On the momentum balance along the Comet Halley — Sun line during the Giotto flyby

1993 ◽  
Vol 98 (A9) ◽  
pp. 15255 ◽  
Author(s):  
P. L. Israelevich ◽  
F. M. Neubauer ◽  
A. I. Ershkovich
Keyword(s):  
Momentum Balance ◽  
Comet Halley

Hydrogen Cyanide Polymers from the Impact of Comet P/Shoemaker-Levy 9 on Jupiter

1997 ◽  
Vol 161 ◽  
pp. 179-187
Author(s):  
Clifford N. Matthews ◽  
Rose A. Pesce-Rodriguez ◽  
Shirley A. Liebman
Keyword(s):  
Amino Acids ◽  
Solar System ◽  
Hydrogen Cyanide ◽  
Nitrogen Heterocycles ◽  
Laboratory Studies ◽  
Heterogeneous Solids ◽  
The Many ◽  
Comet Halley ◽  
The Impact ◽  
By Products

AbstractHydrogen cyanide polymers – heterogeneous solids ranging in color from yellow to orange to brown to black – may be among the organic macromolecules most readily formed within the Solar System. The non-volatile black crust of comet Halley, for example, as well as the extensive orangebrown streaks in the atmosphere of Jupiter, might consist largely of such polymers synthesized from HCN formed by photolysis of methane and ammonia, the color observed depending on the concentration of HCN involved. Laboratory studies of these ubiquitous compounds point to the presence of polyamidine structures synthesized directly from hydrogen cyanide. These would be converted by water to polypeptides which can be further hydrolyzed to α-amino acids. Black polymers and multimers with conjugated ladder structures derived from HCN could also be formed and might well be the source of the many nitrogen heterocycles, adenine included, observed after pyrolysis. The dark brown color arising from the impacts of comet P/Shoemaker-Levy 9 on Jupiter might therefore be mainly caused by the presence of HCN polymers, whether originally present, deposited by the impactor or synthesized directly from HCN. Spectroscopic detection of these predicted macromolecules and their hydrolytic and pyrolytic by-products would strengthen significantly the hypothesis that cyanide polymerization is a preferred pathway for prebiotic and extraterrestrial chemistry.

Analysis of shear bands in slow granular flows using a frictional Cosserat model

2000 ◽  
Vol 627 ◽  
Author(s):  
Prabhu R. Nott ◽  
K. Kesava Rao ◽  
L. Srinivasa Mohan
Keyword(s):  
Scaling Laws ◽  
Shear Bands ◽  
Shear Layers ◽  
Theoretical Description ◽  
Field Variable ◽  
Cosserat Continuum ◽  
Momentum Balance ◽  
Rigid Plastic ◽  
Independent Field ◽  
Cosserat Model

ABSTRACTThe slow flow of granular materials is often marked by the existence of narrow shear layers, adjacent to large regions that suffer little or no deformation. This behaviour, in the regime where shear stress is generated primarily by the frictional interactions between grains, has so far eluded theoretical description. In this paper, we present a rigid-plastic frictional Cosserat model that captures thin shear layers by incorporating a microscopic length scale. We treat the granular medium as a Cosserat continuum, which allows the existence of localised couple stresses and, therefore, the possibility of an asymmetric stress tensor. In addition, the local rotation is an independent field variable and is not necessarily equal to the vorticity. The angular momentum balance, which is implicitly satisfied for a classical continuum, must now be solved in conjunction with the linear momentum balances. We extend the critical state model, used in soil plasticity, for a Cosserat continuum and obtain predictions for flow in plane and cylindrical Couette devices. The velocity profile predicted by our model is in qualitative agreement with available experimental data. In addition, our model can predict scaling laws for the shear layer thickness as a function of the Couette gap, which must be verified in future experiments. Most significantly, our model can determine the velocity field in viscometric flows, which classical plasticity-based model cannot.

Ice Plasma Wave Measurements in the Ion Pick-Up Region of Comet Halley

2013 ◽  
pp. 857-860
Author(s):  
F.L. Scarf ◽  
F.V. Coroniti ◽  
C.F. Kennel ◽  
T.R. Sanderson ◽  
K-P Wenzel ◽  
...  
Keyword(s):  
Plasma Wave ◽  
Wave Measurements ◽  
Comet Halley

Observation of comet Halley by the ultraviolet imager of Suisei

Nature ◽  
1986 ◽  
Vol 321 (S6067) ◽  
pp. 297-299 ◽  
Author(s):  
E. Kaneda ◽  
O. Ashihara ◽  
M. Shimizu ◽  
M. Takagi ◽  
K. Hirao
Keyword(s):  
Comet Halley

scholarly journals Advanced Constitutive Modeling of the Thixotropic Elasto-Visco-Plastic Behavior of Blood: Steady-State Blood Flow in Microtubes

Materials ◽  
2021 ◽  
Vol 14 (2) ◽  
pp. 367
Author(s):  
Konstantinos Giannokostas ◽  
Yannis Dimakopoulos ◽  
Andreas Anayiotos ◽  
John Tsamopoulos
Keyword(s):  
Blood Flow ◽  
Steady State ◽  
Constitutive Model ◽  
Blood Plasma ◽  
Constitutive Modeling ◽  
Flow Direction ◽  
Momentum Balance ◽  
Plastic Behavior ◽  
Flow Investigation ◽  
The Impact

The present work focuses on the in-silico investigation of the steady-state blood flow in straight microtubes, incorporating advanced constitutive modeling for human blood and blood plasma. The blood constitutive model accounts for the interplay between thixotropy and elasto-visco-plasticity via a scalar variable that describes the level of the local blood structure at any instance. The constitutive model is enhanced by the non-Newtonian modeling of the plasma phase, which features bulk viscoelasticity. Incorporating microcirculation phenomena such as the cell-free layer (CFL) formation or the Fåhraeus and the Fåhraeus-Lindqvist effects is an indispensable part of the blood flow investigation. The coupling between them and the momentum balance is achieved through correlations based on experimental observations. Notably, we propose a new simplified form for the dependence of the apparent viscosity on the hematocrit that predicts the CFL thickness correctly. Our investigation focuses on the impact of the microtube diameter and the pressure-gradient on velocity profiles, normal and shear viscoelastic stresses, and thixotropic properties. We demonstrate the microstructural configuration of blood in steady-state conditions, revealing that blood is highly aggregated in narrow tubes, promoting a flat velocity profile. Additionally, the proper accounting of the CFL thickness shows that for narrow microtubes, the reduction of discharged hematocrit is significant, which in some cases is up to 70%. At high pressure-gradients, the plasmatic proteins in both regions are extended in the flow direction, developing large axial normal stresses, which are more significant in the core region. We also provide normal stress predictions at both the blood/plasma interface (INS) and the tube wall (WNS), which are difficult to measure experimentally. Both decrease with the tube radius; however, they exhibit significant differences in magnitude and type of variation. INS varies linearly from 4.5 to 2 Pa, while WNS exhibits an exponential decrease taking values from 50 mPa to zero.

The Comet Halley flyby I.R. sounder “I.K.S.”

1982 ◽  
Vol 2 (4) ◽  
pp. 113-122 ◽  
Author(s):  
M. Arduini ◽  
S. Cazes ◽  
J.F. Crifo ◽  
R. Gispert ◽  
D. Harduin ◽  
...  
Keyword(s):  
Comet Halley

Earth-based observations of Comet Halley dust and gas

1987 ◽  
Vol 323 (1572) ◽  
pp. 369-379
Keyword(s):  
Comet Halley

Very extensive ground-based observations of P/Halley have now been made, both to provide a standard cometary archive and to help interpret data from the Halley space probes. A number of new results are reported here, of which the most important is probably the major role played by sporadic activity of the nucleus in the development of the comet.

A model for intensity profiles of dust jets near the nucleus of comet Halley

Icarus ◽  
1988 ◽  
Vol 76 (1) ◽  
pp. 78-88 ◽  
Author(s):  
W.F. Huebner ◽  
D.C. Boice ◽  
H.J. Reitsema ◽  
W.A. Delamere ◽  
F.L. Whipple
Keyword(s):  
Comet Halley

Detection of a new “chemical” boundary at comet Halley

1986 ◽  
Vol 13 (7) ◽  
pp. 613-616 ◽  
Author(s):  
K. I. Gringauz ◽  
T. I. Gombosi ◽  
M. Tátrallyay ◽  
M. I. Verigin ◽  
A. P. Remizov ◽  
...  
Keyword(s):  
Comet Halley
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