2,393 research outputs found
Frammenti per narrare la storia : Torino e l'evoluzione del mosaico dala produzione artistica alla cultura edilizia nel XX secolo, cultura, tecnologia, conservazione
No full textIl "Circolo delle Fibule" di Sirolo-Numana
No full textLa conoscenza delle Marche di epoca preromana è affidata in gran parte allo studio delle testimonianze provenienti dalle necropoli dei diversi siti della regione, abitati un tempo da popolazioni che per conven- zione sono indicate col nome di Piceni. Grazie a ricerche sempre più approfondite, il patrimonio archeolo- gico piceno sta rivelando in anni recenti una notevole varietà, indice dello sviluppo di molti centri durante l’età del Ferro e di proficui contatti culturali con altre regioni all’interno e all’esterno dei confini dell’Italia preromana.
Tra i principali centri piceni si segnala in particolar modo l’antica Numana, situata sulla costa adriatica alle pendici del Monte Conero, nell’odierna provincia di Ancona. Le ricchissime necropoli locali comprendono circa 2000 sepolture e testimoniano la crescita dell’insediamento costiero attraverso molteplici fasi, dal IX secolo a.C. fino alla romanizzazione, al centro di legami a lungo raggio che inclusero il Piceno in una rete via via sempre più fitta, estesa tra la Grecia, l’area balcanica, la penisola italica e l’area mitteleuropea. Nel novero dei più importanti ritrovamenti locali, il »Circolo delle Fibule« si segnala in particolar modo per la composizione dei corredi funerari delle sue nove tombe, rese celebri a causa del numero esorbitante di fibule deposte al loro interno – oltre 1200 esemplari, di tipologie e materiali differenti. Scoperto nel 1970 e mai pubblicato integralmente, questo contesto chiave dell’archeologia picena è qui presentato all’interno di uno studio specifico, che illustra la varietà dei materiali in esso rinvenuti e la complessità del costume fu- nerario locale. Attraverso l’esame dei corredi funerari si coglie un’eco dei processi di strutturazione sociale in atto a Numana tra la fine del VII secolo a. C. e il principio del V secolo a. C., in bilico tra un forte conserva- torismo e le prime aperture a quei contatti internazionali che, nel corso del V secolo a. C., avrebbero fatto di questo sito uno dei principali scali adriatici
Circadian rhythms of rat pancreatic acinar cells
No full textOn the basis of the circadian oscillations of the rat's exocrine pancreatic function and previous reports on concomitant ultrastructural changes in the pancreatic tissue, we analysed stereologically the circadian rhythmicity in the structure of this organ.
Twenty-four male Wistar rats, four and a half months old, were singly housed two months before the experiment in a lighting regimen LD=12:12, constant environmental temperature and relative humidity, with food and water ad libitum. The experiment was performed in winter. The rats were randomly divided into 6 balanced groups and killed under ether anesthesia at 6 equidistant time points in 24 hours. The pancreatic tissue was fixed in glutaraldehyde and osmium and embedded in Epon. 1 mu m thick sections were examined by light microscopy for the evaluation by stereological methods of: a) volume fractions of the different parenchymal components of the exocrine pancreas; b) surface fractions of acinar cell faces; c) size distribution of acinar cell nuclei, their number per unit tissue volume and their mean diameter.
Single cosinor method analysis of the data demonstrated statistically significant circadian rhythms for the volume fraction of the cytoplasm of acinar cells and the volume fractions of pancreatic acini and acinar cells.
The volume fraction of the cytoplasm of the rat pancreatic acinar cells undergoes circadian oscillations with the highest values at the end of the light span; this rise precedes the well-known physiological nocturnal surge of pancreatic digestive enzymes. Our findings further support the hypothesis of a close relationship between pancreatic cell structure and its function
EFFECT OF CROSSLINKING PROCESS PARAMETERS ON THE RHEOLOGICAL BEHAVIOR OF A POLYDIMETHYLSILOXANE
No full textPolydimethylsiloxane crosslinking kinetics: A systematic study on Sylgard184 comparing rheological and thermal approaches
No full textIn this work a systematic investigation of crosslinking kinetics of Sylgard184 polydimethylsiloxane is performed in both isothermal and dynamic conditions. The results are discussed in terms of two conversions, αC and αR determined by thermal and rheological analysis, respectively. Thermal analysis can well detect the first stage of the reaction, while rheological analysis starts being sensitive only at longer time. However, once the rheological response is observable, it changes with time faster than the calorimetric one. From rheology experiments it comes out that the gel point occurs at αR = 0.53, independently of the applied thermal history. At gel point, αC is around 0.30 indicating that about 30% of the bonds involved in the crosslinking process is enough to create an infinite network. A modified version of the Kamal's autocatalytic model allows to fit and predict the experimental findings from both the techniques; however, two distinct sets of parameters have been used. The results of this work may be a useful tool to design appropriate curing cycles for the preparation of Sylgard184
Influence of curing thermal history on cross-linking degree of a polydimethylsiloxane: Swelling and mechanical analyses
No full textIn this work, the change of the elastic properties induced by a change in cross-linking conditions of polydimethylsiloxane is investigated by measuring its shear modulus by dynamic mechanical analysis and correlating it to that predicted
from swelling measurements. Polymer cross-linking is performed at different curing temperatures reached with ramps at different heating rates. From both mechanical and swelling measurements, the molecular weight between cross-links, MC, is determined, and its dependency on the applied thermal history is analyzed. The main results are: (i) the elastic modulus of the cured material is not significantly affected by the heating rate adopted, while (ii) the curing temperature has a significant influence on the polydimethylsiloxane mechanical properties. In addition, (iii) MC evaluation from swelling measurements is in good agreement with that estimated from mechanical measurements when appropriate theories are considered. This last result suggests that swelling experiments can be considered as a reliable tool to predict the elastic modulus of the polydimethylsiloxane studied. The quantitative information reported in this paper, also obtainable by the suggested method if other thermal curing histories are applied, is extremely useful for the proper design of devices based on polydimethylsiloxane
Minima cascologica. A proposito di alcune appliques bronzee figurate di elmi etruschi ed italici
No full textSu diversi tipi di elmi etruschi ed italici era presente un lophos, ssato tramite piccole appliques in bronzo fuso, inserite tramite perni o saldate sulla calotta. Verso la fine del VI secolo a. C., con il tipo »Vetulonia« degli elmi Negau, ebbe inizio la produzione di una serie caratteristica di appliques figurate, ben riconoscibili per le scelte iconografiche ricorrenti e per gli aspetti stilistici, affini a quelli della produzione bronzistica vulcente. Simili appliques decoravano però anche gli elmi italico-calcidesi e i cosiddetti »Prunkhelme«. Accanto a un catalogo di oltre 150 appliques, si presentano alcune riflessioni circa la loro combinazione e il significato del loro utilizzo su elmi di diverso tipo nel corso del V secolo a. C
Aspekte der Herstellungstechnik der etruskischen Stabdreifüsse
No full textDating between the 7th and the 5th century B. C. E., rod tripods represent some of the most elaborate creations of Etruscan bronze work. These objects reveal a strong variety of solutions adopted for the construction of their individual parts as well as for their assemblage. By the end of the 6th and the beginning of the 5th century B. C. E. Etruscan rod tripod construction became more regular and could be interpreted in some cases as a marker of specific workshops
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