1,721,869 research outputs found
Sistemi X-Ray-EUV laser plasma: messa a punto caratterizzazione e applicazioni per lo studio in vivo di campioni biologici
Full text linkThe work presented in this thesis was mainly developed at the Quantum Electronics and Plasma Laboratory (QEPL) of the University of Rome Tor Vergata. Since manu years at QEPL an activity devoted to the development of power laser systems was started to product Soft X rays via the interaction between solid target and laser radiation. In this work I shall present the above mentioned apparatus, together with its improvement and characterization to reach the goal of producing radiation within Extreme Ultraviolet (EUV) region, thanks to the use of a supersonic gas jet target of Xenon. At the same time I shall illustrate a new technique to record images of biological samples, based on an innovative detector device: the LiF crystals. The utilization of these devices, together with th radiation delivered by our laser plasma source, allow relevant appplications in microscopy analysis since they permit to obtain images of flash of life of the tested biological sample.
The subsequent study of the images revealed that LiF crystals exhibit a high intrinsic resolution, with a dynamical response much higher than that reached with PMMA films. Unfortunately there is still an open problem: the spatial resolution obtainable by the optical apparatus which reads the LiF sample. Up to now the best values are of the order of 500nm.
I shall futhermore show the experimental results obtained by means of a CCD camera with which microradiographies of dewatered biological samples treated by heavy metals were acquired. In this case different absorption of X rays radiation have been measured, to perform studies of bioaccumulation.
Finally, the end of this thesis will be devoted to the description of the state of the art of another laser system based on a femtosecond Ti:Sa oscillator. I shall describe the performances of the first amplifier and compressor, which was installed. This apparatus will be utilized to inject an ultra short pulse into an Excimer KrFl laser, last amplification stage of the whole chain, to produce ultra short pulse trains in the UV region
Optical measures of dust velocities and direction during loss of vacuum accidents in confined environment and correlation between dust positions and properties with the resuspension degrees and the velocity modules
Full text linkDust explosions are dangerous events that still today represent a risk to all the
industries that produce and/or handle combustible dust like the ag
roalimentary,
pharmaceutical and energy ones. When a dust cloud is dispersed in an oxidant gas, like air, it
may reach the explosive concentration range. A model to predict the dust critical conditions,
that can cause explosions, is a key factor for safet
y of operators and the security of the plants.
The key point to predict this dust resuspension is to measure the velocity vectors of dust under
the accidental conditions. In order to achieve this goal the authors have developed an
experimental facility, ST
ARDUST
-
U, which allow to obtain different conditions of
temperature and pressurization rates characteristic of accidents in confined environment. The
authors have developed also optical methods and software to analyse different dust
resuspension phenomena
under different conditions in confined environment. In this paper, the
author will present how they measure the dust velocity vectors in different experimental
conditions (and for different type of dusts) and how they have related the dust characteristics
and positions inside STARDUST
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U with the resuspension degree and the velocity values
On the potential of time delay neural networks to detect indirect coupling between time series
Full text linkDetermining the coupling between systems remains a topic of active research in the field of complex science. Identifying the proper causal influences in time series can already be very challenging in the trivariate case, particularly when the interactions are non-linear. In this paper, the coupling between three Lorenz systems is investigated with the help of specifically designed artificial neural networks, called time delay neural networks (TDNNs). TDNNs can learn from their previous inputs and are therefore well suited to extract the causal relationship between time series. The performances of the TDNNs tested have always been very positive, showing an excellent capability to identify the correct causal relationships in absence of significant noise. The first tests on the time localization of the mutual influences and the effects of Gaussian noise have also provided very encouraging results. Even if further assessments are necessary, the networks of the proposed architecture have the potential to be a good complement to the other techniques available in the market for the investigation of mutual influences between time serie
Enclaves provide new insights on the dynamics of manga mingling: a case study from Salina Island (Southern Thyrrenian Sea, Italy).
No full textA low-resolution inversion-based method to enhance poloidal polarimeter accuracy in thermonuclear plasmas
No full textThe use of polarimeter in nuclear fusion is increasing so much that ITER will mount three polarimeters for plasma control and diagnostics, while the Divertor Tokamak Test will have a poloidal polarimeter with more than ten lines of sight. Several studies have been conducted on this diagnostic, where the main experimental test bench was the FIR interferometer-polarimeter at Joint European Torus. Polarimetry measurements can be used for different purposes, such as real-time control of the plasma, machine protection, and plasma equilibrium constraint. However, even if the rate of change of the polarisation is strongly related to plasma characteristics, the exact equations that link the plasma quantities (electron density and magnetic field) with the beam polarisation are not linear. Thus, extrapolation of the plasma quantities requires an inversion that is not possible a priori since it would need the knowledge of the measuring quantities. For these reasons, polarimeters should be designed to work under the so-called type-I approximation, which ensures linearity between the line-integrated plasma properties and the polarisation state of the electromagnetic wave. However, the range of validity of the type-I approximation, chosen the laser wavelength, is limited to a specific range of plasma quantities. In this work, the authors proposed a new approach to calculate those line-integrated quantities for poloidal polarimeters. The new approach is developed for two situations, back-reflected and not back-reflected beams. The two proposed methods will be introduced analytically and tested numerically, showing that they can provide more accurate measurements for a wider range of plasma operations
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
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