143 research outputs found
Scintillation Caustics in Planetary Occultation Light Curves
We revisit the GSC5249-01240 light curve obtained during its occultation by
Saturn's North polar region. In addition to refractive scintillations, the
power spectrum of intensity fluctuations shows an enhancement of power between
refractive and diffractive regimes. We identify this excess power as due to
high amplitude spikes in the light curve and suggest that these spikes are due
to caustics associated with ray crossing situations. The flux variation in
individual spikes follows the expected caustic behavior, including diffraction
fringes which we have observed for the first time in a planetary occultation
light curve. The presence of caustics in scintillation light curves require an
inner scale cut off to the power spectrum of underlying density fluctuations
associated with turbulence. Another possibility is the presence of gravity
waves in the atmosphere. While occultation light curves previously showed the
existence of refractive scintillations, a combination of small projected
stellar size and a low relative velocity during the event have allowed us to
identify caustics in this occultation. This has led us to re-examine previous
data sets, in which we have also found likely examples of caustics.Comment: 4 pages, 3 figures; ApJL submitte
Multivariate regression methods for estimating velocity of ictal discharges from human microelectrode recordings
Objective. Epileptiform discharges, an electrophysiological hallmark of seizures, can propagate across cortical tissue in a manner similar to traveling waves. Recent work has focused attention on the origination and propagation patterns of these discharges, yielding important clues to their source location and mechanism of travel. However, systematic studies of methods for measuring propagation are lacking. Approach. We analyzed epileptiform discharges in microelectrode array recordings of human seizures. The array records multiunit activity and local field potentials at 400-micron spatial resolution, from a small cortical site free of obstructions. We evaluated several computationally efficient statistical methods for calculating traveling wave velocity, benchmarking them to analyses of associated neuronal burst firing. Main results. Over 90% of discharges met statistical criteria for propagation across the sampled cortical territory. Detection rate, direction and speed estimates derived from a multiunit estimator were compared to four field potential-based estimators: negative peak, maximum descent, high gamma power, and cross-correlation. Interestingly, the methods that were computationally simplest and most efficient (negative peak and maximal descent) offer non-inferior results in predicting neuronal traveling wave velocities compared to the other two, more complex methods. Moreover, the negative peak and maximal descent methods proved to be more robust against reduced spatial sampling challenges. Using least absolute deviation in place of least squares error minimized the impact of outliers, and reduced the discrepancies between local field potential-based and multiunit estimators. Significance. Our findings suggest that ictal epileptiform discharges typically take the form of exceptionally strong, rapidly traveling waves, with propagation detectable across millimeter distances. The sequential activation of neurons in space can be inferred from clinically-observable EEG data, with a variety of straightforward computation methods available. This opens possibilities for systematic assessments of ictal discharge propagation in clinical and research settings
Effectiveness of the Strengthening Families Programme 10–14 in Poland for the prevention of alcohol and drug misuse: protocol for a randomized controlled trial
<p>Abstract</p> <p>Background</p> <p>Alcohol and other drug use and misuse is a significant problem amongst Polish youth. The SFP10-14 is a family-based prevention intervention that has positive results in US trials, but questions remain about the generalizability of these results to other countries and settings.</p> <p>Methods/Design</p> <p>A cluster randomized controlled trial in community settings across Poland. Communities will be randomized to a SFP10-14 trial arm or to a control arm. Recruitment and consent of families, and delivery of the SFP10-14, will be undertaken by community workers. The primary outcomes are alcohol and other drug use and misuse. Secondary (or intermediate) outcomes include parenting practices, parent–child relations, and child problem behaviour. Interview-based questionnaires will be administered at baseline, 12 and 24 months.</p> <p>Discussion</p> <p>The trial will provide information about the effectiveness of the SFP10-14 in Poland.</p> <p>Trial registration</p> <p>International Standard Randomised Controlled Trial Number: ISRCTN89673828</p
The ictal wavefront is the spatiotemporal source of discharges during spontaneous human seizures
The extensive distribution and simultaneous termination of seizures across cortical areas has led to the hypothesis that seizures are caused by large-scale coordinated networks spanning these areas. This view, however, is difficult to reconcile with most proposed mechanisms of seizure spread and termination, which operate on a cellular scale. We hypothesize that seizures evolve into self-organized structures wherein a small seizing territory projects high-intensity electrical signals over a broad cortical area. Here we investigate human seizures on both small and large electrophysiological scales. We show that the migrating edge of the seizing territory is the source of travelling waves of synaptic activity into adjacent cortical areas. As the seizure progresses, slow dynamics in induced activity from these waves indicate a weakening and eventual failure of their source. These observations support a parsimonious theory for how large-scale evolution and termination of seizures are driven from a small, migrating cortical area
Circumstantial Evidence for a Critical Behavior in Peripheral Au + Au Collisions at 35 MeV/nucleon
The fragmentation resulting from peripheral Au + Au collisions at an incident
energy of E = 35 MeV/nucleon is investigated. A power-law charge distribution,
with , and an intermittency signal are observed
for events selected in the region of the Campi scatter plot where "critical"
behavior is expected.Comment: 11 pages, RevTex file, 4 postscript figures available upon request
from [email protected]
Additional Nucleon Current Contributions to Neutrinoless Double Beta Decay
We have examined the importance of momentum dependent induced nucleon
currents such as weak-magnetism and pseudoscalar couplings to the amplitude of
neutrinoless double beta decay in the mechanisms of light and heavy Majorana
neutrino as well as in that of Majoron emission. Such effects are expected to
occur in all nuclear models in the direction of reducing the light neutrino
matrix elements by about 30%. To test this we have performed a calculation of
the nuclear matrix elements of the experimentally interesting nuclei A = 76,
82, 96, 100, 116, 128, 130, 136 and 150 within the pn-RQRPA. We have found that
indeed such corrections vary somewhat from nucleus to nucleus, but in all cases
they are greater than 25 percent. In the case of heavy neutrino the effect is
much larger (a factor of 3). Combining out results with the best presently
available experimental limits on the half-life of the neutrinoless double beta
decay we have extracted new limits on the effective neutrino mass (light and
heavy) and the effective Majoron coupling constant.Comment: 31 pages, RevTex, 3 Postscript figures, submitted to Phys. Rev.
Neutrinoless Double Beta Decay in Gauge Theories
Neutrinoless double beta decay is a very important process both from the
particle and nuclear physics point of view. Its observation will severely
constrain the existing models and signal that the neutrinos are massive
Majorana particles. From the elementary particle point of view it pops up in
almost every model. In addition to the traditional mechanisms, like the
neutrino mass, the admixture of right handed currents etc, it may occur due to
the R-parity violating supersymmetric (SUSY) interactions. From the nuclear
physics point of view it is challenging, because: 1) The relevant nuclei have
complicated nuclear structure. 2) The energetically allowed transitions are
exhaust a small part of all the strength. 3) One must cope with the short
distance behavior of the transition operators, especially when the intermediate
particles are heavy (eg in SUSY models). Thus novel effects, like the double
beta decay of pions in flight between nucleons, have to be considered. 4) The
intermediate momenta involved are about 100 MeV. Thus one has to take into
account possible momentum dependent terms in the nucleon current. We find that,
for the mass mechanism, such modifications of the nucleon current for light
neutrinos reduce the nuclear matrix elements by about 25 per cent, almost
regardless of the nuclear model. In the case of heavy neutrinos the effect is
much larger and model dependent.
Taking the above effects into account, the available nuclear matrix elements
for the experimentally interesting nuclei A = 76, 82, 96, 100, 116, 128, 130,
136 and 150 and the experimental limits on the life times we have extracted new
stringent limits on the average neutrino mass and on the R-parity violating
coupling for various SUSY models.Comment: Latex, 24 pages, 1 postscript figure, uses iopconf.st
Spontaneous Abortion and Preterm Labor and Delivery in Nonhuman Primates: Evidence from a Captive Colony of Chimpanzees (Pan troglodytes)
Preterm birth is a leading cause of perinatal mortality, yet the evolutionary history of this obstetrical syndrome is largely unknown in nonhuman primate species.We examined the length of gestation during pregnancies that occurred in a captive chimpanzee colony by inspecting veterinary and behavioral records spanning a total of thirty years. Upon examination of these records we were able to confidently estimate gestation length for 93 of the 97 (96%) pregnancies recorded at the colony. In total, 78 singleton gestations resulted in live birth, and from these pregnancies we estimated the mean gestation length of normal chimpanzee pregnancies to be 228 days, a finding consistent with other published reports. We also calculated that the range of gestation in normal chimpanzee pregnancies is approximately forty days. Of the remaining fifteen pregnancies, only one of the offspring survived, suggesting viability for chimpanzees requires a gestation of approximately 200 days. These fifteen pregnancies constitute spontaneous abortions and preterm deliveries, for which the upper gestational age limit was defined as 2 SD from the mean length of gestation (208 days).The present study documents that preterm birth occurred within our study population of captive chimpanzees. As in humans, pregnancy loss is not uncommon in chimpanzees, In addition, our findings indicate that both humans and chimpanzees show a similar range of normal variation in gestation length, suggesting this was the case at the time of their last common ancestor (LCA). Nevertheless, our data suggest that whereas chimpanzees' normal gestation length is ∼20-30 days after reaching viability, humans' normal gestation length is approximately 50 days beyond the estimated date of viability without medical intervention. Future research using a comparative evolutionary framework should help to clarify the extent to which mechanisms at work in normal and preterm parturition are shared in these species
The Prevalence and Psychopathological Correlates of Sibling Bullying in Children with and without Autism Spectrum Disorder
Using data from a prospective population based study, the prevalence and psychopathological correlates of sibling bullying in children with and without autism spectrum disorder (ASD) were estimated. There were 475 children with ASD and 13,702 children without ASD aged 11Â years. Children with ASD were more likely to be bullied by their siblings compared to those without ASD. They were also more likely than those without ASD to both bully and be bullied by their siblings, which was associated with lower prosocial skills as well as more internalizing and externalizing problems compared to those not involved in any sibling bullying. Interventions to improve social and emotional outcomes in children with ASD should focus on both the affected and the unaffected sibling
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