Revenue monotonicity in deterministic, dominant-strategy combinatorial auctions

In combinatorial auctions using VCG, a seller can sometimes increase revenue by dropping bidders. In this paper we investigate the extent to which this counterintuitive phenomenon can also occur under other deterministic, dominant-strategy combinatorial auction mechanisms. Our main result is that such failures of “revenue monotonicity” can occur under any such mechanism that is weakly maximal—meaning roughly that it chooses allocations that cannot be augmented to cause a losing bidder to win without hurting winning bidders—and that allows bidders to express arbitrary known single-minded preferences. We also give a set of other impossibility results as corollaries, concerning revenue when the set of goods changes, false-name-proofness, and the core.¹     

Whither subliminal psychodynamic activation? A reply to Silverman.

The authors reply to comments by L. H. Silverman (see record 1982-21579-001) on their earlier criticisms (see record 1980-26153-001) of subliminal symbiotic stimulation as a clinical adjunct to systematic desensitization. The authors contend that Silverman credits them with an overly nebulous "challenge" that was not made, and cites new data that purportedly contradict this overgeneralized conclusion. None of this "contradictory" evidence deals with desensitization or any other treatment for phobic anxiety. The alternative explanations he derives from these new data are based on an arbitrary and simplistic method of data aggregation that lacks consistency across investigations. The resulting selective bias severely reduces the explanatory power of these alternative possibilities and does not negate the authors' contention that stimulation of unconscious merging fantasies is superfluous in desensitization. (9 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Rubella vaccination and congenital rubella syndrome in Western Australia

OBJECTIVE: To review the incidence of congenital rubella syndrome (CRS) and the acceptance of schoolgirl rubella vaccination in Western Australia (WA), and to determine whether any groups in the community are at increased risk of having a child affected by CRS. DESIGN: Review of records of the WA Birth Defects Registry for cases of CRS; survey of obstetricians for terminations of pregnancy for maternal rubella infection; survey of schoolgirls eligible for the 1991 annual rubella vaccination campaign; review of Perth Immunisation Clinic and rural community and child health records; review of the rubella immune status of women tested antenatally. MAIN OUTCOME MEASURES: The incidence rate of CRS per 10,000 live births in WA 1980-1990; the incidence of rubella-associated terminations of pregnancy during 1990 and 1991; trends in rubella vaccine acceptance among WA schoolgirls between 1971 and 1991; and the proportion of women attending antenatal clinics who showed satisfactory immunity against rubella, stratified by country of birth. RESULTS: The incidence rate of CRS in WA remains below 2 cases per 10,000 live births. Approximately 86% of Perth schoolgirls have been vaccinated against rubella. Rubella vaccine acceptance fell in some country areas during the late 1980s, but is now returning to acceptable levels. Women born in Asia are at greater risk of having a baby affected by CRS than women born in Australia. Babies with CRS may be born to women who have previously been vaccinated against rubella. CONCLUSIONS: The incidence of CRS has fallen dramatically since the introduction of the schoolgirl vaccination program, but there is still a need for mechanisms to identify and vaccinate non-immune women.     

Cognitive spatial processing and the regulation of posture.

Investigated the interaction between postural regulation and spatial processing by having 24 college students perform L. R. Brooks's (see record 1968-04936-001) spatial and nonspatial memory tasks either while sitting or while maintaining a difficult standing balance position. The balance task disrupted spatial but not nonspatial memory performance. Balance steadiness during spatial and nonspatial memory conditions did not differ. Results suggest that cognitive spatial processing may rely on neural mechanisms that are also required for the regulation of posture. Findings support the idea that spatial processing may rely on phylogenetically older systems. (26 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

The complexity of stochastic games

We consider the complexity of stochastic games—simple games of chance played by two players. We show that the problem of deciding which player has the greatest chance of winning the game is in the class NP co-NP.     

Susceptibility of stored product insects to high concentrations of ozone at different exposure intervals

Ozone is a highly reactive gas with insecticidal activity. Past studies have indicated that ozone technology has potential as a management tool to control insect pests in bulk grain storage facilities. The objective of this study was to determine the efficacy of short periods of exposure to high ozone concentrations to kill all life stages of red flour beetle (Tribolium castaneum (Herbst)) (Coleoptera: Tenebrionidae), and Indianmeal moth (Plodia interpunctella (Hübner)) (Lepidoptera: Pyralidae), adult maize weevil (Sitophilus zeamais (Motsch.)) (Coleoptera: Curculionidae) and adult rice weevil (S. oryzae (L)) (Coleoptera: Curculionidae). Insects were treated with six ozone concentrations between 50 and 1800 ppm. The specific objective was to determine minimal time needed to attain 100% mortality. The most ozone-tolerant stages of T. castaneum were pupae and eggs, which required a treatment of 180 min at 1800 ppm ozone to reach 100% mortality. Eggs of P. interpunctella also required 180 min at 1800 ppm ozone to reach 100% mortality. Ozone treatments of 1800 ppm for 120 min and 1800 ppm for 60 min were required to kill all adult S. zeamais and adult S. oryzae, respectively. The results indicate that high ozone concentrations reduce the treatment times significantly over previously described results. Our results also provide new baseline information about insect tolerance to ozone treatment.     

Fuel composition and secondary organic aerosol formation: gas-turbine exhaust and alternative aviation fuels

A series of smog chamber experiments were performed to investigate the effects of fuel composition on secondary particulate matter (PM) formation from dilute exhaust from a T63 gas-turbine engine. Tests were performed at idle and cruise loads with the engine fueled on conventional military jet fuel (JP-8), Fischer-Tropsch synthetic jet fuel (FT), and a 50/50 blend of the two fuels. Emissions were sampled into a portable smog chamber and exposed to sunlight or artificial UV light to initiate photo-oxidation. Similar to previous studies, neat FT fuel and a 50/50 FT/JP-8 blend reduced the primary particulate matter emissions compared to neat JP-8. After only one hour of photo-oxidation at typical atmospheric OH levels, the secondary PM production in dilute exhaust exceeded primary PM emissions, except when operating the engine at high load on FT fuel. Therefore, accounting for secondary PM production should be considered when assessing the contribution of gas-turbine engine emissions to ambient PM levels. FT fuel substantially reduced secondary PM formation in dilute exhaust compared to neat JP-8 at both idle and cruise loads. At idle load, the secondary PM formation was reduced by a factor of 20 with the use of neat FT fuel, and a factor of 2 with the use of the blend fuel. At cruise load, the use of FT fuel resulted in no measured formation of secondary PM. In every experiment, the secondary PM was dominated by organics with minor contributions from sulfate when the engine was operated on JP-8 fuel. At both loads, FT fuel produces less secondary organic aerosol than JP-8 because of differences in the composition of the fuels and the resultant emissions. This work indicates that fuel reformulation may be a viable strategy to reduce the contribution of emissions from combustion systems to secondary organic aerosol production and ultimately ambient PM levels.     

Changes in acid tolerance of Lactococcus lactis during growth at constant pH

Cells of Lactococcus lactis MG1363 growing in batch culture in TYG (tryptone, yeast extract, glucose) medium at constant pH 7.0 became gradually more acid sensitive shortly after inoculation until a point of maximum sensitivity was reached in early log-phase. The acid tolerance then gradually increased in the mid- and late-log phase until maximum tolerance was reached at the onset of stationary phase. This pattern has been termed the growth-phase acid tolerance. The variation in acid tolerance seen in pH 7.0 grown cells of L. lactis MG1363 did not result from changes in internal pH or membrane H+ ATPase activity levels. Neither the amount of glucose present during mid-log phase nor the amount of lactate produced by the cells correlated with the pattern of the log-phase acid tolerance. Cells grown in partially spent TYG medium showed a reduced growth rate and increased acid tolerance compared to cells grown in fresh TYG medium. Supplementing the spent medium with tryptone or yeast extract or both restored the growth rate and cells became more sensitive to acid. Fractionation of tryptone yielded a fraction which stimulated the growth of MG1363 in partially spent medium and delayed the acquisition of acid tolerance. The active compound(s) has a putative molecular weight of about 1 kDa and was partially degraded by papain and trypsin.     

Properties of new nanocomposite triblock copolymer gels based on expandable graphite

In this work, we investigated the effect of expandable graphite (EG) on the property of triblock copolymer prepared from a poly(styrene‐b‐(ethylene‐co‐butylene)‐b‐styrene) (SEBS) imbibed with an EB‐compatible hydrocarbon oil. The rheological properties showed that at a temperature between 30 and 40°C below the gel point, the triblock copolymer gels had a dynamic storage modulus (G′) greater than loss modulus (G‵), thereby indicating that at ambient temperature, a physical network is still present in spite of the addition of nanoparticles. Dynamic rheological measurements of the resultant nanocomposite triblock copolymer gels confirmed that the addition of EG affects the linear viscoelastic properties and maximum operating temperature of the parent triblock copolymer gels. The mechanical properties showed only marginal increase, which can be attributed to the poor dispersion that leads to agglomeration of particle into micrometer size stacks, and thus the particles behave only as inorganic fillers. The morphology and X‐ray diffraction revealed that the EG used to generate nanocomposite triblock copolymer gels is dispersed generally within the swollen copolymer and/or solvent. POLYM. ENG. SCI., 2008. © 2008 Society of Plastics Engineers