Entry and market selection of firms: a laboratory study

We study competition in experimental markets in which two incumbents face entry by three other firms. Our treatments vary with respect to three factors: sequential vs. block or simultaneous entry, the cost functions of entrants and the amount of time during which incumbents are protected from entry. Before entry incumbents are able to collude in all cases. When all firms' costs are the same entry always leads consumer surplus and profits to their equilibrium levels. When entrants are more efficient than incumbents, entry leads consumer surplus to equilibrium. However, total profits remain below equilibrium, due to the fact that the inefficient incumbents produce too much and efficient entrants produce too little. Market behavior is satisfactory from the consumers' standpoint, but does not yield adequate signals to other potential entrants. These results are not affected by whether entry is simultaneous or sequential. The length of the incumbency phase does have some subtle effects.

Laboratory Study of Structural Behavior of Alternative Dowel Bars, April 2006

Load transfer across transverse joints has always been a factor contributing to the useful life of concrete pavements. For many years, round steel dowels have been the conventional load transfer mechanism. Many problems have been associated with the round steel dowels. The most detrimental effect of the steel dowel is corrosion. Repeated loading over time also damages joints. When a dowel is repeatedly loaded over a long period of time, the high bearing stresses found at the top and bottom edge of a bar erode the surrounding concrete. This oblonging creates multiple problems in the joint. Over the past decade, Iowa State University has performed extensive research on new dowel shapes and materials to mitigate the effects of oblonging and corrosion. This report evaluates the bearing stress performance of six different dowel bar types subjected to two different shear load laboratory test methods. The first load test is the AASHTO T253 method. The second procedure is an experimental cantilevered dowel test. The major objective was to investigate and improve the current AASHTO T253 test method for determining the modulus of dowel support, k0. The modified AASHTO test procedure was examined alongside an experimental cantilever dowel test. The modified AASHTO specimens were also subjected to a small-scale fatigue test in order to simulate long-term dowel behavior with respect to concrete joint damage. Loss on ignition tests were also performed on the GFRP dowel specimens to determine the resin content percentage. The study concluded that all of the tested dowel bar shapes and materials were adequate with respect to performance under shear loading. The modified AASHTO method yielded more desirable results than the ones obtained from the cantilever test. The investigators determined that the experimental cantilever test was not a satisfactory test method to replace or verify the AASHTO T253 method.

Duloxetine inhibits effects of MDMA ("ecstasy") in vitro and in humans in a randomized placebo-controlled laboratory study.

This study assessed the effects of the serotonin (5-HT) and norepinephrine (NE) transporter inhibitor duloxetine on the effects of 3,4-methylenedioxy-methamphetamine (MDMA, ecstasy) in vitro and in 16 healthy subjects. The clinical study used a double-blind, randomized, placebo-controlled, four-session, crossover design. In vitro, duloxetine blocked the release of both 5-HT and NE by MDMA or by its metabolite 3,4-methylenedioxyamphetamine from transmitter-loaded human cells expressing the 5-HT or NE transporter. In humans, duloxetine inhibited the effects of MDMA including elevations in circulating NE, increases in blood pressure and heart rate, and the subjective drug effects. Duloxetine inhibited the pharmacodynamic response to MDMA despite an increase in duloxetine-associated elevations in plasma MDMA levels. The findings confirm the important role of MDMA-induced 5-HT and NE release in the psychotropic effects of MDMA. Duloxetine may be useful in the treatment of psychostimulant dependence. TRIAL REGISTRATION: Clinicaltrials.gov NCT00990067.

Laboratory Study of Slurry Seal Coats, HR-185, Revised, 1978

Extensive programmed laboratory tests involving some 400 asphalt emulsion slurry seals (AESS) were conducted. Thirteen aggregates including nine Iowa sources, a quartzite, a synthetic aggregate (Haydite), a limestone stone from Nebraska, and a Chat aggregate from Kansas were tested in combination with four emulsions and two mineral fillers, resulting in a total of 40 material combinations. A number of meetings were held with the Iowa DOT engineers and 12 state highway departments that have had successful slurry seal experiences and records, and several slurry seal contractors and material and equipment suppliers were contacted. Asphalt emulsion slurry seal development, uses, characteristics, tests, and design methods were thoroughly reviewed in conjunction with Iowa's experiences through these meetings and discussions and through a literature search (covering some 140 articles and 12 state highway department specifications). It was found that, while asphalt emulsion slurry seals (when properly designed and constructed) can economically improve the quality and extend the life of existing pavement surface, experiences with them had been mixed due to the many material, slurry, and construction variables that affect their design, construction, and performance. The report discusses those variables identified during the course of the project and makes recommendations concerning design procedures, design criteria, specifications and the means of evaluating them.

Effects of Cement on Moisture Migration in Concrete, Phase A, Laboratory Study of Moisture Migration in Hardened Cement Paste, HR-141, 1972

The Columbus Laboratories of Battelle Memorial Institute is currently conducting a study of the effect of cement on moisture migration in concrete as related to the problem of D-cracking of portland cement concrete pavements. The study began on December 31, 1970, and is planned as a 3-year program. The work plan, approved by the policy committee of the members of the Iowa, Kansas, and Missouri highway departments and the Federal Highway Administration, is composed of four parts. The first phase (A) of the investigation concerned the movement of moisture into and from hardened cement pastes and the dimensional changes accompanying the moisture changes. Small slab specimens of hardened neat cement pastes were prepared from 32 different cements which were prepared at the same water/cement ratio and hydrated to the same maturity factor.

Laboratory Study of the Leachate from Crushed Portland Cement Concrete Base Material, MLR-96-04, 1999

Since the 1980s, the Iowa Department of Transportation has increased its use of recycled Portland Cement Concrete (PCC) as drainable base material below some new pavements. Water flowing out of the longitudinal drains on projects having recycled PCC drainable bases was found to have a high pH value. The high pH water impedes vegetation growth and becomes a contributing factor to soil erosion at the drain outlet. In addition, the high pH water contributes to the growth of crystalline deposits on the drain outlet wire mesh rodent guard and in some cases caused it to become completely blocked. This research determined which of three choices of recycled PCC drainable base material, gradation, and design would give the lowest pH value in the drain discharge water. The drainable base material having its fines separated out and placed as a 2-in. (5.1-mm) bottom layer, below the remaining coarse material, generally gave pH values around 11.2 while other designs tested gave pH values around 11.5.

Optimal slopes and speeds in uphill ski mountaineering: a laboratory study.

The purpose of this study was to estimate the energy cost of linear (EC) and vertical displacement (ECvert), mechanical efficiency and main stride parameters during simulated ski mountaineering at different speeds and gradients, to identify an optimal speed and gradient that maximizes performance. 12 subjects roller skied on a treadmill at three different inclines (10, 17 and 24 %) at three different speeds (approximately 70, 80 and 85 % of estimated peak heart rate). Energy expenditure was calculated by indirect calorimetry, while biomechanical parameters were measured with an inertial sensor-based system. At 10 % there was no significant change with speed in EC, ECvert and mechanical efficiency. At 17 and 24 % the fastest speed was significantly more economical. There was a significant effect of gradient on EC, ECvert and mechanical efficiency. The most economical gradient was the steepest one. There was a significant increase of stride frequency with speed. At steep gradients only, relative thrust phase duration decreased significantly, while stride length increased significantly with speed. There was a significant effect of gradient on stride length (decrease with steepness) and relative thrust phase duration (increase with steepness). A combination of a decreased relative thrust phase duration with increased stride length and frequency decreases ECvert. To minimize the energy expenditure to reach the top of a mountain and to optimize performance, ski-mountaineers should choose a steep gradient (~24 %) and, provided they possess sufficient metabolic scope, combine it with a fast speed (~6 km h(-1)).

The role of mindfulness in coping with recollections of acute stressors : a laboratory study

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A laboratory study of an inactivated bivalent iron restricted Salmonella enterica serovars Enteritidis and Typhimurium dual vaccine against Typhimurium challenge in chickens

A commercial inactivated iron restricted Salmonella Typhimurium and Salmonella Enterifidis vaccine was used to vaccinate chicks at I day and again at 4 weeks of age, with challenge by a high and a low dose of S. Typhimurium given either orally or by contact with seeder birds inoculated orally with a high dose of S. Typhimurium. In all three challenge regimes, the shedding of challenge strain was reduced significantly (p < 0.05) in vaccinated birds compared with unvaccinated controls. Vaccination reduced colonisation of internal organs after challenge by contact seeder birds. However, no effect of vaccination upon colonisation of internal organs after either high or low oral challenge was apparent. In conclusion, the data indicate that the vaccine should be a useful tool in the control of S. Typhimurium infection in chickens. (C) 2002 Elsevier Science B.V. All rights reserved.

A laboratory study on feeding plasticity of the shredder Sericostoma vittatum Rambur (Sericostomatidae)

Since litter input and availability of leaves in many streams is highly seasonal in Portugal, we investigated whether Sericostoma vittatum, a typical shredder, was able to grow using alternative food sources. To test this hypothesis we fed S. vittatum with Alnus glutinosa (alder, CPOM, coarse particulate organic matter), leaf powder from A. glutinosa and Acacia dealbata and FPOM (fine particulate organic matter) from a 5th and a > 6th order river, the macrophyte Myriophyllum aquaticum and biofilm. Growth in S. vittatum was significantly influenced by the food item given (ANOVA, P = 0.0082). The food item promoting the highest growth was A. glutinosa, in the form of FPOM (6.48% day(-1)) and CPOM (4.24% day(-1)); all other forms of FPOM and biofilm provided relatively low growth rates (0.77-1.77% day(-1)). The macrophyte M. aquaticum was also used as food source by S. vittatum and promoted intermediate growth (1.96% day(-1)). Neither nitrogen, phosphorus nor caloric content was correlated with growth. However, since higher growth was achieved with alder, in the form of CPOM and FPOM, we concluded that the chemical content of food was more important for S. vittatum than the physical form of such food. This may partially explain why shredders are able to survive when leaves are scarce in streams.

A laboratory study of the transfer of U-234 and U-238 during water-rock interactions in the Carnmenellis granite (Cornwall, England) and implications for the interpretation of field data

Laboratory time-scale experiments were conducted on gravels from the Carnmenellis granite, Cornwall, England, with the purpose of evaluating the release of natural uranium isotopes to the water phase. The implications of these results for the production of enhanced U-234/U-238 activity ratios in Cornish groundwaters are discussed. It is suggested that the U-234/U-238 lab data can be used to interpret activity ratios from Cornwall, even when the observed inverse relationship between dissolved U and U-234/U-238 in leachates/etchates is taken into account. (C) 2001 Elsevier B.V. Ltd. All rights reserved.

Laboratory study on the bioremediation of diesel oil contaminated soil from a petrol station

O objetivo do presente estudo foi investigar possíveis métodos para aumentar a taxa de biodegradação aeróbia de hidrocarbonetos (tratamentos ex-situ). Neste trabalho, processos de biorremediação foram aplicados a um solo arenoso com alto nível de contaminação ocasionada por um vazamento de um tanque de armazenamento de óleo diesel subterrâneo em um posto de combustíveis. Experimentos em escala laboratorial (respirômetros de Bartha) foram utilizados para avaliar a biodegradação do óleo diesel. Estímulo da biodegradação foi realizado utilizando-se as técnicas de bioestímulo (adição de soluções de nitrogênio e fósforo ou surfactante Tween 80) e de bioaumento (consórcio bacteriano isolado de um sistema de landfarming). Para investigar as interações entre os fatores otimizadores, e encontrar a melhor combinação entre esses agentes, o estudo foi baseado em um delineamento experimental fatorial completo. A eficiência de biodegradação foi simultaneamente medida com dois métodos: respirométrico (produção de CO2 microbiano) e cromatografia gasosa. Testes de toxicidade aguda com Daphnia similis foram aplicados para examinar a eficiência dos processos em termos de geração de produtos menos tóxicos. Resultados mostraram que todas as estratégias de biorremediação aceleraram a biorremediação natural do solo contaminado e os melhores resultados foram obtidos quando os tratamentos tinham adição de nutrientes. Dados respirométricos indicaram uma máxima mineralização de hidrocarbonetos de 19,8%, obtida com a combinação dos três agentes, com uma remoção de hidrocarbonetos totais de petróleo (TPH) de 45,5% em 55 dias de tratamento. No final dos experimentos, duas espécies predominantes de bactéria foram isoladas e identificadas como Staphylococcus hominis e Kocuria palustris.

Periodic sterility assessment of materials stored for up to 6 months at continuous microbial contamination risk: Laboratory study

An investigation was conducted to test the hypothesis that the storage time of packaging sterility has no effect on contamination susceptibility even under deliberate bacterial exposure (Serratia marcescens). No growth of the test microorganisms was identified in the experimental group in any of the storage intervals (7, 14, 28, 90, and 180 days). Current recommendations/guidelines suggest that contamination of packaging occurs only because of events. This study, done in vitro, supports these recommendations. Copyright (c) 2012 by the Association for Professionals in Infection Control and Epidemiology, Inc. Published by Elsevier Inc. All rights reserved.

Laboratory study of grouted macadams impregnated with mine waste geopolymeric binder

A new type of pavement has been gaining popularity over the last few years in Europe. It comprises a surface course with a semi-flexible material that provides significant advantages in comparison to both concrete and conventional asphalt, having both rut resistance and a degree of flexibility. It also provides good protection against the ingress of water to the foundation, since it has an impermeable surface. The semi-flexible material, generally known as grouted macadam, comprises an open-graded asphalt skeleton with 25% to 35% voids into which a cementitious slurry is grouted. This hybrid mixture provides good rut resistance and a surface highly resistant to fuel and oil spillage. Such properties allow it to be used in industrial areas, airports and harbours, where those situations are frequently associated with heavy and slow traffic. Grouted Macadams constitute a poorly understood branch of pavement technology and have generally been relegated to a role in certain specialist pavements whose performance is predicted on purely empirical evidence. Therefore, the main objectives of this project were related to better understanding the properties of this type of material, in order to predict its performance more realistically and to design pavements incorporating grouted macadam more accurately. Based on a standard mix design, several variables were studied during this project in order to characterise the behaviour of Grouted Macadams in general, and the influence of those variables on the fundamental properties of the final mixture. In this research project, one approach was used to the design of pavements incorporating Grouted Macadams: a traditional design method, based on laboratory determined of the stiffness modulus and the compressive strength.