The Effect of Changing the Gaseous Diffusion Coefficient on the Mass Loss Pattern of Hyalophora cecropia Pupae

Photospheric abundances are used to determine the importance of atomic diffusion, meridional circulation, mass loss and turbulence in main sequence and horizontal branch stars. Atomic diffusion leads to the appearance of the Li gap and the AmFm and HgMn phenomena at approximately the Teff at which they are observed. It leads to a 12 to 25% reduction in the age of halo stars. The Li abundance in Halo stars is probably 50% of the original abundance. Atomic diffusion competes with meridional circulation. The V sin i at which the HgMn and AmFm phenomena disappear give an argument in favour of the meridional circulation model of Tassoul and Tassoul. Mass loss is probably present in AmFm stars and cooler F stars but only at the rate of 10-15 M⊙ yr-1. In many objects, the turbulent particle diffusion coefficient is at most 10 times larger than the atomic diffusion coefficient.

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Modeling of the gaseous diffusion coefficient through unsaturated soil systems

Journal of Contaminant Hydrology ◽

10.1016/s0169-7722(96)00097-6 ◽

1997 ◽

Vol 29 (1) ◽

pp. 1-21 ◽

Cited By ~ 25

Author(s):

C.E. Schaefer ◽

R.R. Arands ◽

H.A. van der Sloot ◽

D.S. Kosson

Keyword(s):

Diffusion Coefficient ◽

Unsaturated Soil ◽

Gaseous Diffusion ◽

Soil Systems

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Mass Accommodation Coefficient of H2SO4Vapor on Aqueous Sulfuric Acid Surfaces and Gaseous Diffusion Coefficient of H2SO4in N2/H2O

The Journal of Physical Chemistry A ◽

10.1021/jp982809s ◽

1998 ◽

Vol 102 (49) ◽

pp. 10082-10089 ◽

Cited By ~ 58

Author(s):

Ulrich Pöschl ◽

Manjula Canagaratna ◽

John T. Jayne ◽

Luisa T. Molina ◽

Douglas R. Worsnop ◽

...

Keyword(s):

Diffusion Coefficient ◽

Sulfuric Acid ◽

Accommodation Coefficient ◽

Gaseous Diffusion ◽

Aqueous Sulfuric Acid ◽

Mass Accommodation Coefficient

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Mass Loss and Lithium Abundances in Popii Stars: A New Approach of The Primordial Value

Highlights of Astronomy ◽

10.1017/s153929960001176x ◽

1995 ◽

Vol 10 ◽

pp. 463-464 ◽

Cited By ~ 3

Author(s):

Sylvie Vauclair ◽

Corinne Charbonnel

Keyword(s):

Diffusion Coefficient ◽

Mass Loss ◽

Turbulent Diffusion ◽

Nuclear Reactions ◽

Lithium Abundance ◽

Turbulent Diffusion Coefficient ◽

New Approach ◽

Halo Stars ◽

Order Of Magnitude

The observations by Spite & Spite (1982), that the upper values of the lithium abundance in halo stars are one order of magnitude smaller than the ones observed in galactic stars, lead to a large debate about the primordial lithium abundance. The whole problem can be summarized by the following question: has lithium been depleted in the outer layers of halo stars, or has the original lithium been preserved at their surfaces since the beginning?It seems difficult to maintain the original lithium abundance in halo stars during all their lifetime. Either lithium is depleted due to element separation, or it is destroyed by nuclear reactions. Computations by Proffitt & Michaud (1989) showed that nowhere inside halo stars the lithium abundance could have remained at its original value.It was suggested by Vauclair (1988) that rotation-induced turbulence could lead to a nuclear destruction of lithium in halo stars large enough to explain their present abundances, with an original abundance equal to the present galactic one. It seemed possible that the “plateau shape” of the abundances be preserved if the turbulent diffusion coefficient decreased rapidly with radius, as in Zahn (1987) (see also Pinsonneault et al. 1992).

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Water accumulation as a function of temperature on specimens in an electron microscope cold stage

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100142219 ◽

1986 ◽

Vol 44 ◽

pp. 114-115 ◽

Cited By ~ 2

Author(s):

M.K. Lamvik ◽

D.A. Kopf ◽

S.D. Davilla ◽

J.D. Robertson

Keyword(s):

Electron Microscope ◽

Mass Loss ◽

Liquid Helium ◽

Liquid Nitrogen ◽

Liquid Nitrogen Temperature ◽

Liquid Helium Temperature ◽

Helium Temperature ◽

Cold Stage ◽

Water Accumulation ◽

Better Than

Last year we reported1 that there is a striking reduction in the rate of mass loss when a specimen is observed at liquid helium temperature. It is important to determine whether liquid helium temperature is significantly better than liquid nitrogen temperature. This requires a good understanding of mass loss effects in cold stages around 100K.

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Electron Beam-Induced Mass Loss in Freeze-Dried Tissue and Protein Samples

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s042482010011917x ◽

1985 ◽

Vol 43 ◽

pp. 470-471

Author(s):

M.E. Cantino ◽

M.K. Goddard ◽

L.E. Wilkinson ◽

D.E. Johnson

Keyword(s):

Electron Beam ◽

Salivary Gland ◽

Mass Loss ◽

Counting Rate ◽

Dose Dependence ◽

X Ray ◽

Large Samples ◽

Freeze Dried ◽

Muscle Homogenate ◽

Large Muscle

Quantification in biological x-ray microanalysis depends on accurate evaluation of mass loss. Although several studies have addressed the problem of electron beam induced mass loss from organic samples (eg., 1,2). uncertainty persists as to the dose dependence, the extent of loss, the elemental constituents affected, and the variation in loss for different materials and tissues. in the work described here, we used x-ray counting rate changes to measure mass loss in albumin (used as a quantification standard), salivary gland, and muscle.In order to measure mass loss at low doses (10-4 coul/cm2 ) large samples were needed. While freeze-dried salivary gland sections of the required dimensions were available, muscle sections of this size were difficult to obtain. To simulate large muscle sections, frog or rat muscle homogenate was injected between formvar films which were then stretched over slot grids and freeze-dried. Albumin samples were prepared by a similar procedure. using a solution of bovine serum albumin in water. Samples were irradiated in the STEM mode of a JEOL 100C.

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Elemental mass loss in silicate minerals during x-ray analysis

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100177155 ◽

1990 ◽

Vol 48 (4) ◽

pp. 804-805

Author(s):

P.E. Champness ◽

R.W. Devenish

Keyword(s):

Mass Loss ◽

Current Density ◽

Damage Mechanism ◽

Beam Current ◽

Single Chain ◽

Plagioclase Feldspar ◽

X Ray ◽

Alkali Ions ◽

Structural Order ◽

Sheet Silicate

It has long been recognised that silicates can suffer extensive beam damage in electron-beam instruments. The predominant damage mechanism is radiolysis. For instance, damage in quartz, SiO2, results in loss of structural order without mass loss whereas feldspars (framework silicates containing Ca, Na, K) suffer loss of structural order with accompanying mass loss. In the latter case, the alkali ions, particularly Na, are found to migrate away from the area of the beam. The aim of the present study was to investigate the loss of various elements from the common silicate structures during electron irradiation at 100 kV over a range of current densities of 104 - 109 A m−2. (The current density is defined in terms of 50% of total current in the FWHM probe). The silicates so far ivestigated are:- olivine [(Mg, Fe)SiO4], a structure that has isolated Si-O tetrahedra, garnet [(Mg, Ca, Fe)3Al2Si3AO12 another silicate with isolated tetrahedra, pyroxene [-Ca(Mg, Fe)Si2O6 a single-chain silicate; mica [margarite, -Ca2Al4Si4Al4O2O(OH)4], a sheet silicate, and plagioclase feldspar [-NaCaAl3Si5O16]. Ion- thinned samples of each mineral were examined in a VG Microscopes UHV HB501 field- emission STEM. The beam current used was typically - 0.5 nA and the current density was varied by defocussing the electron probe. Energy-dispersive X-ray spectra were collected every 10 seconds for a total of 200 seconds using a Link Systems windowless detector. The thickness of the samples in the area of analysis was normally 50-150 nm.

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