A Seismic Inversion Problem for an Anisotropic, Inhomogeneous Medium

In this report, we consider the propagation of seismic waves through a medium that can be subdivided into of two distinct parts. The upper part is assumed to be azimuthally symmetric, linearly nonuniform with increasing depth, and the velocity dependence with direction consistent with elliptical anisotropy. The lower part, which is the layer of interest, is assumed to also be azimuthally symmetric, but uniform and nonelliptically anisotropic. Despite nonellipticity, we assume the angular dependence of the velocity can be described by a convex curve. Our goal is to produce a single source-single receiver model which uses modern seismic measurements to determine the elastic moduli of the lower media. Once known, geoscientists could better describe the angular dependence of the velocity in the layer of interest and also would have some clues at to the actual material composing it

Automatic detection of potentially illegal online sales of elephant ivory via data mining

In this work, we developed an automated system to detect potentially illegal elephant ivory items for sale on eBay. Two law enforcement experts, with specific knowledge of elephant ivory identification, manually classified items on sale in the Antiques section of eBay UK over an 8 week period. This set the “Gold Standard” that we aim to emulate using data-mining. We achieved close to 93% accuracy with less data than the experts, as we relied entirely on metadata, but did not employ item descriptions or associated images, thus proving the potential and generality of our approach. The reported accuracy may be improved with the addition of text mining techniques for the analysis of the item description, and by applying image classification for the detection of Schreger lines, indicative of elephant ivory. However, any solution relying on images or text description could not be employed on other wildlife illegal markets where pictures can be missing or misleading and text absent (e.g., Instagram). In our setting, we gave human experts all available information while only using minimal information for our analysis. Despite this, we succeeded at achieving a very high accuracy. This work is an important first step in speeding up the laborious, tedious and expensive task of expert discovery of illegal trade over the internet. It will also allow for faster reporting to law enforcement and better accountability. We hope this will also contribute to reducing poaching, by making this illegal trade harder and riskier for those involved

The Political Ecology of Takeovers: Thoughts On Harmonizing the European Corporate Governance Environment

Economic policy debate in the United States during the 1980s focused on the dynamics of bidder and target tactics in hostile takeovers. Confronted with the largest transactions in business history, financial economists took advantage of developments in econometric techniques to conduct virtually real time studies of the impact on firm value of each new bidder tactic and target defense. For courts and lawyers, hostile takeovers subjected standard features of corporate law to the equivalent of a stress x-ray, revealing previously undetected doctrinal cracks. Congress held seemingly endless hearings on the subject, although managing to enact only relatively innocuous tax penalties on particular defensive tactics the public found especially offensive. State legislatures, closer to the political action, acted more substantively, if less wisely. Whether or not takeovers created new wealth they did result in its transfer, and at least one of the parties from whom wealth was transferred – target management – had remarkable influence in state legislatures. When labor also came actively to oppose hostile takeovers, the coalition was virtually unstoppable. The decade saw some thirty-four states pass more than sixty-five major laws restricting corporate takeovers, including states discouraging partial offers and front-end loaded offers. The 1980s have now closed transactionally as well as chronologically. The first quarter of 1991 marked the lowest level of merger and acquisition activity since the first quarter of 1980. The passing of this remarkable decade invites a broader perspective, which can be helpfully thought of as the political ecology of takeovers. An ecological perspective builds on the proposition that phenomena are embedded in interactive systems – a rich web of mutually dependent relationships. Thus, a seemingly independent event cannot be fully evaluated without understanding how it relates to the environmental forces to which it was a response and which, in turn, respond to it. What the narrow focus of the 1980s debate missed was an appreciation of the complex economic corporate governance and political environments in which hostile takeovers are embedded. Corporate acquisitions are a response to real conditions in the economic environment. The choice among acquisition techniques, most importantly between friendly and hostile transactions, depends both upon the economic motivation for the transaction and upon conditions in the corporate governance environment. Finally, conditions in the corporate governance environment are directly influenced by politics; both what is allowed and prohibited is defined, in the first instance, by legislation. My goal in this article is two-fold. I begin by sketching the political ecology of takeovers in the United States – the interaction of economics, corporate governance and politics that shaped the experience of the 1980s. I then make a tentative effort at applying the insights gained from an ecological perspective to the current endeavor to change dramatically the European corporate governance environment through the harmonization of takeover and company law in the European Community. Sheltered by the cloak of political naivete commonly allowed those attempting comparative analysis from a distance, I will argue that an ecological understanding of takeovers suggests a different approach than that reflected so far in the debate over the terms of harmonization. This approach is based on what I term the mutability principle

Effect of weathering product assemblages on Pb bioaccessibility in mine waste: implications for risk management

General assessments of orebody types and associated mine wastes with regards to their environmental signature and human health hazards are needed to help managing present and historical mine waste facilities. Bioaccessibility tests and mineralogical analysis were carried out on mine waste from a systematic sampling of mine sites from the Central Wales orefield, UK. The bioaccessible Pb widely ranged from 270 to 20300 mg/kg (mean 7250 mg/kg; median 4890 mg/kg) and the bioaccessible fraction from 4.53 % to >100 % (mean 33.2 %; median 32.2 %), with significant (p=0.001) differences among the mine sites. This implies sensitivity of bioaccessibility to site-specific conditions and suggests caution in the use of models to assess human health impacts generalised on the basis of the mineral deposit type. Mineralogical similarities of the oxidation products of primary galena provided a better control over the observed Pb bioaccessibility range. The higher Pb bioaccessibility (%) was related to samples containing cerussite, irrespective of the presence of other Pb minerals in the mineral assemblage; lower Pb bioaccessibility resulted where anglesite was the main Pb mineral phase and cerussite was absent. A solubility diagram for the various Pb minerals in the waste was derived using PHREEQC model and the experimental Pb concentration measured in the simulated gastric solution compared with the equilibrium modelling results. For samples containing cerussite, the model well predicted the soluble Pb concentrations measured in the experimental simulated gastric solution, indicative of the carbonate mineral phase control on the Pb in solution for these samples and little kinetic control on the dissolution of cerussite. On the contrary, most mine waste samples containing dominant anglesite and or plumbojarosite (no cerussite) had lower solution Pb values, falling at or below the anglesite and plumbojarosite solubility equilibrium concentrations, implying kinetic or textural factors hindering the dissolution

A Survey of 10-Micron Silicate Emission from Dust around Young Sun-Like Stars

We obtained low resolution (R = 100) mid-infrared (8-13 micron wavelengths) spectra of 8 nearby young main sequence stars with the Keck 1 telescope and Long-Wavelength Spectrometer (LWS) to search for 10 micron silicate (Si-O stretch) emission from circumstellar dust. No stars exhibited readily apparent emission: Spectra were then analyzed by least-squares fitting of a template based on a spectrum of Comet Hale-Bopp. Using this technique, we were able to constrain the level of silicate emission to a threshold ten times below what was previously possible from space. We found one star, HD 17925, with a spectrum statistically different from its calibrator and consistent with a silicate emission peak of 7% of the photosphere at a wavelength of 10 microns. Excess emission at 60 microns from this star has already been reported.Comment: 19 total pages, 5 Postscript figures, 2 tables, Late