Symbolic knowledge extraction from trained neural networks: A sound approach

Although neural networks have shown very good performance in many application domains, one of their main drawbacks lies in the incapacity to provide an explanation for the underlying reasoning mechanisms. The “explanation capability” of neural networks can be achieved by the extraction of symbolic knowledge. In this paper, we present a new method of extraction that captures nonmonotonic rules encoded in the network, and prove that such a method is sound. We start by discussing some of the main problems of knowledge extraction methods. We then discuss how these problems may be ameliorated. To this end, a partial ordering on the set of input vectors of a network is defined, as well as a number of pruning and simplification rules. The pruning rules are then used to reduce the search space of the extraction algorithm during a pedagogical extraction, whereas the simplification rules are used to reduce the size of the extracted set of rules. We show that, in the case of regular networks, the extraction algorithm is sound and complete. We proceed to extend the extraction algorithm to the class of non-regular networks, the general case. We show that non-regular networks always contain regularities in their subnetworks. As a result, the underlying extraction method for regular networks can be applied, but now in a decompositional fashion. In order to combine the sets of rules extracted from each subnetwork into the final set of rules, we use a method whereby we are able to keep the soundness of the extraction algorithm. Finally, we present the results of an empirical analysis of the extraction system, using traditional examples and real-world application problems. The results have shown that a very high fidelity between the extracted set of rules and the network can be achieved

Modelling strong seismic ground motion: three-dimensional loading path versus wavefield polarization

Seismic waves due to strong earthquakes propagating in surficial soil layers may both reduce soil stiffness and increase the energy dissipation into the soil. To investigate seismic wave amplification in such cases, past studies have been devoted to one-directional shear wave propagation in a soil column (1D-propagation) considering one motion component only (1C-polarization). Three independent purely 1C computations may be performed ('1D-1C' approach) and directly superimposed in the case of weak motions (linear behaviour). This research aims at studying local site effects by considering seismic wave propagation in a 1-D soil profile accounting for the influence of the 3-D loading path and non-linear hysteretic behaviour of the soil. In the proposed '1D-3C' approach, the three components (3C-polarization) of the incident wave are simultaneously propagated into a horizontal multilayered soil. A 3-D non-linear constitutive relation for the soil is implemented in the framework of the Finite Element Method in the time domain. The complex rheology of soils is modelled by mean of a multisurface cyclic plasticity model of the Masing-Prandtl-Ishlinskii-Iwan type. The great advantage of this choice is that the only data needed to describe the model is the modulus reduction curve. A parametric study is carried out to characterize the changes in the seismic motion of the surficial layers due to both incident wavefield properties and soil non-linearities. The numerical simulations show a seismic response depending on several parameters such as polarization of seismic waves, material elastic and dynamic properties, as well as on the impedance contrast between layers and frequency content and oscillatory character of the input motion. The 3-D loading path due to the 3C-polarization leads to multi-axial stress interaction that reduces soil strength and increases non-linear effects. The non-linear behaviour of the soil may have beneficial or detrimental effects on the seismic response at the free surface, depending on the energy dissipation rate. Free surface time histories, stress-strain hysteresis loops and in-depth profiles of octahedral stress and strain are estimated for each soil column. The combination of three separate 1D-1C non-linear analyses is compared to the proposed 1D-3C approach, evidencing the influence of the 3C-polarization and the 3-D loading path on strong seismic motions

Mammalian sialidase Neu3 overexpression in Cos-7 cells : effects on Newcastle disease virus-cell interaction

Newcastle Disease Virus (NDV) is an avian single-stranded RNA enveloped virus that belongs to the Paramyxoviridae family. The interaction of enveloped viruses with cell surface receptors is the first step in the viral cycle and an important determinant of viral host range. Although it is estabilished that NDV, such as the most of Paramyxovirus, infects cells binding sialic acid-containing glycoconjugates, the exact nature of these receptors is not well known. It is thought that both sialoglycoproteins and gangliosides may serve as viral receptors. Infection by NDV requires the combined action of its two glycoproteins: the hemagglutinin-neuraminidase (HN) protein and the fusion (F) protein. HN protein has three main biological activities: hemagglutinin, sialidase and fusion promotion. The hemagglutinin activity allows the binding of the virus to the host cell surface by recognizing specific cellular receptors. The sialidase activity facilitates the viral spread of newly born virions, while the fusion promotion activity induces F protein to begin the fusion between the virus and host membranes. After fusion, viral nucleocapsid is delivered into the cytoplasm and here the replication cycle takes place. After synthesis, once correctly folded and assembled, HN and F are transported to the host plasma membrane. F protein is synthetized as a precursor, Fo, and it becomes fusogenic only after cleavage into disulfide-linked F1 and F2 polypeptide before catching up the host membrane (Iwata et al., 1994). The NDV clone used in our experiments is \u201cClone 30\u201d that belongs to the lentogenic group. The lentogenic viruses\u2019 F protein can be cleaved only by tripsin-like enzyme. In this work we investigated the effects caused by mammalian sialidase Neu3 overexpression in COS7 cells in terms of NDV infection, NDV-cell interaction and its entry. First, we studied if the overexpression of Neu3 sialidase could interfere with the virus entry. To this end, we performed immunofluorescence assays in collaboration with the Department of Biochemistry and Molecular Biology of the University of Salamanca, and we observed that NDV infection was reduced (19%) in Neu3 overexpressing COS7 cells compared to controls. Because Neu3 sialidase is mainly located in regions of the membrane named \u201clipid rafts\u201d (Simons et al., 1997), we studied the possible involvement of these domains in the infection process by Western Blot analysis and HN activity assays. Mock and Neu3 overexpressing COS7 infected with 1 moi of NDV at 4\ub0C were collected after infection. Cell lysates were separated on an optiprep gradient. The 8 collected fractions were analyzed for sialidase activity toward Mu-NeuAc substrate and by western blot with antibodies a-caveolin 1 and a-NDV. We observed that NDV\u2019s neuraminidase is concentrated in the fraction corresponding to that of lipid rafts. Gangliosides have been identified as key receptors for some of caveolae-dependent viruses, such as for the polyomaviruses SV40 and Py (Tsai et al., 2003). Since it has been reported that NDV interacts with several gangliosides bearing both the Neu5 Ac and N-glycolylneuraminic sialic acid forms (Suzuky et al., 1985) and in vitro with different monosialogangliosides, disialogangliosides and trisialogangliosides, carrying sialic acid residues attached to a terminal or internal galactose (Ferreira et al.,2004), we tried to delineate if one or more gangliosides may act as receptors. We made a metabolic labelling with [1-3H]Sphingosine with a 2h pulse followed by a 48h chase; at 24h of chase cells were infected with NDV at 1 or 10 moi at 37\ub0C and collected after infection. Total lipids from lyophilized cells were extracted. [3H]Sphingolipids from aqueous and organic phases were separated by HPTLC. No differences could be detected between infected cells and controls in both aqueous and organic phases. It seems that NDV probably only hydrolize a very small number of sialo-glycosphingolipid to infect COS7 cells. Subsequently, we defined the glycosphingolipid pattern of COS7 cells at 24h post-infection, and we could observe a 50% decrease of GD1a accompained by a 46% increase of GM1 in infected cells compared to controls. This suggests that the newly syntetized HN specifically hydrolizes GD1a present on the host\u2019s surface to allow the virus spread by budding. To be sure that newly syntetized HN hydrolized only GD1a present on the host cell surface, we labelled COS7 with [1-3H]Sphingosine with a 2h pulse followed by a 48h chase: at 24h of chase, we made a co-colture for 24h of the labeled cells with COS7 cells infected by NDV. Analyzing the lipids from aqueous and organic phases, we could observe that GD1a of neighboring cells wasn\u2019t hydrolized by HN present on the infected cell\u2019s surface. The present study demonstrates that: \uf0d8 The overexpression of Neu3 sialidase leads to a decrease in the ability of NDV to infect host cells. \uf0d8 NDV\u2019s neuraminidase (HN) co-localizes with lipid rafts. \uf0d8 NDV\u2019s neuraminidase acts preferentially on ganglioside GD1a of host cells. GD1a of neighboring cells is not hydrolized by HN present on the infected cell\u2019s surface. Iwata et al.,(1994), J Virol. 68, 3200-3206 Simons et al., (1997) Nature 387, 569-572 Suzuky et al., (1985) JB 97,1189-1199 Ferreira et al., (2004) ICBCB 36, 2344-235

O ensino superior como projeto profissional para "ser alguém": repercussões de um cursinho pré-vestibular popular na vida dos estudantes

Dissertação (mestrado) - Universidade Federal de Santa Catarina, Centro de Filosofia e Ciências Humanas. Programa de Pós-Graduação em Psicologia.Esta pesquisa tem como objetivo identificar quais as repercussões no projeto profissional de estudantes a partir de seu ingresso, em 2005, no Cursinho Pré-Vestibular Popular da Universidade Federal de Santa Catarina. Considerando a abordagem qualitativa, a entrevista semi-estruturada foi o instrumento para a coleta de dados. Os sujeitos foram sete alunos do Cursinho, sendo quatro mulheres e três homens, com idades entre 18 e 22 anos. Os achados da pesquisa, tratados com base na técnica de análise de conteúdo, permitiram identificar três grandes temas: o ensino superior; o projeto; e as repercussões do Cursinho para a vida dos sujeitos. Desses temas, emergiram sete categorias de análise, a saber: (a) as razões para o ingresso no ensino superior e (b) o acesso a esse ensino; (c) o futuro; (d) o projeto profissional; (e) a visão dos alunos; (f) a importância de terem sido "escolhidos"; e (g) as contribuições para a sua vida e seu futuro. Optar pelo ingresso no ensino superior é uma forma de incluir-se no mercado de trabalho, mediante a profissionalização, numa tentativa de ascensão no tecido social. Essa tentativa é decorrente do medo de permanecer à margem de algumas áreas da sociedade. O caminho de acesso à universidade brasileira, sobretudo nas instituições federais, está atrelado ao exame vestibular e é considerado longo e árduo. Projetar o futuro profissional significa entrar em contato, inicialmente, com um "grande vazio", com a dúvida e a incerteza, mas significa também se relacionar com o passado e com o momento presente, situação em que predomina o pensamento otimista com relação ao futuro. O projeto de vida e o profissional, indissociáveis, direcionam-se para as escolhas de vida dos sujeitos, no entanto as condições sociais interferem fortemente em sua elaboração. A visão dos estudantes sobre o Cursinho é a melhor possível, sendo citados como aspectos diferenciais de outros pré-vestibulares a gratuidade e a localização. O Cursinho configurou-se como mais que uma oportunidade de acesso e preparação para o ingresso na universidade, sendo considerado o alunado como "vestibulando" desde o momento da entrada no referido curso. A inserção nesse pré-vestibular repercutiu positivamente e de forma imediata na vida dos participantes, transformando alguns de seus valores e visões de mundo, bem como resgatando e atualizando projetos que, anteriormente, estavam "esquecidos". Em síntese, o projeto profissional de ingressar no ensino universitário torna-se fundamental para atingir o projeto de vida de "ser alguém", sendo o Cursinho uma ferramenta para o aumento da inclusão social

Uma justiça penal internacional sem os Estados Unidos da América

As sociedades e as nações dos nossos dias estão violentamente confrontadas com questões de genocídio, limpeza étnica e crimes de guerra. Uma das respostas da comunidade internacional traduziu- se na criação do primeiro Tribunal Penal Internacional com carácter permanente, cuja criação ficou marcada pela contradição entre um velho Soberanismo/ /Estatismo e um novo Comunitarismo/Universalismo. A não ratificação do Estatuto de Roma pelos Estados Unidos da América e a sua posição controversa suscitou um acesso debate internacional, centrado nas seguintes questões: “Terá futuro uma Justiça Penal Internacional sem os Estados Unidos da América?” “Vale ou não vale a pena uma Justiça Penal Internacional sem os Estados Unidos da América?” Quais os argumentos principais da escolha americana, quais os seus efeitos, a sua estratégia anti-TPI e, sobretudo, as consequências desta decisão no actual contexto internacional de novas e diferentes ameaças? Terão perdido os Estados Unidos da América o seu papel de Estado-central na Segurança e Defesa Mundial? Conclui-se, assim, procurando-se desmistificar alguns dos argumentos anti-TPI, que a criação deste Tribunal representa uma lufada de ar fresco na História do Direito Internacional e um contributo decisivo para a implementação de uma jurisdição penal universal, seja no quadro de adesão ou não adesão dos Estados Unidos da América, assumindo-se, simultaneamente, que só o respeito dos Estados pelo Direito Internacional permitirá assegurar a Defesa da Humanidade e a Defesa do Património Cultural comum representativo do passado, do presente e do futuro

Social reform in the fiction of Charlotte Perkins Gilman and Olive Schreiner

Dissertação (mestrado) - Universidade Federal de Santa Catarina. Centro de Comunicação e ExpressãoUma das contribuições da crítica feminista tem sido a redescoberta de escritoras que foram por alguma razão esquecidas ou subestimadas nos meios intelectuais e literários. A presente dissertação aborda duas dessas mulheres, (Charlotte Perkins Gilman e Olive Schreiner). Há um século atrás estavam no auge de suas atividades como ativistas sociais, conferencistas, defensoras do movimento de mulheres e escritoras. Nesta dissertação busco resgatar a importância de Gilman e Schreiner durante a época em que viveram discutindo algumas das idéias desenvolvidas nas suas mais influentes obras teóricas