The fine structure of pancreatic stones as shown by scanning electron microscopy and x-ray probe microanalyser
SummaryTo delineate the process of pancreatic stone formation, stones from four patients were studied with a scanning electron microscope and X-ray probe microanalyser.The stones consisted of a central core and surrounding shell. Two kinds of stones were demonstrated:one had a core composed of a calcium-rich amorphous substance and interlacing fibrils; the other had a core consisting of multiple cavities with smooth walls composed of a calcium-deficient amorphous substance.The shells showed a common structure: zones of layers or bands of a calcium-rich amorphous substance, network fibrils filled with a calcium-rich amorphous substance, and laminated parallelogrammic or polygonal plates of calcite parallel to the surface in one layer and oblique or perpendicular in the next layer. Calcium was in the crypto-crystalline state as well as crystalline state of calcite. Crystalline calcite showed spiral and epitaxial growth along with findings of dissolution, resembling cholesterol crystals of gall stones. Pancreatic stones are probably formed through central core formation and layered growth of a shell. Comparison of stones and protein plugs suggests that protein plugs can grow to stones with calcite deposition accompanied by precipitation of network fibrils and an amorphous substance.
Scanning electron-microscopic studies on protein plugs obtained from patients with chronic pancreatitis
SummaryThe previous histochemical study on the endoscopically obtained protein plugs revealed the process of protein plug formation. The present scanning electron-microscopic study was performed to clarify the fine structure of the protein plug and was quite in accordance with the results of the histochemical study: (1) protein plugs were constructed of interlacing networks and amorphous material stuffed in the networks; (2) protein plug formation started in the form of random and loose interlacing of cottony network fibrils and poor stuffing with degenerating epithelial cells and amorphous material, and in this stage protein plugs enlarged by adherence of smaller aggregates; (3) with maturation, protein plugs came to be covered by stratiform fine networks which were more compactly built up with uniformly thick, dense and smooth fibers and were stuffed more densely with amorphous material; (4) mature protein plugs were considered to enlarge by repeated process of stratiform deposit of reticular substance and amorphous material and subsequent maturation.However, it remains to be clarified which factors induce the changes of networks from random interlacing to stratiform arrangement.
Arc flash hazard assessment in the mining industry
When it comes to electrical safety in the workplace, arc flash has become the most prominent topic over the past decade. The Occupational Safety and Health Administration (OSHA, including state chapters) is the only government body that recognizes NFPA-70E, Standard for Electrical Safety in the Workplace. However, OSHA does not have jurisdiction in mining operations. Electrical safety for the metal and nonmetal surface mining industry is covered by the Code of Federal Regulations (CFR) Title 30, Part 56, Subpart K (Electricity). The Mine Safety and Health Administration (MSHA) is responsible for enforcing electrical safety in mining operations. CFR Title 30 does not reference personal protective equipment (PPE) to protect electrical workers against arc flash hazards. This paper provides maintenance and safety personnel in surface Metal/Nonmetal mining operations with a step by step guide to implementing an electrical safety program that meets the requirements of MSHA, CFR Title 30 and NFPA-70E.