Hybrid optical fiber for light-induced superconductivity

We exploit the recent proposals for the light-induced superconductivity mediated by a Bose-Einstein condensate of exciton-polaritons to design a superconducting fiber that would enable long-distance transport of a supercurrent at elevated temperatures. The proposed fiber consists of a conventional core made of a silica glass with the first cladding layer formed by a material sustaining dipole-polarised excitons with a binding energy exceeding 25 meV. To be specific, we consider a perovskite cladding layer of 20 nm width. The second cladding layer is made of a conventional superconductor such as aluminium. The fiber is covered by a conventional coating buffer and by a plastic outer jacket. We argue that the critical temperature for a superconducting phase transition in the second cladding layer may be strongly enhanced due to the coupling of the superconductor to a bosonic condensate of exciton-polaritons optically induced by the evanescent part of the guiding mode confined in the core. The guided light mode would penetrate to the first cladding layer and provide the strong exciton-photon coupling regime. We run simulations that confirm the validity of the proposed concept. The fabrication of superconducting fibers where a high-temperature superconductivity could be controlled by light would enable passing superconducting currents over extremely long distances

Mycotoxins in Tea: Occurrence, Methods of Determination and Risk Evaluation

Tea is one of the most popular beverages all over the world. Being an everyday drink for almost everyone, for centuries tea was considered safe and healthy. However, fungal contamination of tea at any stage of commodity production can pose a serious health hazard due to the accumulation of toxic secondary metabolites of moulds. Contemporary research revealed incidences of highly contaminated samples. Mycotoxin transfer from naturally contaminated raw tea into beverage was well studied for ochratoxin A only, and the possible leak of other mycotoxins is discussed. The results of several surveys were combined to evaluate aflatoxin B1 and ochratoxin A contamination levels in black tea and Pu-erh. Exposure estimate to aflatoxin B1 and ochratoxin A due to tea consumption was carried out based on these data. Average contamination level corresponds to the exposure of 3–40% (aflatoxin B1) and 5–24% (ochratoxin A) of mean overall estimates for different cluster diets. Lack of data does not allow the conclusion for the necessity of public health protection measures. It is necessary to perform representative studies of different kinds of tea for regulated mycotoxins at least. Contemporary techniques for analysis of mycotoxins in tea are summarised in the present review

Mycotoxins in Tea: Occurrence, Methods of Determination and Risk Evaluation

Tea is one of the most popular beverages all over the world. Being an everyday drink for almost everyone, for centuries tea was considered safe and healthy. However, fungal contamination of tea at any stage of commodity production can pose a serious health hazard due to the accumulation of toxic secondary metabolites of moulds. Contemporary research revealed incidences of highly contaminated samples. Mycotoxin transfer from naturally contaminated raw tea into beverage was well studied for ochratoxin A only, and the possible leak of other mycotoxins is discussed. The results of several surveys were combined to evaluate aflatoxin B1 and ochratoxin A contamination levels in black tea and Pu-erh. Exposure estimate to aflatoxin B1 and ochratoxin A due to tea consumption was carried out based on these data. Average contamination level corresponds to the exposure of 3⁻40% (aflatoxin B1) and 5⁻24% (ochratoxin A) of mean overall estimates for different cluster diets. Lack of data does not allow the conclusion for the necessity of public health protection measures. It is necessary to perform representative studies of different kinds of tea for regulated mycotoxins at least. Contemporary techniques for analysis of mycotoxins in tea are summarised in the present review

Special issues of IFRS application in Russian organizations

In modern conditions, Russian accounting is increasingly oriented to international standards. Accounting for leasing relations is also subject to changes that are associated with the transition of Russian accounting to international financial reporting standards (IFRS). In 2016, a new standard was approved for accounting for leases in public sector organizations - the SPS “Leases” (entered into force on January 1, 2018). For other organizations, on October 16, 2018, FAS 25 “Lease accounting” was approved. This standard introduces the type of asset - the right to lease, which represents a new format for accounting methodological documents. The purpose of the study is to consider the features of the application of FAS 25 “Lease accounting” based on the new IFRS 16 “Leases” in accounting for operating leases of Russian organizations. The authors consider the lease relations of economic entities of the Russian economy using the example of pharmacy organizations, in particular, the main aspects of FAS 25, the procedure for accounting for operating leases from the perspective of a lessee and lessor, features of accounting for sublease, leaseback, lease on special terms, as well as disclosure of lease information in accounting (financial) statements. The methodological basis of the study consisted of elements of the accounting method (system of accounts, double entry book-keeping, reporting) and tools of economic analysis (method of comparison, absolute and relative values, tabular and graphical representations of data, coefficient method). As a result of the study, an operating lease accounting mechanism was proposed, which reflects the specifics of pharmacy organizations

Polygonal patterns of confined light

We propose a technique for the generation of polygonal optical patterns in real space using a combined effect of the spin–orbit interaction and confinement of light in the plane of a dielectric optical microcavity. The spin–orbit interaction emerging from the splitting in transverse electric (TE) and transverse magnetic (TM) optical modes of the microcavity gives rise to oscillations in space of propagating macroscopic wave packets of polarized photons. Confined in a harmonic potential, the latter follow closed trajectories of a polygonal form. We demonstrate the possibility of excitation by a continuous wave resonant optical pumping of polygonal optical patterns with a controllable (both even and odd) number of vertices

Online peer editing: the influence of comments, tracked changes and perception of participation on students’ writing performance

Abstract While peer-editing is considered an important part of developing students’ academic writing, questions remain about how different types of peer-editing affect subsequent student performance. The present study looked at a group of university students (N = 149) engaged in peer editing of one another’s essays in an online security studies course. The analysis was conducted from two perspectives: feedback givers and feedback receivers. More specifically, the relationships between the giving of comments and tracking changes in peer’s work and writing score on essays were explored. The results showed that there was a positive correlation between the total number of received comments and the student's writing score, whereas there was no correlation for the number of tracked changes (neither words deleted, nor words added). Surprisingly, students who assume that peers provide high quality tracked changes demonstrate worse writing performance. This research shows the importance of nuance in understanding peer editing types and their influence on students’ performance, as well as highlighting potential complexities of the interplay between students’ collaborative activities, their performance, and their attitudes

Manipulation of the propagation of light in tunable nonlinear Bragg mirrors with embedded quantum wells

The specially designed nonlinear semiconductor structure with embedded quantum wells possesses a tunable hyperbolic dispersion. We revealed dynamical regimes for localized polariton wave packets resulting from competition of the hyperbolic dispersion and the repulsive nonlinearity.</p

Bright Single-Photon Emitters with a CdSe Quantum Dot and Multimode Tapered Nanoantenna for the Visible Spectral Range

We report on single photon emitters for the green-yellow spectral range, which comprise a CdSe/ZnSe quantum dot placed inside a semiconductor tapered nanocolumn acting as a multimode nanoantenna. Despite the presence of many optical modes inside, such a nanoantenna is able to collect the quantum dot radiation and ensure its effective output. We demonstrate periodic arrays of such emitters, which are fabricated by focused ion beam etching from a II-VI/III-V heterostructure grown using molecular beam epitaxy. With non-resonant optical pumping, the average count rate of emitted single photons exceeds 5 MHz with the second-order correlation function g(2)(0) = 0.25 at 220 K. Such single photon emitters are promising for secure free space optical communication lines

The Poly(chloro-p-xylylene)-Ag Metal-Polymer Nanocomposites Obtained by Controlled Vapor-Phase Synthesis for SERS Effect Realisation

Substrates based on the metal-polymer nanocomposites 2,3-dichloro-p-xylylene-silver (PCPX-Ag) that realize the effect of surface-enhanced Raman scattering (SERS) were developed. To obtain nanocomposites, the vapor-phase polymerization method was used (VDP), which makes it possible to control the nanocomposite microstructure. In the process of self-assembly during VDP, nanocomposite films with inclusions of silver particles were formed on the polycore substrates. Silver content varied from 2.5 to 16% vol. The possibility of using such substrates for the detection of low-molecular substances, for example 5,5′-dithiobis- (2-nitrobenzoic acid) (DTNB) analyte, by the SERS method with an enhancement factor of up to 104, was demonstrated. The dependence of the SERS spectra enhancement on the microstructure of the nanocomposite and the silver content was determined. The optical and morphological properties of nanocomposites were also investigated and their dependence on the silver content was shown. It has been demonstrated that the nanocomposite is SERS selective since when working with complex solutions in the presence of high molecular weight substances, signal enhancement was only observed for low molecular weight substances