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At least 937 records · Page 52Linked to original sources
PubMed1994

Cobalt exposure in 'hard metal' and diamonds grinding tools manufacturing and in grinding processes.

Cobalt is considered to play a major role in the development of 'hard metal' interstitial lung disease, asthma and other adverse health effects. A survey of occupational exposure of workers is a fundamental step to obtain exposure-response information and for preventive action. Process related exposure assessment was performed before and after technical control in small and medium size factories in a large surveillance programme. Cobalt containing airborne dusts were sampled by performing multiple measurements at the workplace of each process in which the types of job and duration of exposure were similar. Samples were analyzed by atomic absorption spectroscopy. Very high exposure levels encountered before technical control were significantly lowered with efficient local exhaust ventilation plant in 'hard metal' and grinding processes, but sometimes the TLV of 0.05 mg/m3 were exceeded. In the manufacture of grinding tools, major steps in cobalt control by local ventilation was not able to keep exposure below the TLV; exposures from 0.12 to 0.75 mg/m3 were recurrent and these need control strategies.

Air Pollutants, Occupational↗
PubMed2003

EPR spectroscopy of [Fe2O2(5-Et3-TPA)2]3+: electronic origin of the unique spin-Hamiltonian parameters of the Fe2(III,IV)O2 diamond core.

The electronic origins of the magnetic signatures of [Fe(2)O(2)(5-Et(3)-TPA)(2)](ClO(4))(3), where 5-Et(3)-TPA = tris(5-ethyl-2-pyridylmethyl)amine, were investigated by density functional calculations. These signatures consist of a near-axial EPR spectrum, anisotropic superhyperfine broadening upon (17)O substitution in the Fe(2)O(2) core, and an unusually large, positive zero-field splitting parameter, D = 38 +/- 3 cm(-1). Density functional calculations identify the anisotropic (17)O superhyperfine broadening to be due to a preponderance of oxo 2p density perpendicular to the plane of the Fe(2)O(2) core in the three singly occupied molecular orbitals of the S = (3)/(2) ground state. The near-axial g-matrix arises from DeltaS = 0 spin-orbit mixing between the singly and doubly occupied d(pi) orbitals of the iron d-manifold. The large D is due to DeltaS = +/-1 spin-orbit mixing with low-lying d(pi) excited states. These experimental observables reflect the dominance of iron-oxo (rather than Fe-Fe) bonding in the Fe(2)O(2) core, and define the low-lying valence orbitals responsible for reactivity.

Diamond↗