1,721,204 research outputs found
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Theoretical investigations of atmospheric species relevant for the search of high-energy density materials
No full textThe great effort put in the last decades in the study of the natural cycles of ozone and carbon dioxide, of the chemistry of air pollution and its effect on the depletion of ozone and on the greenhouse effect caused by combustion processes has shown the great importance of simple, but very reactive, species, as ions, radicals and “exotic” molecules. Being these species in the gas phase, it is particularly appropriate for their study the joint use of theoretical methods, at ab initio level, with experimental techniques, mass spectrometry specifically. Both these investigations methods improved in the last few years and, for this reason, they are particularly suitable for applications involving the study of the atmosphere. On the one hand, the high performance computing allows nowadays the theoretical investigation of more and more complex species at a great level of accuracy. On the other hand, mass spectrometry, with the development of techniques of neutralization/reionization, can now study neutral species (radicals, unstable molecules) which are of great interest in the atmospheric chemistry. The combined use of accurate theoretical methods and mass spectrometry techniques allowed us to discover recently several new species, both cationic and neutral, which can be important for the chemistry of terrestrial and planetary atmospheres. The neutral species are experimentally detected starting from a charged precursor of appropriate connectivity for the neutralization experiment aimed at the formation of the neutral by a vertical process. Some of these new species show also the peculiarity of being metastable: these species can dissociate towards the products through very exothermic processes; however, the dissociation usually presents an activation barrier. This “metastability” suggests that these species should be promising candidates of high energy density materials (HEDM), which can be the next generation of environmentally benign propellants and explosives, especially in relation to spacecraft propulsion
S3O and S3O+ in the gas phase: ring and open-chain structures
No full textRing and open-chain S3O sulfur oxides are detected by neutralization–reionization experiments. The paper reports experimental results that differ from the conclusions of a previous theoretical study (Chemm.Comm. 2005, 3712), and succeed in providing the definitive experimental assignment of the structure of S3O and S3O+. A simple labelling experiment gives strong evidence that the open-chain structure is detected and not just the ring one
Theoretical investigations of systems relevant for the chemistry of the atmosphere.
No full textThe great effort put in the last decades in the study of the chemistry of air pollution and its effect on the depletion of ozone and on the greenhouse effect caused by combustion processes has shown the great importance of simple, but very reactive, species, as ions, radicals and “exotic” molecules. Being these species in the gas phase, it is particularly appropriate for their study the joint use of theoretical methods with experimental techniques, mass spectrometry specifically. Both these investigations methods are particularly suitable for applications involving the study of the atmosphere. The combined use of accurate theoretical methods and mass spectrometry techniques allowed us to discover recently several new species, both cationic and neutral, which can be important for the chemistry of terrestrial and planetary atmospheres
The CS2O+ ion and its neutral counterpart in the gas phase: an experimental and computational study
No full textAb initio calculations on systems relevant for the chemistry of the atmosphere.
No full textThe great effort put in the last decades in the study of the chemistry of air pollution and its effect on the depletion of ozone and on the greenhouse effect caused by combustion processes has shown the great importance of simple, but very reactive, species, as ions, radicals and “exotic” molecules. Being these species in the gas phase, it is particularly appropriate for their study the joint use of theoretical methods with experimental techniques, mass spectrometry specifically. Both these investigations methods are particularly suitable for applications involving the study of the atmosphere. The combined use of accurate theoretical methods and mass spectrometry techniques allowed us to discover recently several new species, both cationic and neutral, which can be important for the chemistry of terrestrial and planetary atmospheres. As examples, we will present our recent studies on CS2O+ and CS2OH+ and their neutral species
Gas phase reactions of protonated chlorine, Cl2H+, with H2 (D2) and CH4. A mass spectrometric and theoretical study.
No full textFT-ICR (Fourier Transform Ion Cyclotron Resonance) experiments showed that the reaction of Cl2H+ with H2 (rate coefficient 6.3±1.0 cm3 s−1 molecule−1 at 298 K) yields ClH2+ ions, identified as protonated hydrochloric acid by CAD (Collisionally Activated Decomposition) mass spectrometry. Calculations performed at the B3LYP and CCSD(T) levels of theory show that the reaction involves insertion of the terminal Cl atom of Cl2H+ into the H–H bond, which accounts for the experimental observation that ClD2+ but not ClHD+ is formed from the reaction of Cl2H+ with D2. The same Cl+ insertion mechanism characterizes the reaction of Cl2H+ with CH4, whose product was identified as protonated methyl chloride, CH3ClH+, by CAD mass spectrometry
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