16 research outputs found
Avaliação do impacto nas métricas de desempenho de protocolos de roteamento em redes MANET: [dissertação]
No full textDissertação (mestrado) - Universidade Federal de Santa Catarina, Centro Tecnológico. Programa de Pós-Graduação em Ciência da Computação.As promessas das redes móveis Wireless em resolver problemas do mundo virtual continuam chamando a atenção dos projetos de pesquisas industriais e acadêmicos. O aumento da performance dos computadores e da tecnologia de comunicação Wireless é notável. Também evidencia-se a necessidade de mobilidade e conectividade que o mundo moderno impõe. A maior parte das pesquisas sobre redes Wireless foi realizada para o desenvolvimento dos mecanismos básicos de operação. Nos últimos tempos, contudo, foco que tem chamado muito a atenção tange os aspectos de segurança. Considerando que este tipo de redes tem sido idealizado para operar em ambientes hostis, onde os sinais possam ser interceptados e/ou alterados, como as aplicações comerciais e as militares, os mecanismos de segurança devemvariar de acordo com o tipo de aplicação a que se destinarem. Esta dissertação tem por objetivo efetuar um mapeamento dos diferentes tipos de protocolos de roteamento para redes MANET e, a partir daí, pretende-se realizar simulações no Network Simulator avaliando a latência, jitter, vazão e perda de pacotes, checando, assim, o desempenho dos protocolos que implementam conceitos mais sólidos de segurança, comparando-os com protocolos que não possuam esta característica. Cada um dos protocolos tem suas vantagens e desvantagens e, pela própria característica da rede, a escolha do protocolo que melhor se adeque as características de mobilidade e volatilidade de rede é uma tarefa complexa. As informações das simulações podem contribuir para se traçar um perfil dos possíveis impactos causados com a agregação de segurança aos protocolos aqui implementados. Os resultados apresentados nas simulações desta dissertação mostram que os protocolos seguros de melhor desempenho e que mais atendem aos requisitos de segurança são o Ariadne e o SEAD
Ariadne-BFT: uma proposta de extensão do protocolo Ariadne baseada na descoberta e seleção de rotas do protocolo BFTR
No full textDissertação (mestrado) - Universidade Federal de Santa Catarina, Centro Tecnológico. Programa de Pós-Graduação em Ciência da Computação.As redes sem fio ad hoc surgiram para estender a mobilidade e a flexibilidade no ambiente sem fio, onde um conjunto de nós, que podem agir como roteadores, formam a infra-estrutura de roteamento na rede. A maioria dos protocolos de roteamento propostos não utiliza mecanismos de segurança, pois assumem que o ambiente é composto apenas por nós confiáveis. Mas devido à mudança dinâmica de topologia e ambiente aberto, uma rede ad hoc é extremamente vulnerável à presença de nós maliciosos os quais podem degradar desempenho ou até mesmo impedir o funcionamento da rede. Para evitar ou minimizar os problemas causados pela falta de segurança, os seguintes protocolos de roteamento seguro foram propostos: Ariadne, SAODV, BFTR, SEAD e ARAN. Neste contexto, a presente dissertação tem como objetivo analisar estes protocolos de roteamento seguro utilizados em redes sem fio ad hoc e propor melhorias nos mecanismos de segurança projetados para proteger a rede contra ataques interrupção de roteamento e de consumo de recursos. Como resultado desta análise, é proposto o Ariadne-BFT (Ariadne Best-effort Fault-Tolerant), uma extensão do protocolo de roteamento seguro Ariadne baseado nos algoritmos de descoberta e seleção de rotas do protocolo BFTR. O Ariadne-BFT incrementa a segurança no roteamento em relação ao protocolo Ariadne original, com a proteção contra o ataque Blackhole. Experimentos são executados sob a forma de simulações para análise e comparação de desempenho, através das quais é demonstrado que o protocolo Ariadne-BFT possui um desempenho superior em relação às métricas latência e razão de entrega de pacotes
Evaluation of the humoral immune response to a multicomponent recombinant vaccine against S. aureus in healthy pregnant heifers
No full textStaphylococcus aureus is a worldwide pathogen that causes mastitis in dairy herds. Shortcomings in control programs have encouraged the development of vaccines against this pathogen. This study evaluated the vaccine candidate VacR, which included recombinant S. aureus protein clumping factor A (rClf), fibronectin binding protein A (rFnBP) and hemolysin beta (rBt), formulated with a novel immune-stimulating complex. Comparisons were made between healthy pregnant heifers that received either VacR (n = 8; VacR group) or phosphate buffered saline (PBS) plus adjuvant (control group) SC in the supramammary lymph node area on days 45 and 15 before the expected calving date. Blood and foremilk samples were collected from 7 to 60 days post-calving.
After calving, heifers in the VacR group produced higher total IgG (IgGtotal) titers against each component, in both serum (rBt, 3.4 × 105; rClf, 3.1 × 105; rFnBP, 2.3 × 105) and milk (rBt, 2.6 × 104; rClf, 1.3 × 104; rFnBP, 1.1 × 104), than control heifers (P < 0.0001). There were increased concentrations of IgG1 and IgG2 in VacR group (P < 0.05), in both serum and milk. Humoral responses remained high throughout the period most susceptible to intramammary infections (P < 0.01). Antibodies produced against S. aureus rClf and rFnBP reduced bacterial adherence to fibronectin and fibrinogen by 73% and 67%, respectively (P < 0.001). Milk antibodies against these adhesins inhibited S. aureus invasion of a mammary epithelial cell line (MAC-T), resulting in 15.7% of bacteria internalized (P < 0.0001). There was an approximately 6-fold reduction in the hemolysis titer for the native hemolysin in the VacR group compared to the control group (P < 0.0001) and a significantly increase in the proportion of positive neutrophils (VacR, 29.7%; PBS, 13.1%) and the mean fluorescent index (VacR, 217.4; PBS, 152.6; P < 0.01) in the VacR group. The results suggest that VacR is a valuable vaccine candidate against S. aureus infections, and merits further field trials and experimental challenges.EEA RafaelaFil: Pujato, Nazarena. Universidad Nacional del Litoral. Facultad de Bioquímica y Ciencias Biológicas; ArgentinaFil: Camussone, Cecilia. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Instituto Nacional de Tecnología Agropecuaria (INTA). Estación Experimental Agropecuaria Rafaela; ArgentinaFil: Renna, Maria Sol. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Santa Fe. Instituto de Ciencias Veterinarias del Litoral. Universidad Nacional del Litoral. Facultad de Ciencias Veterinarias; ArgentinaFil: Perrig, Melina Soledad. Universidad Nacional del Litoral. Facultad de Bioquímica y Ciencias Biológicas; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Santa Fe; Argentina.Fil: Morein, Bror. Uppsala University. Department of Clinical Virology; SueciaFil: Calvinho, Luis Fernando. Instituto Nacional de Tecnología Agropecuaria (INTA). Estación Experimental Agropecuaria Rafaela; Argentina. Universidad Nacional del Litoral. Facultad de Ciencias Veterinarias; ArgentinaFil: Marcipar, Iván Sergio. Universidad Nacional del Litoral. Facultad de Bioquímica y Ciencias Biológicas. Laboratorio de Tecnología Inmunológica; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Santa Fe; Argentin
Recipients' anonymity in multihop ad-hoc networks
No full textMultihop ad-hoc networks have a dynamic topology. Retrieving a route towards a remote peer requires the execution of a recipient lookup, which can publicly reveal sensitive information about him. Within this context, we propose an efficient, practical and scalable solution to guarantee the anonymity of recipients' nodes in ad-hoc networks.Los saltos múltiples de redes ad-hoc tienen una topología dinámica. La recuperación de una ruta hacia un par remoto requiere la ejecución de una búsqueda de destinatarios, que puede revelar públicamente información confidencial. Dentro de este contexto, proponemos una solución
eficiente, práctica y escalable para garantizar el anonimato de los nodos destinatarios en redes ad-hoc.Els salts múltiples de xarxes ad hoc tenen una topologia dinàmica. La recuperació d'una ruta cap a un parell remot requereix l'execució d'una recerca de destinataris, que pot revelar públicament informació confidencial. Dins d'aquest context, proposem una solució eficient, pràctica i escalable per garantir l'anonimat dels nodes destinataris en xarxes ad-hoc
Subjective perception of the life-course in old age and in youth
No full textThe aim of the article is to present the results of the perceived age norms of the lifecourse. Several such studies were described in literature. The research project of Perrig-Chiello and Perren (2005) inspired the author to replicate some of the used measures in a different cultural context. Polish women from early and late adulthood were interviewed on timing biographical transitions and well-being.
Tested hypothesis claimed that timing is related to age. The second hypothesis assumed connection between well-being and age. The comparison of the results of senior women and young women proved different timing of 11 biographical transitions. However their subjective perception and evaluation of life-course was comparable. There were only 5 significant differences in emotional valence of transitions: end of school education, being single, birth of second child, grandparenthood, and retirement given by senior and young women. The achieved results proved the moderately positive life satisfaction both of senior women and young women.Projekt Operacyjny Polska Cyfrowa POPC.02.03.01-00-0039/1
Author's personal copy The relationship between n-back performance and matrix reasoning -implications for training and transfer ☆
No full textWe have previously demonstrated that training on a dual n-back task results in improvements in fluid intelligence (Gf) as measured by matrix reasoning tasks. Here, we explored the underlying mechanisms of this transfer effect in two studies, and we evaluated the transfer potential of a single n-back task. In the first study, we demonstrated that dual and single n-back task performances are approximately equally correlated with performance on two different tasks measuring Gf, whereas the correlation with a task assessing working memory capacity was smaller. Based on these results, the second study was aimed on testing the hypothesis that training on a single n-back task yields the same improvement in Gf as training on a dual n-back task, but that there should be less transfer to working memory capacity. We trained two groups of students for four weeks with either a single or a dual n-back intervention. We investigated transfer effects on working memory capacity and Gf comparing the two training groups' performance to controls who received no training of any kind. Our results showed that both training groups improved more on Gf than controls, thereby replicating and extending our prior results
BSA Practice guidance: an overview of current management of auditory processing disorder (APD)
No full textNeighbor stranger discrimination: A new defense mechanism against internet DDoS attacks
No full textDistributed Denial of Service (DDoS) attacks have become a real threat to the security of the Internet. Defending against DDoS is a challenging job, due to the use of IP spoofing and the destination-based routing of the Internet. Many solutions have been proposed, but none is able to completely stop an intense attack. In this paper we propose a new defense mechanism, Neighbor Stranger Discrimination (NSD), which is capable of stopping or significantly reducing the intensity of a DDoS attack. NSD can be incrementally deployed and satisfactory results are achieved even when it is implemented on a small percentage, 10percent to 20percent, of the Internet routers. The overhead of installing NSD on a certain router is low in terms of additional storage and processing load. Unlike other defense strategies, NSD produces no false positives while reducing false negatives. Being router-based, NSD also stops reflected DDoS attacks (RDDoS) since it discards the spoofed packets before they reach the reflectors. © 2005 IEEE.CHESWICK B, INTERNET MAPPING PRO; JIN C, P 10 ACM C COMP COMM, P30; MIRKOVIC J, TAXONOMY DDOS ATTACK; PERRIG A, 2003, P 2003 S SEC PRIV, P93; ZHANG S, DENYING DENIAL OF SE; ZHAOLE C, P 19 ANN COMP SEC AP0
Variation in mental models of text as a function of genre
No full text"This dissertation addresses the question ""Does text genre affect the characteristics of mental representations built from text?"" As early as the turn of last century writing teachers used text genre to classify textual styles in rhetoric textbooks. Recently researchers have suggested that the characteristics of mental models formed from one text genre would be different from the mental models formed from another genre (Brewer, 1980; Johnson-Laird, 1983). Readers of survey texts and route texts were faster and more accurate in verifying spatial information that was presented in the same form as the initial text (Perrig & Kintsch, 1985). The results suggest that the characteristics of mental models built from these two texts were different. Readers use different information to resolve ambiguity in order to determine ambiguous pronoun referents when narrative texts and descriptive texts were compared (Morrow, 1985, 1986). If the knowledge about text genre affects the process of mental model construction, does it also affect the characteristics of the mental model built from various genres?"In this dissertation, the characteristics of mental models built from three genres, descriptive, procedural, and narrative texts, which contain the same underlying spatial information, were examined by asking three types of inference questions. One hundred twenty-two undergraduate students read one of the three genres on a computer display and later answered inference questions about spatial information. Accuracy scores and response time data were examined. The results suggest that the mental model built from the Descriptive text differs from the models built from the other two genres and shows more two-dimensional characteristics. The readers were able to transform the mental model constructed from one genre of text to other forms of mental models in order to answer different types of inference questions. Therefore, the mental models built from text can be conceptualized as flexible representations that can be manipulated by readers rather than static, rigid structures that simply hold the textual information for retrieval.Made available in DSpace on 2011-05-07T14:05:42Z (GMT). No. of bitstreams: 2
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Bereavement or Breakup: Differences in Networks of Depression
No full textBackground. Prior network analyses demonstrated that the death of a loved one potentially precedes specific depression symptoms, primarily loneliness, which in turn links to other depressive symptoms. In this study, we extend prior research by comparing depression symptom network structures following two types of marital disruption: bereavement versus separation.
Methods: We fitted two Gaussian Graphical Models to cross-sectional data from a Swiss survey of older persons (145 bereaved, 217 separated, and 362 married controls), and compared symptom levels across bereaved and separated individuals.
Results: Separated compared to widowed individuals were more likely to perceive an unfriendly environment and oneself as a failure. Both types of marital disruption were strongly linked to loneliness, from where different relations emerged to other depressive symptoms. Amongst others, loneliness had a stronger connection to perceiving oneself as a failure in separated compared to widowed individuals. Conversely, loneliness had a stronger connection to getting going in widowed individuals.
Limitations: Analyses are based on cross-sectional between-subjects data, and conclusions regarding dynamic processes on the within-subjects level remain putative. Further, some of the estimated parameters in the network exhibited overlapping confidence intervals and their order needs to be interpreted with care. Replications should thus aim for studies with multiple time points and larger samples.
Conclusions: The findings of this study add to a growing body of literature indicating that depressive symptom patterns depend on contextual factors. If replicated on the within-subjects level, such findings have implications for setting up patient-tailored treatment approaches in dependence of contextual factors
