The isotropic-nematic interface in suspensions of hard rods: Mean-field properties and capillary waves

We present a study of the isotropic-nematic interface in a system of hard spherocylinders. First we compare results from Monte Carlo simulations and Onsager density functional theory for the interfacial profiles of the orientational order parameter and the density. Those interfacial properties that are not affected by capillary waves are in good agreement, despite the fact that Onsager theory overestimates the coexistence densities. Then we show results of a Monte Carlo study of the capillary waves of the interface. In agreement with recent theoretical investigations (Eur.Phys.J. E {\bf 18} 407 (2005)) we find a strongly anistropic capillary wave spectrum. For the wave-numbers accessed in our simulations, the spectrum is quadratic, i.e.elasticity does not play a role. We conjecture that this effect is due to the strong bending rigidity of the director field in suspensions of spherocylinders.Comment: 8 pages, 10 figure

Methods for tree cover extraction from high resolution orthophotos and airborne LiDAR scanning in Spanish dehesas

[EN] Dehesas are high value agroecosystems that benefit from the effect tree cover has on pastures. Such effect occurs when tree cover is incomplete and homogeneous. Tree cover may be characterized from field data or through visual interpretation of remote sensing data, both time-consuming tasks. An alternative is the extraction of tree cover from aerial imagery using automated methods, on spectral derivate products (i.e. NDVI) or LiDAR point clouds. This study focuses on assessing and comparing methods for tree cover estimation from high resolution orthophotos and airborne laser scanning (ALS). RGB image processing based on thresholding of the ‘Excess Green minus Excess Red’ index with the Otsu method produced acceptable results (80%), lower than that obtained by thresholding the digital canopy model obtained from the ALS data (87%) or when combining RGB and LiDAR data (87.5%). The RGB information was found to be useful for tree delineation, although very vulnerable to confusion with the grass or shrubs. The ALS based extraction suffered for less confusion as it differentiated between trees and the remaining vegetation using the height. These results show that analysis of historical orthophotographs may be successfully used to evaluate the effects of management changes while LiDAR data may provide a substantial increase in the accuracy for the latter period. Combining RGB and Lidar data did not result in significant improvements over using LIDAR data alone.[ES] Las dehesas son agroecosistemas de alto valor que se benefician del efecto de la cobertura arbórea sobre el pasto. Este efecto facilitador aparece cuando la cobertura arbolada es incompleta y homogénea. La cobertura arbórea puede caracterizarse con datos de campo o mediante fotointerpretación de datos de teledetección, ambas tareas que requieren mucho tiempo. Una alternativa es extraer la cobertura arbórea a partir de imagen aérea, derivados espectrales (i.e. NDVI) o nubes de puntos LiDAR. Este estudio se centra en evaluar y comparar métodos para la estimación de cobertura arbolada a partir de ortofotografías de alta resolución y LiDAR aeroportado (ALS). El procesado de imagen RGB basado en la umbralización del índice ‘Excess green minus excess red’ con el método de Otsu produjo resultados aceptables, algo peores que los obtenidos mediante umbralización del modelo digital de copa obtenido con datos ALS (87%) o al combinar datos RGB y LiDAR (87.5%). La información RGB resultó ser útil para la delineación de copas, aunque muy vulnerable a la confusión con pastos o arbustos. La extracción basada en ALS sufrió menos confusión, ya que diferencia entre el arbolado y otros tipos de vegetación usando la altura. Estos resultados muestran que el análisis de ortofotografías históricas podría usarse para evaluar el efecto en los cambios en la gestión, mientras que los datos LiDAR pueden permitir un aumento sustancial en la precisión en períodos posteriores. Combinar LiDAR y RGB no produjo una mejora sustancial sobre el uso de datos LiDAR.IGN and the Andalusian government are acknowledged for providing the airborne datasets. The study was carried out under the projects LIFE+ bioDehesa (LIFE11/BIO/ES/000726) and FUNDIVER (MINECO, Spain; CGL2015-69186-C2-2-R projects), funded through the LIFE+ program.Borlaf-Mena, I.; Tanase, MA.; Gómez-Sal, A. (2019). Métodos para la estimación de la cabida cubierta a partir de ortofotografías de alta resolución y LiDAR aeroportado en dehesas españolas. Revista de Teledetección. (53):17-32. https://doi.org/10.4995/raet.2019.11320SWORD17325

Electric single-molecule hybridization detector for short DNA fragments

By combining DNA nanotechnology and high-bandwidth single-molecule detection in nanopipets, we demonstrate an electric, label-free hybridization sensor for short DNA sequences (<100 nucleotides). Such short fragments are known to occur as circulating cell-free DNA in various bodily fluids, such as blood plasma and saliva, and have been identified as disease markers for cancer and infectious diseases. To this end, we use as a model system an 88-mer target from the RV1910c gene in Mycobacterium tuberculosis, which is associated with antibiotic (isoniazid) resistance in TB. Upon binding to short probes attached to long carrier DNA, we show that resistive-pulse sensing in nanopipets is capable of identifying rather subtle structural differences, such as the hybridization state of the probes, in a statistically robust manner. With significant potential toward multiplexing and high-throughput analysis, our study points toward a new, single-molecule DNA-assay technology that is fast, easy to use, and compatible with point-of-care environments

Effective LAI and CHP of a single tree from small-footprint full-waveform LiDAR

This letter has tested the canopy height profile (CHP) methodology as a way of effective leaf area index (LAIe) and vertical vegetation profile retrieval at a single-tree level. Waveform and discrete airborne LiDAR data from six swaths, as well as from the combined data of six swaths, were used to extract the LAIe of a single live Callitris glaucophylla tree. LAIe was extracted from raw waveform as an intermediate step in the CHP methodology, with two different vegetation-ground reflectance ratios. Discrete point LAIe estimates were derived from the gap probability using the following: 1) single ground returns and 2) all ground returns. LiDAR LAIe retrievals were subsequently compared to hemispherical photography estimates, yielding mean values within ±7% of the latter, depending on the method used. The CHP of a single dead Callitris glaucophylla tree, representing the distribution of vegetation material, was verified with a field profile manually reconstructed from convergent photographs taken with a fixed-focal-length camera. A binwise comparison of the two profiles showed very high correlation between the data reaching R2 of 0.86 for the CHP from combined swaths. Using a study-area-adjusted reflectance ratio improved the correlation between the profiles, but only marginally in comparison to using an arbitrary ratio of 0.5 for the laser wavelength of 1550 nm

Coupling of morphological instability and kinetic instability: Chemical waves in hydrogen oxidation on a bimetallic Ni/Rh(111) surface

The oxidation and reduction of a bimetallic Ni/Rh model catalyst during the water forming O2+H2 reaction is studied with low-energy electron microscopy, microspot-low-energy electron diffraction, and x-ray photoemission electron microscopy. Oxidation of a submonolayer Ni film results in the formation of three-dimensional (3D) NiO nanoparticles. Reduction of 3D-NiO in H2 produces a dispersed two-dimensional film of metallic Ni. Chemical waves during the O2+H2 reaction involve a cyclic transformation between 3D-NiO and 2D-NiO

Forest fire severity estimation based on the LiDAR-PNOA data and the values of the Composite Burn Index

Revista oficial de la Asociación Española de Teledetección[EN] Mediterranean pine forests in Spain experience wildland fire events with different frequencies, intensities, and severities. An estimation of the fire severity as accurate as possible is required by forest managers to decide which strategy is most appropriate to mitigate the effect of fire. The aim of this research is to estimate the post-fire severity, relating a pool of independent variables derived from the LiDAR (Light Detection And Ranging) points clouds delivered by the National Plan for Aerial Orthophotography (PNOA) to field data based on Composite Burn Index collected in four fires located in Aragón (Spain). Logistic regression models were developed and statistically tested and validated to map fire severity with up to 85.5% accuracy. The canopy relief ratio and the percentage of all returns above one meter height were the most significant variables. In addition, the obtained results are compared to different spectral indices derived from Landsat Thematic Mapper.[ES] Los pinares mediterráneos españoles se ven afectados por incendios forestales con diferente frecuencia, intensidad y severidad. Para su valoración, hay que recurrir a estimaciones lo más precisas posibles de la severidad, la cual podrá ayudar a los gestores del bosque a decidir qué estrategia es más adecuada para mitigar el efecto del fuego. El objetivo de esta investigación es la estimación de la severidad post-incendio, relacionando un conjunto de variables independientes derivadas de las nubes de puntos del vuelo LiDAR (Light Detection And Ranging) del Plan Nacional de Ortofotografía Aérea (PNOA), con datos de campo basados en el índice CBI (Composite Burn Index) y recogidos en cuatro incendios localizados en Aragón. Se ha ajustado un modelo de regresión logística, que tras la validación, ha reportado una precisión del 85,5%, siendo las variables “canopy relief ratio” y el porcentaje de puntos por encima de 1 m de altura sobre el terreno, las incluidas en dicho modelo. Por otro lado, se ha realizado una comparativa de los resultados con índices espectrales derivados de imágenes Landsat Thematic Mapper.Estos trabajos han sido financiados por la beca pre-doctoral (FPI BOA 30, 11/02/2011) del Gobierno de Aragón y el proyecto CGL2014-57013-C2-2-R, y han contado con la ayuda de Francisco Palú, Marco Lorenzo y Emilio Pérez-Aguilar del Servicio Provincial de Agricultura, Ganadería y Medio Ambiente del Gobierno de Aragón. Los au-tores agradecen al Centro Nacional de Información Geográfica y al Centro de Información Territorial de Aragón por proporcionar los datos LiDAR-PNOA y al CENAD “San Gregorio” por facilitar el acceso a las parcelas de campo.Montealegre, AL.; Lamelas, MT.; Tanase, MA.; De La Riva, J. (2017). Estimación de la severidad en incendios forestales a partir de datos LiDAR-PNOA y valores de Composite Burn Index. Revista de Teledetección. (49):1-16. https://doi.org/10.4995/raet.2017.7371SWORD1164

Molybdenum-99 (99Mo) Adsorption Profile of Zirconia-Based Materials for 99Mo/99mTc Generator Application

Technetium-99m (99mTc) plays a major role in diagnostic nuclear medicine and has not yet been replaced with any other radionuclides. It is available through the 99Mo/99mTc generator. The use of low-specific-activity 99Mo for 99Mo/99mTc generator application requires high adsorptive capacity sorbents. This study focused on the determination of 99Mo adsorption capacity of several zirconia materials, namely monoclinic nanozirconia, orthorhombic nanozirconia, sulfated zirconia,   and phosphated zirconia. These materials were synthesized by using the sol-gel method and characterized using FT-IR spectroscopy, X-ray diffraction (XRD), and scanning electron microscopy/energy-dispersive X-ray spectroscopy (SEM-EDS). The determination of 99Mo adsorption capacity of these materials was carried out by soaking the materials in a Na299MoO4 solution with pH of 3 and 7, at temperatures ranging from room temperature to 90 °C, for 1 and 3 hours. The results indicated that monoclinic nanozirconia has a 99Mo adsorption capacity of 76.9 mg Mo/g, whereas orthorhombic nanozirconia, sulfated zirconia, and phosphated zirconia have 99Mo adsorption capacities of 150.1 mg Mo/g, 15.58 mg Mo/g, and 12.74 mg Mo/g, respectively. It appears that orthorhombic nanozirconia has the highest 99Mo adsorption capacity among the synthesized materials and can be applied as a candidate material for the 99Mo/99mTc generator