Identificação de duplicidades de acessos de feijão por meio de técnicas multivariadas

Este trabalho objetivou testar as técnicas de análise multivariada e da medida de divergência genética representada pela distância generalizada de Mahalanobis na seleção de descritores e na identificação de duplicidades de acessos de feijão (Phaseolus vulgaris L.). Cinqüenta acessos do Banco Ativo de Germoplasma (BAG-Feijão), da Embrapa - Centro Nacional de Pesquisa de Arroz e Feijão (CNPAF), foram avaliados em junho de 1993, utilizando-se delineamento experimental em blocos casualizados, com duas repetições. Dez descritores com características quantitativas e fenológicas foram analisados por meio de variáveis canônicas e distância de Mahalanobis. Todos os caracteres foram importantes na descrição do germoplasma. A técnica de agrupamento pela distância generalizada de Mahalanobis mostrou-se viável e eficaz na identificação de duplicidades do feijoeiro, podendo ser utilizada rotineiramente no Banco de Germoplasma.

Efectos de tipicidad en la percepción visual de escenas naturales

La actuación de las estructuras de conocimiento en el proceso de identificación y codificación de estimulos visuales se ha operativizado frecuentemente mediante conceptos como contexto o tipicidad. Ambos efectos pueden considerarse complementarios y producidos por la actuación de un mecanisrno de tipo atencional. Dicho mecanisrno fue aplicado al procesamiento de escenas por Arnau, Carreras y Salvador (en prensa). A partir de los términos propuestos en dicho modelo se intenta comprobar si la tipicidad es una variable relevante para la identificación de 10s objetos que forman una escena. Los resultados obtenidos en el experimento 1 permiten afirmar que el grado de tipicidad de un objeto respecto a una escena determina el tiempo y exactitud de su identificación. Por otra parte, en el experimento 2 se demuestra que en procesos de memoria a corto plazo el efecto de tipicidad detectado en el experimento 1 se anula. Finalmente se discuten las implicaciones de estos resultados para el estudio de la percepción visual de escenas naturales.

Comparing 'visual' effect size indices for single-case designs

Effect size indices are indispensable for carrying out meta-analyses and can also be seen as an alternative for making decisions about the effectiveness of a treatment in an individual applied study. The desirable features of the procedures for quantifying the magnitude of intervention effect include educational/clinical meaningfulness, calculus easiness, insensitivity to autocorrelation, low false alarm and low miss rates. Three effect size indices related to visual analysis are compared according to the aforementioned criteria. The comparison is made by means of data sets with known parameters: degree of serial dependence, presence or absence of general trend, changes in level and/or in slope. The percent of nonoverlapping data showed the highest discrimination between data sets with and without intervention effect. In cases when autocorrelation or trend is present, the percentage of data points exceeding the median may be a better option to quantify the effectiveness of a psychological treatment.

Factors affecting visual analysis in single-case designs

Visual inspection remains the most frequently applied method for detecting treatment effects in single-case designs. The advantages and limitations of visual inference are here discussed in relation to other procedures for assessing intervention effectiveness. The first part of the paper reviews previous research on visual analysis, paying special attention to the validation of visual analysts" decisions, inter-judge agreement, and false alarm and omission rates. The most relevant factors affecting visual inspection (i.e., effect size, autocorrelation, data variability, and analysts" expertise) are highlighted and incorporated into an empirical simulation study with the aim of providing further evidence about the reliability of visual analysis. Our results concur with previous studies that have reported the relationship between serial dependence and increased Type I rates. Participants with greater experience appeared to be more conservative and used more consistent criteria when assessing graphed data. Nonetheless, the decisions made by both professionals and students did not match sufficiently the simulated data features, and we also found low intra-judge agreement, thus suggesting that visual inspection should be complemented by other methods when assessing treatment effectiveness.

Contributions of pitch and bandwidth to sound-induced enhancement of visual cortex excitability in humans.

Multisensory interactions have been documented within low-level, even primary, cortices and at early post-stimulus latencies. These effects are in turn linked to behavioral and perceptual modulations. In humans, visual cortex excitability, as measured by transcranial magnetic stimulation (TMS) induced phosphenes, can be reliably enhanced by the co-presentation of sounds. This enhancement occurs at pre-perceptual stages and is selective for different types of complex sounds. However, the source(s) of auditory inputs effectuating these excitability changes in primary visual cortex remain disputed. The present study sought to determine if direct connections between low-level auditory cortices and primary visual cortex are mediating these kinds of effects by varying the pitch and bandwidth of the sounds co-presented with single-pulse TMS over the occipital pole. Our results from 10 healthy young adults indicate that both the central frequency and bandwidth of a sound independently affect the excitability of visual cortex during processing stages as early as 30 msec post-sound onset. Such findings are consistent with direct connections mediating early-latency, low-level multisensory interactions within visual cortices.

Aplicação de análise estatística para identificação de tendências climáticas

O objetivo deste trabalho foi usar a análise estatística para identificar tendências anuais da temperatura e precipitação pluvial. Foi usada a série histórica de 1924 a 1998 de precipitação pluvial e temperatura média do ar à superfície, da estação meteorológica de Urussanga (latitude 28º31' S, longitude 49º19' W e altitude de 48,2 m). Foram empregados a análise de regressão e os testes paramétricos de Run, Mann-Kendall e Pettitt. Os resultados indicam que houve tendência significativa no aumento da temperatura média anual e na temperatura média do mês de janeiro, sendo que a mudança ocorreu no ano de 1965. Não foi identificada nenhuma tendência significativa na temperatura média do mês de julho. Também foi identificada a tendência significativa de aumento da precipitação pluvial total anual, e da precipitação pluvial total no quarto trimestre. Nos três primeiros trimestres do ano, nenhuma tendência significativa foi identificada.

Auditory cues support place navigation in rats when associated with a visual cue.

Rats, like other crepuscular animals, have excellent auditory capacities and they discriminate well between different sounds [Heffner HE, Heffner RS, Hearing in two cricetid rodents: wood rats (Neotoma floridana) and grasshopper mouse (Onychomys leucogaster). J Comp Psychol 1985;99(3):275-88]. However, most experimental literature concerning spatial orientation almost exclusively emphasizes the use of visual landmarks [Cressant A, Muller RU, Poucet B. Failure of centrally placed objects to control the firing fields of hippocampal place cells. J Neurosci 1997;17(7):2531-42; and Goodridge JP, Taube JS. Preferential use of the landmark navigational system by head direction cells in rats. Behav Neurosci 1995;109(1):49-61]. To address the important issue of whether rats are able to achieve a place navigation task relative to auditory beacons, we designed a place learning task in the water maze. We controlled cue availability by conducting the experiment in total darkness. Three auditory cues did not allow place navigation whereas three visual cues in the same positions did support place navigation. One auditory beacon directly associated with the goal location did not support taxon navigation (a beacon strategy allowing the animal to find the goal just by swimming toward the cue). Replacing the auditory beacons by one single visual beacon did support taxon navigation. A multimodal configuration of two auditory cues and one visual cue allowed correct place navigation. The deletion of the two auditory or of the one visual cue did disrupt the spatial performance. Thus rats can combine information from different sensory modalities to achieve a place navigation task. In particular, auditory cues support place navigation when associated with a visual one.

Identificação de impurezas e misturas em pó de café por meio de comportamento espectral e análise de imagens digitais

Para eliminar divergências na interpretação dos resultados e agilizar os atuais métodos de detecção de fraudes em café torrado e moído, foi estabelecido um método baseado na análise por imagem e fundamentado no princípio de que diferentes materiais de origem orgânica, como o pó de café, podem apresentar reflectâncias distintas em diferentes comprimentos de onda do espectro eletromagnético. Partiu-se da hipótese de que o pó de café adulterado, quando submetido a uma fonte artificial de iluminação, apresenta uma reflectância, nos canais vermelho (R), verde (G) e azul (B), diferente em relação à do pó de café não-adulterado. Após as etapas de limpeza, secagem e homogeneização, foram geradas imagens multiespectrais das amostras de café, por meio de uma lupa acoplada a uma câmara CCD (Charge Coupled Device). A quantificação das impurezas na amostra foi obtida utilizando-se curvas de calibração entre a área relativa obtida pela classificação supervisionada de imagens e a porcentagem de impurezas presentes nas amostras. Esse novo método permite agilidade da resposta, ausência de subjetividade nos resultados e não-destruição das amostras analisadas, e assegura um patamar mínimo de detecção de 95% das impurezas do produto.

Identificação e quantificação de fungos micorrízicos arbusculares autóctones em municípios produtores de citros no Rio Grande do Sul

O objetivo deste trabalho foi identificar e quantificar os esporos de FMA presentes em viveiros e pomares de citros no Rio Grande do Sul. Foram coletadas amostras de solo e de raízes de dez viveiros e doze pomares de oito municípios produtores de citros, nas quais avaliaramse conteúdo nutricional, número de esporos por 100 g de solo seco e colonização das radicelas, e determinaramse as espécies autóctones. As espécies, em ordem decrescente de ocorrência, foram: Glomus macrocarpum > Scutellospora heterogama > Acaulospora scrobiculata = Acaulospora birreticulata > Glomus invermaium = Glomus occultum = Entrophospora colombiana > Glomus claroideum = Glomus constrictum > Scutellospora persica.

Subretinal neovascular membranes complicating uveitis : frequency, treatments and visual outcome

RESUME Les membranes néovasculaires (MNV) compliquent diverses pathologies ophtalmiques. Elles sont à l'origine d'une importante baisse de l'acuité visuelle lorsque elles se situent à proximité de la fovéa. A l'heure actuelle, peu de données relatives à leur association aux pathologies inflammatoires de l'oeil (uvéites) existent. Dans ce travail, la fréquence de MNV a été évaluée parmi 643 patients avec uvéite. Leur impact sur l'acuité visuelle ainsi que le pronostic en fonction des différents traitements effectués ont été étudiés. Les dossiers des 643 patients souffrant d'uvéite ont été étudiés. Les patients présentant une MNV ont été classés en trois groupes en fonction de l'importance de l'inflammation intraoculaire: élevée (2+ cellules dans le vitré), moyenne (1/2+ à 1+ cellules dans le vitré) ou absente (0 cellules dans le vitré). L'évolution de l'acuité visuelle fut considérée comme favorable (+VA: maintient de l'acuité visuelle ou gain d'une ou plusieurs lignes de Snellen) ou défavorable (-VA: perte d'une ou plusieurs lignes Snellen). Chez 9 patients, le traitement instauré a consisté, initialement, en l'administration orale de corticostéroïdes (CST) à haute dose qui, dans le cas d'évolution favorable (-FVA ou régression angiographique de la MNV), était arrêtée en doses dégressives. Dans les évolutions défavorables (-VA ou progression angiographique de la MNV), les CST étaient maintenus à dose moyenne en complémentation d'un traitement par thérapie laser (photothérapie dynamique (PDT), thermothérapie transpupillaire (TTT) ou laser Argon). Ce protocole thérapeutique ne fut appliqué chez trois patients en raison de la non disponibilité de PDT ou d'un diagnostic manqué d'uvéite. Douze patients sur 643 avec uvéite ont présenté une MNV. L'impact visuel moyen était de 4.5 lignes de Snellen et le temps moyen de suivi était de 19.5 mois. Deux patients avec inflammation intraoculaire élevée ont évolué favorablement sous CST seuls. Huit patients avec inflammation intraoculaire moyenne ont évolué favorablement sous CST seuls chez trois patients, alors que quatre patients ont nécessité une thérapie laser additionnelle. Le dernier patient ne fut traité que par thérapie laser sans CST (diagnostic manqué d'uvéite). Deux patients sans inflammation intraoculaire ont eu un pronostic défavorable sous CST seuls (pas d'autre alternative thérapeutique). Notre étude a démontré que les MNV sont une complication rare de l'uvéite qui, après traitement adéquat, ont un pronostic visuel relativement favorable. Bien que les CST semblent être la première modalité thérapeutique, les traitements laser devraient être adoptés tôt dans les situations d'inflammation intraoculaire moyenne ou absente.

Exploring the rate-limiting steps in visual phototransduction recovery by bottom-up kinetic modeling

Phototransduction in vertebrate photoreceptor cells represents a paradigm of signaling pathways mediated by G-protein-coupled receptors (GPCRs), which share common modules linking the initiation of the cascade to the final response of the cell. In this work, we focused on the recovery phase of the visual photoresponse, which is comprised of several interacting mechanisms. We employed current biochemical knowledge to investigate the response mechanisms of a comprehensive model of the visual phototransduction pathway. In particular, we have improved the model by implementing a more detailed representation of the recoverin (Rec)-mediated calcium feedback on rhodopsin kinase and including a dynamic arrestin (Arr) oligomerization mechanism. The model was successfully employed to investigate the rate limiting steps in the recovery of the rod photoreceptor cell after illumination. Simulation of experimental conditions in which the expression levels of rhodospin kinase (RK), of the regulator of the G-protein signaling (RGS), of Arr and of Rec were altered individually or in combination revealed severe kinetic constraints to the dynamics of the overall network. Our simulations confirm that RGS-mediated effector shutdown is the rate-limiting step in the recovery of the photoreceptor and show that the dynamic formation and dissociation of Arr homodimers and homotetramers at different light intensities significantly affect the timing of rhodopsin shutdown. The transition of Arr from its oligomeric storage forms to its monomeric form serves to temper its availability in the functional state. Our results may explain the puzzling evidence that overexpressing RK does not influence the saturation time of rod cells at bright light stimuli. The approach presented here could be extended to the study of other GPCR signaling pathways.