Levy process simulation by stochastic step functions

We study a Monte Carlo algorithm for simulation of probability distributions based on stochastic step functions, and compare to the traditional Metropolis/Hastings method. Unlike the latter, the step function algorithm can produce an uncorrelated Markov chain. We apply this method to the simulation of Levy processes, for which simulation of uncorrelated jumps are essential. We perform numerical tests consisting of simulation from probability distributions, as well as simulation of Levy process paths. The Levy processes include a jump-diffusion with a Gaussian Levy measure, as well as jump-diffusion approximations of the infinite activity NIG and CGMY processes. To increase efficiency of the step function method, and to decrease correlations in the Metropolis/Hastings method, we introduce adaptive hybrid algorithms which employ uncorrelated draws from an adaptive discrete distribution defined on a space of subdivisions of the Levy measure space. The nonzero correlations in Metropolis/Hastings simulations result in heavy tails for the Levy process distribution at any fixed time. This problem is eliminated in the step function approach. In each case of the Gaussian, NIG and CGMY processes, we compare the distribution at t=1 with exact results and note the superiority of the step function approach.Comment: 20 pages, 18 figure

User-Fee Financing of USDA Meat and Poultry Inspection

USDA's Food Safety and Inspection Service (FSIS) finances about 13.5 percent of its budget outlays through user fees for overtime and unscheduled meat and poultry inspections. User fees play an increasingly important role in financing government programs, and FSIS has frequently requested expanded authority to charge user fees for more of its operations. Congress has consistently rejected the FSIS requests and has placed important restrictions on fees and the uses of fee revenue at those agencies that have been granted more extensive user fee authority. This report surveys the application of user-fees for financing meat and poultry inspection programs in other countries; reviews user-fee systems in other Federal agencies, particularly those with food and agricultural missions or regulatory responsibilities; and discusses the relevant economics literature on the use and design of user fees. Finally, we suggest several elements that should underlie the structure of user fees for meat and poultry inspection, should such a program be introduced. euser fees, meat inspection, public finance, Livestock Production/Industries, Public Economics,

Transcatheter Electrical Ablation of Accessory Pathways in Children

Supraventricular tachycardia (SVT), the most common sustained symptomatic arrhythmia of childhood, is often supported hy a manifest or concealed accessory pathway. Permanent interruption of the accessory pathway usually requires surgical division. Recent experience with electrical ablation of posterior septal pathways in adults prompted us to apply the technique to children. Six children, ages 8 to 15 years, underwent a complete electrophysiological study followed by transcatheter electrical ablation. Five of the 6 children, 3 with a right posterior septal and 2 with a left posterior septal pathway, were approached with the ablation catheter at the os of the coronary sinus. In the remaining patient, a left lateral pathway was mapped with an electrode catheter in the coronary sinus and then approached with the ablation catheter through the patent foramen into the left atrium. Two patients are asymptomatic 18–24 months postabla-tion; one patient had return of anomalous conduction between 7 and 21 days after ablation. Two patients had transient interruption of anomalous conduction, whereas one patient experienced no effect. We conclude that in carefully selected patients, transcatheter electrical ablation ofers an alternative to surgery for permanent interruption of an accessory pathway. (PACE, Vol. 12, November 3989)Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/71986/1/j.1540-8159.1989.tb01865.x.pd

Concealed anterograde accessory pathway conduction during the induction of orthodromic reciprocating tachycardia

AbstractThe purpose of this study was to determine whether concealed anterograde accessory pathway conduction occurs during the induction of orthodromic tachycardia by an artrial extrastimulus (S2). Sixteen patients with an overt (n = 9) or concealed (n = 7) accessory pathway had inducible orthodromic tachycardia by S2during an atrial drive (S1) cycle length of 500 to 650 ms. A ventricular extrastimulus (S3) was introduced coincident with the His depolarization resulting from S2during the longest S1S2interval that reproducibly induced orthodromic tachycardia. The S1S3interval was decreased in 10 ms steps until S3reached ventricular refractoriness. Retrograde accessory pathway conduction of S3in the presence and absence of S2was compared at the same S1S3intervals.In the absence of S2there was retrograde accessory pathway conduction after S3in each patient. In the presence of S2, in patients with overt pre-excitation, retrograde accessory pathway conduction after S3was absent in one patient, prolonged in four patients and present only after long S1S3intervals in three patients. Only one patient had unchanged retrograde conduction regardless of the presence or absence of S2. In patients with a concealed accessory pathway, retrograde accessory pathway conduction after S3was absent in five patients and was prolonged in two. Thus, concealed anterograde accessory pathway conduction was present in 15 of 16 patients at the time of orthodromic tachycardia induction.In conclusion, concealed anterograde accessory pathway conduction occurs in a majority of patients with an overt or a concealed accessory pathway during induction of orthodromic tachycardia by an atrial extrastimulus. In some patients, the initiation of orthodromic tachycardia may depend on a critical interaction between the degree of concealed anterograde accessory pathway conduction and atrioventricular conduction delay after S2

Cotton Policy in China

This report examines China’s 2011-13 attempt to maintain a high level of price support for its cotton producers, analyzing the policy’s motivation, its consequences to date, and the impacts of various adjustment alternatives China might pursue. With China’s wages rising rapidly in recent years, cotton production costs there have been rising faster than in the rest of the world. Rising costs both helped motivate China’s policymakers to strengthen their price support for cotton production in 2011 and ensured that the policy ultimately proved unsustainable. After several years of sharply lower cotton consumption and sharply rising state-owned stockpiles of cotton, China in 2014 began switching producer support to direct subsidies, and focusing support on producers in the largest producing region, Xinjiang. Additional reforms include plans to restore market forces to a leading role in determining China’s cotton prices. But China’s large role in world cotton markets and the unprecedented size of the government’s stocks mean that difficult choices lie ahead for China’s policymakers. Policy decisions in China will continue to have a significant impact on the rest of the world, and lower Chinese import quotas for cotton could reduce world cotton prices significantly

Cotton Policy in China

This report examines China’s 2011-13 attempt to maintain a high level of price support for its cotton producers, analyzing the policy’s motivation, its consequences to date, and the impacts of various adjustment alternatives China might pursue. With China’s wages rising rapidly in recent years, cotton production costs there have been rising faster than in the rest of the world. Rising costs both helped motivate China’s policymakers to strengthen their price support for cotton production in 2011 and ensured that the policy ultimately proved unsustainable. After several years of sharply lower cotton consumption and sharply rising state-owned stockpiles of cotton, China in 2014 began switching producer support to direct subsidies, and focusing support on producers in the largest producing region, Xinjiang. Additional reforms include plans to restore market forces to a leading role in determining China’s cotton prices. But China’s large role in world cotton markets and the unprecedented size of the government’s stocks mean that difficult choices lie ahead for China’s policymakers. Policy decisions in China will continue to have a significant impact on the rest of the world, and lower Chinese import quotas for cotton could reduce world cotton prices significantly

Note and Comment

The Tight of a Trade Union to Enforce a Boycott; Criminal Responsibility of Husband for Maliciously Slandering His Wife; The Bulk Sales Laws; The Police Power and Liberty of Contract; The Obligations Resulting from an Indorsement, In Blank, Before Delivery, of a Negotiable Instrumen

The inferior turbinate flap in skull base reconstruction

BACKGROUND: As the indications for expanded endonasal approaches continue to evolve, alternative reconstructive techniques are needed to address increasingly complex surgical skull base defects. In the absence of the nasoseptal flap, we describe our experience with the posterior pedicle inferior turbinate flap (PPITF) in skull base reconstruction. DESIGN: Case series. SETTING: Academic tertiary care centre. METHODS: Patients who underwent reconstruction of the skull base with the PPITF were identified. Medical records were reviewed for demographic, presentation, treatment, follow-up, surgical and outcomes data. MAIN OUTCOME MEASURES: Flap survival, adequacy of seal, and complications. RESULTS: Two patients with residual/recurrent pituitary adenomas met the inclusion criteria. The nasoseptal flap was unavailable in each case due to a prior septectomy. Salvage of the original nasoseptal flap was not possible, as it did not provide adequate coverage of the resultant defect due to contraction from healing. All PPITFs healed uneventfully and covered the entire defect. No complications were observed in the early post-operative period. Endoscopic techniques and limitations of the PPITF are also discussed. CONCLUSIONS: Our clinical experience supports the PPITF to be a viable alternative for reconstruction of the skull base in the absence of the nasoseptal flap

Note and Comment

The Doctrine of Unfair Trade; Valuing Property and Franchises of Public Service Corporations for Fixing Rates; Right of the Interstate Commerce Commission to Adduce Testimony; Rule in Shelley\u27s Case controls Estate Created by Deed to Trustee; The Right of the Garnishee to Dispose of Goods in His Possession While the Litigation is Pending; The Police Power, Billboards and Sky Signs; How Far the Record of Voting Machines is Conclusive