Optimal pricing using online auction experiments: A P\'olya tree approach

We show how a retailer can estimate the optimal price of a new product using observed transaction prices from online second-price auction experiments. For this purpose we propose a Bayesian P\'olya tree approach which, given the limited nature of the data, requires a specially tailored implementation. Avoiding the need for a priori parametric assumptions, the P\'olya tree approach allows for flexible inference of the valuation distribution, leading to more robust estimation of optimal price than competing parametric approaches. In collaboration with an online jewelry retailer, we illustrate how our methodology can be combined with managerial prior knowledge to estimate the profit maximizing price of a new jewelry product.Comment: Published in at http://dx.doi.org/10.1214/11-AOAS503 the Annals of Applied Statistics (http://www.imstat.org/aoas/) by the Institute of Mathematical Statistics (http://www.imstat.org

On Approaching the Ultimate Limits of Photon-Efficient and Bandwidth-Efficient Optical Communication

It is well known that ideal free-space optical communication at the quantum limit can have unbounded photon information efficiency (PIE), measured in bits per photon. High PIE comes at a price of low dimensional information efficiency (DIE), measured in bits per spatio-temporal-polarization mode. If only temporal modes are used, then DIE translates directly to bandwidth efficiency. In this paper, the DIE vs. PIE tradeoffs for known modulations and receiver structures are compared to the ultimate quantum limit, and analytic approximations are found in the limit of high PIE. This analysis shows that known structures fall short of the maximum attainable DIE by a factor that increases linearly with PIE for high PIE. The capacity of the Dolinar receiver is derived for binary coherent-state modulations and computed for the case of on-off keying (OOK). The DIE vs. PIE tradeoff for this case is improved only slightly compared to OOK with photon counting. An adaptive rule is derived for an additive local oscillator that maximizes the mutual information between a receiver and a transmitter that selects from a set of coherent states. For binary phase-shift keying (BPSK), this is shown to be equivalent to the operation of the Dolinar receiver. The Dolinar receiver is extended to make adaptive measurements on a coded sequence of coherent state symbols. Information from previous measurements is used to adjust the a priori probabilities of the next symbols. The adaptive Dolinar receiver does not improve the DIE vs. PIE tradeoff compared to independent transmission and Dolinar reception of each symbol.Comment: 10 pages, 8 figures; corrected a typo in equation 3

The Simulation of Subsurface Effects on the Diurnal Surface Thermal Regime in Cold Regions

... Layered substrate materials are common in nature; these include naturally stratified soils, ice and snow. ... solar radiation penetrates the surface and produces subsurface heating in snow and ice terrain. The stratification problem has been treated by numerous authors as variation of the periodic heat flow problem using surface temperature as the forcing function. ... In recent years there has been a considerable interest in the possibility of acquiring surface environmental information using the spatial variance in the phase and amplitude of the diurnal surface thermal regime as an indicator. ... It would appear that melting rock glacier ice cores, massive ground ice and active layer depth variations contribute significantly to the surface thermal regime variance when these features are relatively close to the surface. It would however appear that lake and sea ice depth variations with either spatially homogeneous light snow cover or none should be detectable particularly where there are large depth variations. Whereas surface climate simulation presents an explicit method of estimating the influence of a wide range of surface environmental factors, specifically albedo, emissivity, substrate radiation extinction (ice and snow), roughness, wetness, stratified thermal properties, slope and exposure, the method would appear to be extremely valuable in the experimental design and hypothesis formation phases of thermal mapping investigations in cold regions. Furthermore as the strategy can be employed to estimate the sensitivity of the surface thermal response to individual environmental factors the method dictates the ground truth requirements for exploratory investigations. Lastly as process and environmental information becomes available the strategy can be used to construct explicit deterministic physical models of the spatial and temporal variance of surface thermal response which can be employed as an analytical portion of a remote sensing reconnaissance system specific to trafficability and site studies in arctic and alpine environments. In short, the capacity for modelling the surface thermal response as a function of the surface and substrate environment vastly increases the accessible information content of thermal infrared maps particularly where these are acquired at several times during the diurnal cycle

Gravitational self-torque and spin precession in compact binaries

We calculate the effect of self-interaction on the "geodetic" spin precession of a compact body in a strong-field orbit around a black hole. Specifically, we consider the spin precession angle $\psi$ per radian of orbital revolution for a particle carrying mass $\mu$ and spin $s \ll (G/c) \mu^2$ in a circular orbit around a Schwarzschild black hole of mass $M \gg \mu$. We compute $\psi$ through $O(\mu/M)$ in perturbation theory, i.e, including the correction $\delta\psi$ (obtained numerically) due to the torque exerted by the conservative piece of the gravitational self-field. Comparison with a post-Newtonian (PN) expression for $\delta\psi$, derived here through 3PN order, shows good agreement but also reveals strong-field features which are not captured by the latter approximation. Our results can inform semi-analytical models of the strong-field dynamics in astrophysical binaries, important for ongoing and future gravitational-wave searches.Comment: 5 pages, 1 table, 1 figure. Minor changes to match published versio

Chytrid fungus infection in alpine tree frogs is associated with individual heterozygosity and population isolation but not population-genetic diversity

Chytridiomycosis, a disease caused by the emerging fungus Batrachochytrium dendrobatidis (Bd), has been implicated in the decline of over 500 amphibian species. Population declines could have important genetic consequences, including reduced genetic diversity. We contrasted genetic diversity among both long-Bd-exposed and unexposed populations of the south-east Australian alpine tree frog (Litoria verreauxii alpina) across its range. At the population level, we found no significant differences in genetic diversity between Bd-exposed and unexposed populations. Encouragingly, even Bd-infected remnant populations that are now highly isolated maintain genetic diversity comparable to populations in which Bd is absent. Spatial genetic structure among populations followed an isolation-by-distance pattern, suggesting restricted movement among remnant populations. At the individual level, greater heterozygosity was associated with reduced probability of infection. Loss of genetic diversity in remnant populations that survived chytridiomycosis epidemics does not appear to be a threat to L. v. alpina. We suggest several factors underpinning maintenance of genetic diversity: (1) remnant populations have remained large enough to avoid losses of genetic diversity; (2) many individuals in the population are able to breed once before succumbing to disease; and (3) juveniles in the terrestrial environment have low exposure to Bd, providing an annual ‘reservoir’ of genetic diversity. The association between individual heterozygosity and infection status suggests that, while other work has shown all breeding adults are typically killed by Bd, males with greater heterozygosity may survive longer and obtain fitness benefits through extended breeding opportunities. Our results highlight the critical role of life history in mitigating the impacts of Bd infection for some amphibian species, but we infer that increased isolation as a result of disease-induced population extirpations will enhance population differentiation and thus biogeographic structure

The Distribution and Origin of Bottom Sediments in Timbalier Bay, Louisiana, and the Adjacent Offshore Area

Paper by James I. Jones and Sam E. William

Spin nutation and polarization in ballistic semiconductor nanostructures

The definitions of spin orientation and polarization vectors are introduced within the particle density matrix of scattering states in leads. It is shown that spin-density vector can be defined by the product of the spin orientation vector, being a unit direction vector, and the charge density, corresponding to the amplitude of the spin-density vector, experimentally observable by a spatial charge modulation measurement. When an electron transports through a ballistic semiconductor nanostructure, due to quantum interference of two spin eigenmodes, the electron spin generally undergoes nutation on its precession around the effective magnetic field resulting from spin-orbit interactions. The nutation of electron spin is found to be crucial for spin polarization in the quantum transport. When one of two spin-dependent channels in leads is evanescent, electron spin is shown to be fully polarized for distance from the interface larger than the spin precession length

Bamboo Hermitage [Editors\u27 Introduction]

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Performance, Carcass and Organ Weights Characteristics of Finishing Broiler Chickens Fed Pro-Vitamin A ( UMUCASS 36) Cassava Meal

A 4-week study was conducted using 120 unsexed Anak strain broilers to determine the performance, carcass and internal organs characteristics of finishing broilers fed unpeeled and  peeled fermented pro-vitamin A cassava meal as total replacement for maize. Fresh bio-fortified pro-vitamin A cassava was harvested and divided into two batches. The first batch was peeled and the second batch was unpeeled. Both were soaked separately in a plastic vat containing clean water and allowed to ferment for 72 hours. Thereafter, they were washed with clean water, sundried and milled to produce i. peeled fermented pro-vitamin A cassava tuber meal (PFPC). ii. Unpeeled fermented pro-vitamin A cassava tuber meal (UFPC). The broilers were divided into three groups and fed diets containing 100% maize T1 (control) as the source of energy, while T2 and T3 contained 100% unpeeled and peeled fermented pro-vitamin A cassava as the source of energy respectively. Each group was replicated four times with 10 birds per replicate in a completely Randomized Design (CRD). Feed and water were provided ad libitum for the period. Result showed that final body weight, daily weight gain and breast weight of the control were significantly (p 0.05) higher than UFPC and PFPC groups. The treatment had no significant (p 0.05) effect on the internal organs of the birds. Abdominal fat of the PFPC group was significantly (p 0.05) higher than the control and UFPC. The results of this study revealed that unpeeled and peeled fermented pro-vitamin A cassava meal can completely replaced maize in the diets of finishing broilers. Keywords: Broiler, performance, pro-vitamin A cassav

About Our Contributors

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