Sedimentary waves are represented by a series of wavelike accumulative features with various degrees of morphological expression. These morphological forms are superimposed on the underlying surface ...with a clear stratigraphic unconformity. The hydrophysical processes are the main relief-forming factors of such features. During expeditions 38 (2018) and 41 (2019) of the R/V
Akademik Nikolay Strakhov
, the seafloor was mapped between the Kanin Peninsula and inlet of Cheshskaya Bay and new data were acquired on the morphology sedimentary waves. New data obtained in summer (July–August) 2019 show rapid changes in the natural hydrodynamic environment influencing the alternation of the sedimentary waves. The occurrence of hazardous natural processes, geological and geomorphological risks, and the level of threats were identified, especially with respect to the prolonged navigation period along the Northern Sea Route.
The study is devoted to the development of a microscope operating at a wavelength of 3.37 nm in the water window. A Schwarzschild lens with a multilayer coating is used as an image-forming objective ...lens. The microscope has a theoretical resolution of up to 13 nm and a field of view of 7.3–97.5 µm depending on the magnification. A low depth of focus (±37.5 nm) allows one to implement the
z-
tomography of samples. A schematic diagram of the microscope, the result of aspherizing the mirror collector, and the results of measuring the roughness of the mirror substrates are given. A three-point method for mounting the mirrors and also a magnetic damper operating on Foucault currents are described. The exposure time is estimated.
We present the optical layout and actual design of a compact high-aperture referenceless point diffraction interferometer with a diffraction reference wave. The basic concept of this interferometer ...is based on a single-mode optical fibre with a subwave output aperture, which is used as a source of spherical reference waves. The interferometer is designed for high-precision measurements of the surface shape and aberrations of optical elements. It makes use of a diffraction reference wave and is developed for mass industrial applications. The proposed design does not require the involvement of special external conditions, and reduces the need for calibrated reference surfaces. We evaluate the performance of our interferometer for highprecision measurements and demonstrate its use by presenting results obtained from measuring the shapes of spherical references from various manufacturers and the aberration of a five lens objective.
•Concept of a point diffraction interferometer based on tipped single mode optical fiber.•The interferometer can be used in the factory without frequent calibrations and adjustments.•Interferometer has sub-nanometer measurement precision.
The paper describes a high-performance facility for ion beam processing of the surface of optical elements. The facility is equipped with three technological ion sources, which allow working with ...inert or reactive gases, and a five-axis goniometer. Two sources (KLAN-103M and KLAN-163M) have a wide-aperture quasi-parallel ion beam and a third ion source with the focused ion beam (width of the output beam is Ø1–15mm by changing the diaphragm). For a focusing ion source an optimal diaphragm material (sapphire) and the Ar energy range (less than 400eV), which minimizes deposition on the surface of the workpiece the material sputtered from the edge of the diaphragm, are found. The concept of a movable workpiece has allowed realizing within one vacuum chamber three methods of ion beam surface treatment: aspherization, local shape errors correction and ion polishing. A detailed description of all the surface treatment methods is given. An algorithm for selecting the ion beam diameter and scanning steps for the local shape errors correction depending on the lateral dimension of the surface errors is proposed. The facility allows to produce an optical surface of any complex (convex/concave) shape, including higher-order aspheres with an asymmetrical profile and a diameter of up to 300mm, with a subnanometer precision of the surface shape and the effective roughness in the range of spatial frequencies q∈2.5·10−2–6.0·101μm−1 down to σeff=0.14nm.
We report on fabrication and studies of composite heterostuctures consisting of an Al
0.55
Ga
0.45
N/A
l0.8
Ga
0.2
N quantum well and surface Al nanoislands, grown by plasma-assisted molecularbeam ...epitaxy on c-sapphire substrates. The influence of a substrate temperature varied between 320 and 700ºC on the size and density of the deposited Al nanoislands is evaluated. The effect of Al nanoislands on decay kinetics of the quantum well middle-ultraviolet photoluminescence has been investigated by time resolved photoluminescence. The samples with the maximum density of Al nanoislands of 10
8
cm
–2
and lateral dimensions in the range of 100–500 nm demonstrated shortening of the photoluminescence lifetime, induced by interaction of the emitting quantum well and the plasmonic metal particles.
In this article the authors defined the limits of applicability of the pipeline pusher as additional equipment for pipeline construction when using trenchless methods. In this case, the pushing force ...is applied to the free end of the pipeline section located on the day surface. The authors obtained analytical dependences for determining the stress-strain state of the pushed pipeline when using the pusher in a particular case. In addition, they identified values of axial pushing force that are considered dangerous, because they can cause pipeline dropping down from the roller supports during pipeline pullback.
•EFSA’s OpenFoodTox database contains summary hazard data for 5000 chemicals in food and feed.•OpenFoodTox can be downloaded and visualised using a micro-strategy tool.•Current and future development ...include links to in silico models and integration of New Approach Methodologies.
Since its creation in 2002, the European Food Safety Authority (EFSA) has produced risk assessments for over 5000 substances in >2000 Scientific Opinions, Statements and Conclusions through the work of its Scientific Panels, Units and Scientific Committee. OpenFoodTox is an open source toxicological database, available both for download and data visualisation which provides data for all substances evaluated by EFSA including substance characterisation, links to EFSA’s outputs, applicable legislations regulations, and a summary of hazard identification and hazard characterisation data for human health, animal health and ecological assessments. The database has been structured using OECD harmonised templates for reporting chemical test summaries (OHTs) to facilitate data sharing with stakeholders with an interest in chemical risk assessment, such as sister agencies, international scientific advisory bodies, and others. This manuscript provides a description of OpenFoodTox including data model, content and tools to download and search the database. Examples of applications of OpenFoodTox in chemical risk assessment are discussed including new quantitative structure–activity relationship (QSAR) models, integration into tools (OECD QSAR Toolbox and AMBIT-2.0), assessment of environmental footprints and testing of threshold of toxicological concern (TTC) values for food related compounds. Finally, future developments for OpenFoodTox 2.0 include the integration of new properties, such as physico-chemical properties, exposure data, toxicokinetic information; and the future integration within in silico modelling platforms such as QSAR models and physiologically-based kinetic models. Such structured in vivo, in vitro and in silico hazard data provide different lines of evidence which can be assembled, weighed and integrated using harmonised Weight of Evidence approaches to support the use of New Approach Methodologies (NAMs) in chemical risk assessment and the reduction of animal testing.
We demonstrate a Schottky ultraviolet photodiode (UV-PD) and a UV light-emitting diode (UV-LED) based on AlGaN heterostructures grown by plasma-assisted molecular beam epitaxy. The spectral ...responsivity of the Schottky UV-PD is 3 mA/W at 271 nm at zero bias and decreases by two orders of magnitude for the spectral range of longer wavelengths ( > 300 nm). The sub-monolayer digital alloying technique was used for growing the AlGaN quantum wells in UV-LEDs emitting a single electroluminescence peak at 273 nm.
We present the results of hybrid photoconductive antenna THz emission enhanced by silver nanoantenna arrays. By varying the size of nanoantennas and the distance between them, we obtain the greatest ...value of optical-to-THz conversion efficiency reached so far. The results of experimental investigations are in a good agreement with numerical simulations. The conversion efficiency reveals over 5-fold improvement at certain frequencies, if compared with similar photoconductive antenna without silver nanoparticles, while previous results for this type of antenna barely exceeded 2-fold conversion efficiency gain.
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