A dynamic overproduce-and-choose strategy for the selection of classifier ensembles

The overproduce-and-choose strategy, which is divided into the overproduction and selection phases, has traditionally focused on finding the most accurate subset of classifiers at the selection phase, and using it to predict the class of all the samples in the test data set. It is therefore, a static classifier ensemble selection strategy. In this paper, we propose a dynamic overproduce-and-choose strategy which combines optimization and dynamic selection in a two-level selection phase to allow the selection of the most confident subset of classifiers to label each test sample individually. The optimization level is intended to generate a population of highly accurate candidate classifier ensembles, while the dynamic selection level applies measures of confidence to reveal the candidate ensemble with the highest degree of confidence in the current decision. Experimental results conducted to compare the proposed method to a static overproduce-and-choose strategy and a classical dynamic classifier selection approach demonstrate that our method outperforms both these selection-based methods, and is also more efficient in terms of performance than combining the decisions of all classifiers in the initial pool.     

A dynamic optimization approach for adaptive incremental learning

A fundamental problem when performing incremental learning is that the best set of a classification system's parameters can change with the evolution of the data. Consequently, unless the system self‐adapts to such changes, it will become obsolete, even if the application environment seems to be static. To address this problem, we propose a dynamic optimization approach in this paper that performs incremental learning in an adaptive fashion by tracking, evolving, and combining optimum hypotheses overtime. The approach incorporates various theories, such as dynamic particle swarm optimization, incremental support vector machine classifiers, change detection, and dynamic ensemble selection based on classifiers' confidence levels. Experiments carried out on synthetic and real‐world databases demonstrate that the proposed approach actually outperforms the classification methods often used in incremental learning scenarios. © 2011 Wiley Periodicals, Inc.     

Vegetational association of host-seeking adult blacklegged ticks, Ixodes scapularis Say (Acari: Ixodidae), on dairy farms in northwestern Wisconsin

Non-obese diabetic NOD/SCID mice have been used to grow human leukaemia as a systemic disease. The animals were inoculated with leukaemic cells obtained from a 36-year-old male with early B-cell precursor acute lymphoblastic leukaemia and on day 15 were given the first of three weekly injections of 1 mg/kg vincristine or equimolar liposomal vincristine. The development of leukaemia in the mice was monitored by taking weekly blood samples and measuring the cell content by flow cytometry. The median time to 50% human cells in the peripheral blood of mice treated with free vincristine was 41 d from the start of treatment compared with 49 d for mice treated with liposomal vincristine (P < 0.01). The median day of death for mice treated with free vincristine was 47 d from the start of treatment and 57 d for mice receiving liposomal vincristine (P<0.01), thus providing a 21% increase in lifespan for animals treated with the liposomal preparation. There was slightly greater weight loss in mice treated with free vincristine than those given liposomal vincristine. Measurement of in vitro colony forming bone marrow progenitor cells in similarly treated, tumour-free mice, showed no difference in progenitor cell survival between mice that received either type of vincristine. We conclude that encapsulating vincristine in liposomes improves the therapeutic index of this drug measured in mice bearing human leukaemia. This may lead to use of the drug in conventional combination chemotherapy with greater safety or, in this setting, at higher dosage.     

Alpha-catenin can form asymmetric homodimeric complexes and/or heterodimeric complexes with beta-catenin

The cadherin-based transmembrane cell-cell adhesive complex is thought to be composed of a cadherin molecule, a beta-catenin, and an alpha-catenin, which connects the complex to the cytoskeleton. The precise stoichiometry of this complex remains uncertain. We have used a series of recombinant molecules and biophysical techniques to assess the multimeric state of human alpha- and beta-catenin in vitro and then visualized them by electron microscopy after rotary shadowing. Calculated solution molecular masses are 213 kDa for alpha-catenin, 73 kDa for beta-catenin, and 186 kDa for both. This suggests that alpha-catenin exists as a homodimer in solution, beta-catenin is a monomer, and when both are present, they form alpha/beta-catenin heterodimers. Co-precipitation and surface plasmon resonance assays localize the site of alpha-catenin dimerization to the NH2-terminal 228 amino acids. This region encompasses a high-affinity (Kd = 100 nM) binding site for beta-catenin that lies between residues 54 and 157. We anticipate that the oligomeric state of alpha-catenin and the relative stoichiometry of the components in the membrane adhesion complex will be dynamic and regulated by beta-catenin, cell adhesion, and probably other factors as well.     

Individual differences in response to a Zen meditation exercise.

In order to explore the psychological functions involved in meditation, 28 male college student volunteers were instructed in a concentration exercise related to Zen Buddhist procedures. Their response to the exercise was rated as high, moderate, and low from verbal reports taken after daily 45-min. sessions over a 2-3 wk. period. Response was then compared with premeditation test results related to attention, tolerance for unrealistic experience, and capacity for regression in the service of the ego (derived from Rorschach expressions of "primary process" and from spontaneous visual imagery). Capacity for regression and tolerance for unrealistic experience significantly predicted response to meditation, while attention measures did not. Once issues related to comfort in the face of strange inner experience are resolved, attention functions necessary to the exercise probably became available. (15 ref.) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Two new coccidian parasites from the grand anglehead lizard, Gonocephalus grandis from Peninsular Malaysia

During 3 collecting expeditions between October 1996 and December 1996, fecal samples were obtained from 43 adult Gonocephalus grandis from Tanah Rata and the Cameron Highlands in Peninsular Malaysia. Two species of coccidia (Isospora gonocephali n. sp. [9/43, 23%] and Eimeria cameronensis n. sp. [3/43, 7%]) were discovered. Sporulated oocysts of I. gonocephali are subspherical to ovoidal, 22.3 x 18.7 (19-25 x 17-23) microm with a bilayered wall composed of a thin inner wall and a striated outer wall with a pitted surface; oocyst residuum absent; 1 polar granule present; sporocysts are almond-shaped, 13.5 x 9.2 (12-15 x 8.5-10) microm, Stieda body broad, domelike, substieda body fanlike, sporocyst residuum consisting of coarse, nonuniform granules in an amorphous cluster; sporozoites sausage-shaped with 1 large terminal, refractile body and lay randomly in the sporocyst. Sporulated oocysts of E. cameronensis are bilayered, smooth-walled, ellipsoidal, 26.5 x 12.4 (25-28 x 12-13) microm; with 1, small, polar granule composed of 2-3 splinter-like structures fused together; oocyst residuum absent; sporocysts ovoidal, almost rectangular-shaped 8.8 x 6.6 (8-9 x 5-7) microm, with no Stieda or substieda bodies, containing scattered residuum and 2 sausage-shaped sporozoites with 1 terminal, ovoidal refractile body. No individual lizard was host to both coccidian species.     

Dynamics of plague in a Gunnison's prairie dog colony complex from New Mexico

A plague (Yersinia pestis) epizootic spread through Gunnison's prairie dogs (Cynomys gunnisoni), and possibly other rodent species, in the Moreno Valley in north-central New Mexico between winter 1984-1985 and autumn 1987. We observed the progress of the epizootic and subsequent population recovery at four prairie dog towns within the valley during this period. At two towns (Midlake and Val Verde) the prairie dogs were marked prior to the epizootic. At two additional towns (Vega and South Entrance) prairie dogs were marked following the epizootic. In 1988, a second epizootic occurred at Vega. One hundred thirty-nine serum samples were collected from prairie dogs and other rodents and 1,750 fleas were collected from animals and burrows. Fleas infected with Y. pestis were collected from prairie dogs, deer mice (Peromyscus maniculatus), and thirteen-lined ground squirrels (Spermophilus tridecemlineatus). Prairie dog fleas included Oropsylla hirsuta, O. labis and O. tuberculata, deermouse associated fleas were Aetheca wagneri and Rhadinopsylla sectilis, and Oropsylla bacchi was associated with thirteen-lined ground squirrels. All of the above flea species were collected from prairie dog burrows. All rodent species shared some flea species. Thirteen-lined ground squirrels disappeared shortly before plague was identified in prairie dogs at Midlake. Meadow voles were rare following the epizootic at Vega in 1986, became abundant in 1987, and disappeared at the time of the second prairie dog epizootic in summer 1988. Although we collected serum from Gunnison's prairie dogs, thirteen-lined ground squirrels, deer mice, and meadow voles (Microtus pennsylvanicus), we identified elevated serum titers against Y. pestis only in Gunnison's prairie dogs. Prairie dog mortality at all towns affected by plague was in excess of 99%. Serum antibody titers indicate that more than 40% of the few prairie dogs left to establish colonies following epizootics survived plague infection.     

The effects of superior female performance and sex-role orientation on gender conformity.

Assessed the effects of gender, sex-role orientation, and demonstrated female task superiority on influenceability in 54 mixed-gender dyads. The dependent variable was the number of items changed on a social judgment questionnaire subsequent to the influence attempt. The female superiority manipulation rather than gender- or sex-role orientation emerged as the strongest factor in determining influenceability. As predicted, the gender-relatedness of the measuring instrument also played an important role, with females conforming more on masculine items and males conforming more on feminine items. Results are interpreted as consistent with expectation states theory. (French abstract) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

The pillaring effect of the 1,2-dimethyl-3(benzyl ethyl iso-butyl POSS) imidazolium cation in polymer/montmorillonite nanocomposites

A polyhedral oligomeric silsesquioxane (POSS) tethered imidazolium surfactant was used to exchange montmorillonite for the preparation of polymer nanocomposites in polystyrene, poly(ethylene-co-vinyl acetate), and polyamide-6 using a melt blending technique. Simultaneous temperature resolved small angle X-ray scattering and wide angle X-ray diffraction was used to monitor the surfactant stability and phase behavior of the polyamide-6 nanocomposites. Good thermal stability of the surfactant was in agreement with thermogravimetric analysis. Transmission electron microscopy revealed a mixed intercalated/exfoliated structure, with the presence of small tactoids exhibiting gallery spacings greater than 3.8 nm in all three polymers. Fluorescently tagged organically exchanged montomorillonite was used to assess the quality of nanoparticle dispersion. Exchanging the montmorillonite with lower loadings of the POSS surfactant slightly increased the size of clay tactoids, but did not significantly alter the gallery spacing or overall dispersion. The results suggest that the bulky and rigid structure of POSS, as well as its tendency to aggregate into ordered crystals, form a bilayer structure in the clay galleries and prevent montmorillonite from completely exfoliating, even in polyamide-6.