1,721,187 research outputs found
Family Boundaries: a Study on 'Emergency Fostering' in Reggio Emilia
No full textThe family is the primary place where relational experiences occur; the place par excellence of cognitive, social and emotional ties, but not always able to implement these dimensions. The foster is a response to the problems of the child, when its family of origin is not adequate to provide for its growth and education. Welcoming a baby is an event rich in complexity: it is therefore essential to analyze the elements that characterize it, starting from its structural problems, such as the reasons that determine this choice and the educational implications of it (Pati, 2008). Fostering a child cannot be achieved by isolated individuals or families. Teamwork is needed: it's important to consider all those involved, starting by the child’s native family, the new-family ‘inclusion policy’ and the Social Services (Grana, 2004). Crucial are the expectations and relational dynamics that are created between the actors involved and their experience, but especially the emotional bond that is built and that gives life to countless changes that affect the psychology of the family. The role of foster parents is very complex and difficult and is characterized, psychologically, from the distinctive features that place the role of new parents at the ‘family boundaries’ (Scabini, Cigoli, 2000). This research provides a nuanced picture of the foster’s complexity, using two different methodologies. One presents a collection of statistics and documents, focusing on how the "Network of families for emergency" manage to support families in need. A second part of the study concerns a qualitative research on parental experiences, to understand the dynamics of parenting through interviews, conversations and diaries by and with foster families (Demetrio, 1996; Lewis,2001). The analysis of collected materials shows some fundamental elements that characterize the foster family: availability, cohesiveness, non-judgmental attitude and above all openness to others (Cerrai et al.,2007; Torre, 2008)
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
ON THE LENSE-THIRRING EFFECT IN ACCRETING BLACK HOLE SYSTEMS
Full text linkBlack holes are a natural prediction of the theory of General Relativity. Their gravitational field is strong enough to prevent light from escaping and to distort the space and the flow of time around them.
Since light cannot escape, black holes can be detected when they are accreting mass from the surrounding gas or through the dynamics of nearby stars. Accretion of gas onto black holes is the most efficient mechanism that converts matter into energy. The investigation of this complex physical mechanism, in terms of both radiative emission and mechanical outflow, is crucial in order to understand the observations of accreting sources.
In this context the Lense-Thirring or `frame dragging' effect becomes relevant since it warps the accretion disc around the black hole. The presence of warps within the disc can lead to its rigid precession around the black hole that results in a modulation of the emitted flux. Measuring the period and the duration of the quasi-periodic behaviour in the light curve, the black hole fundamental parameters (mass and spin) can be inferred.
This thesis is devoted to the study of warps and rigid precession in accretion discs around black holes.
The first part aims to give an introduction to the fundamental topics of the thesis: black holes, accretion discs and Lense-Thirring precession.
The second is dedicated to tidal disruption event accretion discs formed around supermassive black holes. This contains an introduction to Tidal Disruption Events (TDEs) and a Chapter based on my first paper about LT precession of TDE accretion discs.
The third part contains an introduction on the modelling of accretion discs in low mass X-ray binaries (LMXBs) around stellar mass black holes and two Chapters based on two papers I have co-authored that aim to constrain the black hole spin in LMXBs through the detection of type-C Quasi-Periodic Oscillations (QPOs) in the power density spectra of these sources.
In the last Chapter I draw the conclusion and future perspectives of the work done in the thesis. The Appendix contains a detailed calculation of the spherical innermost stable orbit around a black hole and a general introduction to Smoothed Particle Hydrodynamic (SPH) simulations
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
Lense–Thirring precession around supermassive black holes during tidal disruption events
Full text linkA tidal disruption event occurs when a star wanders close enough to a black hole to be disrupted by its tidal force. The debris of a tidally disrupted star are expected to form an accretion disc around the supermassive black hole. The light curves of these events sometimes show a quasi-periodic modulation of the flux that can be associated with the precession of the accretion disc due to the Lense-Thirring (`frame-dragging') effect. Since the initial star orbit is in general inclined with respect to the black hole spin, this misalignment combined with the Lense-Thirring effect leads to a warp in the disc. In this paper, we provide a simple model of the system composed by a thick and narrow accretion disc surrounding a spinning supermassive black hole, with the aim to: (a) compute the expected precession period as a function of the system parameters, (b) discuss the conditions that have to be satisfied in order to have rigid precession, (c) investigate the alignment process, highlighting how different mechanisms play a role leading the disc and the black hole angular momenta into alignment
Constraining black hole spins with low-frequency quasi-periodic oscillations in soft states
Full text linkBlack hole X-ray transients show a variety of state transitions during their outburst phases, characterized by changes in their spectral and timing properties. In particular, power density spectra (PDS) show quasi periodic oscillations (QPOs) that can be related to the ac- cretion regime of the source. We looked for type-C QPOs in the disc-dominated state (i.e. the high soft state) and in the ultra-luminous state in the RXTE archival data of 12 transient black hole X-ray binaries known to show QPOs during their outbursts. We detected 6 significant QPOs in the soft state that can be classified as type-C QPOs. Under the assumption that the accretion disc in disc-dominated states extends down or close to the innermost stable circular orbit (ISCO) and that type-C QPOs would arise at the inner edge of the accretion flow, we use the relativistic precession model (RPM) to place constraints on the black hole spin. We were able to place lower limits on the spin value for all the 12 sources of our sample while we could place also an upper limit on the spin for 5 sources
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