5,519 research outputs found
Fairness through the Lens of Cooperative Game Theory: An Experimental Approach
This paper experimentally investigates cooperative game theory from a normative perspective. Subjects designated as Decision Makers express their view on what is fair for others, by recommending a payoļ¬ allocation for three subjects (Recipients) whose substitutabilities and complementarities are captured by a characteristic function. We show that axioms and solution concepts from cooperative game theory provide valuable insights into the data. Axiomatic and regression analysis suggest that Decision Makersā choices can be (noisily) described as a convex combination of the Shapley value and equal split solution. A mixture model analysis, examining the distribution of Just Deserts indices describing how far one goes in the direction of the Shapley value, reveals heterogeneity across characteristic functions. Aggregating opinions by averaging, however, shows that the societal view of what is fair remains remarkably consistent across problems
Competing for Consumer Inattention
Consumers purchase multiple types of goods and services, but may be able to examine only a limited number of markets for the best price. We propose a simple model which captures these features, conveying some new insights. A ļ¬rmās price can deflect or draw attention to its market, and consequently, limited attention introduces a new dimension of competition across markets. We fully characterize the resulting equilibrium, and show that the presence of partially attentive consumers improves consumer welfare as a whole. When consumers are less attentive, they are more likely to miss the best oļ¬er in each market; but the enhanced cross-market competition decreases average price paid, as leading ļ¬rms try to stay under the consumersā radar
Dynamics of Fixation of Advantageous Mutations
We investigate the process of fixation of advantageous mutations in an
asexual population. We assume that the effect of each beneficial mutation is
exponentially distributed with mean value . The model
also considers that the effect of each new deleterious mutation reduces the
fitness of the organism independent on the previous number of mutations. We use
the branching process formulation and also extensive simulations to study the
model. The agreement between the analytical predictions and the simulational
data is quite satisfactory. Surprisingly, we observe that the dependence of the
probability of fixation on the parameter is precisely
described by a power-law relation, . The
exponent is an increase function of the rate of deleterious mutations
, whereas the probability is a decreasing function of . The
mean value of the beneficial mutations which reach ultimate
fixation depends on and . The ratio
increases as we consider higher values of mutation
value in the region of intermediate to large values of ,
whereas for low we observe the opposite behavior.Comment: 13 page
An ancestral non-proteolytic role for presenilin proteins in multicellular development of the social amoeba dictyostelium discoideum
Mutations in either of two presenilin genes can cause familial Alzheimer's disease. Presenilins have both proteolysis-dependent functions, as components of the Ī³-secretase complex, and proteolysis-independent functions in signalling. In this study, we investigate a conserved function of human presenilins in the development of the simple model organism Dictyostelium discoideum. We show that the block in Dictyostelium development caused by the ablation of both Dictyostelium presenilins is rescued by the expression of human presenilin 1, restoring the terminal differentiation of multiple cell types. This developmental role is independent of proteolytic activity, because the mutation of both catalytic aspartates does not affect presenilin ability to rescue development, and the ablation of nicastrin, a Ī³-secretase component that is crucial for proteolytic activity, does not block development. The role of presenilins during Dictyostelium development is therefore independent of their proteolytic activity. However, presenilin loss in Dictyostelium results in elevated cyclic AMP (cAMP) levels and enhanced stimulation-induced calcium release, suggesting that presenilins regulate these intracellular signalling pathways. Our data suggest that presenilin proteins perform an ancient non-proteolytic role in regulating intracellular signalling and development, and that Dictyostelium is a useful model for analysing human presenilin function
Inventarisatie lokstoffen : huidige en toekomstige trends in beheersing van plaaginsecten met signaalstoffen in combinatie met insecticiden t.b.v. de vollegrondsgroenteteelt
De effectiviteit van gewasbeschermingsmiddelen is sterk afhankelijk van de mate waarin het middel in contact komt met het insect (de raakkans). Insecten hebben de mogelijkheid om zich te verstoppen. Met lokstoffen zouden insecten uit hun verstopplek kunnen komen waarna ze beter geraakt kunnen worden. Internationaal zijn voorbeelden bekend waarbij lokmiddelen met bestrijdingsmiddel toegepast worden, o.a. tegen rupsen en als bait of als gel. Lokken/verstoren en daarna spuiten is een strategie die voor zover bekend nog weinig wordt toegepast. Wel zijn er veel lokstoffen van insecten op de markt. Onbekend is nu welke toepassingen er al zijn, in ontwikkeling zijn, of kansrijk ontwikkeld kunnen worden in de vollegrondsgroenteteelt. In dit verslag resultaten van onderzoek waarin een overzicht van de huidige stand van zaken en potentiĆ«le mogelijkheden van het gebruik van lokstoffen om insecten uit het gewas te lokken (om vervolgens gericht te bestrijden met een insecticide). Daarbij worden de volgende vragen beantwoord: o Welke lokstoffen zijn in gebruik (insecten ā gewas)? o Welke lokstoffen zijn in ontwikkeling? o Hoe worden ze toegepast? o Wat is het effect / meerwaarde van de lokstof? o Wat zijn de voor% en nadelen van het gebruik van lokstoffen
Actief randenbeheer Drenthe lijkt effect te hebben
Via monitoring inzicht krijgen in het effect van actief randenbeheer op de oppervlaktewaterkwaliteit en de biodiversiteit in het landelijk gebied en op de inpasbaarheid op de agrarische bedrijven in een bepaald gebied. Dat was het doel van het pilotprogramma āActief Randenbeheer Drentheā: een initiatief van de Provincie Drenthe, LTO-Noord en de waterschappen Hunze en Aaās en Velt en Vecht, in het zuidoostelijk deel van Drenthe. Uitvoerende partijen zijn Royal Haskoning, Praktijkonderzoek Plant & Omgeving van Wageningen UR en enkele agrarische bedrijven. Het programma begon in januari 2006 en is in november 2008 afgesloten. De totale duur van de meetperiode bedroeg 27 maande
Antibiotic production in Streptomyces is organized by a division of labor through terminal genomic differentiation
One of the hallmark behaviors of social groups is division of labor, where different group members become specialized to carry out complementary tasks. By dividing labor, cooperative groups increase efficiency, thereby raising group fitness even if these behaviors reduce individual fitness. We find that antibiotic production in colonies ofĀ Streptomyces coelicolorĀ is coordinated by a division of labor. We show thatĀ S. coelicolorĀ colonies are genetically heterogeneous because of amplifications and deletions to the chromosome. Cells with chromosomal changes produce diversified secondary metabolites and secrete more antibiotics; however, these changes reduced individual fitness, providing evidence for a trade-off between antibiotic production and fitness. Last, we show that colonies containing mixtures of mutants and their parents produce significantly more antibiotics, while colony-wide spore production remains unchanged. By generating specialized mutants that hyper-produce antibiotics, streptomycetes reduce the fitness costs of secreted secondary metabolites while maximizing the yield and diversity of these products
Genomic and transcriptional analysis of protein heterogeneity of the honeybee venom allergen Api m 6
Several components of honeybee venom are known to cause allergenic responses in humans and other vertebrates. One such component, the minor allergen Api m 6, has been known to show amino acid variation but the genetic mechanism for this variation is unknown. Here we show that Api m 6 is derived from a single locus, and that substantial protein-level variation has a simple genome-level cause, without the need to invoke multiple loci or alternatively spliced exons. Api m 6 sits near a misassembled section of the honeybee genome sequence, and we propose that a substantial number of indels at and near Api m 6 might be the root cause of this misassembly. We suggest that genes such as Api m 6 with coding-region or untranslated region indels might have had a strong effect on the assembly of this draft of the honeybee genome
A new marker based on the avian spindlin gene that is able to sex most birds, including species problematic to sex with CHD markers
We have developed a new marker (Z43B) that can be successfully used to identify the sex of most birds (69%), including species difficult or impossible to sex with other markers. We utilized the zebra finch Taeniopygia guttata EST microsatellite sequence (CK309496) which displays sequence homology to the 5ā² untranslated region (UTR) of the avian spindlin gene. This gene is known to be present on the Z and W chromosomes. To maximize cross-species utility, the primer set was designed from a consensus sequence created from homologs of CK309496 that were isolated from multiple distantly related species. Both the forward and reverse primer sequences were 100% identical to 14 avian species, including the Z chromosome of eight species and the chicken Gallus gallus W chromosome, as well as the saltwater crocodile Crocodylus porosus. The Z43B primer set was assessed by genotyping individuals of known sex belonging to 61 non-ratite species and a single ratite. The Z and W amplicons differed in size making it possible to distinguish between males (ZZ) and females (ZW) for the majority (69%) of non-ratite species tested, comprising 10 orders of birds. We predict that this marker will be useful for obtaining sex-typing data for ca 6,869 species of birds (69% of non-ratites but not galliforms). A wide range of species could be sex-typed including passerines, shorebirds, eagles, falcons, bee-eaters, cranes, shags, parrots, penguins, ducks, and a ratite species, the brown kiwi, Apteryx australis. Those species sexed include species impossible or problematic to sex-type with other markers (magpie, albatross, petrel, eagle, falcon, crane, and penguin species)
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