A randomization test for the comparison of ordered sequences

Several algorithms, based on dynamic programming techniques, for comparing, matching, or cross-correlating two ordered sequences of observations now exist. All such algorithms produce one or more optimal matchings, no matter what data are used. This paper presents an empirical method, based on a randomization test, for assessing how well the given sequences are matched or slotted together. The randomization test is designed to test the assumption, implicit in most cross-correlation algorithms, that both sequences comprise observations, at unknown but ordered times, from the same underlying yet unknown function of time. The test is intuitively appealing, easy to implement, works well on both artificial and real data, and requires no complicated parametric modelling.     

Flood insurance and extreme events: the role of crisis in prompting changes in British institutional response to flood hazard

Insurance represents an effective response to natural hazards, spreading the cost of damage in space and time. The development of flood insurance for buildings and building contents in the UK is examined in order to assess the extent to which it fits a crisis-oriented model whereby changes in the nature and effectiveness of the response are triggered directly (and exclusively) by individual hazard events. The model is confirmed in outline, some factors influencing the imperfect link between insurance innovation and individual flood events are identified, and implications both of the widespread insurance cover availability and of the crisis orientation evident in the evolution of insurance policy are discussed.     

OSO-III high-energy gamma-ray experiment

Very preliminary results for the distribution of -rays with energies greater than 50 MeV are presented. Extraterrestrial -rays appear to be concentrated to the plane of the galaxy.     

210pb as a chronometer and tracer,Burrinjuck Reservoir,Australia

Cores taken at Burrinjuck Reservoir in southeastern New South Wales have been dated using the first appearance of ¹³⁷Cs, charcoal/bushfire correlations, and annual grass pollen peaks. None of the main ²¹⁰Pb dating models reproduced the ‘known’ chronology. Correlation analysis shows no significant relationship between original ²¹⁰Pb (unsupp.) concentration and grain-size, sedimentation rate or loss on ignition. Differences in sediment source may explain the variations in ²¹⁰Pb. A simple provenance model has been used to interpret the ratio of original ²¹⁰Pb (unsupp.)/²²⁶Ra as a tracer of topsoils and subsoils. High ratios in the reservoir sediments probably indicate eroded topsoils and low ratios eroded subsoils.     

Regression revisited

One traditional method of estimating ore reserves is to allocate the arithmetic mean of local samples to each block or stope within the deposit. Thirty years ago, Krige showed that this method produced a “bias” in the estimates, in that high values were commonly overestimated and low values underestimated. This bias became known as the “regression effect” because it could usually be corrected by an empirical regression relationship derived from previously mined areas. This paper shows how the regression effect can be reconciled with the geostatistical method of kriging and how a simple regression line may be derived before any areas are mined out. The method is similar to kriging with known mean, but acknowledges that the overall mean of the deposit may not be known precisely.     

Reversible ion-exchange fixation of cesium-137 leading to mobilization from reservoir sediments

The radioactive fission product, ¹³⁷Cs, has been observed to mobilize from bottom sediments of two South Carolina reservoirs during summer thermal stratification and hypolimnetic anoxia. Mobilization is attributed to ion-exchange displacement of ¹³⁷Cs from sediments by cations such as NH⁺₄, Fe⁺² and Mn⁺² released under anaerobic conditions.Three types of ¹³⁷Cs binding sites to sediment clay minerals are identified: 1) surface and planar sites from which ¹³⁷Cs is generally exchangeable by all cations studied (Na⁺, NH⁺₄, H⁺, Cs⁺, Ca⁺², Mg⁺², Fe⁺², and Mn⁺²); 2) wedge sites where ¹³⁷Cs exchange is sterically limited to cations of similar size and charge (NH⁺₄, Cs⁺, K⁺, and perhaps H₃O⁺); 3) interlayer sites from which ¹³⁷Cs is not readily exchanged. More than 15 years after final ¹³⁷Cs inputs, the reservoir sediments we studied showed the following percentage distribution of sites: 2 to 9% surface sites, 6 to 13% wedge sites, and 78 to 85% interlayer sites. In contrast, lake and stream sediments near Oak Ridge, Tennessee receiving ¹³⁷Cs inputs more than 20 years earlier had greater than 99% of their ¹³⁷Cs associated with non-exchangeable interlayer sites. The difference is attributed to the paucity in the South Carolina sediments of weathered micaceous clay minerals with their abundant interlayer sites. Such interlayer deficient clays are dominant in the Atlantic and Gulf coastal plains of the United States and elsewhere. This suggests that ¹³⁷Cs will be physically and chemically more mobile in such areas as well as more biologically available. Mobility will be enhanced in regimes where cation inputs favoring ¹³⁷Cs exchange occur. Subsurface waste disposal sites where anaerobic conditions develop with NH⁺₄ production and Fe⁺² and Mn⁺² release might be such a regime.     

Ultraminiature X-ray fluorescence spectrometer for in-situ geochemical analysis on Mars

Determination of the surface composition at various sites on the planet Mars will provide information essential to a better understanding of the geologic history of this complex planet. A spectrometer based upon the X-ray fluorescence method of elemental analysis has been developed in an ultraminiature, rugged form suitable for a spacecraft mission to Mars. The instrument employs two radioisotope sources (⁵⁵Fe and¹⁰⁹Cd) which irradiate adjacent areas on a regolith sample. Fluorescent X-rays emitted by the sample are detected by four thin-window proportional counters. Using pulse-height discrimination, the energy spectra are determined. Virtually all elements above sodium in the periodic table are detected if present at sufficient levels. Minimum detection limits range from 30 ppm to 2%. depending upon the element and the matrix. For most elements, they are below 0.5%. Accuracies also depend upon the matrix, but are generally better than ± 0.5% for all elements of atomic number greater than 14. Elements below sodium are also detected, but as a single group. Ambiguities of identification of the elements producing the observed spectra are minimal. Exotic geological materials are, therefore, just as susceptible to analysis as are the more common rocks. A computer model of the instrument has been developed and tested. This model was used to optimize instrument parameters during the design phase, and has now been expanded to perform automatic analysis of the output data.     

Paleomagnetic excursion recorded in latest Pleistocene deep-sea sediments,Gulf of Mexico

Paleomagnetic and/or micropaleontological studies have been carried out on approximately 28 sedimentary cores of latest Pleistocene age from the Gulf of Mexico. Sedimentation rates range from 9 cm to 20 cm/1000 yr. A distinct excursion in the earth's magnetic field occurs in the upper parts of 8 of 15 cores for which paleomagnetic studies were conducted and is independently correlated with planktonic foraminiferal zones. An inclination change to zero or negative inclination is often associated with a declination change. The age of the excursion was determined by extrapolation of sedimentation rates from the Z-Y paleontological boundary which is dated at 11,000 B.P. The magnetic excursion occurred between 12,500 and 17,000 yr ago within the upper part of zone Y. This falls within the age range of the Laschamp Event as originally defined.