Conductance fluctuations in metallic nanogaps made by electromigration

We report on low temperature conductance measurements of gold nanogaps fabricated by controlled electromigration. Fluctuations of the conductance due to quantum interferences and depending both on bias voltage and magnetic field are observed. By analyzing the voltage and magnetoconductance correlation functions we determine the type of electron trajectories generating the observed quantum interferences and the effective characteristic time of phase coherence in our device.Comment: 5 pages, 4 figures, to appear in J. Appl. Phy

Metallic single-electron transistor without traditional tunnel barriers

We report on a new type of single-electron transistor (SET) comprising two highly resistive Cr thin-film strips (~ 1um long) connecting a 1 um-long Al island to two Al outer electrodes. These resistors replace small-area oxide tunnel junctions of traditional SETs. Our transistor with a total asymptotic resistance of 110 kOhm showed a very sharp Coulomb blockade and reproducible, deep and strictly e-periodic gate modulation in wide ranges of bias currents I and gate voltages V_g. In the Coulomb blockade region (|V| < 0.5 mV), we observed a strong suppression of the cotunneling current allowing appreciable modulation curves V-V_g to be measured at currents I as low as 100 fA. The noise figure of our SET was found to be similar to that of typical Al/AlOx/Al single-electron transistors.Comment: 5 pages incl. 4 fig

Effect of elevated CO2 and high temperature on seed-set and grain quality of rice

Hybrid vigour may help overcome the negative effects of climate change in rice. A popular rice hybrid (IR75217H), a heat-tolerant check (N22), and a mega-variety (IR64) were tested for tolerance of seed-set and grain quality to high-temperature stress at anthesis at ambient and elevated [CO2]. Under an ambient air temperature of 29 °C (tissue temperature 28.3 °C), elevated [CO2] increased vegetative and reproductive growth, including seed yield in all three genotypes. Seed-set was reduced by high temperature in all three genotypes, with the hybrid and IR64 equally affected and twice as sensitive as the tolerant cultivar N22. No interaction occurred between temperature and [CO2] for seed-set. The hybrid had significantly more anthesed spikelets at all temperatures than IR64 and at 29 °C this resulted in a large yield advantage. At 35 °C (tissue temperature 32.9 °C) the hybrid had a higher seed yield than IR64 due to the higher spikelet number, but at 38 °C (tissue temperature 34–35 °C) there was no yield advantage. Grain gel consistency in the hybrid and IR64 was reduced by high temperatures only at elevated [CO2], while the percentage of broken grains increased from 10% at 29 °C to 35% at 38 °C in the hybrid. It is concluded that seed-set of hybrids is susceptible to short episodes of high temperature during anthesis, but that at intermediate tissue temperatures of 32.9 °C higher spikelet number (yield potential) of the hybrid can compensate to some extent. If the heat tolerance from N22 or other tolerant donors could be transferred into hybrids, yield could be maintained under the higher temperatures predicted with climate change

Effect of Species Horizontal Distribution on Defoliation of Ryegrass-Clover Swards Grazed by Sheep

Defoliation events on labelled white clover (Trifolium repens) growing points or ryegrass (Lolium perenne) tillers were measured during grazing tests by sheep with swards consisting of mixed ryegrass-clover (MIX) or alternate strips of clover and ryegrass (STRIP). Sward surface height was maintained at 6.4 cm by lawnmower cuts in order to obtain a similar surface height for both species. On average, during 13 grazing tests in STRIP and 11 in MIX swards, clover was the more defoliated species : 23.3% of the growing points in STRIP and 26.5% in MIX swards were defoliated compared to 16.2% and 12.5% of the tillers. No difference of clover defoliation probability occurred between STRIP and MIX swards, nor between clover growing points in different neighbourhoods in STRIP sward, indicating that the horizontal distribution of clover does not affect its pattern of defoliation by sheep

Multi-scale building maps from aerial imagery

Nowadays, the extraction of buildings from aerial imagery is mainly done through deep convolutional neural networks (DCNNs). Buildings are predicted as binary pixel masks and then regularized to polygons. Restricted by nearby occlusions (such as trees), building eaves, and sometimes imperfect imagery data, these results can hardly be used to generate detailed building footprints comparable to authoritative data. Therefore, most products can only be used for mapping at smaller map scale. The level of detail that should be retained is normally determined by the scale parameter in the regularization algorithm. However, this scale information has been already defined in cartography. From existing maps of different scales, neural network can be used to learn such scale information implicitly. The network can perform generalization directly on the mask output and generate multi-scale building maps at once. In this work, a pipeline method is proposed, which can generate multi-scale building maps from aerial imagery directly. We used a land cover classification model to provide the building blobs. With the models pre-trained for cartographic building generalization, blobs were generalized to three target map scales, 1:10,000, 1:15,000, and 1:25,000. After post-processing with vectorization and regularization, multi-scale building maps were generated and then compared with existing authoritative building data qualitatively and quantitatively. In addition, change detection was performed and suggestions for unmapped buildings could be provided at a desired map scale. . © 2020 International Archives of the Photogrammetry, Remote Sensing and Spatial Information Sciences - ISPRS Archives

Effect of Level Statistics on Superconductivity in Ultrasmall Metallic Grains

We examine the destruction of superconducting pairing in metallic grains as their size is decreased for both even and odd numbers of electrons. This occurs when the average level spacing d is of the same order as the BCS order parameter. The energy levels of these grains are randomly distributed according to random matrix theory, and we must work statistically. We find that the average value of the critical level spacing is larger than for the model of equally spaced levels for both parities, and derive numerically the probabilities $P_{o,e}(d)$ that a grain of mean level spacing d shows pairing.Comment: 12 pages, 2 PostScript files, RevTex format, submitted to PR