633 research outputs found
Strategy Complexity of Concurrent Safety Games
Get PDFWe consider two player, zero-sum, finite-state concurrent reachability games, played for an infinite number of rounds, where in every round, each player simultaneously and independently of the other players chooses an action, whereafter the successor state is determined by a probability distribution given by the current state and the chosen actions. Player 1 wins iff a designated goal state is eventually visited. We are interested in the complexity of stationary strategies measured by their patience, which is defined as the inverse of the smallest non-zero probability employed. Our main results are as follows: We show that: (i) the optimal bound on the patience of optimal and epsilon-optimal strategies, for both players is doubly exponential; and (ii) even in games with a single non-absorbing state exponential (in the number of actions) patience is necessary
Faster Monte-Carlo Algorithms for Fixation Probability of the Moran Process on Undirected Graphs
Get PDFEvolutionary graph theory studies the evolutionary dynamics in a population structure given as a connected graph. Each node of the graph represents an individual of the population, and edges determine how offspring are placed. We consider the classical birth-death Moran process where there are two types of individuals, namely, the residents with fitness 1 and mutants with fitness r. The fitness indicates the reproductive strength. The evolutionary dynamics happens as follows: in the initial step, in a population of all resident individuals a mutant is introduced, and then at each step, an individual is chosen proportional to the fitness of its type to reproduce, and the offspring replaces a neighbor uniformly at random. The process stops when all individuals are either residents or mutants. The probability that all individuals in the end are mutants is called the fixation probability, which is a key factor in the rate of evolution. We consider the problem of approximating the fixation probability. The class of algorithms that is extremely relevant for approximation of the fixation probabilities is the Monte-Carlo simulation of the process. Previous results present a polynomial-time Monte-Carlo algorithm for undirected graphs when is given in unary. First, we present a simple modification: instead of simulating each step, we discard ineffective steps, where no node changes type (i.e., either residents replace residents, or mutants replace mutants). Using the above simple modification and our result that the number of effective steps is concentrated around the expected number of effective steps, we present faster polynomial-time Monte-Carlo algorithms for undirected graphs. Our algorithms are always at least a factor O(n^2/log n) faster as compared to the previous algorithms, where n is the number of nodes, and is polynomial even if r is given in binary. We also present lower bounds showing that the upper bound on the expected number of effective steps we present is asymptotically tight for undirected graphs
Domestic hot water in a dorm building
No full textThis study examines the domestic hot water consumption of a Danish dorm building with 50 residens, located in Aalborg. The aim of the study is to investigate consumption patterns regarding domestic hot water, and to investigate the impact that the circulation system has on the energy consumptions and energy losses in the domestic hot water system. The average, typical domestic hot water consumption was \SI{47,1}{L/person/day}, equivalent to \SI{419,4}{L/m^2/year}. In general, the domestic hot water consumption was found to be evenly distributed throughout most of the day, while typical week days also have a morning peak between 07:00 - 09:00.The circulation system was to found to have a major impact on the efficiency of the domestic hot water system, by consuming between 28,19 - \SI{49,28}{\%} of the district heating delivered to the domestic hot water system. Furthermore, the circulation system leads to a low utilization of the delivered district heating, corresponding to an average temperature difference of 15,38 - \SI{16,08}{\degree C}, between the delivered and consumed district heating.The efficiency of the domestic hot water system was estimated to 33,56 - \SI{36,67}{\%}, including energy for circulation losses, while the efficiency of the domestic hot water production alone was estimated to 44,56 - \SI{66,22}{\%}, excluding circulation losses. This shows that circulation systems can have a big impact on the overall efficiency of domestic hot water systems in dwellings such as the examined property
Shifts in coding properties and maintenance of information transmission during adaptation in barrel cortex
Get PDF12 pages, 6 figures.-- PMID: 17253902 [PubMed].-- PMCID: PMC1779810.Neuronal responses to ongoing stimulation in many systems change over time, or "adapt". Despite the ubiquity of adaptation, its effects on the stimulus information carried by neurons are often unknown. Here we examine how adaptation affects sensory coding in barrel cortex. We used spike-triggered covariance analysis of single-neuron responses to continuous, rapidly varying vibrissa motion stimuli, recorded in anesthetized rats. Changes in stimulus statistics induced spike rate adaptation over hundreds of milliseconds. Vibrissa motion encoding changed with adaptation as follows. In every neuron that showed rate adaptation, the input–output tuning function scaled with the changes in stimulus distribution, allowing the neurons to maintain the quantity of information conveyed about stimulus features. A single neuron that did not show rate adaptation also lacked input–output rescaling and did not maintain information across changes in stimulus statistics. Therefore, in barrel cortex, rate adaptation occurs on a slow timescale relative to the features driving spikes and is associated with gain rescaling matched to the stimulus distribution. Our results suggest that adaptation enhances tactile representations in primary somatosensory cortex, where they could directly influence perceptual decisions.[Author summary] Neuronal responses to continued stimulation change over time, or "adapt". Adaptation can be crucial to our brain's ability to successfully represent the environment: for example, when we move from a dim to a bright scene adaptation adjusts neurons' response to a given light intensity, enabling them to be maximally sensitive to the current range of stimulus variations. We analyzed how adaptation affects sensory coding in the somatosensory “barrel” cortex of the rat, which represents objects touched by the rat's whiskers, or vibrissae. Whiskers endow these nocturnal animals with impressive discrimination abilities: a rat can discern differences in texture as fine as we can distinguish using our fingertips. Neurons in the somatosensory cortex represent whisker vibrations by responding to “kinetic features”, particularly velocity fluctuations. We recorded responses of barrel cortex neurons to carefully controlled whisker motion and slowly varied the overall characteristics of the motion to provide a changing stimulus “context”. We found that stimulus–response relationships change in a particular way: the “tuning functions” that predict a neuron's response to fluctuations in whisker motion rescale according to the current stimulus distribution. The rescaling is just enough to maintain the information conveyed by the response about the stimulus.This work was supported by Human Frontier Science Program grant RG0043/2004-C (to MM and MED), European Community Marie Curie fellowship (to MM and MED), European Community Marie Curie International Reintegration grant MIRG-CT-2004–511273 (to MM), European Community grant IST-2000–28127 (to MED), Telethon Foundation grant GGP02459 (to MED), a grant from Ministero per l'Istruzione, l'Università e la Ricerca (to MED), a grant from the Italian Institute of Technology (to MED), a Royal Society Joint Project grant (to RSP and MM), a Royal Society Research grant (to RSP), a Human Frontier Science Program short-term fellowship (to ALF), a Sloan Foundation award (to ALF), and a Burroughs-Wellcome Foundation Career Award at the Scientific Interface (to ALF). MM is a Ramón y Cajal Research Fellow (Spanish Ministry of Education).Peer reviewe
Steven Shapin
No full textWhat does it mean to be an academic? A public intellectual? What is the role of the universities today? Who better to ask than the people who for decades have worked, taught, struggled and lived in these places. Steven Shapin is the Franklin L. Ford Research Professor of the History of Science at Harvard University. He was part of the Science Studies Unit at Edinburgh University in the 1970s and went on to co-author the influential Leviathan and the Air-Pump: Hobbes, Boyle, and the Experimental Life. In this book you can read about his journey through the heydays of Science Studies and his thoughts on the future of universities. In the Questions & Afthoughts series you will meet some of the finest and most distinguished senior professors—you will meet living history. They are interviewed by young graduate students, who are eager to learn from past experiences of trial and error in academia, both professionally and personally.What does it mean to be an academic? A public intellectual? What is the role of the universities today? Who better to ask than the people who for decades have worked, taught, struggled and lived in these places. Steven Shapin is the Franklin L. Ford Research Professor of the History of Science at Harvard University. He was part of the Science Studies Unit at Edinburgh University in the 1970s and went on to co-author the influential Leviathan and the Air-Pump: Hobbes, Boyle, and the Experimental Life. In this book you can read about his journey through the heydays of Science Studies and his thoughts on the future of universities. In the Questions & Afthoughts series you will meet some of the finest and most distinguished senior professors—you will meet living history. They are interviewed by young graduate students, who are eager to learn from past experiences of trial and error in academia, both professionally and personally
Future-oriented Seafood Markets: Economic dimensions, ecological compatibility and social aspects of fisheries and aquacultures
No full text No abstracts are to be cited without prior reference to the author. Converners: Cornelia Kreiss (Germany), Rasmus Nielsen (Denmark).CM 2018/L:34. Being in the stranglehold of conservationists. Stakeholders perceptions on the stagnating German aquaculture production. Antje Gimpel, Tobias LasnerCM 2018/L:643. Moving to a new target group? conclusions from comprehensive consumer studies of the PrimeFish project for the seafood industry. Matullat I., Mora C., Menozzi D., Sogari G., Nguyen T.T., Hagen B., Carcagnì A., Cubero Dudinskaya E., Guido D., Untilov O., Ganassali S.CM 2018/L:90. Sustainability knowledge to sustainable fish choice: consumer based insights from emerging markets. Mohammed Ziaul Hoque, Jinghua Xie, Ph.D, Øystein Myrland, Ph.DCM 2018/L:512. Fishing gears’ effect on ex-vessel fish prices. Tim Cashion, U. Rashid SumailaCM 2018/L:205. The potential of small scale and traditional firms in fisheries and aquaculture. Daurès Fabienne, Girard Sophie, Lasner Tobias, Goti LeyreCM 2018/L:585. The theory of change underpinning seafood ecolabelling tested through stock assessments. Catherine S. Longo, Ashleigh Arton, Annette Scheffer, Francis NeatCM 2018/L:419. Consumer preference heterogeneity and preference segmentation: the case of eco-labeled salmon in Danish retail sales. Isaac Ankamah-Yeboah, Frank Asche, Julia Bronnmann, Max Nielsen, Rasmus NielsenCM 2018/L:409. Is whitefish just white? a comparison of production costs and substitution of wild and farmed whitefish. Cornelia Kreiss, Rasmus Nielsen, Giap V. Nguyen, Sarah Simons, Tobias LasnerCM 2018/L:287. The young consumers of fish products –the determinants of purchasing processes. Adam Mytlewski, Tomasz KulikowskiCM 2018/L:360. Transnational localism: market practices of small scale fishers in the Mediterranean. Jerneja PencaCM 2018/L:462. Fisheries eco-certification: a large-scale societal experiment? Kochalski, SCM 2018/L:93. What should be recognized and rewarded in sustainable fisheries designations? fish harvester perspectives and preferences in Newfoundland and Labrador. Courtenay E. Parlee, Paul Foley, Erin CarruthersCM 2018/L:262. Teleconnection of cod stocks in the world market. Camilla Sguotti, Christian Möllmann, Andries RichterCM 2018/L:365. Estimating the impacts of common fisheries policy implementation to North Sea demersal fisheries using a bioeconomic mixed fisheries model. Marc H. Taylor, Alexander Kempf, Thomas Brunel, Clara Ulrich, Youen Vermard, Dorleta GarciaCM 2018/L:321. Game theory applications to Baltic Sea multispecies and multi-fleet fisheries under climate variability. Sezgin Tunca, Martin Lindegren, Lars-Ravn Jonsen, Marko Lindroos</p
The effect of cypermethrin and copper on Daphnia magna
No full textInsecticides and heavy metals are frequently distributed in the environment, but few studies have assessed the joint toxicity of the mixture of such substances. This project focused on two toxicants that occur to-gether in the aquatic environment as a result of human activities. The chemicals chosen were copper, an abundant toxicant in sewage sludge, and cypermethrin the active compound of many insecticides. This report investigate the combined effect of cypermethrin and copper on Daphnia magna. The acute toxicity was investigated on D. magna in a 48 hour immobilisation test. The experiments were conducted to test the effects of the two toxicants separately and in a mixture. We found individual EC50 values of 125±22 μg/L and 0.87±0.12 μg/L for copper and cypermethrin, respectively, each corresponding to 1 TU (Toxic unit). A mixture of copper and cypermethrin (30:70) gave an EC50 value of 0.685±0.137 TU. These results indicate a more-than-additive mixture toxicity for copper and cypermethrin according to the concentration addition model, but owing to high uncertainties in the experiment this cannot be conclusively interpreted as synergism.Insecticides and heavy metals are frequently distributed in the environment, but few studies have assessed the joint toxicity of the mixture of such substances. This project focused on two toxicants that occur to-gether in the aquatic environment as a result of human activities. The chemicals chosen were copper, an abundant toxicant in sewage sludge, and cypermethrin the active compound of many insecticides. This report investigate the combined effect of cypermethrin and copper on Daphnia magna. The acute toxicity was investigated on D. magna in a 48 hour immobilisation test. The experiments were conducted to test the effects of the two toxicants separately and in a mixture. We found individual EC50 values of 125±22 μg/L and 0.87±0.12 μg/L for copper and cypermethrin, respectively, each corresponding to 1 TU (Toxic unit). A mixture of copper and cypermethrin (30:70) gave an EC50 value of 0.685±0.137 TU. These results indicate a more-than-additive mixture toxicity for copper and cypermethrin according to the concentration addition model, but owing to high uncertainties in the experiment this cannot be conclusively interpreted as synergism
Stoichiometric constraints on secondary production in a nutrient rich headwater stream food web
No full textPhDMost consumers maintain body tissue Carbon:Nitrogen:Phosphorus within narrow constraints, despite ratios often varying markedly among basal resources. Elemental quality may be a major factor governing resource selection by, and production of, consumers. Elemental imbalances between resources and consumers could constrain the flux of matter through food webs. Here the aim was to characterise and quantify the distribution and flux of C, N and P in a headwater stream food web.
The stream water was nutrient rich (TP=208 μg L-1; TON=7 mg L-1), resulting in low C:N and C:P of basal resources. Nevertheless, elemental imbalances were evident between consumers and basal resources, particularly for organisms feeding on detritus. Although taxonomic differences existed, detritivores were typically depleted in N and P compared to taxonomically related species. Detritus comprised 97% of the biomass entering the food web, resulting in excess consumption of C and, therefore, stoichiometric imbalances.
75% of the tree canopy was removed from the heavily shaded experimental reach, resulting in a significant increase in benthic algae and a subsequent reduction in elemental imbalance and an increase in secondary production. It appears that stoichiometric constraints on secondary production were relaxed by increasing the availability of high quality resources in this detritus based food web.
Most previous studies have calculated imbalances based on diet assumed from trophic level or functional feeding groups; however, the results presented here from gut contents analysis highlight the potentially erroneous interpretation of assumed measures of imbalance. Furthermore, static measures of elemental imbalances, i.e. the difference in elemental quality between consumers and their resources, do not give an adequate measure of these constraints. The dynamic measures explored here, give an assessment of relative rates of supply (rate of consumption) and demand (from metabolism). Such dynamic measures are crucial to understanding the role of ecological stoichiometry in determining key ecosystem processes.Natural Environment Research Council.
Grants NE/C511905/1 and
NE/E0121 175/
General Equilibrium Measures of Agricultural Policy Bias in Fifteen Developing Countries
Get PDFA comparative analysis of 15 developing countries shows that, during the 1990s, indirect taxes, tariffs, and exchange rates significantly discriminated against agriculture in only one country (Malawi), was largely neutral in five (Argentina, Brazil, Costa Rica, Indonesia, and Zimbabwe), provided a moderate subsidy to agriculture in four (Mexico, Tanzania, Venezuela, and Zambia), and strongly favored agriculture in five (Egypt, Korea, Morocco, Mozambique, and Tunisia). In contrast to earlier partial equilibrium results, our general equilibrium analysis indicates that exchange rate changes can lead to anything between strongly increasing and strongly decreasing relative agriculture/non-agriculture incentives, depending on relative trade shares and relative tradability of agricultural and non-agricultural commodities. Country-specific circumstances greatly affect the relative impact of trade policies on agriculture and the rest of the economy in a general equilibrium setting. Earlier partial equilibrium measures of policy bias could not adequately incorporate country heterogeneity and are therefore likely to have overstated the bias. In any case, from the empirical results with our sample of countries, we conclude that any incentive bias against agriculture in the 1980s had mostly disappeared by the 1990s.urban bias, food and agricultural policy; general equilibrium modelling
Highly stable and reactive nano zero-valent-iron synthesis with Mg-aminoclay and aging characteristics for practical application
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