Optical properties of irregular interstellar grains

In order to study the interaction of light with interstellar grains, the authors represent an irregular particle by a network of interacting dipoles whose polarizability is determined in a first approach by the Clausius-Mossoti relationship. Typically, 10,000 dipoles are considered. In the case of spherical particles, the results from Mie theory are fully recovered. The main interest of this method is to study with good accuracy the implications of surface roughness and/or inhomogeneities on optical properties in the infrared spectral range, particularly of the silicate emission features

Light scattering of large rough particles application to cometary grains

While the electromagnetic field scattered by a spherical particle is classically obtained by the Helmholtz equation, the general case of an arbitrary particle may be investigated in the general framework of the interaction of a wave with a scattering potential. A wave function then satisfies the Schroedinger equation. The general solution of the Schroedinger equation is given. The main disadvantage of this approach are its restriction to large particles and its scalar nature preventing the calculation of the polarization. However, Perrin and Lamy have shown how to avoid the second limitation and retrieve a vectorial description. They proved that in the case of large spheres when the ad hoc assumptions are satisfied, the expression of the scattering amplitude may be approximated by an expansion series in partial waves, i.e., on a discrete basis. The analogy may be generalized, and the ratio of the two components for a rough particle obtained by taking the ratio of the reflectivities for the two directions of polarization. These reflectivities involve the simple and double reflections calculated following the method developed by Wolff for rough surfaces. The theory is further detailed

An experimental determination of perceived liveability in Sydney

Liveability is a concept and factor being used by urban planners and designers to better understand how people perceive the places they live and work in and how it affects their life choices. Existing normative liveability indices are based on measurable and reproducible factors. They aim to objectively compare various residential conditions and their evolution. However, better understanding decisional processes attached to transport or residential choices necessitates a more dynamic approach. The concept of perceived liveability addresses the subjective nature of individual assessments of local environmental conditions. First, we have developed an empirical model based on subjective ranking and evaluation of six environmental factors. Then, we have conducted a pilot Computer Assisted Telephone Interviewing (CATI) survey in Sydney to inform our empirical model. Finally, a linear additive model was fitted to the survey data in order to represent various levels of satisfaction based on residential and socio-demographic conditions. (Résumé d'auteur

Writing Reusable Digital Geometry Algorithms in a Generic Image Processing Framework

Digital Geometry software should reflect the generality of the underlying mathe- matics: mapping the latter to the former requires genericity. By designing generic solutions, one can effectively reuse digital geometry data structures and algorithms. We propose an image processing framework focused on the Generic Programming paradigm in which an algorithm on the paper can be turned into a single code, written once and usable with various input types. This approach enables users to design and implement new methods at a lower cost, try cross-domain experiments and help generalize resultsComment: Workshop on Applications of Discrete Geometry and Mathematical Morphology, Istanb : France (2010

Radio emission from satellite-Jupiter interactions (especially Ganymede)

Analyzing a database of 26 years of observations of Jupiter from the Nan\c{c}ay Decameter Array, we study the occurrence of Io-independent emissions as a function of the orbital phase of the other Galilean satellites and Amalthea. We identify unambiguously the emissions induced by Ganymede and characterize their intervals of occurrence in CML and Ganymede phase and longitude. We also find hints of emissions induced by Europa and, surprisingly, by Amalthea. The signature of Callisto-induced emissions is more tenuous.Comment: 14 pages, 7 figures, in "Planetary Radio Emissions VIII", G. Fischer, G. Mann, M. Panchenko and P. Zarka eds., Austrian Acad. Sci. Press, Vienna, in press, 201

The effect of load in a contact with boundary lubrication

The effect of the transition load on the wear in a contact with boundary lubrication was investigated. An experimental method was developed for this purpose, and parameters affecting the boundary lubrication under industrial operating conditions were identified. These parameters are the adsorbed boundary film, the contact microgeometry (surface roughness), macrogeometry, and hardness of materials used. It was found that the curve of the tops of the surface protrustion affect the transition load, and thus the boundary lubrication. The transition load also depends on the chemical nature of the contact and its geometrical and mechanical aspects

Differences in salivary α-amylase levels among women with different taste sensitivities

Saliva is the main component of taste receptor cells external environment, and consequently it may have a decisive role in taste perception. Taste sensitivity varies among different individuals. Sensitivity to the compound n-6-propylthiouracil (PROP) has been considerably studied and besides the known influence of genetic background, the contribution of perireceptor environment is not completely clear yet. Salivary α-amylase (one of the main proteins of saliva) is involved in carbohydrate digestion and its enzymatic activity may change the levels of sugars present in the mouth, influencing food perception. To evaluate differences in salivary total protein content and α-amylase activity and expression among individuals with different PROP taste sensitivities. Sixty seven female women (18-30 years old) were classified in one of the three groups of taste sensitivity (non-taster, medium-taster or super-taster), according to the perceived intensity for PROP, using Labeled Magnitude Scales. Saliva was collected without stimulation. Flow rate was calculated by dividing total volume for the 5 minutes collection. Bradford method was used for total protein assessment. Dinitrosalicylic acid assay was used for measuring the starch-hydrolyzing activity of salivary α-amylase, while the expression of this enzyme was evaluated by Wester blot. 20,9% of the subjects were classified as non-taters. The three groups presented similar saliva flow rates and total protein content was not significantly different although a tendency for lower protein concentration in medium-tasters individuals was observed. Salivary α-amylase activity (U/min) was higher in supertasters (P<0,05). Salivary α-amylase activity (U/min) was higher in super-tasters (P<0,05) without any significant differences in expression. In women individual differences in saliva composition can contribute to the different taste sensitivity. One of the differences appears to be α-amylase enzymatic activity. The reason for this deserves to be elucidated, as well as the potential involvement of others salivary proteins

Multi-point observations of intermittency in the cusp regions

International audienceIn this paper we investigate the statistical properties of magnetic field fluctuations measured by the four Cluster spacecraft in the cusp and close to the interface with the magnetospheric lobes, magnetopause and magnetosheath. At lower altitudes along the outbound orbit of 26 February 2001, the magnetic field fluctuations recorded by all four spacecraft are random and their Probability Distribution Functions (PDFs) are Gaussian at all scales. The flatness parameter, F ? related to the kurtosis of the time series, is equal to 3. At higher altitudes, in the cusp and its vicinity, closer to the interface with the magnetopause and magnetosheath, the PDFs from all Cluster satellites are non-Gaussian and show a clear intermittent behavior at scales smaller than ?G? 61 s (or 170 km). The flatness parameter increases to values greater than 3 for scales smaller than ?G. A Haar wavelet transform enables the identification of the "events" that produce sudden variations of the magnetic field and of the scales that have most of the power. The LIM parameter (i.e. normalized wavelet power) indicates that events for scales below 65 s are non-uniformly distributed throughout the cusp passage. PDFs, flatness and wavelet analysis show that at coarse-grained scales larger than ?G the intermittency is absent in the cusp. Fluctuations of the magnetic energy observed during the same orbit in the magnetosheath show PDFs that tend toward a Gaussian at scales smaller than ?G found in the cusp. The flatness analysis confirms the decreasing of ?G from cusp to magnetosheath. Our analysis reveals the turbulent cusp as a transition region from a non-intermittent turbulent state inside the magnetosphere to an intermittent turbulent state in the magnetosheath that has statistical properties resembling the solar wind turbulence. The observed turbulent fluctuations in the cusp suggests a phenomenon of nonlinear interactions of plasma coherent structures as in contemporary models of space plasma turbulence

Alterações na actividade enzimática da amílase salivar em indivíduos obesos

Nos últimos anos o estudo da composição proteica da saliva ganhou interesse pelo seu potencial no diagnóstico não invasivo e compreensão de diversas doenças, quer orais, quer sistémicas. Para além disso, a interacção deste fluido com os constituintes dos alimentos tornam a sua análise importante para a compreensão das variações a nível da percepção dos alimentos e escolhas alimentares. Há, contudo, poucos estudos que comparem a composição proteica da saliva de indivíduos obesos com indivíduos normoponderais. Uma das proteínas mais abundante na saliva é a α-amilase. Esta proteína é responsável pelo início da digestão de hidratos de carbono na boca influenciando a percepção dos alimentos. Para além disso, os seus níveis são indicadores do funcionamento das glândulas salivares, tendo ainda sido sugerida como potencial marcador de condições de stress e de actividade do sistema nervoso simpático. O presente trabalho teve como objectivo comparar os níveis de α-amilase salivar entre indivíduos obesos (IMC>30; N=10) e normoponderais (IMC<25; N=10) do sexo feminino. Foram feitas recolhas de saliva mista, na ausência de estimulação e sempre à mesma hora do dia. Para determinar a actividade enzimática da α-amilase utilizou-se um kit colorimétrico (Sentinel Diagnostics). Foi observada uma maior actividade enzimática de α-amilase nos indivíduos obesos comparativamente aos normoponderais (243,2 X 103 ± 37,7 X 103 e 106,1 X 103 ± 44,2 X 103 U/L, respectivamente) A maior actividade enzimática da α-amilase poderá contribuir para alterações na percepção dos alimentos, nomeadamente no que diz respeito ao gosto doce dos hidratos de carbono. Uma diferente sensibilidade gustativa poderá ter influências nas escolhas alimentares. Estes resultados reforçam a importância de estudos mais aprofundados acerca da função salivar e percepção gustativa na obesidade