Spin-polarized Majorana zero modes in proximitized superconducting penta-silicene nanoribbons.

We theoretically propose penta-silicene nanoribbons (p-SiNRs) with induced p-wave superconductivity as a platform for the emergence of spin-polarized Majorana zero-modes (MZMs). The model explicitly considers the key ingredients of well-known Majorana hybrid nanowire setups: Rashba spin-orbit coupling, magnetic field perpendicular to the nanoribbon plane, and first nearest neighbor hopping with p-wave superconducting pairing. The energy spectrum of the system, as a function of chemical potential, reveals the existence of MZMs with a well-defined spin orientation localized at the opposite ends of both the top and bottom chains of the p-SiNR, associated with well-localized and nonoverlapping wave function profiles. Well-established experimental techniques enable the fabrication of highly ordered p-SiNRs, complemented by a thin lead film on top, responsible for inducing p-wave superconductivity through proximity effect. Moreover, the emergence of MZMs with explicit opposite spin orientations for some set of model parameters opens a new avenue for exploring quantum computing operations, which accounts for both MZMs and spin properties, as well as for new MZMs probe devices based on spin-polarized electronic transport mechanisms.

Growth and structural properties of silicene at multilayer coverage.

At monolayer coverage, silicene on Ag(1 1 1) may present different structural phases depending on the growth conditions. At multilayer coverage, only one structural phase has been reported: the [Formula: see text] phase. However, no link between the structural arrangement of the monolayer and that of the multilayer has been addressed. In this paper, reporting experimental work based on low-energy electron diffraction and scanning tunneling microscopy, we focus on the structural aspects of a multilayer film of silicene. We demonstrate that it exhibits one structural arrangement, namely the [Formula: see text] form, but with different domain orientations resulting from the structural properties of the initial wetting monolayer.

Presence of gapped silicene-derived band in the prototypical (3 × 3) silicene phase on silver (111) surfaces.

By mapping the low-energy electronic dynamics using angle resolved photoemission spectroscopy (ARPES), we have shed light on essential electronic characteristics of the (3 × 3) silicene phase on Ag(111) surfaces. In particular, our results show a silicene-derived band with a clear gap and linear energy-momentum dispersion near the Fermi level at the Γ symmetry point of the (3 × 3) phase at several distinctive Brillouin zones. Moreover, we have confirmed that the large buckling of ~0.7 Å of this silicene structure induces the opening of a gap close to the Fermi level higher than at least 0.3 eV, in agreement with recent reported photoemission results. The two-dimensional character of the charge carriers has also been revealed by the photon energy invariance of the gapped silicene band, suggesting a limited silicene-silver hybridization, in disagreement with recent density-functional theory (DFT) predictions.

Comparative structural and electronic studies of hydrogen interaction with isolated versus ordered silicon nanoribbons grown on Ag(110).

We have investigated the geometry and electronic structure of two different types of self-aligned silicon nanoribbons (SiNRs), forming either isolated SiNRs or a self-assembled 5 × 2/5 × 4 grating on an Ag(110) substrate, by scanning tunnelling microscopy and high resolution x-ray photoelectron spectroscopy. At room temperature we further adsorb on these SiNRs either atomic or molecular hydrogen. The hydrogen absorption process and hydrogenation mechanism are similar for isolated or 5 × 2/5 × 4 ordered SiNRs and are not site selective; the main difference arises from the fact that the isolated SiNRs are more easily attacked and destroyed faster. In fact, atomic hydrogen strongly interacts with any Si atoms, modifying their structural and electronic properties, while molecular hydrogen has first to dissociate. Hydrogen finally etches the Si nanoribbons and their complete removal from the Ag(110) surface could eventually be expected.

Reduced genetic diversity, increased isolation and multiple introductions of invasive giant hogweed in the western Swiss Alps.

The giant hogweed (Heracleum mantegazzianum) has successfully invaded 19 European countries as well as parts of North America. It has become a problematic species due to its ability to displace native flora and to cause public health hazards. Applying population genetics to species invasion can help reconstruct invasion history and may promote more efficient management practice. We thus analysed levels of genetic variation and population genetic structure of H. mantegazzianum in an invaded area of the western Swiss Alps as well as in its native range (the Caucasus), using eight nuclear microsatellite loci together with plastid DNA markers and sequences. On both nuclear and plastid genomes, native populations exhibited significantly higher levels of genetic diversity compared to invasive populations, confirming an important founder event during the invasion process. Invasive populations were also significantly more differentiated than native populations. Bayesian clustering analysis identified five clusters in the native range that corresponded to geographically and ecologically separated groups. In the invaded range, 10 clusters occurred. Unlike native populations, invasive clusters were characterized by a mosaic pattern in the landscape, possibly caused by anthropogenic dispersal of the species via roads and direct collection for ornamental purposes. Lastly, our analyses revealed four main divergent groups in the western Swiss Alps, likely as a consequence of multiple independent establishments of H. mantegazzianum.

Ordered phthalocyanine superstructures on Ag(110).

Organic-metal interfaces, in particular, self-assembling systems, are interesting in the field of molecular electronics. In this study, we have investigated the formation of the Ag(110)-iron phthalocyanine (FePc) interface in a coverage range of less than 1 and up to 2 ML using synchrotron based photoelectron spectroscopy and low energy electron diffraction. As-deposited FePc forms a densely packed first layer exhibiting a 3 x 2c(6 x 2) symmetry. Upon thermal treatment the order at the interface is modified depending on the initial FePc coverage, resulting in less densely packed but still ordered superstructures. The first monolayer is relatively strongly bound to the substrate, leading to the formation of an interface state just below the Fermi level. The highest occupied molecular orbital of FePc in the second layer is found at 1 eV higher binding energy compared to the interface state.

Germanium adsorption on Ag(111): an AES-LEED and STM study.

The adsorption of germanium on Ag(111) has been investigated using Scanning Tunneling Microscopy, Auger Electron Spectroscopy and Low Energy Electron Diffraction. From the shape of the Auger peak-to-peak versus time curves, we deduce that at room temperature the growth mode is nearly layer-by-layer at least for the first two layers. In the sub-monolayer range, the growth starts by the formation of a (mean square root of 3 x mean square root of 3)R30 degrees surface superstructure which is complete at 1/3 monolayer coverage. Beyond this coverage a rectangular c(mean square root of 3 x 7) superstructure is observed. STM images reveal that this last reconstruction is formed by an ordered arrangement of self-assembled Ge tetramers giving rise to a surprising undulation of the surface.

Computerized map of risk to manage wildlife species in urban areas.

For the last 20 years, human-wildlife conflicts have been rapidly increasing in towns. Although people want "greener" cities, the expansion of disliked species causes problems that are difficult to manage and to reduce. The complexity of the numerous factors involved in these human-wildlife relations needs the development of a comprehensive tool for urban planners. Today, with the development of computers and geographical information systems, it is easier to analyze and combine different spatial data as methods used for the management of risks in studies of natural hazards. Here we present a method for assessing and mapping the risk in cases of human-wildlife conflict. An application to starling management in a town in western France will show the efficiency of our methods to combine information given by a network of experts and to highlight higher risk sites. The map of risk provides a spatial result useful for comprehension, communication between people and agencies, and public education.

Panmictic structure of Helicobacter pylori demonstrated by the comparative study of six genetic markers.

We compared the classifications of strains obtained by analysis of several genetic markers to demonstrate the panmictic structure of Helicobacter pylori, previously suggested by the study of multilocus enzyme electrophoresis. A series of 39 strains, including 37 clinical isolates from patients with gastritis or ulcers from two regions of France, reference strain CIP 101260 and the Sydney strain (strain SSI), were used. They were studied by restriction fragment length polymorphism analysis of ribosomal DNA (ribotyping) using HindIII and HaeIII, by polymorphism analysis of the ureA-ureB and flaA genes by PCR-RFLP using HaeIII and MboI, by vacA genotyping and by the presence or absence of the cagA gene and of the insertion sequence IS605 detected by PCR. There was a high level of genetic polymorphism over the studied strains, with 38 ribotypes, 38 restriction profiles for the ureA-ureB gene, 19 restriction profiles for the flaA gene and five combinations of the signal and mid-region sequences of the vacA gene. Factorial analysis of correspondence and hierarchical clustering performed using each marker revealed that the different classifications of the strains were not correlated. This suggests there is much genetic recombination between strains and supports the hypothesis of a panmictic structure for the H. pylori species.

[Tick-transmitted arbovirus in Maghreb]. / Arbovirus transmis par des tiques au Maghreb.

The problem of arbovirus infections in Maghreb has been relatively neglected in the pst in spite of a rich diversity of biotopes, the presence of potential reservoirs and vectors, and their position on the flight path of the Palearctic-african bird migration systems, western branch. Moreover, West Nile virus has been isolated from southern Algeria since 1968. From 1979 to 1989, ticks were collected from wild birds, pigeons, bats, rodents, poultry, camels, wild boars, domestic mammals and man, and assayed for viruses. On the whole, 424 ticks were virologically studied from Morocco, 582 from Algeria and 601 from Tunisia. Four tick-borne arboviruses have been isolated so far: three from Morocco, Soldado (Nairovirus), Essaouria (Orbivirus) and Kala Iris (Orbivirus) from Ornithodoros (A.) maritimus ticks parasitizing marine birds, and one from Tunisia, Tunis (Phlebovirus), from Argas reflexus hermanni infesting domestic pigeons. Soldado virus may infect man working into colonies of gulls for ornithological or entomological purposes and this infection is associated with a self-limited febrile illness and pruritus. In addition, antibody to Essaouira virus was detected in a wild rodent in Morocco. On the contrary it is unlike that Tunis virus may infect man because A. r. hermanni is a strickly ornithophilic tick. However, Uukuniemi group antibody has been previously evidenced in wild rodents in Tunisia. Finally, it is not excluded that other, more pathogenic, arboviruses such as Congo-Crimean haemorrhagic fever might be accidentally introduced in this sensitive geographical area.

Tunis virus: a new Phlebovirus from Argas reflexus hermanni ticks in Tunisia.

A new Phlebovirus provisionally named Tunis virus has been isolated from Argas reflexus hermanni ticks parasitizing domestic pigeons. It is the first isolation of an arbovirus from Tunisia and the fourth tick-borne virus to be isolated from the Moghreb following Soldado, Essaouira and Kala Iris in Morocco. The pathogenic potential of this virus is briefly discussed according to the behaviour of its vector and previous serosurveys in the country.

Essaouira and Kala iris: two new orbiviruses of the Kemerovo serogroup, Chenuda complex, isolated from Ornithodoros (Alectorobius) maritimus ticks in Morocco.

Essaouira and Kala Iris viruses were isolated from Ornithodoros (Alectorobius) maritimus ticks parasitizing yellow-legged gulls (Larus cachinnans) on the coast of Morocco in 1979 and 1981, respectively. Serological evidence indicates that these two viruses are new members of the Chenuda complex within the Kemerovo serogroup of the genus Orbivirus. Ecological, pathological, morphological, and physicochemical properties are compatible with these findings. The infectivity of these viruses for man and animals, including seabirds, remains unknown.

New developments in the molecular epidemiology of adenovirus 8 keratoconjunctivitis.

Four consecutive epidemics of keratoconjunctivitis caused by adenovirus 8 (Ad8) occurred over a 5-year period in Brest, France. A selection of 30 strains isolated during this period was studied by DNA restriction enzyme analysis using nine restriction enzymes. BglI and SacI were the most discriminative enzymes and allowed the recognition of four DNA variants, all different from the prototype strain Trim. Within each of the epidemics, the strains tested could not be distinguished in this analysis. Between strains from different epidemics differences in DNA structure could be detected however. Thus, the Ad8 epidemics of 1983/1984, 1984, 1987, and 1988 appear to have been due to DNA variants Ad8/D7, D8, D9, and D10, respectively. These results demonstrate that the DNA of Ad8 seems to display a considerable variability, comparable to that observed with Ad7 and Ad21. As has been described for Ad7, Ad21 and Ad41, successive DNA variants of Ad8 prevail during one or more years, and are then replaced by other, newly emerging variants sometimes associated with epidemics.