3,980 research outputs found
Properties of Reactive Oxygen Species by Quantum Monte Carlo
The electronic properties of the oxygen molecule, in its singlet and triplet
states, and of many small oxygen-containing radicals and anions have important
roles in different fields of Chemistry, Biology and Atmospheric Science.
Nevertheless, the electronic structure of such species is a challenge for
ab-initio computational approaches because of the difficulties to correctly
describe the statical and dynamical correlation effects in presence of one or
more unpaired electrons. Only the highest-level quantum chemical approaches can
yield reliable characterizations of their molecular properties, such as binding
energies, equilibrium structures, molecular vibrations, charge distribution and
polarizabilities. In this work we use the variational Monte Carlo (VMC) and the
lattice regularized Monte Carlo (LRDMC) methods to investigate the equilibrium
geometries and molecular properties of oxygen and oxygen reactive species.
Quantum Monte Carlo methods are used in combination with the Jastrow
Antisymmetrized Geminal Power (JAGP) wave function ansatz, which has been
recently shown to effectively describe the statical and dynamical correlation
of different molecular systems. In particular we have studied the oxygen
molecule, the superoxide anion, the nitric oxide radical and anion, the
hydroxyl and hydroperoxyl radicals and their corresponding anions, and the
hydrotrioxyl radical. Overall, the methodology was able to correctly describe
the geometrical and electronic properties of these systems, through compact but
fully-optimised basis sets and with a computational cost which scales as
, where is the number of electrons. This work is therefore opening
the way to the accurate study of the energetics and of the reactivity of large
and complex oxygen species by first principles
Immobilisation of electroactive macrocyclic complexes within titania films
The 4-carboxyphenyl-appended macrocyclic ligand trans-6,13-dimethyl-6-((4-carboxybenzyl)amino)-1,4,8,11-tetraazacyclotetradecane-6-amine (HL10) has been synthesised and complexed with Co-III. The mononuclear complexes [Co(HL10)(CN)](2+) and [CoL10(OH)](+) have been prepared and the crystal structures of their perchlorate salts are presented, where the ligand is bound in a pentadentate mode in each case while the 4-carboxybenzyl-substituted pendent amine remains free from the metal. The cyano-bridged dinuclear complex [CoL10-mu-NC-Fe(CN)(5)](2-) was also prepared and chemisorbed on titania-coated ITO conducting glass. The adsorbed complex is electrochemically active and cyclic voltammetry of the modified ITO working electrode in both water and MeCN solution was undertaken with simultaneous optical spectroscopy. This experiment demonstrates that reversible electrochemical oxidation of the Fe-II centre is coupled with rapid changes in the optical absorbance of the film
A proposed sampling design for a timber inventory of a Tennessee forest
The purpose of this investigation was threefold. First, an extensive review of aerial forest parameters was undertaken. This was done in order to establish which parameters might serve as realistic indicators of volume for the Central Forest Region into which most of Tennessee\u27s forests are classified. The four aerial forest parameters that were selected were forest type, crown closure, crown diameter, and stand height. Second, a sampling design was proposed for the Central Forest Region of Tennessee based on the aerial forest volume parameters above, small scale photography (1:120,000) available from the National Aero-nautics and Space Administration (NASA), medium altitude photography, and some previous knowledge and subsequent determination of timber volume from the ground. The contributions of such a design are that for the first time: (a) small scale photography is proposed for a timber inventory in Tennessee; (b) photogrammetric parameters at any other scale are proposed as an integral part of a timber inventory in Tennessee; and (c) 3-P statistical sampling theory is the basis for determination of volume at the ground level of an aerial timber volume inventory. Third, the problem of optimization of the proposed sampling design was considered with respect to the two conventional optimization methods: (a) maximization of precision for a given cost or (b) minimi-zation of cost for a given precision. It was suggested that a new and different form of optimization method may evolve as a consequence of the possibility of several, equal results of minimum cost for a given, pre-cision or as a consequence of the possibility of several, equal results of maximum precision for a given cost
SLIDES: Chapter 7 of the Commission Report
Presenter: David L. Bernhardt, Partner, Brownstein Hyatt Farber Schreck (Washington, DC) and former Solicitor for U.S. Department of the Interior
14 slide
SLIDES: Chapter 7 of the Commission Report
Presenter: David L. Bernhardt, Partner, Brownstein Hyatt Farber Schreck (Washington, DC) and former Solicitor for U.S. Department of the Interior
14 slide
A New Phenomenon: Sub-Tg, Solid-State, Plasticity-Induced Bonding in Polymers
Polymer self-adhesion due to the interdiffusion of macromolecules has been an
active area of research for several decades [70, 43, 62, 42, 72, 73, 41]. Here,
we report a new phenomenon of sub-Tg, solid-state, plasticity-induced bonding;
where amorphous polymeric films were bonded together in a period of time on the
order of a second in the solid-state at ambient temperatures nearly 60 K below
their glass transition temperature (Tg) by subjecting them to active plastic
deformation. Despite the glassy regime, the bulk plastic deformation triggered
the requisite molecular mobility of the polymer chains, causing
interpenetration across the interfaces held in contact. Quantitative levels of
adhesion and the morphologies of the fractured interfaces validated the sub-Tg,
plasticity-induced, molecular mobilization causing bonding. No-bonding outcomes
(i) during the compression of films in a near hydrostatic setting (which
inhibited plastic flow) and (ii) between an 'elastic' and a 'plastic' film
further established the explicit role of plastic deformation in this newly
reported sub-Tg solid-state bonding
It's Not Just the ATMs: Technology, Firm Strategies, Jobs, and Earnings in Retail Banking
The authors examine trends in job content and earnings in selected jobs in two American banks. Firm restructuring and technological changes resulted in higher earnings for college-educated workers. The banks followed different strategies in implementing these changes for lower-skill jobs, with different effects on bank tellers in particular. The authors conclude that technology enables workplace reform but does not determine its effect on jobs and earnings; these effects are contingent on managerial strategies. This focus on organizational processes and managerial strategy provides a complementary approach to accounts of growing inequality that center solely on the role of individual skills and technological change.
Lawyers\u27 Ethics in Real Estate Transactions
In the past few months, two California decisions have made strong statements to lawyers about improper behavior in handling real estate matters for their clients. One such case is concerned with going into business with a client while representing the client and the other case addresses supporting the other side after the termination of the client\u27s representation
Cyanocobalt(III) complexes of penta- and tetradentate-coordinated macrocyclic hexaamines
The pendent-arm macrocyclic hexaamine trans-6,13-dimethyl-1,4,8,11-tetraazacyclotetradecane-6,13-diamine (L) may coordinate in tetra-, penta- or hexadentate modes, depending on the metal ion and the synthetic procedure. We report here the crystal structures of two pseudo-octahedral cobalt(III) complexes of L, namely sodium trans-cyano(trans-6,13-dimethyl-1,4,8,11-tetraazacyclotetradecane-6,13-diamine)cobalt(III) triperchlorate, Na[Co(CN)(C13H30N6)](ClO4)(3) or Na{trans-[CoL(CN)]}(ClO4)(3), (I), where L is coordinated as a pentadentate ligand, and trans-dicyano(trans-6,13-dimethyl-1,4,8,11-tetraazacyclotetradecane-6,13-diamine) cobalt (III) trans-dicyano (trans-6,13-dimethyl-1,4,8,11-tetraazacyclotetradecane-6,13-diaminium)cobalt(III) tetraperchlorate tetrahydrate, [Co(CN)(2)(Cl4H32N6)][Co(CN)(2)(Cl4H30N6)](ClO4)(4)•-4H(2)O or trans-[CoL(CN)(2)]trans-[Co(H2L)(CN)(2)] (ClO4)(4)•-4H(2)O, (II), where the ligand binds in a tetradentate mode, with the remaining coordination sites being filled by C-bound cyano ligands. In (I), the secondary amine Co-N bond lengths lie within the range 1.944 (3)-1.969 (3) &ANGS;, while the trans influence of the cyano ligand lengthens the Co-N bond length of the coordinated primary amine [Co-N = 1.986 (3) &ANGS;]. The Co-CN bond length is 1.899 (3) &ANGS;. The complex cations in (11) are each located on centres of symmetry. The Co-N bond lengths in both cations are somewhat longer than in (I) and span a narrow range [1.972 (3)-1.982 (3) &ANGS;]. The two independent Co-CN bond lengths are similar [1.918 (4) and 1.926 (4) &ANGS;] but significantly longer than in the structure of (1), again a consequence of the trans influence of each cyano ligand
Elevation correction of ERA-Interim temperature data in complex terrain
Air temperature controls a large variety of environmental processes, and is an essential input parameter for land surface models, for example in hydrology, ecology and climatology. However, meteorological networks, which can provide the necessary information, are commonly sparse in complex terrains, especially in high mountainous regions. In order to provide temperature data in an adequate temporal and spatial resolution for local scale applications a new elevation correction method has been developed that is able to downscale 3-hourly ERA-Interim temperature data. The scheme is based on model internal vertical lapse rates derived from different ERA-Interim pressure levels and has been validated for twelve meteorological stations in the German and Swiss Alps. The method was also compared with two other statistical, lapse rate based correction approaches. The results indicate that the use of model internal ERA-Interim lapse rates can significantly improve the downscaling performance when compared to the standard procedure of using fixed lapse rates
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