995 resultados para Physical parameter


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Detailed information about the sediment properties and microstructure can be provided through the analysis of digital ultrasonic P wave seismograms recorded automatically during full waveform core logging. The physical parameter which predominantly affects the elastic wave propagation in water-saturated sediments is the P wave attenuation coefficient. The related sedimentological parameter is the grain size distribution. A set of high-resolution ultrasonic transmission seismograms (ca. 50-500 kHz), which indicate downcore variations in the grain size by their signal shape and frequency content, are presented. Layers of coarse-grained foraminiferal ooze can be identified by highly attenuated P waves, whereas almost unattenuated waves are recorded in fine-grained areas of nannofossil ooze. Color-encoded pixel graphics of the seismograms and instantaneous frequencies present full waveform images of the lithology and attenuation. A modified spectral difference method is introduced to determine the attenuation coefficient and its power law a = kfn. Applied to synthetic seismograms derived using a "constant Q" model, even low attenuation coefficients can be quantified. A downcore analysis gives an attenuation log which ranges from ca. 700 dB/m at 400 kHz and a power of n = 1-2 in coarse-grained sands to few decibels per meter and n ? 0.5 in fine-grained clays. A least squares fit of a second degree polynomial describes the mutual relationship between the mean grain size and the attenuation coefficient. When it is used to predict the mean grain size, an almost perfect coincidence with the values derived from sedimentological measurements is achieved.

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Fruit turgidity and firmness have shown to influence impact bruise susceptibility in apples and pears. Analysis of the impact response showed that stresses in the tissues are higher in turgid fruits, so they are more susceptible to bruising. A physical parameter, deformation at skin puncture, was able to detect fruit turgidity changes and showed to be related to bruise susceptibility.

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Cells adapt to their changing world by sensing environmental cues and responding appropriately. This is made possible by complex cascades of biochemical signals that originate at the cell membrane. In the last decade it has become apparent that the origin of these signals can also arise from physical cues in the environment. Our motivation is to investigate the role of physical factors in the cellular response of the B lymphocyte. B cells patrol the body for signs of invading pathogens in the form of antigen on the surface of antigen presenting cells. Binding of antigen with surface proteins initiates biochemical signaling essential to the immune response. Once contact is made, the B cell spreads on the surface of the antigen presenting cell in order to gather as much antigen as possible. The physical mechanisms that govern this process are unexplored. In this research, we examine the role of the physical parameters of antigen mobility and cell surface topography on B cell spreading and activation. Both physical parameters are biologically relevant as immunogens for vaccine design, which can provide laterally mobile and immobile antigens and topographical surfaces. Another physical parameter that influences B cell response and the formation of the cell-cell junction is surface topography. This is biologically relevant as antigen presenting cells have highly convoluted membranes, resulting in variable topography. We found that B cell activation required the formation of antigen-receptor clusters and their translocation within the attachment plane. We showed that cells which failed to achieve these mobile clusters due to prohibited ligand mobility were much less activation competent. To investigate the effect of topography, we use nano- and micro-patterned substrates, on which B cells were allowed to spread and become activated. We found that B cell spreading, actin dynamics, B cell receptor distribution and calcium signaling are dependent on the topographical patterning of the substrate. A quantitative understanding of cellular response to physical parameters is essential to uncover the fundamental mechanisms that drive B cell activation. The results of this research are highly applicable to the field of vaccine development and therapies for autoimmune diseases. Our studies of the physical aspects of lymphocyte activation will reveal the role these factors play in immunity, thus enabling their optimization for biological function and potentially enabling the production of more effective vaccines.

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The virtual (or minimum) height of the F-region (h'F), recorded over a number of solar cycles for I I equatorial and mid-latitude ionosonde stations, was used to deduce the hemispheric (i.e. southern or northern hemisphere) character of equatorial stations. The semi-annual median monthly height (h'F) variations consist of two components: major local summer maximum and winter sub-maximum (about 5 percent of the summer maximum). This hemispheric pattern was most consistently observed for equatorial stations (within 5degrees of the geomagnetic equator) in a period centred on the local midnight (21-03 LT) but was also present, to a lesser extent, at mid-latitude stations and at other time intervals. It is evident that the physical parameter h'F defines the hemispheric character of an equatorial station which has different (sometimes opposite) geographic and geomagnetic latitudes. There is a sharp transition in the latitudinal character of the stations on both sides of the equator leading to hypothesis that the equal maxima in h'F in December and June solstices are observed at a near-equator position labelled as ionosonde deduced equator (IDE). Such a signature was observed for an American equatorial (both geographic and geomagnetic) station Talara (Peru) which is an experimental support of the hypothesis. The IDE can be another useful parameter characterising the equatorial ionosphere. This finding reveals a new application of the standard ionosonde data in defining the geophysical character of equatorial stations, being an important contribution to space climatology. (C) 2002 Elsevier Science Ltd. All rights reserved.

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L’empresa TER és una empresa dedicada al disseny i la construcció de projectes electrònics. La necessitat de comprovar el funcionament dels seus dissenys ha motivat a realitzar un projecte capaç de recollir dades significatives de diferents àmbits com pressió, voltatge, intensitat, temperatura etc. En el mercat les dos maneres més freqüents de recollir aquestes dades són per sensors que donen una equivalència d’un paràmetre físic a un rang de voltatge (0 a 10v) o per corrent (4 a 20mA). Aquestes dades seran adquirides i processades periòdicament per un microcontrolador que les emmagatzemarà una a una per posteriorment visualitzar-les en un LCD o en un programa fet per Visual Basic capaç de generar un document que guardi les dades en Excel. Com a conclusions es pot dir que s’han assolit els objectius, tant els personals com els proposats, per tal de tenir un prototip funcional

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Raaka-aineen hiukkaskoko on lääkekehityksessä keskeinen materiaaliparametri. Lääkeaineen partikkelikoko vaikuttaa moneen lääketuotteen tärkeään ominaisuuteen, esimerkiksi lääkkeen biologiseen hyväksikäytettävyyteen. Tässä diplomityössä keskityttiin jauhemaisten lääkeaineiden hiukkaskoon määrittämiseen laserdiffraktiomenetelmällä. Menetelmä perustuu siihen, että partikkeleista sironneen valon intensiteetin sirontakulmajakauma on riippuvainen partikkelien kokojakaumasta. Työn kirjallisuusosassa esiteltiin laserdiffraktiomenetelmän teoriaa. PIDS (Polarization Intensity Differential Scattering) tekniikka, jota voidaan käyttää laserdiffraktion yhteydessä, on myös kuvattu kirjallisuusosassa. Muihin menetelmiin perustuvista analyysimenetelmistä tutustuttiin mikroskopiaan sekä aerodynaamisen lentoajan määrittämiseen perustuvaan menetelmään. Kirjallisuusosassa esiteltiin myös partikkelikoon yleisimpiä esitystapoja. Työn kokeellisen osan tarkoituksena oli kehittää ja validoida laserdiffraktioon perustuva partikkelikoon määritysmenetelmä tietylle lääkeaineelle. Menetelmäkehitys tehtiin käyttäen Beckman Coulter LS 13 320 laserdiffraktoria. Laite mahdollistaa PIDS-tekniikan käytön laserdiffraktiotekniikan ohella. Menetelmäkehitys aloitettiin arvioimalla, että kyseinen lääkeaine soveltuu parhaiten määritettäväksi nesteeseen dispergoituna. Liukoisuuden perusteella väliaineeksi valittiin tällä lääkeaineella kyllästetty vesiliuos. Dispergointiaineen sekä ultraäänihauteen käyttö havaittiin tarpeelliseksi dispergoidessa kyseistä lääkeainetta kylläiseen vesiliuokseen. Lopuksi sekoitusnopeus näytteensyöttöyksikössä säädettiin sopivaksi. Validointivaiheessa kehitetyn menetelmän todettiin soveltuvan hyvin kyseiselle lääkeaineelle ja tulosten todettiin olevan oikeellisia sekä toistettavia. Menetelmä ei myöskään ollut herkkä pienille häiriöille.

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L’empresa TER és una empresa dedicada al disseny i la construcció de projectes electrònics. La necessitat de comprovar el funcionament dels seus dissenys ha motivat a realitzar un projecte capaç de recollir dades significatives de diferents àmbits com pressió, voltatge, intensitat, temperatura etc. En el mercat les dos maneres més freqüents de recollir aquestes dades són per sensors que donen una equivalència d’un paràmetre físic a un rang de voltatge (0 a 10v) o per corrent (4 a 20mA). Aquestes dades seran adquirides i processades periòdicament per un microcontrolador que les emmagatzemarà una a una per posteriorment visualitzar-les en un LCD o en un programa fet per Visual Basic capaç de generar un document que guardi les dades en Excel. Com a conclusions es pot dir que s’han assolit els objectius, tant els personals com els proposats, per tal de tenir un prototip funcional

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Les modèles sur réseau comme ceux de la percolation, d’Ising et de Potts servent à décrire les transitions de phase en deux dimensions. La recherche de leur solution analytique passe par le calcul de la fonction de partition et la diagonalisation de matrices de transfert. Au point critique, ces modèles statistiques bidimensionnels sont invariants sous les transformations conformes et la construction de théories des champs conformes rationnelles, limites continues des modèles statistiques, permet un calcul de la fonction de partition au point critique. Plusieurs chercheurs pensent cependant que le paradigme des théories des champs conformes rationnelles peut être élargi pour inclure les modèles statistiques avec des matrices de transfert non diagonalisables. Ces modèles seraient alors décrits, dans la limite d’échelle, par des théories des champs logarithmiques et les représentations de l’algèbre de Virasoro intervenant dans la description des observables physiques seraient indécomposables. La matrice de transfert de boucles D_N(λ, u), un élément de l’algèbre de Temperley- Lieb, se manifeste dans les théories physiques à l’aide des représentations de connectivités ρ (link modules). L’espace vectoriel sur lequel agit cette représentation se décompose en secteurs étiquetés par un paramètre physique, le nombre d de défauts. L’action de cette représentation ne peut que diminuer ce nombre ou le laisser constant. La thèse est consacrée à l’identification de la structure de Jordan de D_N(λ, u) dans ces représentations. Le paramètre β = 2 cos λ = −(q + 1/q) fixe la théorie : β = 1 pour la percolation et √2 pour le modèle d’Ising, par exemple. Sur la géométrie du ruban, nous montrons que D_N(λ, u) possède les mêmes blocs de Jordan que F_N, son plus haut coefficient de Fourier. Nous étudions la non diagonalisabilité de F_N à l’aide des divergences de certaines composantes de ses vecteurs propres, qui apparaissent aux valeurs critiques de λ. Nous prouvons dans ρ(D_N(λ, u)) l’existence de cellules de Jordan intersectorielles, de rang 2 et couplant des secteurs d, d′ lorsque certaines contraintes sur λ, d, d′ et N sont satisfaites. Pour le modèle de polymères denses critique (β = 0) sur le ruban, les valeurs propres de ρ(D_N(λ, u)) étaient connues, mais les dégénérescences conjecturées. En construisant un isomorphisme entre les modules de connectivités et un sous-espace des modules de spins du modèle XXZ en q = i, nous prouvons cette conjecture. Nous montrons aussi que la restriction de l’hamiltonien de boucles à un secteur donné est diagonalisable et trouvons la forme de Jordan exacte de l’hamiltonien XX, non triviale pour N pair seulement. Enfin nous étudions la structure de Jordan de la matrice de transfert T_N(λ, ν) pour des conditions aux frontières périodiques. La matrice T_N(λ, ν) a des blocs de Jordan intrasectoriels et intersectoriels lorsque λ = πa/b, et a, b ∈ Z×. L’approche par F_N admet une généralisation qui permet de diagnostiquer des cellules intersectorielles dont le rang excède 2 dans certains cas et peut croître indéfiniment avec N. Pour les blocs de Jordan intrasectoriels, nous montrons que les représentations de connectivités sur le cylindre et celles du modèle XXZ sont isomorphes sauf pour certaines valeurs précises de q et du paramètre de torsion v. En utilisant le comportement de la transformation i_N^d dans un voisinage des valeurs critiques (q_c, v_c), nous construisons explicitement des vecteurs généralisés de Jordan de rang 2 et discutons l’existence de blocs de Jordan intrasectoriels de plus haut rang.

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

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ROTATION is one the most important aspects to be observed in stellar astrophysics. Here we investigate that particularly in stars with planets. This physical parameter supplies information about the distribution of angular momentum in the planetary system, as well as its role on the control of dierent phenomena, including coronal and cromospherical emission and on the ones due of tidal effects. In spite of the continuous solid advances made on the study of the characteristics and properties of planet host stars, the main features of their rotational behavior is are not well established yet. In this context, the present work brings an unprecedented study about the rotation and angular momentum of planet-harbouring stars, as well as the correlation between rotation and stellar and planetary physical properties. Our analysis is based on a sample of 232 extrasolar planets, orbiting 196 stars of dierent luminosity classes and spectral types. In addition to the study of their rotational behavior, the behavior of the physical properties of stars and their orbiting planets was also analyzed, including stellar mass and metallicity, as well as the planetary orbital parameters. As main results we can underline that the rotation of stars with planets present two clear features: stars with Tef lower than about 6000 K have slower rotations, while among stars with Tef > 6000 K we and moderate and fast rotations, though there are a few exceptions. We also show that stars with planets follow mostly the Krafts law, namely < J > / v rot. In this same idea we show that the rotation versus age relation of stars with planets follows, at least qualitatively, the Skumanich and Pace & Pasquini laws. The relation rotation versus orbital period also points for a very interesting result, with planet-harbouring stars with shorter orbital periods present rather enhanced rotation

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Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

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The object of this work was to make a morphometric characterization of the Bobo river watershed in the Nariño department in Colombia. A map was created from topographical maps (1:25.000 scale) using the drainage network and the limit of each 2nd order microbasin as database. Dimensional, drainage network and relief morphometric parameters were evaluated for a later hy-drological study. The drainage area was 224.97 km2, having a 71.31 km perimeter. The Bobo river watershed is considered to be 6th order and has 176 2nd order drainage channels, 34 3rd order drainage channels, 9 4th order drainage channels and 3 5th order drainage channels. Average drainage density is 3.71km/km2, reflecting its high density, having strong, dissected geological formation. The area has a typical Andean land-use pattern, having native wooded vegetation, traditional transitory potato and vegetable growing predominating.

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Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

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The increased demand for using the Industrial, Scientific and Medical (ISM) unlicensed frequency spectrum has caused interference problems and lack of resource availability for wireless networks. Cognitive radio (CR) have emerged as an alternative to reduce interference and intelligently use the spectrum. Several protocols were proposed aiming to mitigate these problems, but most have not been implemented in real devices. This work presents an architecture for Intelligent Sensing for Cognitive Radios (ISCRa), and a spectrum decision model (SDM) based on Artificial Neural Networks (ANN), which uses as input a database with local spectrum behavior and a database with primary users information. For comparison, a spectrum decision model based on AHP, which employs advanced techniques in its spectrum decision method was implemented. Another spectrum decision model that considers only a physical parameter for channel classification was also implemented. Spectrum decision models evaluated, as well as ISCRa's architecture were developed in GNU-Radio framework and implemented on real nodes. Evaluation of SDMs considered metrics of: delivery rate, latency (Round Trip Time - RTT) and handoff. Experiments on real nodes showed that ISCRa architecture with ANN based SDM increased packet delivery rate and presented fewer frequency variation (handoff) while maintaining latency. Considering higher bandwidth as application's Quality of Service requirement, ANN-SDM obtained the best results when compared to other SDM for cognitive radio networks (CRN).

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Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)