1,184 research outputs found
Fundamental and harmonic emission in interplanetary type 2 radio bursts
Three interplanetary type II radio bursts which show two prominent and long duration bands in their dynamic spectra were analyzed in detail and compared to similar bands in meter wavelength type II events. These bands, which differ by a factor of about two in frequency, were interpreted in terms of fundamental and harmonic emission. The fundamental component has a greater average intensity than the harmonic, due largely to short intense brightenings. The fundamental spectral profile is more narrow than that of the harmonic, with harmonic band typically exhibiting a larger bandwidth to frequency ratio than the fundamental by a factor of two. The fundamental has a larger source size than the harmonic, 160 degrees versus 110 degrees, on average, as viewed from the Sun. Two of the events have source positions which correlate well with the associated flare positions
Turing Instability in a Boundary-fed System
The formation of localized structures in the chlorine dioxide-idodine-malonic
acid (CDIMA) reaction-diffusion system is investigated numerically using a
realistic model of this system. We analyze the one-dimensional patterns formed
along the gradients imposed by boundary feeds, and study their linear stability
to symmetry-breaking perturbations (Turing instability) in the plane transverse
to these gradients. We establish that an often-invoked simple local linear
analysis which neglects longitudinal diffusion is inappropriate for predicting
the linear stability of these patterns. Using a fully nonuniform analysis, we
investigate the structure of the patterns formed along the gradients and their
stability to transverse Turing pattern formation as a function of the values of
two control parameters: the malonic acid feed concentration and the size of the
reactor in the dimension along the gradients. The results from this
investigation are compared with existing experiments.Comment: 41 pages, 18 figures, to be published in Physical Review
A Population-Based Ultra-Widefield Digital Image Grading Study for Age-Related Macular Degeneration-Like Lesions at the Peripheral Retina.
Our understanding of the relevance of peripheral retinal abnormalities to disease in general and in age-related macular degeneration (AMD) in particular is limited by the lack of detailed peripheral imaging studies. The purpose of this study was to develop image grading protocols suited to ultra-widefield imaging (UWFI) in an aged population
Analytic Criteria for Power Exhaust in Divertors due to Impurity Radiation
Present divertor concepts for next step experiments such ITER and TPX rely
upon impurity and hydrogen radiation to transfer the energy from the edge
plasma to the main chamber and divertor chamber walls. The efficiency of these
processes depends strongly on the heat flux, the impurity species, and the
connection length. Using a database for impurity radiation rates constructed
from the ADPAK code package, we have developed criteria for the required
impurity fraction, impurity species, connection length and electron temperature
and density at the mid-plane. Consistent with previous work, we find that the
impurity radiation from coronal equilibrium rates is, in general, not adequate
to exhaust the highest expected heating powers in present and future
experiments. As suggested by others, we examine the effects of enhancing the
radiation rates with charge exchange recombination and impurity recycling, and
develop criteria for the minimum neutral fraction and impurity recycling rate
that is required to exhaust a specified power. We also use this criteria to
find the optimum impurity for divertor power exhaust.Comment: Preprint for the 11th PSI meeting, Adobe pdf with 14 figures, 15
page
Radiation Rates for Low Z Impurities in Edge Plasmas
The role of impurity radiation in the reduction of heat loads on divertor
plates in present experiments such as DIII-D, JET, JT-60, ASDEX, and Alcator
C-Mod, and in planned experiments such as ITER and TPX places a new degree of
importance on the accuracy of impurity radiation emission rates for electron
temperatures below 250 eV for ITER and below 150 eV for present experiments. We
have calculated the radiated power loss using a collisional radiative model for
Be, B, C, Ne and Ar using a multiple configuration interaction model which
includes density dependent effects, as well as a very detailed treatment of the
energy levels and meta-stable levels. The "collisional radiative" effects are
very important for Be at temperatures below 10 eV. The same effects are present
for higher Z impurities, but not as strongly. For some of the lower Z elements,
the new rates are about a factor of two lower than those from a widely used,
simpler average-ion package (ADPAK) developed for high Z ions and for higher
temperatures. Following the approach of Lengyel for the case where electron
heat conduction is the dominant mechanism for heat transport along field lines,
our analysis indicates that significant enhancements of the radiation losses
above collisional radiative model rates due to such effects as rapid recycling
and charge exchange recombination will be necessary for impurity radiation to
reduce the peak heat loads on divertor plates for high heat flux experiments
such as ITER.Comment: Preprint for the 11th PSI meeting, gzipped postscript with 11
figures, 14 page
New records and present status of the invasive Spotted Wing Drosophila, Drosophila suzukii (Matsumura, 1931) (Diptera) in Hungary
The spotted wing drosophila (Drosophila suzukii (Matsumura, 1931) – SWD) is one of the most recently introduced invasive pests of economical importance in Europe. It has invaded many countries in Europe and North America causing significant losses in fruit production. In 2012, the species has been detected for the first time in Hungary at a highway rest area. The following year a countrywide trapping program was conducted to monitor the spreading of the species. In 2013, thirty-three highway rest areas and furthermore cherry, strawberries, raspberries, peach, grape orchards were monitored using apple vinegar bait traps. Altogether 33 individuals of SWD have been captured in 5 localities along highways in western Hungary, including the collecting site of the first detection. On the other hand the species was not found in countryside orchards. The location of the collecting sites indicates that international transport along highways plays an important role in spreading of SWD. Highway infrastructures, like selective trash bins, or buildings may serve as refugee spots for SWD. The role of vehicle transport in the spreading of SWD is also supported by the relatively high spreading rate of SWD, which was estimated around 320–390 km year-1
Center or Limit Cycle: Renormalization Group as a Probe
Based on our studies done on two-dimensional autonomous systems, forced
non-autonomous systems and time-delayed systems, we propose a unified
methodology - that uses renormalization group theory - for finding out
existence of periodic solutions in a plethora of nonlinear dynamical systems
appearing across disciplines. The technique will be shown to have a non-trivial
ability of classifying the solutions into limit cycles and periodic orbits
surrounding a center. Moreover, the methodology has a definite advantage over
linear stability analysis in analyzing centers
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The Dynamical Regime of Sensory Cortex: Stable Dynamics around a Single Stimulus-Tuned Attractor Account for Patterns of Noise Variability.
Correlated variability in cortical activity is ubiquitously quenched following stimulus onset, in a stimulus-dependent manner. These modulations have been attributed to circuit dynamics involving either multiple stable states ("attractors") or chaotic activity. Here we show that a qualitatively different dynamical regime, involving fluctuations about a single, stimulus-driven attractor in a loosely balanced excitatory-inhibitory network (the stochastic "stabilized supralinear network"), best explains these modulations. Given the supralinear input/output functions of cortical neurons, increased stimulus drive strengthens effective network connectivity. This shifts the balance from interactions that amplify variability to suppressive inhibitory feedback, quenching correlated variability around more strongly driven steady states. Comparing to previously published and original data analyses, we show that this mechanism, unlike previous proposals, uniquely accounts for the spatial patterns and fast temporal dynamics of variability suppression. Specifying the cortical operating regime is key to understanding the computations underlying perception
Developing a method for obtaining pupil insight for Building in Use reviews
This report details exploratory research undertaken by Newcastle University from November 2022 to May 2023. The aim of this exploratory project was to develop, trial and evaluate approaches to providing indications of how outdoor space is being perceived, used and valued by students in four schools – to ascertain which approach (or approaches) may be best suited for use as part of Building in Use (BiU) reviews.The report details the three digital methods tested, as well as the enablers and barriers encountered while using them.The digital tools developed can be used individually to obtain limited data, but a combination of several methods is most and can be combined with information from the BiU site visit and staff survey in providing an overall BiU assessment. However, there are barriers to this including financial outlay, support from schools, and the time and effort required to create the data collection tools, even with the templates and prototypes that we detail in the report.We recommend initial discussions between the BiU technical adviser (TA) and school about tools, so that these can be chosen to fit with school procedures, especially relating to online access, and also fulfil particular needs of a specific BiU review. This would form part of a developed relationship between TA and school, beyond the existing one of schools accommodating data collection using pre-specified methods, which would also include feedback from the TA to the school
Spin Effects in Two Quark System and Mixed States
Based on the numeric solution of a system of coupled channels for vector
mesons (- and -waves mixing) and for tensor mesons (- and -waves
mixing) mass spectrum and wave functions of a family of vector mesons
in triplet states are obtained. The calculations are performed using
a well known Cornell potential with a mixed Lorentz-structure of the
confinement term. The spin-dependent part of the potential is taken from the
Breit-Fermi approach. The effect of singular terms of potential is considered
in the framework of the perturbation theory and by a configuration interaction
approach (CIA), modified for a system of coupled equations. It is shown that
even a small contribution of the -wave to be very important at the
calculation of certain characteristics of the meson states.Comment: 12 pages, LaTe
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