176 research outputs found

    Do CAPM results hold in a dynamic economy. A Numerical analysis

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    Cataloged from PDF version of article.In this research we use the projection method (reported by Judd) to find numerical solutions to the Euler equations of a stochastic dynamic growth model. The mode1 that we solve is Brock’s asset pricing model for a variety of parameterizations of the production functions. Using simulated data from the model, conjectures (which are not analytically tractable) can be verified. We show that the market portfolio is mean-variance efficient in this dynamic context. We also show a result that is not available from the static CAPM theory: the efficient frontier shifts up and down over the business cycle

    The Equity Premium in Brock's Asset Pricing Model

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    Cataloged from PDF version of article.In this paper we combine dynamic programming methods with projection methods for solving stochastic growth models. As an application of these methods, we solve Brock’s asset pricing model with a variety of parameterizations. We focused on finding parameterizations that result in an equity premium that is high relative to the variation in consumption. We show (both analytically and numerically) that the equity premium can be higher in a production based asset pricing model than it is in the consumption based asset pricing model, even when the real output level is the same in both models. r 2006 Elsevier B.V. All rights reserved

    Bistable Gradient Networks II: Storage Capacity and Behaviour Near Saturation

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    We examine numerically the storage capacity and the behaviour near saturation of an attractor neural network consisting of bistable elements with an adjustable coupling strength, the Bistable Gradient Network (BGN). For strong coupling, we find evidence of a first-order "memory blackout" phase transition as in the Hopfield network. For weak coupling, on the other hand, there is no evidence of such a transition and memorized patterns can be stable even at high levels of loading. The enhanced storage capacity comes, however, at the cost of imperfect retrieval of the patterns from corrupted versions.Comment: 15 pages, 12 eps figures. Submitted to Phys. Rev. E. Sequel to cond-mat/020356

    Utility and Usability of Laser Speckle Contrast Imaging (LSCI) for Displaying Real-Time Tissue Perfusion/Blood Flow in Robot-Assisted Surgery (RAS): Comparison to Indocyanine Green (ICG) and Use in Laparoscopic Surgery.

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    BACKGROUND: Utility and usability of laser speckle contrast imaging (LSCI) in detecting real-time tissue perfusion in robot-assisted surgery (RAS) and laparoscopic surgery are not known. LSCI displays a color heatmap of real-time tissue blood flow by capturing the interference of coherent laser light on red blood cells. LSCI has advantages in perfusion visualization over indocyanine green imaging (ICG) including repeat use on demand, no need for dye, and no latency between injection and display. Herein, we report the first-in-human clinical comparison of a novel device combining proprietary LSCI processing and ICG for real-time perfusion assessment during RAS and laparoscopic surgeries. METHODS: ActivSight™ imaging module is integrated between a standard laparoscopic camera and scope, capable of detecting tissue blood flow via LSCI and ICG in laparoscopic surgery. From November 2020 to July 2021, we studied its use during elective robotic-assisted and laparoscopic cholecystectomies, colorectal, and bariatric surgeries (NCT# 04633512). For RAS, an ancillary laparoscope with ActivSight imaging module was used for LSCI/ICG visualization. We determined safety, usability, and utility of LSCI in RAS vs. laparoscopic surgery using end-user/surgeon human factor testing (Likert scale 1-5) and compared results with two-tailed t tests. RESULTS: 67 patients were included in the study-40 (60%) RAS vs. 27 (40%) laparoscopic surgeries. Patient demographics were similar in both groups. No adverse events to patients and surgeons were observed in both laparoscopic and RAS groups. Use of an ancillary laparoscopic system for LSCI/ICG visualization had minimal impact on usability in RAS as evidenced by surgeon ratings of device usability (set-up 4.2/5 and form-factor 3.8/5). LSCI ability to detect perfusion (97.5% in RAS vs 100% in laparoscopic cases) was comparable in both RAS and laparoscopic cases. CONCLUSIONS: LSCI demonstrates comparable utility and usability in detecting real-time tissue perfusion/blood flow in RAS and laparoscopic surgery

    An International Multi-Center Evaluation of Type 5 Long QT Syndrome: A Low Penetrant Primary Arrhythmic Condition.

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    Background: Insight into type 5 long QT syndrome (LQT5) has been limited to case reports and small family series. Improved understanding of the clinical phenotype and genetic features associated with rare KCNE1 variants implicated in LQT5 was sought through an international multi-center collaboration. Methods: Patients with either presumed autosomal dominant LQT5 (N = 229) or the recessive Type 2 Jervell and Lange-Nielsen syndrome (JLNS2, N = 19) were enrolled from 22 genetic arrhythmia clinics and 4 registries from 9 countries. KCNE1 variants were evaluated for ECG penetrance (defined as QTc > 460ms on presenting ECG) and genotype-phenotype segregation. Multivariable Cox regression was used to compare the associations between clinical and genetic variables with a composite primary outcome of definite arrhythmic events, including appropriate implantable cardioverter-defibrillator shocks, aborted cardiac arrest, and sudden cardiac death. Results: A total of 32 distinct KCNE1 rare variants were identified in 89 probands and 140 genotype positive family members with presumed LQT5 and an additional 19 JLNS2 patients. Among presumed LQT5 patients, the mean QTc on presenting ECG was significantly longer in probands (476.9 ± 38.6ms) compared to genotype positive family members (441.8 ± 30.9ms, p<0.001). ECG penetrance for heterozygous genotype positive family members was 20.7% (29/140). A definite arrhythmic event was experienced in 16.9% (15/89) of heterozygous probands in comparison with 1.4% (2/140) of family members (adjusted hazard ratio [HR]: 11.6, 95% confidence interval [CI]: 2.6-52.2; p=0.001). Event incidence did not differ significantly for JLNS2 patients relative to the overall heterozygous cohort (10.5% [2/19]; HR: 1.7, 95% CI: 0.3-10.8, p=0.590). The cumulative prevalence of the 32 KCNE1 variants in the Genome Aggregation Database (gnomAD), which is a human database of exome and genome sequencing data from now over 140,000 individuals, was 238-fold greater than the anticipated prevalence of all LQT5 combined (0.238% vs. 0.001%). Conclusions: The present study suggests that putative/confirmed loss-of-function KCNE1 variants predispose to QT-prolongation, however the low ECG penetrance observed suggests they do not manifest clinically in the majority of individuals, aligning with the mild phenotype observed for JLNS2 patients

    Markov-Perfect Nash Equilibria in Models with a Single Capital Stock

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    Many economic problems can be formulated as dynamic games in which strategically interacting agents choose actions that determine the current and future levels of a single capital stock. We study necessary conditions that allow us to characterize Markov perfect Nash equilibria (MPNE) for these games. These conditions result in an auxiliary system of ordinary differential equations that helps us to explore stability, continuity and differentiability of MPNE. The techniques are used to derive detailed properties of MPNE for several games including the exploitation of a finite resource, the voluntary investment in a public capital stock, and the inter-temporal consumption of a reproductive asset
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