Packaging of a large capacity magnetic bubble domain spacecraft recorder

A Solid State Spacecraft Data Recorder (SSDR), based on bubble domain technology, having a storage capacity of 10 to the 8th power bits, was designed and is being tested. The recorder consists of two memory modules each having 32 cells, each cell containing sixteen 100 kilobit serial bubble memory chips. The memory modules are interconnected to a Drive and Control Unit (DCU) module containing four microprocessors, 500 integrated circuits, a RAM core memory and two PROM's. The two memory modules and DCU are housed in individual machined aluminum frames, are stacked in brick fashion and through bolted to a base plate assembly which also houses the power supply

A technique for automatic real time scoring of several simultaneous sleep electroencephalograms

Automatic real-time scoring of simultaneous sleep electroencephalogram

Testing common classical LTE and NLTE model atmosphere and line-formation codes for quantitative spectroscopy of early-type stars

It is generally accepted that the atmospheres of cool/lukewarm stars of spectral types A and later are described well by LTE model atmospheres, while the O-type stars require a detailed treatment of NLTE effects. Here model atmosphere structures, spectral energy distributions and synthetic spectra computed with ATLAS9/SYNTHE and TLUSTY/SYNSPEC, and results from a hybrid method combining LTE atmospheres and NLTE line-formation with DETAIL/SURFACE are compared. Their ability to reproduce observations for effective temperatures between 15000 and 35000 K are verified. Strengths and weaknesses of the different approaches are identified. Recommendations are made as to how to improve the models in order to derive unbiased stellar parameters and chemical abundances in future applications, with special emphasis on Gaia science.Comment: 12 pages, 8 figures; accepted for publication in Journal of Physics: Conference Series, GREAT-ESF Workshop: Stellar Atmospheres in the Gaia Er

Search for L5 Earth Trojans with DECam

Most of the major planets in the Solar system support populations of co-orbiting bodies, known as Trojans, at their L4 and L5 Lagrange points. In contrast, Earth has only one known co-orbiting companion. This paper presents the results from a search for Earth Trojans (ETs) using the DECam instrument on the Blanco Telescope at CTIO. This search found no additional Trojans in spite of greater coverage compared to previous surveys of the L5 point. Therefore, the main result of this work is to place the most stringent constraints to date on the population of ETs. These constraints depend on assumptions regarding the underlying population properties, especially the slope of the magnitude distribution (which in turn depends on the size and albedo distributions of the objects). For standard assumptions, we calculate upper limits to a 90 per cent confidence limit on the L5 population of N_(ET) < 1 for magnitude H < 15.5, N_(ET) = 60–85 for H < 19.7, and N_(ET) = 97 for H = 20.4. This latter magnitude limit corresponds to Trojans ∼300 m in size for albedo 0.15. At H = 19.7, these upper limits are consistent with previous L4 ET constraints and significantly improve L5 constraints

DNA: From rigid base-pairs to semiflexible polymers

The sequence-dependent elasticity of double-helical DNA on a nm length scale can be captured by the rigid base-pair model, whose strains are the relative position and orientation of adjacent base-pairs. Corresponding elastic potentials have been obtained from all-atom MD simulation and from high-resolution structural data. On the scale of a hundred nm, DNA is successfully described by a continuous worm-like chain model with homogeneous elastic properties characterized by a set of four elastic constants, which have been directly measured in single-molecule experiments. We present here a theory that links these experiments on different scales, by systematically coarse-graining the rigid base-pair model for random sequence DNA to an effective worm-like chain description. The average helical geometry of the molecule is exactly taken into account in our approach. We find that the available microscopic parameters sets predict qualitatively similar mesoscopic parameters. The thermal bending and twisting persistence lengths computed from MD data are 42 and 48 nm, respectively. The static persistence lengths are generally much higher, in agreement with cyclization experiments. All microscopic parameter sets predict negative twist-stretch coupling. The variability and anisotropy of bending stiffness in short random chains lead to non-Gaussian bend angle distributions, but become unimportant after two helical turns.Comment: 13 pages, 6 figures, 6 table

Pristine CNO abundances from Magellanic Cloud B stars II. Fast rotators in the LMC cluster NGC 2004

We present spectroscopic abundance analyses of three main-sequence B stars in the young Large Magellanic Cloud cluster NGC 2004. All three targets have projected rotational velocities around 130 km/s. Techniques are presented that allow the derivation of stellar parameters and chemical abundances in spite of these high v sin i values. Together with previous analyses of stars in this cluster, we find no evidence among the main-sequence stars for effects due to rotational mixing up to v sin i around 130 km/s. Unless the equatorial rotational velocities are significantly larger than the v sin i values, this finding is probably in line with theoretical expectations. NGC 2004/B30, a star of uncertain evolutionary status located in the Blue Hertzsprung Gap, clearly shows signs of mixing in its atmosphere. To verify the effects due to rotational mixing will therefore require homogeneous analysis of statistically significant samples of low-metallicity main-sequence B stars over a wide range of rotational velocities.Comment: 12 pages, 5 figures, 2 tables; accepted for publication in ApJ (vol. 633, p. 899

The 10 to the 8th power bit solid state spacecraft data recorder

The results are summarized of a program to demonstrate the feasibility of Bubble Domain Memory Technology as a mass memory medium for spacecraft applications. The design, fabrication and test of a partially populated 10 to the 8th power Bit Data Recorder using 100 Kbit serial bubble memory chips is described. Design tradeoffs, design approach and performance are discussed. This effort resulted in a 10 to the 8th power bit recorder with a volume of 858.6 cu in and a weight of 47.2 pounds. The recorder is plug reconfigurable, having the capability of operating as one, two or four independent serial channel recorders or as a single sixteen bit byte parallel input recorder. Data rates up to 1.2 Mb/s in a serial mode and 2.4 Mb/s in a parallel mode may be supported. Fabrication and test of the recorder demonstrated the basic feasibility of Bubble Domain Memory technology for such applications. Test results indicate the need for improvement in memory element operating temperature range and detector performance

The Chandra Detection of Galactic Center X-ray Features G359.89-0.08 and G359.54+0.18

We report on the detection of two elongated X-ray features G359.89-0.08 and G359.54+0.18 in the Galactic center (GC) region using the Chandra X-ray Observatory. G359.89-0.08 is an elongated X-ray feature located $\sim$2\arcmin in projection south of the center of the Galaxy, SgrA$^*$. This X-ray feature source is partially coincident with a slightly curved (``wisp''-like) non-thermal radio source. The X-ray spectrum of G359.89-0.08 can be best characterized as non-thermal, with a photon index of 2. The morphological and spectral characteristics of the X-ray and radio emission associated with G359.89-0.08 are best interpreted as the synchrotron emission from a ram-pressure confined pulsar wind nebula. G359.54+0.18 is one of the most prominent radio non-thermal filaments (NTFs) in the GC region, located $\sim$30\arcmin in projection from SgrA$^*$. A narrow ($\sim$10\arcsec) filament of X-ray emission appears to arise from one of the two strands that comprise the radio NTF. Although the photon statistics are poor for this source, the X-ray emission is also likely to be non-thermal in nature. Several models for the production of X-ray emission in G359.54+0.18 are discussed.Comment: 19 pages with 6 figures included, accepted by A

The X-ray emitting galaxy Cen-A

OSO-8 X-ray observations of Cen-A in 1975 and 1976 are reported. The source spectrum is well fit in both years by a power law of number index 1.62 and absorption due to 1.3 x 10 to the 23rd power at/sq cm. The total flux varied by a factor 2 between 1975 and 1976. In 1976 there were approximately 40% flux variations on a time scale of days. The 6.4 keV Fe fluorescent line and the 7.1 keV absorption edge were measured implying Fe/H approximately equals .000016. Simultaneous radio measurements show variation in phase with X-ray variability. Models considering radio, milimeter, IR and X-ray data show that all the data can be accounted for by a model in which the X-rays are due to a synchrotron self-Compton source embedded in a cold H(2) cloud

Discovery of the Putative Pulsar and Wind Nebula Associated with the TeV Gamma-ray Source HESS J1813-178

We present a Chandra X-ray observation of G12.82-0.02, a shell-like radio supernova remnant coincident with the TeV gamma-ray source HESS J1813-178. We resolve the X-ray emission from the co-located ASCA source into a point source surrounded by structured diffuse emission that fills the interior of the radio shell. The morphology of the diffuse emission strongly resembles that of a pulsar wind nebula. The spectrum of the compact source is well-characterized by a power-law with index Gamma approx 1.3, typical of young and energetic rotation-powered pulsars. For a distance of 4.5 kpc, consistent with the X-ray absorption and an association with the nearby star formation region W33, the 2-10 keV X-ray luminosities of the putative pulsar and nebula are L(PSR) = 3.2E33 ergs/s and L(PWN) = 1.4E34 ergs/s, respectively. Both the flux ratio of L(PWN)/L(PSR) = 4.3 and the total luminosity of this system predict a pulsar spin-down power of Edot > 1E37 ergs/s, placing it within the ten most energetic young pulsars in the Galaxy. A deep search for radio pulsations using the Parkes telescope sets an upper-limit of approx 0.07 mJy at 1.4 GHz for periods >~ 50 ms. We discuss the energetics of this source, and consider briefly the proximity of bright H2 regions to this and several other HESS sources, which may produce their TeV emission via inverse Compton scattering.Comment: 7 pages, 6 figure, Latex, emulateapj style. To appear in the Astrophysical Journa