Generation of Huygens' dipoles for any spherical nanoparticle excited by counter-propagating plane waves: study of scattered helicity.

Helicity and directionality control of scattered light by nanoparticles is an important task in different photonic fields. In this paper, we theoretically demonstrate that scattered light of lossy spherical nanoparticles excited by using two counter-propagating dephased plane waves with opposite helicity ±1 and the adequate selection of dephase and intensity shows a well defined helicity and a controllable scattering directivity. Numerical examples of Si nanospheres are studied showing their potential application to directional nanoantennas with a well defined helicity. The proposed method is valid for any type of nanoparticle, not only lossy ones.

Effects of positive personal and non-personal autobiographical stimuli on emotional regulation in older adults.

People can regulate negative emotional states using personal episodic information stored in memory. However, amongst older adults, assistance in retrieving personal memories might be needed. As such, positive personal images might better facilitate the retrieval of positive personal memories, relative to generic positive images. The present study induced older adults (N = 40; Mage = 76.28) into a negative mood state using a validated film clip ("Dead Man Walking"; Robbins et al. in Dead Man Walking [Cinta Cinematográfica]. PolyGram Filmed Entertainment, Working Title Films, Estados Unidos, 1995). Participants were then shown positive personal images (album photos) or positive non-personal images from the International Affective Picture System (IAPS) and between-group differences in their mood state and their ability to retrieve positive autobiographical memories were measured. Although participants' moods decreased after the negative mood induction, their mood then recovered after picture cuing regardless of whether images were personal or non-personal. Furthermore, the positive mood evoked by non-personal, but not personal, images was significantly positively associated with self-reported feelings of reliving of the memories evoked by those images. These results suggest that, when pictures from personal life are not available, the selection of images able to generate positive autobiographical memories with a sense of reliving, is a feasible tool for older adult's emotional regulation.

Reliable method for assessing the COD mass balance of a submerged anaerobic membrane bioreactor (SAMBR) treating sulphate-rich municipal wastewater.

The anaerobic treatment of sulphate-rich wastewater causes sulphate reducing bacteria (SRB) and methanogenic archaea (MA) to compete for the available substrate. The outcome is lower methane yield coefficient and, therefore, a reduction in the energy recovery potential of the anaerobic treatment. Moreover, in order to assess the overall chemical oxygen demand (COD) balance, it is necessary to determine how much dissolved CH(4) is lost in the effluent. The aim of this study is to develop a detailed and reliable method for assessing the COD mass balance and, thereby, to establish a more precise methane yield coefficient for anaerobic systems treating sulphate-rich wastewaters. A submerged anaerobic membrane bioreactor (SAMBR) treating sulphate-rich municipal wastewater was operated at 33 °C for an experimental period of 90 d, resulting in a high COD removal (approximately 84%) with a methane-enriched biogas of 54 ± 15% v/v. The novelty of the proposed methodology is to take into account the sulphide oxidation during COD determination, the COD removed only by MA and the dissolved CH(4) lost with the effluent. The obtained biomethanation yield (333 L CH(4) kg(-1) COD(REM MA)) is close to the theoretical value, which confirms the reliability of the proposed method.

An explanation for the non-uniform grating effects during recording of diffraction gratings in photopolymers.

The recent results reported in reference 1 have produced an increased interest in explaining deviations from the ideal behavior of the energetic variation of the diffraction efficiency of holographic gratings. This ideal behavior occurs when uniform gratings are recorded, and the index modulation is proportional to the energetic exposure. As a result, a typical sin(2) curve is obtained reaching a maximum diffraction efficiency and saturation at or below this value. However, linear deviations are experimentally observed when the first maximum on the curve is lower than the second. This effect does not correspond to overmodulation and recently in PVA/acrylamide photopolymers of high thickness it has been explained by the dye concentration in the layer and the resulting molecular weight of the polymer chains generated in the polymerization process. In this work, new insights into these deviations are gained from the analysis of the non-uniform gratings recorded. Therefore, we show that deviations from the linear response can be explained by taking into account the energetic evolution of the index modulation as well as the fringe bending in the grating.

Theoretical approach to photoinduced inhomogeneous anisotropy in bacteriorhodopsin films.

The aim of this work was to perform a complete study of the dynamic and steady-state photoinduced processes of thick bacteriorhodopsin (bR) films, taking into account all the physical parameters and the coupling of rate equations with the energy transfer equation. The theoretical approach was compared with experimental data, and good concordance was found between both sets of data. The theoretical approach shows that the values of the rate constants for solid bR films are about two or three orders of magnitude lower than those observed in solution. It can also be noted that the temperature change during the experiment had a great influence on the final values of transmittance and, consequently, on the inhomogeneous distribution along the coordinate of light propagation. The study shows that, depending on the intensity and wavelength of the pump beam, we can obtain a very inhomogeneous profile of the population densities, which implies an inhomogeneous profile of the birefringence and dichroism. Therefore, this must be taken into account in the applications described for this system.

Matrix method for the study of wave propagation in one-dimensional general media.

A matrix method which relates the field and its derivative is presented for the study of wave propagation in any type of one-dimensional media. The transfer matrix is obtained from the canonical solutions of Helmholtz equations at normal incidence. The method is applied to different optical systems like a Fabry-Perot cavity formed by uniform fiber Bragg gratings, periodic dielectric structures and different quasi-periodic structures based on Fibonacci and Thue-Morse sequences of layers with constant and variable refractive index.

Bidimensional chromophores for photorefractive polymers with working wavelength in the near IR.

In this study we show six bidimensional chromophores designed for high Tg photorefractive polymers with a working wavelength in the near IR. The macroscopic optical properties of a poled polymer which contains the designed chromophores were expressed as a function of the microscopic properties of the chromophores, which were calculated using quantum mechanical methods. Later, the diffraction efficiency of a holographic recording and readout experiment was simulated using the Montemezzani equation for anisotropic materials. Results show that high diffraction efficiencies could be obtained for three important working wavelengths (1064, 1300 and 1500 nm) using these chromophores. Of particular interest are the result for the PMC3b derivative at the telecommunication windows of 1300 nm and 1500 nm and the result for PMC1a derivative at the light source wavelength of 1064 nm.

Application of the Fixed Point Theorem for the solution of the 1D wave equation: comparison with exact Mathieu solutions.

A method based in the application of Fixed Point Theorem (FPT) techniques to the solution of the 1D wave equation at normal incidence for materials that present a continuous (real or complex) dielectric constant is presented. As an example, the method is applied for the calculation of the electric field, reflection and transmission spectra in volume holographic gratings. It is shown that the solution obtained using this method agrees with the exact Mathieu solutions also obtained in this paper for volume holographic reflection gratings.

Upper limits of dielectric permittivity modulation in bacteriorhodopsin films.

A theoretical study of light-induced modulation of the dielectric permittivity in bacteriorhodopsin films has been done (including B--> M and B --> Q transitions). Analysis of dielectric permittivity modulation enables us to determine the fundamental limits of BR to be used in a holographic data storage system, together with the optimum experimental and material conditions. In order to carry out this analysis, the macroscopic dielectric permittivity was related to the microscopic polarizability of the three states of BR considered (B, M and Q). This parameter was calculated using a modelization procedure that includes the effect of ASP85, TRP86, and TYR185 amino acid residues (the B3LYP/6-31+ G(*) method was used for the calculations). Good concordance between theoretical calculations and experimental data was found for the linear optical properties (absorption wavelength, transition dipole moment, and dielectric permittivity modulation). The theoretical upper limits of Deltaepsilson at 750 nm (far from the resonance of the molecule) in a randomly oriented material are about 0.01 and 0.012 for B--> M and B--> Q transitions, respectively. The values of Deltaepsilon obtained were used to simulate diffraction efficiencies (eta) of a volume phase hologram recorded in a BR film. The high absorptive losses at low wavelengths (about 625 nm ) cause an interesting behavior, since the highest Deltaepsilom do not produce the greatest eta. The highest eta is produced for a hologram thickness in the range of 900-1000 microm and working wavelength of 700-750 nm.

Acrylamide-N,N'-methylenebisacrylamide silica glass holographic recording material.

In this paper, we describe a photopolymerizable silica glass based on acrylamide (AA) and N,N'-methylenebisacrylamide (BMA) as monomers, triethanolamine (TEA) as coinitiator and yellowish eosin (YE) as photoinitiator. We studied different compositions, analyzing the diffraction efficiency, energetic exposure and effective thickness obtained in the holographic gratings. A diffraction efficiency of 60 % with an energetic exposure of 139 mJ/cm(2) and an effective thickness of 1.1 mm were obtained. Also, by varying the photopolymerizable composition of the material diffraction efficiencies higher than 80 % can be reached with an energetic exposure of 10 mJ/cm(2) and an effective thickness of 113 microm. These values are similar to those obtained in conventional photopolymer systems in polyvinylalcohol and better than the values reached in other sol-gel compositions. Also, 9 holograms were angular multiplexed with diffraction efficiencies between 6 and 12 % and total exposure time shorter than 150 ms, with a dynamic range M/#= 2.4.

Multiplexed holographic gratings for fabricating 3D photonic crystals in BB640 photographic emulsions.

Three multiplexed holographic gratings were used to fabricate 3D photonic crystals without complete band gap using ultra-fine grain holographic emulsion as the storage material. Theoretical and experimental studies were carried out in order to characterize the crystals. Good agreement between theory and experimental results was obtained, showing that it is possible to obtain a band-pass filter for a fixed direction of illumination.

Purple membrane-polyacrilamide films as holographic recording materials.

The holographic parameters of purple membrane-polyacrylamide films obtained from a mutant form of Halobacterium salinarum (originally Halobacterium halobium) were measured. The synthesized films have an absorption of around 2.5 at 532 nm and a pH of 8.65. The results show that diffraction efficiencies of about 1.2 % (measured at 633 nm) can be achieved with writing intensities in the range of 200-400 mW/cm2 (532 nm), and these values remain constant after saturation. Pump-probe experiments were also used to measure the M state lifetime and our PM films were found to have the lowest M state lifetime described at this pH.

Prognostic implications of loss of heterozygosity in the 17q21 region in breast cancer.

Sporadic breast cancer is the commonest form of this malignancy. Genetic changes are frequent events in breast cancer. We investigated the implication of LOH in the 17q21 region as a prognostic factor in this disease. Fifty-three patients were studied and 14 clinico-pathological parameters were evaluated for comparison between the patients with LOH and patients without LOH. A LOH rate of 21% was found and, upon comparison of the two subgroups, a significantly lower rate of recurrence after adjuvant chemotherapy in patients with LOH was observed. This suggests that LOH occurring in this region in breast cancer could help to design new adjuvant treatment strategies.

Accuracy of Topcon CM-1000 videokeratoscope on spherical test surfaces.

BACKGROUND: Many videokeratoscopes use mathematical formulas to calculate corneal radii; calculations depend on slope, curvature, coordinate position, or focal properties of the surface. Accuracy of each type of videokeratoscope must be evaluated. A controversy exists about whether axial or tangential methods best provide a precise description of corneal shape; therefore results with the Topcon CM-1000 using both methods were evaluated. METHODS: Measurements were done on black polymethylmethacrylate (PMMA) spherical calibrated surfaces. Lenses were first aligned and measured and then misaligned in different directions and measured. Results for each position were compared with the zero or alignment position. RESULTS: Accuracy of the CM-1000 was high even under extreme misalignment conditions. Tolerance to misalignment was high (about 300 mm). Misalignment-induced variations in the output results were small (usually less than 0.05 mm). However, important variations (more than 1.00 diopter [D]) were found for the lowest measured radius (6 mm). In some cases, small differences between axial and tangential radii for the same point could be found. CONCLUSION: With the exception of extremely low radii of curvature, the CM-1000 was accurate for measuring spherical surfaces. Further investigation remains to be done on aspheric surfaces and in clinical practice.

[Hepato-cholangiocarcinoma with diffuse metastases and hypercalcemia]. / Hepatocolangiocarcinoma con metástasis difusas e hipercalcemia.

The combined hepatocellular-cholangiocarcinoma (C-HCC) is a very uncommon neoplasm, its diagnosis is difficult and its course is usually very rapid. We report the case of a patient with CHCC type II or transitional tumor, which shows two cellular types in certain zones. Our patient had tumoral hypercalcemia as well, which was very difficult to control. There was a metastatic spread with cholangiolar features almost from the beginning, that made impossible any sort of therapy. It seems that dissemination followed lymphatic pathways.

[Idiopathic cholestasis associated with progressive ductopenia in two patients with hodgkin's disease]. / Colestasis idiopática asociada a ductopenia progresiva en dos pacientes con linfoma de Hodgkin.

INTRODUCTION: Jaundice in Hodgkin's disease can be due to several causes. Ductal lesions and ductopenia, which we describe below, have rarely been reported. CASE REPORT: We describe 2 cases of idiopathic cholestasis associated with Hodgkin's disease in which duction lesions and ductopenia were found. In one case, the ductal lesion progressed to ductopenia and the patient died from complications of her oncological disease while in the second case, outcome was favorable with improvement of cholestasis and remission of Hodgkin's lymphoma. DISCUSSION: Ductopenia should be included in the differential diagnosis of cholestasis associated with Hodgkin's disease, for which a high degree of suspicion is required. Hodgkin's disease should be suspected when ductopenia is found.

Experimental study of the anaerobic urban wastewater treatment in a submerged hollow-fibre membrane bioreactor at pilot scale.

The aim of this study was to assess the effect of several operational variables on both biological and separation process performance in a submerged anaerobic membrane bioreactor pilot plant that treats urban wastewater. The pilot plant is equipped with two industrial hollow-fibre ultrafiltration membrane modules (PURON® Koch Membrane Systems, 30 m² of filtration surface each). It was operated under mesophilic conditions (at 33 °C), 70 days of SRT, and variable HRT ranging from 20 to 6h. The effects of the influent COD/SO4-S ratio (ranging from 2 to 12) and the MLTS concentration (ranging from 6 to 22 g L⁻¹) were also analysed. The main performance results were about 87% of COD removal, effluent VFA below 20 mg L⁻¹ and biogas methane concentrations over 55% v/v. Methane yield was strongly affected by the influent COD/SO4-S ratio. No irreversible fouling problems were detected, even for MLTS concentrations above 22 g L⁻¹.