191 research outputs found
Discrete Surface Solitons
No full textSurface waves exist along the interfaces between two different media and are known to display properties that have no analogue in continuous systems. In years past, they have been the subject of many studies in a diverse collection of scientific disciplines. In optics, one of the mechanisms through which optical surface waves can exist is material nonlinearity. Until recently, most of the activity in this area was focused on interfaces between continuous media but no successful experiments have been reported. However, the growing interest that nonlinear discrete optics has attracted in the last two decades has raised the question of whether nonlinear surface waves can exist in discrete optical systems. In this work, a detailed experimental study of linear and nonlinear optical wave propagation at the interface between a discrete one-dimensional Kerr-nonlinear system and a continuous medium (slab waveguide) as well as at the interface between two dissimilar waveguide lattices is presented. The major part of this dissertation is devoted to the first experimental observation of discrete surface solitons in AlGaAs Kerr-nonlinear arrays of weakly coupled waveguides. These nonlinear surface waves are found to localize in the channels at and near the boundary of the waveguide array. The key unique property of discrete surface solitons, namely the existence of a power threshold, is investigated in detail. The second part of this work deals with the linear light propagation properties at the interface between two dissimilar waveguide arrays (so-called waveguide array hetero-junction). The possibility of three different types of linear interface modes is theoretically predicted and the existence of one of them, namely the staggered/staggered mode, is confirmed experimentally. The last part of the dissertation is dedicated to the investigation of the nonlinear properties of AlGaAs waveguide array hetero-junctions. The predicted three different types of discrete hybrid surface solitons are analyzed theoretically. The experimental results on observation of in-phase/in-phase hybrid surface solitons localized at channels on either side of the interface are presented and different nature of their formation is discussed
Lossless Dimension Reduction for Integer Least Squares with Application to Sphere Decoding
No full textMinimum achievable complexity (MAC) for a maximum likelihood (ML) performance-Achieving detection algorithm is derived. Using the derived MAC, we prove that the conventional sphere decoding (SD) algorithms suffer from an inherent weakness at low SNRs. To find a solution for the low SNR deficiency, we analyze the effect of zero-forcing (ZF) and minimum mean square error (MMSE) linearly detected symbols on the MAC and demonstrate that although they both improve the SD algorithm in terms of the computational complexity, the MMSE linearly detected point has a vital difference at low SNRs. By exploiting the information provided by the MMSE of linear method, we prove the existence of a lossless dimension reduction which can be interpreted as the feasibility of a detection method which is capable of detecting the ML symbol without visiting any nodes at low and high SNRs. We also propose a lossless dimension reduction-Aided detection method which achieves the promised complexity bounds marginally and reduces the overall computational complexity significantly, while obtaining the ML performance. The theoretical analysis is corroborated with numerical simulations.Peer reviewe
The process of mythologizing in Sergiy Zhadan’s collection «Mesopotamia»
No full textУ статті йдеться про особливості літературного міфотворення у прозі та поезії сучасного українського автора С.
Жадана. Основним предметом дослідження є принципи міфологізації часу та простору у збірці оповідань та поезій
«Месопотамія». Аналізуються особливості творення художнього міфосвіту збірки на рівні поетики хронотопу. Про-
цес міфологізації часу та простору відбувається внаслідок накладання на реальну історію міфологічних сюжетів та
архетипів, ієрархієзації просторових образів, наскрізної уваги автора до мотивів часу та простору, що проявляється в
частому мікшуванні сакральних та профанних хронотопічних символів тощо.The article deals with the peculiarities involving the for-mation of mythology of literary prose and poetry of modern
Ukrainian author Sergiy Zhadan. The main object of the study is the principles of mythologizing of time and space
in the collection of short stories and poems “Mesopotamia”. The peculiarities of mythological world creation of the
collection are analyzed at the time-space level. The process of mythologizing of time and space is a result of the
interaction between the true story and mythological themes and archetypes, hierarchyzation of space images, the
author is thorough attention to the motives of time and space, resulting in frequent combination of sacred and ordinary
symbols of chronotope, etc
Ytterbium-laser-driven THz generation in thin lithium niobate at 1.9 kW average power in a passive enhancement cavity
No full textSingle-cycle, high-power, high-repetition-rate THz pulse sources are becoming the cornerstone of several scientific and industrial applications. A promising and versatile method for high-power THz generation is optical rectification in nonlinear crystals pumped by powerful near-infrared ultrafast laser systems. In this context, ytterbium-based laser sources are particularly advantageous in terms of power scalability and technology establishment. However, as the repetition rate increases toward hundreds of MHz, the conversion efficiency typically decreases, as most laser systems do not reach sufficiently high average powers to correspondingly enhance the peak power to drive the nonlinear conversion process efficiently. An alternative approach to achieving a sufficiently high average power at a high repetition rate is based on passive enhancement cavities, which boost the pulse energy of standard watt-level ytterbium lasers by orders of magnitude. We present the first demonstration of optical rectification in a passive enhancement cavity at multi-kW levels, achieved by a 240-fold power enhancement. By irradiating a 50-μm thin lithium niobate plate with 1.9-kW average power inside the enhancement cavity, we generate milliwatt-level THz pulses with 2-THz bandwidth and 93-MHz repetition rate, mostly limited by the driving pulse duration. To the best of our knowledge, this represents the highest driving average power used for optical rectification. This methodology represents a promising new step toward high-repetition-rate and high average power single-cycle THz sources using widely available multi-watt level Yb lasers
Er:Ti:LiNbO₃ ridge waveguides amplifiers by optical grade dicing and three-side Er/Ti in-diffusion
No full textN
Ascorbic acid metabolism in the organism under the lack of oxygen supply to the tissues
No full textPetrov Sergiy, Budnyak Oleksandr, Ozherelyeva Kateryna, Bytlan Oleksandr, Nikolaienko Kseniia. Ascorbic acid metabolism in the organism under the lack of oxygen supply to the tissues. Journal of Education, Health and Sport. 2017;7(6):583-590. eISSN 2391-8306. DOI http://dx.doi.org/10.5281/zenodo.827512
http://ojs.ukw.edu.pl/index.php/johs/article/view/4617
The journal has had 7 points in Ministry of Science and Higher Education parametric evaluation. Part B item 1223 (26.01.2017).
1223 Journal of Education, Health and Sport eISSN 2391-8306 7
© The Author 2017;
This article is published with open access at Licensee Open Journal Systems of Kazimierz Wielki University in Bydgoszcz, Poland
Open Access. This article is distributed under the terms of the Creative Commons Attribution Noncommercial License which permits any noncommercial use, distribution, and reproduction in any medium,
provided the original author(s) and source are credited. This is an open access article licensed under the terms of the Creative Commons Attribution Non Commercial License
(http://creativecommons.org/licenses/by-nc/4.0/) which permits unrestricted, non commercial use, distribution and reproduction in any medium, provided the work is properly cited.
This is an open access article licensed under the terms of the Creative Commons Attribution Non Commercial License (http://creativecommons.org/licenses/by-nc/4.0/) which permits unrestricted, non commercial
use, distribution and reproduction in any medium, provided the work is properly cited.
The authors declare that there is no conflict of interests regarding the publication of this paper.
Received: 03.06.2017. Revised: 20.06.2017. Accepted: 30.06.2017.
Ascorbic acid metabolism in the organism under the lack
of oxygen supply to the tissues
Sergiy Petrov, Oleksandr Budnyak*, Kateryna Ozherelyeva, Oleksandr Bytlan,
Kseniia Nikolaienko[a]
Odesa National Mechnykov I. I. University, Department of Biochemistry,
Dvoryanska Str., 2, Odesa, 65082, Ukraine
e-mail: [email protected]
[a] Prof. S. A. Petrov, Dr. O. K. Budnyak, postgraduate student K. Yu. Ozherelyeva,
O. M. Bytlan, K. S. Nikolaienko
Abstract
The number and ratios of the metabolites of vitamin C - ascorbic, dehydroascorbic and diketogulonic acids were studied under the action of closed space hypoxia, acute blood loss and during sleep – the conditions associated with various oxygen saturation of the organism. It was found that in case of closed space hypoxia, the level of ascorbic and diketogulonic acid decreased with a simultaneous increase in the content of dehydroascorbic acid in the heart and brain. Acute blood loss resulted in decrease in the level of all metabolites of ascorbic acid. During sleep, the level of ascorbic acid metabolites increased. The ratio of vitamin-active metabolites to vitamin-inactive form of ascorbic acid in case of closed space hypoxia and acute blood loss decreased, and during sleep – it did not change significantly.
Keywords: vitamins, metabolism, ascorbic acid, hypoxi
Fiber-optic sensor measuring spatial distributions of refractive index and temperature
No full textIn this work, we present a fiber sensor designed to measure simultaneously spatial inhomogeneities of the refractive index and temperature in liquid media, for example, induced by biochemical reactions. The sensor's constituent elements are Fabry-Perot microresonators fabricated in standard single-mode optical fibers by diamond blade dicing. To allow simultaneous measurements of different refractive indices, the sensor comprises two open cavities approximately 2 mm apart. With a small Si inlay inserted into one of the resonators used for temperature measurements, the sensor allows for immediate compensation of crosstalk between temperature- and composition-induced fluids' refractive index changes. The measurements were evaluated by phase tracking of the characteristic Fourier transform components of the sensor's backreflected spectra. The temperature sensitivity of the Si inlay is 0.063 rad/°C (79 pm/°C), and an accuracy of 0.01°C is obtained. Meanwhile, the two refractive index sensing (open) cavities show a sensitivity of 1168 and 1153 nm/RIU for temperature-compensated measurements. Finally, the sensor performance to measure spatial distributions is demonstrated by measuring the diffusion behavior of sucrose in water, which allows precise monitoring of hydration effects and breaking of bonds at elevated temperatures.N
Efficient watt-level 0.775 μm SHG and 3.3 μm DFG in annealed and reverse proton exchanged diced PPLN ridge waveguides
No full textN
Efficient watt-level 0.775 μm SHG and 3.3 μm DFG in annealed and reverse proton exchanged diced PPLN ridge waveguides
No full textWe report on the fabrication of ridge waveguides formed in congruent periodically poled lithium niobate (PPLN). The waveguides were fabricated by periodic poling, proton exchange, subsequent annealing and reverse proton exchange followed by diamond blade dicing. Up to 1 W of single-pass second-harmonic generation at 775 nm has been realized in 50 mm long ridge waveguides with internal conversion efficiency of 70%. Furthermore, difference frequency generation at 3.3 μm of two pump waves at 1.05 μm and 1.55 μm has been obtained in similarly fabricated PPLN ridge waveguides with an appropriate poling period
Refractive index sensing in a monolithic micro-optofluidic lithium niobate chip
No full textWe report a micro-optofluidic refractive index sensor integrating a femtosecond laserwritten waveguide and selectively etched channel in lithium niobate. Fabry-Perot spectra show a 1212 nm/RIU sensitivity at 1554 nm for refractive index steps of 10₋₃.Vo
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