1,721,022 research outputs found
Effects of atomic interactions on the resonant tunnelling of sodium condensates
No full textWe investigate the influence of atomic interactions on the tunnelling of sodium condensates across a spatially oscillating optical barrier. In the limit of very fast barrier oscillations, in which resonant tunnelling via a metastable state takes place, the interactions affect the position and lineshape of the transmission peak. We anticipate that the possibility of modulating the interactions in a tunnelling condensate can be exploited to achieve nonlinear effects such as optical limiting and bistability
Vertical transport through laterally periodically modulated heterostructures
No full textThe ballistic transport in a laterally periodically modulated heterojunction connecting two reservoirs is studied: this can model the presence of an ordered layer of self-organized quantum dots. The problem is solved in the envelope function formalism using a three-dimensional (3D) generalization of the transfer matrix approach that exploits the two-dimensional (2D) lattice periodicity. Illustrative numerical results are presented showing qualitatively different behaviors of the transmission coefficients due to the multichannel nature of the propagation, In particular, deep minima of the transmission occur due to destructive interference between different conducting channels, a situation that cannot be realized in the absence of the lateral modulation. (C) 2001 Elsevier Science Ltd. All rights reserved
Effects of atomic interactions on the resonant tunnelling of sodium condensates
No full textWe investigate the influence of atomic interactions on the tunnelling of sodium condensates across a spatially oscillating optical barrier. In the limit of very fast barrier oscillations, in which resonant tunnelling via a metastable state takes place, the interactions affect the position and lineshape of the transmission peak. We anticipate that the possibility of modulating the interactions in a tunnelling condensate can be exploited to achieve nonlinear effects such as optical limiting and bistability
Microgravity vertical gradient measurement in the site of VIRGO interferometric antenna (Pisa plain, Italy)
No full textThe site of the European Gravitational Observatory (EGO) located in the countryside near Pisa (Tuscany, Italy) was investigated by a microgravity vertical gradient (MVG) Survey. The EGO site houses the VIRGO interferometric antenna for gravitational waves detection. The microgravity survey aims to highlight the gravity anomalies of high-frequency related to more superficial geological sources to obtain a detailed model of the lithologic setting of the VIRGO site, this will allow an estimate of the noise induced by seismic waves and by Newtonian interference. This paper presents the results of the gradiometric survey of 2006 in the area of the interferometric antenna. MVG measurements allow its to enhance the high frequency signal strongly associated with the shallow structures. The gradient gravity map shows a main negative pattern that seems related to the trending of the high density layer of gravel revealed in geotechnical drillings executed along the orthogonal arms during the construction of the VIRGO complex. Calibrating the relationship between the vertical gradient and the depth of the gravel interface we have computed a model of gravity gradient for the whole VIRGO site, defining the 3D distribution of the top surface of this layer. The latter shows a NE-SW negative pattern that may represent a palaeobed alluvial of the Serchio from the Bientina River system
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
Environmental magneto-gradiometric marine survey in a highly anthropic noisy area
No full textWe describe a magneto-gradiometric survey performed in the «Mar Piccolo» of Taranto, Italy in May 2005 for environmental purposes. This region, which is a noisy harbour environment, provides a challenging test for magnetic methods. To reduce spurious noise signals, with both temporal and spatial origins, we used two Geometrics G880 model caesium magnetometers towed in a transverse gradient configuration. We show how, in shallow waters, this gradiometric configuration allows us to distinguish anomalies due to small metallic bodies near the seabed from the induced noise due to the anthropic contribution and geomagnetic field variations. A direct visual inspection confirmed that the peculiarities highlighted in the gradient anomaly map were due to abandoned metallic objects found on the seabed
Microgravity vertical gradient measurement in the site of VIRGO interferometric antenna (Pisa plain, Italy)
No full textThe site of the European Gravitational Observatory (EGO) located in the countryside near Pisa (Tuscany, Italy) was investigated by a microgravity vertical gradient (MVG) survey. The EGO site houses the VIRGO interferometric antenna for gravitational waves detection. The microgravity survey aims to highlight the gravity anomalies of high-frequency related to more superficial geological sources to obtain a detailed model of the lithologic setting of the VIRGO site, this will allow an estimate of the noise induced by seismic waves and by Newtonian interference. This paper presents the results of the gradiometric survey of 2006 in the area of the interferometric antenna. MVG measurements allow us to enhance the high frequency signal strongly associated with the shallow structures. The gradient gravity map shows a main negative pattern that seems related to the trending of the high density layer of gravel revealed in geotechnical drillings executed along the orthogonal arms during the construction of the VIRGO complex. Calibrating the relationship between the vertical gradient and the depth of the gravel interface we have computed a model of gravity gradient for the whole VIRGO site, defining the 3D distribution of the top surface of this layer. The latter shows a NE-SW negative pattern that may represent a palaeobed alluvial of the Serchio from the Bientina River system
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
- …
