DFT studies of the molecular nanomagnet Fe 8 and the V 15 spin system

Based on first-principles all-electron density-functional calculations we report the electronic structure and magnetic ordering of the molecular magnet Fe₈ and the V₁₅ spin system. The ferrimagnetic ordering with total spin S = 10 of the eight iron atoms in the Fe₈ cluster agrees well with experimental results from polarized neutron data. In comparison the low spin system V₁₅ shows a spin S = 1/2 ground state which is also found from our calculations. Received 30 October 2000     

Working group report: Heavy-ion physics and quark-gluon plasma

This is the report of Heavy Ion Physics and Quark-Gluon Plasma at WHEPP-09 which was part of Working Group-4. Discussion and work on some aspects of quark-gluon plasma believed to have created in heavy-ion collisions and in early Universe are reported.     

Gas-phase deprotonation of arylalkylamines. A collision-induced dissociation study

The collision-induced dissociation (CID) of deprotonated arylalkylamines of general formula R(1)C(6)H(4)CHR(2)CH(2)NR(3)(2) (where R(1) = H, OH, F or NO(2); R(2) = H or OH; R(3) = H or CH(3)) generated by negative chemical ionization with H(2)O and D(2)O as ionizing reagents, is discussed. The negative chemical ionization mass spectra show that, in the absence of a hydroxy group in the aromatic ring, deprotonation takes place at the benzylic position whereas the proton is lost from the OH group when present. The nitro compound forms only M(-.) ions. The CID spectra of the deprotonated molecules show that fragmentations are strongly dependent on the structural features of the molecules, namely the presence or absence of substituents in the aromatic ring or aliphatic chain. Copyright 1999 John Wiley & Sons, Ltd.     

Astrophysical S-factors from asymptotic normalization coefficients

S-factors for direct capture reactions can be found at astrophysical energies from asymptotic normalization coefficients which provide the normalization of the tail of the overlap function. For example the overlap for ⁸B → ⁷Be+p defines the S-factor for ⁷Be (p, γ)⁸B. Peripheral transfer reactions offer a technique to determine these asymptotic normalization coefficients. As a test of the technique, the ¹⁶O(³He, d)¹⁷F reaction has been used to determine asymptotic normalization coefficients for transitions to the ground and first excited states of ¹⁷F. The S-factors for ¹⁶O(p, γ)¹⁷F calculated from these ¹⁷F → ¹⁶O+p asymptotic normalization coefficients are found to be in very good agreement with recent measurements. Following the same technique, the ¹⁰B(⁷Be, ⁸B)⁹Be and ¹⁴N(⁷Be, ⁸B)¹³C reactions have been used to measure the asymptotic normalization coefficient for ⁷Be(p, γ)⁸B. This result provides an indirect determination of S ₁₇(0).     

Isolation of NO(3)(-)-N as 1-phenylazo-2-naphthol (Sudan-1) for measurement of delta(15)N

The conversion of nitrate (NO(3)(-)) to 1-phenylazo-2-naphthol (Sudan-1) has been examined as a method for natural abundance measurement of delta(15)N of NO(3)(-). The reaction results in dilution of NO(3)(-)-N with only one reagent-derived N and the product is readily concentrated from dilute samples by reverse phase chromatography. There is systematic isotopic fractionation during the reaction, but this can be allowed for by analysing known NO(3)(-) standards along with each sample set. Sudan-1 prepared from surface water samples containing approximately 50 &mgr;g NO(3)(-)-N can be analysed by automated continuous flow isotope ratio mass spectrometry with a precision of 0.2 per thousand (one standard deviation) and the accuracy is not affected by interference from other nitrogenous species in the sample or reagents. Copyright 1999 John Wiley & Sons, Ltd.     

Methods for removal of residual catalyst from polymers prepared by ring opening metathesis polymerization

Methods for removing the residual Grubbs' third generation catalyst from polymers prepared by ring opening metathesis polymerization are reported. Two strategies were investigated for reduction of the residual catalyst in the final polymer product. The first strategy involved the use of heterogeneous functionalized particles to scavenge the catalyst from the solution. Filtration of the particles followed by precipitation produced polymers with 10–60 ppm residual catalyst, depending on the type of particle used, surface functional groups, and number of equivalents. The second strategy used small organic molecules that could coordinate to the metal species and modify the solubility of the catalyst, facilitating partitioning of the catalyst into the precipitation solvent. Several types of molecules with varied functionality reduced the residual catalyst level to 30–120 ppm, depending on the loading. Hydrogenation of the polymer backbone followed by precipitation lowered the residual Ru content from 195 ppm to 10 ppm, suggesting that the difficulty of completely removing the catalyst could be a result of coordination of the metal species to the double bonds in the polymer backbone. Reducing the amount of trace catalyst significantly improved the oxidative stability of the polymer. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2010     

On essential entropy-carrying sets

In this paper we study properties of essential entropy-carrying sets of a continuous map on a compact metric space. If f:X→X$f:X\to X$ is continuous on a compact metric space X, then the intersection of all essential entropy-carrying sets of f may or may not be an essential entropy-carrying set of f  . When this intersection is an essential entropy-carrying set we denote it by E(f)$E(f)$, the least essential entropy-carrying set, otherwise we say that E(f)$E(f)$ does not exist. We present an example where E(f)$E(f)$ does not exist but also find a sufficient condition for E(f)$E(f)$ to exist. If f   is a piecewise monotone map, we show that E(f)$E(f)$ exists and is the finite union of the entropy-carrying sets in the Nitecki Decomposition of the nonwandering set of f intersected with the closure of the periodic points of f  . When E(f)$E(f)$ exists we study how it relates to other entropy-carrying sets of f including subsets of itself.