64 resultados para reti power law social network analysis sna borsa italiana misure di centralità e potere scale free


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Revisió sobre l’eficàcia de les intervencions dirigides a cuidadorsinformals de malalts amb demència per a reduir els nivells de morbiditatpsicològicaAntecedentsL’envelliment de la població està relacionat amb l’augment de la prevalença dedemències tals com la malaltia d’Alzheimer. El caràcter progressiu, incapacitanti irreversible de la malaltia d’Alzheimer comporta dependència i demanda,obligant l’aparició d’un cuidador informal per cobrir les necessitats del malalt.Amb l’evolució de la malaltia, augmenta l’exigència de les cures i el cuidador esveu en risc de patir alteracions a qualsevol nivell, principalment a nivellpsicològic.Objectius1. Avaluar l’efectivitat de les intervencions dirigides a cuidadors informals depersones amb demència per a reduir la morbiditat psicològica, segons latipologia de les intervencions i els seus components.2. Avaluar l’efectivitat de les intervencions dirigides a cuidadors informals depersones amb demència per a reduir la morbiditat psicològica, segons lescaracterístiques sociodemogràfiques del cuidador i la persona que rep lescures, el tipus de càrrega i els instruments de mesura.Material i mètodesEs va realitzar una revisió bibliogràfica en les bases de dades: MEDLINEPubMed, CSIC-IME, CUIDEN i Biblioteca Cochrane Plus sobre lesintervencions dirigides a cuidadors informals de demència o Alzheimerd’estudis publicats entre el gener de 2002 i febrer de 2013. Els criteris d’inclusióvan ser: cuidadors informals que convisquessin amb la persona a qui donen lescures i sense remuneració econòmica, persones amb demència o Alzheimer noinstitucionalitzades, intervencions comparades entre un grup experimental i ungrup control, prioritat per revisions sistemàtiques i metanàlisis. La mostra finalla van composar 7 estudis.ResultatsLes diferents intervencions analitzades van mostrar dades estadísticamentsignificatives tot i produir efectes discrets en les diferents variables demorbiditat psicològica. Les intervencions psicoeducatives i les intervencionsdirigides als pacients van resultar efectives en la millora de la sensació debenestar i la simptomatologia del malalt. Les intervencions psicològiques vanincidir en la sobrecàrrega i la depressió. Les intervencions de suport vanproduir un augment dels coneixements, habilitats i de la xarxa social delcuidador. El dia de descans va disminuir l’estrès, l’ansietat i la càrrega objectivaperò els efectes van ser a curt termini. Les intervencions múltiplesestructurades van mostrar una disminució del risc d’institucionalització. Lesintervencions centrades en la resolució de problemes, superiors a 6 sessions oaquelles que havien realitzat seguiment, van mostrar efectes a llarg termini finsals 12 mesos. Altres intervencions pràctiques com les realitzades al domicili oamb tecnologia, no van mostrar suficient evidència científica. El sexe i l’edat delcuidador així com la relació de parentesc amb el malalt van mostrar diferènciesen els efectes de les intervencions.ConclusionsLes intervencions s’han de planificar en funció de les necessitats del cuidadorja que no hi ha cap intervenció que incideixi en totes les variables de morbiditatpsicològica. La variabilitat de tipologia i composició de les intervencions, lesdiferències sociodemogràfiques del cuidador i la persona que rep les cures i lescaracterístiques dels estudis influeixen en l’heterogeneïtat de resultats de larevisió. Aquests fets limiten la contundència de resultats pel que cal seguirinvestigant

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We propose a procedure for analyzing and characterizing complex networks. We apply this to the social network as constructed from email communications within a medium sized university with about 1700 employees. Email networks provide an accurate and nonintrusive description of the flow of information within human organizations. Our results reveal the self-organization of the network into a state where the distribution of community sizes is self-similar. This suggests that a universal mechanism, responsible for emergence of scaling in other self-organized complex systems, as, for instance, river networks, could also be the underlying driving force in the formation and evolution of social networks.

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We propose a class of models of social network formation based on a mathematical abstraction of the concept of social distance. Social distance attachment is represented by the tendency of peers to establish acquaintances via a decreasing function of the relative distance in a representative social space. We derive analytical results (corroborated by extensive numerical simulations), showing that the model reproduces the main statistical characteristics of real social networks: large clustering coefficient, positive degree correlations, and the emergence of a hierarchy of communities. The model is confronted with the social network formed by people that shares confidential information using the Pretty Good Privacy (PGP) encryption algorithm, the so-called web of trust of PGP.

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Purpose This paper aims to analyse various aspects of an academic social network: the profile of users, the reasons for its use, its perceived benefits and the use of other social media for scholarly purposes. Design/methodology/approach The authors examined the profiles of the users of an academic social network. The users were affiliated with 12 universities. The following were recorded for each user: sex, the number of documents uploaded, the number of followers, and the number of people being followed. In addition, a survey was sent to the individuals who had an email address in their profile. Findings Half of the users of the social network were academics and a third were PhD students. Social sciences scholars accounted for nearly half of all users. Academics used the service to get in touch with other scholars, disseminate research results and follow other scholars. Other widely employed social media included citation indexes, document creation, edition and sharing tools and communication tools. Users complained about the lack of support for the utilisation of these tools. Research limitations/implications The results are based on a single case study. Originality/value This study provides new insights on the impact of social media in academic contexts by analysing the user profiles and benefits of a social network service that is specifically targeted at the academic community.

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Learning objects have been the promise of providing people with high quality learning resources. Initiatives such as MIT Open-CourseWare, MERLOT and others have shown the real possibilities of creating and sharing knowledge through Internet. Thousands of educational resources are available through learning object repositories. We indeed live in an age of content abundance, and content can be considered as infrastructure for building adaptive and personalized learning paths, promoting both formal and informal learning. Nevertheless, although most educational institutions are adopting a more open approach, publishing huge amounts of educational resources, the reality is that these resources are barely used in other educational contexts. This paradox can be partly explained by the dificulties in adapting such resources with respect to language, e-learning standards and specifications and, finally, granularity. Furthermore, if we want our learners to use and take advantage of learning object repositories, we need to provide them with additional services than just browsing and searching for resources. Social networks can be a first step towards creating an open social community of learning around a topic or a subject. In this paper we discuss and analyze the process of using a learning object repository and building a social network on the top of it, with respect to the information architecture needed to capture and store the interaction between learners and resources in form of learning object metadata.

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In this paper we discuss and analyze the process of using a learning object repository and building a social network on the top of it, including aspects related to open source technologies, promoting the use of the repository by means of social networks and helping learners to develop their own learning paths.

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La pérdida de autonomía a edades avanzadas no se asocia únicamente con el envejecimiento sino también con características del entorno físico y social. Investigaciones recientes han demostrado que la red social, la integración social y la participación, actúan como predictores de la discapacidad en la vejez. El objetivo de este trabajo es nalizar el efecto de la red social sobre el nivel de autonomía(en términos de discapacidad instrumental y básica) en etapas iniciales de la vejez.

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Optimization models in metabolic engineering and systems biology focus typically on optimizing a unique criterion, usually the synthesis rate of a metabolite of interest or the rate of growth. Connectivity and non-linear regulatory effects, however, make it necessary to consider multiple objectives in order to identify useful strategies that balance out different metabolic issues. This is a fundamental aspect, as optimization of maximum yield in a given condition may involve unrealistic values in other key processes. Due to the difficulties associated with detailed non-linear models, analysis using stoichiometric descriptions and linear optimization methods have become rather popular in systems biology. However, despite being useful, these approaches fail in capturing the intrinsic nonlinear nature of the underlying metabolic systems and the regulatory signals involved. Targeting more complex biological systems requires the application of global optimization methods to non-linear representations. In this work we address the multi-objective global optimization of metabolic networks that are described by a special class of models based on the power-law formalism: the generalized mass action (GMA) representation. Our goal is to develop global optimization methods capable of efficiently dealing with several biological criteria simultaneously. In order to overcome the numerical difficulties of dealing with multiple criteria in the optimization, we propose a heuristic approach based on the epsilon constraint method that reduces the computational burden of generating a set of Pareto optimal alternatives, each achieving a unique combination of objectives values. To facilitate the post-optimal analysis of these solutions and narrow down their number prior to being tested in the laboratory, we explore the use of Pareto filters that identify the preferred subset of enzymatic profiles. We demonstrate the usefulness of our approach by means of a case study that optimizes the ethanol production in the fermentation of Saccharomyces cerevisiae.

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The loss of autonomy at advanced ages is not only associated with ageing, but also with the characteristics of the physical and social environment. Recent investigations have shown that social networks, social engagement and participation act like predictors of disability among the elderly. The aim of this study is to determine whether social networks are related to the development and progression of disability in the early years of old age. The source of data is the first wave of the survey "Processes of Vulnerability among Spanish Elderly", carried out in 2005 to a sample of 1 244 individuals. The population object of study is the cohort aged 70 to 74 years in metropolitan areas (Madrid and Barcelona) and not institutionalized. Disability is measured by the development of basic activities of daily life (ADL), and instrumental activities of daily life (IADL). The structural aspects of the social relationships are measured through the diversity of social networks and participation. We used the social network index (SNI). For each point over the SNI, the risk of developing any type of disability decreased by 49% (HR = 0.51, 95%CI = 0.31-0.82). The SNI was a decisive factor in all forecasting models constructed with some hazard ratios (HR) that ranged from 0.29 (95%CI = 0.14-0.59) in the first model to 0.43 (95%CI 0.20-0.90) in the full model. The results of the present study showed a strong association between an active social life, emotional support provided by friends and confidents and disability. These findings suggest a protective effect of social networks on disability. Also, these results indicate that some family and emotional ties have a significant effect on both the prevalence and the incidence of disability.

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Purpose- This paper aims to analyse various aspects of an academic social network: the profile of users, the reasons for its use, its perceived benefits and the use of other social media for scholarly purposes. Design/methodology/approach- The authors examined the profiles of the users of an academic social network. The users were affiliated with 12 universities. The following were recorded for each user: sex, the number of documents uploaded, the number of followers, and the number of people being followed. In addition, a survey was sent to the individuals who had an email address in their profile. Findings- Half of the users of the social network were academics and a third were PhD students. Social sciences scholars accounted for nearly half of all users. Academics used the service to get in touch with other scholars, disseminate research results and follow other scholars. Other widely employed social media included citation indexes, document creation, edition and sharing tools and communication tools. Users complained about the lack of support for the utilisation of these tools. Research limitations/implications- The results are based on a single case study. Originality/value- This study provides new insights on the impact of social media in academic contexts by analysing the user profiles and benefits of a social network service that is specifically targeted at the academic community.

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We report on the results of the spectral and timing analysis of a BeppoSAX observation of the microquasar system LS 5039/RX J1826.2-1450. The source was found in a low-flux state with Fx(1-10 keV)= 4.7 x 10^{-12} erg cm^{-2} s^{-1}, which represents almost one order of magnitude lower than a previous RXTE observation 2.5 years before. The 0.1--10 keV spectrum is described by an absorbed power-law continuum with photon-number spectral index Gamma=1.8+-0.2 and hydrogen column density of NH=1.0^{+0.4}_{-0.3} x 10^{22} cm^{-2}. According to the orbital parameters of the system the BeppoSAX observation covers the time of an X-ray eclipse should one occur. However, the 1.6-10 keV light curve does not show evidence for such an event, which allows us to give an upper limit to the inclination of the system. The low X-ray flux detected during this observation is interpreted as a decrease in the mass accretion rate onto the compact object due to a decrease in the mass-loss rate from the primary.

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Wide-range spectral coverage of blazar-type active galactic nuclei is of paramount importance for understanding the particle acceleration mechanisms assumed to take place in their jets. The Major Atmospheric Gamma Imaging Cerenkov (MAGIC) telescope participated in three multiwavelength (MWL) campaigns, observing the blazar Markarian (Mkn) 421 during the nights of April 28 and 29, 2006, and June 14, 2006. Aims. We analyzed the corresponding MAGIC very-high energy observations during 9 nights from April 22 to 30, 2006 and on June 14, 2006. We inferred light curves with sub-day resolution and night-by-night energy spectra. Methods. MAGIC detects γ-rays by observing extended air showers in the atmosphere. The obtained air-shower images were analyzed using the standard MAGIC analysis chain. Results. A strong γ-ray signal was detected from Mkn 421 on all observation nights. The flux (E > 250 GeV) varied on night-by-night basis between (0.92±0.11) × 10-10 cm-2 s-1 (0.57 Crab units) and (3.21±0.15) × 10-10 cm-2 s-1 (2.0 Crab units) in April 2006. There is a clear indication for intra-night variability with a doubling time of 36± min on the night of April 29, 2006, establishing once more rapid flux variability for this object. For all individual nights γ-ray spectra could be inferred, with power-law indices ranging from 1.66 to 2.47. We did not find statistically significant correlations between the spectral index and the flux state for individual nights. During the June 2006 campaign, a flux substantially lower than the one measured by the Whipple 10-m telescope four days later was found. Using a log-parabolic power law fit we deduced for some data sets the location of the spectral peak in the very-high energy regime. Our results confirm the indications of rising peak energy with increasing flux, as expected in leptonic acceleration models.

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This paper describes Question Waves, an algorithm that can be applied to social search protocols, such as Asknext or Sixearch. In this model, the queries are propagated through the social network, with faster propagation through more trustable acquaintances. Question Waves uses local information to make decisions and obtain an answer ranking. With Question Waves, the answers that arrive first are the most likely to be relevant, and we computed the correlation of answer relevance with the order of arrival to demonstrate this result. We obtained correlations equivalent to the heuristics that use global knowledge, such as profile similarity among users or the expertise value of an agent. Because Question Waves is compatible with the social search protocol Asknext, it is possible to stop a search when enough relevant answers have been found; additionally, stopping the search early only introduces a minimal risk of not obtaining the best possible answer. Furthermore, Question Waves does not require a re-ranking algorithm because the results arrive sorted

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Past research in using ICTs (Information and Communication Technologies) in interpersonal communication showed that age plays an important role. There is a general assumption that the elderly are left behind regarding the adoption and the use of ICTs. Furthermore, elders tend to use ICTs mainly for instrumental purposes and the use is rather non-sophisticated. When elders are using ICTs to maintain their social network, similar patterns could be found: They start using internet, or intensify its use, when their children move abroad while they might decrease using the tool if the motivation ends. In this research we explore elders' incentives to go online and use internet services to communicate; the type of agencies they use to communicate with children and grandchildren abroad; and the situations that make them stop using the ICTs or even reject internet mediated communications. We base our discussion on the empirical evidence the two authors gathered in different cities and countries: Barcelona, Romania, Toronto, Los Angeles, Montevideo and Lima, through semi-structured interviews and observation, with people aged 60 years old and over. The results show that the ability for using ICT tools in an autonomous way is a better explanation than age. In this, we distinguish between assisted users and autonomous users. We found that oldest seniors and those seniors who are less socially active are more likely to be assisted users than those who are socially or professionally active. For them communication with their children and grandchildren abroad follows no agency or it is mediated by significant others from their local social network, who are able to use ICTs and select specific information to share, in the second step, with the elder. For some younger participants the use of ICTs is rather situational and imposed by their children or grandchildren, who installed the tool in the first place and assisted them in using it. Finally, other elders describe a proficient and independent use of ICTs so they use the devices and services the way they want to.We discuss the implications of the patterns in using ICTs, for elders' social life and their relationships with children and grandchildren. First, we emphasis the fact that those elders rejecting the ICTs or being unskilled in using them to communicate might be left out from their family circle, particularly when children are abroad -they would experience more isolation. Second, we underline the fact that when children and grandchildren are the ones that control the ICTs used by their parents and grandparents, they are controlling also the information flow and this will redefine the power relations between elders and their younger relatives.

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Peer-reviewed