Adjustment of the electric current in pulsar magnetospheres and origin of subpulse modulation

The subpulse modulation of pulsar radio emission goes to prove that the plasma flow in the open field line tube breaks into isolated narrow streams. I propose a model which attributes formation of streams to the process of the electric current adjustment in the magnetosphere. A mismatch between the magnetospheric current distribution and the current injected by the polar cap accelerator gives rise to reverse plasma flows in the magnetosphere. The reverse flow shields the electric field in the polar gap and thus shuts up the plasma production process. I assume that a circulating system of streams is formed such that the upward streams are produced in narrow gaps separated by downward streams. The electric drift is small in this model because the potential drop in narrow gaps is small. The gaps have to drift because by the time a downward stream reaches the star surface and shields the electric field, the corresponding gap has to shift. The transverse size of the streams is determined by the condition that the potential drop in the gaps is sufficient for the pair production. This yields the radius of the stream roughly 10% of the polar cap radius, which makes it possible to fit in the observed morphological features such as the "carousel" with 10-20 subbeams and the system of the core - two nested cone beams.Comment: 8 pages, 1 figur

Generative Adversarial Networks for Scintillation Signal Simulation in EXO-200

Generative Adversarial Networks trained on samples of simulated or actual events have been proposed as a way of generating large simulated datasets at a reduced computational cost. In this work, a novel approach to perform the simulation of photodetector signals from the time projection chamber of the EXO-200 experiment is demonstrated. The method is based on a Wasserstein Generative Adversarial Network - a deep learning technique allowing for implicit non-parametric estimation of the population distribution for a given set of objects. Our network is trained on real calibration data using raw scintillation waveforms as input. We find that it is able to produce high-quality simulated waveforms an order of magnitude faster than the traditional simulation approach and, importantly, generalize from the training sample and discern salient high-level features of the data. In particular, the network correctly deduces position dependency of scintillation light response in the detector and correctly recognizes dead photodetector channels. The network output is then integrated into the EXO-200 analysis framework to show that the standard EXO-200 reconstruction routine processes the simulated waveforms to produce energy distributions comparable to that of real waveforms. Finally, the remaining discrepancies and potential ways to improve the approach further are highlighted.Comment: 20 pages, 10 figure

Search for Neutrinoless Double- β Decay with the Complete EXO-200 Dataset

A search for neutrinoless double-β decay (0νββ) in Xe136 is performed with the full EXO-200 dataset using a deep neural network to discriminate between 0νββ and background events. Relative to previous analyses, the signal detection efficiency has been raised from 80.8% to 96.4±3.0%, and the energy resolution of the detector at the Q value of Xe136 0νββ has been improved from σ/E=1.23% to 1.15±0.02% with the upgraded detector. Accounting for the new data, the median 90% confidence level 0νββ half-life sensitivity for this analysis is 5.0×1025 yr with a total Xe136 exposure of 234.1 kg yr. No statistically significant evidence for 0νββ is observed, leading to a lower limit on the 0νββ half-life of 3.5×1025 yr at the 90% confidence level

THE ROLE OF MINERAL NUTRITION ON YIELDS AND FRUIT QUALITY IN GRAPEVINE, PEAR AND APPLE

ABSTRACT Fertilization of temperate fruit trees, such as grapevine ( Vitis spp.), apple ( Malus domestica), and pear ( Pyrus communis) is an important tool to achive maximum yield and fruit quality. Fertilizers are provided when soil fertility does not allow trees to express their genetic potential, and time and rate of application should be scheduled to promote fruit quality. Grapevine berries, must and wine quality are affected principally by N, that regulate the synthesis of some important compounds, such as anthocyanins, which are responsible for coloring of the must and the wine. Fermenation of the must may stop in grapes with low concentration of N because N is requested in high amount by yeasts. An N excess may increase the pulp to peel ratio, diluting the concentration of anthocyanins and promoting the migration of anthocyanins from berries to the growing plant organs; a decrease of grape juice soluble solid concentration is also expected because of an increase in vegetative growth. Potassium is also important for wine quality contributing to adequate berry maturation, concentration of sugars, synthesis of phenols and the regulation of pH and acidity. In apple and pear, Ca and K are important for fruit quality and storage. Potassium is the most important component of fruit, however, any excess should be avoided and an adequate K:Ca balance should be achieved. Adequate concentration of Ca in the fruit prevents pre- and post-harvest fruit disorders and, at the same time, increases tolerance to pathogens. Although N promotes adequate growth soil N availability should be monitored to avoid excessive N uptake that may decrease fruit skin color and storability

Search for Neutrinoless Double-Beta Decay with the Upgraded EXO-200 Detector

Results from a search for neutrinoless double-beta decay (0νββ) of Xe136 are presented using the first year of data taken with the upgraded EXO-200 detector. Relative to previous searches by EXO-200, the energy resolution of the

IDENTIFYING THE MYSTERIOUS EGRET SOURCES: SIGNATURES OF POLAR CAP PULSAR MODELS

The advent of the next generation of gamma-ray experiments, led by GLAST, AGILE, INTEGRAL and a host of atmospheric Čerenkov telescopes coming on line in the next few years, will enable ground-breaking discoveries relating to the presently enigmatic set of EGRET/CGRO UID galactic sources that have yet to find definitive identifications. Pulsars are principal candidates for such sources, and many are expected to be detected by GLAST, some that are radio-selected, like most of the present EGRET/Comptel pulsars, and perhaps even more that are detected via independent pulsation searches. At this juncture, it is salient to outline the principal predictions of pulsar models that might aid identification of gamma-ray sources, and moreover propel subsequent interpretation of their properties. This review summarizes relevant characteristics of the polar cap model, emphasizing where possible distinctions from the competing outer gap model. Foremost among these considerations are the hard X-ray to gamma-ray spectral shape, high energy cutoffs and pulse profiles, and how these characteristics generally depend on pulsar period and period derivative, as well as observational viewing angle. The polar cap model exhibits definitive signatures that will be readily tested by the detections of GLAST and other experiments, thereby establishing cogent observational diagnostics. The paper focuses on different classes of pulsars that might define agendas and parameter regimes for blind gamma-ray pulsation searches; examples include the highly-magnetized ones that are currently quite topical in astrophysics. 1 2 1