Annihilation of positrons from AGN jets as a possible source of cosmic gamma-ray background at energies below 511 keV

The origin of the diffuse gamma-ray background in the range from hundreds keV to several MeV is not known conclusively. From current models and observations it is believed that, at least partially, this background is formed by blazars and remnants of supernovae (SN) of type Ia in distant galaxies. However, these contributions are not sufficient to reproduce the observed level of the signal. In this work we propose another source which could contribute to this background, namely the jets of active galactic nuclei (AGN). The composition of jets is not known, but there are observational hints that the fraction of positrons there is substantial. Positrons are partially evacuated to the intergalactic medium and partially mix with the circumgalactic medium and annihilate there comparatively quickly. Using the AGN luminosity function, we estimated the positron production rate and the contribution of the positron annihilation to the cosmic background below 511 keV. We also estimated the analogous contribution from positron annihilation within SN Ia remnants in distant galaxies. The contribution of AGNs is estimated to be a factor of 5 - 10 smaller than the observed background intensity, and the contribution from SNe is yet smaller by one order of magnitude. Nevertheless, the contribution of AGNs appeared to be larger than the contribution of blazars estimated from Swift-BAT and Fermi-LAT observations. The main uncertainty in our model is the fraction of positrons remaining in the circumgalactic medium which makes our estimation an upper limit.Comment: 9 pages, 2 figure

Carboxylated photoswitchable diarylethenes for biolabeling and super-resolution RESOLFT microscopy.

Reversibly photoswitchable 1,2-bis(2-ethyl-6-phenyl-1-benzothiophene-1,1-dioxide-3-yl)perfluorocyclopentenes (EBT) having fluorescent "closed" forms were decorated with four or eight carboxylic groups and attached to antibodies. Low aggregation, efficient photoswitching in aqueous buffers, specific staining of cellular structures, and good photophysical properties were demonstrated. Alternating light pulses of UV and blue light induce numerous reversible photochemical transformations between two stables states with distinct structures. Using relatively low light intensities, EBTs were applied in biology-related super-resolution microscopy based on the reversible saturable (switchable) optical linear fluorescence transitions (RESOLFT) and demonstrated optical resolution of 75 nm

Development of methods of phosphorylation of citral by medial and acidic phosphites

The reactions of trimethyl phosphite with citral in the presence of acetic acid, triphenyl phosphite with citral in the presence of water and trimethyl phosphite with citral in the presence of water and triethylamine in the methanol solution were studied. On the basis of these studies, dienyl 1-hydroxyphosphonates were obtained. A convenient method of synthesizing unsaturated 1-hydroxyphosphonates was developed on the basis of reaction of dialkyl phosphites with citral in the presence of triethylamine in molar ratio 4:2:8 in alcohol solutions

Carboxylierte photoschaltbare Diarylethene als Biomarkierungen für hochauflösende RESOLFT-Mikroskopie.

Reversibel photoschaltbares 1,2-Bis(2-ethyl-6-phenyl-1-benzothiophen-1,1-dioxid-3-yl)perfluorcyclopenten (EBT) mit fluoreszierender “geschlossener” Form wurde mit vier oder acht Carboxygruppen versehen und an Antikörper gebunden. Die carboxylierten Derivate wiesen geringe Aggregation, effizientes Photoschalten in wässrigen Puffern, gezieltes Färben von zellulären Strukturen und gute photophysikalische Eigenschaften auf. Abwechselnde Bestrahlung mit UV und blauem Licht relativ geringer Intensität führte zu reversibler photochemischer Isomerisierung zwischen zwei stabilen Strukturen über mehrere dutzend Schaltzyklen. Dies ermöglichte die Verwendung der Farbstoffe für hochauflösende RESOLFT-Mikroskopie (“reversible switchable optical linear fluorescence transitions”). Hierbei konnte eine optische Auflösung von 75 nm an zellulären Tubulin-Filamenten erzielt werden

Novel effectively carbonaceous and sulfurated hydrogen corrosion inhibitors on the basis of organosulfurphosphorus compounds

Novel ammonium salts of O,O-dialkyl dithiophosphoric acids were obtained by one-pot synthesis from white phosphorus, elemental sulfur, industrial alcohols or phenols, and amines. Long-chain S-alkyl O,O-dialkyldithiophosphonates were prepared by the reaction of red phosphorus with elemental sulfur, alcohols, and the cheap industrial fractions of C16-C18 and C 20-C26 of higher α-olefins in the presence of Lewis acid catalyst. The dithiophosphates obtained possess the high anticorrosion activities toward mild steel. © 2013 Copyright Taylor and Francis Group, LLC