Radiofrequency power transfer to ion-cyclotron waves in a collision-free magnetoplasma

Radio frequency power transfer to ion cyclotron waves in collisionless plasma as function of magnetic field intensity and electron densit

One-year follow-up of family versus child CBT for anxiety disorders: Exploring the roles of child age and parental intrusiveness.

ObjectiveTo compare the relative long-term benefit of family-focused cognitive behavioral therapy (FCBT) and child-focused cognitive behavioral therapy (CCBT) for child anxiety disorders at a 1-year follow-up.MethodThirty-five children (6-13 years old) randomly assigned to 12-16 sessions of family-focused CBT (FCBT) or child-focused CBT (CCBT) participated in a 1-year follow-up assessment. Independent evaluators, parents, and children rated anxiety and parental intrusiveness. All were blind to treatment condition and study hypotheses.ResultsChildren assigned to FCBT had lower anxiety scores than children assigned to CCBT on follow-up diagnostician- and parent-report scores, but not child-report scores. Exploratory analyses suggested the advantage of FCBT over CCBT may have been evident more for early adolescents than for younger children and that reductions in parental intrusiveness may have mediated the treatment effect.ConclusionFCBT may yield a stronger treatment effect than CCBT that lasts for at least 1 year, although the lack of consistency across informants necessitates a circumspect view of the findings. The potential moderating and mediating effects considered in this study offer interesting avenues for further study

Parametric study of ion heating in a burnout device (HIP-1)

Results of further studies on the Lewis Research Center hot-ion plasma source (HIP-1) are reported. Changes have been made in both the electrode geometry and materials to produce higher ion temperatures. Ion temperature increased significantly with increased vacuum pumping speed. The best ion temperatures achieved, so far, for H(+), D(+), and He(+) plasmas are estimated to be equal to, or greater than 0.6, equal to, or greater than 0.9, and equal to, greater than 2.0 keV, respectively. Electrode pairs produced high ion temperatures whether on the magnetic axis or off it by 5.5 cm. Multiple sources, one on-axis and one off-axis, were run simultaneously from a single power supply by using independent gas feed rates. A momentum analyzer has been added to the charge-exchange neutral particle analyzer to identify particles according to mass, as well as energy. Under any given plasma condition, the higher mass ions have higher average energies but not by as much as the ratio of their respective masses

Subsurface tropical Pacific nitrogen isotopic composition of nitrate: Biogeochemical signals and their transport

We report measurements of the nitrogen isotopic composition of nitrate (the δ15N of NO3−) across the equatorial Pacific, for zonal transects from 165°E to 95°W and meridional transects across 95° and 110°W. The δ15N of NO3− is similar in the equatorial thermocline (≈100 m) and intermediate depth waters (≈150 to 600 m), averaging (7.1 ± 0.3)‰ and (7.1 ± 0.1)‰, respectively. These values are more than 2‰ higher than subthermocline waters of the Southern and Atlantic Oceans and are ≈1‰ higher than putative source waters in the high latitude South Pacific (Subantarctic Mode Water, SAMW). The combined constraints of nitrate concentration and δ15N of NO3−in the equatorial Pacific require (1) lateral exchange between the high‐latitude source waters and the zones of denitrification in the eastern tropical Pacific and (2) the accumulation of remineralized nutrients at depth. The zonal uniformity of the subsurface equatorial Pacificδ15N of NO3− indicates rapid transport within the equatorial zone, which works to homogenize the δ15N of NO3− across the Pacific basin. Against this backdrop of high δ15N of NO3−in the tropical Pacific, we find a discrete off‐equatorial core of lowerδ15N of NO3− (5.5 ± 0.3)‰ concentrated at 5°S and 150 to 200 m along the 110° and 95°W transects and in apparent association with the Southern Subsurface Counter Current (SSCC). We propose that the remineralized products of nitrogen fixation, at the source of the SSCC in the western south Pacific, are the origin of the low δ15N of NO3− in these waters

On a common circle: natural scenes and Gestalt rules

To understand how the human visual system analyzes images, it is essential to know the structure of the visual environment. In particular, natural images display consistent statistical properties that distinguish them from random luminance distributions. We have studied the geometric regularities of oriented elements (edges or line segments) present in an ensemble of visual scenes, asking how much information the presence of a segment in a particular location of the visual scene carries about the presence of a second segment at different relative positions and orientations. We observed strong long-range correlations in the distribution of oriented segments that extend over the whole visual field. We further show that a very simple geometric rule, cocircularity, predicts the arrangement of segments in natural scenes, and that different geometrical arrangements show relevant differences in their scaling properties. Our results show similarities to geometric features of previous physiological and psychophysical studies. We discuss the implications of these findings for theories of early vision.Comment: 3 figures, 2 large figures not include

Avoiding catastrophic failure in correlated networks of networks

Networks in nature do not act in isolation but instead exchange information, and depend on each other to function properly. An incipient theory of Networks of Networks have shown that connected random networks may very easily result in abrupt failures. This theoretical finding bares an intrinsic paradox: If natural systems organize in interconnected networks, how can they be so stable? Here we provide a solution to this conundrum, showing that the stability of a system of networks relies on the relation between the internal structure of a network and its pattern of connections to other networks. Specifically, we demonstrate that if network inter-connections are provided by hubs of the network and if there is a moderate degree of convergence of inter-network connection the systems of network are stable and robust to failure. We test this theoretical prediction in two independent experiments of functional brain networks (in task- and resting states) which show that brain networks are connected with a topology that maximizes stability according to the theory.Comment: 40 pages, 7 figure

Nitrogen and oxygen isotope constraints on the origin of atmospheric nitrate in coastal Antarctica

Throughout the year 2001, aerosol samples were collected continuously for 10 to 15 days at the French Antarctic Station Dumont d'Urville (DDU) (66°40' S, l40°0' E, 40 m above mean sea level). The nitrogen and oxygen isotopic ratios of particulate nitrate at DDU exhibit seasonal variations that are among the most extreme observed for nitrate on Earth. In association with concentration measurements, the isotope ratios delineate four distinct periods, broadly consistent with previous studies on Antarctic coastal areas. During austral autumn and early winter (March to mid-July), nitrate concentrations attain a minimum between 10 and 30 ng m^−3 (referred to as Period 2). Two local maxima in August (55 ng m^−3) and November/December (165 ng m^−3) are used to assign Period 3 (mid-July to September) and Period 4 (October to December). Period 1 (January to March) is a transition period between the maximum concentration of Period 4 and the background concentration of Period 2. These seasonal changes are reflected in changes of the nitrogen and oxygen isotope ratios. During Period 2, which is characterized by background concentrations, the isotope ratios are in the range of previous measurements at mid-latitudes: δ¹⁸O_vsmow=(77.2±8.6)‰; Δ¹⁷O=(29.8±4.4)‰; δ¹⁵N_air=(−4.4±5.4)‰ (mean ± one standard deviation). Period 3 is accompanied by a significant increase of the oxygen isotope ratios and a small increase of the nitrogen isotope ratio to δ¹⁸O_vsmow=(98.8±13.9)‰; Δ¹⁷O=(38.8±4.7)‰ and δ¹⁵N_air=(4.3±8.20‰). Period 4 is characterized by a minimum ¹⁵N/¹⁴N ratio, only matched by one prior study of Antarctic aerosols, and oxygen isotope ratios similar to Period 2: δ¹⁸O_vsmow=(77.2±7.7)‰; Δ¹⁷O=(31.1±3.2)‰; δ¹⁵N_air=(−32.7±8.4)‰. Finally, during Period 1, isotope ratios reach minimum values for oxygen and intermediate values for nitrogen: δ¹⁸O_vsmow=63.2±2.5‰; Δ¹⁷O=24.0±1.1‰; δ¹⁵N_air=−17.9±4.0‰). Based on the measured isotopic composition, known atmospheric transport patterns and the current understanding of kinetics and isotope effects of relevant atmospheric chemical processes, we suggest that elevated tropospheric nitrate levels during Period 3 are most likely the result of nitrate sedimentation from polar stratospheric clouds (PSCs), whereas elevated nitrate levels during Period 4 are likely to result from snow re-emission of nitrogen oxide species. We are unable to attribute the source of the nitrate during periods 1 and 2 to local production or long-range transport, but note that the oxygen isotopic composition is in agreement with day and night time nitrate chemistry driven by the diurnal solar cycle. A precise quantification is difficult, due to our insufficient knowledge of isotope fractionation during the reactions leading to nitrate formation, among other reasons

The auxiliary use of LANDSAT data in estimating crop acreages: Results of the 1975 Illinois crop-acreage experiment

The author has identified the following significant results. It was found that classifier performance was influenced by a number of temporal, methodological, and geographical factors. Best results were obtained when corn was tasselled and near the dough stage of development. Dates earlier or later in the growing season produced poor results. Atmospheric effects on results cannot be independently measured or completely separated from the effects due to the maturity stage of the crops. Poor classifier performance was observed in areas where considerable spectral confusion was present

Threshold and non-linear behavior of lasers of Λ\Lambda and V - configurations

Dynamic properties of closed three level laser systems are investigated. Two schemes of pumping - $\Lambda$ and V - are considered. It is shown that the non-linear behavior of the photon number as a function of pump both near and far above threshold is crucially different for these two configurations. In particular, it is found that in the high pump regime laser can turn off in a phase-transition-like manner in both $\Lambda$ and V schemes.Comment: 9 pages, 5 figure

Measuring the evolution of contemporary western popular music

Popular music is a key cultural expression that has captured listeners' attention for ages. Many of the structural regularities underlying musical discourse are yet to be discovered and, accordingly, their historical evolution remains formally unknown. Here we unveil a number of patterns and metrics characterizing the generic usage of primary musical facets such as pitch, timbre, and loudness in contemporary western popular music. Many of these patterns and metrics have been consistently stable for a period of more than fifty years, thus pointing towards a great degree of conventionalism. Nonetheless, we prove important changes or trends related to the restriction of pitch transitions, the homogenization of the timbral palette, and the growing loudness levels. This suggests that our perception of the new would be rooted on these changing characteristics. Hence, an old tune could perfectly sound novel and fashionable, provided that it consisted of common harmonic progressions, changed the instrumentation, and increased the average loudness.Comment: Supplementary materials not included. Please see the journal reference or contact the author