The Reed-Solomon encoders: Conventional versus Berlekamp's architecture

Concatenated coding was adopted for interplanetary space missions. Concatenated coding was employed with a convolutional inner code and a Reed-Solomon (RS) outer code for spacecraft telemetry. Conventional RS encoders are compared with those that incorporate two architectural features which approximately halve the number of multiplications of a set of fixed arguments by any RS codeword symbol. The fixed arguments and the RS symbols are taken from a nonbinary finite field. Each set of multiplications is bit-serially performed and completed during one (bit-serial) symbol shift. All firmware employed by conventional RS encoders is eliminated

System for generating timing and control signals

A system capable of generating every possible data frame subperiod and delayed subperiod of a data frame of length of M clock pulse intervals (CPIs) comprised of parallel modulo-m sub i counters is presented. Each m sub i is a prime power divisor of M and a cascade of alpha sub i identical modulo-p sub i counters. The modulo-p sub i counters are feedback shift registers which cycle through p sub i distinct states. Every possible nontrivial data frame subperiod and delayed subperiod is derived and a specific CPI in the data frame is detected. The number of clock pulses required to bring every modulo-p sub i counter to a respective designated state or count is determined by the Chinese remainder theorem. This corresponds to the solution of simultaneous congruences over relatively prime moduli

Propionibacterium acnes infections in patients with idiopathic scoliosis: a case-control study and review of the literature.

Purpose:Surgical site infection (SSI) caused by Propionibacterium acnes is an infrequent but devastating complication after spinal fusion. The purpose of this study was to identify risk factors for SSI with Propionibacterium acnes after spinal fusion for juvenile and adolescent idiopathic scoliosis (JIS and AIS). Methods:A case-control study was performed. Each case was matched 2:1 for age, gender and diagnosis. Retrospective chart review was performed to obtain relevant demographic, surgical and clinical data for all cases and controls. Statistical analysis included paired t-test and McNemar test, as well as exact logistic regression and robust regression models. Results:This study included ten infection cases (eight AIS, two JIS) and 20 controls (16 AIS, four JIS). In total, six infected cases presented within two weeks of the index procedure (acute infection) and four infected cases presented more than one year from the index procedure (delayed infection). The most common presentation for acute infections was wound drainage, while back pain was more common in delayed infections. All infections were successfully treated with surgical irrigation and debridement and postoperative antibiotics. Hardware was removed for patients with delayed infections. The strongest risk factor for infection was increased requirement for blood transfusion, but it did not reach statistical significance. Conclusion:SSI with Propionibacterium acnes is an important complication after spinal fusion for idiopathic scoliosis. These infections can be successfully treated, but larger studies are needed to further identify risk factors and establish standardized guidelines for the treatment and prevention of this complication. Level of Evidence Level III

The role of the synchrotron component in the mid infrared spectrum of M 87

We study in detail the mid-infrared Spitzer-IRS spectrum of M 87 in the range 5 to 20 micron. Thanks to the high sensitivity of our Spitzer-IRS spectra we can disentangle the stellar and nuclear components of this active galaxy. To this end we have properly subtracted from the M 87 spectrum, the contribution of the underlying stellar continuum, derived from passive Virgo galaxies in our sample. The residual is a clear power-law, without any additional thermal component, with a zero point consistent with that obtained by high spatial resolution, ground based observations. The residual is independent of the adopted passive template. This indicates that the 10 micron silicate emission shown in spectra of M 87 can be entirely accounted for by the underlying old stellar population, leaving little room for a possible torus contribution. The MIR power-law has a slope alpha ~ 0.77-0.82 (S$_\nu\propto\nu^{-\alpha}$), consistent with optically thin synchrotron emission.Comment: 5 pages, 4 figures, accepted for publication in ApJ main journa

Iconicity and ape gesture.

Iconic gestures are hypothesized to be c rucial to the evolution of language. Yet the important question of whether apes produce iconic gestures is the subject of considerable debate. This paper presents the current state of research on iconicity in ape gesture. In particular, it describes some of the empirical evidence suggesting that apes produce three different kinds of iconic gestures; it compares the iconicity hypothesis to other major hypotheses of ape gesture; and finally, it offers some directions for future ape gesture researc

X-ray Emission Properties of Large Scale Jets, Hotspots and Lobes in Active Galactic Nuclei

We examine a systematic comparison of jet-knots, hotspots and radio lobes recently observed with Chandra and ASCA. This report will discuss the origin of their X-ray emissions and investigate the dynamics of the jets. The data was compiled at well sampled radio (5GHz) and X-ray frequencies (1keV) for more than 40 radio galaxies. We examined three models for the X-ray production: synchrotron (SYN), synchrotron self-Compton (SSC) and external Compton on CMB photons (EC). For the SYN sources -- mostly jet-knots in nearby low-luminosity radio galaxies -- X-ray photons are produced by ultrarelativistic electrons with energies 10-100 TeV that must be accelerated in situ. For the other objects, conservatively classified as SSC or EC sources, a simple formulation of calculating the ``expected'' X-ray fluxes under an equipartition hypothesis is presented. We confirmed that the observed X-ray fluxes are close to the expected ones for non-relativistic emitting plasma velocities in the case of radio lobes and majority of hotspots, whereas considerable fraction of jet-knots is too bright at X-rays to be explained in this way. We examined two possibilities to account for the discrepancy in a framework of the inverse-Compton model: (1) magnetic field is much smaller than the equipartition value, and (2) the jets are highly relativistic on kpc/Mpc scales. We concluded, that if the inverse-Compton model is the case, the X-ray bright jet-knots are most likely far from the minimum-power condition. We also briefly discuss the other possibility, namely that the observed X-ray emission from all of the jet-knots is synchrotron in origin.Comment: 20 pages, 10 figures, accepted for publication in the Astrophysical Journal, vol.62

Continuing a Chandra Survey of Quasar Radio Jets

We are conducting an X-ray survey of flat spectrum radio quasars (FSRQs) with extended radio structures. We summarize our results from the first stage of our survey, then we present findings from its continuation. We have discovered jet X-ray emission from 12 of our first 20 Chandra targets, establishing that strong 0.5-7.0 keV emission is a common feature of FSRQ jets. The X-ray morphology is varied, but in general closely matches the radio structure until the first sharp radio bend. In the sources with optical data as well as X-ray detections we rule out simple synchrotron models for X-ray emission, suggesting these systems may instead be dominated by inverse Compton (IC) scattering. Fitting models of IC scattering of cosmic microwave background photons suggests that these jets are aligned within a few degrees of our line of sight, with bulk Lorentz factors of a few to ten and magnetic fields a bit stronger than $10^{-5}$ G. In the weeks prior to this meeting, we have discovered two new X-ray jets at $z > 1$. One (PKS B1055+201) has a dramatic, $20''$-long jet. The other (PKS B1421-490) appears unremarkable at radio frequencies, but at higher frequencies the jet is uniquely powerful: its optically-dominated, with jet/core flux ratios of 3.7 at 1 keV and 380 at 480 nm.Comment: 4 pages, 8 figures. To appear in `X-Ray and Radio Connections', ed. L.O. Sjouwerman and K.K. Dyer (published electronicly at http://www.aoc.nrao.edu/events/xraydio/). Additional material and higher resolution figures may be found at http://space.mit.edu/home/jonathan/jets

Optical spectroscopy of microquasar candidates at low galactic latitudes

We report optical spectroscopic observations of a sample of 6 low-galactic latitude microquasar candidates selected by cross-identification of X-ray and radio point source catalogs for |b|<5 degrees. Two objects resulted to be of clear extragalactic origin, as an obvious cosmologic redshift has been measured from their emission lines. For the rest, none exhibits a clear stellar-like spectrum as would be expected for genuine Galactic microquasars. Their featureless spectra are consistent with being extragalactic in origin although two of them could be also highly reddened stars. The apparent non-confirmation of our candidates suggests that the population of persistent microquasar systems in the Galaxy is more rare than previously believed. If none of them is galactic, the upper limit to the space density of new Cygnus X-3-like microquasars within 15 kpc would be 1.1\times10^{-12} per cubic pc. A similar upper limit for new LS 5039-like systems within 4 kpc is estimated to be 5.6\times10^{-11} per cubic pc.Comment: 7 pages, 7 figures. Published in A&A, see http://adsabs.harvard.edu/cgi-bin/nph-bib_query?bibcode=2004A%26A...413..309

The Mid-Infrared Emission of M87

We discuss Subaru and Spitzer Space Telescope imaging and spectroscopy of M87 in the mid-infrared from 5-35 um. These observations allow us to investigate mid-IR emission mechanisms in the core of M87 and to establish that the flaring, variable jet component HST-1 is not a major contributor to the mid-IR flux. The Spitzer data include a high signal-to-noise 15-35 $\mu$m spectrum of the knot A/B complex in the jet, which is consistent with synchrotron emission. However, a synchrotron model cannot account for the observed {\it nuclear} spectrum, even when contributions from the jet, necessary due to the degrading of resolution with wavelength, are included. The Spitzer data show a clear excess in the spectrum of the nucleus at wavelengths longer than 25 um, which we model as thermal emission from cool dust at a characteristic temperature of 55 \pm 10 K, with an IR luminosity \sim 10^{39} {\rm ~erg ~s^{-1}}. Given Spitzer's few-arcsecond angular resolution, the dust seen in the nuclear spectrum could be located anywhere within ~5'' (390 pc) of the nucleus. In any case, the ratio of AGN thermal to bolometric luminosity indicates that M87 does not contain the IR-bright torus that classical unified AGN schemes invoke. However, this result is consistent with theoretical predictions for low-luminosity AGNsComment: 9 pages, 7 figures, ApJ, in pres