Numerical simulations of stochastic differential equations

A simple, very accurate algorithm for numerical simulation of stochastic differential equations is described. Its relationship to colored noise is elucidated and exhibited by explicit results. The especially delicate problem of mean first passage times is highlighted and highly accurate agreement between the numerical simulations and analytic results are shown.     

Optimal nonlinear approximation

We introduce a definition of nonlinear n-widths and then determine the n-widths of the unit ball of the Sobolev spaceW _p ^r inL _q. We prove that in the sense of these widths the manifold of splines of fixed degree with n free knots is optimal for approximating functions in these Sobolev spaces.This author was supported by NSF Grant DMS 8620108This author was supported by NSF Grant DMS 8803585     

Assignment of the NMR spectra of a potent ribonucleotide reductase inactivator - utilization of HMQC-TOCSY to establish connectivities in exchange broadened spectra

Inverted and Suppressed Direct Response (IDR and SDR, respectively) HMQC-TOCSY experiments are evaluated relative to the conventional HMQC-TOCSY experiment in the assignment of the congested proton and carbon spectra of a 2-acetylpyridine thiocarbonohydrazone used to potentiate the antiviral drug acyclovir. Spectra with moderate overlap can be most expeditiously interpreted using the inverted direct response HMQC-TOCSY variant; spectra with severe overlap can be more readily interpreted if direct responses are suppressed.     

Non-parametric estimation for renewal processes from event count data

A procedure is developed for estimating the interevent time distribution of a stationary renewal process that uses only data in the form of counts (the number of events occurring in each of several adjacent disjoint intervals) that are predominantly zeros and ones. Some properties of the procedure are derived, and the procedure's performance is assessed via Monte Carlo simulation.     

Kinematic, acoustic, and perceptual analyses of connected speech produced by parkinsonian and normal geriatric adults

Acoustic and kinematic analyses, as well as perceptual evaluation, were conducted on the speech of Parkinsonian and normal geriatric adults. As a group, the Parkinsonian speakers had very limited jaw movement compared to the normal geriatrics. For opening gestures, jaw displacements and velocities produced by the Parkinsonian subjects were about half those produced by the normal geriatrics. Lower lip movement amplitude and velocity also were reduced for the Parkinsonian speakers relative to the normal geriatrics, but the magnitude of the reduction was not as great as that seen in the jaw. Lower lip closing velocities expressed as a function of movement amplitude were greater for the Parkinsonian speakers than for the normal geriatrics. This increased velocity of lower lip movement may reflect a difference in the control of lip elevation for the Parkinsonian speakers, an effect that increased with the severity of dysarthria. Acoustically, the Parkinsonian subjects had reduced durations of vocalic segments, reduced formant transitions, and increased voice onset time compared to the normal geriatrics. These effects were greater for the more severe, compared to the milder, dysarthrics and were most apparent in the more complex, vocalic gestures.     

PREVENTION OF UV IRRADIATION INDUCED SUPPRESSION OF MONOCYTE FUNCTIONS BY RETINOIDS AND CAROTENOIDS in vitro

Abstract— The effects of stimulation of human peripheral blood monocytes in vitro with retinoids and carotenoids, and subsequent exposure to ultraviolet light of the B wavelength were measured. The compounds were applied to the monocytes in culture for 24 h, and the washed cells were then exposed to UVB light up to 220 J/m². The compounds tested protected the monocyte from UVB induced damage to phagocytic activity. This protection may be due to the antioxidant or UVB energy-quenching properties of these compounds. Monocyte cytotoxicity against a melanoma cell line was stimulated by exposure to the retinoids or carotenoids, but a protective effect in vitro against UVB damage was not seen for this cell function.