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排序方式: 共有240条查询结果,搜索用时 31 毫秒
141.
Dehant Veronique Debaille Vinciane Dobos Vera Gaillard Fabrice Gillmann Cedric Goderis Steven Grenfell John Lee Höning Dennis Javaux Emmanuelle J. Karatekin Özgür Morbidelli Alessandro Noack Lena Rauer Heike Scherf Manuel Spohn Tilman Tackley Paul Van Hoolst Tim Wünnemann Kai 《Space Science Reviews》2019,215(6):1-48
Space Science Reviews - This paper reviews habitability conditions for a terrestrial planet from the point of view of geosciences. It addresses how interactions between the interior of a planet or... 相似文献
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144.
Marc Studer Gesine Bradacs Andre Hilliger Eva Hürlimann Stephanie Engeli Cora S. Thiel Peter Zeitner Beat Denier Markus Binggeli Thomas Syburra Marcel Egli Frank Engelmann Oliver Ullrich 《Acta Astronautica》2011,68(11-12):1729-1741
Long-term sensitivity of human cells to reduced gravity has been supposed since the first Apollo missions and was demonstrated during several space missions in the past. However, little information is available on primary and rapid gravi-responsive elements in mammalian cells. In search of rapid-responsive molecular alterations in mammalian cells, short-term microgravity provided by parabolic flight maneuvers is an ideal way to elucidate such initial and primary effects. Modern biomedical research at the cellular and molecular level requires frequent repetition of experiments that are usually performed in sequences of experiments and analyses. Therefore, a research platform on Earth providing frequent, easy and repeated access to real microgravity for cell culture experiments is strongly desired. For this reason, we developed a research platform onboard the military fighter jet aircraft Northrop F-5E “Tiger II”. The experimental system consists of a programmable and automatically operated system composed of six individual experiment modules, placed in the front compartment, which work completely independent of the aircraft systems. Signal transduction pathways in cultured human cells can be investigated after the addition of an activator solution at the onset of microgravity and a fixative or lysis buffer after termination of microgravity. Before the beginning of a regular military training flight, a parabolic maneuver was executed. After a 1 g control phase, the parabolic maneuver starts at 13,000 ft and at Mach 0.99 airspeed, where a 22 s climb with an acceleration of 2.5g is initiated, following a free-fall ballistic Keplerian trajectory lasting 45 s with an apogee of 27,000 ft at Mach 0.4 airspeed. Temperature, pressure and acceleration are monitored constantly during the entire flight. Cells and activator solutions are kept at 37 °C during the entire experiment until the fixative has been added. The parabolic flight profile provides up to 45 s of microgravity at a quality of 0.05g in all axes. Access time is 30 min before take-off; retrieval time is 30 min after landing. We conclude that using military fighter jets for microgravity research is a valuable tool for frequent and repeated cell culture experiments and therefore for state-of-the art method of biomedical research. 相似文献
145.
Mann Ingrid Kimura Hiroshi Biesecker Douglas A. Tsurutani Bruce T. Grün Eberhard McKibben R. Bruce Liou Jer-Chyi MacQueen Robert M. Mukai Tadashi Guhathakurta Madhulika Lamy Philippe 《Space Science Reviews》2004,110(3-4):269-305
We review the current knowledge and understanding of dust in the inner solar system. The major sources of the dust population in the inner solar system are comets and asteroids, but the relative contributions of these sources are not quantified. The production processes inward from 1 AU are: Poynting-Robertson deceleration of particles outside of 1 AU, fragmentation into dust due to particle-particle collisions, and direct dust production from comets. The loss processes are: dust collisional fragmentation, sublimation, radiation pressure acceleration, sputtering, and rotational bursting. These loss processes as well as dust surface processes release dust compounds in the ambient interplanetary medium. Between 1 and 0.1 AU the dust number densities and fluxes can be described by inward extrapolation of 1 AU measurements, assuming radial dependences that describe particles in close to circular orbits. Observations have confirmed the general accuracy of these assumptions for regions within 30° latitude of the ecliptic plane. The dust densities are considerably lower above the solar poles but Lorentz forces can lift particles of sizes < 5 μm to high latitudes and produce a random distribution of small grains that varies with the solar magnetic field. Also long-period comets are a source of out-of-ecliptic particles. Under present conditions no prominent dust ring exists near the Sun. We discuss the recent observations of sungrazing comets. Future in-situ experiments should measure the complex dynamics of small dust particles, identify the contribution of cometary dust to the inner-solar-system dust cloud, and determine dust interactions in the ambient interplanetary medium. The combination of in-situ dust measurements with particle and field measurements is recommended. 相似文献
146.
ISO performed a large variety of observing programmes on comets, asteroids and zodiacal light – covering about 1% of the archived
observations – with a surprisingly rewarding scientific return. Outstanding results were related to the exceptionally bright
comet Hale–Bopp and to ISO's capability to study in detail the water spectrum in a direct way. But many other results were
broadly recognised: Discovery of new molecules in comets, the studies of crystalline silicates, the work on asteroid surface
mineralogy, results from thermophysical studies of asteroids, a new determination of the asteroid number density in the main-belt
and last but not least, the investigations on the spatial and spectral features of the zodiacal light. 相似文献
147.
Continuous direct records of solar variability are limited to the telescopic era covering approximately the past four centuries. For longer records one has to rely on indirect indices such as cosmogenic radionuclides. Their production rate is modulated by magnetic properties of the solar wind. Using a parameterisation of the solar activity and a Monte Carlo simulation model describing the interaction of the cosmic rays with the atmosphere, the production rate for each cosmogenic nuclide of interest can be calculated as a function of solar activity. Analysis of appropriate well-dated natural archives such as ice cores or tree rings offers the possibility to reconstruct the solar activity over many millennia. However, the interpretation of the cosmogenic nuclide records from these archives is difficult. The measured concentrations contain not only information on solar activity but also on changes in the geomagnetic field intensity and the transport from the atmosphere into the archive where, under ideal conditions, no further processes take place. Comparison of different nuclides (e.g. 10Be and 14C) that are produced in a very similar way but exhibit a completely different geochemical behaviour, allows us to separate production effects from system effects.The presently available data show cyclic variability ranging from 11-year to millennial time scale periodicities with changing amplitudes, as well as irregularly distributed intervals of very low solar activity (so called minima, e.g. Maunder minimum) lasting typically 100 years. 相似文献
148.
Harald Krüger Markus Landgraf Nicolas Altobelli Eberhard Grün 《Space Science Reviews》2007,130(1-4):401-408
The Ulysses spacecraft has been orbiting the Sun on a highly inclined ellipse almost perpendicular to the ecliptic plane (inclination
79°, perihelion distance 1.3 AU, aphelion distance 5.4 AU) since it encountered Jupiter in 1992. The in situ dust detector
on board continuously measured interstellar dust grains with masses up to 10−13 kg, penetrating deep into the solar system. The flow direction is close to the mean apex of the Sun’s motion through the
solar system and the grains act as tracers of the physical conditions in the local interstellar cloud (LIC). While Ulysses
monitored the interstellar dust stream at high ecliptic latitudes between 3 and 5 AU, interstellar impactors were also measured
with the in situ dust detectors on board Cassini, Galileo and Helios, covering a heliocentric distance range between 0.3 and
3 AU in the ecliptic plane. The interstellar dust stream in the inner solar system is altered by the solar radiation pressure
force, gravitational focussing and interaction of charged grains with the time varying interplanetary magnetic field. We review
the results from in situ interstellar dust measurements in the solar system and present Ulysses’ latest interstellar dust
data. These data indicate a 30° shift in the impact direction of interstellar grains w.r.t. the interstellar helium flow direction,
the reason of which is presently unknown. 相似文献
149.
G. Klingelhöfer J. Brückner C. D’uston R. Gellert R. Rieder 《Space Science Reviews》2007,128(1-4):383-396
The Alpha Particle X-Ray Spectrometer (APXS) is a small instrument to determine the elemental composition of a given sample.
For the ESA Rosetta mission, the periodical comet 67P/Churyumov-Gerasimenko was selected as the target comet, where the lander
PHILAE (after landing) will carry out in-situ observations. One of the instruments onboard is the APXS to make measurements
on the landing site. The APXS science goal is to provide basic compositional data of the comet surface. As comets consist
of a mixture of ice and dust, the dust component can be characterized and compared with known meteoritic compositions. Various
element ratios can be used to evaluate whether chemical fractionations occurred in cometary material by comparing them with
known chondritic material. To enable observations of the local environment, APXS measurements of several spots on the surface
and one spot as function of temperature can be made. Repetitive measurements as function of heliocentric distance can elucidate
thermal processes at work. By measuring samples that were obtained by drilling subsurface material can be analyzed. The accumulated
APXS data can be used to shed light on state, evolution, and origin of 67P/Churyumov- Gerasimenko. 相似文献
150.
K. Scherer H. Fichtner T. Borrmann J. Beer L. Desorgher E. Flükiger H.-J. Fahr S. E. S. Ferreira U. W. Langner M. S. Potgieter B. Heber J. Masarik N. Shaviv J. Veizer 《Space Science Reviews》2006,127(1-4):467-465
In recent years the variability of the cosmic ray flux has become one of the main issues interpreting cosmogenic elements
and especially their connection with climate. In this review, an interdisciplinary team of scientists brings together our
knowledge of the evolution and modulation of the cosmic ray flux from its origin in the Milky Way, during its propagation
through the heliosphere, up to its interaction with the Earth’s magnetosphere, resulting, finally, in the production of cosmogenic
isotopes in the Earth’ atmosphere. The interpretation of the cosmogenic isotopes and the cosmic ray – cloud connection are
also intensively discussed. Finally, we discuss some open questions. 相似文献