Natella Mirzoyan | Weizmann Institute of Science (original) (raw)

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Papers by Natella Mirzoyan

European Journal of Lipid Science and Technology

Aquacultural Engineering, 2015

ABSTRACT

Geochemical Transactions, 2014

Pyrite is one of the most abundant and widespread of the sulfide minerals with a central role in ... more Pyrite is one of the most abundant and widespread of the sulfide minerals with a central role in biogeochemical cycles of iron and sulfur. Due to its diverse roles in the natural and anthropogenic sulfur cycle, pyrite has been extensively studied in various experimental investigations of the kinetics of its dissolution and oxidation, the isotopic fractionations associated with these reactions, the microbiological processes involved, and the effects of pyrite on human health. Elemental sulfur (S(0)) is a common product of incomplete pyrite oxidation. Preexisting S(0) impurities as unaccounted reaction products are a source of experimental uncertainty, as are adhered fine grains of pyrite and its oxidation products. Removal of these impurities is, therefore, desirable. A robust standardized pretreatment protocol for removal of fine particles and oxidation impurities from pyrite is lacking. Here we describe a protocol for S(0) and fine particle removal from the surface of pyrite by rinsing in acid followed by repeated ultrasonication with warm acetone. Our data demonstrate the presence of large fractions of S(0) on untreated pyrite particle surfaces, of which only up to 60% was removed by a commonly used pretreatment method described by Moses et al. (GCA 51:1561-1571, 1987). In comparison, after pretreatment by the protocol proposed here, approximately 98% S(0) removal efficiency was achieved. Additionally, the new procedure was more efficient at removal of fine particles of adhered pyrite and its oxidation products and did not appear to affect the particle size distribution, the specific surface area, or the properties of grain surfaces. The suggested pyrite pretreatment protocol is more efficient in removal of impurities from pyrite grains, and provides multiple advantages for both kinetic and isotopic investigations of pyrite transformations under various environmental conditions.

Journal of the World Aquaculture Society, 2012

Archives of Microbiology, 2014

Water, Air, & Soil Pollution, 2015

Journal of Animal Ecology, 2004

1Fleas Xenopsylla conformis and Xenopsylla ramesis parasitize the rodents Meriones crassus and Ge... more 1Fleas Xenopsylla conformis and Xenopsylla ramesis parasitize the rodents Meriones crassus and Gerbillus dasyurus. Previously reported isodar analysis of host selection suggested that at low density, X. conformis parasitizes M. crassus only, but with an increase in flea density, G. dasyurus is also parasitized. Xenopsylla ramesis at low density parasitizes both hosts equally, whereas at high density prefers M. crassus. The ultimate cause of underlying these patterns was suggested to be differential fitness reward of parasitism on a particular host species, while the mechanism can be adaptive host selection by fleas.2To justify the suggested fitness–density relations, we studied reproductive success in X. conformis and X. ramesis feeding on either M. crassus or G. dasyurus. We hypothesized that reproductive success would differ between two host species for each flea species.3Xenopsylla conformis parasitizing M. crassus produced more eggs than when parasitizing G. dasyurus, whereas time of oviposition and larval hatching did not depend on host species. In contrast, egg production in X. ramesis did not differ between host species. However, fleas fed on M. crassus needed fewer bloodmeals, oviposited earlier and hatching of their larvae took less time than those of fleas fed on G. dasyurus.4Patterns of egg production and development time in both fleas were consistent with the hypothesis that their between-host distribution arose from adaptive host selection strategy.Fleas Xenopsylla conformis and Xenopsylla ramesis parasitize the rodents Meriones crassus and Gerbillus dasyurus. Previously reported isodar analysis of host selection suggested that at low density, X. conformis parasitizes M. crassus only, but with an increase in flea density, G. dasyurus is also parasitized. Xenopsylla ramesis at low density parasitizes both hosts equally, whereas at high density prefers M. crassus. The ultimate cause of underlying these patterns was suggested to be differential fitness reward of parasitism on a particular host species, while the mechanism can be adaptive host selection by fleas.To justify the suggested fitness–density relations, we studied reproductive success in X. conformis and X. ramesis feeding on either M. crassus or G. dasyurus. We hypothesized that reproductive success would differ between two host species for each flea species.Xenopsylla conformis parasitizing M. crassus produced more eggs than when parasitizing G. dasyurus, whereas time of oviposition and larval hatching did not depend on host species. In contrast, egg production in X. ramesis did not differ between host species. However, fleas fed on M. crassus needed fewer bloodmeals, oviposited earlier and hatching of their larvae took less time than those of fleas fed on G. dasyurus.Patterns of egg production and development time in both fleas were consistent with the hypothesis that their between-host distribution arose from adaptive host selection strategy.

Fems Microbiology Letters, 2006

Escherichia coli G35 N49 strain, from the gut of breast cancer patients, in comparison with the E... more Escherichia coli G35 N49 strain, from the gut of breast cancer patients, in comparison with the E. coli G35 N61 strain, from the gut of healthy people, shows in vitro reduction in growth rates and maximal growth yield. The changes in certain membrane characteristics, such as low membrane potential and disturbance in intramembrane interaction of H+-ATPase F0F1 with the TrkA system, indicate a dysfunction in ion transport and enzymatic activity. These changes can be detected during fermentation and in anaerobic conditions (in the gut, for example) and may be influenced by unfavorable conditions in the gut of cancer patients.

Current Opinion in Biotechnology, 2010