Edge Channel Interference Controlled by Landau Level Filling

We study the visibility of Aharonov-Bohm interference in an electronic Mach-Zehnder interferometer (MZI) in the integer quantum Hall regime. The visibility is controlled by the filling factor $\nu$ and is observed only between $\nu \approx 2.0$ and 1.0, with an unexpected maximum near $\nu=1.5$. Three energy scales extracted from the temperature and voltage dependences of the visibility change in a very similar way with the filling factor, indicating that the different aspects of the interference depend sensitively on the local structure of the compressible and incompressible strips forming the quantum Hall edge channels.Comment: 5 pages, 5 figures, final version accepted for publication in Phys. Rev.

Decoherence and single electron charging in an electronic Mach-Zehnder interferometer

We investigate the temperature and voltage dependence of the quantum interference in an electronic Mach-Zehnder interferometer using edge channels in the integer quantum-Hall-regime. The amplitude of the interference fringes is significantly smaller than expected from theory; nevertheless the functional dependence of the visibility on temperature and bias voltage agrees very well with theoretical predictions. Superimposed on the Aharonov-Bohm (AB) oscillations, a conductance oscillation with six times smaller period is observed. The latter depends only on gate voltage and not on the AB-phase, and may be related to single electron charging.Comment: 4 pages, 6 figures, discussion of charging effect change

Counting Statistics and Dephasing Transition in an Electronic Mach-Zehnder Interferometer

It was recently suggested that a novel type of phase transition may occur in the visibility of electronic Mach-Zehnder Interferometers. Here, we present experimental evidence for the existence of this transition. The transition is induced by strongly non-Gaussian noise that originates from the strong coupling of a quantum point contact to the interferometer. We provide a transparent physical picture of the effect, by exploiting a close analogy to the neutrino-oscillations of particle physics. In addition, our experiment constitutes a probe of the singularity of the elusive full counting statistics of a quantum point contact.Comment: 7 pages, 4 figures (+Supplement 8 pages, 9 figures

Precision of spiral-bevel gears

The kinematic errors in spiral bevel gear trains caused by the generation of nonconjugate surfaces, by axial displacements of the gears during assembly, and by eccentricity of the assembled gears were determined. One mathematical model corresponds to the motion of the contact ellipse across the tooth surface, (geometry I) and the other along the tooth surface (geometry II). The following results were obtained: (1) kinematic errors induced by errors of manufacture may be minimized by applying special machine settings, the original error may be reduced by order of magnitude, the procedure is most effective for geometry 2 gears, (2) when trying to adjust the bearing contact pattern between the gear teeth for geometry 1 gears, it is more desirable to shim the gear axially; for geometry II gears, shim the pinion axially; (3) the kinematic accuracy of spiral bevel drives are most sensitive to eccentricities of the gear and less sensitive to eccentricities of the pinion. The precision of mounting accuracy and manufacture are most crucial for the gear, and less so for the pinion

Kinematic precision of gear trains

Kinematic precision is affected by errors which are the result of either intentional adjustments or accidental defects in manufacturing and assembly of gear trains. A method for the determination of kinematic precision of gear trains is described. The method is based on the exact kinematic relations for the contact point motions of the gear tooth surfaces under the influence of errors. An approximate method is also explained. Example applications of the general approximate methods are demonstrated for gear trains consisting of involute (spur and helical) gears, circular arc (Wildhaber-Novikov) gears, and spiral bevel gears. Gear noise measurements from a helicopter transmission are presented and discussed with relation to the kinematic precision theory

The main factors and prospects for the restoration of biodiversity in technogenic territories (on the example of the Poltava Mining and Processing Plant)

Mining activities radically change natural ecosystems, the recovery of which is not possible without the restoration of native or transformed communities of autotrophic and heterotrophic organisms. In order to analyze the success of biodiversity restoration using unified methods, an inventory of higher plant flora and avifauna species in the technogenic territories of the Poltava Mining and Processing Plant was carried out. The dominant species identified in mining dumps, tailings, bypass and drainage canals, urban wastewater treatment and bioengineering facilities and on the PMP territory have been studied in detail. The studies were carried out in the spring-summer period of 2021–2022. The avifauna includes 140 species belonging to 18 orders and 45 families (Passeriformes predominate – 62.0%). 103 species nest on the PMP territory, 32 nomadic and 5 transient species are also registered. The nesting avifauna is dominated by representatives of both native nemoral (16.0%, n = 103) and forest-steppe (13.0%) and tropical (14.0%) avifauna. A significant number of birds belong to limnophiles, which prevail in the territories of the urban wastewater treatment plant (66.7%, n = 30) and tailings (62.5%, n = 24). They are also common in the bypass and drainage canals, where hydro- and hygrophilous phytocenoses have formed, similar to floodplain and real meadows as part of adjacent wetland ecosystems. Among the surrounding natural biogeocenoses, there are no steppe ones with their inherent unique floristic composition, which explains the small number of stepants in the studied flora and campophiles in the avifauna. In recovery successions, general patterns were revealed: biogeocenoses surrounding the technogenic territories of the PMP are the main source of producer diasporas and a variety of consumers, which are so necessary for the restoration of degraded landscapes. Phanerophytes from the genera Populus, Pinus, Fraxinus, Ulmus, Morus, Juglans, etc. are determinants in the sylvacenoses formed on the dumps and territories of the plant. Therefore, dendrophiles characteristic of neighbouring pine and floodplain forests, as well as garden phytocenoses in the private sector territory, dominate in the ornithocomplexes. Nationally rare avifauna includes 5 species, two of which nest. Among the identified bird species, the following nesting species are listed in the Red Book of Ukraine: Columba oenas, Himantopus himantopus, as well as transient and nomadic species: Hieraaetus pennatus, Haliaeetus allbicilla, Milvus migrans. The success of the natural formation of plant communities, the rich ornithological complex with the participation of rare species, and the location of the PMP territory within the migration routes indicate the expediency of further research into the possibilities of their inclusion in the nature reserve fund with the status of “territory of renaturalization”

Nonlocal vortex motion in mesoscopic amorphous Nb0.7Ge0.3 structures

We study nonlocal vortex transport in mesoscopic amorphous Nb0.7Ge0.3 samples. A dc current I is passed through a wire connected via a perpendicular channel, of a length L= 2-5 um, with a pair of voltage probes where a nonlocal response Vnl ~ I is measured. The maximum of Rnl=Vnl/I for a given temperature occurs at an L-independent magnetic field and is proportional to 1/L. The results are interpreted in terms of the dissipative vortex motion along the channel driven by a remote current, and can be understood in terms of a simple model.Comment: 4 pages, 3 figure

Atomic Force Microscopy and Optical Studies of Organic Thin Films with Hydrogen-Bonded Networks

Brewster angle microscopy and atomic force microscopy were used to characterize the surface morphology of thin films in situ or after transfer onto solid supports. Two acids were studied, differing in carboxylic acid head groups, resulting in significantly different morphological features for thin films formed from these two amphiphiles on a Langmuir trough. Differences in self-assembly and domain sizes were correlated with the formation of hydrogen-bonded networks. The influence of surface hydrophobicity or hydrophilicity during deposition on morphology was also characterized, with spherulitic features appearing in some samples