L'altro eccezionalismo: William Appleman Williams tra storia, storiografia e impegno civile

La storiografia statunitense, a partire dagli anni Cinquanta, vide l’affermarsi di una nuova interpretazione della politica estera americana. Archiviata la storia diplomatica come storia dei trattati o storia delle interazioni delle élites dominanti, abbandonata una visione incentrata sull’equilibrio di potenza, il dibattito storiografico si arricchì della cosiddetta interpretazione «revisionista», antitetica rispetto a quella che, fino a quel momento, aveva predominato. Soggetto di analisi storica restava sempre lo Stato ma l’enfasi maggiore era posta sui fattori economici che ne influenzavano l’azione: si metteva in rilievo l’interazione tra l’interesse privato e il soggetto statale. Capofila di questa nuova scuola fu William Appleman Williams. Questa ricerca si pone l’obiettivo di delineare il contesto storiografico dal quale emersero gli studi di Williams e di cui egli ne roviesciò alcuni assunti fondamentali. Si intende tracciare il suo percorso intellettuale – storiografico e pubblico – al fine di restituire la complessità di un personaggio che divenne un vero e proprio «intellettuale pubblico». I quesiti, a cui questa ricerca vuole dar risposta riguardano l’evoluzione del percorso intellettuale di Williams tanto in ambito storiografico quanto, più in generale, in quello pubblico; il contributo alla ridefinizione dell’identità statunitense e del suo ruolo internazionale; il lascito della sua riflessione nella storiografia. Prendendo le mosse dall’idea di frontiera proposta da Turner, Williams sostenne che la fine dell’espansione territoriale «interna» aveva obbligato gli Stati Uniti a cercare nuovi mercati per il proprio surplus. Era stata tale necessità a catalizzare la Open Door Diplomacy, guidata da ragioni economiche, che presto identificarono l’interesse nazionale per trasformarsi in una vera e propria ideologia nel XX secolo.L’esito di tale politica estera fu la creazione di un impero non più territoriale ma frutto dell’espansione economica. E proprio questa riflessione sull’impero influenzò, negli anni Sessanta, la protesta studentesca che chiese un ripensamento del ruolo internazionale degli Stati Uniti.

Una applicazione sistematica del metodo CANSLIM di William O'Neil

Applicazione sistematica del metodo CANSLIM sul mercato italiano.

Impact of anthropogenic stressors on the population genetics of the common bioindicator Dreissena polymorpha (Pallas, 1771)

Toxicant inputs from agriculture, industry and human settlements have been shown to severely affect freshwater ecosystems. Pollution can lead to changes in population genetic patterns through various genetic and stochastic processes. In my thesis, I investigated the impact of anthropogenic stressors on the population genetics of the zebra mussel Dreissena polymorpha. In order to analyze the genetics of zebra mussel populations, I isolated five new highly polymorphic microsatellite loci. Out of those and other already existing microsatellite markers for this species, I established a robust marker set of six microsatellite loci for D. polymorpha. rnMonitoring the biogeographical background is an important requirement when integrating population genetic measures into ecotoxicological studies. I analyzed the biogeographical background of eleven populations in a section of the River Danube (in Hungary and Croatia) and some of its tributaries, and another population in the River Rhine as genetic outgroup. Moreover, I measured abiotic water parameters at the sampling sites and analyzed if they were correlated with the genetic parameters of the populations. The genetic differentiation was basically consistent with the overall biogeographical history of the populations in the study region. However, the genetic diversity of the populations was not influenced by the geographical distance between the populations, but by the environmental factors oxygen and temperature and also by other unidentified factors. I found strong evidence that genetic adaptation of zebra mussel populations to local habitat conditions had influenced the genetic constitution of the populations. Moreover, by establishing the biogeographical baseline of molecular variance in the study area, I laid the foundation for interpreting population genetic results in ecotoxicological experiments in this region.rnIn a cooperation project with the Department of Zoology of the University of Zagreb, I elaborated an integrated approach in biomonitoring with D. polymorpha by combining the analysis techniques of microsatellite analysis, Comet assay and micronucleus test (MNT). This approach was applied in a case study on freshwater contamination by an effluent of a wastewater treatment plant (WWTP) in the River Drava (Croatia) and a complementary laboratory experiment. I assessed and compared the genetic status of two zebra mussel populations from a contaminated and a reference site. Microsatellite analysis suggested that the contaminated population had undergone a genetic bottleneck, caused by random genetic drift and selection, whereas a bottleneck was not detected in the reference population. The Comet assay did not indicate any difference in DNA damage between the two populations, but MNT revealed that the contaminated population had an increased percentage of micronuclei in hemocytes in comparison to the reference population. The laboratory experiment with mussels exposed to municipal wastewater revealed that mussels from the contaminated site had a lower percentage of tail DNA and a higher percentage of micronuclei than the reference population. These differences between populations were probably caused by an overall decreased fitness of mussels from the contaminated site due to genetic drift and by an enhanced DNA repair mechanism due to adaptation to pollution in the source habitat. Overall, the combination of the three biomarkers provided sufficient information on the impact of both treated and non-treated municipal wastewater on the genetics of zebra mussels at different levels of biological organization.rnIn my thesis, I could show that the newly established marker set of six microsatellite loci provided reliable and informative data for population genetic analyses of D. polymorpha. The adaptation of the analyzed zebra mussel populations to the local conditions of their habitat had a strong influence on their genetic constitution. We found evidence that the different genetic constitutions of two populations had influenced the outcome of our ecotoxicological experiment. Overall, the integrated approach in biomonitoring gave comprehensive information about the impact of both treated and non-treated municipal wastewater on the genetics of zebra mussels at different levels of biological organization and was well practicable in a first case study.