4,357 research outputs found
Possible Applications of Modern Heuristics to the Assignment of Dense Molecular Spectra
No full textG. Moruzzi, Li-Hong Xu, R. M. Lees, B. P. Winnewisser and M. Winnewisser, J. Mol. Spectrosc., 167, 156-175 (1994). W. L. Meerts, J. A. Hageman, R. Wehrens, L. M. C. Buydens and R. de Gelder, 55th Ohio State University International Symposium on Molecular Spectroscopy, June 12-16, 2000, MI03.Author Institution: Dipartimento di Fisica ``Enrico Fermi'', dell'Universit\`{a} di Pisa and INFMThe assignment of dense rovibronic spectra has constituted for years, and continues to constitute, a great challenge to the molecular spectroscopist. This is particularly true when the selection rules of the molecule are not very stringent, and in the presence of large-amplitude vibrational modes. The availability of powerful desktop computers has lead to the development of interactive assignment methods, like the use of spreadsheets and the Ritz , and, more recently, to the first attempts to completely automate the interpretation of these spectra. Independently, during the last four decades there has been a growing interest in algorithms which rely on analogies to natural processes. These include, notably, simulated annealing, neural networks, genetic algorithms and ant algorithms. Most of these algorithms can solve complex maximization/minimization problems, notably minimization. A first application of genetic algorithms to molecular spectroscopy was presented by W. L. at this conference two years ago. In this contribution we discuss the possibility of exploiting one of the origins of the spectral complexity, namely the presence of non-stringent selection rules, for assigning a spectrum by minimizing the number of levels compatible with a given set of spectral lines (combinatorial minimization). Some preliminary results on artificial sets of more than 2 000 lines will be presented. The effects of experimental accuracy, and the possibility of searching for constrained minima, will be discussed
Vibrationally Excited Level Identification and FIR Laser Line Prediction by the "Ritz" and "LaseRitz" Programs
No full text G. Moruzzi and Li-Hong Xu, Ohio State University 49th International Symposium on Molecular Spectroscopy, TD04, p. 122 (1994).Author Institution: Università di Pisa, Piazza Torricelli 2, I-56100 Pisa, Italy; National Institute of Standards and Technology, Gaithersburg, MD 20899 U.S.A.Following last year's Columbus , we have continued our work on an interactive computer program for automating assignment of the Fourier-Transform methanol spectrum. Two new features have been developed. (1) A new routine has been incorporated in the Ritz program for the identification of small-amplitude vibrationally excited levels starting from the known energies of the ground-vibrational levels. We have been testing this routine in the region for . (2)A new LaseRitz program has been written for predicting FIR laser lines using known energies of the ground and the vibrationally excited levels. The simplified float chart of the interactive program is presented below
Effetto delle poliammine sulla regolazione della proteina cinasi C.
No full textEffetto delle poliamine sulla regolazione della proteina cinasi C. Nel tentativo di contribuire al chiarimento del ruolo delle poliamine sui processi di fosforilazione intracellulari, in questa fase dell’attività di ricerca abbiamo preso in esame gli effetti delle poliamine su diversi aspetti della regolazione della proteina cinasi C (PKC), serina/treonina cinasi che si presenta in diverse forme isoenzimatiche, alcune Ca++/diacilglicerolo (DAG)/fosfolipide dipendenti, ed altre con attività indipendente dal Ca++. Dal momento che l’associazione della PKC alle membrane è il prerequisito essenziale per la risposta fisiologica dell’enzima, particolare interesse è stato rivolto allo studio dell’effetto delle poliamine sul processo di associazione della PKC alle membrane. A questo scopo abbiamo utilizzato un sistema sperimentale costituito da PKC parzialmente purificata da cervello di ratto e da liposomi, costituiti da fosfolipidi acidi, soprattutto acido fosfatidico (PA) e fosfatidilserina (PS). La PKC associata all membrane è stata saggiata quantitativamente come recettore degli esteri del forbolo cioè misurando il legame dell’enzima attivato ad un estere del forbolo radioattivo (3H-PDBu) con cui l’enzima interagisce con una stechiometria di 1:1. Esperimenti eseguiti con liposomi di composizione definita hanno permesso di stabilire che nelle condizioni in cui prevale la formazione del complesso caratterizzato da una stechiometria di legame di 3/4 molecole di PL acido/molecola di SPM si ha un’inibizione nella formazione del complesso attivo. In questo caso infatti sembra che la SPM si disponga parallelamente alla superficie del liposoma impedendo l’ulteriore legame dell’enzima. Al contrario, nelle condizioni in cui prevale la formazione del complesso caratterizzato da una molecola di SPM/molecola di PS, la poliamina sembra legarsi perpendicolarmente alla superficie delle vescicole, e mediante i gruppi amminici non coinvolti nell’interazione con i fosfolipidi legare i siti anionici dell’enzima, favorendo l’interazione della PKC con i liposomi
Recent Evolution of the "Transgenic" Approach to the Automated Assignment of Molecular Spectra: Graph Algorithms and a New "Genetic" Encoding
No full text
A heuristic approach to automated molecular line assignment
No full textA first investigation on the feasibility of automated molecular line assignment is presented. Dense rovibrational molecular spectra are normally assigned by strongly interactive computer methods, ranging from commercial spreadsheets to dedicated programs, like Loomis-Wood or Ritz. While a general-purpose, fully automated assignment procedure seems to be out of reach for the near future, we show that a thorough investigation of the problem can lead to new, more efficient and less interactive methods, at least in reasonably favorable conditions. Interesting suggestions are provided by some modern "heuristic" problem-solving algorithms, which mimic natural processes. As a first step, we have developed a "transgenic-evolutionary" algorithm, which has successfully assigned artificial spectra of up to almost 3500 lines. We discuss also its performance on an experimental, but "filtered," methanol spectrum. Possible future improvements and developments of this method, as well as its limits, are discussed. (C) 2004 Elsevier Inc. All rights reserved
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