Preemptive Behavior in Sequential-Move Tournaments with Heterogeneous Agents

Rank-order tournaments are usually modeled simultaneously. However, real tournaments are often sequential. We show that agents’ strategic behavior in sequential-move tournaments significantly differ from the one in simultaneous-move tournaments: In a sequential-move tournament with heterogeneous agents, there may be either a first-mover or a second-mover advantage. Under certain conditions the first acting agent chooses a preemptively high effort so that the following agent gives up. The principal is able to prevent preemptive behavior in equilibrium, but he will not implement first-best efforts although the agents are risk neutral.preemption, tournaments

Beat the gun - protection against zero-profit imitation

The recent development of 3D printing raises the issue of how to protect manufacturing firms from product piracy. In this paper, we are interested in potential regulatory requirements to protect firms from falling victim of product piracy and associated quality choices. We employ a game-theoretic model of duopoly competition. One firm offers a high-quality product facing quality-related costs. An imitator views the product and produces an imitation using a low-cost production method as 3D printing. Our results indicate that copy protection by the high-quality firm yields a higher quality than under patent protection. However, the chosen quality level of the high-quality firm is highest in duopoly without protection. Optimal patent protection crucially depends on the underlying objective function. It is only socially optimal if the regulatory authority maximises GDP

Why pay for jobs (and not for tasks)?

Consider a principal who assigns a job with two tasks to two identical agents. Monitoring the agents’ efforts is costly. Therefore the principal rewards the agents based on their (noisy) relative outputs. This study addresses the question of whether the principal should evaluate the outputs of each task separately and award two winner prizes, one for each task, or whether it is better to award only one winner prize to the agent who performs the best over the two tasks. There are two countervailing effects. First, there is a prize-diluting effect, because for a given budget, the prizes will be smaller when there are two winner prizes than when there is only one winner prize. The prize-diluting effect reduces the agents’ incentives to invest their effort when there are two winner prizes. Second, there is a noise effect because the noisiness of the evaluation is reduced when there are two winner prizes. The main contribution of this study is to show that the prize-diluting effect dominates the noise effect. Hence, in general, principals will award prizes for combined tasks, and not for separate tasks. Several extensions are considered to test the robustness of this dominance result

Quacks, Lemons, and Self-Regulation: A Welfare Analysis

The paper provides a framework in which suppliers of experience goods find it in their best interest to provide and enforce quality standards. This self-regulatory outcome is compared to various forms of statutory regulation, such as price regulation and quality regulation. The comparision is attractive, since the suppliers can observe each others' product qulity at lower cost than customers or policy maker. As long as quality is the only variable unknown to consumers and policy makers, any self-regulatory outcome can be replicated by an appropriate statutory policy. However, when additional variables (such as cost parameters) are private information of the suppliers, self-regulation may be strictly socially desirable.

Picosecond electric-field-induced threshold switching in phase-change materials

Many chalcogenide glasses undergo a breakdown in electronic resistance above a critical field strength. Known as threshold switching, this mechanism enables field-induced crystallization in emerging phase-change memory. Purely electronic as well as crystal nucleation assisted models have been employed to explain the electronic breakdown. Here, picosecond electric pulses are used to excite amorphous Ag$_4$In$_3$Sb$_{67}$Te$_{26}$. Field-dependent reversible changes in conductivity and pulse-driven crystallization are observed. The present results show that threshold switching can take place within the electric pulse on sub-picosecond time-scales - faster than crystals can nucleate. This supports purely electronic models of threshold switching and reveals potential applications as an ultrafast electronic switch.Comment: 6 pages manuscript with 3 figures and 8 pages supplementary materia

Association of Noncirrhotic Portal Hypertension in HIV-Infected Persons and Antiretroviral Therapy with Didanosine: A Nested Case-Control Study

Background. Noncirrhotic portal hypertension (NCPH) is a newly described life-threatening liver disease of unknown cause in human immunodeficiency virus (HIV)-infected persons. Postulated pathogenesis includes prolonged exposure to antiretroviral therapy, particularly didanosine. Methods. We performed a nested case-control study including 15 patients with NCPH and 75 matched control subjects of the Swiss HIV Cohort Study to investigate risk factors for the development of NCPH. Matching criteria were similar duration of HIV infection, absence of viral hepatitis, and follow-up to at least the date of NCPH diagnosis in the respective case. Results. All 15 case patients had endoscopically documented esophageal varices and absence of liver cirrhosis on biopsies; 4 died because of hepatic complications. At NCPH diagnosis, case patients and control subjects were similar concerning sex; race; Centers for Disease Control and Prevention stage; HIV-RNA level; CD4 cell count nadir; and lipids and lipodystrophy. Differences were found in age (conditional logistic regression odds ratio [OR] for 10 years older, 2.9; 95% confidence interval [CI], 1.4-6.1); homosexuality (OR, 4.5; 95% CI, 1.2-17); current CD4 cell count <200 cells/µL (OR, 34.3; 95% CI, 4.3-277); diabetes mellitus (OR, 8.8; 95% CI, 1.6-49); alanine aminotransferase level higher than normal (OR, 13.0; 95% CI, 2.7-63); alkaline phosphatase higher than normal (OR, 18.3; 95% CI, 4.0-85); and platelets lower than normal (OR, 20.5; 95% CI, 2.4-178). Cumulative exposure to antiretroviral therapy (OR per year, 1.3; 95% CI, 1.0-1.6), nucleoside reverse-transcriptase inhibitor (OR, 1.3; 95% CI, 1.1-1.7), didanosine (OR, 3.4; 95% CI, 1.5-8.1), ritonavir (OR, 1.4; 95% CI, 1.0-1.9), and nelfinavir (OR, 1.4; 95% CI, 1.0-1.9) were longer in case patients. Exposure to nonnucleoside reverse-transcriptase inhibitor and other protease inhibitors were not different between groups. In bivariable models, only the association of NCPH with didanosine exposure was robust; other covariables were not independent risk factors. Conclusions. We found a strong association between prolonged exposure to didanosine and the development of NCP

Left ventricular ejection fraction and cardiac biomarkers for dynamic prediction of cardiotoxicity in early breast cancer

BACKGROUND/PURPOSE: This study aims to quantify the utility of monitoring LVEF, hs-cTnT, and NT-proBNP for dynamic cardiotoxicity risk assessment in women with HER2+ early breast cancer undergoing neoadjuvant/adjuvant trastuzumab-based therapy. MATERIALS AND METHODS: We used joint models of longitudinal and time-to-event data to analyze 1,136 echocardiography reports and 326 hs-cTnT and NT-proBNP measurements from 185 women. Cardiotoxicity was defined as a 10% decline in LVEF below 50% and/or clinically overt heart failure. RESULTS: Median pre-treatment LVEF was 64%, and 19 patients (10%) experienced cardiotoxicity (asymptomatic n = 12, during treatment n = 19). The pre-treatment LVEF strongly predicted for cardiotoxicity (subdistribution hazard ratio per 5% increase in pre-treatment LVEF = 0.68, 95%CI: 0.48–0.95, p = 0.026). In contrast, pre-treatment hs-cTnT and NT-proBNP were not consistently associated with cardiotoxicity. During treatment, the longitudinal LVEF trajectory dynamically identified women at high risk of developing cardiotoxicity (hazard ratio per 5% LVEF increase at any time of follow-up = 0.36, 95% CI: 0.2–0.65, p = 0.005). Thirty-four patients (18%) developed an LVEF decline ≥ 5% from pre-treatment to first follow-up (“early LVEF decline”). One-year cardiotoxicity risk was 6.8% in those without early LVEF decline and pre-treatment LVEF ≥ 60% (n = 117), 15.9% in those with early LVEF decline or pre-treatment LVEF 5% during trastuzumab-based therapy. The longitudinal LVEF trajectory but not hs-cTnT or NT-proBNP allows for a dynamic assessment of cardiotoxicity risk in this setting

Microscopic origin of Cooper pairing in the iron-based superconductor Ba₁₋ₓKₓFe₂As₂

Resolving the microscopic pairing mechanism and its experimental identification in unconventional superconductors is among the most vexing problems of contemporary condensed matter physics. We show that Raman spectroscopy provides an avenue towards this aim by probing the structure of the pairing interaction at play in an unconventional superconductor. As we study the spectra of the prototypical Fe-based superconductor Ba1−xKxFe2As2 for 0.22 ≤ x ≤ 0.70 in all symmetry channels, Raman spectroscopy allows us to distill the leading s-wave state. In addition, the spectra collected in the B1g symmetry channel reveal the existence of two collective modes which are indicative of the presence of two competing, yet sub-dominant, pairing tendencies of dx2−y2 symmetry type. A comprehensive functional Renormalization Group and random-phase approximation study on this compound confirms the presence of the two sub-leading channels, and consistently matches the experimental doping dependence of the related modes. The consistency between the experimental observations and the theoretical modeling suggests that spin fluctuations play a significant role in superconducting pairing