155 research outputs found
Shallow NV- colour centres in diamond
No full textNegatively charged Nitrogen-Vacancy (NV-) colour centre in diamond is a well-known and characterised point defect with notable properties such as photostable bright fluorescence and spin states that can be initialised and read out, making it of great appeal for quantum technology applications.
Specifically, the latter can benefit from forming NV- defects in the proximity of the diamond surface. As an example, for nuclear magnetic resonance (NMR) sensing, it is necessary to have the NV- spins close to the surface as the coupling strength between magnetic dipoles decreases with the cubic distance of the defects from the surface. Shallow NV- defects can also be easily coupled with nanophotonic cavities for photon extraction. Furthermore, shallow NV- can also be beneficial in the biomedical field since the proximity to the surface allows the coupling with biomaterials for sensing applications, such as nano thermometry. However, the fabrication of shallow NV colour centres is challenging since it faces with several issues such as charge stability and low formation efficiency due to the behaviour of the diamond surface as an electron and a vacancy sink. The surface effects (i.e. vacancy sink, band bending and electron tunnelling) tend to convert NV- in NV0 centres which do not possess the same spin properties and are not commonly used for quantum technologies
The Concept of Information Asymmetry as a Theoretical Substantiation of the Phenomenon of Public Non-Financial Reporting
No full textThe global trend of widespread of public non-financial reporting makes the researchers face the task of finding its scientific basis. A unified theoretical and methodological basis of the concept of public non-financial reporting can be able to form the system of categories, laws, postulates and allow to implement effectively the processes of norm-setting, standardization and harmonization of public non-financial reporting with financial reporting. The purpose of the article is to provide the rationale for the choice of concept of information asymmetry as a fundamental theoretical basis to justify the phenomenon of public non-financial reporting. In the study the author applied the following research methods: analysis, synthesis, induction, deduction, comparison, generalization, and a systems approach. The article provides the results of analysis of extension of public non-financial reporting and identification of the problems of its application in Russian firms. The author systematizes the theoretical concepts be able to explain a phenomenon of public non-financial reporting: concept of sustainable development, the stakeholder theory, the doctrine of fair contracts. The author also demonstrates that the concept of information asymmetry is unifying for all of them and can be used to explain the voluntary adoption of obligations for additional disclosure of non-financial measurers by business. There is a need for a further scientific discussion of ideas about the implementation of public non-financial reporting as a prescriptive institutional or voluntary signaling mechanism, problem of its standardization, the counteract unfair usage of non-financial reporting to strengthen the negative effects of information asymmetry and the reallocation of market goods
A SiON Microring Resonator-Based Platform for Biosensing at 850 nm
No full textn this paper, we report on the design, fabrication, and characterization of a photonic circuit for biosensing applications. Silicon oxynitride with a bulk refractive index of 1.66 is the core-layer material. The photonic circuit is optimized for a wavelength of ~850 nm, which allows on-chip integration of the light source via cost effective vertical-cavity surface-emitting lasers and of the detector by using standard silicon photodetectors. Design as well as fabrication processes are explained in details. The best characteristics for the single optical components in the photonic circuit are: for single-mode channel waveguides with dimensions of 350 nm × 950 nm; propagation losses of 0.8 dB/cm; bending losses of 0.1 dB/90°-bend (radius of curvature 100 μm); 49/51 splitting ratio for 3-dB power splitters (directional couplers); quality factors up to 1.3 × 105 for microring resonators. Volumetric sensing yields a bulk sensitivity of 80 nm/RIU and a limit of detection of 3 × 10-6 RIU. Therefore, SiON-based photonic circuits represent a reliable material platform for biosensing in the short-wave near infrared region
Silicon nanocrystals for nonlinear optics and secure communications
No full textSilicon nanocrystals (Si-nc) are reviewed here for their interesting optical applications. On the one hand, they do exhibit quantum confinement effects. This allows turning silicon into a light-emitting material where luminescence can be excited by electrical injection. On the other hand, small sizes, large surfaces, and dielectric mismatch between the core and the surrounding matrix increase dramatically the nonlinear optical coefficients. This allows using Si-nc as a nonlinear material in different waveguide configurations. In this paper, we discuss specifically two different applications of Si-nc: (i) as a nonlinear material in various devices, e.g., in bistable optical cavities, in waveguide optical mode monitors that are based on two-photon excited luminescence detection, and in wavelength shifters by using four-wave mixing (FWM); (ii) as an entropy source for quantum random number generation, the key device for cryptography
Sensitivity and Limit of Detection of biosensors based on ring resonators
No full textIn this work, we present a study of the Sensitivity (S) and Limit of Detection (LOD) of microring based photonic biosensors as a function of the waveguide composition and dimensions. The target is Aflatoxin, which is a toxin of major concern for south Europe dairy industry. The sensing device is based on an array of multiple SiON microring resonators, fiber-coupled to both an 850 nm VCSEL and a silicon photodetectors, packaged with a microfluidic circuit. Volumetric sensing with glucose–water solutions of various concentrations yields a best sensitivity of 112 nm/RIU. To link these results to the Limit of Detection of the sensors, we also measured the noise of our experimental readout system and then calculated the LOD of our sensors. We found a best value of LOD of 1.6 × 10−6 RIU (referred to volumetric sensing). Finally, we detected Aflatoxin in solutions of various concentrations (down to 1.58 nM) by functionalized sensors. The functionalization is based on a wet silanization and specific DNA-aptamer binding on the chip. Reproducibility and re-usability of the sensor are investigated by several chemical treatments. Optimum procedure allows multiple sequential measurements with a good endurance. This work was supported by the FP7 EU project “Symphony” (Grant agreement no.: 610580). Keywords: Biosensor, Whispering Gallery Mode, Ring resonator, Aflatoxin, Limit of Detection, Sensitivit
Design and Optimization of SiON Ring Resonator-Based Biosensors for Aflatoxin M1 Detection
No full textIn this article, we designed and studied silicon oxynitride (SiON) microring-based photonic structures for biosensing applications. We designed waveguides, directional couplers, and racetrack resonators in order to measure refractive index changes smaller than 10−6 refractive index units (RIU). We tested various samples with different SiON refractive indexes as well as the waveguide dimensions for selecting the sensor with the best performance. Propagation losses and bending losses have been measured on test structures, along with a complete characterization of the resonator’s performances. Sensitivities and limit of detection (LOD) were also measured using glucose-water solutions and compared with expected results from simulations. Finally, we functionalized the resonator and performed sensing experiments with Aflatoxin M1 (AFM1). We were able to detect the binding of aflatoxin for concentrations as low as 12.5 nm. The results open up the path for designing cost-effective biosensors for a fast and reliable sensitive analysis of AFM1 in milk
New SDD arrays for the SIDDHARTA-2 experiment
No full textThis paper reports on the development of novel 2×4 monolithic Silicon Drift Detector (SDD) arrays with a thickness of 1 mm, carried out in the context of the SIDDHARTA-2 experiment, representing an advancement in terms of detection efficiency over the presently adopted 450 μm thick detectors. The chip contains eight square SDD cells with an active area of 8 × 8 mm2 each and has a total dimension of 20 mm × 36 mm. Besides an optimization of the sensor design for the thicker substrate, this new version of the SDD array is characterized by the introduction of an additional electrode on the entrance window, which should reduce the charge sharing between pixels. The paper also describes the development of a detection module based on a stacked structure involving two SDDs placed atop each other. This solution aims to further increase the detection efficiency of the system without acting on the substrate thickness of the SDD. The results from the spectroscopic characterization of these new detectors, and the implementation and characterization of the stacked SDDs module will be presented at the conference
Теория учета: современные проблемы и структурно-логическаямодель развития
No full textIntroduction, Purpose. The current stage of development in accounting is characterized by the methodological fragmentation of accounting theory, poor link between accounting theory and the development of social sciences, inability of accounting to cope with challenges of modern economy. These may be a reason for denial of scientific foundations of accounting theory. The purpose of the article is to provide a systematic analysis of the contemporary academic papers devoted to the problems of the development of accounting theory and methodology of accounting in order to formulate a structural-logical model for the development of a level of particular theoretical schemes of accounting. Methods. In the study the author applied the following research methods: analysis, synthesis, induction, deduction, comparison, generalization, and a systems approach. Results. The article provides the results of analysis and systemization of modern problems in accounting theory. The author considers the transformation peculiarities of methodology of accounting as a social and applied science, makes a proposal about how to organize research in the field of accounting theory in accordance with the Academician V. Stepin concept of scientific knowledge organization and formulates a structural-logical model of development of accounting theory concepts as a level of particular theoretical schemes. Discussions. There is a need for a further scientific discussion of ideas about the types of accounting as particular theoretical schemes based, on the one hand, on accounting theory, and on judgments and postulates taken from related fields of social sciences, on the other hand
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