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A F Peterson

Publications and source records attributed to A F Peterson.

7 recordsLinked to original sources
PubMed2001

Modeling considerations for rigorous boundary element method analysis of diffractive optical elements.

Critical modeling issues relating to rigorous boundary element method (BEM) analysis of diffractive optical elements (DOEs) are identified. Electric-field integral equation (EFIE) and combined-field integral equation (CFIE) formulations of the BEM are introduced and implemented. The nonphysical interior resonance phenomenon and thin-shape breakdown are illustrated in the context of a guided-mode resonant subwavelength grating. It is shown that modeling such structures by using an open geometric configuration eliminates these problems that are associated with the EFIE BEM. Necessary precautions in defining the incident fields are also presented for the analysis of multiple-layer DOEs.

Journal Article↗
PubMed1992

Electric-field distribution near rectangular microstrip radiators for hyperthermia heating: theory versus experiment in water.

A rectangular microstrip antenna radiator is investigated for its near-zone radiation characteristics in water. Calculations of a cavity model theory are compared with the electric-field measurements of a miniature nonperturbing diode-dipole E-field probe whose 3 mm tip was positioned by an automatic three-axis scanning system. These comparisons have implications for the use of microstrip antennas in a multielement microwave hyperthermia applicator. Half-wavelength rectangular microstrip patches were designed to radiate in water at 915 MHz. Both low (epsilon r = 10) and high (epsilon r = 85) dielectric constant substrates were tested. Normal and tangential components of the near-zone radiated electric field were discriminated by appropriate orientation of the E-field probe. Low normal to transverse electric-field ratios at 3.0 cm depth indicate that the radiators may be useful for hyperthermia heating with an intervening water bolus. Electric-field pattern addition from a three-element linear array of these elements in water indicates that phase and amplitude adjustment can achieve some limited control over the distribution of radiated power.

Air↗
PubMed1978

Comparative evaluation of surgical scrub preparations.

The efficacy of 0.75 per cent available povidone-iodine scrub solution, 4 per cent chlorhexidine gluconate detergent solution and 3 per cent hexachlorophene emulsion against resident and transient flora of the hand has been compared using two currently accepted study designs. Chlorhexidine gluconate produced the greatest initial reductions against resident flora, followed by povidone-iodine and hexachlorophene, respectively. In subsequent washings, all three treatments further reduced the flora, chlorhexidine giving the greatest reduction on any test day. On gloved hands, there was significant regrowth following the use of povidone-iodine; there was no such significant regrowth on gloved hands which had been washed with chlorhexidine gluconate or hexachlorophene. Against transient flora, chlorhexidine gluconate gave the lowest over-all counts, followed by povidone-iodine and hexachlorophene, respectively. The reductions in bacteria counts increased following the repetitive use of chlorhexidine; no such trend was noted with either povidone-iodine or hexachlorophene.

Anti-Infective Agents, Local↗
PubMed1976

Safety and efficacy of the antiseptic chlorhexidine gluconate.

Chlorhexidine gluconate, an antiseptic for the skin, has recently been investigated in a series of clinical studies on its safety and efficacy. By using standard methods, Hibiclens, Hibitane tinted tincture and 0.5 per cent aqueous chlorhexidine gluconate were shown to have an extremely low potential for the production of irritation, allergic contact sensitization, photoallergic contact sensitization and phototoxicity. In the glove fluid test for efficacy against resident flora of the hand, Hibiclens produced log10 reductions over the control of 1.9398, 2.5371 and 2.6885 for test days 1, 2 and 5, respectively. Corresponding reductions for Hibitane tinted tincture were 3.6903, 4.0984 and 4.1253 and for the aqueous formulation, 1.5003, 1.5721 and 1.8692. In a transient flora skin contamination study, Serratia marcescens was applied at an average level of 6.8363 log10 organisms per milliliter to persons' hands, after which a 15 second Hibiclens hand wash was performed. Following five of these contaminations and hand washes, there was an over-all log10 reduction in recoverable Serratia of 3.8500. Counts were further determined after ten, 15, 20 and 25 contaminations and hand washes, resulting in corresponding reductions of 4.2649, 4.6661, 4.8501 and 5.1725, respectively. Chlorhexidine gluconate offers an alternative to available antiseptics for the skin. It has been shown to be a fast acting, broad spectrum antimicrobial agent, with an extremely low potential for eliciting dermal reactions.

Adult↗
PubMedDate not supplied

Tibial osteotomy.

Tibial osteotomy is the procedure of choice for young adults with disabling unicompartmental osteoarthritis of the knee. It is a conservative precursor to total knee arthroplasty. This article presents an overview of the indications for the surgery and the biomechanical rationale for the procedure. The immediate postsurgical and subsequent rehabilitative care of the patient is discussed, as well as implications for discharge planning.

Adult↗
PubMedDate not supplied

Noninvasive microwave phased arrays for local hyperthermia: a review.

Microwave energy has proven useful for treating superficial tumours in the head, neck and chest regions. Currently, multi-element phased arrays are being proposed to upgrade clinical capabilities for localized microwave hyperthermia. When compared with a single radiating element, phased array applicators are expected to provide deeper tissue penetration, reduce undesired heating of normal tissues between the applicator and tumour, and improve local control of the tumour temperature distribution. This paper surveys recent developments in the design and characterization of phased arrays, identifies anatomical and physiological factors that complicate successful clinical treatment and discusses the current state of phased array hardware development for hyperthermia.

Biomedical Engineering↗