Electric field tunable superconductor-semiconductor coupling in Majorana nanowires

We study the effect of external electric fields on superconductor-semiconductor coupling by measuring the electron transport in InSb semiconductor nanowires coupled to an epitaxially grown Al superconductor. We find that the gate voltage induced electric fields can greatly modify the coupling strength, which has consequences for the proximity induced superconducting gap, effective g-factor, and spin-orbit coupling, which all play a key role in understanding Majorana physics. We further show that level repulsion due to spin-orbit coupling in a finite size system can lead to seemingly stable zero bias conductance peaks, which mimic the behavior of Majorana zero modes. Our results improve the understanding of realistic Majorana nanowire systems.Comment: 10 pages, 5 figures, supplemental information as ancillary fil

Quantized Majorana conductance

Majorana zero-modes hold great promise for topological quantum computing. Tunnelling spectroscopy in electrical transport is the primary tool to identify the presence of Majorana zero-modes, for instance as a zero-bias peak (ZBP) in differential-conductance. The Majorana ZBP-height is predicted to be quantized at the universal conductance value of 2e2/h at zero temperature. Interestingly, this quantization is a direct consequence of the famous Majorana symmetry, 'particle equals antiparticle'. The Majorana symmetry protects the quantization against disorder, interactions, and variations in the tunnel coupling. Previous experiments, however, have shown ZBPs much smaller than 2e2/h, with a recent observation of a peak-height close to 2e2/h. Here, we report a quantized conductance plateau at 2e2/h in the zero-bias conductance measured in InSb semiconductor nanowires covered with an Al superconducting shell. Our ZBP-height remains constant despite changing parameters such as the magnetic field and tunnel coupling, i.e. a quantized conductance plateau. We distinguish this quantized Majorana peak from possible non-Majorana origins, by investigating its robustness on electric and magnetic fields as well as its temperature dependence. The observation of a quantized conductance plateau strongly supports the existence of non-Abelian Majorana zero-modes in the system, consequently paving the way for future braiding experiments.Comment: 5 figure

Not a melting pot: Plant species aggregate in their non-native range

Aim: Plant species continue to be moved outside of their native range by human activities. Here, we aim to determine whether, once introduced, plants assimilate into native communities or whether they aggregate, thus forming mosaics of native- and alien-rich communities. Alien species might aggregate in their non-native range owing to shared habitat preferences, such as their tendency to establish in high-biomass, species-poor areas. Location: Twenty-two herbaceous grasslands in 14 countries, mainly in the temperate zone. Time period: 2012–2016. Major taxa studied: Plants. Methods: We used a globally coordinated survey. Within this survey, we found 46 plant species, predominantly from Eurasia, for which we had co-occurrence data in their native and non-native ranges. We tested for differences in co-occurrence patterns of 46 species between their native (home) and non-native (away) range. We also tested whether species had similar habitat preferences, by testing for differences in total biomass and species richness of the patches that species occupy in their native and non-native ranges. Results: We found the same species to show different patterns of association depending on whether they were in their native or non-native range. Alien species were negatively associated with native species; instead, they aggregated with other alien species in species-poor, high-biomass communities in their non-native range compared with their native range. Main conclusions: The strong differences between the native (home) and non-native (away) range in species co-occurrence patterns are evidence that the way in which species associate with resident communities in their non-native range is not species dependent, but is instead a property of being away from their native range. These results thus highlight that species might undergo important ecological changes when introduced away from their native range. Overall, we show origin-dependent associations that result in novel communities, in which alien-rich patches exist within a mosaic of native-dominated communities

MONITORING THE EFFECT OF SOME INSECTICIDES FOR CORN STEM BORER CONTROL, AT DEIR EZ-ZOR REGION, SYRIA

The corn stem borers larvae (species Sesamia cretica Led., Sesamia nonagrioides Lef. and Os-trinia nubilalis (Hübner)) are considered the major pests attacking Zea mays L. The larvae bore into stems and ears which cause a significant decrease of both quantity and quality of yield. This research was completed at Eastern region of Syria during 2004 and 2005 corn growing season, aiming to control these corn borer species with some insec-ticides; Avaunt 150SC (Indoxacarb 150 g / L),Sumialpha 5EC (Esfenvalerate 50 g / L), Proclaim 05SG (Emamectin benzoate 50 g / Kg), Comply 25WP (Fenoxycarb 205 g / Kg) and Agerin 6.5WP (Bacillus thuringiensis kurstaki 32000 IU / Mg). The results showed that in corn attacked by Sesa-mia cretica, Sesamia nonagrioides and Ostrinia nubilalis the infested rate reached up to 38 % on stems and 18.5 % on ears at control plots. Results also showed high efficacy of insecticides Avaunt 150SC, Sumialpha 5EC, Proclaim 05SG, Comply 25WP and Agerin 6.5WP in reducing the infested rate in stems to about 6, 8.1, 11.5, 13.5 and 21.2 %, respectively. And to about 4.5, 6.1, 7.2, 7.9 and 11.1 % in ears by Avaunt 150SC, Sumialpha 5EC, Proclaim 05SG, Comply 25WP and Agerin 6.5WP, respectively. These results gave rise to a positive increase in the yield of corn seeds

Ants visible from space influence soil propertes and vegetaton in steppe rangelands of Iran

Messor nests in Iranian steppe rangelands can be so large that they are visible from space. When compared with reference soils, nest soil is higher in nutrients and lower in pH. Ant nests also homogenise the nutrients throughout the upper soil profile, although this effect diminished when nests are abandoned. The denuded circles around nests are surrounded by rings of vegetaton that differ in species compositon from that of the surrounding vegetaton, while abandoned nests are colonized by a different range of plant species. Data on the density and abundance of Messor cf. intermedius nests indicate that the soil in less than 1% of the area is impacted, although the cumulatve effect of so many nests influences the plant species and vegetaton structure of the region. The data indicate the importance of these ants in altering soil chemical compositon and plant diversity, which could have flow-on effects to the diversity of animals

The Effects of Altitude on Productivity and Formative Components of Essential Oils of Artemisia absinthium L. (Iran)

ABSTRACT Productivity and growth of plants in terrestrial ecosystems and natural habitats influence by different factors such as the altitude from sea level. Common wormwood (Artemisia absinthium L.) species belongs to the level is respectively 0.96±0.007%, 0.91±0.007%, and 0.94±0.007% so that the highest percentage is for first level and the least one is for second level. Generally, 54 components were found in three altitude levels that elements of Sabinene, Germacrene D