1,720,963 research outputs found
Due approcci perfezionati allo studio della competizione in comunità batteriche
No full textMicrobial communities are ubiquitous and play crucial roles in many natural processes (e.g., biogeochemical cycles and industrial processes). Despite their importance, however, there are still many aspects of microbial community dynamics that we do not fully understand. In this Thesis we provide two improvements to the approach used to study competition in microbial communities that can help us in this direction. The theoretical framework on which we build is MacArthur's consumer-resource model, commonly used to describe mathematically competition between microbes.
The first improvement consists in introducing an optimization principle in the dynamics of such systems, so that we can include in mathematical models the well known fact that microbes can switch between different energy sources depending on environmental conditions. We require that each species does so in order to maximize its own relative fitness, and we explore the consequences of this choice on the biodiversity of competitive communities, comparing also the model with experimental data.
Then, we reconsider the consumer-resource framework in light of experimental evidence showing that the allocation of cellular internal resources affects microbial growth. This new framework describes community dynamics at an intermediate level of complexity, allowing us to explore the relationship between population dynamics and microbial metabolism, which has attracted the attention of the scientific community in recent years. We compare the predictions of our new model with experimental data in a simple case, and then we study its predictions analytically and numerically to understand how biodiversity in competitive communities can be maintained.Le comunità microbiche sono onnipresenti in natura, e giocano ruoli fondamentali in moltissimi processi naturali (come cicli biogeochimici e processi di produzione industriale). Nonostante la loro importanza, ci sono ancora molti aspetti delle comunità microbiche che non comprendiamo appieno. In questa Tesi vengono proposti due miglioramenti all'approccio nello studio della competizione in comunità microbiche che possono aiutarci in questa direzione. Il framework teorico sul quale si fonda il lavoro di questa Tesi è il modello consumer-resource di MacArthur, comunemente utilizzato per descrivere matematicamente la competizione fra specie microbiche.
Il primo miglioramento consiste nell'introduzione di un principio di ottimizzazione nella dinamica di questo tipo di sistemi, di modo tale da includere nei modelli matematici il fatto (ben noto sperimentalmente) che i batteri possono passare da una fonte di energia all'altra a seconda delle condizioni ambientali. In particolare, in questa Tesi si impone che ogni specie faccia ciò con l'obiettivo di massimizzare il proprio tasso di crescita, e si esplorano le conseguenze di questa scelta sulla biodiversità di comunità competitive, confrontando anche il modello con dati sperimentali.
Dopodiché, in questa Tesi il consumer-resource framework viene riconsiderato alla luce di evidenze sperimentali che mostrano come l'allocazione delle risorse cellulari interne influenzi la crescita di specie microbiche. Questo nuovo framework descrive le comunità a un livello intermedio di complessità, consentendo di esplorare la relazione fra dinamica delle popolazioni e metabolismo microbico, una relazione che ha attirato l'attenzione della comunità scientifica di recente. Le predizioni di questo nuovo framework vengono confrontate con dati sperimentali in un caso semplice, dopodiché il modello e le sue predizioni vengono studiati analiticamente e numericamente per capire come la biodiversità possa essere mantenuta in comunità competitive
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
Glycidyl Azide-butadiene Block Copolymers: Synthesis from the Homopolymers and a Chain Extender
No full textGlycidyl azide polymer (GAP) is an “energetic” alternative
to hydroxyl-terminated polybutadiene (HTPB), but
has poorer mechanical properties. Since HTPB-GAP mechanical
blends are markedly biphasic, the use of block copolymers
may be the solution to join the advantages of
both. The copolymers were synthesized from the homopolymers
by using two chain extenders: hexamethylene diisocyanate
(HDI) and adipoyl chloride (AdCl). Both reagents
gave homogeneous and stable polymeric mixtures, but
with HDI there are risks of gelation during reaction. Therefore,
the product obtained with AdCl is the best candidate
to be used as binder or as compatibilizer in GAP-HTPB mechanical
blends
Author-wise bibliometric analysis based on entropy.
No full textAuthor-wise bibliometric analysis based on entropy.</p
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