Cosmic dust in the atmosphere and in the interplanetary space at 1 AU today and in the early solar system

A description of techniques used in recent experiments to detect and analyze cosmic dust and micrometeorites is given and the results both from the study of lunar crater statistics and from in situ measurements are reviewed. The results from lunar crater statistics show an agreement with the results obtained from in situ measurements in interplanetary space and derived from zodiacal light measurements. The near earth results show an enhancement in the flux numbers. This can be caused either by secondary lunar debris or by disintegration of low density fireballs in the outer atmosphere

The role of organic polymers in the structure of cometary dust

Several phenomena observed in P/Halley and other comets indicate additional fragmentation of dust particles or dust aggregates in cometary atmospheres. The disintegration of dust aggregates may be explained by sublimation of polymerized formaldehyde - POM - which play a role as binding material between submicron individual particles

Particles from comet Kohoutek detected by the micrometeoroid experiment on HEOS 2

HEOS B measurements on particles ejected from comet Kohoutek reflect average particle rate as a function of particle speed and mass in relation to random distribution with known speed from the interplanetary region. The micrometeoroid experiment detector onboard the satellite passed through the orbital plane of the comet and encountered ejected particles for approximately two months

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

United States and Western Europe cooperation in planetary exploration

A framework was sought for U.S.-European cooperation in planetary exploration. Specific issues addressed include: types and levels of possible cooperative activities in the planetary sciences; specific or general scientific areas that seem most promising as the main focus of cooperative efforts; potential mission candidates for cooperative ventures; identification of special issues or problems for resolution by negotiation between the agencies, and possible suggestions for their resolutions; and identification of coordinated technological and instrumental developments for planetary missions

The influence of bicuspid aortic valves on the dynamic pressure distribution in the ascending aorta: a porcine ex vivo model †

OBJECTIVES The aim of the study was to simulate the effect of different bicuspid aortic valve configurations on the dynamic pressure distribution in the ascending aorta. METHODS Aortic specimens were harvested from adult domestic pigs. In Group 1, bicuspidalization was created by a running suture between the left and the right coronary leaflets (n = 6) and in Group 2 by a running suture between the left and the non-coronary leaflets (n = 6). Eleven tricuspid specimens served as controls. Two intraluminal pressure catheters were positioned at the concavity and the convexity of the ascending aorta. The specimens were connected to a mock circulation (heart rate: 60 bpm, target pressure: 95 mmHg). A comparison of the different conditions was also done in a numerical simulation. RESULTS At a distal mean aortic pressure of 94 ± 10 mmHg, a mean flow rate of 5.2 ± 0.3 l/min was achieved. The difference of maximal dynamic pressure values (which occurred in systole) between locations at the convexity and the concavity was 7.8 ± 2.9 mmHg for the bicuspid and 1.0 ± 0.9 mmHg for the tricuspid specimens (P < 0.001). The numerical simulation revealed an even higher pressure difference between convexity and concavity for bicuspid formation. CONCLUSIONS In this hydrodynamic mock circulation model, we were able to demonstrate that bicuspid aortic valves are associated with significant pressure differences in different locations within the ascending aorta compared with tricuspid aortic valves. These altered pressure distributions and flow patterns may further add to the understanding of aneurismal development in patients with bicuspid aortic valves and might serve to anticipate adverse aortic events due to a better knowledge of the underlying mechanism

Electromagnetic interferences from plasmas generated in meteoroids impacts

It is shown that the plasma, generated during an impact of a meteoroid with an artificial satellite, can produce electromagnetic radiation below the microwave frequency range. This interference is shown to exceed local noise sources and might disturb regular satellite operations.Comment: 6 pages, no figures. This version macthes the published versio

Orbital evolution under action of fast interstellar gas flow

Orbital evolution of an interplanetary dust particle under action of an interstellar gas flow is investigated. Secular time derivatives of the particle orbital elements, for arbitrary orbit orientation, are presented. An important result concerns secular evolution of semi-major axis. Secular semi-major axis of the particle on a bound orbit decreases under the action of fast interstellar gas flow. Possible types of evolution of other Keplerian orbital elements are discussed. The paper compares influences of the Poynting-Robertson effect, the radial solar wind and the interstellar gas flow on dynamics of the dust particle in outer planetary region of the Solar System and beyond it, up to 100 AU. Evolution of putative dust ring in the zone of the Edgeworth-Kuiper belt is studied. Also non-radial solar wind and gravitational effect of major planets may play an important role. Low inclination orbits of micron-sized dust particles in the belt are not stable due to fast increase of eccentricity caused by the interstellar gas flow and subsequent planetary perturbations - the increase of eccentricity leads to planet crossing orbits of the particles. Gravitational and non-gravitational effects are treated in a way which fully respects physics. As a consequence, some of the published results turned out to be incorrect. Moreover, the paper treats the problem in a more general way than it has been presented up to now. The influence of the fast interstellar neutral gas flow might not be ignored in modeling of evolution of dust particles beyond planets.Comment: 12 pages, 7 figure