Reaction Mechanism between Carbonyl Oxide and Hydroxyl Radical: A Theoretical Study

11 pages, 1 scheme, 5 figures, 2 tables.The reaction mechanism of carbonyl oxide with hydroxyl radical was investigated by using CASSCF, B3LYP, QCISD, CASPT2, and CCSD(T) theoretical approaches with the 6-311+G(d,p), 6-311+G(2df, 2p), and aug-cc-pVTZ basis sets. This reaction involves the formation of H2CO + HO2 radical in a process that is computed to be exothermic by 57 kcal/mol. However, the reaction mechanism is very complex and begins with the formation of a pre-reactive hydrogen-bonded complex and follows by the addition of HO radical to the carbon atom of H2COO, forming the intermediate peroxy-radical H2C(OO)OH before producing formaldehyde and hydroperoxy radical. Our calculations predict that both the pre-reactive hydrogen-bonded complex and the transition state of the addition process lie energetically below the enthalpy of the separate reactants (ΔH(298K) = −6.1 and −2.5 kcal/mol, respectively) and the formation of the H2C(OO)OH adduct is exothermic by about 74 kcal/mol. Beyond this addition process, further reaction mechanisms have also been investigated, which involve the abstraction of a hydrogen of carbonyl oxide by HO radical, but the computed activation barriers suggest that they will not contribute to the gas-phase reaction of H2COO + HOThe financial support for this research was provided by the Spanish Dirección General de Investigación Científica y Técnica (DGYCIT, Grant CTQ2005-07790) and by the Generalitat de Catalunya (Grant 2005SGR00111). The calculations described in this work were carried out at the Centre de Supercomputació de Catalunya (CESCA) and the Centro de Supercomputación de Galicia (CESGA), whose services are gratefully acknowledged, and at an AMD Opteron cluster of our group. A. Mansergas thanks the Spanish Ministerio de Educación y Ciencia for a fellowship (BES-2003-1352).Peer reviewe

Dual-band antennas in CST Studio Suite

The aim of this report is to learn about dual-band antennas, and carry out electromagnetic simulations of pre-designed antennas using CST Studio Suite, a commercial software. We will replicate the structural models of three representative dual-band antenna designs extracted from the scienti c literature, and we will try to obtain the same results after the simulation. For this, we will rst search information about the antennas we are going to work with, then we will learn how to use CST from a tutorial article provided by our instructors, and nally we will discuss the results obtained.2019/202

On the nature of the unusually long OO bond in HO3 and HO4 radicals

9 pages, 3 figures, 6 tables.-- PMID: 17989793 [PubMed].-- Supplementary information (Suppl. tables S1-S2, 3 pages) available at: http://www.rsc.org/suppdata/CP/b7/b711464h/b711464h.pdfThe HO3 and HO4 polyoxide radicals have attracted some attention due to their potential role in ozone chemistry. Experimentally, the geometrical structure of HO3 is known whereas that of HO4 is not. Moreover, the existence of the latter radical has been questioned. Theoretical calculations on the two species have been reported before, showing important structural differences depending on the computational level. Both radicals present an unusually long OO bond (around 1.7–1.8 A) that can be associated with an intricate interaction between HO, or HO2, with O2. The nature of such interaction is investigated in detail using large scale ab initio methods (CASSCF, CASPT2, MRCI, QCISD, CCSD(T)) and density functional techniques (B3LYP) in connection with extended basis sets. Stabilization enthalpies at 298 K with respect to HO (or HO2) and O2 have been computed amounting to -3.21 kcal mol-1 for HO3 (trans conformation) and 11.33 kcal mol-1 for HO4 (cis conformation). The corresponding formation enthalpies are 6.12 and 11.83 kcal mol-1. The trans conformation of HO4 is less stable than the cis one by 6.17 kcal mol-1. Transition states for HO4 dissociation and for cis/trans conversion are also described.This research has been supported by the Spanish Dirección General de Investigación Científica y Técnica (DGYCIT, Grant CTQ2005-07790) and by the Generalitat de Catalunya (Grant 2005SGR00111) and by a Spanish–French integrated action (HF-2005-0286). The calculations described in this work have been carried out at the Centro de Supercomputación de Galicia (CESGA) and at an AMD Opteron cluster of the IIQAB. A. Mansergas thanks the Spanish Ministerio de Educación y Ciencia for a fellowship (BES-2003-1352).Peer reviewe

SEGUE : a spectroscopic survey of 240,000 stars with g=14-20

The Sloan Extension for Galactic Understanding and Exploration (SEGUE) Survey obtained approximate to 240,000 moderate-resolution (R similar to 1800) spectra from 3900 angstrom to 9000 angstrom of fainter Milky Way stars (14.0 10 per resolution element, stellar atmospheric parameters are estimated, including metallicity, surface gravity, and effective temperature. SEGUE obtained 3500 deg(2) of additional ugriz imaging (primarily at low Galactic latitudes) providing precise multicolor photometry (sigma(g, r, i) similar to 2%), (sigma(u, z) similar to 3%) and astrometry (approximate to 0 ''.1) for spectroscopic target selection. The stellar spectra, imaging data, and derived parameter catalogs for this survey are publicly available as part of Sloan Digital Sky Survey Data Release 7