Monitoring Technical Agents: Theory, Evidence, and Prescriptions

Agency relationships--where one party (the principal) delegates authority to another (the agent)--are well studied in financial settings but less so in technical settings. The asymmetry of information between the general manager and the technical manager is likely to create the possibility of misdirected effort, an overuse of the agent's human capital, whether the agent is opportunistic or not. Analyzing a dataset of information technology hardware and staff spending by larger multidivisional firms during a growth phase of US IT spending, 1989-1993, results suggest that technical managers significantly overspent on hardware, with deleterious consequences for performance. Chief executive experience significantly altered the effects of overspending. Analysis of the results suggest a solution, a model termed "staged commitment," that can be used to monitor technical agents in many areas of business.

Mathematical programs with equilibrium constraints: automatic reformulation and solution via constrained optimization

Constrained optimization has been extensively used to solve many large scale deterministic problems arising in economics, including, for example, square systems of equations and nonlinear programs. A separate set of models have been generated more recently, using complementarity to model various phenomenon, particularly in general equilibria. The unifying framework of mathematical programs with equilibrium constraints (MPEC) has been postulated for problems that combine facets of optimization and complementarity. This paper briefly reviews some methods available to solve these problems and described a new suite of tools for working with MPEC models. Computational results demonstrating the potential of this tool are given that automatically construct and solve a variety of different nonlinear programming reformulations of MPEC problems.\ud \ud This material is based on research partially supported by the National Science Foundation Grant CCR-9972372, the Air Force Office of Scientific Research Grant F49620-01-1-0040, Microsoft Corporation and the Guggenheim Foundation

HST-COS Spectroscopy of the Cooling Flow in Abell 1795 - Evidence for Inefficient Star Formation in Condensing Intracluster Gas

We present far-UV spectroscopy from the Cosmic Origins Spectrograph on the Hubble Space Telescope of a cool, star-forming filament in the core of Abell 1795. These data, which span 1025A - 1700A, allow for the simultaneous modeling of the young stellar populations and the intermediate-temperature (10^5.5 K) gas in this filament, which is far removed (~30 kpc) from the direct influence of the central AGN. Using a combination of UV absorption line indices and stellar population synthesis modeling, we find evidence for ongoing star formation, with the youngest stars having ages of 7.5 +/- 2.0 Myr and metallicities of 0.4 +/- 0.2 Zsun. The latter is consistent with the local metallicity of the intracluster medium. We detect the O VI (1038) line, measuring a flux of 4.0 +/- 0.9 x 10^-17 erg s^-1 cm^-2. The O VI (1032) line is redshifted such that it is coincident with a strong Galactic H2 absorption feature, and is not detected. The measured O VI (1038) flux corresponds to a cooling rate of 0.85 +/- 0.2 (stat) +/- 0.15 (sys) Msun/yr at ~10^5.5 K, assuming that the cooling proceeds isochorically, which is consistent with the classical X-ray luminosity-derived cooling rate in the same region. We measure a star formation rate of 0.11 +/- 0.02 Msun/yr from the UV continuum, suggesting that star formation is proceeding at 13 +/- 3% efficiency in this filament. We propose that this inefficient star formation represents a significant contribution to the larger-scale cooling flow problem.Comment: 6 pages, 4 figures. Accepted for publication in ApJ Letter

The Internalization of Advertising Services: An Inter-IndustryAnalysis

The common perception appears to be that vertical integration of advertising services is more the exception than the rule in the U.S. advertising industry. This study investigates the extent of such outsourcing and examines inter-industry variation in the use of in-house rather than independent advertising agencies by U.S. advertisers. While the vast majority of large advertisers employ outside agencies, it comes as a surprise to find that when advertisers of all sizes are considered, about half operate some form of in-house agency. Internalization of advertising services is much more widespread than has hitherto been appreciated and varies widely across industries. To explain this variation, we draw on concepts from research on scale economies and transaction costs to develop a set of hypotheses which we test in cross sectional analyses of data covering 69 two digit SIC industries at two points in time, 1991 and 1999. Across industries, we find that the likelihood of internalization of advertising services decreases as the size of advertising outlays increase but increases as advertising intensity and technological intensity increase and is greater for "creative" industries.Advertising Agencies, In-House, Vertical Integration, Make or Buy

An electric-field representation of the harmonic XY model

The two-dimensional harmonic XY (HXY) model is a spin model in which the classical spins interact via a piecewise parabolic potential. We argue that the HXY model should be regarded as the canonical classical lattice spin model of phase fluctuations in two-dimensional condensates, as it is the simplest model that guarantees the modular symmetry of the experimental systems. Here we formulate a lattice electric-field representation of the HXY model and contrast this with an analogous representation of the Villain model and the two-dimensional Coulomb gas with a purely rotational auxiliary field. We find that the HXY model is a spin-model analogue of a lattice electric-field model of the Coulomb gas with an auxiliary field, but with a temperature-dependent vacuum (electric) permittivity that encodes the coupling of the spin vortices to their background spin-wave medium. The spin vortices map to the Coulomb charges, while the spin-wave fluctuations correspond to auxiliary-field fluctuations. The coupling explains the striking differences in the high-temperature asymptotes of the specific heats of the HXY model and the Coulomb gas with an auxiliary field. Our results elucidate the propagation of effective long-range interactions throughout the HXY model (whose interactions are purely local) by the lattice electric fields. They also imply that global spin-twist excitations (topological-sector fluctuations) generated by local spin dynamics are ergodically excluded in the low-temperature phase. We discuss the relevance of these results to condensate physics.Comment: 13 pages, 10 figure

Sequential Sectioning of the Ulnar Collateral Ligament of the Elbow in Cadaveric Arms with Ulnohumeral Laxity Assessed by Dynamic Ultrasonography

Objectives: Injury of the ulnar collateral ligament (UCL), whether acute or chronic, is potentially career-threatening for elite overhead throwing athletes. Dynamic ultrasound (DUS) allows for rapid, cost-effective, non-invasive, and non-radiating evaluation of the UCL and elbow joint both at rest and with applied stress. The purpose of this study was to determine the amount of cadaveric elbow valgus laxity with sequential UCL sectioning using DUS. Our objective was to quantify which portions of the UCL must be injured to cause the varying levels of laxity seen clinically on DUS testing. No prior study has used DUS to quantify valgus joint laxity with sequential cadaveric UCL sectioning. It was hypothesized that the change in laxity due to release of the anterior band of the UCL would be greater than that seen when the posterior and transverse bands were cut. Methods: Twelve cadaveric elbows were dissected free of skin and subcutaneous tissue by an experienced orthopaedic surgeon. Baseline DUS at rest and with applied valgus stress was then performed by an experienced ultrasonographer. Sequential sectioning of the medial elbow soft-tissue stabilizing structures was then carried out with valgus stress applied to the joint at each sectioning interval utilizing a standardized device (Telos, Marburg, Germany). First the transverse band of the UCL was released, followed by the posterior band, then the anterior bundle of the anterior band, the remaining posterior bundle of the anterior band, and finally the complete flexor pronator mass. Results: Mean ulnohumeral laxity in millimeters with 95% CIs was calculated for each step of the sequence. The deltas between each step of the dissection were also calculated with means and 95% CIs. Mean baseline laxity of the unstressed ulnohumeral joint at rest was 3.2 mm (CI, 2.2-4.2); with the addition of valgus stress, mean laxity was 4.7 mm (CI, 3.5-6.0). When the transverse band was cut, ulnohumeral laxity increased to a mean of 5.5 mm (CI, 4.0-7.0). With release of the posterior band, mean laxity was 6.4 mm (CI, 4.3-8.5). When the anterior bundle of the anterior band of the UCL was cut, mean ulnohumeral laxity was 8.4 mm (CI, 5.7-11.0) and when the entire anterior band was released, mean laxity was 10.9 mm (CI, 7.8-14.0). Complete release of the flexor pronator muscle mass resulted in mean ulnohumeral laxity of 15.5 mm (CI, 12.9-18.1). The largest deltas were observed with release of the anterior bundle of the anterior band (2.0 mm; CI, 1.0-3.0), the entire anterior band (2.6 mm; CI, 1.3-3.8), and flexor pronator mass (4.6 mm; CI, 1.3-3.8). Release of the transverse and posterior bands of the UCL resulted in deltas of 0.74 mm (CI, 0.1-1.3) and 0.9 mm (CI, 0.3-1.5) respectively. Conclusion: DUS allows for rapid, cost-effective, non-invasive, non-radiating evaluation of the elbow joint and UCL both at rest and with applied valgus stress. Previous studies have indicated that DUS can identify abnormalities of the UCL associated with chronic degeneration and ligamentous injury including thickening of the anterior band of the UCL as well as hypoechoic foci/calcifications. The results of the current cadaveric study suggest that different changes in clinical laxity are seen on DUS with injury of particular bands of the UCL. Early identification and localization of injury to a particular band of the UCL may allow more appropriate selection of patients who will benefit from operative treatment. © The Author(s) 2013

Topological-sector fluctuations and ergodicity breaking at the Berezinskii-Kosterlitz-Thouless transition

The Berezinskii-Kosterlitz-Thouless (BKT) phase transition drives the unbinding of topological defects in many two-dimensional systems. In the two-dimensional Coulomb gas, it corresponds to an insulator-conductor transition driven by charge deconfinement. We investigate the global topological properties of this transition, both analytically and by numerical simulation, using a lattice-field description of the two-dimensional Coulomb gas on a torus. The BKT transition is shown to be an ergodicity breaking between the topological sectors of the electric field, which implies a definition of topological order in terms of broken ergodicity. The breakdown of local topological order at the BKT transition leads to the excitation of global topological defects in the electric field, corresponding to different topological sectors. The quantized nature of these classical excitations, and their strict suppression by ergodicity breaking in the low-temperature phase, afford striking global signatures of topological-sector fluctuations at the BKT transition. We discuss how these signatures could be detected in experiments on, for example, magnetic films and cold-atom systems.Comment: 11 pages, 6 figure

Assessing An Economics Programme: Hansen Proficiencies, ePortfolio, and Undergraduate Research

Numerous sources calling for more accountability in higher education are putting increased pressure on many economics departments to develop assessment plans. This paper discusses a set of principles for programmatic assessment gleaned from the assessment literature, while highlighting one US economic department's journey to develop an assessment of student learning outcomes based on Hansen's proficiencies. We explain the curriculum reforms that culminate with independent undergraduate research as suggested by the highest level of Hansen's proficiencies. We describe ePortfolios which showcase student abilities and integrate evidence of student learning across the curriculum. For departments without direct guidance from accreditation boards or other agencies, we put forth a process of forming programmatic assessment in economics.

Single Superconducting Split-Ring Resonator Electrodynamics

We investigate the microwave electrodynamic properties of a single superconducting thin film split-ring resonator (SRR). The experiments were performed in an all-Nb waveguide, with Nb wires and Nb SRRs. Transmission data showed a high-Q stopband for a single Nb SRR ($Q \sim 4.5\times10^4$ at 4.2 K) below $T_c$, and no such feature for a Cu SRR, or closed Nb loops, of similar dimensions. Adding SRRs increased the bandwidth, but decreased the insertion loss of the features. Placing the Nb SRR into an array of wires produced a single, elementary negative-index passband ($Q \sim 2.26\times10^4$ at 4.2 K). Changes in the features due to the superconducting kinetic inductance were observed. Models for the SRR permeability, and the wire dielectric response, were used to fit the data.Comment: 4 pages, 3 figures, RevTex, submitted to Applied Physics Letters. Updated version includes mention of bianisotropy, better looking figures, and different temperature dat