Algorithms for Coloring Quadtrees

We describe simple linear time algorithms for coloring the squares of balanced and unbalanced quadtrees so that no two adjacent squares are given the same color. If squares sharing sides are defined as adjacent, we color balanced quadtrees with three colors, and unbalanced quadtrees with four colors; these results are both tight, as some quadtrees require this many colors. If squares sharing corners are defined as adjacent, we color balanced or unbalanced quadtrees with six colors; for some quadtrees, at least five colors are required.     

SEM study of the growth of electrochemically obtained polyselenophene thin films. Effect of electrolyte and monomer concentration in acetonitrile

Summary The influence of electrolyte and monomer concentration on properties and morphology of electrochemically obtained polyselenophene films doped and undoped with hexafluorophosphate and tetrafluoroborate anions was analyzed. The films were deposited on SnO₂-coated glass in a classical three-electrode cell from the monomer and the electrolyte in anhydrous acetonitrile.The electrochemical growth of polyselenophene thin films was studied by X-ray photoelectron spectroscopy (XPS), electron probe microanalysis (EPMA), and scanning electron microscopy (SEM). The morphology study revealed different three- dimensional (3D) and bidimensional (2D) growth, depending on monomer and electrolyte concentration.     

First observation of the fourth neutral polarization point in the atmosphere

In the clear sky there are three commonly known loci, the Arago, Babinet, and Brewster neutral points, where the skylight is unpolarized. These peculiar celestial points, bearing the names of their discoverers, have been the subject of many ground-based investigations, because their positions are sensitive indicators of the amount and type of atmospheric turbidity. According to theoretical considerations and computer simulations, there should exist an additional neutral point approximately opposite to the Babinet point, which can be observed only at higher altitudes in the air or space. Until now, this anonymous "fourth" neutral point has not been observed during air- or space-borne polarimetric experiments and has been forgotten, in spite of the fact that the neutral points were a basic tool in atmospheric research for a century. Here, we report on the first observation of this fourth neutral point from a hot air balloon. Using 180 degrees-field-of-view imaging polarimetry, we could observe the fourth neutral point at 450, 550, and 650 nm from different altitudes between 900 and 3500 m during and after sunrise at approximately 22 degrees - 40 degrees below the anti-solar point along the anti-solar meridian, depending on the wavelength and solar elevation. We show that the fourth neutral point exists at the expected location and has characteristics similar to those of the Arago, Babinet, and Brewster points. We discuss why the fourth neutral point has not been observed in previous air- or space-borne polarimetric experiments.     

Mapping the human retina

The new therapeutic method of scotoma-based photocoagulation (SBP) developed at the Vienna Eye Clinic for diagnosis and treatment of age-related macular degeneration requires retinal maps from scanning laser ophthalmoscope images. This paper describes in detail all necessary image analysis steps for map generation. A prototype software system for fully automatic map generation has been implemented and tested on a representative dataset selected from a clinical study with 50 patients. The map required for the SBP treatment can be reliably extracted in all cases. Thus, algorithms presented in this paper should be directly applicable in daily clinical routine without major modifications.     

On the ultrathin gold film used as buffer layer at the transparent conductive anode/organic electron donor interface

Previously, we have shown that a gold thin film of only 0.5 nm introduced at the interface between the indium tin oxide or ZnO anode and the organic electron donor in organic photovoltaic cells induces a strong improvement of the cell efficiency. Of course a thickness of 0.5 nm corresponds only to an averaged thickness, the films being too thin to be continuous. For a clear understanding of the physical mechanisms that are responsible for this improved behaviour, it is important to know the fractional coverage and the island height of this thin Au film. In the present work, we have used two different techniques, such as treated scanning electron microscope images and analysis of the inelastic part of peaks of X-ray photoelectron spectroscopy spectra, to estimate the gold coverage and island height of the transparent conductive anode. There is an excellent agreement between the results achieved by both methods. Only 15% of the anode is covered, which proves the high efficiency of gold as an anode buffer layer in organic photovoltaic devices.     

Response of the Rhône deltaic margin to loading and subsidence during the last climatic cycle

Passive continental margin subsidence is initiated by the synrift mechanical stretching of the lithospheric upper brittle layer and continues during the postrift phase; the thermal cooling and contraction of the upwelled asthenosphere forces the margin to subside in addition to the overloads from sea water and sediments. Therefore, the total subsidence in stretched basins includes fault-controlled initial sinking, thermal subsidence and flexural isostatic compensations. Decoupling and estimating the different components of this subsidence from stratigraphic analysis and restricted geophysical and sedimentological databases remains problematic. In particular, backstripping the sediment layers requires a well-constrained geological framework. A method is proposed here to investigate the subsidence history of a margin based on forward stratigraphic modelling. Using the Sedflux model, several experiments are done using generally agreed upon assumptions on the parameters describing lithospheric rheology and isostatic behaviour of a margin. The stratigraphic modelling of the Rhône deltaic margin during the last climatic cycle (125 kyr) provides an assessment of these parameter estimates and their influence on geohistory (tectonic/thermal subsidence and sediment loading). The model results confirm the important impact of water loading on vertical deflection along the platform between glacial low sea-level and interglacial high sea-level. Based on Gulf of Lions (NW Mediterranean) observations, a conceptual method that uses the stratigraphic simulations is produced in order to evaluate the different components of the total subsidence of a margin, and, in particular, the relative impact of tectonic subsidence and sediment load.     

Characterization of electrosynthesized polydihaloanilines

The nucleation and growth mechanism of some homopolymers of aniline (six monomers were studied: 3,5‐dichloroaniline, 2,5‐dichloroaniline, 2,6‐dichloroaniline, 2,3‐dichloroaniline, 2,5‐dibromoaniline, and 2,6‐dibromoaniline), synthesized by potentiostatic methods, was determined with a mathematical model that considers different contributions from current–time transients with a gold‐disc electrode. Deconvolution of the transients for the dichlorinated monomers showed IN3D_ct and PN3D_dif contributions (where IN3D_ct refers to an instantaneous nucleation and three‐dimensional growth mechanism under charge‐transfer control and PN3D_dif refers to a progressive nucleation and three‐dimensional growth mechanism under diffusion control), whereas IN2D and PN3D_dif components and IN2D, IN3D_ct, and PN3D_dif components (where IN2D refers to an instantaneous nucleation and two‐dimensional growth mechanism) were needed for 2,5‐dibromoaniline and 2,6‐dibromoaniline, respectively. The percentage of the contribution of the current–time transient to the total charge was worked out for each monomer. The effect of the scan rate on the voltammetric profile during the potentiodynamic electrosynthesis of the polymers was studied too. Curves of the current versus the square root of the potential scan rate were recorded for a selected group of monomers, and the slope was considered an estimation of the diffusion coefficient of the respective monomer. Furthermore, the electrosynthesized polymers were characterized with Fourier transform infrared, ultraviolet–visible, X‐ray photoelectron spectroscopy, and scanning electron microscopy. Microanalysis, used to establish the ratio of the atomic percentages of P and N for each polymer synthesized at a constant potential, was performed for doped and undoped polymers. This parameter was a measure of the degree of electrochemical doping. The conductivity of the doped and undoped polymers was also measured. Hence, the systematic characterization of this analogue series of monomers allows, before generalization, an adequate experimental design to prepare polymers with the properties required for their use. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

EXISTENCE OF A GENERALIZED SOLUTION IN THERMOELASTICITY WITH TWO RELAXATION TIMES,PART II

The existence of a generalized solution to a natural stress-temperature initial-boundary value problem of linear thermoelasticity with two relaxation times is established in a functional space of the Sobolev type.     

Microstructural properties of ZnO:Sn thin films deposited by intermittent spray pyrolysis process

Zinc oxide films have been prepared via spray pyrolysis using a perfume atomizer. ZnCl₂ has been used as precursor. The influence of the precursor solution and dopant concentration has been investigated. Homogeneous films are obtained with a precursor concentration ranging between 0.3 and 0.4 M and a SnCl₂ dopant concentration of 1–2%. The films exhibit broad band gaps and small conductivity. The microstructural properties of these films have been compared with that of films deposited using a classical nozzle. Films deposited by perfume atomizer are rougher, with smaller grain size, compared to films deposited with a classical nozzle.