials and methods Surface sediments were collected along the Aussa River (R), in the central basin of the Marano and
Grado Lagoon (L) and within a secluded lagoon fish farm (FF). Extractable NOM components were obtained by extracting
sediments first with 0.5 M NaOH (free NOM) and then with 0.1 M NaOH plus 0.1 M Na4P2O7 (bound NOM). Extracts were
separated into non-humic and humic fractions by solid phase chromatography. Organic carbon (Corg), total nitrogen (Ntot), δ13C,
and δ15N were determined with an Isotope Ratio Mass Spectrometer (Thermo Scientific Delta VAdvantage) coupled with an
Elemental Analyzer (Costech Instruments Elemental Combustion System). Fourier-transform infrared (FTIR) spectra were
recorded with a FT-IR100 PerkinElmer Spectrometer. UV-vis spectra were recorded at pH 7 by a Varian Cary Spectrophotometer.
Results and discussion Both NOM and HA display typical traits of terrestrial origin in river sediments and of a more marine
(algal) origin in lagoon and fish farm sediments. This trend is evident in free HA, whereas bound HA seem more influenced by
terrestrial inputs. A larger proportion (60–70%) of non-humic C was extracted by NaOH in all samples. Bound HA differ from
free HA for their C/N ratios, which are higher and vary within a much narrower range. The changes in HA’s 13C isotopic
composition, FTIR spectra, and spectroscopic parameters (SUVA254, SR, and aromaticity) highlight a progressive mixing of
terrestrial and marine substrates that either undergo in situ humification or are transported as materials sorbed onto suspended
mineral particles.
Conclusions Our results highlight the existence of a complex, but continuous pattern of terrestrial and marine contributions to C
sequestration and humification even in transitional environments where allochthonous humic C inputs are restricted due to
insolubilization of humic substances by Ca2+. Along the examined transect, the NOM and free and bound HA appear well
differentiated. Terrestrial inputs contribute to the bound HA fraction via transported mineral particles in all the samples, no matter
the environment encountered
Direct costs of schizophrenia in Italian community psychiatric services
No full textObjective: To estimate resource utilisation and direct costs of treatment for patients with schizophrenia in Italian Community Mental Health Centers (CMHCs). Design: Multicentre, retrospective observational study. CMHCs recruited all patients who attended a follow-up consultation during the period September to December 1998. At enrolment, psychiatrists completed a questionnaire on consumption of resources in the 2 months before recruitment. Setting: 14 CMHCs. Perspective: Italian National Health Service (INHS). Patients: 702 patients with a diagnosis of schizophrenia or other psychotic disorders, defined according to the Diagnostic and Statistical Manual of Mental Disorders-fourth edition. These patients had been followed by the CMHCs for at least 2 years and attended a follow-up consultation either during the period September to December 1998 or on randomly selected days during this period. Patients were classified into seven groups according to their diagnosis. Results: The mean direct cost of patients with schizophrenia in the 2-month observation period was 2 234 475 Italian lire [L] (1154.01 Euro; EUR); direct costs ranged from L.1 545 818 to L.2 775 658 (EUR798.35 to EUR1433.51) by prognostic group. There was wide variability for prognostic groups in the impact of most cost components on total cost. Admissions accounted for between 11.4 and 56.3% of the total cost, daycare centre days for between 11.3 and 35.5%, home visits for 7.8 to 16.4%, and day-hospital days for 5.4 to 32.8%. Anti-psychotics and anxiolytics were the most prescribed drugs and also the most costly. Conclusion: Despite the limitations of the study related to the short period considered, we believe this study offers some interesting information on the burden of schizophrenia, a disease for which its cost has received limited attention so far in Italy
Benthic fluxes of mercury species in a lagoon environment (Grado lagoon, Northern Adriatic Sea, Italy)
No full textThe role of the major biogeochemical processes in Hg cycling at the sediment–water interface was investigated in the Grado Lagoon (Northern Adriatic Sea). This wetland system has been extensively contaminated from the Idrija Hg Mine (Slovenia) through the Isonzo River suspended load carried by tidal fluxes. Three approaches were used to study the sediment–water exchange of total Hg (THg), methylmercury (MeHg), reactive Hg (RHg) and dissolved gaseous Hg (DGHg): (1) estimation of diffusive fluxes from porewater and overlying water concentrations, (2) measurements of benthic fluxes using a deployed light benthic chamber in situ and (3) measurements of benthic fluxes during oxic–anoxic transition with a laboratory incubation experiment. The THg solid phase, ranging between 9.5 and 14.4 lg g1, showed slight variability with depth and time. Conversely, MeHg contents were highest (up to 21.9 ng g1) at the surface; they tended to decrease to nearly zero concentration with depth, thus suggesting that MeHg production and accumulation occur predominantly just below the sediment–water interface. Porewater MeHg concentrations (0.9–7.9 ng L1, 0.15–15% of THg) varied seasonally; higher contents were observed in the warmer period. The MeHg diffusive fluxes (up to 17 ng m2 day1) were similar to those in the nearby Gulf of Trieste [Covelli, S., Horvat, M., Faganeli, J., Brambati, A., 1999. Porewater distribution and benthic flux of mercury and methylmercury in the Gulf of Trieste (Northern Adriatic Sea). Estuar. Coast. Shelf Sci. 48, 415–428], although the lagoon sediments contained four-fold higher THg concentrations. Conversely, the THg diffusive fluxes in the lagoon (up to 110 ng m2 day1) were one- to two-fold higher than those previously estimated for the Gulf of Trieste. The diurnal MeHg benthic fluxes were highest in summer at both sites (41,000 and 33,000 ng m2 day1 at the fishfarm and in the open lagoon, respectively), thus indicating the influence of temperature on microbial processes. The diurnal variations of dissolved THg and especially MeHg were positively correlated with O2 and inversely with DIC, suggesting an important influence of benthic photosynthetic activities on lagoon benthic Hg cycling, possibly through the production of organic matter promptly available for methylation. The results from the dark chamber incubated in thelaboratory showed that the regeneration of dissolved THg was slightly affected by the oxic–anoxic transition. Conversely,the benthic flux of MeHg was up to 15-fold higher in sediments overlain by O2 depleted waters. In the anoxic phase, the MeHg fluxes proceeded in parallel with Fe fluxes and the methylated form reached approximately 100% of dissolved THg.The MeHg is mostly released into overlying water (mean recycling efficiency of 89%) until the occurrence of sulphide inhibition, due to scavenging of the available Hg substrate for methylation. The results suggest that sediments in the Grado Lagoon, especially during anoxic events, should be considered as a primary source of MeHg for the water column
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