Efficiency issues of evolutionary k-means

One of the top ten most influential data mining algorithms, k-means, is known for being simple and scalable. However, it is sensitive to initialization of prototypes and requires that the number of clusters be specified in advance. This paper shows that evolutionary techniques conceived to guide the application of k-means can be more computationally efficient than systematic (i.e., repetitive) approaches that try to get around the above-mentioned drawbacks by repeatedly running the algorithm from different configurations for the number of clusters and initial positions of prototypes. To do so, a modified version of a (k-means based) fast evolutionary algorithm for clustering is employed. Theoretical complexity analyses for the systematic and evolutionary algorithms under interest are provided. Computational experiments and statistical analyses of the results are presented for artificial and text mining data sets. (C) 2010 Elsevier B.V. All rights reserved.

Mass spectral characterization of submicron biogenic organic particles in the Amazon Basin

Submicron atmospheric particles in the Amazon Basin were characterized by a high-resolution aerosol mass spectrometer during the wet season of 2008. Patterns in the mass spectra closely resembled those of secondary-organic-aerosol (SOA) particles formed in environmental chambers from biogenic precursor gases. In contrast, mass spectral indicators of primary biological aerosol particles (PBAPs) were insignificant, suggesting that PBAPs contributed negligibly to the submicron fraction of particles during the period of study. For 40% of the measurement periods, the mass spectra indicate that in-Basin biogenic SOA production was the dominant source of the submicron mass fraction, contrasted to other periods (30%) during which out-of-Basin organic-carbon sources were significant on top of the baseline in-Basin processes. The in-Basin periods had an average organic-particle loading of 0.6 mu g m(-3) and an average elemental oxygen-to-carbon (O:C) ratio of 0.42, compared to 0.9 mu g m(-3) and 0.49, respectively, during periods of out-of-Basin influence. On the basis of the data, we conclude that most of the organic material composing submicron particles over the Basin derived from biogenic SOA production, a finding that is consistent with microscopy observations made in a concurrent study. This source was augmented during some periods by aged organic material delivered by long-range transport. Citation: Chen, Q., et al. (2009), Mass spectral characterization of submicron biogenic organic particles in the Amazon Basin, Geophys. Res. Lett., 36, L20806, doi: 10.1029/2009GL039880.

Metastable Periodic Patterns in Singularly Perturbed Delayed Equations

We consider the scalar delayed differential equation epsilon(x) over dot(t) = -x(t) + f(x(t-1)), where epsilon > 0 and f verifies either df/dx > 0 or df/dx < 0 and some other conditions. We present theorems indicating that a generic initial condition with sign changes generates a solution with a transient time of order exp(c/epsilon), for some c > 0. We call it a metastable solution. During this transient a finite time span of the solution looks like that of a periodic function. It is remarkable that if df/dx > 0 then f must be odd or present some other very special symmetry in order to support metastable solutions, while this condition is absent in the case df/dx < 0. Explicit epsilon-asymptotics for the motion of zeroes of a solution and for the transient time regime are presented.

Estimating abundance and spatial distribution patterns of the bubble crab Dotilla fenestrata (Crustacea : Brachyura)

The bubble crab Dotilla fenestrata forms very dense populations on the sand flats of the eastern coast of Inhaca Island, Mozambique, making it an interesting biological model to examine spatial distribution patterns and test the relative efficiency of common sampling methods. Due to its apparent ecological importance within the sandy intertidal community, understanding the factors ruling the dynamics of Dotilla populations is also a key issue. In this study, different techniques of estimating crab density are described, and the trends of spatial distribution of the different population categories are shown. The studied populations are arranged in discrete patches located at the well-drained crests of nearly parallel mega sand ripples. For a given sample size, there was an obvious gain in precision by using a stratified random sampling technique, considering discrete patches as strata, compared to the simple random design. Density average and variance differed considerably among patches since juveniles and ovigerous females were found clumped, with higher densities at the lower and upper shore levels, respectively. Burrow counting was found to be an adequate method for large-scale sampling, although consistently underestimating actual crab density by nearly half. Regression analyses suggested that crabs smaller than 2.9 mm carapace width tend to be undetected in visual burrow counts. A visual survey of sampling plots over several patches of a large Dotilla population showed that crab density varied in an interesting oscillating pattern, apparently following the topography of the sand flat. Patches extending to the lower shore contained higher densities than those mostly covering the higher shore. Within-patch density variability also pointed to the same trend, but the density increment towards the lowest shore level varied greatly among the patches compared.

Abundance of sedentary consumers and sessile organisms along the wave exposure gradient of subtropical rocky shores of the south-west Atlantic

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Padrão de distribuição de K+, Ca++, Mg++ e P no solo de um pomar de citros em função da fertirrigação

Em solos tropicais, a distribuição dos nutrientes no solo em função da fertirrigação realizada por meio de irrigação localizada (gotejamento e/ou microaspersão), na cultura de citros, é pouco conhecida. Este trabalho teve por objetivo avaliar os padrões de distribuição de potássio, cálcio, magnésio e fósforo em solo tropical, em função da fertirrigação, aplicada por dois sistemas de irrigação localizada (microaspersão e gotejamento), sendo que o sistema por gotejamento era composto por uma e duas linhas laterais por linha de plantas, e o de microaspersão por apenas uma linha, e com três dotações hídricas (100%, 75% e 50%) da evapotranspiração da cultura (ETc), em um pomar de laranjeira. As fontes de fertilizantes utilizadas na fertirrigação foram o nitrato de amônio (fonte de N), o cloreto de potássio (fonte de K+) e o ácido fosfórico (fonte de P). Observouse que, sob o emissor, nos tratamentos com gotejamento, houve depleção nos teores de Ca++ e Mg++ desde a superfície do solo até 60 cm de profundidade em relação aos teores anteriores às fertirrigações, enquanto os teores de P aumentaram, principalmente na camada de 0 cm a 20 cm. Na microaspersão, esses efeitos não foram observados, ocorrendo distribuição mais homogênea desses nutrientes tanto na direção transversal à linha de plantas quanto em profundidade. As lâminas de irrigação aplicadas por irrigação localizada não interferem na distribuição de K+ aplicado por fertirrigação e do Ca++ e Mg++ no solo em profundidade, porém menores lâminas de irrigação promovem maior concentração de P na camada mais superficial do solo, e lâminas maiores carregam o P para camadas mais profundas.

Impacts of limestone and nitrogen top dressing application on the potassium content in the soil profile and marandu-grass leaf concentration

Objetivou-se avaliar os efeitos de nitrogênio (0, 100, 200, 300 e 400 kg/ha.ano), com ou sem aplicação de calcário dolomítico em cobertura, sobre o teor de potássio (K) do solo nas profundidades de 0 a 5; 5 a 10; e 10 a 20 cm e a concentração de potássio na planta. O experimento foi realizado em Latossolo Vermelho distroférrico de relevo suavemente ondulado, disposto em esquema fatorial 5 × 2, em blocos casualizados, com quatro repetições. A adubação nitrogenada promoveu aumento linear na concentração de potássio na planta e no teor desse mineral na camada de 0 a 5 cm do solo. Ocorreu efeito de inibição competitiva entre a absorção de potássio e cálcio e entre potássio e magnésio. Embora uma fração significativa de potássio retorne à camada superficial do solo pelo resíduo de forragem, em decorrência da maior produção de massa, o aumento da concentração de potássio na planta nas mais altas doses de nitrogênio comprova a importância do suprimento de potássio para a planta, por intensificar a massa de forragem.

Contraste fônico encoberto entre /t/ e /k/: um estudo de caso de normalidade e de transtorno fonológico

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

No mutations found in exons of TP53, H-RAS and K-RAS genes in liver of male Wistar rats submitted to a medium-term chemical carcinogenesis assay

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Fish ladders select fish traits on migration - still a growing problem for natural fish populations

We investigated the potential selective effect of fish ladders on physiological and morphological profiles of the curimbata, Prochilodus lineatus, during reproductive migration in Brazil. We registered sex, body weight and length, plasma glucose, hepatosomatic and gonadosomatic indices (HSI and GSI, respectively), hematocrit, leucocrit, blood cell and nucleus areas, and the diameter of white and red muscle fibers in fish sampled at the bottom (downstream) and at the top (upstream) of a fish ladder at a hydroelectric dam. Males and females at the top of the ladder showed higher size (weight and length), white muscle fiber diameters, plasma glucose levels and lower hematocrit when compared with those at the bottom. These size and muscle traits assist fish to overcome the ladder barrier and bypass the dam, an effort that might be reflected in the glucose levels. Females also showed higher GSI at the top of the fish ladder, a trait possibly facilitating their reproduction upstream. These results indicate that a dam system favors fish with specific morphological-physiological profile. This may have a strong influence upon upstream fish populations over generations and implies the presence of artificial selective pressure.

Seasonal changes in daily metabolic patterns of tegu lizards (Tupinambis merianae) placed in the cold (17 degrees C) and dark

Oxygen consumption rate was measured continuously in young tegu lizards Tupinambis merianae exposed to 4 d at 25 degrees C followed by 7-10 d at 17 degrees C in constant dark at five different times of the year. Under these conditions, circadian rhythms in the rate of oxygen consumption persisted for anywhere from 1 d to the entire 2 wk in different individuals in all seasons except the winter. We also saw a progressive decline in standard oxygen consumption rate (at highly variable rates in different individuals) to a very low rate that was seasonally independent (ranging from 19.1 +/- 6.2 to 27.7 +/- 0.2 mL kg(-1) h(-1) across seasons). Although this degree of reduction appeared to take longer to invoke when starting from higher metabolic rates, tegu lizards reduced their metabolism to the low rates seen in winter dormancy at all times of the year when given sufficient time in the cold and dark. In the spring and summer, tegus reduced their standard metabolic rate (SMR) by 80%-90% over the experimental run, but only roughly 20%-30% of the total fall was due to the reduction in temperature; 70%-80% of the total fall occurred at constant temperature. By autumn, when the starting SMR on the first night at 25 degrees C was already reduced by 59%-81% (early and late autumn, respectively) from peak summer values, virtually all of the fall (63%-83%) in metabolism was due to the reduction in temperature. This suggests that the temperature-independent reduction of metabolism was already in place by autumn before the tegus had entered winter dormancy.

Integrating species life-history traits and patterns of deforestation in amphibian conservation planning

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Search for right-handed W bosons in top quark decay

We present a measurement of the fraction f(+) of right-handed W bosons produced in top quark decays, based on a candidate sample of t (t) over bar events in the lepton+jets decay mode. These data correspond to an integrated luminosity of 230 pb(-1), collected by the D0 detector at the Fermilab Tevatron p (p) over bar Collider at root s=1.96 TeV. We use a constrained fit to reconstruct the kinematics of the t (t) over bar and decay products, which allows for the measurement of the leptonic decay angle theta(*) for each event. By comparing the cos theta(*) distribution from the data with those for the expected background and signal for various values of f(+), we find f(+)=0.00 +/- 0.13(stat)+/- 0.07(syst). This measurement is consistent with the standard model prediction of f(+)=3.6 x 10(-4).

Search for production of single top quarks via tcg and tug flavor-changing-neutral-current couplings

We search for the production of single top quarks via flavor-changing-neutral-current couplings of a gluon to the top quark and a charm (c) or up (u) quark. We analyze 230 pb(-1) of lepton+jets data from p (p) over tilde collisions at a center of mass energy of 1.96 TeV collected by the D0 detector at the Fermilab Tevatron Collider. We observe no significant deviation from standard model predictions, and hence set upper limits on the anomalous coupling parameters kappa(c)(g)/Lambda and kappa(u)(g)/Lambda, where kappa(g) define the strength of tcg and tug couplings, and Lambda defines the scale of new physics. The limits at 95% C.L. are kappa(c)(g)/Lambda < 0.15 TeV-1 and kappa(u)(g)/Lambda < 0.037 TeV-1.