View allAll Photos Tagged PCM
Modeled by Cassie Dyches Photos by Jeremey Dyches Pattern available on Ravelry.com Pattern by Kayla Dyches
Simple, captured image showing microscopic asbestos fibers and other ambient particles under 400x magnification using Phase-Contrast Microscopy (PCM) optical illumination method.
Although certain technical fiber-counting rules prohibit identification of specific fiber types using the PCM technique, this example depicts a reference slide with a known type of fiber; in this case, chrysotile asbestos fibers. Note characteristic splitting, wavy/flexible lines, narrow width, and splayed ends of the fibers (fiber bundles).
The visible "fibers" in the image are actually bundles of yet further bundles of "fibers". One of the more distinguishing features of asbestos is its incredible ability to subdivide into increasingly smaller and thinner fibers (far beyond the resolution of this microscopy method); until the fiber reaches its ultimate particle size: the theoretical, individual unit fibril (on the order of angstroms and nanometers). The minute size is also why asbestos can infiltrate into microscopic and cellular-level areas of lungs and other bodily systems.
Among other scientific applications, PCM is a fairly common, standard analytical technique utilized for testing air monitoring samples for airborne fiber concentrations pertaining to asbestos-related work, such as projects related to: abatement, repair, clean-up, worker exposure, ambient background, etc. Further, PCM equipment is relatively inexpensive, portable, and sturdy enough that it can be setup andcalibrated directly on many project sites, a particularly convenient advantage. This testing method is currently so routine, that if one is familiar with an asbestos abatement work project that has occurred or will occur, it's quite likely that PCM air monitoring is involved.
However, while used as an acceptable standard method for determining worker exposure levels to airborne fiber concentrations and for "clearance" of post-abatement work areas, there are a number of significant issues regarding over-reliance of PCM for airborne asbestos detection.
One main cause for concern are serious limitations of PCM's optical resolution. Unknown quantities of asbestos fibers may not be discernible using PCM, but are easily detected using more advanced and asbestos-specific imaging techniques such as transmission-electron microscopy (TEM). PCM may be considered as a "screening" method and possibly inadequate for truly accurate analyses of airborne asbestos fiber concentrations; another debate that typically boils down to Health vs. Cost.
Also depicted, partially shown, is a standardized Walton-Beckett graticule with incremental graduated x-y axes measured in micrometer units; diameter is approx. 100-µm across. Encircling the graticule area are measured scale markers in 3:1 length-to-width aspect ratio for visual reference. The green color is from a green-tinted light interference filter.
Captured image showing microscopic fiberglass fibers and other ambient particles under 400x magnification using Phase-Contrast Microscopy (PCM) optical illumination method. Note the "large" size of the fiberglass fibers relative to the 100-micrometer diameter graticule cirlce.
Certain fiber-counting rules using the PCM analysis method require that the fiberglass fibers be counted as "asbestos" (including any other interference particles that may meet the specific definition of a "fiber", such particles possibly as: cellulose, artificial man-made fibers, diatomes, hyphal fragments, organic structures, etc., may all be influential during counting process). Although an obvious interference to accurate airborne asbestos fiber concentrations, the non-asbestos fibers may adversely contribute toward a "positive-bias" of results.
Among other scientific applications, PCM is a fairly common, standard analytical technique utilized for testing air monitoring samples for airborne fiber concentrations pertaining to asbestos-related work, such as projects related to: abatement, repair, clean-up, worker exposure, ambient background, etc.
Further, PCM equipment is relatively inexpensive, portable, and sturdy enough that it can be setup directly on many project sites, a particularly convenient advantage. This testing method is currently so routine, that if one is familiar with an asbestos abatement work project that has occurred or will occur, it's quite likely that PCM air monitoring is involved.
However, while currently an acceptable standard method for determining worker exposure levels to airborne fiber concentrations and for "clearance" of post-abatement work areas, there are a number of significant issues regarding over-reliance of PCM for airborne asbestos detection.
One main cause for concern are serious limitations of PCM's optical resolution. Unknown quantities of asbestos fibers too fine for observation at 400x may not be discernible using PCM, but are better detected using more advanced and asbestos-specific imaging techniques such as transmission-electron microscopy (TEM). PCM may be considered more as a simple "screening" method and possibly inadequate for truly accurate analyses of airborne asbestos fiber concentrations; another debate that typically boils down to Health vs. Cost, as TEM sample analysis is comparatively many times more costly than PCM sample testing fees.
Also depicted in this image, is a standardized Walton-Beckett graticule with incremental graduated x-y axes measured in micrometer units; diameter is approx. 100-µm across. Encircling the graticule area are measured scale markers in 3:1 length-to-width aspect ratio for visual reference. The green color is from a green-tinted light interference filter.
Presidente del Consejo de Ministros Héctor Valer acude al Congreso de la Republica para solicitar presentarse ante la representación nacional (Fotos: Congreso de la Republica / Ernesto Arias).
El Presidente del Congreso de la República, José Williams Zapata, se reunió con el Presidente del Consejo de Ministros , Alberto Otárola (Fotos: Congreso de la República / Ernesto Arias)
Peter Island and the Sir Francis Drake Channel
Tortola, BVI
Kodachrome MAR-82
Film 1 Frame 4 (PCM)
BVI-01-0004-01
A jpg file I made quite 10 years ago to show the difference in quality between a PCM 44 kh 16bit audio file ( typical CD sound quality) and the same file converted in MP3 (even at the highest quality ).
The black stripe on top of the right image shows clearly there are no sounds at higher frequencies in the mp3.
Mp3 file format is a very poor compression method, and nobody who loves music would listen mp3s instead of a non compressed ( or losslessly compressed audio file).
mp3 are just good for they travel fast over the internet and thus let artists show their music easily.
mp3 It's a good way to promote music giving away low quality samples.
high fidelity audio is a concept absolutely incompatible with mp3!!