670 research outputs found
Anticipated results from dust experiments on cometary missions
The major scientific objectives of a mission are: to determine the chemical nature and physical structure of comet nuclei, and to characterize the changes that occur as a function of time orbital position; to characterize the chemical and physical nature of the atmospheres and ionospheres of comets as well as the processes that occur in them, and to characterize the development of the atmospheres and ionospheres as functions of time and orbital position; and to determine the nature of comet tails and processes by which they are formed, and to characterize the interaction of comets with the solar wind. Since dust is a major constituent of a comet, the achievement of these goals requires the intensive study of the paticulate emission from a comet
Future European Ground Segment
lhe existing European ground infrastructure is capable to support earth observation satellites, the present ARIANE program and scientific manned spaceflight missions as demonstrated during the first German Spacelab D 1 mission flown as payload onboard NSTS in October 85.
Future European space program like EURECA, COLUMBUS, HERMES, ARIANE 5, DRS and scientifi~ satellites will require a ground based end-to-end o~eration and verification infrastructure (GEOVI) of a new order of magnitude.
Individual program needs and required user support ground segments exceed the very tight budgetary frame available for the European space com~unity (agencies and i ndust.ry) . Investments are\u27 necessary for i ndust ri a 1 development faci- 1 iti es to ~upport the AIV phase, support facilities for development and operation, launch and landing facilities operation~ facilities for mission and payload control and payload data facilities for data dissemination, archiving, retrieval etc
Debris and micrometeorite impact measurements in the laboratory
A method was developed to simulate space debris in the laboratory. This method, which is an outgrowth of research in inertial confinement fusion (ICF), uses laser ablation to accelerate material. Using this method, single 60 micron aluminum spheres were accelerated to 15 km/sec and larger 500 micron aluminum spheres were accelerated to 2 km/sec. Also, many small (less than 10 micron diameter) irregularly shaped particles were accelerated to speeds of 100 km/sec
Integrable atomtronic interferometry
High sensitivity quantum interferometry requires more than just access to
entangled states. It is achieved through deep understanding of quantum
correlations in a system. Integrable models offer the framework to develop this
understanding. We communicate the design of interferometric protocols for an
integrable model that describes the interaction of bosons in a four-site
configuration. Analytic formulae for the quantum dynamics of certain
observables are computed. These expose the system's functionality as both an
interferometric identifier, and producer, of NOON states. Being equivalent to a
controlled-phase gate acting on two hybrid qudits, this system also highlights
an equivalence between Heisenberg-limited interferometry and quantum
information. These results are expected to open new avenues for
integrability-enhanced atomtronic technologies.Comment: 6 pages, 4 figures, 1 tabl
Perspectives on Interstellar Dust Inside and Outside of the Heliosphere
Measurements by dust detectors on interplanetary spacecraft appear to
indicate a substantial flux of interstellar particles with masses exceeding
10^{-12}gram. The reported abundance of these massive grains cannot be typical
of interstellar gas: it is incompatible with both interstellar elemental
abundances and the observed extinction properties of the interstellar dust
population. We discuss the likelihood that the Solar System is by chance
located near an unusual concentration of massive grains and conclude that this
is unlikely, unless dynamical processes in the ISM are responsible for such
concentrations. Radiation pressure might conceivably drive large grains into
"magnetic valleys". If the influx direction of interstellar gas and dust is
varying on a ~10 yr timescale, as suggested by some observations, this would
have dramatic implications for the small-scale structure of the interstellar
medium.Comment: 13 pages. To appear in Space Science Review
The Cosmic Infrared Background at 1.25 microns and 2.2 microns using DIRBE and 2MASS: a contribution not due to galaxies ?
Using the 2MASS 2nd Incremental Data Release and the Zodiacal-Subtracted
Mission Average maps of COBE/DIRBE, we estimate the cosmic background in the J
(1.25 micron) and K (2.2 microns) bands using selected areas representing 550
square degrees of sky. We find a J background of 22.9 \pm 7.0 kJy/sr (54.0 \pm
16.8 nW/m2/sr) and a K background of 20.4 \pm 4.9 kJy/sr (27.8 \pm 6.7
nW/m2/sr). This large scale study shows that the main uncertainty comes from
the residual zodiacal emission. The cosmic background we obtain is
significantly higher than integrated galaxy counts (3.6 \pm 0.8 kJy/sr and 5.3
\pm 1.2 kJy/sr for J and K, respectively), suggesting either an increase of the
galaxy luminosity function for magnitudes fainter than 30 or the existence of
another contribution to the cosmic background from primeval stars, black holes,
or relic particle decay.Comment: 20 pages, 6 figures, accepted in Ap
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Combined transcriptomic-(1)H NMR metabonomic study reveals yhat monoethylhexyl phthalate stimulates adipogenesis and glyceroneogenesis in human adipocytes
Adipose tissue is a major storage site for lipophilic environmental contaminants. The environmental metabolic disruptor hypothesis postulates that some pollutants can promote obesity or metabolic disorders by activating nuclear receptors involved in the control of energetic homeostasis. In this context, monoethylhexyl phthalate (MEHP) is of particular concern since it was shown to activate the peroxisome proliferator-activated receptor Ī³ (PPARĪ³) in 3T3-L1 murine preadipocytes. In the present work, we used an untargeted, combined transcriptomic-(1)H NMR-based metabonomic approach to describe the overall effect of MEHP on primary cultures of human subcutaneous adipocytes differentiated in vitro. MEHP stimulated rapidly and selectively the expression of genes involved in glyceroneogenesis, enhanced the expression of the cytosolic phosphoenolpyruvate carboxykinase, and reduced fatty acid release. These results demonstrate that MEHP increased glyceroneogenesis and fatty acid reesterification in human adipocytes. A longer treatment with MEHP induced the expression of genes involved in triglycerides uptake, synthesis, and storage; decreased intracellular lactate, glutamine, and other amino acids; increased aspartate and NAD, and resulted in a global increase in triglycerides. Altogether, these results indicate that MEHP promoted the differentiation of human preadipocytes to adipocytes. These mechanisms might contribute to the suspected obesogenic effect of MEHP
The COBE Diffuse Infrared Background Experiment Search for the Cosmic Infrared Background: IV. Cosmological Implications
In this paper we examine the cosmological constraints of the recent DIRBE and
FIRAS detection of the extragalactic background light between 125-5000 microns
on the metal and star formation histories of the universe.Comment: 38 pages and 9 figures. Accepted for publications in The
Astrophysical Journa
Well posedness of an isothermal diffusive model for binary mixtures of incompressible fluids
We consider a model describing the behavior of a mixture of two
incompressible fluids with the same density in isothermal conditions. The model
consists of three balance equations: continuity equation, Navier-Stokes
equation for the mean velocity of the mixture, and diffusion equation
(Cahn-Hilliard equation). We assume that the chemical potential depends upon
the velocity of the mixture in such a way that an increase of the velocity
improves the miscibility of the mixture. We examine the thermodynamic
consistence of the model which leads to the introduction of an additional
constitutive force in the motion equation. Then, we prove existence and
uniqueness of the solution of the resulting differential problem
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