Application of the program LISE to fusion-evaporation

A new fusion-evaporation model LisFus for fast calculation of fusion residue cross sections has been developed in the framework of the code LISE. This model can calculate very small cross sections quickly compared to programs using the Monte Carlo method. Such type of the fast calculations is necessary to estimate fusion residue yields. Using this model, the program LISE now has the possibility of calculating the transmission of fusion residues through a fragment separator. It is also possible to use fusion residue cross sections calculated by the program PACE, which has been incorporated in the LISE package. The code PACE is a modified version of JULIAN—the Hillman-Eyal evaporation code using a Monte Carlo code coupling angular momentum. A comparison between PACE and the LisFus model is presented.     

SUPEROXIDE DISMUTASE AS AN AMPLIFIER OF THE CHEMICAL REACTIVITY OF PORPHYRIN RADICAL-CATIONS

Abstract— Porphyrin radical-cations have been produced using laser flash photolysis via oxidation of the porphyrin triplets by metronidazole. This radical-cation reacts with OJ as shown by its increased half-life in the presence of native superoxide dismutase. Comparable results are obtained when porphyrin radical-cations are formed by Br₂^-O₂^-oxidation of porphyrins produced in pulse radiolysis of oxygen-saturated aqueous solutions containing 20 mM Br^-O^-. These results provide an explanation for the enhancement by superoxide dismutase of the photosensitizing capacity of porphyrins in the presence of electrophilic nitroimidazoles (Bazin and Santus, 1986). They may also apply to porphyrin radical-cations formed by monophotonic or biphotonic photoionization processes.     

Amino acid-pyrrole N-conjugates; a new class of antioxidants II. Effectiveness of singlet oxygen quenching by luminescence measurements

The pyrrole-amino acid and peptide N-conjugates synthesized from tyrosine, histidine and glutathione very effectively quench the 1270 nm singlet oxygen luminescence, at rates ranging from 10⁸ to 10⁹ M⁻¹ s⁻¹. Nuclear magnetic resonance spectroscopy suggests that the electron-donating properties of the methyl groups after 2,5-dimethyl substitution on the pyrrole ring are probably an important determinant of the reactivity of singlet oxygen with the N-conjugate of glutathione. However, intramolecular interactions between the pyrrole ring and the side chain may also modulate the reactivity of the antioxidant as suggested by absorption and fluorescence spectroscopies carried out on tyrosine derivatives. Efficient fluorescence quenching of the phenol ring by the pyrrole ring occurs in the tyrosine derivatives. The reactivities of these antioxidants with ¹O₂ are comparable in methanol, ethanol and D₂O.     

Aligning Text and Phonemes for Speech Technology Applications Using an EM-Like Algorithm

A common requirement in speech technology is to align two different symbolic representations of the same linguistic ‘message’. For instance, we often need to align letters of words listed in a dictionary with the corresponding phonemes specifying their pronunciation. As dictionaries become ever bigger, manual alignment becomes less and less tenable yet automatic alignment is a hard problem for a language like English. In this paper, we describe the use of a form of the expectation-maximization (EM) algorithm to learn alignments of English text and phonemes, starting from a variety of initializations. We use the British English Example Pronunciation (BEEP) dictionary of almost 200,000 words in this work. The quality of alignment is difficult to determine quantitatively since no ‘gold standard’ correct alignment exists. We evaluate the success of our algorithm indirectly from the performance of a pronunciation by analogy system using the aligned dictionary data as a knowledge base for inferring pronunciations. We find excellent performance—the best so far reported in the literature. There is very little dependence on the start point for alignment, indicating that the EM search space is strongly convex. Since the aligned BEEP dictionary is a potentially valuable resource, it is made freely available for research use.     

A laser flash photolysis and pulse radiolysis study of primary photochemical processes of flumequine

The 355 nm laser flash photolysis of argon-saturated pH 8 phosphate buffer solutions of the fluoroquinolone antibiotic flumequine produces a transient triplet state with a maximum absorbance at 575 nm where the molar absorptivity is 14,000 M(-1) cm(-1). The quantum yield of triplet formation is 0.9. The transient triplet state is quenched by various Type-1 photodynamic substrates such as tryptophan (TrpH), tyrosine, N-acetylcysteine and 2-deoxyguanosine leading to the formation of the semireduced flumequine species. This semireduced form has been readily identified by pulse radiolysis of argon-saturated pH 8 buffered aqueous solutions by reaction of the hydrated electrons and the CO2*- radicals with flumequine. The absorption maximum of the transient semireduced species is found at 570 nm with a molar absorptivity of 2,500 M(-1) cm(-1). In argon-saturated buffered solutions, the semireduced flumequine species formed by the reaction of the flumequine triplet with TrpH stoichiometrically reduces ferricytochrome C (Cyt Fe3+) under steady state irradiation with ultraviolet-A light. In the presence of oxygen, O2*- is formed but the photoreduction of Cyt Fe3+ by O2*- competes with an oxidizing pathway which involves photo-oxidation products of TrpH.     

IS RHODAMINE 123 A PHOTOSENSITIZER?

Because of conflicting reports on the photoxicity of rhodamine 123 (Rh 123), we have undertaken a study of Rh 123 photosensitization in several in vitro systems. First, Rh 123 is not a photodynamic agent and does not react with singlet oxygen. Second, when bound to cytochrome c (Cyt c), Rh 123 photosensitizes ferro Cyt c but not ferri Cyt c degradation by an oxygen-independent process. When delivered to skin fibroblasts where it specifically stains mitochondria, Rh 123 photosensitizes membrane damage. These results are consistent with the hypothesis that Rh 123 is a phototoxic stain. The lack of photosensitivity of Rh 123-stained mitochondria in some cell lines might therefore be due to specific structural features.     

Z = 50 shell gap near 100Sn from intermediate-energy Coulomb excitations in even-mass 106-112Sn isotopes

Rare isotope beams of neutron-deficient 106,108,110Sn from the fragmentation of 124Xe were employed in an intermediate-energy Coulomb excitation experiment. The measured B(E2,0(1)(+)-->2(1)(+)) values for 108Sn and 110Sn and the results obtained for the 106Sn show that the transition strengths for these nuclei are larger than predicted by current state-of-the-art shell-model calculations. This discrepancy might be explained by contributions of the protons from within the Z = 50 shell to the structure of low-energy excited states in this region.