Records in the Fα-scheme. II. Limit laws

Limit theorems for the number of records in a sequence of independent nonidentically distributed random variables are obtained. A generalization of the so-called F^α-scheme is given. Bibliography: 4 titles. Translated fromZapiski Nauchnykh Seminarov POMI, Vol. 216, 1994, pp. 42–51. Translated by A. Sudakov.     

Role of Na(+)-Ca2+ exchange system in the pathogenesis of myocardial ischemia-reperfusion damage

Results from a systematic experiment on isolated perfused rat heart and isolated myocytes of adult rat showed that the mechanism of calcium influx during myocardial ischemia-reperfusion is due to the development of intracellular sodium overload during ischemic period; on reperfusion, the high intracellular Na+ content activated the reverse direction of Na(+)-Ca2+ exchange over myocardial sarcolemma (SL), thus a large quantity of extracellular Ca2+ fluxed over the SL to the intracellular space, forming a condition of intracellular Ca2+ overload, which leads to irreversible damage of the myocardium.     

Wave attenuation in an elastic medium

This article examines the propagation of viscoelastic (elastic) waves in a medium consisting of two layers of finite thickness. It is found that there is a mechanical effect manifest in the monotonic dependence of the damping factor on the parameters of the system. These dependences have distinct maxima and minima, thus making it possible to optimize the damping properties of systems by varying their geometric parameters.Translated from Dinamicheskie, Sistemy, No. 4, pp. 57–62, 1985.     

Synthesis of 4H-pyrans by O-cyclization of 1,5-diketones

Substituted 4H-pyrans were obtained in high preparative yields by the reaction of 1,5-diketones with acetic anhydride and boron trifluoride etherate in diethyl ether. It is assumed that the heterocyclization of 1,5-diketones includes a step involving the formation and transformations of an acyloxy carbonium ion.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 3, pp. 320–322, March, 1992.     

Magnetopause plasma transients: mapping into the auroral ionosphere

Attention is focused on a specific category of auroral event occurring predominantly during a southward directed interplanetary magnetic field (IMF). Coordinated observations from the ground and satellites in polar orbit have been used to study the temporal/spatial development of the events in relation to the background patterns of particle precipitation and ionospheric convection as well as the field-aligned current and ion drift characteristics of the individual events. Both prenoon and postnoon sector events are reported. In one case the auroral event was observed near the zero point potential line separating the morning and postnoon convection cells. The available data indicate that this auroral event sequence is a signature of quasi-periodic bursts of particle entry from the magnetosheath along flux tubes convecting into the polar cap, representing structures of enhanced IMF B_Y-related convection poleward of the persistent cleft aurora. Such events may be initiated by localized patches of enhanced merging rate at the dayside magnetopause     

A novel derivatization method for peptides to increase sensitivity and backbone fragmentation in liquid secondary-ion mass spectra.

Derivatization is used to increase both negative-ion sensitivity and positive-ion sequence information in the liquid secondary-ion mass spectra (LSIMS) of a series of peptides. The derivatization method involves acylation with pentafluorobenzoyl fluoride in a single-step reaction, and the reaction mixture is applied directly to the probe tip for analysis. Acylation takes place at the unprotected N-terminus, tyrosine, and lysine. The derivatives exhibit increased signal-to-noise ratio for [M-H]- ions, especially where there is not already an acidic amino acid residue in the peptide. In positive-ion LSIMS, the N-terminal group acts to retain the charge at the N-terminus, simplifying the fragmentation by producing N-terminal fragment ions. It also increases positive-ion fragmentation, sometimes very dramatically, making sequence determination more straightforward. The simplicity of the process, together with the enhancements it provides, make this a generally useful method for obtaining peptide structural information.     

Nitroazines. 20. Simple syntheses of nitropyrazolopyridines from aliphatic nitrosynthons and aminopyrazoles

Two variants of a synthesis for nitropyrazolopyridines from aminopyrazoles and two- or three-carbon nitrosynthons are examined.For Communication 19 see [1].Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 11, pp. 1560–1564, November, 1992.     

Measurement of the transverse Doppler shift using a stored relativistic7Li+ ion beam

We have performed for the first time precision spectroscopy on a coasting fast⁷Li⁺ ion beam in a storage ring. The ion beam moving with 6.4% speed of light was first electron cooled and then merged with two counterpropagating laser beams acting on two different hyperfine transitions sharing a common upper level (λ-system). One laser was frequency locked to thea ₃ ¹²⁷J₂ hfs frequency component established as a secondary frequency standard at 514 nm. The second laser was tuned over theλ-resonance, which was recorded relative to¹²⁷J₂ hfs components. This experiment is sensitive to the time dilation in fast moving frames and will lead to new limits for the verification of special relatively. The present status of the experiment and perspectives in accuracy are discussed.