Maximum Coverage and Maximum Connected Covering in Social Networks with Partial Topology Information

Viral marketing campaigns seek to recruit the most influential individuals to cover the largest target audience. This can be modeled as the well-studied maximum coverage problem. There is a related problem when the recruited nodes are connected. It is called the maximum connected cover problem. This problem ensures a strong coordination between the influential nodes which are the backbone of the marketing campaign. In this work, we are interested on both of these problems. Most of the related literature assumes knowledge about the topology of the network. Even in that case, the problem is known to be NP-hard. In this work, we propose heuristics to the maximum connected cover problem and the maximum coverage problem with different knowledge levels about the topology of the network. We quantify the difference between these heuristics and the local and global greedy algorithms

Evolution of Social Power for Opinion Dynamics Networks

This article studies the evolution of opinions and interpersonal influence structures in a group of agents as they discuss a sequence of issues, each of which follows an opinion dynamics model. In this work, we propose a general opinion dynamics model and an evolution of interpersonal influence structures based on the model of reflected appraisals proposed by Friedkin. Our contributions can be summarized as follows: (i) we introduce a model of opinion dynamics and evolution of interpersonal influence structures between issues viewed as a best response cost minimization to the neighbor's actions, (ii) we show that DeGroot's and Friedkin-Johnsen's models of opinion dynamics and their evolution of interpersonal influence structures are particular cases of our proposed model, and (iii) we prove the existence of an equilibrium. This work is a step towards providing a solid formulation of the evolution of opinions and interpersonal influence structures over a sequence of issues

Functional Analysis of in Vivo and in Organello Footprinting of HeLa Cell Mitochondrial DNA in Relationship to ATP and Ethidium Bromide Effects on Transcription

In vivo and in organello footprinting techniques based on methylation interference have been utilized to investigate protein-DNA interactions in the transcription initiation and rDNA transcription termination regions of human mitochondrial DNA (mtDNA) in functionally active mitochondria. In particular, the changes in methylation reactivity of these regions in response to treatment of the organelles with ATP or ethidium bromide, which affects differentially the rates of mitochondrial rRNA and mRNA synthesis, have been analyzed. Two major sites of protein-DNA interactions have been identified in the main control region of mtDNA, both in vivo and in organello, which correspond to the regions of the light-strand promoter and heavy-strand rRNA-specific promoter. The in organello footprinting of the latter showed ATP- and ethidium bromide-dependent modifications that could be correlated with changes in the rate of rRNA but not of mRNA synthesis. By contrast, no ATP effects were observed on the in organello footprinting pattern of the termination region and on in vitro transcription termination, strongly suggesting that ATP control of rRNA synthesis occurs at the initiation level. Several methylation interference sites were found upstream of the whole H-strand transcription unit, pointing to possible protein-DNA interactions related to the activity of this unit. In vivo footprinting of the rDNA transcription termination region of human mtDNA has revealed a very strong protection pattern, indicating a high degree of occupancy of the termination site by mitochondrial transcription termination factor (~80%)

Estilos políticos y orientación tecnocrática bajo los gobiernos de Lagos y Bachelet

This article explores the ways in which Presidents Lagos and Bachelet have dealt with the technocratic phenomenon within their respective governments. For this purpose, special attention is given to the political styles characterizing both presidents and the manner in which these styles have facilitated or obstructed the functioning of technocratic groups within governmental circles. As it is argued, the attitude adopted by both leaders vis-à-vis the presence of technocratic groups within their governments is largely conditioned by the type of relation established between the presidents and the supporting political parties. In addition to this, a sordid clash between politicians and technocrats for power and influence can be observed. President Lagos always distrusted the technocracy. He only made strategic use of it in order to lehis cgitimate onduction of the country's economy towards entrepreneurial groups and the international financial community. On the other hand, President Bachelet will be forced to seek support from the 'Expansiva' technocrats due to her problematic relation vis-à-vis the leaders of the Concertación's political parties.Este artículo explora de qué manera Ricardo Lagos y Michelle Bachelet han abordado el tema de la tecnocracia durante sus respectivos gobiernos. Para ello se presta especial atención a los estilos políticos utilizados por ambos presidentes y como éstos facilitan o obstaculizan el accionar tecnócratico al interior de sus administraciones. Se argumenta que la posición que ambos líderes adoptan ante los estamentos tecnocráticos al interior de sus gobiernos se encuentra fuertemente condicionada por el tipo de relación que estos presidentes establecen con las dirigencias de los partidos políticos que participan en la coalición gubernamental. Además, se subraya la existencia de una lucha sórdida entre políticos tradicionales y tecnócratas por el poder político y la influencia sobre la figura del presidente al interior de ambas administraciones. El Presidente Lagos siempre desconfió de la tecnocracia y sólo hizo uso estratégico de ésta para atender a problemas de legitimidad ante las clases empresariales y la comunidad financiera internacional respecto a la conducción económica del país. Por su parte, Michelle Bachelet se verá obligada a aceptar el apoyo de la tecnocracia de 'Expansiva' en vista de la siempre problemática relación entre ella y las cúpulas políticas concertacionistas

Self-assembly of triblock copolymers in aqueous solution

Indexación: ScieloThe aggregation of PE4VP-b-PS-b-PE4VP block copolymers was studied in aqueous solution. Triblock copolymers P4VP-b-PS-b-P4VP were synthesized by sequential anionic polymerization of poly(styrene) and poly(4-vinylpirydine) using sodium naphthalene as a bifunctional initiator. Subsequently, the 4-vinylpyridine units were quaternized with ethyl bromide to obtain cationic PE4VP-b-PS-b-PE4VP block copolymers. Both star and crew-cut micelles were formed. The concentrations at which micelles are formed cmc were determined, by steady-state and time-resolved fluorescence probing methods, as a function of quatemization degree. The results indicate that cmc of crew-cut micelles increases with increasing charge density of the PE4VP blocks. For star micelles there is not a clear dependency of cmc with the percentage of quatemization. The lifetime of pyrene fluorescence and the ratio I1/I3 were determined at concentrations of copolymers well above the cmc, and the results show that the location of pyrene into the micelle changes with the charge density of the micelle corona. The micropolarity sensed by pyrene decreases with increasing quatemization degree. The presence of aggregates was confirmed by transmission electronic microscopy.http://www.scielo.cl/scielo.php?script=sci_arttext&pid=S0717-97072008000200013&lng=es&nrm=is

The Mitochondrial Myopathy, Encephalopathy, Lactic Acidosis, and Stroke-like Episode Syndrome-associated Human Mitochondrial tRNALeu(UUR) Mutation Causes Aminoacylation Deficiency and Concomitant Reduced Association of mRNA with Ribosomes

The pathogenetic mechanism of the mitochondrial tRNALeu(UUR) A3243G transition associated with the mitochondrial myopathy, encephalopathy, lactic acidosis, and stroke-like episodes (MELAS) syndrome has been investigated in transmitochondrial cell lines constructed by transfer of mutant mitochondrial DNA (mtDNA)-carrying mitochondria from three genetically unrelated MELAS patients or of isogenic wild-type mtDNA-carrying organelles into human mtDNA-less cells. An in vivo footprinting analysis of the mtDNA segment within the tRNALeu(UUR) gene that binds the transcription termination factor failed to reveal any difference in occupancy of sites or qualitative interaction with the protein between mutant and wild-type mtDNAs. Cell lines nearly homoplasmic for the mutation exhibited a strong (70-75%) reduction in the level of aminoacylated tRNALeu(UUR) and a decrease in mitochondrial protein synthesis rate. The latter, however, did not show any significant correlation between synthesis defect of the individual polypeptides and number or proportion of UUR codons in their mRNAs, suggesting that another step, other than elongation, may be affected. Sedimentation analysis in sucrose gradient showed a reduction in size of the mitochondrial polysomes, while the distribution of the two rRNA components and of the mRNAs revealed decreased association of mRNA with ribosomes and, in the most affected cell line, pronounced degradation of the mRNA associated with slowly sedimenting structures. Therefore, several lines of evidence indicate that the protein synthesis defect in A3243G MELAS mutation-carrying cells is mainly due to a reduced association of mRNA with ribosomes, possibly as a consequence of the tRNALeu(UUR) aminoacylation defect

Congestion in Randomly Deployed Wireless Ad-Hoc and Sensor Networks

Congestion in wireless ad-hoc and sensor networks not only causes packet loss, and increases queueing delay, but also leads to unnecessary energy consumption. In a wireless ad-hoc and sensor network, two types of congestion can occur: node-level congestion, which is caused by buffer overflow in the node, or link-level congestion, when wireless channels are shared by several nodes and collisions occur when multiple active nodes try to seize the channel at the same time. We study a measure of link-level congestion in a static wireless ad-hoc and sensor network randomly deployed over an area. The measure considered on this paper is the inverse of the greatest eigenvalue of the adjacency matrix of the random graph. This measure of congestion gives an approximation of the average quantity of wireless links of a certain length that a node have on the wireless ad-hoc and sensor network. We review the results to find this measure of congestion in a Bernoulli random graph and we use tools from random graph theory and random matrix theory to extend this measure of congestion on a Geometric random graph

PESQUISA E PRODUÇÃO DE CONHECIMENTO NA PRÁTICA PROFISSIONAL DO ASSISTENTE SOCIAL: NOTAS INTRODUTÓRIAS SOBRE A REALIDADE DE PARINTINS/AM

Resumo A premissa da qual parte este artigo é a necessária reflexão crítica sobre a realidade profissional do Assistente Social no município de Parintins-AM a partir de um levantamento exploratório e algumas sinalizações presentes em pesquisas já realizadas, as quais perpassam por questões relacionadas ao processo da pesquisa e produção de conhecimento científico na prática profissional. A discussão em análise aponta algumas fragilidades encontradas no desenvolver do exercício profissional, tais como as formas de vínculo empregatício, dificuldades na compreensão da unidade teoria e prática, parcialidade na ação investigativa; elementos estes que podem interferir na não produção científica