Theoretical interpretation of the ground-based photometry of Saturn's B ring     

Kari Lumme  William M. Irvine  Larry W. Esposito 《Icarus》1983,53(2):174-184

New photographic photometry at small tilt angles during the 1979 and 1981 apparitions is combined with earlier data to yield several physical parameters for Saturn's B ring in red and blue colors. Phase curves are obtained for a mean tilt angle B ? 6°. The value of the volume density D is 0.020±0.004 with no indication of dependence on either the color or the tilt angle for 6°<B<26°. This conclusion is not altered significantly if the individual ring particles have a phase function similar to the phase curves of bright solar system objects. For the geometric albedo of a single particle we derive 0.61±0.04 (red) and 0.41±0.03 (blue), which are superior to earlier estimates because of the additional data now available. These values and the derived amount of multiple scattering as a function of tilt angle constrain the particle phase function in the red to be moderately backscattering. Inferred values of the particle single-scattering albedo are $\text{0.7≤}\text{ω}{}_0\text{(}\text{red}\text{) ≤0.92}$ and $\text{0.5≤}\text{ω}{}_0\text{(}\text{blue}\text{) ≤0.7}$, depending on the choice of phase function. No indication was found that the particle photometric properties might depend on the vertical distance from the central plane. Our results show that the ground-based photometry is entirely consistent with the classical, many-particle-thick ring model.  相似文献   

A Tsunami Detection and Warning-focused Sea Level Station Metadata Web Service     

John J. Marra  Uday S. Kari  Stuart A. Weinstein 《Pure and Applied Geophysics》2008,165(11-12):2265-2273

Currently information used to describe sea-level stations (such as location, collection and transmission capabilities, operator identification, etc.) is distributed among databases held by multiple agencies, institutions and organizations. Such information could be used to support detection and warning. However, the Indian Ocean Tsunami of 26 December, 2004 made it clear that such information is not readily accessible, is difficult to use, and is often incomplete. In addressing this issue, agencies within the Pacific region are collaborating to develop a web service to expose station metadata enabling various types of real-time data mining client applications that support decision-making and strategic planning at Tsunami Warning Centers. Because information about sea levels has a broad range of applications, integration of this information in a way that is comprehensive, and enhances its access and use, would have a tremendous impact on lives and livelihoods.  相似文献   

A flow-foliated ignimbrite related to the Åland rapakivi granite in SW Finland     

Olav Eklund  Alexey Shebanov  Soren Fröjdö  Kari Yli-kyyny  Ulf B. Andersson 《地学学报》1996,8(6):548-557

A flow-foliated felsic ignimbrite constitutes the uppermost lithological unit of the 1.58 Gyr anorogenic magmatic rocks in SW Finland. The ignimbrite is derived from an explosive eruption of hot (≅ 950 °C) phenocryst-bearing A-type (rapakivi-type granite magma.
The ignimbrite is close in composition to subvolcanic rapakivi granites that occur in the margins of the kand rapakivi batholith. The subvolcanic granites crystallized under a pressure of ≅ 1 kbar and at temperatures of about 650–700 °C. However, both major and rare earth elements show that the ignimbrite- forming magma was more fractionated than the magma forming the subvolcanic varieties.
Supported by evidence of mafic-felsic magma mingling, it is suggested that injection of hot mafic magma into a shallow magma chamber produced the high temperature of the ignimbrite-forming magma. This injection increased the magmatic and the volatile pressure that caused the eruption of the dry felsic magma.  相似文献   

Lechatelierite inclusions in indochinites and the origin of tektites     

Kari A. Kinnunen 《Meteoritics & planetary science》1990,25(3):181-184

Abstract— The grain size distribution and shapes of lechatelierite inclusions (silica glass inclusions) have been determined from 20 splash-form tektites from the Khorat Plateau, northeastern Thailand. The chemical and petrographic properties are reviewed, and the absence of any type of inclusion other than bubbles is confirmed. These data suggest that the parent material for the lechatelierite inclusions is not the conventional detrital quartz. One possible precursor is silica of plant origin in the form of biogenic opal-CT. According to this model, the lechatelierite inclusions are formed by shock melting of opal phytoliths in plants. These opal phytolith melts were included in the shock-melted soil and bedrock, jetted from the impact site. The expansion of the vapor plume ejected the melt droplets in ballistic trajectories. This model is extended to all tektite groups, because of the similarity between lechatelierite inclusions in them.  相似文献   

On the role and the properties ofn body central configurations     

Donald G. Saari 《Celestial Mechanics and Dynamical Astronomy》1980,21(1):9-20

The role central configurations play in the analysis ofn body systems is outlined. Emphasis is placed on collision orbits, expanding gravitational systems, andn body zero radial velocity surfaces. In the second half of the paper, properties of cenral configurations are discussed. Here, emphasis is placed on describing a different approach to analyze these configurations, one which is related to the classical problem of the weightedsth mean values of a vector. This approach is illustrated by discussing the non-degeneracy of central configurations and by describing central configurations in various dimensions. This is a written version of a talk given at Oberwolfach, August, 1978.proceedings of the Sixth Conference on Mathematical Methods in Celestial Mechanics held at Oberwolfach (West Germany) from 14 to 19 August 1978.This research was supported in part by an NSF Grant.  相似文献   

Lakshmi Planum,Venus: Characteristics and models of origin     

Roberts  Kari M.  Head  James W. 《Earth, Moon, and Planets》1990,(1):193-249

Lakshmi Planum is distinctive and unique on the surface of Venus as an expansive (~2 × 10⁶km²), relatively smooth, flat plateau containing two large shield volcanoes and abundant volcanic plains in the midst of a region of extreme relief. It rises 3–5 km above the datum and is surrounded on all sides by bands of mountains interpreted to be of compressional tectonic origin. The major units mapped on Lakshmi are volcanic edifices, smooth, ridged and grooved plains units, and structural units referred to as ridged terrain. Three styles of volcanism are observed to dominate the surface of Lakshmi. Distributed effusive volcanism is associated with extensive plains deposits and many of the small shields, domes and cones mapped within the plateau. Centralized effusive volcanism is primarily associated with the paterae, Colette and Sacajawea, and their circumferential low-shield-forming deposits. The precise origin and evolution of these unusually large and complex structures is not understood, although a catastrophic, explosive origin is unlikely. Pyroclastic volcanism may be represented by a unit referred to as the diffuse halo. The origin and evolution of Lakshmi Planum is closely related to its compressional tectonic environment; volcanism on Lakshmi has occurred synchronously with tectonism in the surrounding orogenic belts. A model for the origin and evolution of Lakshmi Planum consisting of a continuous sequence of convergence and horizontal shortening of crustal segments against a preexisting block of tessera seems best able to account for the elevation, plateau shape and irregular polygonal outline of Lakshmi, as well as the presence of ridged terrain and its resemblance to tessera. Volcanism on Lakshmi is proposed to be the result of basal melting of a thickened crustal root. According to this model, the origin and evolution of Lakshmi Planum has consisted of the following sequence of events: (1) formation of a large, elevated block of tessera surrounded by low-lying plains; (2) convergence and underthrusting of crustal segments to produce peripheral mountain ranges, thickening, and uplift of the plateau; and (3) basal melting of the thickened crust and underthrust material and surface volcanism that occurred synchronously with continued edge deformation.'Geology and Tectonics of Venus', special issue edited by Alexander T. Basilevsky (USSR Acad. of Sci., Moscow), James W. Head (Brown University, Providence). Gordon H. Pettengill (MIT. Cambridge, Massachusetts) and R. S. Saunders (J.P.L., Pasadena).  相似文献   

TheN-body problem of celestial mechanics     

Donald G. Saari 《Celestial Mechanics and Dynamical Astronomy》1976,14(1):11-17

A selective survey of then-body problem of celestial mechanics is given where the emphasis is on the asymptotic behavior of all solutions ast, the possible configurations the particles can assume in phase space and in physical space, and collision and non-collision singularities.Supported in part by NSF Grant MPS 71-03407 A03.  相似文献   

Timescales of storage and recycling of crystal mush at Krafla Volcano,Iceland     

Kari M. Cooper  Kenneth W. W. Sims  John M. Eiler  Neil Banerjee 《Contributions to Mineralogy and Petrology》2016,171(6):54

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Indices for the assessment of environmental pollution of the Baltic Sea coasts: integrated assessment of a multi-biomarker approach   总被引：2，自引：0，他引：2  

Broeg K  Lehtonen KK 《Marine pollution bulletin》2006,53(8-9):508-522

Two mathematical methods to assess the "health status" of flounder (Platichthys flesus), eelpout (Zoarces viviparus) and blue mussel (Mytilus spp.) populations of the Baltic Sea were applied on selected biomarker data collected during the EU project "BEEP" (Biological Effects of Environmental Pollution on Marine Coastal Ecosystems). The Bioeffect Assessment Index (BAI) and the Integrated Biomarker Index (IBR) combine different biomarkers to single values, which can be used to describe the toxically-induced stress level of populations in different areas. Both indices determined here produced essentially similar results, which in most cases agreed with the known contamination levels in the different study areas. Advantages and limitations of index applications and interpretations are critically discussed. The use of indices provides comprehensive information about biological effects of pollution in marine organisms and may therefore serve as a useful tool for environmental management by ranking the pollution status of marine coastal areas.  相似文献   

Chemical pollution--has it been tackled sufficiently? Visions of a healthier Baltic Sea     

Lehtonen KK  Schiedek D 《Marine pollution bulletin》2006,53(8-9):375-376

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