The period of a classical oscillator

We develop a simple method to obtain approximate analytical expressions for the period of a particle moving in a given potential. The method is inspired to the Linear Delta Expansion (LDE) and it is applied to a large class of potentials. Precise formulas for the period are obtained.Comment: 5 pages, 4 figure

Systematic perturbation calculation of integrals with applications to physics

In this paper we generalize and improve a method for calculating the period of a classical oscillator and other integrals of physical interest, which was recently developed by some of the authors. We derive analytical expressions that prove to be more accurate than those commonly found in the literature, and test the convergence of the series produced by the approach.Comment: 11 pages, 5 figure

Speckle fluctuations resolve the interdistance between incoherent point sources in complex media

We study the fluctuations of the light emitted by two identical incoherent point sources in a disordered environment. The intensity-intensity correlation function and the speckle contrast, obtained after proper temporal and configurational averaging, encode the relative distance between the two sources. This suggests the intriguing possibility that intensity measurements at only one point in a speckle pattern produced by two incoherent sources can provide information about the relative distance between the sources, with a precision that is not limited by diffraction. The theory also suggests an alternative approach to the Green's-function retrieval technique, where the correlations of the isotropic ambient noise detected by two receivers are replaced by a measurement at a single point of the noise due to two fluctuating incoherent sources

Photodynamic therapy of cutaneous T-cell lymphoma cell lines mediated by 5-aminolevulinic acid and derivatives

The delta-amino acid 5-aminolevulinic acid (ALA), is the precursor of the endogenous photosensitiser Protoporphyrin IX (PpIX), and is currently approved for Photodynamic Therapy (PDT) of certain superficial cancers. However, ALA-PDT is not very effective in diseases in which T-cells play a significant role. Cutaneous T-cell lymphomas (CTCL) is a group of non-Hodgkin malignant diseases, which includes mycosis fungoides (MF) and Sézary syndrome (SS). In previous work, we have designed new ALA esters synthesised by three-component Passerini reactions, and some of them showed higher performance as compared to ALA. This work aimed to determine the efficacy as pro-photosensitisers of five new ALA esters of 2-hydroxy-N-arylacetamides (1f, 1 g, 1 h, 1i and 1 k) of higher lipophilicity than ALA in Myla cells of MF and HuT-78 cells of SS. We have also tested its effectiveness against ALA and the already marketed ALA methyl ester (Me-ALA) and ALA hexyl ester (He-ALA). Both cell Myla and SS cells were effectively and equally photoinactivated by ALA-PDT. Besides, the concentration of ALA required to induce half the maximal porphyrin synthesis was 209 μM for Myla and 169 μM for HuT-78 cells. As a criterion of efficacy, we calculated the concentration of the ALA derivatives necessary to induce half the plateau porphyrin values obtained from ALA. These values were achieved at concentrations 4 and 12 times lower compared to ALA, according to the derivative used. For He-ALA, concentrations were 24 to 25 times lower than required for ALA for inducing comparable porphyrin synthesis in both CTCL cells. The light doses for inducing 50% of cell death (LD50) for He-ALA, 1f, 1 g, 1 h and 1i were around 18 and 25 J/cm2 for Myla and HuT-78 cells respectively, after exposure to 0.05 mM concentrations of the compounds. On the other hand, the LD50s for the compound 1 k were 40 and 57 J/cm2 for Myla and HuT-78, respectively. In contrast, 0.05 mM of ALA and Me-ALA did not provoke photokilling since the concentration employed was far below the porphyrin saturation point for these compounds. Our results suggest the potential use of ALA derivatives for topical application in PDT treatment of MF and extracorporeal PDT for the depletion of activated T-cells in SS

Dynamical and temporal characterization of the total ozone column over Spain

As the ozone is one of the most relevant variables in the climate system, to get further in its long-term characterization is a critical issue. In this study, measurements of total ozone column (TOC) from five well-calibrated Brewer spectrophotometers placed in the Iberian Peninsula are analyzed. The temporal trend rate for TOC is +9.3 DU per decade for the period 1993–2012 in Central Iberian Peninsula. However, the low TOC levels during 2011 and 2012 over the study region notably reduce this rate. Empirical linear relationships are established between TOC and pressure, height, and temperature of the tropopause. The linear fits showed seasonal and latitudinal dependence, with stronger relationships during winter and spring. Events with the presence of a double tropopause (DT) are proved to be characteristic of the study region. The decrease in TOC levels when these anomalous events occur is quantified around 10 % in winter and spring with respect to the usual cases with a single tropopause. The total weight of the DT events with respect to the annual values is about 20 %, with a negligible occurrence in summer and autumn and being latitudinal-dependent. The North Atlantic Oscillation (NAO) index explains 30 % of the total ozone variability in winter. The DT events are found to be more frequent during phases with positive NAO.This work was partially supported the Ministerio de Ciencia e Innovación through project CGL2011-29921-C02-01

Modelagem matemática da secagem de bagaço de laranja associado ao método convectivo e radiação infravermelha

Sem informaçãoMathematical modeling enables dimensioning of dryers, optimization of drying conditions and the evaluation of process performance. The aim of this research was to describe the behavior of orange bagasse drying using Page's and Fick's second law models, and to assess activation energy (using Arrhenius equation), moisture content, water activity and bulk density of product at the end of the process. The drying experimental assays were performed in 2011 with convective air temperature between 36 and 64 degrees C and infrared radiation application time in the range from 23 to 277 s in accordance with the experimental central composite rotatable design. Analysis of variance and F-test were applied to results. At the end of the drying process, moisture content was about 0.09 to 0.87 db and water activity was between 0.25 and 0.87. Bulk density did not vary under studied conditions. Empirical Page's model demonstrated better representation of experimental data than the Fick's model for spheres. Activation energy values were about 18.491; 14.975 and 11.421 kJ mol(-1) for infrared application times of 60; 150 e 244 s, respectively.Mathematical modeling enables dimensioning of dryers, optimization of drying conditions and the evaluation of process performance. The aim of this research was to describe the behavior of orange bagasse drying using Page's and Fick's second law models, an191211781184Sem informaçãoSem informaçãosem informaçãoA modelagem matemática permite o dimensionamento de secadores, otimização das condições de secagem e avaliação do desempenho do processo. O objetivo deste trabalho foi descrever o comportamento da secagem de bagaço de laranja utilizando-se os modelos de

Transition from Diffusive to Localized Regimes in Surface Corrugated Optical Waveguides

Exact calculations of the transmittance of surface corrugated optical waveguides are presented. The elastic scattering of diffuse light or other electromagnetic waves from a rough surface induces a diffusive transport along the waveguide axis. As the length of the corrugated part of the waveguide increases, a transition from the diffusive to the localized regime is observed. This involves an analogy with electron conduction in nanowires, and hence, a concept analogous to that of ``resistance'' can be introduced. We show an oscillatory behavior of both the elastic mean free path and the localization length versus the wavelength.Comment: 3 pages, REVTEX, 3 PS figure