198 research outputs found
Modification of various metals by volume discharge in air atmosphere
The results of the modification of stainless steel, niobium and titanium by volume discharge induced by a beam of runaway electrons in air under normal pressure are presented. Changes in the chemical composition of the surface layers of metal by the action of the discharge, structural changes and changes of hardness were studied. It has been found that the concentration of oxygen and carbon in the surface layers of the samples depend on the number of discharge pulses. The aim of this work is to find possible application of this type of discharge in science and industrial production
Absence of quantum-confined Stark effect in GaN quantum disks embedded in (Al,Ga)N nanowires grown by molecular beam epitaxy
Several of the key issues of planar (Al,Ga)N-based deep-ultraviolet light
emitting diodes could potentially be overcome by utilizing nanowire
heterostructures, exhibiting high structural perfection and improved light
extraction. Here, we study the spontaneous emission of GaN/(Al,Ga)N nanowire
ensembles grown on Si(111) by plasma-assisted molecular beam epitaxy. The
nanowires contain single GaN quantum disks embedded in long (Al,Ga)N nanowire
segments essential for efficient light extraction. These quantum disks are
found to exhibit intense emission at unexpectedly high energies, namely,
significantly above the GaN bandgap, and almost independent of the disk
thickness. An in-depth investigation of the actual structure and composition of
the nanowires reveals a spontaneously formed Al gradient both along and across
the nanowire, resulting in a complex core/shell structure with an Al deficient
core and an Al rich shell with continuously varying Al content along the entire
length of the (Al,Ga)N segment. This compositional change along the nanowire
growth axis induces a polarization doping of the shell that results in a
degenerate electron gas in the disk, thus screening the built-in electric
fields. The high carrier density not only results in the unexpectedly high
transition energies, but also in radiative lifetimes depending only weakly on
temperature, leading to a comparatively high internal quantum efficiency of the
GaN quantum disks up to room temperature.Comment: This document is the unedited Author's version of a Submitted Work
that was subsequently accepted for publication in Nano Letters (2019),
copyright (C) American Chemical Society after peer review. To access the
final edited and published work see
https://doi.org/10.1021/acs.nanolett.9b01521, the supporting information is
available (free of charge) under the same lin
Fungal Planet Description Sheets: 1112–1181
Novel species of fungi described in this study include those from various countries as follows: Australia, Austroboletus asper on soil, Cylindromonium alloxyli on leaves of Alloxylon pinnatum, Davidhawksworthia quintiniae on leaves of Quintinia sieberi, Exophiala prostantherae on leaves of Prostanthera sp., Lactifluus lactiglaucus on soil, Linteromyces quintiniae (incl. Linteromyces gen. nov.) on leaves of Quintinia sieberi, Lophotrichus medusoides from stem tissue of Citrus garrawayi, Mycena pulchra on soil, Neocalonectria tristaniopsidis (incl. Neocalonectria gen. nov.) and Xyladictyochaeta tristaniopsidis on leaves of Tristaniopsis collina, Parasarocladium tasmanniae on leaves of Tasmannia insipida, Phytophthora aquae-cooljarloo from pond water, Serendipita whamiae as endophyte from roots of Eriochilus cucullatus, Veloboletus limbatus (incl. Veloboletus gen. nov.) on soil. Austria, Cortinarius glaucoelotus on soil. Bulgaria, Suhomyces rilaensis from the gut of Bolitophagus interruptus found on a Polyporus sp. Canada, Cantharellus betularum among leaf litter of Betula, Penicillium saanichii from house dust. Chile, Circinella lampensis on soil, Exophiala embothrii from rhizosphere of Embothrium coccineum. China, Colletotrichum cycadis on leaves of Cycas revoluta. Croatia, Phialocephala melitaea on fallen branch of Pinus halepensis. Czech Republic, Geoglossum jirinae on soil, Pyrenochaetopsis rajhradensis from dead wood of Buxus sempervirens. Dominican Republic, Amanita domingensis on litter of deciduous wood, Melanoleuca dominicana on forest litter. France, Crinipellis nigrolamellata (Martinique) on leaves of Pisonia fragrans, Talaromyces pulveris from bore dust of Xestobium rufovillosum infesting floorboards. French Guiana, Hypoxylon hepaticolor on dead corticated branch. Great Britain, Inocybe ionolepis on soil. India, Cortinarius indopurpurascens among leaf litter of Quercus leucotrichophora. Iran, Pseudopyricularia javanii on infected leaves of Cyperus sp., Xenomonodictys iranica (incl. Xenomonodictys gen. nov.) on wood of Fagus orientalis. Italy, Penicillium vallebormidaense from compost. Namibia, Alternaria mirabibensis on plant litter, Curvularia moringae and Moringomyces phantasmae (incl. Moringomyces gen. nov.) on leaves and flowers of Moringa ovalifolia, Gobabebomyces vachelliae (incl. Gobabebomyces gen. nov.) on leaves of Vachellia erioloba, Preussia procaviae on dung of Procavia capensis. Pakistan, Russula shawarensis from soil on forest floor. Russia, Cyberlindnera dauci from Daucus carota. South Africa, Acremonium behniae on leaves of Behnia reticulata, Dothiora aloidendri and Hantamomyces aloidendri (incl. Hantamomyces gen. nov.) on leaves of Aloidendron dichotomum, Endoconidioma euphorbiae on leaves of Euphorbia mauritanica, Eucasphaeria proteae on leaves of Protea neriifolia , Exophiala mali from inner fruit tissue of Malus sp., Graminopassalora geissorhizae on leaves of Geissorhiza splendidissima, Neocamarosporium leipoldtiae on leaves of Leipoldtia schultzii, Neocladosporium osteospermi on leaf spots of Osteospermum moniliferum, Neometulocladosporiella seifertii on leaves of Combretum caffrum, Paramyrothecium pituitipietianum on stems of Grielum humifusum, Phytopythium paucipapillatum from roots of Vitis sp., Stemphylium carpobroti and Verrucocladosporium carpobroti on leaves of Carpobrotus quadrifolius, Suttonomyces cephalophylli on leaves of Cephalophyllum pilansii. Sweden, Coprinopsis rubra on cow dung, Elaphomyces nemoreus fromdeciduouswoodlands. Spain, Polyscytalum pini-canariensis on needles of Pinus canariensis, Pseudosubramaniomyces septatus from stream sediment, Tuber lusitanicum on soil under Quercus suber. Thailand, Tolypocladium flavonigrum on Elaphomyces sp. USA, Chaetothyrina spondiadis on fruits of Spondias mombin, Gymnascella minnisii from bat guano, Juncomyces patwiniorum on culms of Juncus effusus, Moelleriella puertoricoensis on scale insect, Neodothiora populina (incl. Neodothiora gen. nov.) on stem cankers of Populus tremuloides, Pseudogymnoascus palmeri fromcavesediment. Vietnam, Cyphellophora vietnamensis on leaf litter, Tylopilus subotsuensis on soil in montane evergreen broadleaf forest. Morphological and culture characteristics are supported by DNA barcodes
Polyphenole als Qualitätskriterium für die Beurteilung von Cistus incanus Tees und ihre antibakterielle Wirkung auf Streptococcus mutans
Heuristic Evaluation for Novice Programming Systems
The past few years has seen a proliferation of novice programming tools. The availability of a large number of systems has made it difficult for many users to choose among them. Even for education researchers, comparing the relative quality of these tools, or judging their respective suitability for a given context, is hard in many instances. For designers of such systems, assessing the respective quality of competing design decisions can be equally difficult.
Heuristic evaluation provides a practical method of assessing the quality of alternatives in these situations and of identifying potential problems with existing systems for a given target group or context. Existing sets of heuristics, however, are not specific to the domain of novice programming and thus do not evaluate all aspects of interest to us in this specialised application domain.
In this article, we propose a set of heuristics to be used in heuristic evaluations of novice programming systems. These heuristics have the potential to allow a useful assessment of the quality of a given system with lower cost than full formal user studies and greater precision than the use of existing sets of heuristics. The heuristics are described and discussed in detail. We present an evaluation of the effectiveness of the heuristics that suggests that the new set of heuristics provides additional useful information to designers not obtained with existing heuristics sets
Dispersion and Aging of Volcanic Aerosols After the La Soufrière Eruption in April 2021
Volcanic aerosols change the atmospheric composition and thereby affect weather and climate. Aerosol dynamic processes such as nucleation, condensation, and coagulation modify the shape, size, and mass of aerosol particles, which influence their atmospheric lifetime and radiative properties. Nevertheless, most models omit these processes for ash particles. In this work, we explore the ash aerosol aging and sulfate production during the first 4 days following the 2021 La Soufrière (St. Vincent) eruption with the ICON-ART model (ICOsahedral Nonhydrostatic model with Aerosol and Reactive Trace gases). Online coupling of ICON-ART with a one-dimensional volcanic plume model calculates volcanic emission, which makes it possible to resolve the different eruption phases of the noncontinuous La Soufrière eruption. We compared our simulated aerosol distribution and composition with observations from the Cloud-Aerosol Lidar with Orthogonal Polarization (CALIOP) instrument, the Multiangle Imaging SpectroRadiometer (MISR) Research Aerosol (RA) Algorithm, and the Barbados Cloud Observatory (BCO). We show that online coupling is essential to adequately model the emissions and plume development close to the volcano. The modeled aerosol aging is in very good agreement with observations from MISR near the emission source and with CALIOP at larger distances. Furthermore, particle aging occurs faster in the troposphere than in the stratosphere due to the availability of water vapor and OH, but a layer of coated ash appears at the plume top due to faster oxidation of SO and lofting by aerosol-radiation interaction. This paper gives the first direct comparison of aerosol aging in volcanic eruption plumes between simulations and observations
Massively-parallelized production of femtoliter droplets and its application to self-assembled nanoparticle clusters for novel metamaterials
Hard superconducting gap and diffusion-induced superconductors in Ge-Si nanowires
We show a hard induced superconducting gap in a Ge-Si nanowire Josephson
transistor up to in-plane magnetic fields of mT, an important step
towards creating and detecting Majorana zero modes in this system. A hard
induced gap requires a highly homogeneous tunneling heterointerface between the
superconducting contacts and the semiconducting nanowire. This is realized by
annealing devices at C during which aluminium inter-diffuses and
replaces the germanium in a section of the nanowire. Next to Al, we find a
superconductor with lower critical temperature ( K) and a
higher critical field ( T). We can therefore selectively
switch either superconductor to the normal state by tuning the temperature and
the magnetic field and observe that the additional superconductor induces a
proximity supercurrent in the semiconducting part of the nanowire even when the
Al is in the normal state. In another device where the diffusion of Al rendered
the nanowire completely metallic, a superconductor with a much higher critical
temperature ( K) and critical field ( T) is
found. The small size of diffusion-induced superconductors inside nanowires may
be of special interest for applications requiring high magnetic fields in
arbitrary direction
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