On the self-consistent model of the axisymmetric radio pulsar magnetosphere

We consider a model of axisymmetric neutron star magnetosphere. In our approach, the current density in the region of open field lines is constant and the returning current flows in a narrow layer along the separatrix. In this case, the stream equation describing the magnetic field structure is linear both in the open and closed regions, the main problem lying in matching the solutions along the separatrix (Okamoto 1974; Lyubarskii 1990). We demonstrate that it is the stability condition on the separatrix that allows us to obtain a unique solution of the problem. In particular, the zero point of magnetic field is shown to locate near the light cylinder. Moreover, the hypothesis of the existence of the nonlinear Ohm's Law (Beskin, Gurevich & Istomin 1983) connecting the potential drop in the pair creation region and the longitudinal electric current flowing in the magnetosphere is confirmed.Comment: 7 pages, 5 figures, twocolumn MNRAS styl

Amplification of magnetic fields by dynamo action in Gaussian-correlated helical turbulence

We investigate the growth and structure of magnetic fields amplified by kinematic dynamo action in turbulence with non-zero kinetic helicity. We assume a simple Gaussian velocity correlation tensor, which allows us to consider very large magnetic Reynolds numbers, up to one trillion. We use the kinematic Kazantsev-Kraichnan model of dynamo and find a complete numerical solution for the correlation functions of growing magnetic fields.Comment: 7 pages, 3 figure

Magnetic reconnection with anomalous resistivity in two-and-a-half dimensions I: Quasi-stationary case

In this paper quasi-stationary, two-and-a-half-dimensional magnetic reconnection is studied in the framework of incompressible resistive magnetohydrodynamics (MHD). A new theoretical approach for calculation of the reconnection rate is presented. This approach is based on local analytical derivations in a thin reconnection layer, and it is applicable to the case when resistivity is anomalous and is an arbitrary function of the electric current and the spatial coordinates. It is found that a quasi-stationary reconnection rate is fully determined by a particular functional form of the anomalous resistivity and by the local configuration of the magnetic field just outside the reconnection layer. It is also found that in the special case of constant resistivity reconnection is Sweet-Parker and not Petschek.Comment: 15 pages, 4 figures, minor changes as compared to the 1st versio

Structure of Small-Scale Magnetic Fields in the Kinematic Dynamo Theory

In the interstellar medium and protogalactic plasmas, the magnetic Prandtl number is very large, and the kinematic dynamo therefore produces a broad spectrum of growing magnetic fluctuations at small (subviscous) scales. The condition for the onset of nonlinear effects depends on the structure of the field lines. We study the statistical correlations that are set up in the field pattern and show that the magnetic-field lines possess a folding structure, where most of the scale decrease is due to the field variation across itself, while the scale of the field variation along itself stays approximately constant. Specifically, we find that, though both the magnetic energy and the mean square curvature of the field lines grow exponentially, the field strength and the field-line curvature are anticorrelated, i.e. the curved field is relatively weak, while the growing field is relatively flat. The detailed analysis of the statistics of the curvature shows that it possesses a stationary limiting distribution with the bulk located at the values of curvature comparable to the characteristic wave number of the velocity field and a power-like tail extending to large values of curvature where it is cut off by the resistive regularization. The growth of the curvature occurs in a small fraction of the total volume of the system, is due to the intermittent nature of the curvature distribution, and is limited only by the resistive cut-off. The implication of the folding effect is that the advent of the Lorentz back reaction occurs when the magnetic energy approaches that of the smallest turbulent eddies

Conduction and cooling flows

Chandra and XMM-Newton observations have confirmed the presence of large temperature gradients within the cores of many relaxed clusters of galaxies. Here we investigate whether thermal conduction operating over those gradients can supply sufficient heat to offset radiative cooling. Narayan & Medvedev (2001) and Gruzinov (2002) have noted, using published results on cluster temperatures, that conduction within a factor of a few of the Spitzer rate is sufficient to balance bremsstrahlung cooling. From a detailed study of the temperature and emission measure profiles of Abell 2199 and Abell 1835, we find that the heat flux required by conduction is consistent with or below the rate predicted by Spitzer in the outer regions of the core. Conduction may therefore explain the lack of observational evidence for large mass cooling rates inferred from arguments based simply on radiative cooling, provided that conductivity is suppressed by no more than a factor of three below the full Spitzer rate. To stem cooling in the cluster centre, however, would necessitate conductivity values at least a factor of two larger than the Spitzer values, which we consider implausible. This may provide an explanation for the observed star formation and optical nebulosities in cluster cores. The solution is likely to be time dependent. We briefly discuss the possible origin of the cooler gas and the implications for massive galaxies.Comment: 5 pages, 4 figures, accepted by MNRAS. Minor changes following referee's comment

Possibilities of laparoscopic diagnosis and elimination of acute adhesive intestinal obstruction

The study was undertaken to assess the diagnostic and therapeutic possibilities of video laparoscopy and the reasons for the failure of laparoscopic interventions in patients with acute adhesive intestinal obstruction in a city multi-field hospital. A retrospective analysis of laparoscopic interventions in 110 patients is presented. In 14 (12.7%) cases, the study allowed to exclude competing diagnoses and understand the true cause of the disease. In 19 (17.3%) cases, an attempt at laparoscopic diagnosis was unsuccessful. In 28 (25.5%) cases, laparoscopic attempts to eliminate obstruction were ineffective. In 20 (18%) cases after laparoscopic evaluation, a laparotomic method of treatment was immediately selected without attempting laparoscopic adhesiolysis. Laparoscopically, the adhesions that caused the disease were eliminated in 29 (26.4%) cases. At the same time, there is a potential possibility of increasing this indicator by up to 50% with timely laparoscopic intervention (before the development of excessive dilatation of the intestine). In cases where laparoscopic surgery was successful, they had all the advantages of minimally invasive interventions.Исследование предпринималось для оценки диагностических и лечебных возможностей видеолапароскопии и причин неудач лапароскопических вмешательств у больных острой спаечной кишечной непроходимостью в условиях городской многопрофильной больницы. Представлен ретроспективный анализ лапароскопических вмешательств у 110 пациентов. В 14 (12,7%) случаях исследование позволило исключить конкурирующие диагнозы и разобраться в истинной причине заболевания. В19 (17,3%) случаях попытка лапароскопической диагностики оказалась безуспешной. В 28 (25,5%) наблюдениях лапароскопические попытки устранения непроходимости оказались неэффективными. В 20 (18%) наблюдений после лапароскопической оценки сразу был избран лапаротомный способ лечения без попыток лапароскопического адгезиолизиса. Лапароскопически устранить спайки, явившиеся причиной болезни, удалось в 29 (26,4%) случаях. При этом имеется потенциальная возможность увеличения этого показателя до 50% при своевременном лапароскопическом вмешательстве (до развития чрезмерной дилатации кишки). В тех случаях, где лапароскопические операции удались, они обладали всеми преимуществами малоинвазивных вмешательств

New measurement of θ13\theta_{13} via neutron capture on hydrogen at Daya Bay

This article reports an improved independent measurement of neutrino mixing angle $\theta_{13}$ at the Daya Bay Reactor Neutrino Experiment. Electron antineutrinos were identified by inverse $\beta$-decays with the emitted neutron captured by hydrogen, yielding a data-set with principally distinct uncertainties from that with neutrons captured by gadolinium. With the final two of eight antineutrino detectors installed, this study used 621 days of data including the previously reported 217-day data set with six detectors. The dominant statistical uncertainty was reduced by 49%. Intensive studies of the cosmogenic muon-induced $^9$Li and fast neutron backgrounds and the neutron-capture energy selection efficiency, resulted in a reduction of the systematic uncertainty by 26%. The deficit in the detected number of antineutrinos at the far detectors relative to the expected number based on the near detectors yielded $\sin^22\theta_{13} = 0.071 \pm 0.011$ in the three-neutrino-oscillation framework. The combination of this result with the gadolinium-capture result is also reported.Comment: 26 pages, 23 figure

Evolution of the Reactor Antineutrino Flux and Spectrum at Daya Bay

The Daya Bay experiment has observed correlations between reactor core fuel evolution and changes in the reactor antineutrino flux and energy spectrum. Four antineutrino detectors in two experimental halls were used to identify 2.2 million inverse beta decays (IBDs) over 1230 days spanning multiple fuel cycles for each of six 2.9 GW$_{\textrm{th}}$ reactor cores at the Daya Bay and Ling Ao nuclear power plants. Using detector data spanning effective $^{239}$Pu fission fractions, $F_{239}$, from 0.25 to 0.35, Daya Bay measures an average IBD yield, $\bar{\sigma}_f$, of $(5.90 \pm 0.13) \times 10^{-43}$ cm$^2$/fission and a fuel-dependent variation in the IBD yield, $d\sigma_f/dF_{239}$, of $(-1.86 \pm 0.18) \times 10^{-43}$ cm$^2$/fission. This observation rejects the hypothesis of a constant antineutrino flux as a function of the $^{239}$Pu fission fraction at 10 standard deviations. The variation in IBD yield was found to be energy-dependent, rejecting the hypothesis of a constant antineutrino energy spectrum at 5.1 standard deviations. While measurements of the evolution in the IBD spectrum show general agreement with predictions from recent reactor models, the measured evolution in total IBD yield disagrees with recent predictions at 3.1$\sigma$. This discrepancy indicates that an overall deficit in measured flux with respect to predictions does not result from equal fractional deficits from the primary fission isotopes $^{235}$U, $^{239}$Pu, $^{238}$U, and $^{241}$Pu. Based on measured IBD yield variations, yields of $(6.17 \pm 0.17)$ and $(4.27 \pm 0.26) \times 10^{-43}$ cm$^2$/fission have been determined for the two dominant fission parent isotopes $^{235}$U and $^{239}$Pu. A 7.8% discrepancy between the observed and predicted $^{235}$U yield suggests that this isotope may be the primary contributor to the reactor antineutrino anomaly.Comment: 7 pages, 5 figure

Improved Measurement of the Reactor Antineutrino Flux and Spectrum at Daya Bay

A new measurement of the reactor antineutrino flux and energy spectrum by the Daya Bay reactor neutrino experiment is reported. The antineutrinos were generated by six 2.9~GW$_{\mathrm{th}}$ nuclear reactors and detected by eight antineutrino detectors deployed in two near (560~m and 600~m flux-weighted baselines) and one far (1640~m flux-weighted baseline) underground experimental halls. With 621 days of data, more than 1.2 million inverse beta decay (IBD) candidates were detected. The IBD yield in the eight detectors was measured, and the ratio of measured to predicted flux was found to be $0.946\pm0.020$ ($0.992\pm0.021$) for the Huber+Mueller (ILL+Vogel) model. A 2.9~$\sigma$ deviation was found in the measured IBD positron energy spectrum compared to the predictions. In particular, an excess of events in the region of 4-6~MeV was found in the measured spectrum, with a local significance of 4.4~$\sigma$. A reactor antineutrino spectrum weighted by the IBD cross section is extracted for model-independent predictions.Comment: version published in Chinese Physics