Moore R.O.,University Heights
Optics Letters | Year: 2014
We demonstrate a trade-off between linewidth and loss-of-lock rate in a mode-locked laser employing active feedback to control the carrier-envelope offset phase difference. In frequency metrology applications, the linewidth translates directly to uncertainty in the measured frequency, whereas the impact of lock loss and recovery on the measured frequency is less well understood. We reduce the dynamics to stochastic differential equations, specifically diffusion processes, and compare the linearized linewidth to the rate of lock loss determined by the mean time to exit, as calculated from large deviation theory. © 2014 Optical Society of America.
Boubendir Y.,University Heights |
Antoine X.,University of Lorraine |
Geuzaine C.,University of Liege
Journal of Computational Physics | Year: 2012
This paper presents a new non-overlapping domain decomposition method for the Helmholtz equation, whose effective convergence is quasi-optimal. These improved properties result from a combination of an appropriate choice of transmission conditions and a suitable approximation of the Dirichlet to Neumann operator. A convergence theorem of the algorithm is established and numerical results validating the new approach are presented in both two and three dimensions. © 2011 Elsevier Inc.
Ihde E.S.,Hackensack University Medical Center |
Loh J.M.,University Heights |
Rosen L.,Hackensack University Medical Center
BMC Endocrine Disorders | Year: 2015
Background: The prevalence of pediatric hormonal disorders and hormonally-sensitive cancers are rising. Chemicals including bisphenol A (BPA), phthalates, parabens, 4-nonylphenol (4NP) and triclosan have been linked to disruption of endocrine pathways and altered hormonal status in both animal and human studies. Additionally, changes in estrogen metabolism have been associated with pediatric endocrine disorders and linked to estrogen-dependent cancers. The main objective of the study was to measure the presence of these environmental chemicals in prepubescent children and assess the relationship between chemical metabolites and estrogen metabolism. Methods: 50 subjects (25 male, 25 female) were recruited from the principal investigator's existing patient population at his pediatric primary care office. The first 5 boys and 5 girls in each age group (4 through 8 years old inclusive) who presented for annual examinations were included, as long as they were Tanner Stage I (prepubertal) on physical exam, without diagnosis of hormonally-related condition and/or cancer and able to give a urine sample. Urine samples were collected in glass containers for analysis of chemical and estrogen metabolites. Study kits and lab analysis were provided by Genova Diagnostics (Duluth, GA). Summary statistics for the concentrations of each chemical metabolite as well as estrogen metabolites were computed (minimum, maximum, median and inter-quartile range) for males only, for females only and for all subjects. Comparisons between groups (e.g. males v. females) were assessed using the nonparametric Wilcoxon test, since the data was skewed. The correlation between concentrations of chemical metabolites and estrogen metabolites in prepubescent children were examined by the Spearman's correlation coefficient (ρ). Results: 100 % of subjects had detectable levels of at least one chemical in their urine, and 74 % had detectable levels of eight or more chemicals. 28 % of subjects had measurable levels of 4NP. No associations were found between the urine levels of chemicals and estrogen metabolites. Conclusions: Endocrine disrupting environmental chemicals were detected in all children in the study, with measurable levels of 4NP in nearly 1/3 of subjects. This is the first known published study of 4NP levels in American children. No associations were found between the urine levels of chemicals tested and estrogen metabolites. The presence of multiple chemicals in a majority of children's urine coupled with increasing prevalence of pediatric hormonal disorders warrants further research to elucidate potential causal mechanisms in pre- and post-pubertal children. © 2015 Ihde et al.
Chou P.B.,University Heights
International Journal of Information Technology and Management | Year: 2011
This paper develops a game-theoretical model to address different levels of cooperation between two firms that share their knowledge/information systems as a local public good. The model shows that the collaboration between two firms can lead to the creation of new knowledge/information technology, and that a higher speed of creating new knowledge can change the structure of the game from a prisoners' dilemma game to a coordination game as an evolutionary process. Therefore, despite the knowledge-sharing dilemma, it is possible for both firms to reach the stable and more efficient full-collaboration equilibrium than the Nash collaboration equilibrium. © 2011 Inderscience Enterprises Ltd.
Matveev V.,University Heights |
Bertram R.,Florida State University |
Sherman A.,U.S. National Institutes of Health
Brain Research | Year: 2011
The number of Ca 2+ channels contributing to the exocytosis of a single neurotransmitter vesicle in a presynaptic terminal has been a question of significant interest and debate, and is important for a full understanding of localized Ca 2+ signaling in general, and synaptic physiology in particular. This is usually estimated by measuring the sensitivity of the neurotransmitter release rate to changes in the synaptic Ca 2+ current, which is varied using appropriate voltage-clamp protocols or via pharmacological Ca 2+ channel block under the condition of constant single-channel Ca 2+ current. The slope of the resulting log-log plot of transmitter release rate versus presynaptic Ca 2+ current is termed Ca 2+ current cooperativity of exocytosis, and provides indirect information about the underlying presynaptic morphology. In this review, we discuss the relationship between the Ca 2+ current cooperativity and the average number of Ca 2+ channels participating in the exocytosis of a single vesicle, termed the Ca 2+channel cooperativity. We relate these quantities to the morphology of the presynaptic active zone. We also review experimental studies of Ca 2+ current cooperativity and its modulation during development in different classes of synapses.