5,559 research outputs found
Plasma reactor waste management systems
The University of North Dakota is developing a plasma reactor system for use in closed-loop processing that includes biological, materials, manufacturing, and waste processing. Direct-current, high-frequency, or microwave discharges will be used to produce plasmas for the treatment of materials. The plasma reactors offer several advantages over other systems, including low operating temperatures, low operating pressures, mechanical simplicity, and relatively safe operation. Human fecal material, sunflowers, oats, soybeans, and plastic were oxidized in a batch plasma reactor. Over 98 percent of the organic material was converted to gaseous products. The solids were then analyzed and a large amount of water and acid-soluble materials were detected. These materials could possibly be used as nutrients for biological systems
GMRT Low Frequency Observations of Extrasolar Planetary Systems
Extrasolar planets are expected to emit detectable low frequency radio
emission. In this paper we present results from new low frequency observations
of two extrasolar planetary systems (Epsilon Eridani and HD 128311) taken at
150 MHz with the Giant Metrewave Radio Telescope (GMRT). These two systems have
been chosen because the stars are young (with ages < 1 Gyr) and are likely to
have strong stellar winds, which will increase the expected radio flux. The
planets are massive (presumably) gas giant planets in longer period orbits, and
hence will not be tidally locked to their host star (as is likely to be the
case for short period planets) and we would expect them to have a strong
planetary dynamo and magnetic field. We do not detect either system, but are
able to place tight upper limits on their low frequency radio emission, at
levels comparable to the theoretical predictions for these systems. From these
observations we have a 2.5sigma limit of 7.8 mJy for Epsilon Eri and 15.5 mJy
for HD 128311. In addition, these upper limits also provide limits on the low
frequency radio emission from the stars themselves. These results are discussed
and also the prospects for the future detection of radio emission from
extrasolar planets.Comment: 6 pages, 2 figures, accepted for publication in MNRA
An extension of the dual magnetometer method for use on a dual spinning spacecraft
A method of estimating and correcting for the magnetic field of a dual spinning spacecraft has been developed by employing an extension of the dual magnetometer technique. This new method is useful for those situations in which a magnetometer boom of modest length is attached to the spinning part of a large spacecraft. The purpose of using a dual spinning spacecraft is to accommodate two types of instruments: imaging and similar pointed remote sensing systems on the stationary platform, and fields, particles and other in-situ measuring instruments on the spinning portion. The new method assumes that the stationary part of the spacecraft possesses a magnetic field which is represented by a combination of a dipole and a quadrupole field
From X-ray dips to eclipse: Witnessing disk reformation in the recurrent nova USco
The 10th recorded outburst of the recurrent eclipsing nova USco was observed
simultaneously in X-ray, UV, and optical by XMM-Newton on days 22.9 and 34.9
after outburst. Two full passages of the companion in front of the nova ejecta
were observed, witnessing the reformation of the accretion disk. On day 22.9,
we observed smooth eclipses in UV and optical but deep dips in the X-ray light
curve which disappeared by day 34.9, then yielding clean eclipses in all bands.
X-ray dips can be caused by clumpy absorbing material that intersects the line
of sight while moving along highly elliptical trajectories. Cold material from
the companion could explain the absence of dips in UV and optical light. The
disappearance of X-ray dips before day 34.9 implies significant progress in the
formation of the disk. The X-ray spectra contain photospheric continuum
emission plus strong emission lines, but no clear absorption lines. Both
continuum and emission lines in the X-ray spectra indicate a temperature
increase from day 22.9 to day 34.9. We find clear evidence in the spectra and
light curves for Thompson scattering of the photospheric emission from the
white dwarf. Photospheric absorption lines can be smeared out during scattering
in a plasma of fast electrons. We also find spectral signatures of resonant
line scattering that lead to the observation of the strong emission lines.
Their dominance could be a general phenomenon in high-inclination systems such
as Cal87.Comment: Submitted to ApJ. 16 pages, 16 figure
Exploring Information Technology Flexibility and Increased Complexity: Is Management Prepared?
Information technology (IT) flexibility has become a key enabler of increased IT effectiveness, towards improved IT-business alignment and sustained competitive advantage (Ness, 2005). However, as has been shown through this exploratory literature review, higher levels of IT flexibility also increase the level of complexity to be managed (Young, 2007; Rettig, 2007). Unfortunately, it was also found that management does not appear to be aware and/or prepared to manage the increased complexity (Wheatley, 2000; Lee, 2003), possibly resulting in more harm than good. This study are hoped to alert both IT and business management as to the opportunities existing within the area of IT flexibility, but also the risks involved if the resulting complexity level is not satisfactorily recognized and managed
Functionality in single-molecule devices: Model calculations and applications of the inelastic electron tunneling signal in molecular junctions
We analyze how functionality could be obtained within single-molecule devices
by using a combination of non-equilibrium Green's functions and ab-initio
calculations to study the inelastic transport properties of single-molecule
junctions. First we apply a full non-equilibrium Green's function technique to
a model system with electron-vibration coupling. We show that the features in
the inelastic electron tunneling spectra (IETS) of the molecular junctions are
virtually independent of the nature of the molecule-lead contacts. Since the
contacts are not easily reproducible from one device to another, this is a very
useful property. The IETS signal is much more robust versus modifications at
the contacts and hence can be used to build functional nanodevices. Second, we
consider a realistic model of a organic conjugated molecule. We use ab-initio
calculations to study how the vibronic properties of the molecule can be
controlled by an external electric field which acts as a gate voltage. The
control, through the gate voltage, of the vibron frequencies and (more
importantly) of the electron-vibron coupling enables the construction of
functionality: non-linear amplification and/or switching is obtained from the
IETS signal within a single-molecule device.Comment: Accepted for publication in Journal of Chemical Physic
Non-equilibrium inelastic electronic transport: Polarization effects and vertex corrections to the self-consistent Born approximation
We study the effect of electron-vibron interactions on the inelastic
transport properties of single-molecule nanojunctions. We use the
non-equilibrium Green's functions technique and a model Hamiltonian to
calculate the effects of second-order diagrams (double-exchange DX and
dressed-phonon DPH diagrams) on the electron-vibration interaction and consider
their effects across the full range of parameter space. The DX diagram,
corresponding to a vertex correction, introduces an effective dynamical
renormalization of the electron-vibron coupling in both the purely inelastic
and the inelastic-resonant features of the IETS. The purely inelastic features
correspond to an applied bias around the energy of a vibron, while the
inelastic-resonant features correspond to peaks (resonance) in the conductance.
The DPH diagram affects only the inelastic resonant features. We also discuss
the circumstances in which the second-order diagrams may be approximated in the
study of more complex model systems.Comment: To be published in PR
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