The Acquisitive Nature of Extraverted CEOs

This study examines how extraversion, a personality trait that signifies more or less positive affect, assertive behavior, decisive thinking, and desires for social engagement, influences chief executive officers’ (CEOs’) decisions and the ensuing strategic behavior of firms. Using a novel linguistic technique to assess personality from unscripted text spoken by 2,381 CEOs of S&P 1500 firms over ten years, we show that CEOs’ extraversion influences the merger and acquisition (M&A) behavior of firms above and beyond other well-established personality traits. We find that extraverted CEOs are more likely to engage in acquisitions, and to conduct larger ones, than other CEOs and that these effects are partially explained by their higher representation on boards of other firms. Moreover, we find that the acquisitive nature of extraverted CEOs reveals itself particularly in so-called “weaker” situations, in which CEOs enjoy considerable discretion to behave in ways akin to their personality traits. Subsequent analyses show that extraverted CEOs are also more likely than other CEOs to succeed in M&As, as reflected by stronger abnormal returns following acquisition announcements

Dirac-harmonic maps from index theory

We prove existence results for Dirac-harmonic maps using index theoretical tools. They are mainly interesting if the source manifold has dimension 1 or 2 modulo 8. Our solutions are uncoupled in the sense that the underlying map between the source and target manifolds is a harmonic map.Comment: 26 pages, no figur

Magneto-optical imaging of magnetic flux patterns in superconducting films with antidots

Superconducting YBaCuO thin films were equipped with a special arrangement of antidots (holes) of 1 micron radius in order to guide the stream of magnetic flux moving in (or out of) the sample. The flux distribution and its dynamics were visualized using real-time magneto-optical imaging. It is clearly demonstrated that one-dimensional antidot arrays strongly facilitate propagation of magnetic flux. We also demonstrate a possibility to alter the direction of flux motion in a controlled way by special arrangement of intercepting antidot arrays. Our resolution was sufficient for observation of flux in particular antidots, which allows a more detailed dynamic analysis of such systems.Comment: 4 pages, 5 figures, submitted to Physica C, Proc. of VORTEX-IV Workshop on Crete-200

Harmonic maps from degenerating Riemann surfaces

We study harmonic maps from degenerating Riemann surfaces with uniformly bounded energy and show the so-called generalized energy identity. We find conditions that are both necessary and sufficient for the compactness in $W^{1,2}$ and $C^{0}$ modulo bubbles of sequences of such maps.Comment: 27 page

Efficacy of cyanoacrylate tissue adhesive in the management of corneal thinning and perforation due to microbial keratitis

Purpose: Report the efficacy of cyanoacrylate tissue adhesive (CTA) application in the management of corneal thinning and perforations associated with microbial keratitis.Methods: A retrospective review of consecutive patients who underwent CTA application for corneal thinning and perforation secondary to microbiologically proven infectious keratitis between 2001 and 2018 at a single center. We defined successful CTA application as an intact globe without tectonic surgical intervention.Results: The cohort included 67 patients, and 37 presented with corneal perforation while 30 had corneal thinning. The perforation/thinning was central/paracentral in 43 eyes and peripheral in 23 eyes. The underlying infectious etiologies were monomicrobial in 42 cases (35 bacterial, 3 fungal, 2 viral, and 2 acanthamoeba cases) and polymicrobial in 25 cases (22 polybacterial cases and 3 cases with a combination of Gram positive bacteria and fungus). The median duration of glue retention was 29 days. The CTA success rate was 73%, 64%, and 44% at 10, 30, and 180 days, respectively. CTA application appears more successful in monomicrobial (vs. poly -microbial) and Gram positive bacterial (vs. Gram negative) keratitis but the differences are statistically nonsignificant. The location of perforation/thinning and the use of topical corticosteroid were not associated with CTA failure.Conclusion: CTA was moderately effective in restoring globe integrity in severe corneal thinning and perforation secondary to microbial keratitis in the short term. However the majority of patients require tectonic surgical intervention within 6 months. CTA application success is not significantly associated with the location of thinning/perforation or the use of topical corticosteroid

Local fluctuations in quantum critical metals

We show that spatially local, yet low-energy, fluctuations can play an essential role in the physics of strongly correlated electron systems tuned to a quantum critical point. A detailed microscopic analysis of the Kondo lattice model is carried out within an extended dynamical mean-field approach. The correlation functions for the lattice model are calculated through a self-consistent Bose-Fermi Kondo problem, in which a local moment is coupled both to a fermionic bath and to a bosonic bath (a fluctuating magnetic field). A renormalization-group treatment of this impurity problem--perturbative in $\epsilon=1-\gamma$, where $\gamma$ is an exponent characterizing the spectrum of the bosonic bath--shows that competition between the two couplings can drive the local-moment fluctuations critical. As a result, two distinct types of quantum critical point emerge in the Kondo lattice, one being of the usual spin-density-wave type, the other ``locally critical.'' Near the locally critical point, the dynamical spin susceptibility exhibits $\omega/T$ scaling with a fractional exponent. While the spin-density-wave critical point is Gaussian, the locally critical point is an interacting fixed point at which long-wavelength and spatially local critical modes coexist. A Ginzburg-Landau description for the locally critical point is discussed. It is argued that these results are robust, that local criticality provides a natural description of the quantum critical behavior seen in a number of heavy-fermion metals, and that this picture may also be relevant to other strongly correlated metals.Comment: 20 pages, 12 figures; typos in figure 3 and in the main text corrected, version as publishe

Fluorescence spectrum of a two-level atom driven by a multiple modulated field

We investigate the fluorescence spectrum of a two-level atom driven by a multiple amplitude-modulated field. The driving held is modeled as a polychromatic field composed of a strong central (resonant) component and a large number of symmetrically detuned sideband fields displaced from the central component by integer multiples of a constant detuning. Spectra obtained here differ qualitatively from those observed for a single pair of modulating fields [B. Blind, P.R. Fontana, and P. Thomann, J. Phys. B 13, 2717 (1980)]. In the case of a small number of the modulating fields, a multipeaked spectrum is obtained with the spectral features located at fixed frequencies that are independent of the number of modulating fields and their Rabi frequencies. As the number of the modulating fields increases, the spectrum ultimately evolves to the well-known Mellow triplet with the sidebands shifted from the central component by an effective Rabi frequency whose magnitude depends on the initial relative phases of the components of the driving held. For equal relative phases, the effective Rabi frequency of the driving field can be reduced to zero resulting in the disappearance of fluorescence spectrum, i.e., the atom can stop interacting with the field. When the central component and the modulating fields are 180 degrees out of phase, the spectrum retains its triplet structure with the sidebands located at frequencies equal to the sum of the Rabi frequencies of the component of the driving field. Moreover, we shaw that the frequency of spontaneous emission can be controlled and switched from one frequency to another when the Rabi frequency or initial phase of the modulating fields are varied

Location of crossings in the Floquet spectrum of a driven two-level system

Calculation of the Floquet quasi-energies of a system driven by a time-periodic field is an efficient way to understand its dynamics. In particular, the phenomenon of dynamical localization can be related to the presence of close approaches between quasi-energies (either crossings or avoided crossings). We consider here a driven two-level system, and study how the locations of crossings in the quasi-energy spectrum alter as the field parameters are changed. A perturbational scheme provides a direct connection between the form of the driving field and the quasi-energies which is exact in the limit of high frequencies. We firstly obtain relations for the quasi-energies for some common types of applied field in the high-frequency limit. We then show how the locations of the crossings drift as the frequency is reduced, and find a simple empirical formula which describes this drift extremely well in general, and appears to be exact for the specific case of square-wave driving.Comment: 6 pages, 6 figures. Minor changes to text, this version to be published in Physical Review

Theory of charge transport in diffusive normal metal / unconventional singlet superconductor contacts

We analyze the transport properties of contacts between unconventional superconductor and normal diffusive metal in the framework of the extended circuit theory. We obtain a general boundary condition for the Keldysh-Nambu Green's functions at the interface that is valid for arbitrary transparencies of the interface. This allows us to investigate the voltage-dependent conductance (conductance spectrum) of a diffusive normal metal (DN)/ unconventional singlet superconductor junction in both ballistic and diffusive cases. For d-wave superconductor, we calculate conductance spectra numerically for different orientations of the junctions, resistances, Thouless energies in DN, and transparencies of the interface. We demonstrate that conductance spectra exhibit a variety of features including a $V$-shaped gap-like structure, zero bias conductance peak (ZBCP) and zero bias conductance dip (ZBCD). We show that two distinct mechanisms: (i) coherent Andreev reflection (CAR) in DN and (ii) formation of midgap Andreev bound state (MABS) at the interface of d-wave superconductors, are responsible for ZBCP, their relative importance being dependent on the angle $\alpha$ between the interface normal and the crystal axis of d-wave superconductors. For $\alpha=0$, the ZBCP is due to CAR in the junctions of low transparency with small Thouless energies, this is similar to the case of diffusive normal metal / insulator /s-wave superconductor junctions. With increase of $\alpha$ from zero to $\pi/4$, the MABS contribution to ZBCP becomes more prominent and the effect of CAR is gradually suppressed. Such complex spectral features shall be observable in conductance spectra of realistic high-$T_c$ junctions at very low temperature

Protons in near earth orbit

The proton spectrum in the kinetic energy range 0.1 to 200 GeV was measured by the Alpha Magnetic Spectrometer (AMS) during space shuttle flight STS-91 at an altitude of 380 km. Above the geomagnetic cutoff the observed spectrum is parameterized by a power law. Below the geomagnetic cutoff a substantial second spectrum was observed concentrated at equatorial latitudes with a flux ~ 70 m^-2 sec^-1 sr^-1. Most of these second spectrum protons follow a complicated trajectory and originate from a restricted geographic region.Comment: 19 pages, Latex, 7 .eps figure