Accelerated electrons and hard X-ray emission from X-pinches

The generation of accelerated electrons in the X-pinch minidiode is studied experimentally. It is well known that the explosion of an X-pinch consisting of two or more wires is accompanied by the formation of a minidiode, in which electrons are accelerated. The subsequent slowing down of electrons in the products of wire explosion causes the generation of hard X-ray (HXR) emission with photon energies higher than 10 keV. In this work, the spatial and temporal characteristics of X-pinch HXR emission are studied, the specific features of HXR generation are discussed, and the capability of applying this radiation to point-projection X-ray imaging of various plasma and biological objects is considered. The parameters of the electron beam produced in the X-pinch are measured using a Faraday cup and X-ray diagnostics. The experiments were performed with the XP generator (550 kA, 100 ns) at Cornell University (United States) and the BIN generator (270 kA, 150 ns) at the Lebedev Physical Institute (Russia).     

Lysine decarboxylase activity as a factor of fluoroquinolone resistance in <Emphasis Type="Italic">Escherichia coli</Emphasis>

Exposure of E. coli cells to sublethal concentrations of fluoroquinolones induced synthesis of lysine decarboxylase LdcC, which was previously considered to be a constitutive enzyme. Under these conditions, a key role in this process is played by RNA polymerase σ ^S subunit (RpoS); its quantity increased substantially in the presence of antibiotics. Fluoroquinolones of the second and third generations had a more pronounced effect on rpoS expression and LdcC activity than the first-generation antibiotics. A direct correlation was shown between the level of cadaverine, the product of lysine decarboxylase reaction in E. coli cells, and their resistance to fluoroquinolones. An increase in endogenous cadaverine reduced effectiveness of the second and third-generation fluoroquinolones, but had no effect on antimicrobial activity of the first-generation antibiotics. This is in good agreement with the hydrophilic properties of antibiotics of different generations and, consequently, with different mechanisms of their penetration into bacterial cells.     

Effect of M and N-cholinoblockers on the excitability of the dorsal hippocampus in acute alcoholic intoxication

It has been established in chronic experiments on rabbits that acute alcohol intoxication increased the after-discharge thresholds in response to electrical stimulation of dorsal hippocampus. It has been shown that neurotropic agents selectively blocking M- or N-cholinoceptors exerted various effects. M-cholino-blocker methamizol (1 mg/kg, i. p.) decreased the excitability of dorsal hippocampus, potentiated EEG and behavioural effects of alcohol intoxication. N-cholinoblocker etherophen (IEM-506, 20 mg/kg, i. p.), on the contrary, increased the excitability of dorsal hippocampus and reduced behavioural effects of alcohol administration.     

Nutrition of the Red Fox (Vulpes vulpes) in Bol’shekhekhtsirskii Nature Reserve and Its Environs (Southern Part of the Amur River Region)

Biology Bulletin - The diet of the red fox (Vulpes vulpes L. 1758) was studied in the years 1990–1993, 1996–2000, and 2005–2013 in Bol’shekhekhtsirskii State Nature Reserve...     

Role of the energy status of Escherichia coli in cell membrane phospholipid composition changes during aerobic-anaerobic transitions]

The aerobic to anaerobic transition of E. coli is accompanied with interrelated changes of the adenylate pool, energy charge, respiration rate, as well as the phospholipid content of the cell membranes and the activity of the polyamine synthesizing system. The role of the cellular energy status in the control of the relative content of membrane phospholipids is discussed. The control is based either on energy redistribution in phospholipid metabolism or on the effect on the activity of the polyamine synthesizing system.