The structure and evolution of Jupiter - The fluid contraction stage

1975 ◽  
Vol 199 ◽  
pp. 265 ◽  
Author(s):  
H. C., Jr. Graboske ◽  
R. J. Olness ◽  
J. B. Pollack ◽  
A. S. Grossman
Keyword(s):  
Contraction Stage

scholarly journals Galactic Distribution, Kinematics, Locations in Clusters and H-R Diagrams, and Duplicity of Be Stars (Review Paper)

1987 ◽  
Vol 92 ◽  
pp. 470-485 ◽  
Author(s):  
Helmut A. Abt
Keyword(s):  
Be Stars ◽  
Orbital Elements ◽  
Constant Frequency ◽  
B Stars ◽  
Star Catalogue ◽  
Solar Motion ◽  
Observational Techniques ◽  
Mass Functions ◽  
Galactic Distribution ◽  
Contraction Stage

AbstractThe locations of 143 B0e-B7e III-V stars listed in the Bright Star Catalogue are similar to those of the early-B Gould Belt stars. Therefore the Be stars have roughly the same ages and origins as early B stars. The frequency of runaway Be stars must be less than several percent. The radial velocities of Be stars show primarily the reflex of solar motion and show no evidence for systematically negative velocities attributable to mass-loss effects upon the absorption profiles. The scatter in the residual velocities is such that there is unlikely to be many undetected binaries with orbital amplitudes greater than 10 km s-l. We are unable to state whether or not Be stars tend to occur during the overall contraction stage, but we do observe Be stars in roughly constant frequency in clusters of all ages. About 18% of the field B0-B7 III-V stars are Be stars. Clusters show both lower and higher frequencies that may be real or may be due to different observational techniques. The frequencies and distribution of binary periods for Be stars is the same as for non-emission B stars except for the lack of periods less than 10-1 yr. Statistically the 12 classical Be stars with known orbital elements have mass functions indicating that their secondaries are more massive than neutron stars and their secondary mass distribution is like that of normal B stars. We observe 35 companions for 100 Be primaries, so after correction for undetected companions, it seems likely that most Be stars have companions, mostly with periods of years.

scholarly journals A Preliminary Note on the Pollen Development of Lathyrus Odoratus

1925 ◽  
Vol 2 (2) ◽  
pp. 199-209
Author(s):  
JOAN LATTER
Keyword(s):  
Nuclear Membrane ◽  
Pollen Development ◽  
Cell Walls ◽  
Crossing Over ◽  
Haploid Number ◽  
Preliminary Note ◽  
Homologous Chromosomes ◽  
Lathyrus Odoratus ◽  
Thread Formation ◽  
Contraction Stage

1. In this paper the main points in the pollen development of Lathyrus odoratus are briefly described. At the beginning of the meiotic phase the reticulum contracts from the nuclear membrane and exhibits an entirely granular appearance. 2. During thread formation, occasional amœboid nucleoli are observed. Nucleolar "budding" is also seen. 3. Connecting strands are constantly found between the synizetic knot and the nucleolus. 4. The thread at all stages appears usually to be a continuous structure. 5. The synizetic knot is followed by a stage in which the thread is thrown into seven definite loops which radiate out from the centre of the nucleus. For this stage, which has frequently been called the second contraction stage in cytological literature, the name broxonema is proposed. 6. The haploid number of chromosomes in Lathyrus odoratus is seven. Each loop represents one pair of homologous chromosomes joined distally end to end. 7. The arms of each loop are twisted round one another at one period. This affords opportunity for exchange of segments of chromosomes, and gives a possible physical basis for crossing over in a telosynaptic form. 8. These stages are followed by typical diakinesis and heterotypic divisions. 9. During homotypic telophase evanescent cell plates occur between the daughter nuclei. Later, the cell walls are formed by furrowing. 10. The tapetum remains uninucleate throughout.

Mode and determination of the initial contraction stage in the mouse embryo heart

2005 ◽  
Vol 211 (2) ◽  
pp. 95-100 ◽  
Author(s):  
Kiyomasa Nishii ◽  
Yosaburo Shibata
Keyword(s):  
Mouse Embryo ◽  
Embryo Heart ◽  
Contraction Stage

Die Casting Improvements through Melt Shear

2009 ◽  
Vol 618-619 ◽  
pp. 33-37 ◽  
Author(s):  
Robert G. O'Donnell ◽  
Dayalan R. Gunasegaram ◽  
Michel Givord
Keyword(s):  
Die Casting ◽  
Casting Process ◽  
Shrinkage Porosity ◽  
Thermal Gradients ◽  
Casting Defects ◽  
Melt Flow ◽  
Complex Process ◽  
Casting Cycle ◽  
Die Casting Process ◽  
Contraction Stage

Melt flow and solidification within a die casting cavity is a complex process dependent in part on melt pressure (with or without intensification), melt velocity, melt flow path, thermal gradients within the die, die lubrication and melt viscosity. Casting defects such as short shots, cold shuts and shrinkage porosity can readily occur if casting conditions are not optimised. Shrinkage porosity in particular is difficult to eradicate from castings that comprise thick sections, since these sections will usually solidify late in the casting cycle and may be starved of melt supply during the critical solidification (and contraction) stage. The current work seeks to elucidate the influence of the melt shearing on the die casting process and demonstrates that the modifications made to the melt through introduction of a local constriction in the melt path can generate improvements in casting microstructure and reduce shrinkage porosity.

Numerical and Experimental Study of Bubble Impact on a Solid Wall

2015 ◽  
Vol 137 (3) ◽  
Author(s):  
B. Y. Ni ◽  
A. M. Zhang ◽  
G. X. Wu
Keyword(s):  
High Speed ◽  
Bubble Dynamics ◽  
Velocity Potential ◽  
Solid Wall ◽  
Rigid Wall ◽  
Rigid Surface ◽  
Severe Damage ◽  
Convergence Study ◽  
Numerical Difficulty ◽  
Contraction Stage

The dynamic characteristics of a bubble initially very close to a rigid wall, or with a very narrow gap, are different from those of a bubble away from the wall. Especially at the contraction stage, a high-speed jet pointing toward the wall will be generated and will impact the rigid surface directly, which could cause more severe damage to the structure. Based on the velocity potential theory and boundary element method (BEM), the present paper aims to overcome the numerical difficulty and simulate the bubble impact on a solid wall for the axisymmetric case. The convergence study has been undertaken to verify the developed numerical method and the computation code. Extensive experiments are conducted. Case studies are made using both experimental data and numerical results. The effects of dimensionless distance on the bubble dynamics are investigated.

Meiotic events in Oenothera — a non-standard pattern of chromosome behaviour

Genome ◽  
2008 ◽  
Vol 51 (11) ◽  
pp. 952-958 ◽  
Author(s):  
Hieronim Golczyk ◽  
Krystyna Musiał ◽  
Uwe Rauwolf ◽  
Jörg Meurer ◽  
Reinhold G. Herrmann ◽  
...  
Keyword(s):  
Degree Of Polarization ◽  
Chromosome Behaviour ◽  
High Complexity ◽  
Standard Pattern ◽  
Reciprocal Translocations ◽  
Chromosome Configuration ◽  
Long Period ◽  
Translocation Heterozygosity ◽  
High Degree ◽  
Contraction Stage

The genus Oenothera shows an intriguing extent of permanent translocation heterozygosity. Reciprocal translocations of chromosome arms in species or populations result in various kinds of chromosome multivalents in diakinesis. Early meiotic events conditioning such chromosome behaviour are poorly understood. We found a surprising uniformity of the leptotene–diplotene period, regardless of the chromosome configuration at diakinesis (ring of 14, 7 bivalents, mixture of bivalents and multivalents). It appears that the earliest chromosome interactions at Oenothera meiosis are untypical, since they involve pericentromeric regions. During early leptotene, proximal chromosome parts cluster and form a highly polarized Rabl configuration. Telomeres associated in pairs were seen at zygotene. The high degree of polarization of meiotic nuclei continues for an exceptionally long period, i.e., during zygotene–pachytene into the diplotene contraction stage. The Rabl-polarized meiotic architecture and clustering of pericentromeres suggest a high complexity of karyotypes, not only in structural heterozygotes but also in bivalent-forming homozygous species.

scholarly journals A STUDY OF MYOFIBRIL SARCOMERE STRUCTURE DURING CONTRACTION

1962 ◽  
Vol 12 (1) ◽  
pp. 135-147 ◽  
Author(s):  
Vladimir P. Gilëv
Keyword(s):  
Electron Microscope ◽  
Striated Muscle ◽  
Muscle Fibers ◽  
Field Of Vision ◽  
Strong Contraction ◽  
Striated Muscle Fibers ◽  
Last Stage ◽  
Contraction Stage

In the present investigation of cross-striated muscle fibers of axolotl, we succeeded in observing in one field of vision of the electron microscope all the stages of myofibril contraction. This allowed us to avoid errors in establishing the sequence of individual contraction stages. Our studies reveal a new contraction stage which appears at the shortening of the sarcomere below 74 per cent of the "resting length" but prior to the formation of typical "maximally shortened" sarcomeres, characterized by strong "contraction bands." At this stage, in the center of the sarcomere, at either side of the M line, a "secondary anisotropic" band arises which widens with further sarcomere contraction. At either side of this band, at the place of the former ("primary") anisotropic band, a "secondary isotropic" band is formed. A scheme of successive stages of contraction of the sarcomere is presented. The mechanisms of contraction for the first stage (from 100 to 79 per cent of the "resting length") and for the last stage (from 74 to 58 per cent of the "resting length") seem to be different. While the sliding of myofilaments with respect to one another can be assumed for the first stage, it is the spiralization of these structures which is the most likely explanation for the last stage. (An Abstract in German also appears at the end of this article.)

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