Robert V. Tompson

Treatment of canine oral squamous cell carcinomas with photodynamic therapy.

Eleven dogs with naturally occurring oral squamous cell carcinomas were treated with photodynamic therapy (PDT) using Photochlor (HPPH) as the photosensitizer. The largest length of the tumours measured in a two-dimensional plane ranged from 0.9 to 6.8 cm. Seven of the tumours invaded underlying bone as determined by radiograph appearance. Photochlor was injected intravenously at a dose of 0.3 mg kg–1. Forty-eight hours later the tumours were treated. Tumours with a surface to base depth of greater than 1 cm were surgically reduced to less than 1 cm. Irradiation with 665 nm light with an energy density of 100 J cm–2was administered. Eight dogs were considered cured with no tumour recurrence for at least 17 months after treatment. Local treatment of oral squamous cell carcinomas with PDT appears to give results similar to those obtained with surgical removal of large portions of the mandible or maxilla. The cosmetic results with PDT are superior to those of radical surgical removal. The new sensitizer, Photochlor, appears effective for oral squamous carcinomas with results similar to those reported for other sensitizers.

Slip coefficients for binary gas mixtures

A full description of rarefied gas flows requires the solution of the Boltzmann equation. In the near continuum regime, however, the preferred approach is to solve the Navier–Stokes equation subject to appropriate slip boundary conditions. For gas mixtures, the slip coefficients that enter into the conditions are dependent upon a host of parameters. Thus, one desires simple algebraic expressions for these coefficients that are also quite accurate. We describe in this article a study of the slip problems associated with the flow of binary gas mixtures. Using some general conservation laws, we first augment some previously reported expressions for the velocity and diffusion slips with an expression for the thermal slip and then we reduce all of the expressions to very convenient forms. Next, we report results of numerical computations for some specific gas mixtures using Lennard-Jones potentials and show previously unknown dependencies of the slips on the mixture properties. The new slip coefficients should...

Deposition patterns of molecular phase radon progeny (218Po) in lung bifurcations

Indoor air contamination by radon and its decay products is currently the focus of considerable attention and is considered by many to be the greatest potential cause of lung cancer in the human environment next to smoking. The bifurcations of the human respiratory tract are regions in which enhanced local deposition of particles (hot spots) can occur. These hot spots are important in estimating the risk from radon exposure but existing mathematical models do not characterize them accurately. In this study, radon progeny in the molecular size range were sampled through an aluminium model of a lung bifurcation. The parent and secondary tube diameters used correspond to the third and fourth generations in Weibels lung model. Steady state, nominally laminar flows were used in the study. Deposition was measured along the inside, outside, top, and bottom walls of the secondary tubes. Experimental results indicate that the deposition along the inside wall is noticeably higher than that along the other walls. The results also show that along the inside, top, and bottom walls the deposition has its overall maximum at the carina. Other maxima are also observed along the secondary tubes downstream from the carina.

Carbon Nanoparticle Generation, Collection, and Characterization Using a Spark Generator and a Thermophoretic Deposition Cell

Abstract Nanoparticles can form during nuclear accidents as well as during normal nuclear reactor operations and can be both radioactive and nonradioactive. It is important to understand particle size characteristics, transport properties, and deposition in order to better predict the behaviors of, and effects due to, these particles in a reactor. Fission products can deposit (adsorb/absorb) on the graphite dust in the core [an amount of carbon dust is present in the Pebble Bed Modular Reactor (PBMR) because of graphite sphere abrasion] and can also be carried by the helium flow (together with some dust). Generating nanoparticles of desired shape, size, and purity for experimental purposes is difficult, and hence, there is a need for new and refined synthesis techniques. Nanoparticle generation using high-voltage electric sparks has become a technique of interest for a wide range of conducting materials, and particles with sizes ranging from a few nanometers up to microns have been generated in this manner in an aerosol state. Our purpose in this paper is to report on the generation, collection, and characterization of carbon nanoparticles. We have used a spark generator and a thermophoretic deposition cell, as well as environmental scanning electron microscopy, transmission electron microscopy, and scanning mobility particle spectrometry. We have explored a number of experimental conditions, and we find that one can generate and effectively collect test particles with a variety of different useful characteristics. We also discuss some computational fluid dynamics simulations of particle deposition in the thermophoretic deposition cell.

Pharmacokinetics of pyropheophorbide‐a‐hexyl ether in the dog

Pyropheophorbide‐a‐hexyl ether (HPPH) is a new compound being investigated for use as a photosensitizer for photodynamic therapy; however, the pharmacokinetics are not known for any of the target species likely to be treated with this drug. The objective of this study was to determine the pharmacokinetic parameters of this drug prior to institution of a clinical trial in canine patients with various cancers. Study design, Materials and Methods. HPPH (0.3mg/kg I.V.) was administered to 12 dogs and blood samples were drawn at intervals for 24 hours and plasma HPPH concentrations were determined. Pharmacokinetic parameters were calculated for each dog.

Generation of Graphite Particles by Rotational/Spinning Abrasion and Their Characterization

Graphite particle generation by interpebble abrasion and by abrasion of pebbles with the containment vessel during operation of a pebble bed reactor is an issue of interest in the safety analysis of this class of very high temperature reactor. To understand particle generation, we have constructed an apparatus to generate graphite particles from preformed graphite hemispheres under rotational/spinning abrasive loading. We have initially used commercial-grade graphites in our experiments and have generated size distributions for the abraded particles, determined particle shapes, and measured the particle surface areas, pore volumes, and pore volume distributions of particles produced during abrasion of graphite surfaces under different conditions. The size distributions were studied using an Aerodynamic Particle Sizer™ and a Scanning Mobility Particle Sizer.™ Most of the particles observed were in the range from 18.1 to 600 nm in diameter. The scanning electron micrographs showed that the particles tend to be irregular in shape and porous in nature. We have also conducted Brunauer-Emmett-Teller surface area and pore volume measurements that have verified the highly porous nature of the particles. The calculated surface area and open porosity for our initial measurements of the particles from this particular grade of commercial graphite were found to be 626 m2 g-1 and 68%, respectively. In addition, the average surface roughness of fresh samples was 0.966 Ra μm at the point of contact.

Measurements of thermal creep in binary gas mixtures

Thermal creep occurs in all nonisothermal gas–mixture systems. The effect is more pronounced in rarefied gases and can play a significant role in, for example, microgravity crystal growth experiments, where natural convection is suppressed. Experimental measurements of the thermal creep in gas mixtures are, however, simply not available. We report experimental measurements of thermal creep in three binary gas mixtures: He:Ar, He:CO2, and Ar:CO2 at different mole ratios (mixture fractions). A stainless steel two-bulb measurement system employing seven capillaries to connect the bulbs is used to measure the steady-state pressure differences that develop between the bulbs for each mixture at a selection of total system pressures. Values of the total system pressure that were used range from 0.12 to 10.00 Torr. For all of the data reported, the two bulbs were held at temperatures of 397 and 297 K for the hot and cold sides, respectively. From the measured pressure differences, experimental values are obtained...

Generation of Graphite Particles by Sliding Abrasion and Their Characterization

Abstract Characterization of graphite particles (dust) produced by abrasion that would occur in a pebble bed reactor is of interest for reasons of safety, operation, and maintenance. To better understand this abrasion and particle generation, we have built a test apparatus to produce particles by sliding abrasion in a 1% to 5% relative humidity air environment. We have used a commercial-grade graphite in our experiments and have generated size distributions for the abraded particles. We have also fit lognormal functions to those size distributions (for use in computer codes); determined particle shapes; measured temperature and humidity during the tests; measured and calculated wear rates; and measured the surface roughness of both pretest and posttest samples, particle surface areas, pore volumes, and pore volume distributions of particles produced during abrasion of graphite surfaces under different loadings and sliding speeds. The experiments showed that as loading (analogous to pebble depth in the reactor) and sliding speed increase, so do the wear rates and numbers of particles produced, while surface roughness decreases, increases, and then decreases. Brunauer-Emmett-Teller measurements show that abrasion increases surface area from 0.583 m2/g in the bulk material to 555 m2/g in material abraded at high loading and high sliding speed. Wear rates range from 0.005 to 0.991 g/m per contact site. The size of the particles observed was <4000 nm. In all, our research shows that pebble abrasion is a complex process that is not constant during operation and thus should be considered for future work.

Total Hemispherical Emissivity of Potential Structural Materials for Very High Temperature Reactor Systems: Hastelloy X

Abstract An experimental system was constructed in accordance with the standard ASTM C835-06 to measure the total hemispherical emittance (emissivity) of structural materials of interest in very high temperature reactor (VHTR) systems. First, data were acquired for 304 stainless steel as well as for oxidized and unoxidized nickel, and good reproducibility and agreement with the literature was found. Emissivity of Hastelloy X was then measured under different conditions that included (a) “as received” (original sample) from the supplier, (b) with increased surface roughness, (c) oxidized, and (d) graphite coated. Measurements were made over a wide range of temperatures. Hastelloy X, as received from the supplier, was cleaned before additional roughening of the surface and coating with graphite. The emissivity of the original samples (cleaned after received) varied from ~0.18 to 0.28 in the temperature range of 473 to 1498 K. The apparent emissivity increased only slightly as the roughness of the surface increased (without corrections for the increased surface area due to the increased surface roughness). When Hastelloy X was coated with graphite or was oxidized, however, its emissivity was observed to increase substantially. With a deposited graphite layer on the Hastelloy, increases from 0.2 to 0.53 at 473 K and from 0.25 to 0.6 at 1473 K were observed—a finding that has strong favorable safety implications in terms of decay heat removal in postaccident VHTR environments. Initial oxidation of Hastelloy X surfaces was observed to notably increase the emissivity of the Hastelloy X but was not observed to progress significantly beyond the initial oxidation even with more prolonged exposure. Since there is likely to be initial surface oxidation of any Hastelloy X used in the construction of VHTRs, this represents an essentially neutral finding in terms of the safety implications in postaccident VHTR environments.

Computational flow and aerosol concentration profiles in lung bifurcations.

Flows in lung bifurcations are complicated by geometry, and it is recognized that accurate lung dosimetric models require realistic calculations of the flow and particle deposition patterns. A computational fluid dynamics study of flow and particle concentration has been carried out for a lung bifurcation based on the model developed by Weibel. The predicted flow patterns match well with previously reported experimental data. Secondary flow patterns and locations close to the walls having high particle concentrations are clearly seen.