The Complex Community Structure of the Bitcoin Address Correspondence Network

Bitcoin is built on a blockchain, an immutable decentralized ledger that allows entities (users) to exchange Bitcoins in a pseudonymous manner. Bitcoins are associated with alpha-numeric addresses and are transferred via transactions. Each transaction is composed of a set of input addresses (associated with unspent outputs received from previous transactions) and a set of output addresses (to which Bitcoins are transferred). Despite Bitcoin was designed with anonymity in mind, different heuristic approaches exist to detect which addresses in a specific transaction belong to the same entity. By applying these heuristics, we build an Address Correspondence Network: in this representation, addresses are nodes are connected with edges if at least one heuristic detects them as belonging to the same entity. In this paper, we analyze for the first time the Address Correspondence Network and show it is characterized by a complex topology, signaled by a broad, skewed degree distribution and a power-law component size distribution. Using a large-scale dataset of addresses for which the controlling entities are known, we show that a combination of external data coupled with standard community detection algorithms can reliably identify entities. The complex nature of the Address Correspondence Network reveals that usage patterns of individual entities create statistical regularities; and that these regularities can be leveraged to more accurately identify entities and gain a deeper understanding of the Bitcoin economy as a whole

Prevalence of the exposure to direct and indirect violence: a study with adolescents from public schools

A adolescência é considerada uma etapa do ciclo vital na qual há maior vulnerabilidade para exposição à violência tanto Adolescence is considered as a stage of the vital cycle, in which there is greater vulnerability to be exposed to both direct (being a victim) and indirect violence (being a witness or hearing about violent acts). This study investigated the exposure to direct and indirect violence (dependent variables), in relation to associated independent variables (gender, age range, school failure and family configuration), in 426 adolescents of 12 to 18 years old, from public schools in the city of Porto Alegre, Brazil. A sociodemographic questionnaire and the instrument “Screening of the exposure of children to violence in the community” were used. Descriptive and inferential analyses (Mann-Whitney and Kruskal-Wallis tests) indicated that 65% of the participants were exposed to at least one episode of direct violence, while 97% of them were exposed to indirect violence; and that both exposures were more frequent in adolescents from 16 to 18 years old (p<0.001) who had a history of school failure (p<0.02). Emphasis is given to the need for further studies that investigate factors associated to indirect violence and the impact of this type of exposure in development, in addition to prevention and intervention public policies in the area of violence toward children and adolescents.A adolescência é considerada uma etapa do ciclo vital na qual há maior vulnerabilidade para exposição à violência tanto direta (ser a própria vítima), quanto indireta (ser testemunha ou ouvir falar). Este estudo investigou a exposição à violência direta e indireta (variáveis dependentes), assim como variáveis independentes associadas (sexo, faixa etária, reprovação escolar e configuração familiar), em 426 adolescentes de 12 a 18 anos estudantes de escolas públicas da cidade de Porto Alegre, no Brasil. Foi utilizada uma ficha de dados sociodemográficos e o instrumento “Triagem da exposição de crianças à violência na comunidade”. Análises descritivas e inferenciais (testes de Mann-Whitney e Kruskal-Wallis) indicaram que 65% dos participantes foram expostos a, pelo menos, um episódio de violência direta, enquanto 97% foram expostos à violência indireta; que ambas as exposições foram mais frequentes em adolescentes de 16 a 18 anos (p<0,001) e que apresentaram reprovação escolar (p<0,02). Destaca-se a necessidade de novos estudos que investiguem fatores associados à violência indireta e o impacto deste tipo de exposição no desenvolvimento, além de políticas públicas de prevenção e intervenção na área da violência infanto-juvenil.La adolescencia es considerada una etapa del ciclo vital en la que existe mayor vulnerabilidad a la exposición a violencia directa (ser víctima) e indirecta (ser testigo o escuchar acerca de actos violentos). En el presente estudio se investigó la exposición a la violencia directa e indirecta (variables dependientes) en relación con variables asociadas como sexo, edad, reprobación escolar y configuración familiar, en 426 adolescentes de entre 12 y 18 años de edad, estudiantes de colegios públicos de la ciudad de Porto Alegre, Brasil. Se utilizó un cuestionario de datos sociodemográficos y el instrumento “Triagem da exposição de crianças à violência na comunidade” (Evaluación de la exposición de niños a la violencia en la comunidad). Se llevaron a cabo análisis descriptivos e inferenciales (test de Mann-Whitney y Kruskall Wallis), los cuales mostraron que 65% de los participantes estuvieron expuestos por lo menos una vez a un episodio de violencia directa, y 97% a violencia indirecta; ambas exposiciones fueron más frecuentes en adolescentes de 16 a 18 años (p < .001) que presentaban fracaso escolar (p < .002). Se destaca la necesidad de realizar nuevos estudios en los que se investiguen factores asociados a la violencia indirecta y el impacto de este tipo de exposición en el desarrollo y en las políticas públicas de prevención e intervención en el área de la violencia infantil y juvenil

Adaptação para implementação online de uma intervenção em Psicologia Positiva para a promoção de saúde

This study describes the online adaptation of a Positive Psychology intervention for health promotion. The methodological guidelines used were The Formative Method for Adapting Psychotherapy and the Consolidated Framework for Implementation, based on: characteristics of the intervention; of the individuals; internal and external contexts; implementation process. The intervention consisted of 6 online group sessions, with 10 staff members from the health management team of a retiree association in RS/Brazil, mean age 43.6 years (SD = 15.86). An evaluation questionnaire was completed at the end of the activities and descriptive statistics revealed participants' satisfaction with the intervention and with the moderator, as well as generalization of the contents. Changes were suggested specially to increase the duration of the sessions. We suggest the systematization the processes used in this study to support research on the implementation and adaptation of online interventions for different contexts and populations.Este estudio describe la adaptación online de una intervención en Psicología Positiva para la promoción de la salud. Como guía metodológico se utilizó el The Formative Method for Adapting Psychotherapy y Consolidated Framework for Implementation Research en: características de la intervención; de individuos; contextos internos y externos; proceso de implementación. La intervención consistió en 6 reuniones grupales con 10 miembros del equipo de gestión de salud de una asociación de jubilados en RS (Brasil), con una edad promedio de 43.6 años (DE = 15.86). Se completó un cuestionario de evaluación al final de las actividades y las estadísticas descriptivas revelaron la satisfacción de los participantes con la intervención, con el moderador y generalización de los contenidos. Se sugirieron cambios, especialmente aumento en la carga de trabajo de las sesiones. Sugerimos sistematizar los procesos utilizados en este estudio para apoyar la investigación sobre la implementación y adaptación de intervenciones para diferentes contextos y públicos.Este estudo descreve a adaptação online de uma intervenção em Psicologia Positiva para promoção de saúde. Como diretriz metodológica, utilizou-se o The Formative Method for Adapting Psychotherapy e o Consolidated Framework for Implementation Research, nos eixos: características da intervenção; dos indivíduos; contextos interno e externo; processo de implementação. A intervenção consistiu em 6 encontros grupais online, com 10 integrantes da equipe de gestão em saúde de uma associação de aposentados do RS, Brasil, média de idade 43,6 anos (DP = 15,86). Um questionário de avaliação foi preenchido ao final das atividades e estatísticas descritivas revelaram satisfação dos participantes com a intervenção e com o moderador, assim como generalização dos conteúdos. Foram sugeridas alterações, especialmente aumento da carga horária das sessões. Sugere-se a sistematização dos processos utilizados neste estudo para embasar pesquisas de implementação e adaptação de intervenções online para diferentes contextos e público-alvo

Galls as a Disputed Resource for Female Parasitoid Wasps Contests

This is the final version of the article. It first appeared from Scientific Research Publishing via http://dx.doi.org/ 10.4236/ae.2015.33010We investigated how the parasitoid Torymus sp. (Hymenoptera: Torymidae) attacking galls of Schismatodiplosis lantanae (Diptera: Cecidomyiidae) on Lantana camara (Verbenaceae) behaves in the presence of a conspecific female competitor in the patch. Presence of a competitor greatly changed resident exploitation behavior. Wasps alone spent more time in gall exploitation behaviors (walk-antennate and probe) and in post-oviposition behaviors (stationary and groom), and when intruders were present they spent more time walking. The attack strategy was trough threatening: raising wings and pointing the antennae towards the opponent. Different from theoretical expectations, residents were not always the attacker. Number of galls in the patch and female wasp size did not affect contest outcomes, although gall exploitation time and time on leaf were significant factors for the probability of having attacks. Overall, the study highlights the fact that intruder interest in the host was the main cause of contests and also this is a unique report both in terms of the target species and the nature of the disputed resource, a gall-inducer inside a singular spatial unit, the gall.We thank all anonymous referees, Marlène Goubault, Paula Beatriz de Araujo, Geraldo Luiz Gonçalves Soares and Luiz Ernesto Costa Schmidt for suggestions and comments. Simone Mundstock Jahnke and Valmir Antonio Costa for helping in wasp identification. This study was supported by CAPES

Luigi Cremona and Wilhelm Fiedler: the link between descriptive and projective geometry in technical instruction

This paper considers Luigi Cremona’s and Wilhelm Fiedler’s outlook on technical instruction at school and university level, their vision about the educational role of descriptive geometry and its relation to Monge’s original conception. Like Cremona, Fiedler sees a symbiosis between descriptive and projective geometry via the fundamental idea of central projection. The link between projective and descriptive geometry plays a double role: an educational one due to the graphical aspects of the two disciplines and a conceptual one due to the connection of theory to practice. Thus, projective and descriptive geometry contribute to form a class of scientifically educated people, and the link between them epitomizes – in the opinion of Cremona – the link between pure mathematics and its applications. According to Fiedler, the main scope of the teaching of descriptive geometry is the scientific construction and development of “Raumanschauung”, as stated in a paper published in the Italian journal Giornale di Matematiche. The textbooks by Fiedler (1871) and Cremona (1873) were used in Italy to develop the geometry programs for the sezione fisico matematica (physics and mathematics section) within technical secondary instruction. While the relation between projective and descriptive geometry – and, thus, between pure and applied mathematics – had a short life at secondary school level in Italy, at the turn of the century there was a new expansion at university level due to the important role that then mathematicians had in the creation of the Faculty of Architecture

On the stability of metal nanoparticles synthesized by laser ablation in liquids

Nanoparticles (NPs) synthesized through chemical routes are stabilized by a surface layer of capping agents. These molecules, beside avoid the infinite growth of the solid phase, impart steric or electrostatic repulsive inter- particle interactions. The technique known as “Laser ablation in liquid” (LAL) is an alternative technique to synthesize capping agents-free metal nanoparticles.1 LAL involves focused laser pulsed irradiation of a bulk metal target in a liquid and consist of four stages . Laser-matter interaction, plasma induction, cavitation bubble formation and particle release in solution. Strikingly, LAL leads to the formation of very stable “naked” NPs that are long standing for months. It is worth emphasizing that the stabilization of noble metal colloids in water is challenging because of the large Hamaker constant. Noble metal NPs prepared by LAL have a large negative zeta-potential and therefore their stability should be electrostatic in nature and it is due to the presence negative surface charges. The question is what is the origin of these surface charges? Common explanations for this phenomenon involve the presence of gold oxides and/or the anion adsorption.2, 3 However, the presence of oxidized gold species on the surface of NPs prepared in water has been recently questioned on the basis of XPS analysis.4 Very recently we have accumulated evidences that, in the case of gold NPs prepared by LAL, the metal oxidation and anion adsorptions have only a minor role on building the negative surface potential and we proposed that excess electrons formed within the plasma phase could charge the gold particles.5 The figure below describes an experiment that points in this direction: the addition of macroscopic metallic objects induce the loss of charge (as seen in the temporal evolution of the zeta-potential) and eventually NPs aggregation pnly the case of gold NP synthesized by LAL while it is ineffective in the case of NP synthesized by the classical Turkevitch chemical reduction of HAuCl4 reduction (see the picture of the cuvettes after 4 days). Please click Additional Files below to see the full abstract

“Pesquisadora-mãe”: articulações e praticalidades em uma pesquisa sobre cuidado

Este artigo propõe refletir sobre práticas do fazer pesquisa sobre cuidado, do lugar de uma “pesquisadora-mãe”, a partir de uma experiência etnográfica em uma Comuna rural localizada em um assentamento no interior do estado do Rio Grande do Sul. Inspiradas por Maria Puig de la Bellacasa, consideramos que a ética do fazer pesquisa não mora em um lugar “subjetivo” e de difícil acesso, mas está localizada nas práticas de cuidado diário, atravessadas pelas possibilidades de ser “tocada”, tanto no sentido material quanto afetivo. A partir de cenas vivenciadas em campo, em que ser pesquisadora e mãe provocam uma situacionalidade privilegiada, os conceitos de “kin” e “touching visions” são resgatados de modo a percebermos as fronteiras entre o “eu” e o “outro” enquanto borradas, possibilitando relacionalidades, criando conexões recíprocas e articulações entre os seres, sejam eles humanos ou não.This article proposes to reflect on practices of doing research on care, from the place of a “mother-researcher”, based on an ethnographic experience in a rural Commune located in a settlement in the rural area of Rio Grande do Sul (BR). Inspired by María Puig de la Bellacasa, we consider that ethics of doing research does not live in a “subjective” and difficult-to-access place, but it’s located in daily care practices, crossed by the possibilities of being “touched”, both in the material as well as affective sense. From scenes experienced in the fieldwork, in which being a researcher and a mother provoke a privileged situation, the concepts of “kin” and “touching visions” are rescued in order to perceive the boundaries between “me” and “other” as blurred, enabling relationships, creating reciprocal connections and articulations between being, whether human or no

“Mother-researcher”: articulations and practicalities in a research on care

Este artigo propõe refletir sobre práticas do fazer pesquisa sobre cuidado, do lugar de uma “pesquisadora-mãe”, a partir de uma experiência etnográfica em uma Comuna rural localizada em um assentamento no interior do estado do Rio Grande do Sul. Inspiradas por Maria Puig de la Bellacasa, consideramos que a ética do fazer pesquisa não mora em um lugar “subjetivo” e de difícil acesso, mas está localizada nas práticas de cuidado diário, atravessadas pelas possibilidades de ser “tocada”, tanto no sentido material quanto afetivo. A partir de cenas vivenciadas em campo, em que ser pesquisadora e mãe provocam uma situacionalidade privilegiada, os conceitos de “kin” e “touching visions” são resgatados de modo a percebermos as fronteiras entre o “eu” e o “outro” enquanto borradas, possibilitando relacionalidades, criando conexões recíprocas e articulações entre os seres, sejam eles humanos ou não.This article proposes to reflect on practices of doing research on care, from the place of a “mother-researcher”, based on an ethnographic experience in a rural Commune located in a settlement in the rural area of Rio Grande do Sul (BR). Inspired by María Puig de la Bellacasa, we consider that ethics of doing research does not live in a “subjective” and difficult-to-access place, but it’s located in daily care practices, crossed by the possibilities of being “touched”, both in the material as well as affective sense. From scenes experienced in the fieldwork, in which being a researcher and a mother provoke a privileged situation, the concepts of “kin” and “touching visions” are rescued in order to perceive the boundaries between “me” and “other” as blurred, enabling relationships, creating reciprocal connections and articulations between being, whether human or no

Galactic chemical evolution

We analyze the evolution of oxygen abundance radial gradients resulting from our chemical evolution models calculated with different prescriptions for the star formation rate (SFR) and for the gas infall rate, in order to assess their respective roles in shaping gradients. We also compare with cosmological simulations and confront all with recent observational datasets, in particular with abundances inferred from planetary nebulae. We demonstrate the critical importance in isolating the specific radial range over which a gradient is measured, in order for their temporal evolution to be useful indicators of disk growth with redshift