Two sided markets, competitive bottlenecks and exclusive contracts

We provide a framework for analyzing two-sided markets that allows for different degrees of product differentiation on each side of the market. When platforms are viewed as homogenous by sellers but heterogeneous by buyers, we show that “competitive bottlenecks” arise endogenously. In equilibrium, platforms do not compete directly for sellers, instead choosing to compete indirectly by subsidizing buyers to join. Sellers are left with none of the gains from trade. Despite this, it is sellers who choose to purchase from multiple platforms (multihome). Finally, the role of exclusive contracts to prevent multihoming is explored

Missing Variables in Theories of Strategic Human Resource Management: Time, Cause, and Individuals

Much progress has been made with regard to theory building and application in the field of Strategic Human Resource Management (HRM) since Wright and McMahan’s (1992) critical review. While researchers have increasingly investigated the impact of HR on economic success within the Resource Based view of the firm, and have developed more middle level theories regarding the processes through which HR impacts firm performance, much work still needs to be done. This paper examines how future theorizing in SHRM should explore the concepts of time, cause, and individuals. Such consideration will drive more longitudinal research, more complex causal models, and consideration of multi-level phenomena

Anal signs of child sexual abuse: a case–control study

Background: There is uncertainty about the nature and specificity of physical signs following anal child sexual abuse. The study investigates the extent to which physical findings discriminate between children with and without a history of anal abuse.<p></p> Methods: Retrospective case note review in a paediatric forensic unit.<p></p> Cases: all eligible cases from 1990 to 2007 alleging anal abuse.<p></p> Controls: all children examined anally from 1998 to 2007 with possible physical abuse or neglect with no identified concern regarding sexual abuse. Fisher’s exact test (two-tailed) was performed to ascertain the significance of differences for individual signs between cases and controls. To explore the potential role of confounding, logistic regression was used to produce odds ratios adjusted for age and gender.<p></p> Results: A total of 184 cases (105 boys, 79 girls), average age 98.5 months (range 26 to 179) were compared with 179 controls (94 boys, 85 girls) average age 83.7 months (range 35–193). Of the cases 136 (74%) had one or more signs described in anal abuse, compared to 29 (16%) controls. 79 (43%) cases and 2 (1.1%) controls had >1 sign. Reflex anal dilatation (RAD) and venous congestion were seen in 22% and 36% of cases but <1% of controls (likelihood ratios (LR) 40, 60 respectively), anal fissure in 14% cases and 1.1% controls (LR 13), anal laxity in 27% cases and 3% controls (LR 10).<p></p> Novel signs seen significantly more commonly in cases were anal fold changes, swelling and twitching. Erythema, swelling and fold changes were seen most commonly within 7 days of last reported contact; RAD, laxity, venous congestion, fissure and twitching were observed up to 6 months after the alleged assault.<p></p> Conclusions: Anal findings are more common in children alleging anal abuse than in those presenting with physical abuse or neglect with no concern about sexual abuse. Multiple signs are rare in controls and support disclosed anal abuse

Orbital calculations and trapped radiation mapping

Flux and energy spectra code for orbital calculations and trapped radiation mappin

3D Photoionisation Modelling of NGC 6302

We present a three-dimensional photoionisation and dust radiative transfer model of NGC 6302, an extreme, high-excitation planetary nebula. We use the 3D photoionisation code Mocassin} to model the emission from the gas and dust. We have produced a good fit to the optical emission-line spectrum, from which we derived a density distribution for the nebula. A fit to the infrared coronal lines places strong constraints on the properties of the unseen ionising source. We find the best fit comes from using a 220,000 K hydrogen-deficient central star model atmosphere, indicating that the central star of this PN may have undergone a late thermal pulse. We have also fitted the overall shape of the ISO spectrum of NGC 6302 using a dust model with a shallow power-law size distribution and grains up to 1.0 micron in size. To obtain a good fit to the infrared SED the dust must be sufficiently recessed within the circumstellar disk to prevent large amounts of hot dust at short wavelengths, a region where the ISO spectrum is particularly lacking. These and other discoveries are helping to unveil many properties of this extreme object and trace it's evolutionary history.Comment: 8 pages, 4 figures; for the proceedings of "Asymmetric Planetary Nebuale IV," R. L. M. Corradi, A. Manchado, N. Soker ed

Solar and geothermal energy for low-carbon space heating and energy independence.

In developed countries, space heating is highly dependent on fossil fuels consumption. Also, the non-renewable fuels combustion emits CO2 which is claimed to impact the most on greenhouse effect. The utilization of Renewable Energy Sources (RES) for space heating, instead of fossil fuels, has been found to be feasible for systems’ greater energy independence and reduction in CO2 emissions. Solar Assisted Ground Source Heat Pump (SAGSHP) systems are a promising technology which can be used to accomplish the above framed target. A mathematic model of a SAGSHP system was built and a parametric analysis for Birmingham which is a city located in the UK’s West Midlands was conducted. Two scenarios based on two different dwellings were investigated, the one was a house recently erected and the other was a refurbished house. As regards the new house, simulation results showed that the utilized energy for space heating and Domestic Hot Water (DHW) can vary from 33% up to 73% RES dependent and, at the same time, electricity generation can be 2.21 times higher than the system’s demand. As regards the energy renovated dwelling, the RES contribution to the delivered heat was found to be between the 33% and 63%, while the electricity generation did not result in any surplus energy from the consumed. Finally, by making use of SAGSHP system instead of a natural Gas boiler, the reduction of CO2 emissions was found to be between 300kg/year and 2,170kg/year for the new building and from 245kg/year up to 3,221kg/year for the refurbished house, respectively. In both cases, SAGSHP systems proved to be a feasible practice for greater energy independence from non-renewable energy sources with substantial positive impact on the greenhouse gasses emissions