1,561 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
Differentiated Instruction for All Students in English Language Arts
Teachers are challenged to meet the needs of every student in their classroom and deliver instruction that gives students the opportunity to learn at their highest potential. In any given classroom, there are “at risk students,” “grade level students,” and “accelerated students” that need to have their specific learning needs met. Specifically in English Language Arts, teachers have a wide spectrum of abilities they need to accommodate for. All three levels of learners should be pushed to their fullest potential and challenged equally. By administering a survey to several schools in a suburban Rochester, New York community – data was collected to see if teachers believe all students in their classrooms are being sufficiently challenged, and if so, how are the teachers accommodating for all levels of learners in ELA. Data collection occurred over several weeks in the spring. The information gathered can help all levels of students be adequately challenged, and also provide resources and techniques to further the professional development of current and future teachers
The new sample of Giant radio sources: I. Radio imaging, optical identification and spectroscopy of selected candidates
A new sample of very large angular size radio sources has been selected from the 1.4 GHz VLA surveys: FIRST and NVSS. This sample will be very useful for an observational constraint on the time evolution of double radio sources, especially their size, predicted by numerous analytical models of such evolution (cf. Introduction). In this paper we present radio and optical data for a large fraction of the sample sources. They are: high-frequency VLA maps with very weak radio cores detected, deep optical images showing the identified faint host galaxies not visible on the DSS images, and optical spectra of the identified galaxies brighter than about R ~ 18.5 mag taken with the McDonald Observatory 2.1m telescope. For 15 galaxies (of which 4 do not belong to the complete sample) the redshift has been determined. In the result, 44 per cent of galaxies in the complete sample have redshift data (with one exception all redshifts are less than 0.33), of which 70 per cent have a linear size exceeding 1 Mpc. The photometric redshift estimates for other 11 galaxies with 19 mag<R<21.7 mag (0.3<z<0.5) predict their sizes much over 1 Mpc
Nanometric pitch in modulated structures of twist-bend nematic liquid crystals
The extended Frank elastic energy density is used to investigate the
existence of a stable periodically modulate structure that appears as a ground
state exhibiting a twist-bend molecular arrangement. For an unbounded sample,
we show that the twist-bend nematic phase is characterized by a
heliconical structure with a pitch in the nano-metric range, in agreement with
experimental results. For a sample of finite thickness, we show that the wave
vector of the stable periodic structure depends not only on the elastic
parameters but also on the anchoring energy, easy axis direction, and the
thickness of the sample.Comment: 11 page
Detection of the Vortex Dynamic Regimes in MgB2 by Third Harmonic AC Susceptibility Measurements
In a type-II superconductor the generation of higher harmonics in the
magnetic response to an alternating magnetic field is a consequence of the
non-linearity in the I-V relationship. The shape of the current-voltage (I-V)
curve is determined by the current dependence of the thermal activation energy
U(J) and is thus related to the dynamical regimes governing the vortex motion.
In order to investigate the vortex dynamics in MgB2 bulk superconductors we
have studied the fundamental (chi1) and third (chi3) harmonics of the ac
magnetic susceptibility. Measurements have been performed as a function of the
temperature and the dc magnetic field, up to 9 T, for various frequencies and
amplitudes of the ac field. We show that the analysis of the behaviour in
frequency of chi3(T) and chi3(B) curves can provide clear information about the
non-linearity in different regions of the I-V characteristic. By comparing the
experimental curves with numerical simulations of the non-linear diffusion
equation for the magnetic field we are able to resolve the crossover between a
dissipative regime governed by flux creep and one dominated by flux flow
phenomena.Comment: to be published in "Horizons in Superconductivity Research" (Nova
Science Publishers, Inc., NY, 2003
Photometric, Spectroscopic and Orbital Period Study of Three Early Type Semi-detached Systems: XZ Aql, UX Her and AT Peg
In this paper we present a combined photometric, spectroscopic and orbital
period study of three early-type eclipsing binary systems: XZ Aql, UX Her, and
AT Peg. As a result, we have derived the absolute parameters of their
components and, on that basis, we discuss their evolutionary states.
Furthermore, we compare their parameters with those of other binary systems and
with the theoretical models. An analysis of all available up-to-date times of
minima indicated that all three systems studied here show cyclic orbital
changes, their origin is discussed in detail. Finally, we performed a frequency
analysis for possible pulsational behavior and as a result we suggest that XZ
Aql hosts a {\delta} Scuti component.Comment: 40 pages, 16 figure
Two-year outcome of an observe-and-plan regimen for neovascular age-related macular degeneration treated with Aflibercept.
The purpose of our study was to investigate the two-year outcome of Aflibercept treatment for neovascular age-related macular degeneration (nAMD), using the Observe-and-Plan regimen, an individually planned treatment regimen, based on the predictability of an individual's need for retreatment, aiming to reduce the clinical burden.
Our prospective study used the Observe-and-Plan regimen with Aflibercept to treat nAMD: Three loading doses, followed by monthly observation visits until the disease-recurrence interval was determined, which then was shortened by 2 weeks in a treatment plan for the next three injections without intermediate monitoring visits. The subsequent treatment plans were adjusted according to periodically assessed disease activity. The primary outcome measures were visual acuity changes, number of injections, and number of monitoring visits.
The study included 112 eyes of 102 patients with a mean age of 80.7 years (SD 7.6). Mean visual acuity (VA) improved from 61.8 ETDRS letters (20/60(+2)) at baseline, by 8.5, 8.0, and 6.2 letters at months 3, 12 and 24, respectively. Mean central retinal thickness was 438um at baseline, and reduced by 152um, 155um, and 150um at months 3, 12 and 24, respectively. The mean number of injections was 8.7 and 6.5 in the first and second year, respectively. The mean number of monitoring visits after baseline was 3.8 and 2.8 during the first and second year, respectively.
The Observe-and-Plan regimen significantly improved VA, while fewer monitoring visits were needed as compared to other variable dosing regimens, thus reducing the workload for chronic care management of nAMD
Signal Processing Methodology of Response Data from a Historical Arch Bridge toward Reliable Modal Identification
The paper is part of a case study concerning the structural assessment of a historical infrastructure in the local territory, a road three-span reinforced concrete arch bridge over a river, built by the end of World War I (1917). The purpose of the paper is twofold: first, in-situ acquired response data are systematically analysed by specific signal processing techniques, to form a devoted methodological procedure and to extract useful information toward possible interpretation of the current structural conditions; second, the deciphered information is elaborated, in view of obtaining peculiar conceptualisations of detailed features of the structural response, as meant to achieve quantitative descriptions and modelling, for final Structural Health Monitoring (SHM) and intervention purposes. The proposed methodology, integrating self-implemented and adapted classical signal processing methods, and refined techniques, such as Wavelet analysis and ARMA models, assembles a rather general, systematic methodological approach to signal processing, highlighting the capability to extract useful and fundamental information from acquired response data, also endowed of a non-stationary character, toward final structural interpretation, identification and modelling, thus enabling for developing a reliable and effective SHM platform, on strategic ageing infrastructures. For the present case study, non-stationary characteristics of the response signals are revealed and flattened out, to identify the underlying fundamental frequencies of the infrastructure and to advance particular interpretations of its current structural behaviour, in forming an enlarging structural consciousness of the bridge at hand
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