this research was conducted from july 1993 to june 1994 on the total population (711 workers) of a glass factory. the purpose of this study was to determine the quantitative free silica (quartz) in respiratory zone of workers in glass industry. field samples including 50 samples total dust and 37 samples respirable dust and standard simplex were collected on membrane filters using skc dust samp...

resonances are intrinsic characteristics of an elastic object, which are completely independent of thesource of excitation. the appropriate utilization of the information contained within the resonancespectra and the identification of the resonance frequencies of the object can be used as a potent toolfor material characterization. in this paper, a new mathematical model for the wave diffractio...

oxide nanoparticles can exhibit unique physical and chemical properties due to their limited size and a high density of corner or edge surface sites. in this study, mgo nanoparticle was synthesized using mg(ch3coo)2 and hexamethylenetetramine as starting materials. the structure and optical properties of these particles are investigated by using x-ray diffraction (xrd), scanning electron micros...

the magnetite (fe3o4) – agar nanocomposite was prepared by co-precipitation of fe (iii) and fe (ii) ions for the first time. the obtained samples were characterized by x-ray diffraction, fourier-transform infrared spectroscopy, scanning electron microscopy and transmission electron microscopy. ft-ir results confirm the formation of fe3o4 nanoparticles in agar matrix. the xrd results revealed th...

Some years ago I visited M. F. Perutz, the Cambridge biochemist who deciphered the structure of the hemoglobin molecule. Professor Perutz showed me a series of artifacts from his 20-year struggle to unravel the twists and folds of the oxygen-carrying protein. There was an x-ray diffraction film whose symmetrical array of dots looked like a lace doily, a contour map of electron density drawn on ...