Reação de cultivares de feijoeiro comum à mancha angular em casa de vegetação

Foi avaliada a reação de 23 genótipos de feijoeiro comum (Phaseolus vulgaris) à mancha angular causada por Phaeoisariopsis griseola, utilizando os isolados monospóricos Ig 664 e Ig 669, caracterizados como os patótipos 63.23 e 63.19, respectivamente. Quatorze dias após a semeadura (estádio V3), as plantas foram inoculadas com uma suspensão contendo 2,5 x 10(4) conídios/mL, nas faces adaxial e abaxial da primeira folha trifoliolada. A avaliação dos sintomas foi efetuada aos 14 e 18 dias após a inoculação, utilizando-se uma escala variando de 1 (sem sintomas) a 9 ( > 25% da área foliar com lesões de mancha angular). Das cultivares analisadas, BRS Valente, CNFC 10281, CNFP 10138, BRS Grafite, BRS Requinte, BRS Pontal, MAR 02, Cornell 49-242 e AND 277 foram resistentes aos dois isolados. As cultivares Carioca Rubi, CNFC 9504, CNFC 10150 e Soberano foram suscetíveis aos dois patótipos testados. O patótipo 63.23 foi o mais virulento. As novas fontes de resistência à mancha angular identificadas neste trabalho podem ser utilizadas em programas de melhoramento do feijoeiro comum, que visem incorporar resistência em novas cultivares.

Indução de resistência em feijoeiro a mancha angular por extratos de micélio de Pycnoporus sanguineus

O feijoeiro (Phaseolus vulgaris L.) está entre as principais culturas da agricultura nacional e pode ser afetada por várias doenças, como a mancha angular causada por Pseudocercospora griseola. Com o objetivo de desenvolver métodos alternativos ao químico para o controle desta doença, verificou-se o potencial de extratos de micélio de Pycnoporus sanguineus para atividade antimicrobiana in vitro contra P. griseola e para indução de resistência e ativação de enzimas de defesa em feijoeiro, como peroxidase, polifenoloxidase e β-1,3-glucanase, além de sua influência nos teores de proteínas e clorofilas. Os experimentos in vitro e em casa de vegetação foram constituídos pelos extratos de micélio de P. sanguineus e dos controles água, acibenzolar-S-metil (ASM: 75 mg i.a./L) e fungicida azoxystrobin (40 mg i.a./L). In vitro o extrato de micélio apresentou efeito sobre o crescimento micelial, a esporulação e a germinação de esporos de P. griseola. In vivo a severidade foi reduzida em 93% e 50% em casa de vegetação e a campo respectivamente, em relação ao controle água. A atividade das enzimas peroxidase e polifenoloxidase e os teores de proteínas e clorofilas foram maiores nas plantas tratadas com o extrato. Estes resultados indicam a eficiência de P. sanguineus para o controle alternativo da mancha angular do feijoeiro.

Weather based warning systems for bean angular-leaf-spot and anthracnose

Data available in the literature were used to develop a warning system for bean angular leaf spot and anthracnose, caused by Phaeoisariopsis griseola and Colletotrichum lindemuthianum, respectively. The model is based on favorable environmental conditions for the infectious process such as continuous leaf wetness duration and mean air temperature during this subphase of the pathogen-host relationship cycle. Equations published by DALLA PRIA (1977) showing the interactions of those two factors on the disease severity were used. Excell spreadsheet was used to calculate the leaf wetness period needed to cause different infection probabilities at different temperature ranges. These data were employed to elaborate critical period tables used to program a computerized electronic device that records leaf wetness duration and mean temperature and automatically shows the daily disease severity value (DDSV) for each disease. The model should be validated in field experiments under natural infection for which the daily disease severity sum (DDSS) should be identified as a criterion to indicate the beginning and the interval of fungicide applications to control both diseases.

Dependência de micorrizas para a nodulação de leguminosas arbóreas tropicais

As espécies de leguminosas Piptadenia gonoacantha e Piptadenia paniculata apresentam dificuldade para nodular e crescer em substratos esterilizados, o que dificulta a seleção de estirpes de rizóbio eficientes dessas espécies. As plantas que apresentam nódulos no campo estão micorrizadas. Assim, a boa resposta das plantas no campo pode ser devida à presença de FMAs. O objetivo deste trabalho foi estudar o efeito da micorrização sobre a nodulação e crescimento de plantas de P. gonoacantha e P. paniculata. Os experimentos foram realizados em casa de vegetação, na Embrapa Agrobiologia, Rio de Janeiro. As plantas foram inoculadas com estirpes de rizóbio específicas de cada espécie e com os fungos Gigaspora margarita e Glomus clarum. Ambas as espécies vegetais demonstraram-se altamente responsivas à inoculação com FMAs. Plantas que receberam rizóbios e fungos micorrízicos apresentaram-se noduladas, com maior produção de matéria seca. Já as plantas inoculadas apenas com rizóbio não exibiram nódulos e tiveram menor acúmulo de matéria seca. As plantas de P. gonoacantha apresentaram maior conteúdo de P na parte aérea quando inoculadas com FMAs. Esses resultados indicam que a micorrização é necessária para a nodulação e crescimento satisfatórios das espécies estudadas, e sugere-se a inoculação com FMAs para a seleção de estirpes eficientes de rizóbio em leguminosas com dificuldade de crescimento no sistema convencional de seleção de estirpes.

Aplicação de métodos geoestatísticos para identificação de dependência espacial na análise de dados de um ensaio de espaçamento florestal em delineamento sistemático tipo leque

Os delineamentos sistemáticos se destacam pela sua compacidade e abrangência e por permitir testar maior número de espaçamentos possíveis. No entanto, não é utilizado devido ao arranjo sistemático (não casualizado) das plantas e à alta sensibilidade para valores perdidos. O objetivo deste trabalho foi descrever o modelo geoestatístico e métodos associados de inferência no contexto de análise de experimentos não aleatorizados, reportando resultados aplicados para identificar a dependência espacial em um particular experimento em delineamento sistemático tipo leque de Eucalyptus dunnii. Também foram propostas, analisadas e comparadas diferentes alternativas para tratar dados faltantes que pudessem advir de falhas e, ou, mortalidade de plantas. Os dados foram analisados seguindo-se três modelos que diferiram, com co-variáveis, na forma de tratar os dados faltantes. Para cada um destes foi construído um semivariograma, com o ajuste de três modelos de função de correlação, sendo os parâmetros estimados pelo método de máxima verossimilhança e selecionados pelo critério de Akaike. Esses modelos, com e sem o componente espacial, foram comparados pelo teste da razão de verossimilhança. De acordo com os resultados, verificou-se que: (1) as co-variáveis interagiram positivamente com a variável de resposta, evitando que dados coletados sejam desperdiçados; (2) a comparação dos modelos, com e sem o componente espacial, não confirmou a existência de dependência; (3) a incorporação da estrutura de dependência espacial aos modelos observacionais recuperou a capacidade de fazer inferências válidas na ausência de aleatorização, permitindo contornar problemas operacionais e, assim, garantindo que os dados possam ser submetidos a uma análise clássica.

Queilite angular traumática em eqüinos associada à ingestão de Panicum maximum

Uma condição com aumento da fenda bucal de eqüinos por lesão na comissura labial foi estudada. Este aumento tinha extensão variável e era uni ou bilateral. Na mucosa da bochecha da comissura labial exposta havia pequenas erosões. Durante a mastigação havia perda de pequena quantidade de capim e saliva pela fenda bucal aumentada. Os animais apresentavam bom estado nutricional. O exame histopatológico de tecido retirado da comissura labial revelou epidermite superficial. Nas quatro propriedades onde se verificou o problema, constatou-se que os eqüinos eram mantidos em sistema extensivo de criação em pastagem de Panicum maximum (variedades Tanzânia, Mombaça, Tobiatã e Colonião), com folhas maduras, altas, lignificadas e de bordos cortantes. De acordo com os dados epidemiológicos, com os achados clínicos e histopatológicos, concluí-se que essas lesões foram causadas pela ação cortante das folhas de Panicum maximum, associada à forma de apreensão da pastagem alta e mastigação pelos eqüinos.

Contrast sensitivity to angular frequency stimuli is higher than that for sinewave gratings in the respective middle range

This study compares contrast thresholds for sinewave gratings, or spatial frequencies (1/CSF) with contrast thresholds for angular frequencies (1/aCSF) and for radial frequencies, or J0 targets (1/rCSF). Observers had to differentiate between one of these frequency stimuli and a stimulus at mean luminance within a forced-choice procedure. All measurements were made with the same equipment, methods and subjects. Our results show higher sensitivity to, or lower thresholds for, angular frequencies when compared to either sinewave gratings or J0 targets. Contrast values in arbitrary units, in the lower threshold range for angular frequencies, were about half those required to differentiate sinewave gratings from mean luminance in its most sensitive range

Inhibitory effects in the detection of 1 cpd jo targets superimposed to angular frequency stimuli or sinewave gratings

Independence among channels processing different aspects of spatial information, including orthogonal stimuli, has been generally assumed in the literature. We tested independence between the processing of jo targets and the processing of either vertical sinusoidal gratings or angular frequency stimuli with suprathreshold summation. We found the detection of a jo target at 1 cpd to be affected in an inhibitory fashion by either background angular frequencies in the range of 3-96 cycles or sinewave gratings in the range of 0.8-3.0 cpd. These results demonstrate interactions both among orthogonal stimuli and among channels processing vertical sinewave gratings and jo target stimuli. Our discussion focuses on the hypothesis of frequency decomposition in polar coordinates

Narrow-band 1, 2, 3, 4, 8, 16 and 24 cycles/360º angular frequency filters

We measured human frequency response functions for seven angular frequency filters whose test frequencies were centered at 1, 2, 3, 4, 8, 16 or 24 cycles/360º using a supra-threshold summation method. The seven functions of 17 experimental conditions each were measured nine times for five observers. For the arbitrarily selected filter phases, the maximum summation effect occurred at test frequency for filters at 1, 2, 3, 4 and 8 cycles/360º. For both 16 and 24 cycles/360º test frequencies, maximum summation occurred at the lower harmonics. These results allow us to conclude that there are narrow-band angular frequency filters operating somehow in the human visual system either through summation or inhibition of specific frequency ranges. Furthermore, as a general result, it appears that addition of higher angular frequencies to lower ones disturbs low angular frequency perception (i.e., 1, 2, 3 and 4 cycles/360º), whereas addition of lower harmonics to higher ones seems to improve detection of high angular frequency harmonics (i.e., 8, 16 and 24 cycles/360º). Finally, we discuss the possible involvement of coupled radial and angular frequency filters in face perception using an example where narrow-band low angular frequency filters could have a major role.

Contrast sensitivity to angular frequency gratings is not higher than to Cartesian gratings

When contrast sensitivity functions to Cartesian and angular gratings were compared in previous studies the peak sensitivity to angular stimuli was reported to be 0.21 log units higher. In experiments carried out to repeat this result, we used the same two-alternative forced-choice paradigm, but improved experimental control and precision by increasing contrast resolution from 8 to 12 bits, increasing the screen refresh rate from 30 Hz interlaced to 85 Hz non-interlaced, linearizing the voltage-luminance relation, modulating luminance in frequencies that minimize pixel aliasing, and improving control of the subject's exposure to the stimuli. The contrast sensitivity functions to Cartesian and angular gratings were similar in form and peak sensitivity (2.4 cycles per visual degree (c/deg) and 32 c/360º, respectively) to those reported in a previous study (3 c/deg and 32 c/360º, respectively), but peak sensitivity to angular stimuli was 0.13 log units lower than that to Cartesian stimuli. When the experiment was repeated, this time simulating the experimental control level used in the previous study, no difference between the peak sensitivity to Cartesian and angular stimuli was found. This result agrees with most current models that assume Cartesian filtering at the first visual processing stage. The discrepancy in the results is explained in part by differences in the degree of experimental control.

Comparison of angular frequency contrast sensitivity in young and older adults

The aim of the present study was to measure contrast sensitivity curves for angular frequencies in the range between 2 and 96 cycles/360º in older human adult volunteers and to compare these measurements with the more usual contrast sensitivity functions for sine-wave gratings. All subjects were free of identifiable ocular disease and had normal acuity. We measured the contrast thresholds for young adults (N = 6; age range, 20-26 years) and older adults (N = 6; age range, 60-67 years) using the psychophysical forced-choice method. In this paradigm the volunteers had to choose the stimulus containing a test frequency at low contrast (e.g., either a sine-wave grating or an angular frequency stimulus), or another neutral stimulus at mean luminance (without any contrast). Older adults presented a loss in contrast sensitivity at high and medium angular frequencies compared to the young adults (i.e., from 8 to 96 cycles/360º). Contrary to expectation, contrast sensitivity at low angular frequencies, i.e., 2 and 4 cycles/360º, was better for the older group than for the younger group. On the other hand, contrast sensitivity for sine-wave gratings at 3 and 4 cpd was higher for young adults as expected. These results suggest age-related changes in the contrast sensitivity function for angular frequencies.

La piedra angular : novela

UANL

Annealing inducedlowcoercivity,nanocrystallineCo–Fe–Si thin films exhibitinginversecosine angular variation

Co–Fe–Si based films exhibit high magnetic moments and are highly sought after for applications like soft under layer sinper pendicular recording mediatomagneto-electro-mechanical sensor applications.In this workt he effect of annealing on s tructural,morphologicaland magnetic propertiesofco–Fe–Si thin films wasinvestigated.compositional analysis using x-rayphotoelectron spectroscopy and secondary ion massspectroscopyrevealedanativeoxidesurfacelayerconsistingofoxidesofco,feandsionthe surface. The morphology of theas deposited films shows mound like structures conformingtothe Volmer–Webergrowthmodel.Nanocrystallisationofamorphous films upon annealing was observed by glancing anglex-raydiffraction and transmission electron microscopy.Theevolutionofmagnetic properties with annealing is explained using the Herzermodel.Vibrating sample magnetometry measurements carried out at various angles from01 to 901 to the applied magnetic field were employed to study the angula rvariation of coercivity.The angular variation fits the modified Kondorsky model. Interestingly,the coercivity evolution with annealing deduced frommagneto-opticalKerreffectstudies indicates areversetrendcomparedtomagetisationobservedinthebulk.Thiscanbeattributedtoa domain wallpinningatnativeoxidelayeronthesurfaceofthin films. Theevolutionofsurfacemagnetic properties iscorrelatedwithmorphologyevolutionprobedusingatomicforcemicroscopy.The morphology aswellasthepresenceofthenativeoxidelayerdictatesthesurfacemagneticproperties and this is corroborated by the apparent difference in the bulk and surface magnetic properties

Many-body theory of laser-induced ultrafast demagnetization and angular momentum transfer in ferromagnetic transition metals

An electronic theory is developed, which describes the ultrafast demagnetization in itinerant ferromagnets following the absorption of a femtosecond laser pulse. The present work intends to elucidate the microscopic physics of this ultrafast phenomenon by identifying its fundamental mechanisms. In particular, it aims to reveal the nature of the involved spin excitations and angular-momentum transfer between spin and lattice, which are still subjects of intensive debate. In the first preliminary part of the thesis the initial stage of the laser-induced demagnetization process is considered. In this stage the electronic system is highly excited by spin-conserving elementary excitations involved in the laser-pulse absorption, while the spin or magnon degrees of freedom remain very weakly excited. The role of electron-hole excitations on the stability of the magnetic order of one- and two-dimensional 3d transition metals (TMs) is investigated by using ab initio density-functional theory. The results show that the local magnetic moments are remarkably stable even at very high levels of local energy density and, therefore, indicate that these moments preserve their identity throughout the entire demagnetization process. In the second main part of the thesis a many-body theory is proposed, which takes into account these local magnetic moments and the local character of the involved spin excitations such as spin fluctuations from the very beginning. In this approach the relevant valence 3d and 4p electrons are described in terms of a multiband model Hamiltonian which includes Coulomb interactions, interatomic hybridizations, spin-orbit interactions, as well as the coupling to the time-dependent laser field on the same footing. An exact numerical time evolution is performed for small ferromagnetic TM clusters. The dynamical simulations show that after ultra-short laser pulse absorption the magnetization of these clusters decreases on a time scale of hundred femtoseconds. In particular, the results reproduce the experimentally observed laser-induced demagnetization in ferromagnets and demonstrate that this effect can be explained in terms of the following purely electronic non-adiabatic mechanism: First, on a time scale of 10–100 fs after laser excitation the spin-orbit coupling yields local angular-momentum transfer between the spins and the electron orbits, while subsequently the orbital angular momentum is very rapidly quenched in the lattice on the time scale of one femtosecond due to interatomic electron hoppings. In combination, these two processes result in a demagnetization within hundred or a few hundred femtoseconds after laser-pulse absorption.