47,015 research outputs found
Gas ion laser construction for electrically isolating the pressure gauge thereof
The valve and the pressure gauge of a gas ion laser were electrically insulated from the laser discharge path by connecting them in series with the cathode of the laser. The laser cathode can be grounded and preferably is a cold cathode although a hot cathode may be used instead. The cold cathode was provided with a central aperture to which was connected both the pressure gauge and the gas pressure reservoir through the valve. This will effectively prevent electric discharges from passing either to the pressure gauge or the valve which would otherwise destroy the pressure gauge
Modeling interannual variability in the Martian seasonal CO2 cycle
One aspect of the seasonal pressure variations measured at the Viking Lander sites is their nearly perfect interannual repeatability. This presents a problem because it implies that the behavior of the seasonal polar caps should be highly repeatable from year to year as well. There are a number of observations and theories suggesting that the presence of dust and water ice clouds in the Martian atmosphere should have significant direct and indirect effects on the rates of CO2 condensation and sublimation in the north and south polar regions. These effects include (1) reduced rates of CO2 frost condensation during polar night seasons due to the radiative effects of dust and water ice clouds and associated CO2 clouds or elevated atmospheric temperatures and (2) reduced or elevated rates of frost sublimation due to the radiative effects of atmospheric dust or to changes in frost emissivities and albedos due to contamination by water ice and dust. The Viking Landing pressure observations are examined to determine the range and character of the interannual variations present. Then a diurnal and seasonal thermal model is used to examine the effects of interannual variations in the polar heat balance on seasonal pressure variations
Recommended from our members
Developing a grid computing system for commercial-off-the-shelf simulation packages
Today simulation is becoming an increasingly
pervasive technology across major business
sectors. Advances in COTS Simulation Packages
and Commercial Simulation Software have made
it easier for users to build models, often of large complex processes. These two factors combined are to be welcomed and when used correctly can be of great benefit to organisations that make use of the technology. However, it is also the case
that users hungry for answers do not always have the time, or possibly the patience, to wait for results from multiple replications and multiple experiments as standard simulation practice would demand. There is therefore a need to support this advance in the use of simulation within todayâs business with improved computing technology. Grid computing has been put forward as a potential commercial solution to this requirement. To this end, Saker Solutions and the Distributed Systems Research Group at Brunel University have developed a dedicated Grid Computing System (SakerGrid) to support the deployment of simulation models across a desktop grid of PCs. The paper identifies route taken to solve this challenging issue and suggests where the future may lie for this exciting integration of two effective but underused technologies
Polar confinement of the Sun's interior magnetic field by laminar magnetostrophic flow
The global-scale interior magnetic field needed to account for the Sun's
observed differential rotation can be effective only if confined below the
convection zone in all latitudes, including the polar caps. Axisymmetric
nonlinear MHD solutions are obtained showing that such confinement can be
brought about by a very weak downwelling flow U~10^{-5}cm/s over each pole.
Such downwelling is consistent with the helioseismic evidence. All three
components of the magnetic field decay exponentially with altitude across a
thin "magnetic confinement layer" located at the bottom of the tachocline. With
realistic parameter values, the thickness of the confinement layer ~10^{-3} of
the Sun's radius. Alongside baroclinic effects and stable thermal
stratification, the solutions take into account the stable compositional
stratification of the helium settling layer, if present as in today's Sun, and
the small diffusivity of helium through hydrogen, chi. The small value of chi
relative to magnetic diffusivity produces a double boundary-layer structure in
which a "helium sublayer" of smaller vertical scale is sandwiched between the
top of the helium settling layer and the rest of the confinement layer.
Solutions are obtained using both semi-analytical and purely numerical,
finite-difference techniques. The confinement-layer flows are magnetostrophic
to excellent approximation. More precisely, the principal force balances are
between Lorentz, Coriolis, pressure-gradient and buoyancy forces, with relative
accelerations and viscous forces negligible. This is despite the kinematic
viscosity being somewhat greater than chi. We discuss how the confinement
layers at each pole might fit into a global dynamical picture of the solar
tachocline. That picture, in turn, suggests a new insight into the early Sun
and into the longstanding enigma of solar lithium depletion.Comment: Accepted by JFM. 36 pages, 10 figure
Fermentation Of Multigrain Dough â An Approach To Reduce Glycemic Index For Healthy Bread
The use of sourdough as the starter culture for bread making is one of the oldest processes in food fermentation and is very much prevalent in being used for the manufacture of various multigrain breads. The fermentation process of breads from mixed flours is one way, reported to reduce the glycemic index as compared to white bread. In this paper, we have discussed the use of (autochthonous) native culture vs pure culture use, in fermentation to prepare a starter culture sourdough by propagative fermentation. Since such a dough is incorporated in the sourdough bread making process (1:3), by the initial process of intermittent back-slopping (at intervals of 3.5 and 7 days) to propagate sourdough with a starter culture, as a part of the process, we observed the reduction in glycaemic index of the sourdough itself to as low as GI=40, at 3rd day of fermentation when the pure consortium and at 5th day of fermentation GI=43, when the native consortium was used. The sourdough process is thus an essential tool, aimed to make healthy breads, as it is incorporated as an ingredient in the process, to make sourdough bread
Photoionisation and Heating of a Supernova Driven, Turbulent, Interstellar Medium
The Diffuse Ionised Gas (DIG) in galaxies traces photoionisation feedback
from massive stars. Through three dimensional photoionisation simulations, we
study the propagation of ionising photons, photoionisation heating and the
resulting distribution of ionised and neutral gas within snapshots of
magnetohydrodynamic simulations of a supernova driven turbulent interstellar
medium. We also investigate the impact of non-photoionisation heating on
observed optical emission line ratios. Inclusion of a heating term which scales
less steeply with electron density than photoionisation is required to produce
diagnostic emission line ratios similar to those observed with the Wisconsin
H{\alpha} Mapper. Once such heating terms have been included, we are also able
to produce temperatures similar to those inferred from observations of the DIG,
with temperatures increasing to above 15000 K at heights |z| > 1 kpc. We find
that ionising photons travel through low density regions close to the midplane
of the simulations, while travelling through diffuse low density regions at
large heights. The majority of photons travel small distances (< 100pc);
however some travel kiloparsecs and ionise the DIG.Comment: 10 pages, 13 figures, accepted to MNRA
Drill/borescope System for the Mars Polar Pathfinder
The primary goals of the Mars Polar Pathfinder (MPP) Discovery Mission are to characterize the composition and structure of Mars' north polar ice cap, and to determine whether a climate record may be preserved in layers of ice and dust. The MPP would land as close as possible to the geographic north pole of Mars and use a set of instruments similar to those used by glaciologists to study polar ice caps on Earth: a radar sounder, a drill/borescope system, and a thermal probe. The drill/borescope system will drill approximately 50 cm into the surface and image the sides of the hole at 10 micron resolution for compositional and stratigraphic analysis. Several uncertainties have guided the development of this instrument, and they are discussed
- âŚ