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The article describes a new detector, a volume filled with hexane at low pressure (3 Torr), containing multi-wire proportional chambers and a silicon semiconductor detector. Using this setup, alpha particles emitted during the decay of the radioactive isotope 226Ra were detected. The device has an energy resolution of ≤ 5% and allows measuring the ionization energy losses of alpha particles as well. Thus, the LPMWPC and SSD-based experimental setup is a good tool for studying both binary and ternary fission of heavy nuclei, in which the third fragment is a high-energy alpha particle. [ABSTRACT FROM AUTHOR]

An active target has been developed for studying the Hoyle like states in 16O. It is a position and time sensitive detector system based on the Low-Pressure Multy-Wire Proportional Chamber (LPMWPC) technique and Si detectors. The few Torr pressure of methyl ((OCH3)2CH2) serves as a working gas for the LPMWPC operation, and the oxygen atoms of the methyl molecules serve as an experimental target. The main advantage of this new target-detector system is a high sensitivity to the low-energy, highly ionizing particles, produced after photodisintegration of 16O, and the insensitivity to the γ-rays and low ionizing particles, which allows one to detect only the products of the nuclear reaction, which are studied. The threshold energies for detection of α particles and 12C nuclei are about 50 keV and 100 keV, respectively. Temporal and positional resolution of the LPMWPC modules was investigated with the use of the α-particle source. This paper discusses the architecture of the active target and the test results of the prototype MWPC detector. This installation has been constructed to study the cluster states at 15.1 MeV in 16O using the proton beams from the Yerevan proton cyclotron and the Compton backscattered photon beams of the ELI-NP facility. [ABSTRACT FROM AUTHOR]

The modern state of microbiological community of Lake Sevan pelagic water is characterized. We analyzed the data using methods accepted in hydrobiology. The tendencies of saprophytes and cyanobacteria total amount correlation changes within the water column of the lake were studied. Decreasing bacterial number over last years (2009-2010) in Lake Sevan waters was established. The comparatively high bacteria consist within surface and bottom layers of lake water column were noticed. Cyanobacterial community structure was examined. The dominance of certain cyanobacterial taxa was shown over the entire period of investigations. The highest values of cyanobacterial abundances were observed for surface or bottom layers mainly in late summer season. The possible impact of cyaonobacterial blooms on saprophytes development was assessed over the last years (2005-2010) in Lake Sevan waters. Our investigations have revealed no significant relationship between saprophytes and cyanobacterial composition over the entire period of study. Neither seasonal no depths relation was observed, except for some months and depths when observed certain positive or negative interaction was not considered as a relationship existence. In conclusion, negative or positive relationship observed between those microbial groups, at least in midsummer, those interactions seemed to be associated with either sufficient nutrition upload or temperature gradient. [ABSTRACT FROM AUTHOR]

Studies the relationships between bacterial and cyanobacterial populations in the Lake Sevan main tributaries waters were carried out during spring-summer period of 2011. It was observed that bacterial population has had a similar tendency of growth, thus, in the spring bacterial abundance was low with significant or maximal picks in April associated with flooded period. In the late spring and early summer bacterial counts were increasing and reached greater numbers by the end of summer. The cyanobacterial massive proliferation has had tendency to have low counts in spring and to increase their numbers in summer. Considering the relationship between bacterial and cyanobacterial populations it cannot be said with certainty, however, whether or not an actual suppression takes place in the open waters of the Lake Sevan tributaries or any other factor can be an explanation of those changes. [ABSTRACT FROM AUTHOR]