RELAXING ASSUMPTIONS OF PERFECT INFORMATION IN PARK VISITATION MODELS*

Variables related to urban park awareness are identified and methods for relaxing assumptions of perfect information in park use models are discussed. Park awareness is related to park characteristics (age and degree of development of the park), population characteristics (race, age, length of residence, recreation participation), and distance. Park attributes are stronger predictors of both park awareness and use than is distance. These findings parallel similar research on the cognitive aspects of shopping decisions.     

Evidence for a low-density inflationary universe?

The inflationary unvierse model predicts the density parameter ₀ to be 1.0 with the cosmological constant ₀ usually taken to be zero, whereas observational estimates give ₀0.2 and ₀10^-57 cm^–2. It was found, however, that the observed variation of angular diameter with redshift for extragalactic radio sources could be interpreted in terms of a low density universe with linear size evolution of the sources for either an inflationary model with 0 or an open model with =0.     

Observations of longperiod mass velocity oscillations in the Sun's chromosphere

Observations made by the differential method in the H line have revealed longperiod (on a timescale of 40 to 80 min) line-of-sight velocity oscillations which increase in amplitude with distance from the centre to the solar limb and, as we believe, give rise to prominence oscillations. As a test, we present some results of simultaneous observations at the photospheric level where such periods are absent.Oscillatory processes in the solar chromosphere have been studied by many authors. Previous efforts in this vein led to the detection of shortperiod oscillations in both the mass velocities and radiation intensity (Deubner, 1981). The oscillation periods obtained do not, normally, exceed 10–20 min (Dubov, 1978). More recently, Merkulenko and Mishina (1985), using filter observations in the H line, found intensity fluctuations with periods not exceeding 78 min. However, the observing technique they used does not exclude the possibility that those fluctuations were due to the influence of the Earth's atmosphere. It is also interesting to note that in spectra obtained by Merkulenko and Mishina (1985), the amplitude of the 3 min oscillations is anomalously small and the 5 min period is altogether absent, while the majority of other papers treating the brightness oscillations in the chromosphere, do not report such periods in the first place. So far, we are not aware of any other evidence concerning the longperiod velocity oscillations in the chromosphere on a timescale of 40–80 min.Longperiod oscillations in prominences (filaments) in the range from 40 to 80 min, as found by Bashkirtsev et al. (1983) and Bashkirtsev and Mashnich (1984, 1985), indicate that such oscillations can exist in both the chromosphere and the corona (Hollweg et al., 1982).In this note we report on experimental evidence for the existence of longperiod oscillations of mass velocity in the solar chromosphere.     

Subaqueous pyroclastic flows and ignimbrites: an assessment

An assessment of the literature on subaqueous pyroclastic flows and their deposits shows that the term pyroclastic flow is frequently used loosely to describe primary, hot gas-rich pyroclastic flows, mass-flows which resulted from the transformation of gassupported flows into water-supported ones, and secondary mass-flows carrying redeposited pyroclastic debris. Based on subaerial pyroclastic flows, the term pyroclastic flow should be restricted to demonstrably hot, gas-rich mass-flows of pyroclastic debris. Using this definition, very few examples of subaqueous pyroclastic deposits with evidence for hot emplacement and of having been wholly submerged have been described. In the majority of these cases, the evidence for a hot state of emplacement and for the subaqueous nature of the host depositional environment is inadequate. The only unequivocal cases of hot pyroclastic flow deposits with adequate supporting evidence are the Ordovician nearshore, shallow marine ignimbrites of Ireland and Wales, and Miocene ignimbrites of southwest Japan, resulting from the passage of subaerially erupted pyroclastic flows into shallow water. Other possible examples are near-vent dense clast deposits in the Donzurobo Formation of Japan, possible submarine intra-caldera ponded ignimbrite successions in California and Wales, and near-vent pumiceous deposits of Ramsay Island, Wales. All other purported cases are either clearly the result of water-supported mass-flow transportation and deposition (debris avalanches, debris flows, turbidity currents), or lack adequate supporting evidence regarding the heat state or the palaeoenvironment. Only the shallow marine ignimbrites of Ireland and Wales show adequate evidence of welding, but even these could have been nearly wholly exposed above sea-level when welding occurred. We conclude that when pyroclastic flows enter water they are generally disrupted explosively and/or ingest water and transform into water-supported mass-flows, and we suggest the various scenarios in which this occurs. There is no evidence to suggest that welding in wholly subaqueous environments is common.     

Ion microprobe analysis of oxygen isotope ratios in granulite facies magnetites: diffusive exchange as a guide to cooling history

Ion microprobe analysis of magnetites from the Adirondack Mountains, NY, yields oxygen isotope ratios with spatial resolution of 2–8 m and precision in the range of 1 (1 sigma). These analyses represent 11 orders of magnitude reduction in sample size compared to conventional analyses on this material and they are the first report of routinely reproducible precision in the 1 per mil range for analysis of ¹⁸O at this scale. High precision micro-analyses of this sort will permit wide-ranging new applications in stable isotope geochemistry. The analyzed magnetites form nearly spherical grains in a calcite matrix with diopside and monticellite. Textures are characteristic of granulite facies marbles and show no evidence for retrograde recrystallization of magnetite. Magnetites are near to Fe₃O₄ in composition, and optically and chemically homogeneous. A combination of ion probe plus conventional BrF₅ analysis shows that individual grains are homogeneous with ¹⁸O=8.9±1 SMOW from the core to near the rim of 0.1–1.2 mm diameter grains. Depth profiling into crystal growth faces of magnetites shows that rims are 9 depleted in ¹⁸O. These low ¹⁸O values increase in smooth gradients across the outer 10 m of magnetite rims in contact with calcite. These are the sharpest intracrystalline gradients measured to date in geological materials. This discovery is confirmed by bulk analysis of 150–350 m diameter magnetites which average 1.2 lower in ¹⁸O than coarse magnetites due to low ¹⁸O rims. Conventional analysis of coexisting calcite yields °¹⁸O=18.19, suggesting that bulk ¹⁸O (Cc-Mt)=9.3 and yielding an apparent equilibration temperature of 525° C, over 200° C below the temperature of regional metamorphism. Consideration of experimental diffusion data and grain size distribution for magnetite and calcite suggests two contrasting cooling histories. The data for oxygen in calcite under hydrothermal conditions at high P(H₂O) indicates that diffusion is faster in magnetite and modelling of the low ¹⁸O rims on magnetite would suggest that the Adirondacks experienced slow cooling after Grenville metamorphism, followed by a brief period of rapid cooling, possibly related to uplift. Conversely, the data for calcite at low P(H₂O) show slower oxygen diffusion than in magnetite. Modelling based on these data is consistent with geochronology that shows slow cooling through the blocking temperature of both minerals, suggesting that the low ¹⁸O rims form by exchange with late, low temperature fluids similar to those that infiltrated the rock to serpentinize monticellite and which infiltrated adjacent anorthosite to form late calcite veinlets. In either case, the ion microprobe results indicate that two distinct events are recorded in the post-metamorphic exchange history of these magnetites. Recognition of these events is only possible through microanalysis and has important implications for geothermometry.     

Directions and possibilities of mathematical geology

This paper considers the present state of mathematical geology. Three directions are recognized: applied, theoretical, and mathematical. Applied mathematical geology includes formal use of mathematics to solve problems and computer processing of data. Success is achieved by a correspondence of mathematical methods used to the nature of geological data. This correspondence can be demonstrated by purely mathematical means. Theoretical mathematical geology uses mathematics as a language of geology; however, a number of methodological problems must be solved: formalization of initial geological concepts and creation of a strict conceptual basis, substantiation of initial principles of mathematical simulation, creation of theoretical geological models, problems of elementary and coincidence in geology, and methodological substantiations of possibilities of any mathematical model to approximate geological models. The essense and significance of these problems are considered. The main task of mathematical geology is to prove its correspondence to the nature of the geological objects studied, geological data obtained, and geological problems solvable. Finally, the main problems of mathematical geology are not so much mathematical as geological and methodological.     

The demographic responses to famine: The case of China 1958–61

Pre-1949 China was The Sick Man of Asia, The Land of Famine. In 1949 Mao brought the communists to power and in the re-ordered world, all such problems were supposedly overcome — but not so. Thirty years ago China suffered one of the world's worst famines. Over the four years 1958–61, China suffered some 25–30 million more deaths and experienced some 30–35 million fewer births than might have been expected under normal conditions. Yet for almost a quarter of a century there would be few, outside of China, who were aware of the existence let alone the dimensions of the disaster. Access to Chinese census data since the mid-1980s has permitted a preliminary analysis of the demographic impact of the famine.Abbreviations JPRS-CEA-81-128 Joint Publications Research Service, China Economic Affairs Report 128, 1981 - JPRS-CPS-85-028 Joint Publications Research Service. China Report, Political, Sociological & Military Affairs 28, 1985