1,721,194 research outputs found
Behaviour of reticulocyte counts and immature reticulocyte fraction during a competitive season in elite athletes of four different sports
No full textThe role of reticulocytes (Ret) in sports medicine became important when the count of immature erythrocytes has been introduced in protocols used and officially approved for antidoping purposes. The use of modern automated analysers, which allow the easy count and the description of characteristics of reticulocytes, increased the possible use of these parameters in sports medicine. We studied the behaviour of Ret and immature reticulocyte fraction (IRF) in top-level athletes practising rugby, ski, soccer and cyclism, throughout a competitive season. We aimed at increasing the knowledge of physiological characteristics of these sportsmen and supplying valuable suggestions to trainers and sports physicians. We observed a stability of Ret counts, also during training and competitions, although some modifications, namely decrease during competitions periods in cyclists, and in rugby and soccer players, occurred. No significant correlation was found between Ret count and Hb in each sport discipline. IRF values tend to be high in athletes owing to continuous bone marrow stimulation linked to haemolysis, typical of sports activities. We confirm the validity of the use of Ret counts for antidoping purposes and also for evaluating health status and iron metabolism of sportsmen
Laboratory investigation on reactivated residual strength
No full textRecent research has outlined that mobilised in situ strength at the reactivation of displacements along a pre-existing sliding surface may be slightly greater than laboratory residual strength. Although geotechnical literature explains this difference in various ways - for instance, strength gain due to soil ageing - little work has been devoted to this topic.
Bromhead ring shear tests were carried out on remoulded samples of the Cormons flysch, a typical geological formation in north-eastern Friuli-Venezia Giulia (Italy). The specimens came from the shallow weathered crust of the Cormons flysch, near the areas of Montona and Rosazzo. This experimental study aimed at highlighting the effect of a limited number of parameters on strength gain at the reactivation of displacements along aged sliding surfaces. The results of this research confirm that ageing may cause a rising of reactivated shear strength above the residual value, depending on time of ageing and vertical stress. The longest ageing period - about a month - showed a 20% strength increase for the Rosazzo flysch, and a 30% increase for the Montona flysch. Reactivated strength increases according to a power law: almost 50% develops over a short time, i.e., after 24 hours of ageing. In the long term, strength growth is characterised by a deviatoric creep rate gradually approaching zero
Resistenza residua alla riattivazione del flysch di Cormons.
No full textDiverse analisi retrospettive di movimenti franosi quiescenti hanno indicato la possibilità che la resistenza al taglio mobilizzata
in sito, alla riattivazione degli scorrimenti, possa essere superiore a quella residua ottenuta in laboratorio con l’apparecchio
di taglio anulare. Tale tematica, di rilevante interesse pratico negli studi di stabilità dei corpi di frana quiescenti,
coinvolge diversi processi fisico-chimici legati al tempo di invecchiamento del terreno (ageing).
La memoria riporta i primi risultati di alcune esperienze di laboratorio condotte su campioni di flysch per lo studio dei
processi di incremento della resistenza alla riattivazione degli scorrimenti lungo preesistenti superfici di scorrimento. I materiali
utilizzati nelle sperimentazioni provengono dalla formazione denominata flysch di Cormons e sono stati prelevati
da due distinti corpi di frana, nelle località di Montona e di Rosazzo, ubicati nella fascia collinare pedemontana orientale
del Collio del Friuli-Venezia Giulia. Sotto il profilo geologico tale area è stata interessata da cicli di sedimentazione e da
processi di tettonizzazione, gli ultimi legati alla formazione dei rilievi alpini nell’Italia settentrionale. Ambedue i terreni
appartengono allo strato di alterazione più superficiale del flysch di Cormons, caratterizzato da marcata eterogeneità e dalla
presenza di diffusi dissesti gravitativi che periodicamente si attivano lungo le preesistenti superfici di scorrimento.
Dopo una iniziale caratterizzazione della resistenza residua dei due terreni flyschoidi, si discutono i risultati delle prove
di riattivazione condotte con l’apparecchio di taglio anulare di Bromhead, eseguendo cicli di invecchiamento sui campioni
precedentemente portati in condizioni residue. I cicli di invecchiamento, con tempi variabili da pochi minuti fino a circa
un mese, hanno consentito di definire i recuperi di resistenza alla riattivazione in funzione del tempo e del livello della
tensione normale. In tale contesto, sono state attuate due distinte modalità di prova, volte a evidenziare, durante il processo
di invecchiamento, l’effetto dello stato di tensione residua sulla superficie di scorrimento.
Altri aspetti legati alle variazioni delle condizioni ambientali (chimismo del fluido interstiziale, variazioni di temperatura,
storia tensionale sulla superficie di scorrimento, velocità di riattivazione degli scorrimenti), sebbene di preminente
interesse per la problematica trattata non sono stati approfonditi in questa memoria.
I principali risultati ottenuti indicano la possibilità dell’insorgere di recuperi di resistenza, al di sopra di quella residua,
in relazione al tempo trascorso e alla tensione normale. Per i massimi tempi d’invecchiamento investigati, i recuperi di resistenza
sono stati mediamente dell’ordine del 20% per il flysch di Rosazzo e del 30% per quello di Montona. Questi sembrano
originati da due principali meccanismi di incrudimento: il primo, a breve termine, legato alle proprietà tixotropiche
delle argille, mentre il secondo, di lungo termine, funzione delle deformazioni viscose volumetriche e deviatoriche, maturate
durante il periodo di invecchiamento
The institutional history of Milan metropolitan area
No full textThe institutional history of Milan metropolitan area. Territory, Politics, Governance. This paper highlights the long-term institutional trajectory of the Milan metropolitan area in Italy using comparative-historical analysis. Although technical and political proposals of metropolitan institutions in Milan have been debated over the last 70 years, empirical evidence shows that the Milan metropolitan area still lacks clear rules for political integration and effective spatial tools for policy-making. In order to explain this outcome, the paper adopts a narrow definition of 'path dependency' and tests it in two different processes of institutional change: land-use planning at the metropolitan scale, and the organization of local governments in metropolitan areas. The paper finds that in both processes, initial episodes of institutional change, promoted by reformist coalitions, were co-determined by 'contingent events': unpredictable circumstances exceeding the control of reformers. It also finds that, in both processes, outcomes of subsequent episodes of institutional change were co-determined by 'increasing returns': the reinforcement of previously crystallized configurations of powers and interests. Therefore, the paper reveals the historical events and socio-political dynamics that determined the 'path dependency' of institutional outcomes at the metropolitan scale in Milan. It argues that ongoing metropolitan institutional dynamics can be better explained by the absence of a land-use reform and the persistence of direct election of mayors.L’histoire institutionnelle de la zone métropolitaine de Milan. Territory, Politics, Governance. À partir d’une analyse comparative historique, ce présent article cherche à mettre l’accent sur la trajectoire institutionnelle à long terme de la zone métropolitaine de Milan en Italie. Bien que l’on étudie depuis les dernières 70 années des propositions à la fois techniques et politiques quant aux institutions métropolitaines à Milan, les résultats empiriques laissent voir que la zone métropolitaine de Milan manque toujours des règles claires en matière de l’intégration politique et des outils spatiaux efficaces pour l’élaboration des politiques. Afin d’expliquer ce résultat, l’article adopte une définition restreinte de la notion de ‘dépendance de trajectoire’ et la met à l’épreuve en employant deux processus tout à fait différents relatifs à la transformation institutionnelle: à savoir, la planification de l’occupation du sol à l’échelle métropolitaine, et l’organisation de l’administration locale dans les zones métropolitaines. Il s’avère que, pour ce qui est des deux processus, les premières étapes de la transformation institutionnelle, favorisées par les coalitions réformistes, ont été co-déterminées suite à des ‘événements imprévisibles’: à savoir: des imprévus qui dépassent le cadre de l’influence des réformateurs. Il est évident aussi que, dans les deux cas, les résultats des étapes ultérieures de la transformation institutionnelle ont été co-déterminées par des ‘rendements croissants’: la consolidation des configurations des pouvoirs et des intérêts concrétisées autrefois. Par conséquent, l’article laisse voir les événements historiques et la dynamique socio-politique qui ont déterminé la ‘trajectoire de dépendance’ des résultats institutionnels à l’échelle métropolitaine à Milan. On affirme que la dynamique instutionnelle métropolitaine en vigueur pourrait mieux s’expliquer par l’absence de réforme relative à l’occupation du sol et par la présence des maires élus au suffrage universel direct.Historia institucional del área metropolitana de Milán. Territory, Politics, Governance. Mediante un análisis histórico comparado, en este artículo se destaca la trayectoria institucional a largo plazo del área metropolitana italiana de Milán. Aunque en los últimos 70 años se han debatido las propuestas técnicas y políticas de las instituciones metropolitanas en Milán, los datos empíricos disponibles muestran que el área metropolitana de Milán todavía carece de normas claras de integración política y herramientas espaciales eficaces para la elaboración de políticas. A fin de explicar este resultado, en este artículo se adopta una definición estrecha de la ‘dependencia de trayectorias’ y se comprueba en dos procesos diferentes de cambio institucional: planificación del uso del suelo a escala metropolitana y la organización de los Gobiernos locales en las áreas metropolitanas. Se observa que en ambos procesos los episodios iniciales del cambio institucional, fomentado por las coaliciones reformistas, estaban codeterminados por ‘contingencias históricas’: circunstancias imprevisibles que excedían el control de los reformistas. También se observa que en ambos procesos, los resultados de los episodios posteriores del cambio institucional estaban codeterminados por ‘rendimientos crecientes’: el fortalecimiento de configuraciones cristalizadas previamente de poderes e intereses. Por tanto, en este artículo se revelan los acontecimientos históricos y las dinámicas sociopolíticas que determinaron la ‘dependencia de trayectorias’ de los resultados institucionales a escala metropolitana en Milán. Se argumenta que las dinámicas institucionales metropolitanas pueden explicarse mejor por la ausencia de una reforma del uso del suelo y la persistencia de la elección directa de alcaldes
Dynamic performance of an embankement using linear and non linear approach
No full textThe paper presents a comparison between linear and non-linear dynamic analyses performed to examine the stability of a tailing dam located near the village of Cave del Predil (Italy) where, during the years of major mining activities, more than 2x106m3 of tailings were accumulated into four basins built on the left bank of the Rio del Lago stream. The slags present a grain size distribution typical of silty sands and have been confined by levees made by the coarse soil fraction deriving by mining activity. As the collapse of the levees could cause the obstruction of the stream and the release of pollutants and heavy metals in the ecosystem, a first study was performed at the beginning of 90’ to evaluate the stability conditions of mine tailings deposits under seismic conditions using a pseudostatic approach implemented into limit equilibrium methods. Starting from these previous analyses, the knowledge of geotechnical properties on both materials have been completed and integrated recently with new in situ and laboratory tests with the aim to create a finite element model and investigate the dynamic behaviour of basins subjected to a seismic action during a period of heavy rainfall. The study was developed in sequential steps: after a seepage analysis performed to evaluate pore pressure distribution inside the basin, FEM method was used to investigate its dynamic behaviour and post seismic stability conditions. The initial seepage analysis highlights the high permeability contrast between fine tailings and coarse levees materials and that the water pressures inside the basins are not particularly influenced by intensity and frequency of rainfall. The results of this initial seepage analysis, in terms of major water pressures and water table increments, were assigned to the following pre-seismic stability analysis. The technical performance of tailings during an earthquake may be defined with reference to serviceability and ultimate limit states. The first ones are represented by the development of differential displacements that may cause localized failures inside the levees through which the polluted sediments may come out and arrive at the biosphere; the second ones are related to the formation of shallow and deep slidings of the levees induced also by liquefaction phenomena. The dynamic analysis of the basins has been performed using different accelerograms changing the severity of seismic action depending from the hypothesized return period. For return periods associated to the serviceability limit state, the shear strains computed with a linear elastic model resulted small and lower than the threshold generally adopted in this kind of analysis. Moreover, the instantaneous displacements and excess pore water pressures were small while the maximum ground acceleration, lower than critical one, was not sufficient to develop permanent displacements assuring the serviceability of the earth structure. The analysis performed for long return periods associated to ultimate limit states, at present in progress, show shear strains much more high and sufficient to adopt a non-linear constitutive soil model even if permanent displacements remain anyway admissible for an earth levee. The development of higher excess water pressures highlights the possibility of liquefaction phenomena in the saturated zones inside fine tailings but the location and the thickness of these zones are not sufficient to trigger ultimate limit states like the loss of embankment global stability
Caratteristiche geotecniche di miscele compattate limo cemento e bentonite
No full textL’attività estrattiva produce materiali di scarto, quali i limi di lavaggio, che potrebbero essere utilizzati se sottoposti a procedimenti tecnologici che ne migliorino le proprietà geotecniche. L’articolo riporta i risultati di prove di compattazione, permeabilità e compressione semplice eseguite su materiale limoso allo stato naturale e additivato con cemento e bentonite. I risultati evidenziano che l’impiego del cemento migliora sensibilmente la resistenza dei limi, ma l’efficacia del trattamento dipende dal contenuto in acqua che deve essere sufficiente a consentire l’idratazione del legante. Per contro, l’aggiunta di cemento conferisce alla miscela una fragilità elevata. Le miscele limo-bentonite hanno una permeabilità molto bassa, ma il loro comportamento meccanico è simile a quello dei suoli argillosi compattati: la resistenza e la rigidezza si riducono sensibilmente per valori di w>wopt. Il comportamento delle miscele limo-cemento-bentonite dipende dal rapporto fra gli additivi presenti: la prevalenza del cemento conferisce alla miscela una resistenza elevata ma non consente la completa idratazione della bentonite e quindi lo sviluppo di bassi valori di permeabilita
Consolidazione di sedimenti lagunari con alto contenuto d’acqua: sperimentazione di laboratorio per la previsione del decorso in sito
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Improvement of geotechnical characteristics of silts deriving from washing of quarry gravel
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