Effects of frozen water content and silt fraction on unconfined compressive behavior of fill materials

Taking unsaturated clay foundation soil of an airport project in Hefei as the research object, the effects of particle gradation and mineral composition on the unsaturated soil properties were analyzed through two kinds of tests. The results show that there is a good correlation between the residual water content and the clay fraction or silt fraction content in the grading, and the residual water content has a significant positive linear correlation with the clay fraction content, but a negative linear correlation with the silt fraction content. Residual matric suction has a nonlinear correlation with clay fraction or silt fraction content in gradation, which has a significant nonlinear negative correlation with clay fraction content and a positive nonlinear correlation with silt fraction content. The residual water content and the residual matric suction have obvious linear relationship with the content of montmorillonite but have no obvious correlation with the content of illite. The water-storage coefficient of unsaturated airfield foundation soil decreases exponentially with the increase of clay content and montmorillonite content.

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Characterization of frozen hydrated biological specimens by low-loss EELS

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100132492 ◽

1992 ◽

Vol 50 (2) ◽

pp. 1572-1573

Author(s):

Songquan Sun ◽

Richard D. Leapman

Keyword(s):

Water Content ◽

Direct Method ◽

Internal Standard ◽

Dry Weight ◽

Dark Field ◽

Protein Solutions ◽

Subcellular Compartment ◽

Differential Shrinkage ◽

Electron Energy Loss

Analyses of ultrathin cryosections are generally performed after freeze-drying because the presence of water renders the specimens highly susceptible to radiation damage. The water content of a subcellular compartment is an important quantity that must be known, for example, to convert the dry weight concentrations of ions to the physiologically more relevant molar concentrations. Water content can be determined indirectly from dark-field mass measurements provided that there is no differential shrinkage between compartments and that there exists a suitable internal standard. The potential advantage of a more direct method for measuring water has led us to explore the use of electron energy loss spectroscopy (EELS) for characterizing biological specimens in their frozen hydrated state.We have obtained preliminary EELS measurements from pure amorphous ice and from cryosectioned frozen protein solutions. The specimens were cryotransfered into a VG-HB501 field-emission STEM equipped with a 666 Gatan parallel-detection spectrometer and analyzed at approximately −160 C.

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STEM measurement of subcellular water distributions

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100148678 ◽

1993 ◽

Vol 51 ◽

pp. 568-569

Author(s):

R.D. Leapman ◽

S.Q. Sun ◽

S-L. Shi ◽

R.A. Buchanan ◽

S.B. Andrews

Keyword(s):

Water Content ◽

Internal Standard ◽

Dry Weight ◽

Dry Mass ◽

Scanning Transmission Electron Microscope ◽

Dark Field ◽

Bulk Water ◽

Inelastic Electron ◽

Scanning Transmission ◽

Annular Dark Field

Recent advances in rapid-freezing and cryosectioning techniques coupled with use of the quantitative signals available in the scanning transmission electron microscope (STEM) can provide us with new methods for determining the water distributions of subcellular compartments. The water content is an important physiological quantity that reflects how fluid and electrolytes are regulated in the cell; it is also required to convert dry weight concentrations of ions obtained from x-ray microanalysis into the more relevant molar ionic concentrations. Here we compare the information about water concentrations from both elastic (annular dark-field) and inelastic (electron energy loss) scattering measurements.In order to utilize the elastic signal it is first necessary to increase contrast by removing the water from the cryosection. After dehydration the tissue can be digitally imaged under low-dose conditions, in the same way that STEM mass mapping of macromolecules is performed. The resulting pixel intensities are then converted into dry mass fractions by using an internal standard, e.g., the mean intensity of the whole image may be taken as representative of the bulk water content of the tissue.

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