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PubMedDate not supplied

[Inter-laboratory comparison of measuring concentration of asbestos fibers less than 5 microM in length using phase-contrast microscopy].

Airborne asbestos fibers at the workplace are usually measured by phase-contrast microscopy (PCM), using the membrane filter method (MFM). Although the MFM has an international standardization, the application of this method can lead to wide differences in results. An inter-laboratory study, involving 19 laboratories, was organized. Two fiber classes were counted: 1) fibers greater than 5 microns in length and less than 3 microns in diameter; 2) fibers less than 5 microns in length and less than 3 microns in diameter. The results of each laboratory were normalised to the mean and their counting performance was compared. The estimated coefficients of variation or relative standard deviation (CV) of the normalised results were fitted assuming a constant component (K) and a component depending on the fiber count (Poisson component: mu-1/2). Fitting showed that the constant K is about 0.36 for counting fibers greater than 5 microns in length and about 0.52 for counting fibers less than 5 microns long. It was shown that counting the latter fiber class is influenced primarily by subjective laboratory-to-laboratory differences.

Asbestos↗
PubMed2002

Thermal induced modification of the contact mechanics of adhering liposomes on cationic substrate.

The correlation between the mechanical property and the thermotropic transition of the phospholipid bilayer has been recently demonstrated (Chem. Phys. Lipids 110 (2001) 27). However, the role of thermal induced mechanical responses of phospholipid bilayer on the contact mechanics of liposome adhering on a cationic substrate has not been determined. In this study, confocal-reflectance interference contrast microscopy, phase contrast microscopy and contact mechanics modeling are applied to probe the adhesion mechanisms of liposomes in the presence of electrostatic interactions during the thermotropic transition of the lipid bilayer. When temperature increases from 23 to 49 degrees C at pH 7.4, the degree of liposome deformation (a/R) and adhesion energy of dipalmitoyl-sn-glycero-3-phosphocholine liposome increases by 10% and remains constant, respectively, on 3-amino-propyl-triethoxy-silane (APTES) modified substrate. The extents of increase in these two parameters are highly dependent on the physicochemical properties of the rigid substrate. At pH 4, the adhesion energies above and below the phase transition temperature (T(m)) are increased by one order of magnitude due to the formation of the free silanol groups on APTES substrate. In hypotonic condition, the degree of vesicle deformation remains constant and the adhesion energy reduces by 20% during sample heating. Under all conditions, the adhesion energy of the adhering liposome spans a few orders of magnitude against the increase of liposome size as the surface area to volume ratio is maximized in smallest vesicle.

1,2-Dipalmitoylphosphatidylcholine↗
PubMed1985

Use of immunofluorescence and phase-contrast microscopy for detection and identification of Giardia cysts in water samples.

A method was developed in which indirect immunofluorescence and phase-contrast microscopy are used for rapid detection and identification of Giardia cysts in raw and finished water supplies. When anti-Giardia cyst antiserum and fluorescein conjugate were applied to known Giardia cysts on membrane filters, the cysts fluoresced bright green when they were illuminated by UV light. This procedure permitted individual cysts to be quickly located even in samples heavily contaminated with other microorganisms and debris. The identity of presumptive Giardia cysts located in this way could then be confirmed by observing characteristic internal morphological features with phase-contrast microscopy. With this method, Giardia cysts were detected and their identities were confirmed in samples taken from raw and finished surface water supplies during several recent outbreaks.

Fluorescent Antibody Technique↗
PubMed1975

Detection of fungi in clinical specimens by phase-contrast microscopy.

During 1973 and 1974, the following fungi were detected in clinical specimens by using phase-contrast microscopy: Blastomyces dermatitidis, 5; Coccidioides immitis, 3; Cryptococcus neoformans, 11; other yeasts 918; dermatophytes, 863; Mucor species, 1; and Aspergillus fumigatus, 16. This technique allows rapid detection and, in many instances, immediate identification of fungi in clinical specimens.

Arthrodermataceae↗