The Timing of Bid Placement and Extent of Multiple Bidding: An Empirical Investigation Using eBay Online Auctions

Online auctions are fast gaining popularity in today's electronic commerce. Relative to offline auctions, there is a greater degree of multiple bidding and late bidding in online auctions, an empirical finding by some recent research. These two behaviors (multiple bidding and late bidding) are of ``strategic'' importance to online auctions and hence important to investigate. In this article we empirically measure the distribution of bid timings and the extent of multiple bidding in a large set of online auctions, using bidder experience as a mediating variable. We use data from the popular auction site \url{www.eBay.com} to investigate more than 10,000 auctions from 15 consumer product categories. We estimate the distribution of late bidding and multiple bidding, which allows us to place these product categories along a continuum of these metrics (the extent of late bidding and the extent of multiple bidding). Interestingly, the results of the analysis distinguish most of the product categories from one another with respect to these metrics, implying that product categories, after controlling for bidder experience, differ in the extent of multiple bidding and late bidding observed in them. We also find a nonmonotonic impact of bidder experience on the timing of bid placements. Experienced bidders are ``more'' active either toward the close of auction or toward the start of auction. The impact of experience on the extent of multiple bidding, though, is monotonic across the auction interval; more experienced bidders tend to indulge ``less'' in multiple bidding.Comment: Published at http://dx.doi.org/10.1214/088342306000000123 in the Statistical Science (http://www.imstat.org/sts/) by the Institute of Mathematical Statistics (http://www.imstat.org

Flight test evaluation of a method to determine the level flight performance of a propeller-driven aircraft

The overall drag of the aircraft is expressed in terms of the measured increment of power required to overcome a corresponding known increment of drag, which is generated by a towed drogue. The simplest form of the governing equations, D = delta D SHP/delta SHP, is such that all of the parameters on the right side of the equation can be measured in flight. An evaluation of the governing equations has been performed using data generated by flight test of a Beechcraft T-34B. The simplicity of this technique and its proven applicability to sailplanes and small aircraft is well known. However, the method fails to account for airframe-propulsion system

Two new species of Trachyandra sect. Liriothamnus (Xanthorrhoeaceae, Asphodeloideae) from the Western and Eastern Cape Provinces of South Africa

Trachyandra eriocarpa and T. bulbosa are two new species from Northern and Eastern Cape Provinces of South Africa. They are placed in T. sect. Liriothamnus based on their wiry roots, the cataphylls not forming membranous collars, and the remains of the outer leaves forming a fibrous collar. Trachyandra eriocarpa from the Great Winterberg in Eastern Cape is recognised by its unusual, villous ovary and capsules; and T. bulbosa from north of Springbok in Northern Cape by the irregular, bulbous rhizome, microscopically puberulous leaves and maculate tepals.Web of Scienc

A global infrageneric classification system for the genus Crotalaria (Leguminosae) based on molecular and morphological evidence

Crotalaria is a large genus of 702 species with its centre of diversity in tropical Africa and Madagascar and secondary radiations in other parts of the world. The current infrageneric classification system is based on morphological and morphomet- ric studies of the African taxa only and is here re-evaluated using a phylogenetic approach. DNA sequences derived from the nuclear ITS and the plastid matK, psbA-trnH and rbcLa markers were analyzed using parsimony and model-based (Bayesian) approaches. The resultant molecular phylogeny allowed for a new interpretation of diagnostically important morphological characters, including specialisations of the calyx, keel, standard petal and style, which are variously convergent in several unrelated infrageneric groups. Of particular interest is the congruence between the new phylogeny and the distribution of stand- ard petal callosity types. A sectional classification system for the entire genus is proposed for the first time. The new system that is formalised here comprises eleven sections: Amphitrichae, Calycinae, Crotalaria, Geniculatae, Glaucae, Grandiflorae, Hedriocarpae, Incanae, Schizostigma, Borealigeniculatae and Stipulosae. Sectional limits of the Geniculatae, Calycinae and Crotalaria are modified. The subsections Stipulosae, Glaucae and Incanae are raised to sectional level, while some groups previously recognized as subsections are abandoned due to non-monophyly (subsections Chrysocalycinae, Hedriocarpae, Macrostachyae and Tetralobocalyx). Two new sections are recognized, Amphitrichae and Borealigeniculatae.Web of Scienc

Molecular and morphological analysis of subfamily Alooideae (Asphodelaceae) and the inclusion of chortolirion in aloe

Asphodelaceae subfam. Alooideae (Asparagales) currently comprises five genera, four of which are endemic to southern Africa. Despite their importance in commercial horticulture the evolutionary relationships among the genera are still incompletely understood. This study examines phylogenetic relationships in the subfamily using an expanded molecular sequence dataset from three plastid regions (matK, rbcLa, trnH-psbA) and the first subunit of the nuclear ribosomal internal transcribed spacer (ITS1). Sequence data were analysed using maximum parsimony and Bayesian statistics, and selected morphological traits were mapped onto the molecular phylogeny. Haworthia is confirmed as being polyphyletic, comprising three main clades that largely correlate with current subgeneric circumscriptions. Astroloba and Gasteria are evidently each monophyletic and sister respectively to Astroloba and H. subg. Robustipedunculares. Chortolirion is shown to be deeply nested within Aloe and is formally included in that genus. Aloe itself is clearly polyphyletic, with the dwarf species A. aristata allied to Haworthia subg. Robustipedunculares. The taxonomic implications of these findings are examined but branch support at critical lower nodes is insufficient at this stage to justify implementing major taxonomic changes

The effect of night splints in the treatment of plantar fasciitis: a systematic literature review

Objective: To investigate the use of night splints for the treatment of plantar fasciitis and the current evidence regarding their ability to affect symptoms associated with plantar fasciitis.https://jdc.jefferson.edu/dptcapstones/1009/thumbnail.jp