Conducting market research using the internet: The case of Xenon laboratories

The way market research is conducted has changed dramatically over the past 30 years, as a result of both the development of the prevailing view of best practice and the state of technology available to researchers. While it is clear that the World Wide Web (WWW) will increasingly be used as a medium for conducting market research, the full implications of this new channel are not yet fully understood. This paper examines the potential for an Internet-based financial services firm (Xenon Laboratories) to analyse conduct market research using the WWW. The case demonstrates that, by employing a novel approach to market research, Xenon Laboratories is in a unique position to understand the charging structures in its market, the market for international payments using credit or charge cards. In doing so, the paper highlights the opportunity to unobtrusively gather market information from an international group of customers by providing Internet-based value-added services

Identifying Deficiencies of Standard Accretion Disk Theory: Lessons from a Mean-Field Approach

Turbulent viscosity is frequently used in accretion disk theory to replace the microphysical viscosity in order to accomodate the observational need for in- stabilities in disks that lead to enhanced transport. However, simply replacing the microphysical transport coefficient by a single turbulent transport coeffi- cient hides the fact that the procedure should formally arise as part of a closure in which the hydrodynamic or magnetohydrodynamic equations are averaged, and correlations of turbulent fluctuations are replaced by transport coefficients. Here we show how a mean field approach leads quite naturally two transport coefficients, not one, that govern mass and angular momentum transport. In particular, we highlight that the conventional approach suffers from a seemingly inconsistent neglect of turbulent diffusion in the surface density equation. We constrain these new transport coefficients for specific cases of inward, outward, and zero net mass transport. In addition, we find that one of the new transport terms can lead to oscillations in the mean surface density which then requires a constant or small inverse Rossby number for disks to maintain a monotonic power-law surface density.Comment: 11 page

Reprocessed emission line profiles from dense clouds in geometrically thick accretion engines

The central engines of active galactic nuclei (AGN) contain cold, dense material as well as hot X-ray emitting gas. The standard paradigm for the engine geometry is a cold thin disc sandwiched between hot X-ray coronae. Strong support for this geometry in Seyferts comes from the study of fluorescent iron line profiles, although the evidence is not ubiquitously air tight. The thin disc model of line profiles in AGN and in X-ray binaries should be bench marked against other plausible possibilities. One proposed alternative is an engine consisting of dense clouds embedded in an optically thin, geometrically thick X-ray emitting engine. This model is further motivated by studies of geometrically thick engines such as advection dominated accretion flows (ADAFs). Here we compute the reprocessed iron line profiles from dense clouds embedded in geometrically thick, optically thin X-ray emitting discs near a Schwarzchild black hole. We consider a range of cloud distributions and disc solutions, including ADAFs, pure radial infall, and bipolar outflows. We find that such models can reproduce line profiles similar to those from geometrically thin, optically thick discs and might help alleviate some of the problems encountered from the latter.Comment: 9 Pages LaTex, + Figs, submitted to MNRA

Reprocessed emission from warped accretion discs with application to X-ray iron line profiles

Flourescent iron line profiles currently provide the best diagnostic for active galactic nuclei (AGN) engine geometries. Here we construct a method for calculating the relativistic iron line profile from an arbitrarily warped accretion disc, illuminated from above and below by hard X-ray sources. This substantially generalises previous calculations of reprocessing by accretion discs by including non-axisymmetric effects. We include a relativistic treatment of shadowing by ray-tracing photon paths along Schwarzchild geodesics. We apply this method to two classes of warped discs, and generate a selection of resulting line profiles. New profile features include the possibility of sharper red, and softer blue fall-offs, a time varying line profile if the warp precesses about the disc, and some differences between `twisted' and `twist-free' warps. We discuss some qualitative implications of the line profiles in the context of Type I and II Seyfert AGN.Comment: 15 pages, LaTeX + eps files + 6 separate gif files, Submitted to MNRA

Iron line profiles from black hole accretion discs with spiral velocity structure

We calculate the iron line profiles from accretion discs with spiral velocity structures around Schwarzschild black holes. We find that quasi-periodic bumps appear in the the profiles, thereby providing a test for spiral wave patterns. This study is motivated by recent work showing that spiral density waves can result from MHD instabilities even in non-self-gravitating discs, and by improved spectral resolution of forthcoming X-ray missions.Comment: 4 pages LaTeX with 3 of the figures separate, submitted to MNRA

Does Eco-Certification Have Environmental Benefits? Organic Coffee in Costa Rica

Eco-certification of coffee, timber and other high-value agricultural commodities is increasingly widespread. In principle, it can improve commodity producers’ environmental performance, even in countries where state regulation is weak. However, evidence needed to evaluate this hypothesis is virtually nonexistent. To help fill this gap, we use detailed farm-level data to analyze the environmental impacts of organic coffee certification in central Costa Rica. We use propensity score matching to control for self-selection bias. We find that organic certification improves coffee growers’ environmental performance. It significantly reduces chemical input use and increases adoption of some environmentally friendly management practices.certification, coffee, Costa Rica, propensity score matching