Hydrolithosphere and Problems of Subsurface Ice in the Equatorial Zone of Mars

1985 ◽  
pp. 607-617 ◽  
Author(s):  
Battistini René
Keyword(s):  
Equatorial Zone

A centrosome-associated antibody from Drosophila melanogaster reveals a new microtubule-dependent structure in the equatorial zone of Parascaris univalens embryos

1993 ◽  
Vol 106 (3) ◽  
pp. 719-730
Author(s):  
M. Jimenez ◽  
C. Goday
Keyword(s):  
Drosophila Melanogaster ◽  
Cytochalasin B ◽  
Cell Communication ◽  
Equatorial Zone ◽  
Contractile Ring ◽  
Daughter Cells ◽  
Ring Assembly ◽  
Single Body ◽  
A Cell ◽  
Cycle Dependent

The distribution of antigens to two antibodies (Bx63 and Rb188) that associate to Drosophila melanogaster centrosomes has been investigated in the nematode Parascaris. By western blot analysis both antibodies identify in Parascaris polypeptides of the same molecular mass as in Drosophila (Rb188 a 185 kDa antigen and Bx63 185 kDa and 66 kDa antigens). By immunocytochemistry we show that the centrosomes of Parascaris contain the 185 kDa antigen recognized by polyclonal Rb188 and monoclonal Bx63 antibodies. In addition, Bx63 reveals cytoplasmic midzone structures, not found in Drosophila, that display a cell cycle-dependent organization in embryos. These structures, which most probably contain the 66 kDa antigen revealed by Bx63, appear at the onset of anaphase as fibrillar-like structures that during anaphase form a ring-like structure encircling the equatorial plane of the blastomere. Before furrowing, the antigen participates in the formation of the midbody and associates with convergent polar microtubules. After blastomere division, Bx63 signal persists as a single body between the daughter cells. The analysis of chilled and nocodazole-treated embryos suggests that the localization of the midzone Bx63 antigen is dependent on non-kinetochore microtubules. Inhibition of furrowing by cytochalasin B shows that the antigen persists after the disassembly of microfilaments. Cytological observations of contractile ring and Bx63 ring assembly indicate that both structures do not simultaneously colocalize at the equatorial zone. The data suggest a spindle-dependent distribution of the Bx63 antigen during cytokinesis. We discuss the participation of this antigen in the organization of the midbody before furrowing, and consider the possible relevance of the midbody with respect to cell to cell communication during early development in nematodes.

scholarly journals Analysis of the FK5 System in the Equatorial Zone

1995 ◽  
Vol 166 ◽  
pp. 382-382
Author(s):  
Yu.B. Kolesnik
Keyword(s):  
Equatorial Zone ◽  
Motion System ◽  
Area Distribution ◽  
The Sixties ◽  
Hipparcos Catalogue ◽  
The Mean ◽  
The Absolute ◽  
The Individual ◽  
Right Ascension ◽  
Selection Of

15 catalogues produced in the eighties and 12 catalogues of the sixties-seventies have been used to assess the consistency of the FK5 system with observations in the declination zone from −30° to 30°. Positions of the FK4-based catalogues have been transformed at the equinox and equator J2000.0. Classical δ-dependent and α-dependent systematic differences (Cat-FK5) have been formed for individual instrumental systems of the catalogues by a method close to the classical Numerical Method. The weighted mean instrumental systems for the two subsets of catalogues centered at the epochs 1970 (MIS 60–70) and 1987 (MIS 80) and for all types of systematic differences have been constructed. The mean errors of the total systematic differences in α and δ have been estimated as 14 mas and 21 mas, respectively, for the catalogues of the 60-70ies, and 10 mas in both α and δ for the catalogues of the 80ies.It has been found that the mutual consistency of individual instrumental systems of catalogues of the 80ies with respect to δ-dependent systematic differences is superior by the factor 1.5 comparing with the catalogues of 60-70ies, while the consistency of both catalogue selections with respect to α-dependent systematic differences is comparable. Random accuracy of the FK5 positions and proper motions at the epochs under analysis has been assessed as close to expected from the formal considerations. Actual systematic discrepancies of the FK5 with observations at the respective epochs have been detected. For systematic differences δαδ cosδ and δδδ, the absolute deviations of the MIS 80 are, in general, within 40 mas, those of the MIS 60-70 are within 30 mas. For systematic differences δαα cosδ and δδα, the absolute deviations reach 30-40 mas for both MIS. For total systematic differences, local deformations of the FK5 system in the equatorial zone in both right ascension and declination has been found exceeding expected ones from the formal errors of the FK5 system by a factor about 1.5 for the MIS 60-70, and by a factor about 2 for the MIS 80. Consistency in area distribution between both MIS for the total systematic differences δαcosδ has been detected. Quick degradation of the FK5 system with time due to optimistic estimation of the errors of its proper motion system is supposed to be one of the main causes of its discrepancies with observations. The results in declination are recognized to be less reliable due to larger inconsistency of the individual instrumental systems.Before the next space astrometric mission will be realized, ground-based observations will continue to be the only available check of an external systematic accuracy of the HIPPARCOS catalogue. Evidently, random and, possibly, systematic accuracy of each individual catalogue observed from the Earth surface would be inferior to that of the HIPPARCOS catalogue. Taken as an ensemble, however, a certain selection of catalogues might give a rather definite idea about the actual distortions of the HIPPARCOS system. This study shows to which level of accuracy such ensembles of different selections of catalogues might check the HIPPARCOS system in the equatorial zone. The analysis of the FK5 gives also an idea about levels of random and systematic discrepancies which may be expected in the equatorial zone when the HIPPARCOS catalogue will be compared with the FK5 at different epochs.

scholarly journals An Inter-Hemispheric Volcanic Time-Marker in Ice Cores from Greenland and Antarctica

1988 ◽  
Vol 10 ◽  
pp. 102-108 ◽  
Author(s):  
C.C. Langway ◽  
H.B. Clausen ◽  
C.U. Hammer
Keyword(s):  
Ice Sheets ◽  
Ice Cores ◽  
Strong Acid ◽  
Historical Record ◽  
Equatorial Zone ◽  
Ice Shelf ◽  
Volcanic Event ◽  
Ross Ice Shelf ◽  
Volcanic Events ◽  
Volcanic Disturbance

A strong volcanic-acid signal is clearly registered, using an acidity-measuring technique, in the A.D. 1259 ice layer in four different Greenland ice cores (Camp Century, Milcent, Crête and Dye 3). This signal is similar in amplitude to the Laki (Iceland) A.D. 1783 volcanic event as recorded in the central and south Greenland ice cores. Measurement of ice layers from corresponding age levels in Antarctic ice cores (Byrd Station, South Pole and J–9 on the Ross Ice Shelf) provides similar strong acid signals. There is no historical record of a significant volcanic eruption for the period around A.D. 1260 in the Northern Hemisphere. Subsequent chemical analyses of all A.D. 1259 ice layers show similar compositions. We suggest that the A.D. 1259 signals registered in both Greenland and Antarctica were caused by the same volcanic disturbance and that its epicenter was located at the Earth’s equatorial zone, which enabled global distribution of the acid gases. These results indicate that inter-hemispheric dating of ice sheets is possible by the chemical identification of major eruptive volcanic events in the equatorial zone.

Burst in cosmic radiation in the equatorial zone

1939 ◽  
Vol 228 (4) ◽  
pp. 516-518
Author(s):  
S.A. Korff
Keyword(s):  
Cosmic Radiation ◽  
Equatorial Zone

scholarly journals Modified Method of Krejnin and Murri for the Determination of Absolute Declinations

1990 ◽  
Vol 141 ◽  
pp. 95-95
Author(s):  
S.A. Tolchelnikova-Murri
Keyword(s):  
Equatorial Zone ◽  
Micrometer Screw ◽  
Modified Method ◽  
Scale Error ◽  
Systematic Effects ◽  
Global Reduction ◽  
Improve Planning

Krejnin and Muni's method (1973) enablesenables one to derive absolute declinations of stars in a narrow equatorial zone |δ| < 10′ from observations near the Earth's equator |ϕ| < 10′. Some systematic effects, including the errors of the value of the micrometer screw for two equatorial instruments (or the scale error if one of the instruments is a PZT), might be determined if a global reduction is used for the original observations from the equator and from those of an astrolabe at latitude |ϕ| ∼ 20° to 23°. Astrolabes—especially photoelectric ones (Hu 1988) are considered to be the most efficient for determination of absolute declinations of stars and absolute latitudes of the instruments in Tolchel'nikova-Murri (1985).In Izv. GAO No. 206 the method will be published as well as the criterion for estimating the efficiency of different programs, which is required to improve planning in astrometry.

scholarly journals Behaviour of magnetotelluric source fields within the equatorial zone

1999 ◽  
Vol 51 (10) ◽  
pp. 1119-1125 ◽  
Author(s):  
Antonio L. Padilha
Keyword(s):  
Equatorial Zone

scholarly journals Wolf-Rayet Stellar Wind Theory

1991 ◽  
Vol 143 ◽  
pp. 289-308
Author(s):  
J. P. Cassinelli
Keyword(s):  
Magnetic Fields ◽  
Stellar Wind ◽  
Equatorial Zone ◽  
Radio Flux ◽  
Polar Wind ◽  
Radiative Processes ◽  
Rotator Model ◽  
Show Evidence ◽  
Wind Theory

Two possible solutions to the Wolf-Rayet wind momentum problem are discussed: purely radiation driven wind theory, with multi-line effects, and Luminous Magnetic Rotator theory. Several recently developed radiative processes for enhancing M or v∞ are described, and it is concluded that only the winds of rather hot luminous Wolf-Rayet stars could possibly be driven by radiation. These stars should show evidence of acceleration at large radial distances. For the rapid rotators, it is possible to drive a dense equatorial outflow. Limits are discussed regarding the needed surface magnetic fields. With this model, the wind momentum problem is solved in a piece-wise fashion by having the large radio flux of Wolf-Rayet stars come from the equatorial zone and the broad P Cygni lines, arising in the polar wind. The Luminous Magnetic Rotator model can also be tested through observation, primarily through spectropolarimetry.

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