943 research outputs found
Implementation of the LDA+U method using the full potential linearized augmented plane wave basis
We provide a straightforward and efficient procedure to combine LDA+U total
energy functional with the full potential linearized augmented plane wave
method. A detailed derivation of the LDA+U Kohn-Sham type equations is
presented for the augmented plane wave basis set, and a simple
``second-variation'' based procedure for self-consistent LDA+U calculations is
given. The method is applied to calculate electronic structure and magnetic
properties of NiO and Gd. The magnetic moments and band eigenvalues obtained
are in very good quantitative agreement with previous full potential LMTO
calculations. We point out that LDA+U reduces the total d charge on Ni by 0.1
in NiO
Thermophysical properties of the lanthanide sesquisulfides. III. Determination of Schottky and lattice heat‐capacity contributions of γ‐phase Sm2S3 and evaluation of the thermophysical properties of the γ‐phase Ln2S3 subset
We report the experimental heat capacity of γ‐phase Sm2S3 and derived thermophysical properties at selected temperatures. The entropy, enthalpy increments, and Gibbs energy function are 21.50R, 3063R⋅K, and 11.23R at 298.15 K. The experimental heat capacity is made up of lattice and electronic (Schottky) contributions. The lattice contribution is determined for all γ‐phase lanthanide sesquisulfides (Ln2S3 ) using the Komada/Westrum model. The difference between the experimental heat capacity and the deduced lattice heat capacity is analyzed as the Schottky contribution. Comparisons are made between the calorimetric Schottky contributions and those determined based on crystal‐field electronic energy levels of Ln3+ ions in the lattice and between the Schottky contributions obtained from the empirical volumetric priority approach and from the Komada/Westrum theoretical approach. Predictions for the thermophysical properties of γ‐phase Eu2S3 and γ‐phase Pm2S3 (unavailable for experimental determination) are also presented.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/71137/2/JCPSA6-96-8-6149-1.pd
Thermophysical properties of the lanthanide sesquisulfides. IV. Schottky contributions, magnetic, and electronic properties of ϵ‐phase Yb2S3 and Lu2S3
The heat capacities of ϵ‐phase Yb2S3 and Lu2S3 have been determined from 6 to 350 K and their thermodynamic properties evaluated. The resolution of the Schottky and magnetic properties by evaluation of the lattice heat capacity is shown to be in accord with spectroscopically determined energy levels. The lattice heat capacity of Yb2S3 was determined by means of the Komada–Westrum phonon distribution model. Excess heat‐capacity contributions were thus evaluated and analyzed as Schottky and magnetic heat capacities. A phase transition associated with magnetic ordering was detected in the heat capacity of Yb2S3 near 7 K with an entropy content of 0.68R. The entropies at 298.15 K are 22.77R and 19.74R for Yb2S3 and for Lu2S3. Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/70016/2/JCPSA6-98-2-1458-1.pd
Thermophysical properties of the lanthanide sesquisulfides. II. Schottky contributions and magnetic and electronic properties of γ‐phase Pr2S3, Tb2S3, and Dy2S3
Heat‐capacity measurements by adiabatic equilibrium calorimetry are reported for γ‐phase Pr2S3, Tb2S3, and Dy2S3 between 5 and 350 K. Highly purified samples were prepared and their composition verified by chemical analysis. Precision lattice parameters were determined for each compound and are compared with literature values. The total heat capacity has been resolved into lattice, magnetic, and Schottky components by a volumetric approach. The experimental Schottky contributions accord with the calculated curves based on the crystal‐field splitting of the 2S+1LJ ground state of the lanthanide ions occupying sites of S4 symmetry in the Th3P4 lattice. The individual crystal‐field electronic energy levels have been obtained in part from an analysis of the hot‐band data observed in the absorption spectra of Pr2S3, Tb2S3, and Dy2S3, and from a calculated splitting in which the crystal‐field parameters Bkm, were determined from a lattice‐sum calculation. Molar thermodynamic properties are reported for all three compounds. The entropy at 298.15 K {S0−S0 (7 K)}, is 22.78R, 22.93R, and 23.36R, for γ‐phase Pr2S3, Tb2S3, and Dy2S3, respectively.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/70592/2/JCPSA6-95-3-1964-1.pd
Media Reporting and Business Cycles: Empirical Evidence based on News Data
Recent literature suggests that news shocks could be an important
driver of economic cycles. In this article, we use a direct measure of news
sentiment derived from media reports. This allows us to examine whether innovations in the reporting tone correlate with changes in the assessment and expectations of the business situation as reported by firms in the German manufacturing sector. We fi nd that innovations in news reporting affect business expectations, even when conditioning on the current business situation and industrial production. The dynamics of the empirical model con rm theoretical predictions that news innovations affect real variables such as production via changes in expectations. Looking at individual sectors within manufacturing, we fi nd that macroeconomic news is at least as important for business expectations as sector-spefici c news. This is consistent with the existence of information complementarities across sectors
Enhanced Cooperation in an Asymmetric Model of Tax Competition
This paper analyzes enhanced cooperation agreements in corporate taxation in a three country tax competition model where countries differ in size. We characterize equilibrium tax rates and the optimal tax responses due to the formation of an enhanced cooperation agreement. Conditions for strategic complementarity or strategic substitutability of tax rates are crucial for the welfare effects of enhanced cooperation. Simulations show that enhanced cooperation is unlikely to be feasible for small countries. When enhanced cooperation is feasible, it may hamper global harmonization. Only when countries are of similar size is global harmonization a feasible outcome
Filling a blank on the map: 60 years of fisheries in Equatorial Guinea
Despite a scarcity of pertinent information, it has been possible to reconstruct time series of marine fisheries catches for Equatorial Guinea from 1950 to 2010 using per capita fish consumption and population numbers for small-scale fisheries, catch rates and number of vessels for industrial fisheries and discard rates to estimate the discarded bycatch. Small-scale fisheries, industrial large-scale fisheries, domestic and legal and illegal foreign fisheries and their discards are all included. Total catches were estimated at 2.7 million tonnes over the time period considered, of which 653 000 t were caught domestically compared to 187 000 t reported by FAO. This shows that fisheries have more importance for Equatorial Guinea's food security than the official data suggest. In contrast to what is suggested by official figures, fisheries were shown to be strongly impacted by civil and political unrest; notably, they declined overall because of civil and political conflicts, socio-demographic dynamics, and a growing role of the newly discovered oil resources, which directly and indirectly threaten the food security of the people of Equatorial Guinea
Effect of the GaAsP shell on optical properties of self-catalyzed GaAs nanowires grown on silicon
We realize growth of self-catalyzed core-shell GaAs/GaAsP nanowires (NWs) on
Si substrates using molecular-beam epitaxy. Transmission electron microscopy
(TEM) of single GaAs/GaAsP NWs confirms their high crystal quality and shows
domination of the zinc-blende phase. This is further confirmed in optics of
single NWs, studied using cw and time-resolved photoluminescence (PL). A
detailed comparison with uncapped GaAs NWs emphasizes the effect of the GaAsP
capping in suppressing the non-radiative surface states: significant PL
enhancement in the core-shell structures exceeding 2000 times at 10K is
observed; in uncapped NWs PL is quenched at 60K whereas single core-shell
GaAs/GaAsP NWs exhibit bright emission even at room temperature. From analysis
of the PL temperature dependence in both types of NW we are able to determine
the main carrier escape mechanisms leading to the PL quench
Functional characterization of a melon alcohol acyl-transferase gene family involved in the biosynthesis of ester volatiles. Identification of the crucial role of a threonine residue for enzyme activity
Volatile esters, a major class of compounds contributing to the aroma of many fruit, are synthesized by
alcohol acyl-transferases (AAT). We demonstrate here that, in Charentais melon (Cucumis melo var.
cantalupensis), AAT are encoded by a gene family of at least four members with amino acid identity ranging
from 84% (Cm-AAT1/Cm-AAT2) and 58% (Cm-AAT1/Cm-AAT3) to only 22% (Cm-AAT1/Cm-AAT4).
All encoded proteins, except Cm-AAT2, were enzymatically active upon expression in yeast and show
differential substrate preferences. Cm-AAT1 protein produces a wide range of short and long-chain acyl
esters but has strong preference for the formation of E-2-hexenyl acetate and hexyl hexanoate. Cm-AAT3
also accepts a wide range of substrates but with very strong preference for producing benzyl acetate.
Cm-AAT4 is almost exclusively devoted to the formation of acetates, with strong preference for cinnamoyl
acetate. Site directed mutagenesis demonstrated that the failure of Cm-AAT2 to produce volatile esters is
related to the presence of a 268-alanine residue instead of threonine as in all active AAT proteins. Mutating
268-A into 268-T of Cm-AAT2 restored enzyme activity, while mutating 268-T into 268-A abolished
activity of Cm-AAT1. Activities of all three proteins measured with the prefered substrates sharply increase
during fruit ripening. The expression of all Cm-AAT genes is up-regulated during ripening and inhibited in
antisense ACC oxidase melons and in fruit treated with the ethylene antagonist 1-methylcyclopropene
(1-MCP), indicating a positive regulation by ethylene. The data presented in this work suggest that the
multiplicity of AAT genes accounts for the great diversity of esters formed in melon
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