1,720,983 research outputs found
Mechanical aspects of biological and biomedical systems
Full text linkI sistemi biologici e biomedici presentano delle caratteristiche tali da renderli a tutti gli effetti assimilabili a dei sistemi meccanici complessi. In questo lavoro di tesi si presentano le ricerche condotte in due diversi ambiti di studio della biomeccanica. Nella prima parte, sono stati studiati gli effetti degli ultrasuoni a bassa intensità sulle cellule tumorali. Diversi studi dimostrano che il calore, la cavitazione e l'ipertermia indotti dagli ultrasuoni possono produrre effetti antitumorali. Inoltre, la terapia ad ultrasuoni a bassa intensità può svolgere un ruolo positivo nella cura del cancro causando danni alla membrana delle cellule tumorali, inducendo l'apoptosi e migliorando l'effetto dei farmaci anticancro. In questo lavoro vengono presentati gli effetti degli ultrasuoni a bassa intensità su due particolari linee cellulari tumorali: l'osteosarcoma MG63 ed il linfoma U937. Le cellule di osteosarcoma MG63 sono state sonicate per 180 secondi a frequenze fisse comprese tra 400 e 1.000 kHz. I risultati hanno mostrato che la mortalità delle cellule MG-63 raggiungeva valori pari a oltre il 60% per valori di frequenza pari a 1.000 kHz. Inoltre, il monitoraggio del comportamento cellulare dopo il trattamento con ultrasuoni ha mostrato che il trattamento produce effetti sulla proliferazione cellulare anche dopo la sonicazione. Risultati interessanti sono stati ottenuti anche sulla linea cellulare U937, per la quale il trattamento con ultrasuoni a frequenza fissa a 1 MHz ha determinato una mortalità cellulare pari a oltre l'80%. Nella seconda parte di questo lavoro è stato studiato il comportamento meccanico degli allineatori ortodontici. Gli allineatori sono dispositivi medici in grado di produrre il movimento di uno o più denti attraverso una serie di passaggi decisi dall'ortodontista. In particolare, sono stati considerati due diversi aspetti del comportamento meccanico di questi dispositivi. In primo luogo, sono state considerate le pressioni specifiche esercitate dagli allineatori sui denti e le aree dove vengono applicate tali pressioni. I risultati hanno mostrato che le pressioni esercitate dall'allineatore non sono distribuite uniformemente su tutta la superficie del dente e che, per diversi allineatori realizzati su uno stesso modello, le aree di applicazione delle forze non erano identiche, poiché influenzate da fattori risultanti dai processi di fabbricazione. Un secondo studio ha investigato la stabilità dimensionale degli allineatori dopo l'applicazione di stress dinamico in vivo e stress statico in vitro. Sono stati testati tre diversi materiali tipicamente utilizzati per la realizzazione degli allineatori (PET-G, PET e SmartTrack®). Gli effetti dello stress dinamico prodotto in vivo sono stati valutati facendo indossare ad un paziente i tre diversi allineatori per un periodo di due settimane. Gli effetti dello stress statico, invece, sono stati valutati sottoponendo gli allineatori ad un carico statico mediante macchina di prova. Gli allineatori testati sono stati scansionati e misurati al fine di valutare la loro stabilità dimensionale dopo i diversi tipi di sollecitazioni. I risultati hanno mostrato che gli allineatori PET sembrano avere la più bassa percentuale di deformazione, mentre gli allineatori PET-G e SmartTrack® mostrano una deformazione ridotta che va dalla zona posteriore a quella anteriore. Infine, è stato dimostrato che il contatto con la saliva umana induce una maggiore deformazione.Biological and biomedical systems present characteristics that make them equivalent to complex mechanical systems. In this thesis, the research conducted on two different fields of biomechanics is presented. In the first part, the effects of low intensity ultrasound on cancer cells were studied. Several studies show that heat, cavitation and hyperthermia induced by ultrasound can produce anticancer effects. In addition, low intensity ultrasound therapy can play a positive role in the treatment of cancer by causing damage to the cancer cells membrane, inducing apoptosis and improving the effect of anticancer drugs. In this paper, the effects of low intensity ultrasound on two particular tumour cell lines are presented: the osteosarcoma MG63 and the U937 lymphoma. MG63 osteosarcoma cells were sonicated for 180 seconds at fixed frequencies between 400 and 1,000 kHz. Results showed that mortality of MG-63 cells reached values of over 60% for 1,000 kHz frequency. Furthermore, monitoring cellular behaviour after ultrasound treatment showed that the treatment has effects on cell proliferation even after sonication. Interesting results were also obtained on U937 cell line, for which the treatment with fixed frequency ultrasound at 1 MHz resulted in a cell mortality of over 80%. In the second part of this work the mechanical behaviour of orthodontic aligners was studied. The aligners are medical devices able to produce the movement of one or more teeth through a number of steps decided by the orthodontist. In particular, two different aspects of the mechanical behaviour of these devices have been considered. First, the specific pressures exerted by the aligners on the teeth and the areas on which these pressures are applied were considered. Results showed that pressures exerted by the aligner are not uniformly distributed over the entire surface of the tooth and that, for different aligners made on the same model, the areas of forces application were not identical, since they were influenced by factors resulting from the production processes. A second study investigated the dimensional stability of the aligners after applying dynamic stress in vivo and static stress in vitro. Three different materials typically used for making the aligners (PET-G, PET and SmartTrack®) were tested. The effects of dynamic stress produced in vivo were evaluated by having a patient wear the three different aligners over a two-week period. The effects of static stress were assessed by subjecting the aligners to a static load using a testing machine. The tested aligners were scanned and measured, in order to evaluate their dimensional stability after different types of stress. Results showed that the PET aligners appeared to have the lowest deformation percentage, while the PET-G and SmartTrack® aligners showed a reduced deformation going from the back to the front area. Finally, contact with human saliva seemed to induce greater deformation
sj-docx-1-sdj-10.1177_03093247221150044 – Supplemental material for Finite element implementation of the aortic double-dispersion fibre model and development of a predictive damage model
No full textSupplemental material, sj-docx-1-sdj-10.1177_03093247221150044 for Finite element implementation of the aortic double-dispersion fibre model and development of a predictive damage model by A. Corvi and L. Collini in The Journal of Strain Analysis for Engineering Design</p
Valutazione di forze esterne nella manipolazione
No full textAl fine di determinare l'entità delle forze scambiate con l'ambiente estemo dalle dita della mano, sono stati progettati, realizzati e tarati due trasduttori: uno per la misura delle forze scambiate nella "presa di precisione" (pinch), l'altro nella "presa di forza" (grasp).
I dati ottenibili da tali trasduttori servono di ausilio allo studio del problema miodinamico inverso in quanto, insieme con i dati antropometrici e cinematici, consentono di definire il modello meccanico delle strutture articolari.
I trasduttori sono stati strumentati con estensimetri elettrici a resistenza e sono stati sottoposti a taratura statica e dinamica realizzando apposite attrezzature.
Sono stati conseguiti risultati preliminari su soggetti sani in compiti del tipo: sviluppo di forza massima, mantenimento di una forza costante e cambiamenti ripetitivi veloci di forza.
La memoria descrive i dispositivi messi a punto, le prove di taratura e riporta i primi riSultati delle prove effettuate
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Appropriate Similarity Measures for Author Cocitation Analysis
Full text linkWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
Dispelling the Myths Behind First-author Citation Counts
Full text linkWe conducted a full-scale evaluative citation analysis study of scholars in the XML research field to explore just how different from each other author rankings resulting from different citation counting methods actually are, and to demonstrate the capability of emerging data and tools on the Web in supporting more realistic citation counting methods. Our results contest some common arguments for the continued
use of first-author citation counts in the evaluation of scholars, such as high correlations between author rankings by first-author citation counts and other citation
counting methods, and high costs of using more realistic citation counting methods that are not well-supported by the ISI databases. It is argued that increasingly available digital full text research papers make it possible for citation analysis studies to go beyond what the ISI databases have directly supported and to employ more
sophisticated methods
koamabayili/VECTRON-author-checklist: VECTRON author checklist
No full textWe have done our best to complete the author checklist relating to the use of animals in the hut study. Note that the objective for the hut study was to evaluate the IRS treatment applications for residual efficacy against Anopheles mosquitoes, including the local An. coluzzii mosquito population. Cows were only used to attract mosquitoes into the huts and no tests were carried out directly on the cows. The author checklist is intended for use with studies where experiments are carried out on animals, which is why we have had such difficulty in completing this for the hut study, as many of the questions do not relate to how the cows were used
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