Work in progress — Studies on selecting successful design teams

This paper gives the first results of a work in progress, in collaboration with G. Michaud and G. Vauclair. It is a first attempt to compute the effects of meridional circulation and turbulence on diffusion processes in stellar envelopes. Computations have been made for a 2 Mʘstar, which lies in the Am - δ Scuti region of the HR diagram.Let us recall that in Am stars diffusion cannot occur between the two outer convection zones, contrary to what was assumed by Watson (1970, 1971) and Smith (1971), since they are linked by overshooting (Latour, 1972; Toomre et al., 1975). But diffusion may occur at the bottom of the second convection zone. According to Vauclair et al. (1974), the second convection zone, due to He II ionization, disappears after a time equal to the helium diffusion time, and then diffusion may happen at the bottom of the first convection zone, so that the arguments by Watson and Smith are preserved.

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A tilting high temperature gas reaction chamber for the JEM 7A T.E.M.

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100107496 ◽

1978 ◽

Vol 36 (1) ◽

pp. 70-71

Author(s):

Brian L. Rhoades

Keyword(s):

Cross Section ◽

Reaction Chamber ◽

Objective Lens ◽

Reduced Cross Section ◽

Cross Sectional ◽

Structural Investigations ◽

Transmission Electron ◽

Dynamic Experiments ◽

Successful Design ◽

Thermocouple Junction

A gas reaction chamber has been designed and constructed for the JEM 7A transmission electron microscope which is based on a notably successful design by Hashimoto et. al. but which provides specimen tilting facilities of ± 15° aboutany axis in the plane of the specimen.It has been difficult to provide tilting facilities on environmental chambers for 100 kV microscopes owing to the fundamental lack of available space within the objective lens and the scope of structural investigations possible during dynamic experiments has been limited with previous specimen chambers not possessing this facility.A cross sectional diagram of the specimen chamber is shown in figure 1. The specimen is placed on a platinum ribbon which is mounted on a mica ring of the type shown in figure 2. The ribbon is heated by direct current, and a thermocouple junction spot welded to the section of the ribbon of reduced cross section enables temperature measurement at the point where localised heating occurs.

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A Biological Cryosystem for the Scanning Electron Microscope

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100180823 ◽

1990 ◽

Vol 48 (1) ◽

pp. 414-415

Author(s):

Zhang zhaohua ◽

Luo Dong ◽

Guo Yisong

Keyword(s):

Electron Microscope ◽

Scanning Electron Microscope ◽

Natural State ◽

Specimen Preparation ◽

Cold Stage ◽

Specimen Temperature ◽

Successful Design ◽

Scanning Electron

Since early 1970's the use of cold stage on SEM for observation of hydrated samples in their natural state has become more and more popular despite its high cost. Experiences gained from earlier experiments indicate that a successful design should incorporate thefollowing features:1. The specimen temperature should be below −135°C (the recrystallization point of water), lower the temperature, better the results.2. The frozen specimen, the cold block in the specimen preparation chamber, as well as the cold stage should be kept under vacuum at all times to keep them frost free.3. Different specimen preparation processes such as fracturing, coating and sublimation should be possible in one compact preparation chamber .

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