Dimension and entropy analysis of MEG time series from human α-rhythm

Magnetoencephalograms (MEG) from human brain were measured by means of a 37 channel SQUID magnetometer (KRENIKON). Correlation integrals were calculated from time series exhibiting strong -rhythm in order to give estimates of correlation dimension andK ₂ entropy. The results are discussed regarding the length and the stationarity of the data. It is shown that low spurious correlation dimensions andK ₂-entropies may easily be obtained as artefacts due to time correlations in phase space and data length. When time correlations are avoided and the length of time series is taken into account, estimates of correlation dimension andK ₂ entropy indicate no evidence of the existence of low dimensionality.     

Reaction cross section measurements of the neutron-rich isotopes8,9,11Li at 80 MeV/nucleon

Total interaction cross sections have been measured for⁸Li on C and Pb targets, for⁹Li on C, Al, Cu, Sn and Pb targets as well as for¹¹Li on C, Sn and Pb targets. For each beam, we also used a plastic scintillator as target. The measurements with the scintillator targets are used to extract reduced nuclear radii of the lithium isotopes. These radii are then used for the calculation of the nuclear part of the total cross section for the other targets. The total electromagnetic-dissociation (EMD) cross sections have been deduced and are compared to different models. A strong target-charge-dependent EMD cross section is measured for¹¹Li reaching 2.96 _–0.82 ^+0.84 b for the Pb target. In the⁹Li case, a large EMD cross section for high-Z targets has been observed which amounts to 0.75 ± 0.45 b for the Pb target. The EMD cross sections of both,⁹Li and¹¹Li, may be understood by the giantdipole-resonance model.This work forms part of the PhD Thesis of B. Blank     

Proton microprobe analysis of interplanetary dust particles

Interplanetary dust particles (IDPs) are typically <10 μm in diameter and <10^?9 g in mass on collection. The Heidelberg proton microprobe (beam spot ?2 × 3 μm²) allows non-destructive detectio of trace elements in such samples. Two IDPs (Zodiac and Bounce) were examined. To evaluate the proton-induced x-ray spectra quantitatively, the x-ray production rates for thin samples were calculated with a computer routine; the elemental ratios of the samples normalized to silicon or iron were evaluated. The ratios found for the Zodiac sample agree within a factor of two with those of cosmic abundance. The other IDP showed depletion in Ca, K, Zn and S.     

Enantioselective synthesis of a mitosane core assisted by diversity-based catalyst discovery

[reaction: see text]. Synthesis of mitosane 1 in optically pure form is reported. A retrosynthetic plan that proceeds through racemic allylic alcohol 3 was carried out. This intermediate served as a test substrate for a rapid screen of a small library (152 members) of peptide-based kinetic resolution catalysts. Peptide 9 was found to effect kinetic resolution with k(rel) = 27. Alcohol (-)-3 was then converted to optically pure (-)-1 in eight steps.     

Stoffwechselprodukte von Mikroorganismen. 231. Mitteilung. Bafilomycin-A1-21-O-(α-L-rhamnopyranosid): Strukturaufklärung durch chemische Verknüpfung mit Bafilomycin A1 und Leucanicidin

Isolation of Bafilomycin-A₁-21-O-(α-L-rhamnopyranoside). Structural Determination by Chemical Correlation with Bafilomycin A₁ and Leucanicidin From cultures of an actinomycete strain, the known antifungal and insecticidal antibiotic leucanicidin ( 1 ) and a hitherto unknown antifungal antibiotic, bafilomycin-A₁-21-O-(α-L-rhamnopyranoside) ( 2 ), were isolated. The latter is spectroscopically closely related to 1 and bafilomycin A₁ ( 3 ) and gave degradation products identical with compounds obtained by analogous degradation of 1 and 3 .     

Localization of carboxyl groups at surface layer of carboxylated polymer emulsion particles by alkali treatment

For the purpose of localizing carboxyl groups from inside to particle surface, styrene — butyl acrylate — methacrylic acid (74.3/17.0/8.7, mol ratio) terpolymer emulsion was kept under pH 9 at different temperatures. The amount of carboxyl groups at the particle surface, As, was remarkably increased by the alkali-treatment above 35 °C. On the other hand, As value of the alkalitreated emulsion was decreased by keeping under ph 3 above 45 °C, although in the case of the original emulsion without the alkalitreatment, it was not changed by the acid-treatment. These results suggest that a part of polymer segments which have ionized carboxyl groups is dragged out at the surface by an increase in the affinity of the groups against water, and the dragged segments turn back into the inside again when the carboxyl groups are deionized.Part 97 of the series Studies on Suspension and Emulsion.     

Photochemical α-Cleavage of β, γ-Unsaturated Aryl Ketones: Competition between recombination/disproportionation and dissociation in geminate singlet and triplet radical pairs

The photolysis of (R)-(+)-phenyl and (R)-(+)-p-anisyl 1, 2, 3-trimethylcyclopent-2-enyl ketone ( 1 , 2 ) and the corresponding rac-1- and 3-desmethyl analogs ( 3 , 4 ) led to isomerization due to formal 1, 3 aroyl migration and to formation of aryl aldehydes ( 7 , 8 ), dienes ( 9 , 10 ) and dimers ( 5 , 6 ) of the cyclopentenyl radical. Evidence obtained from a chiroptical and mass spectrometric analysis of a crossing experiment and from photolytic CIDNP measurements including the use of CCl₄ as a free radical scavenger, supports the conclusion (1): that the ketones undergo photochemical α-cleavage predominantly in the triplet state; (2): that recombination and disproportionation reactions within the geminate singlet and triplet aroyl/allyl radical pairs ( 11 ) compete with the dissociation into free radicals ( 12 ): (3): that ketone isomerization by paths not involving polarizable radical intermediates is unimportant; (4): that no triplet oxa-di-π-methane type rearrangement products are formed.     

Catalytic Spectrophotometric Determination of Nanogram Amounts of Selenium(IV)

A method is proposed for the catalytic spectrophotometric determination of nanogram amounts of selenium(IV). The method is based on the reduction of nitrate with iron(II) ethylenediaminetetraacetate catalyzed by Se(IV) compounds. The reaction proceeds in several stages and yields iron(III) ethylenediaminetetraacetate, the nitrosyl complex of iron, nitrous acid, and other products. Nitrous acid enters into the diazotization reaction with aromatic amine. The resulting diazo compound is coupled with another aromatic amine to form the azo compound. 4-Nitroaniline is used as the diazo component, and N-diethyl-N-(1-naphthyl)ethylenediamine is used as the azo component. The molar absorptivity of the solution of the azo compound is 4.5 × 10⁴ at 540 nm. A kinetic method was developed for the determination of selenium(IV) in potable and natural waters with the use of the standard addition method. The detection limit of selenium by the proposed method is 0.1 ng/mL. In the determination of 0.2 and 2 ng/mL selenium, the relative standard deviation is 6 and 2%, respectively. The interfering effect of organic compounds dissolved in natural water is eliminated by the ultrasonic treatment of water samples.     

Partial charge-changing cross sections for neutron-deficient isotopes from58Ni fragmentation

At the projectile-fragment separator FRS of GSI, relativistic secondary beams of about 520 MeV/nucleon were produced by fragmentation of a primary beam of⁵⁸Ni at 650 MeV/nucleon in a beryllium target. By means of aE—B—TOF measurement, the fragments were identified and their charge-changing probabilities in targets of (CH₂) _n , C, Al, and Pb placed at the exit of the FRS were determined. Whereas a first article dealt with the total charge-changing cross sections, we describe in this second article the element distributions of these secondary fragments, which are found to depend strongly on the isospin of the secondary projectile as well as on the target material. In the case of the lead target, the influence of the electromagnetic dissociation is clearly visible in the one-proton and two-proton removal channels. The preference for the formation of even-Z fragments is much more pronounced for exotic secondary projectiles than for projectiles close to stability. Calculations with a geometrical abrasion-ablation model allow to understand the global features of the experimental data. However, far from stability, the discrepancies between calculations and experimental data increase.On leave of absence from Institute of Experimental Physics, University of Warsaw, PL-00-681 Warszawa, Hoa 69, Poland