Dos lepiotas mediterráneas poco conocidas

Se describen Echinoderma sinopicum y Lepiota griseovirens, recolectadas en el centro peninsular en suelos arenosos básicos. Se aportan macro . y microfotografias de las características más sobresalientes de ambas especies, así como datos coro lógicos, taxonómicos y bibliográficos. Ambas especies presentan interés corológico por su marcada distribución mediterránea.Two little known mediterranean species of Lepiota. Echinoderma sinopicum and Lepiota griseovirens, found in sandy and calcareous soils in central Spain, are described. Macro and microphotographs of the most striking features of both taxa, as well as chorological, taxonomical and bibliographical data, are added. 80th taxa show some chorological interest, because of their marked mediterranean distribution

Dos lepiotas mediterráneas poco conocidas

Two little known mediterranean species of Lepiota. Echinoderma sinopicum and Lepiota griseovirens, found in sandy and calcareous soils in central Spain, are described. Macro and microphotographs of the most striking features of both taxa, as well as chorological, taxonomical and bibliographical data, are added. 80th taxa show some chorological interest, because of their marked mediterranean distribution.Se describen Echinoderma sinopicum y Lepiota griseovirens, recolectadas en el centro peninsular en suelos arenosos básicos. Se aportan macro . y microfotografias de las características más sobresalientes de ambas especies, así como datos coro lógicos, taxonómicos y bibliográficos. Ambas especies presentan interés corológico por su marcada distribución mediterránea

Raman spectroscopy of boron nitride nanotubes and boron nitride-carbon composites

Boron nitride nanotubes (BN-NT) are topological analoges to single wall carbon nanotubes (SWCNT). We analysed and refined the filling process for SWCNTs and applied it to the BN-NTs. BN-NTs were first annealed in air to open the ends and to remove BN particles. A filling procedure with C60 fullerene via vapour phase was applied. Subsequently high temperature treatment was performed to transform the fullerenes. Some spectral features in the Raman spectra of the reaction products in the low frequency range may be assigned to small diameter carbon nanotubes inside the BN-NTs

Caloplaca cerina en los Pirineos de Huesca.

A. R. BURGAZ, E ARENAl.. y. GoNZÁlEZ ANO E. ESTEvE-RAvENTóS. 1999. Caloplaca cerina en los Pirineos de Huesca. Bol, Conípluíensis 23: 5357 Se estudia una población de Calopíaca ce/ma (Ehrh. ex Hedwig) Th. Fr. procedente del piso subalpino de los Pirineos oscenses que presenta ascosporas con un grosor del septo inIrecuente. Se incluyen fotografías de los caracteres más destacables.A. R. BtRGAz, F. ARENAL, V. CONZÁLEz AND F. ESTEvE-RAvENTóS. 1999. Caloplaca cer/na ín thc Pyrenees mountains of Huesca Province. Eot, Complutensis 23: 53-57. A population of Caloplaca cerina (Ehrh. ex t-ledwig) Th. Fr. from the subalpine belt in Huesca Province with an infrequent ascospore septum thickness is studied. Macro and microphotographs of the most striking features are added

Atomic Configuration of Nitrogen Doped Single-Walled Carbon Nanotubes

Having access to the chemical environment at the atomic level of a dopant in a nanostructure is crucial for the understanding of its properties. We have performed atomically-resolved electron energy-loss spectroscopy to detect individual nitrogen dopants in single-walled carbon nanotubes and compared with first principles calculations. We demonstrate that nitrogen doping occurs as single atoms in different bonding configurations: graphitic-like and pyrrolic-like substitutional nitrogen neighbouring local lattice distortion such as Stone-Thrower-Wales defects. The stability under the electron beam of these nanotubes has been studied in two extreme cases of nitrogen incorporation content and configuration. These findings provide key information for the applications of these nanostructures.Comment: 25 pages, 13 figure

ICTV virus taxonomy profile: Bromoviridae

Bromoviridae is a family of plant viruses with tri-segmented, positive-sense, single-stranded RNA genomes of about 8 kb in total. Genomic RNAs are packaged in separate virions that may also contain subgenomic, defective or satellite RNAs. Virions are variable in morphology (spherical or bacilliform) and are transmitted between hosts mechanically, in/on the pollen and non-persistently by insect vectors. Members of the family are responsible for major disease epidemics in fruit, vegetable and fodder crops such as tomato, cucurbits, bananas, fruit trees and alfalfa. This is a summary of the International Committee on Taxonomy of Viruses (ICTV) Report on the family Bromoviridae, which is available at www.ictv.global/report/bromoviridae

Systematic study of Oxygen vacancy tunable transport properties of few-layer MoO3- x enabled by vapor-based synthesis

Bulk and nanoscale molybdenum trioxide (MoO3) has shown impressive technologically relevant properties, but deeper investigation into 2D MoO3 has been prevented by the lack of reliable vapor-based synthesis and doping techniques. Herein, the successful synthesis of high-quality, few-layer MoO3 down to bilayer thickness via physical vapor deposition is reported. The electronic structure of MoO3 can be strongly modified by introducing oxygen substoichiometry (MoO3- x), which introduces gap states and increases conductivity. A dose-controlled electron irradiation technique to introduce oxygen vacancies into the few-layer MoO3 structure is presented, thereby adding n-type doping. By combining in situ transport with core-loss and monochromated low-loss scanning transmission electron microscopy–electron energy-loss spectroscopy studies, a detailed structure–property relationship is developed between Mo-oxidation state and resistance. Transport properties are reported for MoO3- x down to three layers thick, the most 2D-like MoO3- x transport hitherto reported. Combining these results with density functional theory calculations, a radiolysis-based mechanism for the irradiation-induced oxygen vacancy introduction is developed, including insights into favorable configurations of oxygen defects. These systematic studies represent an important step forward in bringing few-layer MoO3 and MoO3- x into the 2D family, as well as highlight the promise of MoO3- x as a functional, tunable electronic material

Optical Transitions in Single-Wall Boron Nitride Nanotubes

Optical transitions in single-wall boron nitride nanotubes are investigated by means of optical absorption spectroscopy. Three absorption lines are observed. Two of them (at 4.45 and 5.5 eV) result from the quantification involved by the rolling up of the hexagonal boron nitride (h-BN) sheet. The nature of these lines is discussed, and two interpretations are proposed. A comparison with single-wall carbon nanotubes leads one to interpret these lines as transitions between pairs of van Hove singularities in the one-dimensional density of states of boron nitride single-wall nanotubes. But the confinement energy due to the rolling up of the h-BN sheet cannot explain a gap width of the boron nitride nanotubes below the h-BN gap. The low energy line is then attributed to the existence of a Frenkel exciton with a binding energy in the 1 eV range

Comparison of Electrogram Organization and Synchronization Indices in Atrial Fibrillation: a Simulation Study

Abstract In this work, a comparative study of several electrogram (EGM) organization and synchronization indices in atrial fibrillation (AF) has been performed. To do this, a realistic EGM simulator has been designed. In order to see how the indices are affected by noise and local activation time and conduction variability, the signal-to-noise ratio (SNR), the delay between leads and its variability Introduction Atrial fibrillation (AF) is a type of cardiac arrhythmia due to electrical re-entry in the atria. As a result, there is no uniform atrial contraction, inadequate blood pumping from atrium to ventricle and erratic and fast ventricular rate. It is the most common arrhythmia To reverse AF to sinus rhythm, electrical and pharmacological cardioversion are used. If this does not work, radiofrequency ablation is performed (to burn atrial zones in order to avoid electrical re-entry by means of cardiac catheterization). Ablation methods were proposed and are currently under investigation The main goal of this work is to perform a comparative study of EGM organization and synchronization indices in AF. For that purpose, an EGM simulator based on real EGM has been designed to study the effect of noise and variability in the activation delays. Methods Simulation setup We selected a 2-min real EGM lead recorded during AF at a sampling frequency of 977 Hz as the basis for the simulations, and generated delayed versions by shifting the record with specific delays (∆∈{10;85}ms, every 10ms). Activation times of the original EGM were automatically detected with the method explained later. Additional variability in the activation times is simulated by advancing or delaying each activation with independent random shifts with zero mean and standard deviations σ (1, 2, 5, 8, 10, 15, 20, 25 and 30 ms, as well 0 ms, no additional variability). This allows us to gradually simulate disorganization in single EGM, and loss in the synchronization between pairs of EGMs. Finally, Gaussian noise is added to the simulated EGMs, so that a given signal-to-noise ratio (SNR) is obtained. Simulated SNR ranged from -10dB to 30dB, every 5dB. For each combination of values, 50 realizations were simulated. EGM preprocessing Filtering: First, we applied a band-pass linear filter (40-250 Hz passband) to attenuate both slow deflections and high frequency noise. The filtered signal was rectified (which makes most energy go to low frequencies), and finally, a linear low-pass filter (with 20 Hz cut-off frequency) was applied. After this preprocessing, the filtered signal shows a positive pulse for each activation Activation detection: it is based on finding positive peaks in the filtered signal, greater than an adaptive threshold proportional to the average amplitude of the last activation

Radial collapse of carbon nanotubes for conductivity optimized polymer composites

The optimization of the electronic conduction of carbon nanotube polymer composites is studied by tuning the radial geometry of the carbon nanotubes in a compression cycle. We have investigated the structural evolution of multi-walled carbon nanotubes in a polyamide matrix as a function of applied high pressure. Combining high resolution electron microscopy and small angle neutron scattering experiments, we conclude that the nanotube radial cross-section is irreversibly deformed following applied pressures up to 5 GPa. Studying highly percolated composites we observe that the sample resistivity drastically decreases with pressure up to about 2 GPa with no further change up to the maximum 5 GPa applied pressure. An important hysteresis is observed upon decompression which leads to an enhanced electrical conductivity of the composite in all the studied compression cycles with maximum pressures ranging from 1 to 5 GPa. Modelling the radial collapse of single-walled carbon nanotubes shows that the modified radial geometry can considerably improve the electronic transport properties in contacted carbon nanotube junctions. Our results open opportunities for engineering nanotube composites by controlling the radial collapse