Rapid quasi-periodic oscillations in the relativistic jet of BL Lacertae.

Blazars are active galactic nuclei (AGN) with relativistic jets whose non-thermal radiation is extremely variable on various timescales. This variability seems mostly random, although some quasi-periodic oscillations (QPOs), implying systematic processes, have been reported in blazars and other AGN. QPOs with timescales of days or hours are especially rare in AGN and their nature is highly debated, explained by emitting plasma moving helically inside the jet, plasma instabilities or orbital motion in an accretion disc.

Steganography in color images with random order of pixel selection and encrypted text message embedding.

Information security is major concern in modern digital ages, and the outdated algorithms need to be replaced with new ones or to be improved. In this article a new approach for hiding secret text message in color images is presented, combining steganography and cryptography. The location and the order of the image pixels chosen for information embedding are randomly selected using chaotic pseudo-random generator.

BOOST: Medical Image Steganography Using Nuclear Spin Generator.

In this study, we present a medical image stego hiding scheme using a nuclear spin generator system. Detailed theoretical and experimental analysis is provided on the proposed algorithm using histogram analysis, peak signal-to-noise ratio, key space calculation, and statistical package analysis. The provided results show good performance of the brand new medical image steganographic scheme.

Internal radiation dose assessment of radiopharmaceuticals prepared with cyclotron-produced Tc.

Purpose: Technetium-99m ( Tc) is the radioisotope most widely used in diagnostic nuclear medicine. It is readily available from Mo/ Tc generators as the β decay product of the Mo (T  = 66 h) parent nuclide. This latter is obtained as a fission product in nuclear reactors by neutron-induced reactions on highly enriched uranium.

Radioisotopic purity and imaging properties of cyclotron-produced Tc using direct Mo(p,2n) reaction.

Evaluation of the radioisotopic purity of technetium-99m (Tc) produced in GBq amounts by proton bombardment of enriched molibdenum-100 (Mo) metallic targets at low proton energies (i.e. within 15-20 MeV) is conducted.

New records of millipedes and centipedes from Bulgaria, with an annotated checklist of the Bulgarian myriapods.

The present paper records new and poorly known myriapods (Diplopoda, Chilopoda) collected in Bulgaria in the last 10 years. Four new species are reported as new to the Bulgarian fauna: Lithobius melanops Newport, 1845 (Chilopoda: Lithobiomorpha: Lithodiidae), Polydesmus collaris C.L.

A study on current status of herbal utilization in Bulgaria. Part 2: Safety concerns.

Ethnopharmacological Relevance: Herbs play an important role for Bulgarian people since centuries. Nowadays an increasing number of people are using over-the-counter natural health products. It is widely accepted that herbs are harmless and herbal remedies are often used without safety precaution.

Near-infrared dispersion and spin-orbit interaction of Co doped (80-x)Sb2O3-20Na2O-xWO3 glasses.

The present paper discusses the fact that the absorption spectra of doped with 0.1% Co3O4 glasses with the composition (80-x)Sb2O3-20Na2O-xWO3 are measured in the spectral region 1200-1400nm. The optical structure of Co(2+) is analyzed and the energies of the electron transitions in the metal ion are determined.

Bifunctionalized Allenes. Part XVI. Synthesis of 3-Phosphoryl-2,5-dihydrofurans by Coinage Metal-Catalyzed Cyclo-isomerization of Phosphorylated α-Hydroxyallenes.

Phosphorylated α-hydroxyallenes 1 and 2 were smoothly converted into the corresponding 2,5-dihydrofurans 3 and 4 in an 5-endo-trig cycloisomerization reaction by using 5 mol % of coinage metal salts as catalyst. Experimental conditions such as the type of the solvent, the reaction temperature, the mol % and the type of the catalyst were optimized. This mild and efficient cyclization method can be applied to dimethyl 1-hydroxyalkyl-alka-1,2-dienephosphonates 1 and 2-diphenylphosphinoyl-2,3-dien-1-ols 2a-c and 3-diphenylphosphinoyl-3,4-dien-2-ols 2d,e, furnishing 3-phosphorylated 2,5-dihydrofurans 3 and 4 in very good yields.

Novel image encryption scheme based on Chebyshev polynomial and Duffing map.

We present a novel image encryption algorithm using Chebyshev polynomial based on permutation and substitution and Duffing map based on substitution. Comprehensive security analysis has been performed on the designed scheme using key space analysis, visual testing, histogram analysis, information entropy calculation, correlation coefficient analysis, differential analysis, key sensitivity test, and speed test. The study demonstrates that the proposed image encryption algorithm shows advantages of more than 10(113) key space and desirable level of security based on the good statistical results and theoretical arguments.

Bifunctionalized allenes. Part XV. Synthesis of 2,5-dihydro-1,2-oxaphospholes by electrophilic cyclization reaction of phosphorylated α-hydroxyallenes.

This paper discusses a reaction of phosphorylated α-hydroxyallenes with protected or unprotected hydroxy groups involving 5-endo-trig cyclizations. Various electrophilic reagents such as sulfuryl chloride, bromine, benzenesulfenyl and benzeneselenenyl chlorides have been applied. The paper describes the reaction of 1-hydroxyalkyl-1,2-dienephosphonates with electrophiles that produces 2-methoxy-2-oxo-2,5-dihydro-1,2-oxaphospholes due to the participation of the phosphonate neighbouring group in the cyclization.

Bifunctionalized allenes. Part XIII. A convenient and efficient method for regioselective synthesis of phosphorylated α-hydroxyallenes with protected and unprotected hydroxy group.

The paper describes a convenient and efficient method for regioselective synthesis of phosphorylated α-hydroxyallenes using an atom economical [2,3]-sigmatropic rearrangement of intermediate propargyl phosphites or phosphinites. These can be readily prepared via reaction of protected alkynols with dimethyl chlorophosphite or chlorodiphenyl phosphine respectively in the presence of a base.

Comparative analysis of clastogen-induced chromosome aberrations observed with light microscopy and by means of atomic force microscopy.

Different types of chromosome aberration were observed in mouse bone-marrow cells after treatment with 4-bromo-N,N-diethyl-5,5-dimethyl-2,5-dihydro-1,2-oxaphosphol-2-amine 2-oxide (Br-oxaphosphole, Br-oxph) in a previous study. The aim of the present study is to perform a comparative analysis of these chromosomal damages observed with light microscopy (LM) and by means of atomic force microscopy (AFM). The kinds of aberrations scored by LM were substantially corrected by images at the ultrastructural level.

Cytotoxic and genotoxic effects of Br-containing oxaphosphole on Allium cepa L. root tip cells and mouse bone marrow cells.

The continuous production and release of chemicals into the environment has led to the need to assess their genotoxicity. Numerous organophosphorus compounds with different structures have been synthesized in recent years, and several oxaphosphole derivatives are known to possess biological activity. Such chemical compounds may influence proliferating cells and cause disturbances of the genetic material.

On the mechanism of stomatocyte-echinocyte transformations of red blood cells: experiment and theoretical model.

This study represents an attempt to achieve a better understanding of the stomatocyte-echinocyte transition in the shape of red blood cells. We determined experimentally the index of cell shape at various ionic strengths and osmolarities for native and trypsin-treated human erythrocytes. For every given composition of the outer phase, we calculated the ionic strength in the cells and the transmembrane electric potential using a known theoretical model.