Estimation of the Fragmentation Effect in the Registration of Superheavy Nuclei of Galactic Cosmic Rays in Pallasites

Journal of Experimental and Theoretical Physics - We report on the results of model calculations for estimating the fragmentation effect in the registration of heavy and superheavy nuclei of...     

Surface area controlled heterogeneous nucleation

Heterogeneous nucleation of liquid from a gas phase on nanoparticles has been studied under various saturation ratios and nuclei size. The probability of liquid droplet nucleation, especially at a low degree of deviation from equilibrium, was measured for both atmospheric aerosol particles and engineered nanoparticles Cr(2)O(3). The concept of a critical saturation ratio and the validity of the one-to-one relationship between the nuclei number and the number of droplets were examined. A transient zone between no nucleation and established nucleation termed the surface area controlled nucleation was observed. In this zone, the probability of stable phase formation is determined by the surface area of nuclei. There are two distinctive features of the surface area controlled nucleation: the nucleation probability is much less than 1 and is proportional to the surface area of nuclei. For condensation particle counters (CPCs) counting nanoparticles, these features mean that counts measured are proportional to the surface area of nanoparticles and, therefore, the CPCs counts can be calibrated to measure the surface area.     

Estimation of the properties of an energy-dispersive X-ray fluorescence spectrometer based on a composite double-layer detector

A mathematical model of double-layer Si-Ge and Si-AsGa energy-dispersive detectors of X-rays based on the analysis of processes of radiation and electron transfer in the detector is proposed along with a model of an energy-dispersive X-ray fluorescence spectrometer on the basis of this detector. The probabilities of recording of photons in different sections of the detector response function are calculated using the Monte-Carlo technique. It is shown that, in using an anticoincidence circuit and a Si detector as the first layer and Ge or AsGa detectors as the second layer, a detector with improved characteristics can be obtained, namely, the suppressed loss peaks of Ge or As and Ga and the efficiency of detection at the high radiation energy close to that of the Ge or AsGa detector. This detector in the energy-dispersive X-ray fluorescence spectrometer in some cases allows the reduction of the background level.     

N-Heterocyclic Carbenes: V. Synthesis of imidazolium salts from lupane series

By the reaction of N-alkyl- and N-arylimidazoles with 30-bromo-3,28-diacetoxylup-20(29)-ene a series was synthesized of unsymmetrically substituted chiral imidazolium bromides with a lupane fragment.     

Direct heterocyclization of benzocrown ethers

The synthesis of novel 3,3‐dialkyl‐3,4‐dihydroisoquinoline derivatives via direct heterocyclization of benzocrown ethers is described. © 2005 Wiley Periodicals, Inc. Heteroatom Chem 16:192–195, 2005; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/hc.20092     

Trigger System of the NUCLEON Experiment

Physics of Particles and Nuclei Letters - The NUCLEON experiment is aimed at measuring the spectrum and the elemental composition of cosmic rays (CR) in the 1011–1015 eV energy range. The...     

A bi-Bayesian procedure with constraints on prior refusal probability

Translated from Issledovaniya po Prikladnoi Matematike, No. 11, Part 2, pp. 39–43, 1984. Presented at the seminar of the Department of Probability Theory and Mathematical Statistics, NIIMM, October 15, 1981.     

Cathode strip chamber for CMS ME1/1 endcap muon station

Seventy-six serial ME1/1 cathode strip chambers have been produced in Dubna. These chambers are the coordinate detectors of the first muon station of the CMS detector at CERN. This paper describes the design of the chamber, its main mechanical parameters, and the results of the cosmic ray test. The text was submitted by the authors in English.     

Tandem Hydroformylation–Acetalization Using a Water-Soluble Catalytic System: a Promising Procedure for Preparing Valuable Oxygen-Containing Compounds from Olefins and Polyols

Specific features of the tandem hydroformylation–acetalization of a series of unsaturated compounds and polyols in the presence of a water-soluble catalytic system containing a rhodium catalyst precursor, sodium (triphenylphosphino)trisulfonate, and sulfuric acid were studied. The process parameters (component ratio, temperature, reaction time) were optimized using model substrates. With the suggested catalytic system, the conversion of unsaturated compounds to target products, acetals, reaches 95%, and the catalytic system can be separated from the reaction products and repeatedly used without significant loss of the activity. The acetal preparation procedure is versatile with respect to the raw materials. Batches of acetal mixtures were prepared by the suggested procedure from 1-octene and polyols (ethylene glycol, glycerol, sorbitol).