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Biomedical subjects

W B Williams

Publications and source records attributed to W B Williams.

6 recordsLinked to original sources
PubMed2005

Generating Bessel beams by use of localized modes.

We propose a novel method for generating both propagating and evanescent Bessel beams. To generate propagating Bessel beams we propose using a pair of distributed Bragg reflectors (DBRs) with a resonant point source on one side of the system. Those modes that couple with the localized modes supported by the DBR system will be selectively transmitted. This is used to produce a single narrow band of transmission in kappa space that, combined with the circular symmetry of the system, yields a propagating Bessel beam. We present numerical simulations showing that a propagating Bessel beam with central spot size of approximately 0.5lambda0 can be maintained for a distance in excess of 3000lambda0. To generate evanescent Bessel beams we propose using transmission of a resonant point source through a thin film. A transmission resonance is produced as a result of the multiple scattering occurring between the interfaces. This narrow resonance combined with the circular symmetry of the system corresponds to an evanescent Bessel beam. Because propagating modes are also transmitted, although the evanescent transmission resonance is many orders of magnitude greater than the transmission for the propagating modes, within a certain distance the propagating modes swamp the exponentially decaying evanescent ones. Thus there is only a certain regime in which evanescent Bessel beams dominate. However, within this regime the central spot size of the beam can be made significantly smaller than the wavelength of light used. Thus evanescent Bessel beams may have technical application, in high-density recording for example. We present numerical simulations showing that with a simple glass thin film an evanescent Bessel beam with central spot size of approximately 0.34lambda0 can be maintained for a distance of 0.14lambda0. By choice of different material parameters, the central spot size can be made smaller still.

Journal Article↗
PubMed1991

Pain release splint.

The pain release splint is a soft vinyl orthotic. In the author's private practice it has proven to be efficient, inexpensive, reversible, and effective during the initial treatment stages of various craniomandibular disorders. This chapter deals with indications for use, construction, fitting and balancing, postinsertion instructions, and escalation to the next level of pain release splints or hard acrylic appliances.

Dental Occlusion↗
PubMed1990

Treatment of primary pulmonary hypertension with continuous intravenous prostacyclin (epoprostenol). Results of a randomized trial.

STUDY OBJECTIVE: To determine the efficacy of continuous intravenous infusion of prostacyclin (epoprostenol) in primary pulmonary hypertension. DESIGN: Randomized trial with 8-week treatment periods and nonrandomized treatment for up to 18 months. SETTING: Four referral centers. PATIENTS: Sequential sample of 24 patients with primary pulmonary hypertension. Nineteen patients completed the study. Four patients died and one left the study because of adverse effects (pulmonary edema). INTERVENTIONS: Continuous intravenous prostacyclin administered by portable infusion pump at doses determined by acute responses during baseline catheterization in ten patients. Nine patients were treated with anticoagulants, oral vasodilators, and diuretics. MEASUREMENTS AND MAIN RESULTS: Starting with a baseline value for total pulmonary resistance of 21.6 units, there was a decrease of 7.9 units (95% CI, -13.1 to -2.2; P = 0.022) in the prostacyclin-treated group after 8 weeks; there was virtually no change in the conventional therapy group (from 20.6 to 20.4 units, not significant). Six of ten prostacyclin-treated patients who completed the 8-week study period had reductions in mean pulmonary artery pressure of greater than 10 mm Hg, whereas only one of nine in the conventional treatment group had a similar response (P = 0.057). Nine patients receiving prostacyclin for up to 18 months have persistent hemodynamic effects, although dose requirements have increased with time. Complications have been attributable to the drug delivery system. CONCLUSIONS: Prostacyclin produces substantial and sustained hemodynamic and symptomatic responses in severe primary pulmonary hypertension and may be useful in the management of some patients with this disease.

Adolescent↗
PubMed1984

A factor structure of child home observation data.

Both normal and antisocial children were extensively observed in their natural home environments. A factor analysis of the baseline data was conducted that differed from the typical factor study in two respects. Equal numbers of deviant and nondeviant behaviors were included in the analysis, and the unit of analysis was the rate-per-minute occurrence of actual child behavior. The factor structure was interpretable, and scaling of the dimensions-I, Verbal Emotionality, II, Physical Dependency, III, Social Involvement, IV, Hostile: Controlling, and V, Hostile: Impulsive-separated groups of normal, socially aggressive, hyperactive-aggressive, and stealing children. Reported differences between aggressive and stealing children on rates of total aversive behavior were found to be due to differences in the verbal behaviors loading on the first factor.

Adolescent↗