Essays on Mechanism Design and the Informed Principal Problem

Three models of a privately informed contract designer (a principal) are examined. In the first, I study how much private information the principal wants to acquire before offering a contract to an agent. Despite allowing her to acquire all information for free, I prove in a general environment that there is a nontrivial set of parameters for which it is strictly suboptimal for the principal to be completely informed, regardless of the continuation equilibrium following any information acquisition choice. This result holds even when the principal is able to employ the most general mechanisms available and, in particular, when she can choose her most favourable full-information continuation equilibria. Further, in a specialized environment I characterize the principal’s optimal information choice. The second is a two-state principal-agent model with moral hazard in which the principal knows the state but the agent does not. This model is relevant to situations where an employer has private information about the productivity of a worker in a particular task while the worker has private information about the effort she exerts on the job. Much of the literature on this subject restricts the employer to offer contracts that leave her no discretion once a contract is accepted, while more general contracts may allow the employer to exercise discretion after acceptance; such contracts are called menu-contracts. I show when the employer can obtain strictly higher expected payoffs by offering menu-contracts than by offering the restricted contracts used in the literature. The final model studies the ability of a bidder in an auction to organize collusion among her rival bidders and the resulting impact of this collusion on the seller. Bidders valuations are private information. I show that in a two bidder, discrete, independent private-value auction, the seller earns less when a bidder can offer her rival a collusion proposal than in the absence of collusion. This contrasts with a cele- brated result by Che and Kim ( Robustly collusion-proof implementation . Econometrica, 74(4):1063–1107, July 2006) stating that for such auctions there is a mechanism that eliminates all the effects of collusion. Che and Kim and much of the literature assume an uninformed third-party organizes collusion

Neuronal avalanches recorded in the awake and sleeping monkey do not show a power law but can be reproduced by a self-organized critical model

Poster presentation: Self-organized critical (SOC) systems are complex dynamical systems that may express cascades of events, called avalanches [1]. The SOC state was proposed to govern brain function, because of its activity fluctuations over many orders of magnitude, its sensitivity to small input and its long term stability [2,3]. In addition, the critical state is optimal for information storage and processing [4]. Both hallmark features of SOC systems, a power law distribution f(s) for the avalanche size s and a branching parameter (bp) of unity, were found for neuronal avalanches recorded in vitro [5]. However, recordings in vivo yielded contradictory results [6]. Electrophysiological recordings in vivo only cover a small fraction of the brain, while criticality analysis assumes that the complete system is sampled. We hypothesized that spatial subsampling might influence the observed avalanche statistics. In addition, SOC models can have different connectivity, but always show a power law for f(s) and bp = 1 when fully sampled. This may not be the case under subsampling, however. Here, we wanted to know whether a state change from awake to asleep could be modeled by changing the connectivity of a SOC model without leaving the critical state. We simulated a SOC model [1] and calculated f(s) and bp obtained from sampling only the activity of a set of 4 × 4 sites, representing the electrode positions in the cortex. We compared these results with results obtained from multielectrode recordings of local field potentials (LFP) in the cortex of behaving monkeys. We calculated f(s) and bp for the LFP activity recorded while the monkey was either awake or asleep and compared these results to results obtained from two subsampled SOC model with different connectivity. f(s) and bp were very similar for both the experiments and the subsampled SOC model, but in contrast to the fully sampled model, f(s) did not show a power law and bp was smaller than unity. With increasing the distance between the sampling sites, f(s) changed from "apparently supercritical" to "apparently subcritical" distributions in both the model and the LFP data. f(s) and bp calculated from LFP recorded during awake and asleep differed. These changes could be explained by altering the connectivity in the SOC model. Our results show that subsampling can prevent the observation of the characteristic power law and bp in SOC systems, and misclassifications of critical systems as sub- or supercritical are possible. In addition, a change in f(s) and bp for different states (awake/asleep) does not necessarily imply a change from criticality to sub- or supercriticality, but can also be explained by a change in the effective connectivity of the network without leaving the critical state

Inclined plate settler for emergency water treatment: final design

Previously we reported on the proof-of-concept and initial optimisation work on an inclined plate settler (IPS) for water treatment in humanitarian situations. Whilst promising results (i.e. effluent turbidity < 5 NTU) were obtained, further work was warranted to better control and design the hydraulic flocculation (floc conditioning) stage of the treatment system. This paper reports on such work. A scaled-down version of the IPS was tested in parallel with several hydraulic flocculation configurations. The first deployment of the IPS is planned for 2015

Framing effects and output interference in a concurring partner review context: Theory and exploratory analysis

https://egrove.olemiss.edu/dl_proceedings/1107/thumbnail.jp

Leptospirosis and an Animal Bite

In October 2013, leptospirosis was identified in a 20-year-old male. The male was bitten on his hand by either his canine or a skunk while breaking up a fight between the two animals. Eight days after the bite, the male developed fever, headache, drowsiness, neck pain, nausea, vomiting, diarrhea, malaise and erythematous rash. Diagnosis was confirmed by amplification of Leptospira by DNA from a urine specimen. Veterinarian serology testing of the canine for Leptospira was negative. Leptospira in a human, acquired from an animal bite is a rare occurrence

A Clostridium perfringens Outbreak Traced to Improper Cooking of Prime Rib in Rochester, New York 2011

In December 2011, the Monroe County Department of Public Health investigated a report of gastrointestinal illness from two separate parties that had dined at a restaurant on the same day. An environmental and epidemiological investigation identified 17 individuals who met the outbreak case definition. A detailed questionnaire based on the restaurant’s menu was administered to patrons from both parties and statistically analyzed. Based on this investigation, it was hypothesized that consuming the prime rib (P \u3c 0.001) was associated with becoming ill. The environmental investigation indicated that the prime rib was not cooked to a proper temperature and was held at an improper temperature before being served. A prime rib sample and three stool samples from ill patrons were collected and sent for laboratory testing. Clostridium perfringens was identified in all of the samples by the New York State Department of Health (NYSDOH) Wadsworth Laboratory. This outbreak demonstrates the importance of proper food safety techniques for restaurants to prevent illness

Real-time phase-shift detection of the surface plasmon resonance

We investigate a method to directly measure the phase of a laser beam reflected from a metallic film after excitation of surface plasmon polaritons. This method permits real time access to the phase information, it increases the possible speed of data acquisition, and it may thus prove useful for increasing the sensitivity of surface plasmon based sensors

Inclined plate settling for emergency water treatment: towards optimisation

Previous work revealed the potential of an inclined plate settler (IPS) for water treatment in emergency relief applications. Whilst preliminary data demonstrated the tested IPS prototype’s capacity to achieve stable turbidity reductions, further optimisation was warranted. This paper reports on the optimisation and preliminary field testing of an IPS prototype. Trials revealed that after system modification, treatment objectives with regards to turbidity reductions (i.e. < 5 NTU) could be achieved. Such positive results were largely due to the addition of a hydraulic flocculation (conditioning) stage

Simulation of Near-field Dispersion of Pollutants Using Detached-Eddy Simulation

A numerical simulation is developed using the unsteady-state turbulence model on a structured highly refined grid to predict the wind-flow field and dispersion field of a pollutant emitted from a rooftop stack around a two-building configuration. The results obtained are compared with those of a steady-state model previously reported by the authors. The pollutant concentrations are examined on the roof where the stack is located as well as on the leeward wall of an upstream tower to the emitting building in order to evaluate how the pollutant is dispersed by the DES model compared to RNG model. DES results are discussed against those from RNG k–ε approach and wind tunnel. The study emphasises limits in reproducing correctly the wind flow and dispersion fields due to underestimation and/or overestimation of the Reynolds stress components and the steady-state methodology when using the RNG k–ε model. Despite such limits, the RNG model produces a similar average error, in terms of concentrations, to that obtained with the DES model

Does the 1/f frequency-scaling of brain signals reflect self-organized critical states?

Many complex systems display self-organized critical states characterized by 1/f frequency scaling of power spectra. Global variables such as the electroencephalogram, scale as 1/f, which could be the sign of self-organized critical states in neuronal activity. By analyzing simultaneous recordings of global and neuronal activities, we confirm the 1/f scaling of global variables for selected frequency bands, but show that neuronal activity is not consistent with critical states. We propose a model of 1/f scaling which does not rely on critical states, and which is testable experimentally.Comment: 3 figures, 6 page