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Technegas and Pertechnegas particle size distribution (1995)

Lloyd, J. J. ; Shields, R. A. ; Taylor, C. J. ; [et al.]

Springer

European journal of nuclear medicine 22 (1995), S. 473-476

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ISSN: 1619-7089

Keywords: Technegas ; Pertechnegas ; Lung ; Particle size ; Aerosol

Source: Springer Online Journal Archives 1860-2000

Topics: Medicine

Notes: Abstract Technegas and Pertechnegas are radioactive aerosols produced in a commercial generator and used for lung scintigraphy. The aerosols are produced by first evaporating to dryness standard technetium-99m generator eluate (99m-TcO4 in normal saline) in a graphite crucible (thesimmer stage) and then heating this to 2500° C (the „burn” stage). The aim of this work was to measure the particle size distributions of these agents and relate this to regional lung deposition. Factors that may vary during production of the aerosol in routine use were investigated to determine whether they influenced the particle size. Activity size distributions were measured using a serial wire-screen diffusion battery. The Technegas size distribution was approximately log-normal with an activity median diameter of 158 nm and a geometric standard deviation of 1.5. The results for Pertechnegas were similar. The median size increased with the number of simmers and with the time from generation. The increase in size with the number of simmers is thought to be due to the increased salt content in the crucible prior to the „burn”. The predicted lung deposition is 37% in the alveolar region and 5% in the bronchial region. Significant changes in deposition are not predicted over the range of particle sizes measured.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1007/BF00839062

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Stable and time-dissipative finite element methods for the incompressible Navier-Stokes equations in advection dominated flows (1995)

Simo, J. C. ; Armero, F. ; Taylor, C. A.

Chichester [u.a.] : Wiley-Blackwell

International Journal for Numerical Methods in Engineering 38 (1995), S. 1475-1506

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ISSN: 0029-5981

Keywords: finite elements ; incompressible Navier-Stokes ; upwinding schemes ; Engineering ; Engineering General

Source: Wiley InterScience Backfile Collection 1832-2000

Topics: Mathematics , Technology

Notes: This paper examines a new Galerkin method with scaled bubble functions which replicates the exact artificial diffusion methods in the case of 1-D scalar advection-diffusion and that leads to non-oscillatory solutions as the streamline upwinding algorithms for 2-D scalar advection-diffusion and incompressible Navier-Stokes. This method retains the satisfaction of the Babuska-Brezzi condition and, thus, leads to optimal performance in the incompressible limit. This method, when, combined with the recently proposed linear unconditionally stable algorithms of Simo and Armero (1993), yields a method for solution of the incompressible Navier-Stokes equations ideal for either diffusive or advection-dominated flows. Examples from scalar advection-diffusion and the solution of the incompressible Navier-Stokes equations are presented.

Additional Material: 24 Ill.