Generating dynamic higher-order Markov models in web usage mining

Markov models have been widely used for modelling users’ web navigation behaviour. In previous work we have presented a dynamic clustering-based Markov model that accurately represents second-order transition probabilities given by a collection of navigation sessions. Herein, we propose a generalisation of the method that takes into account higher-order conditional probabilities. The method makes use of the state cloning concept together with a clustering technique to separate the navigation paths that reveal differences in the conditional probabilities. We report on experiments conducted with three real world data sets. The results show that some pages require a long history to understand the users choice of link, while others require only a short history. We also show that the number of additional states induced by the method can be controlled through a probability threshold parameter

Ligand-Free Palladium-Catalyzed Oxyarylation of Dihydronaphthal­enes and Chromenequinone with o-Iodophenols and 3-Iodolawsone in PEG-400: An Efficient Synthesis of 5-Carbapterocarpans and Pterocarpanquinones

Dihydronaphthalenes were oxyarylated with o-iodophenols, in PEG-400 at 140 or 170 °C, leading regio- and stereoselectively to 5-carbapterocarpans. By using Pd(OAc)2 (5–10 mol%) as precatalyst and Ag2CO3 (1.1 equiv) as base (conditions A), products were obtained in good to excellent chemical yields, in 5–30 minutes, irrespective of the pattern of substitution the starting materials. Alternatively, when p-hydroxyacetophenone oxime derived palladacycle (1 mol%) was used as precatalyst, and dicyclohexylamine (2 equiv) was used as base (silver-free, conditions B), the corresponding adducts were obtained in moderate to good yields, in 0.5 to 4 hours. Finally, the oxyarylation of dihydronaphthalenes­ and chromenquinone with o-iodophenols and 3-iodolawsone in PEG-400 under conditions A led regio- and stereoselectively to the formation of carbapterocarpanquinones and pterocarpanquinones in moderate yield.Financial support from Brazilian agencies CAPES-DGU (Project 200/09), CNPq, FAPERJ and UFRJ are acknowledged. Spanish MICINN (Projects PHB2008-0037-PC, CTQ2007-62771/BQU, CTQ2010-20387, Consolider INGENIO 2010 CSD2007-00006), FEDER, Generalitat Valenciana (Project PROMETEO/2009/038), and the University of Alicante are acknowledged

Spike timing-dependent plasticity induces non-trivial topology in the brain.

We study the capacity of Hodgkin-Huxley neuron in a network to change temporarily or permanently their connections and behavior, the so called spike timing-dependent plasticity (STDP), as a function of their synchronous behavior. We consider STDP of excitatory and inhibitory synapses driven by Hebbian rules. We show that the final state of networks evolved by a STDP depend on the initial network configuration. Specifically, an initial all-to-all topology evolves to a complex topology. Moreover, external perturbations can induce co-existence of clusters, those whose neurons are synchronous and those whose neurons are desynchronous. This work reveals that STDP based on Hebbian rules leads to a change in the direction of the synapses between high and low frequency neurons, and therefore, Hebbian learning can be explained in terms of preferential attachment between these two diverse communities of neurons, those with low-frequency spiking neurons, and those with higher-frequency spiking neurons

Pancreatite aguda grave em centro de terapia intensiva: análise de 10 anos

OBJECTIVE: To evaluate etiology, complications, treatment, hospital and intensive care unit stay and mortality in all patients hospitalized in the intensive care unit of Hospital de Clínicas de Porto Alegre with acute pancreatitis, from January 1st, 1990 to December 31st, 1999. MATERIALS AND METHODS: We performed a historical cohort study with 57 patients, 37% female and 63% male, with an age average of 48±17 years. Patients were classified in two groups – survivors (n=26, 45.6%) and non-survivors (n=31, 54.4%) – and compared considering hospital and intensive care unit stay, Ranson’s and modified Glasgow’s signs, APACHE II (acute physiology and chronic health evaluation), organ failure, surgery, parenteral nutrition and antibiotics.RESULTS: The most common causes of severe acute pancreatitis were alcohol (37%) and gallstones (31%). Mortality was 54.4 %. Hospital stays were longer for survivors than for non-survivors. Non-survivors presented more organ failures (respiratory, renaland cardiovascular failures) and more Ranson’s and modified Glasgow’s signs than survivors. Other parameters were similar in both groups.CONCLUSIONS: In order to better evaluate the reasons for the high rate of mortality identified in the present group in the studied period it would be necessary to perform a prospective study with stronger control of the interfering factors, including an evaluation of the cases of severe acute pancreatitis that are not admitted in the intensive care unit.OBJETIVO: Avaliar etiologia, complicações, tratamento, tempo de internação – hospitalar e em centro de terapia intensiva – e mortalidade de todos os pacientes internados por pancreatite aguda no centro de tratamento intensivo do Hospital de Clínicas de Porto Alegre, no período de janeiro de 1990 a dezembro de 1999.MATERIAIS E MÉTODOS: Realizamos um estudo de coorte histórico, no qual foram avaliados 57 pacientes, 37% do sexo feminino e 63% do sexo masculino, com média de idade de 48 ± 17 anos. Os pacientes foram divididos em dois grupos – sobreviventes (n=26;45,6%) e não-sobreviventes (n=31;54,4%) –, e foram comparados quanto a tempo de internação, critérios de Ranson e de Glasgow modificados, APACHE II (acute physiology and chronic health evaluation), falências orgânicas, procedimentos cirúrgicos, nutrição parenteral e antibióticos recebidos.RESULTADOS: As etiologias mais freqüentes foram alcoólica (37%) e biliar (31%). A mortalidade foi de 54,4%. Os sobreviventes apresentaram maior tempo de internação que os não-sobreviventes (47 ± 36 dias contra 21 ± 20 dias). Os não-sobreviventes apresentaram maiores taxas de falências orgânicas (respiratória, renal e cardiovascular) e maior número de critérios de Ranson e de Glasgow modificados, quando comparados aos sobreviventes. Os parâmetros restantes foram semelhantes entre os dois grupos.CONCLUSÕES: Para melhor avaliar os motivos da alta taxa de mortalidade identificada neste grupo, neste período, seria necessário um trabalho prospectivo com melhor controle dos fatores interferentes e que incluísse ainda a avaliação dos casos de pancreatite aguda com critérios de gravidade que não são admitidos no centro de tratamento intensivo

Thermostatistics of deformed bosons and fermions

Based on the q-deformed oscillator algebra, we study the behavior of the mean occupation number and its analogies with intermediate statistics and we obtain an expression in terms of an infinite continued fraction, thus clarifying successive approximations. In this framework, we study the thermostatistics of q-deformed bosons and fermions and show that thermodynamics can be built on the formalism of q-calculus. The entire structure of thermodynamics is preserved if ordinary derivatives are replaced by the use of an appropriate Jackson derivative and q-integral. Moreover, we derive the most important thermodynamic functions and we study the q-boson and q-fermion ideal gas in the thermodynamic limit.Comment: 14 pages, 2 figure

Cat epididymal semen cryopreserved with and without vitamin E: effect on sperm parameters and lipid peroxidation

The aims of this study were to investigate: 1) if the addition of \u3b1-tocopherol (vitamin E) in three concentrations (0.3, 0.6 and 0.9 mM) is able to preserve spermatozoa integrity after thawing and 2) the effect of \u3b1-tocopherol supplementation on lipid peroxidation. Fifty four domestic cats were used in this study constituting 18 pools (3 cats per pool). Each pool was submitted at four experimental groups: group 0 (control) \u2013 epididymal sperm were frozen with a commercial Botucrio\uae extender; group 0.3, group 0.6 and group 0.9 \u2013 the extender was supplemented with 0.3, 0.6 and 0.9 mM of \u3b1-tocopherol, respectively. Each semen sample was evaluated for motility, progressive forward motility, morphology, sperm viability (plasma membrane integrity-PMI), hypo-osmotic swelling test (HOST), before and after thawing. The evaluation of lipid peroxidation reaction by Thiobarbituric Acid Reactive Substances (TBARS) test was performed on thawed semen only. Results demonstrated that there was no significant difference between control and the three \u3b1-tocopherol groups with regards to motility and progressive motility after thawing (P > 0.05). As expected, in fresh samples viability was significantly higher than in all the cryopreserved groups in which there was no positive influence of any of the \u3b1-tocopherol concentration used. Lipid peroxidation was higher in the supplemented groups 0.6 and 0.9 mM of \u3b1-tocopherol than in control and in 0.3 mM group. In conclusion, the addition of \u3b1-tocopherol to the commercial extender had no positive influence on reduction of lipid peroxidation. This topic deserves further investigations to better understand the effect of cryopreservation procedures on epididymal spermatozoa and to establish adequate strategies to counteract sperm cryodamages