8,005 research outputs found
Magnetic relaxation of type II superconductors in a mixed state of entrapped and shielded flux
The magnetic relaxation has been investigated in type II superconductors when
the initial magnetic state is realized with entrapped and shielded flux (ESF)
contemporarily. This flux state is produced by an inversion in the magnetic
field ramp rate due to for example a magnetic field overshoot. The
investigation has been faced both numerically and by measuring the magnetic
relaxation in BSCCO tapes. Numerical computations have been performed in the
case of an infinite thick strip and of an infinite slab, showing a quickly
relaxing magnetization in the first seconds. As verified experimentally, the
effects of the overshoot cannot be neglected simply by cutting the first 10-100
seconds in the magnetic relaxation. On the other hand, at very long times, the
magnetic states relax toward those corresponding to field profiles with only
shielded flux or only entrapped flux, depending on the amplitude of the field
change with respect to the full penetration field of the considered
superconducting samples. In addition, we have performed numerical simulations
in order to reproduce the relaxation curves measured on the BSCCO(2223) tapes;
this allowed us to interpret correctly also the first seconds of the
curves.Comment: 9 pages, 12 figures submit to PR
Harmonics of the AC susceptibility as probes to differentiate the various creep models
We measured the temperature dependence of the 1st and the 3rd harmonics of
the AC magnetic susceptibility on some type II superconducting samples at
different AC field amplitudes, hAC. In order to interpret the measurements, we
computed the harmonics of the AC susceptibility as function of the temperature
T, by integrating the non-linear diffusion equation for the magnetic field with
different creep models, namely the vortex glass-collective creep
(single-vortex, small bundle and large bundle) and Kim-Anderson model. We also
computed them by using a non-linear phenomenological I-V characteristics,
including a power law dependence of the pinning potential on hAC. Our
experimental results were compared with the numerically computed ones, by the
analysis of the Cole-Cole plots. This method results more sensitive than the
separate component analysis, giving the possibility to obtain detailed
information about the contribution of the flux dynamic regimes in the magnetic
response of the analysed samples.Comment: 9 pages, 6 figures, submitted to Physica
Binge-Eating Symptoms, emotional-behavioral problems and gender differences among adolescents: A brief report
We investigated relationships between binge-eating symptoms and emotional-behavioral problems in 382 community-adolescents (aged 13-18 years, M = 15, SD = 1; 61% girls), analyzing gender differences. Few studies have investigated binge eating in community-adolescents and none have explored gender differences in Italy. Participants completed the Binge Eating Scale (BES) and the Youth Self Report (YSR 11/18), which measures internalizing, externalizing and other problems (e.g. binge-drinking, substance abuse). 6% of adolescents (99% girls) were at-risk of binge-eating symptoms. In both gender, binge-eating symptoms were correlated with internalizing and other problems (all p < .001), but unexpectedly they were correlated with externalizing problems only in girls. The set of internalizing, externalizing and other problems predicted 23% of variance in BES among girls; only other problems predicted 12% of variance in BES among boys. Results identified gender-specific and non-specific risk factors for binge eating in Italian community-adolescents, that should be further investigated
Attachment and alexithymia predict emotional–behavioural problems of institutionalized, late-adopted and community adolescents: An explorative multi-informant mixed-method study
Objective: Compared to community adolescents (COM), adolescents placed in residential care (RC) or late adopted (LA) appear to show more emotional–behavioural problems. They also appear vulnerable in variables linked to emotional–behavioural problems, such as insecure–disorganized attachment and alexithymia. This study employs a mixed-method multi-informant approach to (1) compare adolescents placed in RC, LA and COM in emotional–behavioural problems, attachment and alexithymia and (2) investigate relationships and interplay of attachment and alexithymia concerning emotional–behavioural problems in these three groups. Method: Participants were 174 adolescents (50 RC, 33 LA and 91 COM; Mage = 15, 53% boys and 47% girls). Adolescents' internalizing and externalizing problems were assessed through both caregiver-reported and self-reported questionnaires, while attachment and alexithymia were assessed with a mixed method, using interviews and self-report questionnaires. Results: The results showed RC adolescents as more vulnerable in all variables, while LA and COM did not differ. Accounting for the group, attachment and alexithymia cumulatively predicted 25–43% of internalizing problems, and 19–43% of externalizing problems depending on the method of assessment or problems' informant (all p < 0.01). Alexithymia was both an independent predictor and interacted with preoccupied attachment in predicting internalizing problems, while no predictors were isolated for externalizing ones, and the group never indicate an effect on problems' rates. Conclusions: The authors discuss the utility to maintain a research focus on attachment and alexithymia, also suggesting future directions of research. A need to determine potential distortions of results because of problems' informant and method of assessment is also highlighted
Adaptive statistical pattern classifiers for remotely sensed data
A technique for the adaptive estimation of nonstationary statistics necessary for Bayesian classification is developed. The basic approach to the adaptive estimation procedure consists of two steps: (1) an optimal stochastic approximation of the parameters of interest and (2) a projection of the parameters in time or position. A divergence criterion is developed to monitor algorithm performance. Comparative results of adaptive and nonadaptive classifier tests are presented for simulated four dimensional spectral scan data
Timelike and spacelike hadron form factors, Fock state components and light-front dynamics
A unified description of spacelike and timelike hadron form factors within a
light-front model was successfully applied to the pion. The model is extended
to the nucleon to study the role of pair production and of
nonvalence components in the nucleon form factors. Preliminary results in the
spacelike range are presented.Comment: 4 pages, espcrc1.sty. proceedings of FB XVIII (August 2006, Brazil),
to be published in Nucl. Phys.
Electromagnetic Hadron Form Factors and Higher Fock Components
Investigation of the spacelike and timelike electromagnetic form factors of
hadrons, within a relativistic microscopical model characterized by a small set
of hypothesis, could shed light on the components of hadron states beyond the
valence one. Our relativistic approach has been successfully applied first to
the pion and then the extension to the nucleon has been undertaken. The pion
case is shortly reviewed as an illustrative example for introducing the main
ingredients of our approach, and preliminary results for the nucleon in the
spacelike range are evaluated.Comment: 8 pages, 6 figs, espcrc1.sty included. Proceedings of Fifth
International Conference on Perspectives In Hadronic Physics, ICTP, May
22-26, 200
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