Complexity of and Algorithms for Borda Manipulation

We prove that it is NP-hard for a coalition of two manipulators to compute how to manipulate the Borda voting rule. This resolves one of the last open problems in the computational complexity of manipulating common voting rules. Because of this NP-hardness, we treat computing a manipulation as an approximation problem where we try to minimize the number of manipulators. Based on ideas from bin packing and multiprocessor scheduling, we propose two new approximation methods to compute manipulations of the Borda rule. Experiments show that these methods significantly outperform the previous best known %existing approximation method. We are able to find optimal manipulations in almost all the randomly generated elections tested. Our results suggest that, whilst computing a manipulation of the Borda rule by a coalition is NP-hard, computational complexity may provide only a weak barrier against manipulation in practice

Cohesion policy funding for innovation and the knowledge economy

This paper examines roles of cohesion policy in financing support for research and development and technological innovation

Eliminating the Weakest Link: Making Manipulation Intractable?

Successive elimination of candidates is often a route to making manipulation intractable to compute. We prove that eliminating candidates does not necessarily increase the computational complexity of manipulation. However, for many voting rules used in practice, the computational complexity increases. For example, it is already known that it is NP-hard to compute how a single voter can manipulate the result of single transferable voting (the elimination version of plurality voting). We show here that it is NP-hard to compute how a single voter can manipulate the result of the elimination version of veto voting, of the closely related Coombs' rule, and of the elimination versions of a general class of scoring rules.Comment: To appear in Proceedings of Twenty-Sixth Conference on Artificial Intelligence (AAAI-12

Superspreading on hydrophobic substrates:effect of glycerol additive

The spreading of solutions of three trisiloxane surfactants on two hydrophobic substrates, polyethylene and polyvinylidenefluoride, was studied with the addition of 0–40 mass % of glycerol. It was found that all the surfactant solutions spread faster than silicone oil of the same viscosity, confirming the existence of a mechanism which accelerates the spreading of the surfactant solutions. For the non-superspreading surfactant, BT-233, addition of glycerol improved the spreading performance on polyvinylidenefluoride and resulted in a transition from partial to complete wetting on polyethylene. The fastest spreading was observed for BT-233 at a concentration of 2.5 g/L, independent of glycerol content. For the superspreading surfactants, BT-240 and BT-278, the concentration at which the fastest spreading occurs systematically increased with concentration of glycerol on both substrates from 1.25 g/L for solutions in water to 10 g/L for solutions in 40% glycerol/water mixture. Thus, the surfactant equilibration rate (and therefore formation of surface tension gradients) and Marangoni flow are important components of a superspreading mechanism. De-wetting of the solutions containing glycerol, once spread on the substrates, resulted in the formation of circular drop patterns. This is in contrast to the solely aqueous solutions where the spread film shrank due to evaporation, without any visible traces being left behind

Role of PI 3-kinase, Akt and Bcl-2–related proteins in sustaining the survival of neurotrophic factor–independent adult sympathetic neurons

By adulthood, sympathetic neurons have lost dependence on NGF and NT-3 and are able to survive in culture without added neurotrophic factors. To understand the molecular mechanisms that sustain adult neurons, we established low density, glial cell-free cultures of 12-wk rat superior cervical ganglion neurons and manipulated the function and/or expression of key proteins implicated in regulating cell survival. Pharmacological inhibition of PI 3-kinase with LY294002 or Wortmannin killed these neurons, as did dominant-negative Class IA PI 3-kinase, overexpression of Rukl (a natural inhibitor of Class IA PI 3-kinase), and dominant-negative Akt/PKB (a downstream effector of PI 3-kinase). Phospho-Akt was detectable in adult sympathetic neurons grown without neurotrophic factors and this was lost upon PI 3-kinase inhibition. The neurons died by a caspase-dependent mechanism after inhibition of PI 3-kinase, and were also killed by antisense Bcl-xL and antisense Bcl-2 or by overexpression of Bcl-xS, Bad, and Bax. These results demonstrate that PI 3-kinase/Akt signaling and the expression of antiapoptotic members of the Bcl-2 family are required to sustain the survival of adult sympathetic neurons

New species of Asclepias (Apocynaceae), Baphia (Leguminosae), Cochlospermum (Bixaceae) and Endostemon (Lamiaceae) from the Kalahari sands of Angola and NW Zambia, with one new combination in Vangueria (Rubiaceae)

Four new species are described from central and eastern Angola and adjacent NW Zambia. All occur in Kalahari sand savannas rich in endemic and more widely distributed geoxylic suffrutices. Despite being known from very few collections, the conservation status of one of these new species is assessed as Least Concern, as these grasslands are nutrient-poor, are in remote sparsely populated areas, and are not threatened with conversion to agriculture. The remaining three are treated as Data Deficient. In addition, one new combination is provided for Ancylanthos rubiginosus Desf. under Vangueria as V. rubiginosa (Desf.) Lantz is an illegitimate later homonym. We also make orthographic corrections to specific epithets commemorating Ilse von Nolde, a collector who made important collections from Quela in Malange in the 1930s

Greater priming for previously distracting information in young than older adults when suppression is ruled out

The use of previously distracting information on memory tests with indirect instructions is usually age-equivalent, while young adults typically show greater explicit memory for such information. This could reflect qualitatively distinct initial processing (encoding) of distracting information by younger and older adults, but could also be caused by greater suppression of such information by younger adults on tasks with indirect instructions. In Experiment 1, young and older adults read stories containing distracting words, which they ignored, before studying a list of words containing previously distracting items for a free recall task. Half the participants were informed of the presence of previously distracting items in the study list prior to recall (direct instruction), and half were not (indirect instruction). Recall of previously distracting words was age-equivalent in the indirect condition, but young adults recalled more distracting words in the direct condition. In Experiment 2, participants performed the continuous identification with recognition task, which captures a measure of perceptual priming and recognition on each trial, and is immune to suppression. Priming and recognition of previously distracting words was greater in younger than older adults, suggesting that the young engage in more successful suppression of previously distracting information on tasks in which its relevance is not overtly signaled

The joint evolutionary histories of Wolbachia and mitochondria in Hypolimnas bolina

Background. The interaction between the Blue Moon butterfly, Hypolimnas bolina, and Wolbachia has attracted interest because of the high prevalence of male-killing achieved within the species, the ecological consequences of this high prevalence, the intensity of selection on the host to suppress the infection, and the presence of multiple Wolbachia infections inducing different phenotypes. We examined diversity in the co-inherited marker, mtDNA, and the partitioning of this between individuals of different infection status, as a means to investigate the population biology and evolutionary history of the Wolbachia infections. Results. Part of the mitochondrial COI gene was sequenced from 298 individuals of known infection status revealing ten different haplotypes. Despite very strong biological evidence that the sample represents a single species, the ten haplotypes did not fall within a monophyletic clade within the Hypolimnas genus, with one haplotype differing by 5% from the other nine. There were strong associations between infection status and mtDNA haplotype. The presence of wBol1 infection in association with strongly divergent haplotypes prompted closer examination of wBol1 genetic variation. This revealed the existence of two cryptic subtypes, wBol1a and wBol1b. The wBol1a infection, by far the most common, was in strict association with the single divergent mtDNA haplotype. The wBol1b infection was found with two haplotypes that were also observed in uninfected specimens. Finally, the wBol2 infection was associated with a large diversity of mtDNA haplotypes, most often shared with uninfected sympatric butterflies. Conclusion. This data overall supports the hypothesis that high prevalence of male-killing Wolbachia (wBol1) in H. bolina is associated with very high transmission efficiency rather than regular horizontal transmission. It also suggests this infection has undergone a recent selective sweep and was introduced in this species through introgression. In contrast, the sharing of haplotypes between wBol2-infected and uninfected individuals indicates that this strain is not perfectly transmitted and/or shows a significant level of horizontal transmission

Complexity of and Algorithms for the Manipulation of Borda, Nanson and Baldwin’s Voting Rules

Abstract We investigate manipulation of the Borda voting rule, as well as two elimination style voting rules, Nanson's and Baldwin's voting rules, which are based on Borda voting. We argue that these rules have a number of desirable computational properties. For unweighted Borda voting, we prove that it is NP-hard for a coalition of two manipulators to compute a manipulation. This resolves a long-standing open problem in the computational complexity of manipulating common voting rules. We prove that manipulation of Baldwin's and Nanson's rules is computationally more difficult than manipulation of Borda, as it is NP-hard for a single manipulator to compute a manipulation. In addition, for Baldwin's and Nanson's rules with weighted votes, we prove that it is NP-hard for a coalition of manipulators to compute a manipulation with a small number of candidates. Because of these NP-hardness results, we compute manipulations using heuristic algorithms that attempt to minimise the number of manipulators. We propose several new heuristic methods. Experiments show that these methods significantly outperform the previously best known heuristic method for the Borda rule. Our results suggest that, whilst computing a manipulation of the Borda rule is NP-hard, computational complexity may provide only a weak barrier against manipulation in practice. In contrast to the Borda rule, our experiments with Baldwin's and Nanson's rules demonstrate that both of them are often more difficult to manipulate in practice. These results suggest that elimination style voting rules deserve further study