On one class of holonomy groups in pseudo-Riemannian geometry

We describe a new class of holonomy groups on pseudo-Riemannian manifolds. Namely, we prove the following theorem. Let g be a nondegenerate bilinear form on a vector space V, and L:V -> V a g-symmetric operator. Then the identity component of the centraliser of L in SO(g) is a holonomy group for a suitable Levi-Civita connection.Comment: (revised version

Organic solar cells as high-speed data detectors for visible light communication

Funding: Engineering and Physical Sciences Research Council (EPSRC) (EP/I00243X, EP/K00042X/1, EP/K008757/1).We show that solar cells, widely used in portable devices for power generation, can simultaneously extract a high-speed data signal in an optical wireless communication link. This Letter reports, to the best of our knowledge, the first use of an organic solar cell as an energy-harvesting receiver for visible light communications (VLCs). While generating maximum power in the cell, the communication link can deliver a data rate of 34.2 Mbps with a bit error rate of 4.08 x 10(-4) using an implementation of orthogonal frequency-division multiplexing. This approach could lead to printed optical data receivers in future eco-friendly VLC systems. Simultaneous functions of data communication and energy harvesting have great implications for the connectivity of future smart devices, many of which could become self-powered units as part of the "Internet of Things."PostprintPeer reviewe

Realisation of holonomy algebras on pseudo-Riemannian manifolds by means of Manakov operators

In the present thesis we construct a new class of holonomy algebras in pseudo-Riemannian geometry. Starting from a smooth connected manifold M, we consider its (1;1)-tensor fields acting on the tangent spaces. We then prove that there exists a class of pseudo- Riemannian metrics g on M such that the (1;1)-tensor fields are g-self adjoint and their centralisers in the Lie algebra so(g) are holonomy algebras for the Levi-Civita connection of g. Our construction is elaborated with the aid of Manakov operators and holds for any signature of the metric g

Visible Light Communication Using a Blue GaN μLED and Fluorescent Polymer Color Converter

This letter presents a novel technique to achieve high-speed visible light communication (VLC) using white light generated by a blue GaN mu LED and a yellow fluorescent copolymer. We generated white light suitable for room illumination by optimizing the ratio between the blue electroluminescence of the mu LED and yellow photoluminescence of the copolymer color converter. Taking advantage of the components' high bandwidth, we demonstrated 1.68 Gb/s at a distance of 3 cm (at 240 lx illumination). To the best of our knowledge, this is the fastest white light VLC results using a single blue LED/color converter combination.PostprintPeer reviewe

MINERAL ASSEMBLAGES AND GENESIS OF THE Cu-Au EPITHERMAL DEPOSITS IN THE SOUTHERN PART OF THE PANAGUYRISHTE ORE DISTRICT, BULGARIA

Epithermal Cu-Au deposits hosted within volcanic rocks (Radka, Elshitsa, Krassen) are related to Late Cretaceous andesite-dacite volcanic terrain in the Panagyurishte ore district. The Cu-Au ores are linked by a similar mineralogy and differ by the ratio of tennantite, bornite, enargite and discrete trace minerals of Ga, Ge, In and Bi (e.g., roquesite, germanite, betekhtinite, renierite, vinciennite, aikinite). Bi-Se-Te and Ga-Ge-ln-Sn signature with pronounced Au-enrichment of the bornite rich ores is a characteristic feature underlying the increasing role of the fS2/f02 control during the transition from IS te HS environment. Formation of the epithermal Cu-Au deposits appears to have occurred during a single broad event of contemporaneous formation of epithermal and porphyry systems.The close connection between the volcano-plutonic structures facilitates the multistage and polycyclic character of their hydrothermal systems, the similar character of the epithermal ores and the mineral succession in Elshitsa, Radka and Krassen deposits. The ô^S ratios in the sulphide minerals range from -6.7 to 4.0, suggesting comparable magmatic sources for the epithermal mineralizing fluids and close link with porphyry environment

MODERN METHODS AND POSSIBILITIES FOR DYNAMIC DIAGNOSTICS OF PULMONARY DISEASES

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On a new class of holonomy groups in pseudo-Riemannian geometry

On a new class of holonomy groups in pseudo-Riemannian geometr

Liquid-based cytology and its practicability in Bulgaria

PURPOSE: Our aim was to summarize the foreign and our own experience in screening the cervical cancer by using conventional Papanicolaou (PAP) smear and liquid-based cytology (LBC).MATERIAL AND METHODS: In the Department of Obstetrics and Gynecology, Medical University of Varna, we examined 100 patients and compared the results from LBC with those from conventional PAP smear concerning different criteria as well as to test LBC practicability in Bulgaria.RESULTS: There were significant advantages of LBC mainly due to the lower number of unsatisfactory results and higher specificity of low-grade squamous intraepithelial lesions (LSIL). The comparison with the results from foreign studies demonstrated the same tendencies and diagnostic values.CONCLUSION: Our investigation proved the benefits of LBC in screening the cervical cancer. A much broader application of this method in Bulgaria was recommended taking into consideration that it was rarely used at presence.Scripta Scientifica Medica 2013; 45(2): 66-69