Data Mining in Electronic Commerce

Modern business is rushing toward e-commerce. If the transition is done properly, it enables better management, new services, lower transaction costs and better customer relations. Success depends on skilled information technologists, among whom are statisticians. This paper focuses on some of the contributions that statisticians are making to help change the business world, especially through the development and application of data mining methods. This is a very large area, and the topics we cover are chosen to avoid overlap with other papers in this special issue, as well as to respect the limitations of our expertise. Inevitably, electronic commerce has raised and is raising fresh research problems in a very wide range of statistical areas, and we try to emphasize those challenges.Comment: Published at http://dx.doi.org/10.1214/088342306000000204 in the Statistical Science (http://www.imstat.org/sts/) by the Institute of Mathematical Statistics (http://www.imstat.org

Changes In Femoral Neck Bone Mineral Density: A Comparison Of NHANES 2005-2006, 2007-2008, And 2009-2010

Bone mass is an important component of quality of life and can be influenced by lifestyle factors, such as physical activity and diet. However the US surgeon general found a growing portion of Americans are not engaging in adequate amounts of physical activity and/or consuming less calcium and vitamin D. The purpose of this study was to compare bone mineral density (BMD) of American adults of different ethnicities and time periods to detect any differences. It was hypothesized that BMD would be lower in participants from more recent years, and African Americans would have the highest BMD. Measurements were taken at the femoral neck of volunteers between 18 and 35 years of age (n = 3578) from 2005-2006 (n = 1160), 2007-2008, (n = 1135), and 2009-2010 (n = 1283) by the National Center for Health Statistics. The data was analyzed using a three-way independent ANOVA with an alpha level of .05. Femoral neck BMD was used as the dependent variable; and year, age, and race were independent variables. The study found Hispanic women to have a significantly higher BMD from 2005-2006 (p \u3c.05) when compared to participants from later years. In addition, the study found significant differences based on age and ethnicity (p \u3c .001). African-American men (p \u3c .001) and women (p \u3c.001) had a higher BMD than any other ethnicity. Moreover, Hispanic men had a higher BMD (p \u3c.001) than Caucasian men. In men, BMD significantly decreased in each age group (p \u3c.001); whereas in women a significant decrease was detected in every other age group (p \u3c .05). However, in contradiction to literature, the results found peak BMD to occur between 18 and 19 years of age as opposed to mid-to-late twenties

The Boundary Cosmological Constant in Stable 2D Quantum Gravity

We study further the r\^ole of the boundary operator \O_B for macroscopic loop length in the stable definition of 2D quantum gravity provided by the $[{\tilde P},Q]=Q$ formulation. The KdV flows are supplemented by an additional flow with respect to the boundary cosmological constant $\sigma$. We numerically study these flows for the $m=1$, $2$ and $3$ models, solving for the string susceptibility in the presence of \O_B for arbitrary coupling $\sigma$. The spectrum of the Hamiltonian of the loop quantum mechanics is continuous and bounded from below by $\sigma$. For large positive $\sigma$, the theory is dominated by the `universal' $m=0$ topological phase present only in the $[{\tilde P},Q]=Q$ formulation. For large negative $\sigma$, the non--perturbative physics approaches that of the $[P,Q]=1$ definition, although there is no path to the unstable solutions of the $[P,Q]=1$ $m$-even models.Comment: (Plain Tex, 11pp, 4 figures available on request) SHEP 91/92-2

Three-dimensional structural damage localization system and method using layered two-dimensional array of capacitance sensors

A system and method for detecting damage to a structure is provided. The system includes a voltage source and at least one capacitor formed as a layer within the structure and responsive to the voltage source. The system also includes at least one sensor responsive to the capacitor to sense a voltage of the capacitor. A controller responsive to the sensor determines if damage to the structure has occurred based on the variance of the voltage of the capacitor from a known reference value. A method for sensing damage to a structure involves providing a plurality of capacitors and a controller, and coupling the capacitors to at least one surface of the structure. A voltage of the capacitors is sensed using the controller, and the controller calculates a change in the voltage of the capacitors. The method can include signaling a display system if a change in the voltage occurs

Long-term impacts of wildfire and logging on forest soils

Soils are a fundamental component of terrestrial ecosystems, and play key roles in biogeochemical cycles and the ecology of microbial, plant and animal communities. Global increases in the intensity and frequency of ecological disturbances are driving major changes in the structure and function of forest ecosystems, yet little is known about the long-term impacts of disturbance on soils. Here we show that natural disturbance (fire) and human disturbances (clearcut logging and post-fire salvage logging) can significantly alter the composition of forest soils for far longer than previously recognized. Using extensive sampling across a multi-century chronosequence in some of the tallest and most carbon-dense forests worldwide (southern Australian, mountain ash (Eucalyptus regnans) forests), we provide compelling evidence that disturbance impacts on soils are evident up to least eight decades after disturbance, and potentially much longer. Relative to long-undisturbed forest (167 years old), sites subject to multiple fires, clearcut logging or salvage logging were characterized by soils with significantly lower values of a range of ecologically important measures at multiple depths, including available phosphorus and nitrate. Disturbance impacts on soils were most pronounced on sites subject to compounding perturbations, such as multiple fires and clearcut logging. Long-lasting impacts of disturbance on soil can have major ecological and functional implications.Thank you for the following groups for funding: the Paddy Pallin Foundation, Centre of Biodiversity Analysis, the Ecological Society of Australia and the Holsworth Wildlife Research Endowment fund

Semiclassical Approach to Black Hole Evaporation

Black hole evaporation may lead to massive or massless remnants, or naked singularities. This paper investigates this process in the context of two quite different two dimensional black hole models. The first is the original CGHS model, the second is another two dimensional dilaton-gravity model, but with properties much closer to physics in the real, four dimensional, world. Numerical simulations are performed of the formation and subsequent evaporation of black holes and the results are found to agree qualitatively with the exactly solved modified CGHS models, namely that the semiclassical approximation breaks down just before a naked singularity appears.Comment: 15 pages, PUPT-1340, harvmac, 11 figures available on reques

Remark about string field for general configuration of N D-instantons

In this paper we would like to suggest matrix form of the string field for any configuration of N D-instantons in bosonic string field theory.Comment: 17 pages, R1:corrected some typos, reference adde

A theory of quantum black holes: non-perturbative corrections and no-veil conjecture

A common belief is that further quantum corrections near the singularity of a large black hole should not substantially modify the semiclassical picture of black hole evaporation; in particular, the outgoing spectrum of radiation should be very close to the thermal spectrum predicted by Hawking. In this paper we explore a possible counterexample: in the context of dilaton gravity, we find that non-perturbative quantum corrections which are important in strong coupling regions may completely alter the semiclassical picture, to the extent that the presumptive space-like boundary becomes time-like, changing in this way the causal structure of the semiclassical geometry. As a result, only a small fraction of the total energy is radiated outside the fake event horizon; most of the energy comes in fact at later retarded times and there is no information loss problem. Thus we propose that this may constitute a general characteristic of quantum black holes, that is, quantum gravity might be such as to prevent the formation of global event horizons. We argue that this is not unnatural from the viewpoint of quantum mechanics.Comment: 24 pages, 12 figures (not included, available by request), UTTG-22-9

A Rapid Assessment of Coral Reefs Near Hopetown, Abaco Islands, Bahamas (Stony Corals and Algae)

Coral reefs at 13 sites ranging in depth from 1-16 m near Hopetown, Abaco Islands, Bahamas were surveyed utilizing the Atlantic and Gulf Rapid Reef Assessment (AGRRA) benthos protocol. A total of 35 species of scleractinian corals and 2 species of calcareous hydrocorals were observed. The overall coral cover averaged just over 14%. Among corals that were at least 10 cm in diameter, small colonies (\u3c 40 cm diameter) predominated in all sites except for the Fowl Cay pinnacles where 68% were larger than 60 cm in diameter. Large colonies (\u3e 40 cm diameter) were also found in the Lynyard Cay spur-and-groove formations and the Sandy Cay fore reef. Zero-4% of the colonies were affected by disease. Total (recent + old) partial-colony mortality ranged from 9-31% (both extreme values being found in outer reef crests). Turf algae were the most common algal functional group overall. Macroalgae were ubiquitous, however, with relative abundance values of about 25-47%. Macroalgal indices (a proxy for biomass) ranged from 64 in the Sandy Cay back reef to 184 in the Fowl Cay outer reef crest