1,183 research outputs found
Atmospheric transport of sulphur compound pollutants
Imperial Users onl
Influence of structural disorder and large-scale geometric fluctuations on the Coherent Transport of Metallic Junctions and Molecular Wires
Structural disorder is present in almost all experimental measurements of
electronic transport through single molecules or molecular wires. To assess its
influence on the conductance is computationally demanding, because a large
number of conformations must be considered. Here we analyze an approximate
recursive layer Green function approach for the ballistic transport through
quasi one-dimensional nano-junctions. We find a rapid convergence of the method
with its control parameter, the layer thickness, and good agreement with
existing experimental and theoretical data. Because the computational effort
rises only linearly with system size, this method permits treatment of very
large systems. We investigate the conductance of gold- and silver wires of
different sizes and conformations. For weak electrode disorder and imperfect
coupling between electrode and wire we find conductance variations of
approximately 20%. Overall we find the conductance of silver junctions well
described by the immediate vicinity of narrowest point in the junction, a
result that may explain the observation of well-conserved conductance plateaus
in recent experiments on silver junctions. In an application to flexible
oligophene wires, we find that strongly distorted conformations that are
sterically forbidden at zero temperature, contribute significantly to the
observed average zero-bias conductance of the molecular wire
Oceanographic observation of New York Bight from ERTS-1
The author has identified the following significant events. The Earth Resources Technology Satellite made a transit over New York Bight on 16 August, 1972. Imagery from this transit shows several oceanographic features that demonstrate the usefulness of remote sensing for large area, synoptic observation of changes in water quality in the coastal zone. Both the extent and turbulent character of the Hudson River plume are discernible in the image. Residue from a dump of waste acid is visible over a five mile area in the apex of the Bight. Little dispersion of this residue has occurred which suggests that this feature will be a persistent signature in images from future satellite transits
An Experiment to Evaluate Skylab Earth Resources Sensors for Detection of the Gulf Stream
The author has identified the following significant results. An experiment to evaluate the Skylab earth resources package for observing ocean currents was performed in the Straits of Florida in January 1974. Data from the S190 photographic facility, S191 spectroradiometer and S192 multispectral scanner, were compared with surface observations. The anticyclonic edge of the Gulf Stream could be identified in the Skylab S190A and B photographs, but the cyclonic edge was obscured by clouds. The aircraft photographs were judged not useful for spectral analysis because vignetting caused the blue/green ratios to be dependent on the position in the photograph. The spectral measurement technique could not identify the anticyclonic front, but mass of Florida Bay water which was in the process of flowing into the Straits could be identified and classified. Monte Carlo simulations of the visible spectrum showed that the aerosol concentration could be estimated and a correction technique was devised
Study and parentage analysis of old Albanian grapevine cultivars by ampelography and microsatellite markers
The number of old grapevine cultivars in Albania, originated in the country or introduced over many centuries and adapted to the conditions of the country, is huge. Because numerous cases of homonymy and synonymy exist, the interest for variety recognition is high. Investigation of these cultivars aptitudes is related to identification of desired characteristics and their utilization. In the framework of COST Action FA1003, trueness to type assessment of 13 old Albanian cultivars was undertaken including morphologic description and genetic fingerprinting. Parentage relationships were studied as well. The selected cultivars are of interest for their antiquity, for high production and distinctive organoleptic features. The ampelographic study of these cultivars supported confirmation of the results obtained by genetic profile comparison with seven SSR-marker databases and the European Vitis Database. In summary 12 unique genotypes, four parent-offspring relationships and one full parentage were found
The "missing link" 'Blaue Zimmettraube' reveals that 'Blauer Portugieser' and 'BlaufrÀnkisch' originated in Lower Styria
Parent offspring analysis already revealed genetic relationships for 'Blauer Portugieser' and 'BlaufrĂ€nkisch', sharing at each locus one allele with 'GrĂŒner Silvaner' and 'Weisser Heunisch', respectively. The missing second progenitor of 'Blauer Portugieser' and 'BlaufrĂ€nkisch' is a recently rediscovered black grapevine, called 'Blaue Zimmettraube'. It was found in the largest German wine growing area Rheinhessen. The same cultivar was detected as a single vine in Friuli, Italy and named SbulzĂŹna. The 'Blaue Zimmettraube', bearing female flowers, and thus the female parent in the crosses, was cultivated in the 19th century in Lower Styria together with 'GrĂŒner Silvaner' and 'Weisser Heunisch'. Because the 'Blaue Zimmettraube' did not exist in Austria and red wine production was fairly rare in that country before 1800, it is suspected that the cradle of 'Blauer Portugieser' and 'BlaufrĂ€nkisch' is in Lower Styria. Furthermore, according to chlorotype analysis, it turned out that 'Blauer GĂ€nsfĂŒsser' is the male parent of 'Blaue Zimmettraube' and thus the 'Blaue Zimmettraube' represents a veritable "missing link". To prove the genetic relationships the nine GrapeGen06-markers and additional forty microsatellite markers were applied. Likelihood analysis with allele frequencies of 22 SSR-markers from 772 cultivars revealed a very high degree of probability that the proposed parents are consistent, due to rare alleles inherited from 'Blaue Zimmettraube'. To investigate on the geographical origin of 'Blauer Portugieser' and 'BlaufrĂ€nkisch' historical Austrian and Styrian references were consulted
The prolific grape variety (Vitis vinifera L.) âHeunisch Weissâ (= âGouais blancâ): bud mutants, âcoloredâ homonyms and further offspring
âHeunisch Weissâ (syn. âGouais blancâ) contributed to a considerable increase of our varietal assortment, including renowned varieties like âChardonnayâ and âRiesling Weissâ. Three phenotypic variants of âHeunisch Weissâ were discovered in the grapevine collection at the JKI Institute for Grapevine Breeding Geilweilerhof: (a) âHeunisch Dreifarbigâ (three coloured âHeunischâ; VIVC prime name âHeunisch Dreifarbigâ) expressing intense anthocyanin coloration on shoots, inflorescences and leaf petioles before fruit set and even red berry skin at fruit set stage; (b) âPekasoreâ (VIVC prime name âHeunisch Rotgestreiftâ; red striped âHeunischâ;) with rose to red stripes on white berries and (c) the stenospermocarpic âAspirantâ (VIVC prime name âHeunisch Weiss Seedlessâ). Four cultivars proving to be homonymous in relation to âHeunischâ were investigated at 24 loci to determine their identity or relatedness to âHeunisch Weissâ, respectively. âHeunisch Schwarzâ turned out to be a âHeunisch Weissâ offspring. No parent offspring relationship was detected for âHeunisch Rotâ, âHaenisch Rotâ = âPamidâ, and âHeunisch Blauâ . Ampelographic description was carried out for some of the accessions to trace back historical evidences. In addition five new âHeunisch Weissâ offsprings were identified and confirmed by analysing 35 nuclear microsatellite loci. The accession âFurmint Apirenâ turned out to be a seedless bud mutant of the âHeunisch Weissâ offspring âIordanâ
Pre-selectable integer quantum conductance of electrochemically fabricated silver point contacts
The controlled fabrication of well-ordered atomic-scale metallic contacts is
of great interest: it is expected that the experimentally observed high
percentage of point contacts with a conductance at non-integer multiples of the
conductance quantum G_0 = 2e^2/h in simple metals is correlated to defects
resulting from the fabrication process. Here we demonstrate a combined
electrochemical deposition and annealing method which allows the controlled
fabrication of point contacts with pre-selectable integer quantum conductance.
The resulting conductance measurements on silver point contacts are compared
with tight-binding-like conductance calculations of modeled idealized junction
geometries between two silver crystals with a predefined number of contact
atoms
Assessing Thermochemical Properties of Materials through Ab initio Quantum-mechanical Methods: The Case of α-Al2O3
The thermochemical behavior of α-Al2O3 corundum in the whole temperature range 0â2317 K (melting point) and under pressures up to 12 GPa is predicted by applying ab initio methods based on the density functional theory (DFT), the use of a local basis set and periodic-boundary conditions. Thermodynamic properties are treated both within and beyond the harmonic approximation to the lattice potential. In particular, a recent implementation of the quasi-harmonic approximation, in the Crystal program, is here shown to provide a reliable description of the thermal expansion coefficient, entropy, constant-volume and constant-pressure specific heats, and temperature dependence of the bulk modulus, nearly up to the corundum melting temperature. This is a remarkable outcome suggesting α-Al2O3 to be an almost perfect quasi-harmonic crystal. The effect of using different computational parameters and DFT functionals belonging to different levels of approximations on the accuracy of the thermal properties is tested, providing a reference for further studies involving alumina polymorphs and, more generally, quasi-ionic minerals
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