Systematizing local knowledge using GIS: fisheries management in Bang Saphan Bay, Thailand

Although local knowledge is a crucial source of information for fishery development, its generally unsystematic presentation and nebulous content makes use by policy makers or managers difficult. Based on field data obtained using Participatory Rural Appraisal at Bang Saphan Bay, Prachuap Khiri Khan Province, Thailand, we attempt to show here how local knowledge can be effectively systematized, analyzed and displayed visually using a Geographical Information System (GIS) for use in fisheries management. PRA data on location fished, time of fishing, techniques and technology used and species targeted were obtained from local fishers then mapped using Arcview (3.1). In this way local fisheries knowledge can be converted into geo-spatial data form via GIS, and the succinct results used easily to guide fishery management and planning, especially by offering directions for rights-based fisheries and co-management.     

Accessory silicate mineral assemblages in the Bilanga diogenite: A petrographic study

Abstract— The petrographic relationships in diogenites between orthopyroxene and minor phases such as chromite, troilite, diopside, plagioclase, and silica are often obscured by the intense brecciation that characterizes these meteorites. Although brecciated, Bilanga preserves numerous clasts displaying primary textural relations between orthopyroxene and these minor phases that are large enough to analyze by electron microprobe. In this study, we focus on the distribution, composition, and origin of the minor phases in Bilanga to provide new insights into the crystallization and metamorphic history of these rocks. The samples examined consist mainly of orthopyroxene grains plus five types of assemblages containing diopside + a Fe‐rich phase (chromite, troilite, and/or Fe‐Ni metal) ± plagioclase ± silica. We interpret type 1 assemblages as being remnants of intercumulus melt trapped in the interstices between orthopyroxene grains after crystal settling in a magma chamber. Type 2 assemblages appear to have formed by heterogeneous exsolution during thermal metamorphism. Type 3 assemblages are believed to be remnants of other assemblages that have been shocked, melted, and rapidly recrystallized by impact events. Type 4 assemblages consist of veins that also appear to have formed from trapped intercumulus melt. Regions of silica‐rich mesostasis (type 5) appear to be larger patches of more evolved intercumulus melt that have been significantly affected by late‐stage impact melting. Finally, large clasts containing plagioclase ± diopside are interpreted to be exotic fragments of a different but possibly related rock type incorporated in the Bilanga breccia.     

Monte Carlo modeling of neutral gas and dust in the coma of Comet 1P/Halley

The neutral gas environment of a comet is largely influenced by dissociation of parent molecules created at the surface of the comet and collisions of all the involved species. We compare the results from a kinetic model of the neutral cometary environment with measurements from the Neutral Mass Spectrometer and the Dust Impact Detection System onboard the Giotto spacecraft taken during the fly-by at Comet 1P/Halley in 1986. We also show that our model is in good agreement with contemporaneous measurements obtained by the International Ultraviolet Explorer, sounding rocket experiments, and various ground based observations.The model solves the Boltzmann equation with a Direct Simulation Monte Carlo technique (Tenishev, V., Combi, M., Davidsson, B. [2008]. Astrophys. J. 685, 659-677) by tracking trajectories of gas molecules and dust grains under the influence of the comet’s weak gravity field with momentum exchange among particles modeled in a probabilistic manner. The cometary nucleus is considered to be the source of dust and the parent species (in our model: H₂O, CO, H₂CO, CO₂, CH₃OH, C₂H₆, C₂H₄, C₂H₂, HCN, NH₃, and CH₄) in the coma. Subsequently our model also tracks the corresponding dissociation products (H, H₂, O, OH, C, CH, CH₂, CH₃, N, NH, NH₂, C₂, C₂H, C₂H₅, CN, and HCO) from the comet’s surface all the way out to 10⁶ km.As a result we are able to further constrain cometary the gas production rates of CO (13%), CO₂ (2.5%), and H₂CO (1.5%) relative to water without invoking unknown extended sources.     

Growth of the ice phase in strong cumulonimbus updrafts

A numerical model of ice phase growth in an ascending parcel is used to delineate seeding requirements under the competing embryo and glaciation hypotheses. The strong updraft core is found to remain virtually all liquid until homogeneous freezing occurs, AgI or dry ice seeding having negligible effects with achievable seeding rates. This suggests that the glaciation hypothesis is untenable. Natural hail embryo formation is noted to be limited to updrafts less than 3 to 4 m sec^?1 at cloud base. AgI seeding of such updraft regions at rates currently used is found to produce concentrations of hail embryos sufficient to enhance competition in multi-cell hailstorms, although super-cell storms may require significantly greater seeding rates.     

The volcano-magnetic effect

Summary A geometrically simple volcano is considered, havig a spherical magma chamber of 2.5 km radius centred at 10 km depth. The Curie point isotherm is assumed to be a plane at 20 km depth, except for the spherical volume which is also non-magnetic. The stress pattern in the vicinity of the spherical chamber, due to regional stress of sufficient intensity to cause an eruptions, is used to calculate the change in magnetization which results from the piezomagnetic effect through the volume of solid rock. The consequent magnetic field anomaly at the surface is then obtaied by numerical integration of the dipole law of force over the stressed volume. For rocks of the type found on the volcanic island of St. Vincent (West Indies), this model gives a maximum local volcano-magnet c effect of about 7 gammas.     

Comparison of nitrate attenuation characterization methods at the Uranium mill tailing site in Monument Valley, Arizona

Several methods for characterizing the occurrence and rate of nitrate attenuation were tested at a field site near Monument Valley, Arizona. Spatial and temporal nitrate concentration data collected from a transect of monitoring wells located along the plume centerline were analyzed to evaluate the overall rates of natural attenuation. The occurrence and rate of denitrification was evaluated through microcosm experiments, nitrogen isotopic fractionation analysis, and solute-transport modeling. First-order denitrification-rate coefficients calculated with each method were comparable. In addition, the composite natural attenuation rate coefficient was similar to the denitrification-rate coefficients, which suggests that microbially induced decay primarily controls nitrate attenuation at the site. This research highlights the benefits associated with a multiple-method approach for the characterization of natural attenuation.     

Steady state hodographs in a baroclinic boundary layer

If the steady-state geostrophic wind vector varies exponentially with height in the planetary boundary layer, calculated hodographs of the 24-hour mean wind resemble the classic Ekman spiral distorted by thermal effects. For such an assumed distribution, Lettau's (1967) conclusion that the effects of thermal influence on the steady-state boundary-layer winds can be linearly superimposed on the effects of internal friction is justified.The minimum value of the cross-isobar angle of the surface wind for a given magnitude of the thermal wind vector occurs when that vector points about 345° to the right of the surface geostrophic wind vector and the maximum value occurs when it points at an azimuth of about 120° relative to the surface geostrophic wind vector. The range of values of the cross-isobar angle is almost directly proportional to the magnitude of the thermal wind vector.Hodographs resulting from the assumed variation of the geostrophic wind have approximately the same shape as 24-hour mean hodographs at two locations over the Great Plains.This work is part of a thesis submitted to the University of Wisconsin in partial fulfillment of the requirements for the Ph.D. Degree, written under the supervision of Professor H. Lettau, Department of Meteorology.     

Forecasting in the social and natural sciences: An overview and analysis of isomorphisms

This article identifies and analyzes several points of similarity in the structure and context of forecasting in the social and natural sciences. These include: the limits of identities or universal laws as a basis for forecasts; the corresponding need for simplifying parametric representations of one or more of the variables that enter into identities; various sources of uncertainty about parameterizations; intrinsic limitations on predictability or forecasting accuracy in large-scale systems; the need for sensitivity analyses of model responses to changes in exogenous variables and/or parametric structures; problems of model linkage; and the social (organizational and political) context of forecasts. Suggestions for future lines of inquiry are made in each case. Several of these are such that they can benefit from a sharing of experience and expertise across disciplinary lines.The research reported herein was supported in part by the IC² Institute, The University of Texas at Austin, and in part by National Science Foundation Grant Number SES-8411702. However, the opinions expressed in the paper are those of the authors and do not necessarily reflect those of the sponsoring organizations. We appreciate the advice and comments of Jesse H. Ausubel, Robert S. Chen, Judith Jacobsen, and Richard C. Rockwell on earlier versions of this paper.The National Center for Atmospheric Research is sponsored by the National Science Foundation.