Governance Through Trading and Intervention: A Theory of Multiple Blockholders

http://rfs.oxfordjournals.org/content/early/2010/12/13/rfs.hhq145.full.pdf+htmlTraditional theories argue that governance is strongest under a single large blockholder, as she has high incentives to undertake value-enhancing interventions. However, most firms are held by multiple small blockholders. This article shows that, while such a structure generates free-rider problems that hinder intervention, the same coordination difficulties strengthen a second governance mechanism: disciplining the manager through trading. Since multiple blockholders cannot coordinate to limit their orders and maximize combined trading profits, they trade competitively, impounding more information into prices. This strengthens the threat of disciplinary trading, inducing higher managerial effort. The optimal blockholder structure depends on the relative effectiveness of manager and blockholder effort, the complementarities in their outputs, information asymmetry, liquidity, monitoring costs, and the manager's contract.Wharton SchoolRodney L. White Center for Financial Research (Goldman Sachs Research Fellowship

Seniority zero pair coupled cluster doubles theory

Coupled clusterﾠtheoryﾠwith single and doubleﾠexcitationsﾠaccurately describes weak electronﾠcorrelationﾠbut is known to fail in cases of strong staticﾠcorrelation.ﾠFascinatingly, however, pairﾠcoupled clusterﾠdoubles (p-CCD), a simplified version of theﾠtheoryﾠlimited to pairﾠexcitationsﾠthat preserve the seniority of the reference determinant (i.e.,ﾠthe number of unpaired electrons), hasﾠmean fieldﾠcomputational cost and is an excellent approximation to the full configuration interaction (FCI) of the paired space provided that the orbital basis defining the pairing scheme is adequately optimized. In previous work, we have shown that optimization of the pairing scheme in the seniority zero FCI leads to a very accurate description of staticﾠcorrelation.ﾠThe same conclusion extends to p-CCD if the orbitals are optimized to make the p-CCD energy stationary. We here demonstrate these results with numerous examples. We also explore the contributions of different seniority sectors to theﾠcoupled clusterﾠdoublesﾠ(CCD)ﾠcorrelationﾠenergy using different orbital bases. We consider both Hartree-Fock and Brueckner orbitals, and the role of orbital localization. We show how one can pair the orbitals so that the role of the Brueckner orbitals at theﾠCCDﾠlevel is retained at the p-CCD level. Moreover, we explore ways of extendingﾠCCDﾠto accurately describe strongly correlated systems

Distribución Geográfica de Culicidae de Argentina

Fil: Stein, Marina. Área de Entomología. Instituto de Medicina Regional. Universidad Nacional del Nordeste. Resistencia. Chaco; ArgentinaFil: Rossi, Gustavo Carlos. Centro de Estudios en Parasitología y Vectores (CEPAVE). Facultad de Ciencias Naturales y Museo. Universidad Nacional de La Plata; ArgentinaFil: Almirón, Walter R.. Instituto de Investigaciones Biológicas y Tecnológicas (IIByT). Universidad Nacional de Córdoba; Argentin

Description of male, pupa and larva of Psorophora (Grabhamia) paulli and redescription of the female (Diptera: Culicidae)

The female of Psorophora (Grabhamia) paulli Paterson & Shannon is redescribed, and the pupa, fourth-instar larva and male genitalia are described and illustrated for the first time. Information about the distribution, bionomics and taxonomy is also included. Adults of Ps. paulli can be separated from the other species of the genus and subgenus by its small size. The larva of Ps. paulli is similar to that of Ps. varinervis Edwards and Ps. discolor (Coquillett) but can be separated based on the development of setae 1-X and 5-VIII, the length of the anal papillae and the comb on a sclerotized area.Fil: Stein, Marina. Universidad Nacional del Nordeste. Instituto de Medicina Regional; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Rossi, Gustavo Carlos. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Centro de Estudios Parasitológicos y de Vectores. Universidad Nacional de La Plata. Facultad de Ciencias Naturales y Museo. Centro de Estudios Parasitológicos y de Vectores; ArgentinaFil: Almiron, Walter Ricardo. Universidad Nacional de Córdoba. Facultad de Ciencias Exactas, Físicas y Naturales. Centro de Investigaciones Entomológicas de Córdoba; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentin

Morphological description of the pupa and fourth-instar larva and redescription of the adults of Psorophora (Psorophora) pallescens Edwards (Diptera: Culicidae)

The adult male and female of Psorophora (Psorophora) pallescens Edwards are redescribed. The pupa and fourth-instar larva are described for the first time. The male genitalia, pupa and fourth-instar larva are illustrated. Information on distribution, bionomics and taxonomy is also included. Psorophora pallescens adults differ from the other species of the subgenus in the coloration of the scutum and abdomen. The larva can be distinguished from Psorophora ciliata based on characters of the head, thorax and abdomen.Fil: Stein, Marina. Universidad Nacional del Nordeste. Instituto de Medicina Regional; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Laurito, Magdalena. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Instituto de Investigaciones Biológicas y Tecnológicas. Universidad Nacional de Córdoba. Facultad de Ciencias Exactas, Físicas y Naturales. Instituto de Investigaciones Biológicas y Tecnológicas; ArgentinaFil: Rossi, Gustavo Carlos. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Centro de Estudios Parasitológicos y de Vectores. Universidad Nacional de La Plata. Facultad de Ciencias Naturales y Museo. Centro de Estudios Parasitológicos y de Vectores; ArgentinaFil: Almiron, Walter Ricardo. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Instituto de Investigaciones Biológicas y Tecnológicas. Universidad Nacional de Córdoba. Facultad de Ciencias Exactas, Físicas y Naturales. Instituto de Investigaciones Biológicas y Tecnológicas; Argentin

Morphological description of the female, pupa, and fourth-instar larva and redescription of the male of culex (melanoconion) aliciae (diptera: culicidae)

The female, pupa, and fourth-instar larva of Culex (Melanoconion) aliciae are described for the first time, and the male is redescribed. The cibarium, female and male genitalia, pupa, and fourth-instar larva are illustrated. Information on distribution, bionomics, and taxonomy is also included. Males of Cx. aliciae Duret and Cx. martinezi Casal & Garcia are indistinguishable, except for the appearance of the ninth tergal lobes. The female of Culex martinezi has not been described before. The females of Culex aliciae can be recognized by characteristics of the occipital scales, cibarium, and genitalia. The larva of Cx. aliciae and Cx. martinezi can be distinguished from characters of the thorax and abdomen.Fil: Bangher, Debora Natalia. Universidad Nacional del Nordeste; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Nordeste; ArgentinaFil: Rossi, Gustavo Carlos. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Centro de Estudios Parasitológicos y de Vectores. Universidad Nacional de La Plata. Facultad de Ciencias Naturales y Museo. Centro de Estudios Parasitológicos y de Vectores; ArgentinaFil: Almiron, Walter Ricardo. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Instituto de Investigaciones Biológicas y Tecnológicas. Universidad Nacional de Córdoba. Facultad de Ciencias Exactas, Físicas y Naturales. Instituto de Investigaciones Biológicas y Tecnológicas; ArgentinaFil: Stein, Marina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Nordeste; Argentina. Universidad Nacional del Nordeste. Instituto de Medicina Regional; Argentin

Piscine micronucleus test and the comet assay reveal genotoxic effects of Atrazine herbicide in the neotropical fish Rhamdia quelen

Atrazine (ATZ) is an herbicide extensively used around the world to kill weeds. Due to its applicability and benefits in farming, ATZ can easily reach the aquatic ecosystems and, therefore, represent risks for aquatic biota and human populations. The aim of this study was to evaluate the genotoxic effects of ATZ on Rhamdia quelen through the piscine micronucleus test (MNT) and the comet assay in erythrocytes (ECA) and gill cells (GCA), at three different concentrations (2, 10, and 100 μg L-1) in static (SB) and semi-static bioassays (SSB) during 96 hours. In the SB, we observed an increased frequency of nuclear morphological abnormalities at all concentrations and a dose-dependent effect of ATZ on DNA through the ECA. There was no difference among treatments in gills. In the SSB there was no significant difference in MNT, but the ECA showed an increase of DNA breakages at 10 μg L-1 treatment. GCA showed higher DNA damage on fish exposed to 2 and 100 μg L-1. Our results show a trend to dose-dependent genotoxic effect of ATZ, which causes damage to the DNA of Rhamdia quelen even in a concentration considered safe by regulatory agencies

Seniority-based coupled cluster theory

Doubly occupied configuration interaction (DOCI) with optimized orbitals often accurately describes strong correlations while working in a Hilbert space much smaller than that needed for full configuration interaction. However, the scaling of such calculations remains combinatorial with system size. Pair coupled cluster doubles (pCCD) is very successful in reproducing DOCI energetically, but can do so with low polynomial scaling ($N^3$, disregarding the two-electron integral transformation from atomic to molecular orbitals). We show here several examples illustrating the success of pCCD in reproducing both the DOCI energy and wave function, and show how this success frequently comes about. What DOCI and pCCD lack are an effective treatment of dynamic correlations, which we here add by including higher-seniority cluster amplitudes which are excluded from pCCD. This frozen pair coupled cluster approach is comparable in cost to traditional closed-shell coupled cluster methods with results that are competitive for weakly correlated systems and often superior for the description of strongly correlated systems.Comment: Revised manuscrip