Digital system detects binary code patterns containing errors

System of square loop magnetic cores associated with code input registers to react to input code patterns by reference to a group of control cores in such a manner that errors are canceled and patterns containing errors are accepted for amplification and processing. This technique improves reception capabilities in PCM telemetry systems

The contrast of magnetic elements in synthetic CH- and CN-band images of solar magnetoconvection

We present a comparative study of the intensity contrast in synthetic CH-band and violet CN-band filtergrams computed from a high-resolution simulation of solar magnetoconvection. The underlying simulation has an average vertical magnetic field of 250 G with kG fields concentrated in its intergranular lanes, and is representative of a plage region. To simulate filtergrams typically obtained in CH- and CN-band observations we computed spatially resolved spectra in both bands and integrated these spectra over 1 nm FWHM filter functions centred at 430.5 nm and 388.3 nm, respectively. We find that the average contrast of magnetic bright points in the simulated filtergrams is lower in the CN-band by a factor of 0.96. This result strongly contradicts earlier semi-empirical modeling and recent observations, which both etimated that the bright-point contrast in the CN-band is \emph{higher} by a factor of 1.4. We argue that the near equality of the bright-point contrast in the two bands in the present simulation is a natural consequence of the mechanism that causes magnetic flux elements to be particularly bright in the CN and CH filtergrams, namely the partial evacuation of these elements and the concomitant weakening of molecular spectral lines in the filter passbands. We find that the RMS intensity contrast in the whole field-of-view of the filtergrams is 20.5% in the G band and 22.0% in the CN band and conclude that this slight difference in contrast is caused by the shorter wavelength of the latter. Both the bright-point and RMS intensity contrast in the CN band are sensitive to the precise choice of the central wavelength of the filter.Comment: 24 pages, 9 figures, submitted to Ap

Nuclear Matter on a Lattice

We investigate nuclear matter on a cubic lattice. An exact thermal formalism is applied to nucleons with a Hamiltonian that accommodates on-site and next-neighbor parts of the central, spin- and isospin-exchange interactions. We describe the nuclear matter Monte Carlo methods which contain elements from shell model Monte Carlo methods and from numerical simulations of the Hubbard model. We show that energy and basic saturation properties of nuclear matter can be reproduced. Evidence of a first-order phase transition from an uncorrelated Fermi gas to a clustered system is observed by computing mechanical and thermodynamical quantities such as compressibility, heat capacity, entropy and grand potential. We compare symmetry energy and first sound velocities with literature and find reasonable agreement.Comment: 23 pages, 8 figures (some in color), to be submitted to Phys. Rev.

The Zeeman effect in the G band

We investigate the possibility of measuring magnetic field strength in G-band bright points through the analysis of Zeeman polarization in molecular CH lines. To this end we solve the equations of polarized radiative transfer in the G band through a standard plane-parallel model of the solar atmosphere with an imposed magnetic field, and through a more realistic snapshot from a simulation of solar magneto-convection. This region of the spectrum is crowded with many atomic and molecular lines. Nevertheless, we find several instances of isolated groups of CH lines that are predicted to produce a measurable Stokes V signal in the presence of magnetic fields. In part this is possible because the effective Land\'{e} factors of lines in the stronger main branch of the CH A$^{2}\Delta$--X$^{2}\Pi$ transition tend to zero rather quickly for increasing total angular momentum $J$, resulting in a Stokes $V$ spectrum of the G band that is less crowded than the corresponding Stokes $I$ spectrum. We indicate that, by contrast, the effective Land\'{e} factors of the $R$ and $P$ satellite sub-branches of this transition tend to $\pm 1$ for increasing $J$. However, these lines are in general considerably weaker, and do not contribute significantly to the polarization signal. In one wavelength location near 430.4 nm the overlap of several magnetically sensitive and non-sensitive CH lines is predicted to result in a single-lobed Stokes $V$ profile, raising the possibility of high spatial-resolution narrow-band polarimetric imaging. In the magneto-convection snapshot we find circular polarization signals of the order of 1% prompting us to conclude that measuring magnetic field strength in small-scale elements through the Zeeman effect in CH lines is a realistic prospect.Comment: 22 pages, 6 figures. To be published in the Astrophysical Journa

The size distribution of magnetic bright points derived from Hinode/SOT observations

Context. Magnetic Bright Points (MBPs) are small-scale magnetic features in the solar photosphere. They may be a possible source of coronal heating by rapid footpoint motions that cause magnetohydrodynamical waves. The number and size distribution are of vital importance in estimating the small scale-magnetic-field energy. Aims. The size distribution of MBPs is derived for G-band images acquired by the Hinode/SOT instrument. Methods. For identification purposes, a new automated segmentation and identification algorithm was developed. Results. For a sampling of 0.108 arcsec/pixel, we derived a mean diameter of (218 +- 48) km for the MBPs. For the full resolved data set with a sampling of 0.054 arcsec/pixel, the size distribution shifted to a mean diameter of (166 +- 31) km. The determined diameters are consistent with earlier published values. The shift is most probably due to the different spatial sampling. Conclusions. We conclude that the smallest magnetic elements in the solar photosphere cannot yet be resolved by G-band observations. The influence of discretisation effects (sampling) has also not yet been investigated sufficiently.Comment: Astronomy and Astrophysics, Volume 498, Issue 1, 2009, pp.289-29

A high-resolution mm and cm study of the obscured LIRG NGC 4418 - A compact obscured nucleus fed by in-falling gas?

The aim of this study is to constrain the dynamics, structure and feeding of the compact nucleous of NGC4418, and to reveal the nature of the main hidden power source: starburst or AGN. We obtained high spatial resolution observations of NGC4418 at 1.4 and 5 GHz with MERLIN, and at 230 and 270 GHz with the SMA very extended configuration. We use the continuum morphology and flux density to estimate the size of the emitting region, the star formation rate and the dust temperature. Emission lines are used to study the kinematics through position-velocity diagrams. Molecular emission is studied with population diagrams and by fitting an LTE synthetic spectrum. We detect bright 1mm line emission from CO, HC3N, HNC and C34S, and 1.4 GHz absorption from HI. The CO 2-1 emission and HI absorption can be fit by two velocity components at 2090 and 2180 km s-1. We detect vibrationally excited HC3N and HNC, with Tvib 300K. Molecular excitation is consistent with a layered temperature structure, with three main components at 80, 160 and 300 K. For the hot component we estimate a source size of less than 5 pc. The nuclear molecular gas surface density of 1e4 Msun pc-2 is extremely high, and similar to that found in the ultra-luminous infrared galaxy (ULIRG) Arp220. Our observations confirm the the presence of a molecular and atomic in-flow, previously suggested by Herschel observations, which is feeding the activity in the center of NGC4418. Molecular excitation confirms the presence of a very compact, hot dusty core. If a starburst is responsible for the observed IR flux, this has to be at least as extreme as the one in Arp220, with an age of 3-10 Myr and a star formation rate >10 Msun yr-1. If an AGN is present, it must be extremely Compton-thick.Comment: 18 pages, 11 figures, Accepted for publication by A&A on 10/6/201

Dynamic behavior of porous electrode systems final report

Mathematical model of flooded porous electrodes under dynamic and static conditions - Methods for measuring porous electrode reaction distributio

Gravitational Waves from Axisymmetric, Rotational Stellar Core Collapse

We have carried out an extensive set of two-dimensional, axisymmetric, purely-hydrodynamic calculations of rotational stellar core collapse with a realistic, finite-temperature nuclear equation of state and realistic massive star progenitor models. For each of the total number of 72 different simulations we performed, the gravitational wave signature was extracted via the quadrupole formula in the slow-motion, weak-field approximation. We investigate the consequences of variation in the initial ratio of rotational kinetic energy to gravitational potential energy and in the initial degree of differential rotation. Furthermore, we include in our model suite progenitors from recent evolutionary calculations that take into account the effects of rotation and magnetic torques. For each model, we calculate gravitational radiation wave forms, characteristic wave strain spectra, energy spectra, final rotational profiles, and total radiated energy. In addition, we compare our model signals with the anticipated sensitivities of the 1st- and 2nd-generation LIGO detectors coming on line. We find that most of our models are detectable by LIGO from anywhere in the Milky Way.Comment: 13 pages, 22 figures, accepted for publication in ApJ (v600, Jan. 2004). Revised version: Corrected typos and minor mistakes in text and references. Minor additions to the text according to the referee's suggestions, conclusions unchange

Hot subdwarf stars in close-up view. I. Rotational properties of subdwarf B stars in close binary systems and nature of their unseen companions

Original article can be found at: http://www.aanda.org/ Copyright The European Southern Observatory (ESO)The origin of hot subdwarf B stars (sdBs) is still unclear. About half of the known sdBs are in close binary systems for which common envelope ejection is the most likely formation channel. Little is known about this dynamic phase of binary evolution. Since most of the known sdB systems are single-lined spectroscopic binaries, it is difficult to derive masses and unravel the companions' nature, which is the aim of this paper. Due to the tidal influence of the companion in close binary systems, the rotation of the primary becomes synchronised to its orbital motion. In this case it is possible to constrain the mass of the companion, if the primary mass, its projected rotational velocity as well as its surface gravity are known. For the first time we measured the projected rotational velocities of a large sdB binary sample from high resolution spectra. We analysed a sample of 51 sdB stars in close binaries, 40 of which have known orbital parameters comprising half of all such systems known today. Synchronisation in sdB binaries is discussed both from the theoretical and the observational point of view. The masses and the nature of the unseen companions could be constrained in 31 cases. We found orbital synchronisation most likely to be established in binaries with orbital periods shorter than . Only in five cases it was impossible to decide whether the sdB's companion is a white dwarf or an M dwarf. The companions to seven sdBs could be clearly identified as late M stars. One binary may have a brown dwarf companion. The unseen companions of nine sdBs are white dwarfs with typical masses. The mass of one white dwarf companion is very low. In eight cases (including the well known system KPD1930+2752) the companion mass exceeds , four of which even exceed the Chandrasekhar limit indicating that they may be neutron stars. Even stellar mass black holes are possible for the most massive companions. The distribution of the inclinations of the systems with low mass companions appears to be consistent with expectations, whereas a lack of high inclinations becomes obvious for the massive systems. We show that the formation of such systems can be explained with common envelope evolution and present an appropriate formation channel including two phases of unstable mass transfer and one supernova explosion. The sample also contains a candidate post-RGB star, which rotates fast despite its long orbital period. The post-RGB stars are expected to spin-up caused by their ongoing contraction. The age of the sdB is another important factor. If the EHB star is too young, the synchronisation process might not be finished yet. Estimating the ages of the target stars from their positions on the EHB band, we found PG 2345+318, which is known not to be synchronised, to lie near the zero-age extreme horizontal branch as are the massive candidates PG 1232-136, PG 1432+159 and PG 1101+249. These star may possibly be too young to have reached synchronisation. The derived large fraction of putative massive sdB binary systems in low inclination orbits is inconsistent with theoretical predictions. Even if we dismiss three candidates because they may be too young and assume that the other sdB primaries are of low mass, PG 1743+477 and, in particular, HE 0532-4503 remain as candidates whose companions may have masses close to or above the Chandrasekhar limit. X-ray observations and accurate photometry are suggested to clarify their nature. As high inclination systems must also exist, an appropriate survey has already been launched to find such binaries.Peer reviewe