Search results for "Lens"
showing 10 items of 948 documents
¿Se han hecho más democráticos los partidos en España? La evolución en las reglas de elección del líder (1977-2008)
2011
En este trabajo, los autores verifican si, entre 1977 y 2008, ha habido un aumento de la democracia interna en los principales partidos políticos españoles. Para ello, analizan el proceso de selección del líder, al tiempo que cuestionan si ha habido un incremento de la igualdad en la participación para elegirlo, favoreciendo sistemas representativos o de elección directa. El artículo plantea también la hipótesis de si el grado de igualdad en las reglas de la elección influye en el grado de competencia en la lucha por el liderazgo del partido. Para comprobar tal supuesto, los autores examinan las condiciones de elegibilidad así como la representatividad del cuerpo electoral que escoge al líd…
Gravitational Lensing of Supernova Neutrinos
2006
The black hole at the center of the galaxy is a powerful lens for supernova neutrinos. In the very special circumstance of a supernova near the extended line of sight from Earth to the galactic center, lensing could dramatically enhance the neutrino flux at Earth and stretch the neutrino pulse.
Variable fractional Fourier processor: a simple implementation
1997
A new set of optical implementations of the fractional Fourier transform (FRT) is developed by use of Wigner matrix algebra. The reinterpretation of some elementary operations that synthesize a rotation in the phase-space domain allows us to propose a lensless setup for obtaining the FRT. This compact configuration is also very flexible, because the fractional degree of the transformation can be varied continuously by shifting the input and the output planes along the optical axis by proper amounts. The above results permit one to build an optical FRT processor formed by two FRT systems in cascade, with a spatial filter between them. We present the design of such a variable FRT processor, w…
Super Resolution Methods Implementing Diffractive Masks Having a Certain Degree of Periodicity
2011
This section presents an approach that provides super resolved imaging at the center of the field of view and yet allows to see the remaining of the original field of view with original resolution. This operation resembles optical zooming while the zoomed and the nonzoomed images are obtained simultaneously. This is obtained by taking a single snap-shot and using a single imaging lens. The technique utilizes a special static/still coding element and a postprocessing algorithmic, without any mechanical movements.
Monitoring supercritical fluid extraction by thermal lens spectrometry with pulsed laser excitation
1999
Abstract A dual-beam thermal lens spectrometer (TLS) with a pulse pump–probe coaxial configuration was coupled to commercially available supercritical fluid extraction equipment using a high-pressure flow cell interface. Because of its feasible critical parameters, moderate cost and good thermooptical properties, carbon dioxide was used as supercritical solvent. Using trans -β-carotene as analyte, several factors related with the extraction process under continuos flow conditions were studied in order to establish their influence in the thermal lens signal magnitude. Under the optimum experimental conditions, the relative TLS signal area showed a linear relationship with the concentration o…
Reduction of Convective Low-Frequency Noise in Thermal Lens Spectrometry
1990
The construction and optimization of a thermal lens spectrometer with coaxial pump/probe configuration is reported. The low-frequency noise of convective origin is studied in detail, and it is demonstrated that a horizontal slit, instead of a pinhole, can be used as a simple way of reducing the noise to a negligible level without losing sensitivity.
Rapid determination of baicalin and total baicalein content in Scutellariae radix by ATR-IR and NIR spectroscopy
2013
In this study methods for the quantification of baicalin and total baicalein in Scutellariae radix with near infrared (NIR) spectroscopy and attenuated-total-reflectance mid-infrared (ATR-IR) spectroscopy in hyphenation with multivariate analysis were developed and compared. The reference analysis was performed by high performance liquid chromatography coupled to diode array detection (HPLC-DAD). Different pretreatments like standard normal variate (SNV), multiplicative scatter correction (MSC), first and second derivative Savitzky-Golay were applied on the spectra to optimize the calibrations. A principal component analysis was performed with both spectroscopic methods to distinguish wild …
Magnetic resonance imaging of the siliceous skeleton of the demosponge Lubomirskia baicalensis
2005
The skeletal elements (spicules) of the demosponge Lubomirskia baicalensis were analyzed; they are composed of amorphous, non-crystalline silica, and contain in a central axial canal the axial filament which consists of the enzyme silicatein. The axial filament, that orients the spicule in its longitudinal axis exists also in the center of the spines which decorate the spicule. During growth of the sponge, new serially arranged modules which are formed from longitudinally arranged spicule bundles are added at the tip of the branches. X-ray analysis revealed that these serial modules are separated from each other by septate zones (annuli). We describe that the longitudinal bundles of spicule…
<b>ANTIMICROBIAL DITERPENOID ALKALOIDS FROM <i>ERYTHROPHLEUM SUAVEOLENS</i> (GUILL. & PERR.) BRENAN</b>
2005
An investigation of the stem bark of Erythrophleum suaveolens (Guill. & Perr.) Brenan yielded the known amide norcassaide ( 1 ) and a new diterpenoid alkaloid named norerythrosuaveolide ( 2 ) which was characterized as 7β-hydroxy-7-deoxo-6-oxonorcassaide. The structures were established on the basis of one and two-dimensional 1 H and 13 C NMR spectral data. The compounds showed potent antimicrobial activities against bacteria and yeasts. KEY WORDS: Erythrophleum suaveolens (Guill. & Perr.) Brenan, Norcassaide, Diterpenoid alkaloid, Norerythrosuaveolide, Antimicrobial activities, Bacteria, Yeasts Bull. Chem. Soc. Ethiop. 2005, 19(2), 221-226.
Structure finding in cosmological simulations: the state of affairs
2013
The ever increasing size and complexity of data coming from simulations of cosmic structure formation demands equally sophisticated tools for their analysis. During the past decade, the art of object finding in these simulations has hence developed into an important discipline itself. A multitude of codes based upon a huge variety of methods and techniques have been spawned yet the question remained as to whether or not they will provide the same (physical) information about the structures of interest. Here we summarize and extent previous work of the "halo finder comparison project": we investigate in detail the (possible) origin of any deviations across finders. To this extent we decipher…