2,571 research outputs found
Digital control of diode laser for atmospheric spectroscopy
A system is described for remote absorption spectroscopy of trace species using a diode laser tunable over a useful spectral region of 50 to 200 cm(-1) by control of diode laser temperature over range from 15 K to 100 K, and tunable over a smaller region of typically 0.1 to 10 cm(-1) by control of the diode laser current over a range from 0 to 2 amps. Diode laser temperature and current set points are transmitted to the instrument in digital form and stored in memory for retrieval under control of a microprocessor during measurements. The laser diode current is determined by a digital to analog converter through a field effect transistor for a high degree of ambient temperature stability, while the laser diode temperature is determined by set points entered into a digital to analog converter under control of the microprocessor. Temperature of the laser diode is sensed by a sensor diode to provide negative feedback to the temperature control circuit that responds to the temperature control digital to analog converter
Thermal emission from low-field neutron stars
We present a new grid of LTE model atmospheres for weakly magnetic
(B<=10e10G) neutron stars, using opacity and equation of state data from the
OPAL project and employing a fully frequency- and angle-dependent radiation
transfer. We discuss the differences from earlier models, including a
comparison with a detailed NLTE calculation. We suggest heating of the outer
layers of the neutron star atmosphere as an explanation for the featureless
X-ray spectra of RX J1856.5-3754 and RX J0720.4-3125 recently observed with
Chandra and XMM.Comment: 8 pages A&A(5)-Latex, 6 Figures, A&A in press. The model spectra
presented here are available as XSPEC tables at
http://www.astro.soton.ac.uk/~btg/outgoing/nsspec
I Kiss\u27d You In A Dream : Song And Chorus
https://digitalcommons.library.umaine.edu/mmb-vp/1663/thumbnail.jp
De Old Churchyard In De Lane
Old man reading to young girl under treehttps://scholarsjunction.msstate.edu/cht-sheet-music/13648/thumbnail.jp
Formed by Place: Spatiality, Irony, and Empire in Conradâs âAn Outpost of Progressâ
In its ironic narrative and distinctive geography, Joseph Conradâs 1897 short story âAn Outpost of Progressâ is well suited for geocritical analysis, insofar as Conrad demonstrates the degree to which space and place affect both the characters in the story and style of the text. Focusing on the unique settingâthe âoutpostââin which the events take place, Rutledge and Tally argue that Conradâs tale employs an ironic narrator in order to highlight the taleâs distinctive spatiality, particularly with respect to a geopolitical system that too neatly divides the spaces of the globe into civilized and barbaric regions. The spatiality of âAn Outpost of Progressâ can be seen in the geographical aspects of the narrative, with the specific site or heterotopia of the âoutpostâ situated at the edge of a territory coded as âbarbaricâ or âuncivilized,â thus connecting the colonized domain in central Africa to the metropolitan society of northwestern Europe, largely unseen, but implicitly present throughout the story. But this spatiality may also be observed in its formal or stylistic elements, especially in the point of view and voice of the narrator, as the perspective shifts from omniscient overseer to ironic commentator and then to a free indirect style in which the distance between narrator and subject is dramatically reduced. In this way, Conrad produces an ironic, spatial narrative that highlights, in both content and form, the absurdity of the imperialist âcivilizing missionâ in Africa
Evolution of Massive Haloes in non-Gaussian Scenarios
We have performed high-resolution cosmological N-body simulations of a
concordance LCDM model to study the evolution of virialized, dark matter haloes
in the presence of primordial non-Gaussianity. Following a standard procedure,
departures from Gaussianity are modeled through a quadratic Gaussian term in
the primordial gravitational potential, characterized by a dimensionless
non-linearity strength parameter f_NL. We find that the halo mass function and
its redshift evolution closely follow the analytic predictions of Matarrese et
al.(2000). The existence of precise analytic predictions makes the observation
of rare, massive objects at large redshift an even more attractive test to
detect primordial non-Gaussian features in the large scale structure of the
universe.Comment: 7 pages,3 figures, submitted to MNRA
A Review of Electrospun Carbon Fibers as Electrode Materials for Energy Storage
The applications of electrospun carbon fiber webs to the development of energy storages devices, including both supercapacitors and lithium ion batteries (LIB) , are reviewed. Following a brief discussion of the fabrication process and characterization methods for ultrafine electrospun carbon fibers, recent advances in their performance as supercapacitors and LIBs anode materials are summarized. Optimization of the overall electrochemical properties of these materials through choice of thermal treatment conditions, incorporation of additional active components (such as carbon nanotubes, metal oxides, and catalysts), and generation of novel fibrous structures (such as core-shell, multi-channel or porous fibers) is highlighted. Further challenges related to improving the conductivity, surface area, and mechanical properties of the carbon nanofiber webs, as well as the scale-up ability of the fabrication technique, are discussed.United States. Dept. of Energ
Imaging Polarimeter Arrays for Near-Millimeter Waves
An integrated-circuit antenna array has been developed that images both polarization and intensity. The array consists of a row of antennas that lean alternately left and right, creating two interlaced sub-arrays that respond to different polarizations. The arrays and the bismuth bolometer detectors are made by a photoresist shadowing technique that requires only one photolithographic mask. The array has measured polarization at a wavelength of 800 ”m with an absolute accuracy of 0.8° and a relative precision of 7 arc min. and has demonstrated nearly diffraction-Iimited resolutiort of a 20° step in polarization
Ecological PrinciplesâA Unifying Theme in Environmental Education
Using ecological principles to form the basis of a succinct list of general environmental education (EE) standards will bring unity and strength to EE. Environmental education literature supports the importance of understanding general ecological principles, and general ecological concepts are prevalent in both widely used and locally adapted EE programs. In addition, an understanding of general ecological principles is included in both NSES (National Science Education Standards) and NAAEE Guidelines for Excellence. This article presents an analysis of the frequency of ecological references in several EE programs and discusses the implications of general ecological principles as a common thread in EE
Chandra observation of the fast X-ray transient IGR J17544-2619: evidence for a neutron star?
IGR J17544-2619 belongs to a distinct group of at least seven fast X-ray
transients that cannot readily be associated with nearby flare stars or
pre-main sequence stars and most probably are X-ray binaries with wind
accretion. Sofar, the nature of the accretor has been determined in only one
case (SAX J1819.3-2525/V4641 Sgr). We carried out a 20 ks Chandra ACIS-S
observation of IGR J17544-2619 which shows the source in quiescence going into
outburst. The Chandra position confirms the previous tentative identification
of the optical counterpart, a blue O9Ib supergiant at 3 to 4 kpc (Pellizza,
Chaty & Negueruela, in prep.). This is the first detection of a fast X-ray
transient in quiescence. The quiescent spectrum is very soft. The photon index
of 5.9+/-1.2 (90% confidence error margin) is much softer than 6 quiescent
black hole candidates that were observed with Chandra ACIS-S (Kong et al. 2002;
Tomsick et al. 2003). Assuming that a significant fraction of the quiescent
photons comes from the accretor and not the donor star, we infer that the
accretor probably is a neutron star. A fit to the quiescent spectrum of the
neutron star atmosphere model developed by Pavlov et al. (1992) and Zavlin et
al. (1996) implies an unabsorbed quiescent 0.5--10 keV luminosity of
(5.2+/-1.3) x 10^32 erg/s. We speculate on the nature of the brief outbursts.Comment: accepted for publication in Astronomy & Astrophysic
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