Tomographic sensing of displacement fields

A wavelength scanning interferometry system is used to measure all the orthogonal components of the displacement field inside semitransparent scattering materials. A near infrared tunable laser illuminates a sample from multiple directions. The image of the sample is recombined with a reference beam on a photodetector array. As the laser frequency is linearly tuned during a scan, a sequence of speckle interferograms is recorded. In order to reconstruct the sample structure, Fourier transformation is performed on a pixel by pixel basis along the temporal axis of the 3-D data cube obtained. Multiple displacement sensitivities are achieved by introducing different optical delays between the reference and the illumination beams, which separate the reconstruction signals in the frequency domain. Phase changes due to mechanical loading of the sample can finally be measured and combined to obtain all orthogonal components of the displacement field in a convenient coordinate system. Controlled rigid body rotations of an epoxy phantom have been used to validate the methodology

Simultaneous measurement of in-plane and out-of-plane displacement fields in scattering media using phase-contrast spectral optical coherence tomography

The use of phase contrast spectral optical coherence tomography to measure two orthogonal displacement components on a slice within a scattering medium is demonstrated. This is achieved by combining sequential oblique illumination of the object and recording two interferograms before plus two after the deformation. The proposed technique is illustrated with results from a sample undergoing simple shear. Depth-resolved out-of-plane and in-plane sensitivities of 0.14 and 4.2 μm per fringe are demonstrated up to a depth of 400 μm in a water based polymer

Spatially resolved stress measurements in materials with polarization-sensitive optical coherence tomography: image acquisition and processing aspects

We demonstrate that polarization-sensitive optical coherence tomography (PS-OCT) is suitable to map the stress distribution within materials in a contactless and non-destructive way. In contrast to transmission photoelasticity measurements the samples do not have to be transparent but can be of scattering nature. Denoising and analysis of fringe patterns in single PS-OCT retardation images are demonstrated to deliver the basis for a quantitative whole-field evaluation of the internal stress state of samples under investigation.Comment: 10 pages, 6 figures; Copyright: Blackwell Publishing Ltd 2008; The definitive version is available at: www.blackwell-synergy.co

On the Complexity of Searching in Trees: Average-case Minimization

We focus on the average-case analysis: A function w : V -> Z+ is given which defines the likelihood for a node to be the one marked, and we want the strategy that minimizes the expected number of queries. Prior to this paper, very little was known about this natural question and the complexity of the problem had remained so far an open question. We close this question and prove that the above tree search problem is NP-complete even for the class of trees with diameter at most 4. This results in a complete characterization of the complexity of the problem with respect to the diameter size. In fact, for diameter not larger than 3 the problem can be shown to be polynomially solvable using a dynamic programming approach. In addition we prove that the problem is NP-complete even for the class of trees of maximum degree at most 16. To the best of our knowledge, the only known result in this direction is that the tree search problem is solvable in O(|V| log|V|) time for trees with degree at most 2 (paths). We match the above complexity results with a tight algorithmic analysis. We first show that a natural greedy algorithm attains a 2-approximation. Furthermore, for the bounded degree instances, we show that any optimal strategy (i.e., one that minimizes the expected number of queries) performs at most O(\Delta(T) (log |V| + log w(T))) queries in the worst case, where w(T) is the sum of the likelihoods of the nodes of T and \Delta(T) is the maximum degree of T. We combine this result with a non-trivial exponential time algorithm to provide an FPTAS for trees with bounded degree

Transcriptional profile of Pseudomonas syringae pv. phaseolicola NPS3121 in response to tissue extracts from a susceptible Phaseolus vulgaris L. cultivar

<p>Abstract</p> <p>Background</p> <p><it>Pseudomonas syringae </it>pv. phaseolicola is a Gram-negative plant-pathogenic bacterium that causes "halo blight" disease of beans (<it>Phaseolus vulgaris </it>L.). This disease affects both foliage and pods, and is a major problem in temperate areas of the world. Although several bacterial genes have been determined as participants in pathogenesis, the overall process still remains poorly understood, mainly because the identity and function of many of the genes are largely unknown. In this work, a genomic library of <it>P. syringae </it>pv. phaseolicola NPS3121 was constructed and PCR amplification of individual fragments was carried out in order to print a DNA microarray. This microarray was used to identify genes that are differentially expressed when bean leaf extracts, pod extracts or apoplastic fluid were added to the growth medium.</p> <p>Results</p> <p>Transcription profiles show that 224 genes were differentially expressed, the majority under the effect of bean leaf extract and apoplastic fluid. Some of the induced genes were previously known to be involved in the first stages of the bacterial-plant interaction and virulence. These include genes encoding type III secretion system proteins and genes involved in cell-wall degradation, phaseolotoxin synthesis and aerobic metabolism. On the other hand, most repressed genes were found to be involved in the uptake and metabolism of iron.</p> <p>Conclusion</p> <p>This study furthers the understanding of the mechanisms involved, responses and the metabolic adaptation that occurs during the interaction of <it>P. syringae </it>pv. phaseolicola with a susceptible host plant.</p

Conocimientos, actitudes y prácticas sobre dengue en estudiantes de educación primaria en Chorrillos, Lima, Perú

Objectives. To assess the knowledge, attitudes and practices on dengue fever, measures for prevention and control, and to identify factors related to unawareness in public elementary school students in the district of Chorrillos, Lima, Peru. Design. Cross sectional observational study. Setting. State elementary institution in Chorrillos district, Lima, Peru. Participants. Students of elementary school. Methods. In the year 2013, 142 students from fifth and sixth grade answered a survey questionnaire. We explored the perception among 12 school brigadiers using the projective technique. Main outcome measures. Knowledge, attitudes and practices about dengue. Results. In the study, 53.5% students were boys (76), mean age 11.2 ± 1.05 years old; 33.1% (47; CI95% 25.4-41.4) had basic knowledge about dengue; 53.5% (76) were able to identify dengue virus’ mechanism of vertical transmission; 29.6% of students (42; CI95% 22.2-37.8) were able to identify the larvae and 54.2% (77) identified the adult flying mosquito. Only 5.6% (8) and 2.1% (3) knew respectively of larvicides and using wet sand in flower vases as measures of control at home; 75.4% of the boys (75; CI95% 67.4-82.2) were willing to participate in active control of the mosquito vector, with statistical difference between boys and girls (p = 0.049238). Not having previous information led to not having basic knowledge about dengue (OR = 3.7; CI95% 1.7–8.3) (p = 0.0004676) Conclusion. The knowledge among students about clinical features, mode of transmission, vector and measures of prevention and control of the dengue virus were low because they had not received appropriate information.Revisión por pare

Sex, social interaction and food consumption: “The Eva effect” / Género, interacción social y consumo de alimento: “El efecto Eva”

Abstract. Several elements provide information for food consumption, among them: flavor, texture and temperature. These elements related to environmental characteristics and experience integrate the feeding behavior. Experimental evidence suggests that sex and social interaction are important factors for food consumption. This study evaluated effects of sex and social interaction on food consumption. Additionally, our proposal is to use Behavioral Catalogue of Feeding Interaction (BCFI).  Twenty-four human subjects, both sexes, between 20 and 28 years-old, which were not known between them, were exposed to different familiar and novel foods, evaluating the feeding interaction. Subjects were divided in three groups. First group was formed by man, second by woman; and third group by subjects of both sexes. Data suggest that group 1 and 2 registered similar food consumption in comparison with the group 3 that registered a little consumption. A strong influence of women was registered on men to stimulate its food consumption, phenomenon that was denominated “Eva Effect”. We conclude that sex is an important factor in the study of feeding phenomenon.   Key words: food consumption, sex, feeding interaction, Eva effect.   Resumen. Diversos elementos proporcionan la información necesaria para el consumo de alimentos, entre ellos: el sabor, la textura y temperatura.  Sin embargo, se requiere de su vinculación con la experiencia y las características ambientales para integrar el comportamiento alimentario. La evidencia experimental sugiere que el sexo y la interacción social son factores importantes para el consumo de alimentos. Esta investigación evaluó los efectos del género y de la interacción social sobre el consumo de alimentos. Adicionalmente, para tal objetivo se propone el uso del Catálogo Conductual de Interacción Alimentaria (CCIA). Participaron veinticuatro individuos de ambos sexos, entre 20 y 28 años, desconocidos entre ellos, fueron expuestos a diversos alimentos usuales y novedosos evaluando su interacción alimentaria. Los participantes fueron divididos en tres grupos. El grupo 1 fue integrado por hombres, el grupo 2 por mujeres y el grupo 3 por ambos géneros. Los resultados mostraron que el grupo 1 y 2 consumieron cantidades similares de alimento en comparación con el grupo 3 que presentó un escaso consumo. Se registró una fuerte influencia de las mujeres sobre los hombres para promover su consumo de alimento, fenómeno que fue denominado como “Efecto Eva”. Concluimos que el género es un importante factor en el estudio del fenómeno alimentario.   Palabras clave: consumo de alimento, género, interacción alimentaria, efecto Ev