PubMed · 8678220
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M Lucas Tomás. 1995. [Dental implants].. https://pubmed.ncbi.nlm.nih.gov/8678220/
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Lead (Pb) intoxication in children has been associated with neurodevelopmental disabilities which may result in motor and cognitive impairment. We conducted blood lead (PbB) measurements, neurological examinations and cognitive tests on children living in Ecuadorian villages where Pb is used extensively in the glazing of ceramics. Group I consisted of 55 children with a mean PbB level of 48.0 microg/dl (SD: 26.4, range: 9.2-119.1 microg/dl) who received PbB tests and complete neurological examinations. An appreciable number of the children with elevated PbB levels were normal on specific components of the neurological examination. Among the children who showed neurological deficits, higher PbB levels were associated with abnormal tendon reflexes, finger tapping, visual pursuit, size discrimination, draw-a-person, and math calculation skills. Group II consisted of 41 children with a mean PbB level of 47.4 microg/dl (SD: 22.0, range: 6.6-84.7 microg/dl) who were administered Raven's Coloured Progressive Matrices (RCPM) non-verbal reasoning test. Performance on RCPM was abnormal in 22 (53.7%) of 41 children. Children with abnormal RCPM scores had higher PbB levels (t-test: P=0.030). There was a significant inverse correlation between RCPM scores and PbB levels for children ages 9 years and older (r=-0.618, P=0.011). Males had higher mean PbB levels as a function of age than females (t-test: P=0.037), and more males showed neurocognitive deficits. The results demonstrate a range of neurological responses in children with chronically elevated PbB levels from apparent exceptional neuro-physiological tolerance of PbB intoxication, to some fine motor and cognitive deficits.
A site-specific technique for cross-section transmission electron microscopy specimen preparation of difficult materials is presented. A focused ion beam was used to slice an electron transparent membrane from a specific area of interest within a bulk sample. Micromanipulation lift-out procedures were then used to transport the electron-transparent specimen to a carbon-coated copper grid for subsequent TEM analysis. The FIB (focused ion beam) lift-out technique is a fast method for the preparation of site-specific TEM specimens. The versatility of this technique is demonstrated by presenting cross-sectioned TEM specimens from several types of materials systems, including a multi-layered integrated circuit on a Si substrate, a galvanized steel, a polycrystalline SiC ceramic fiber, and a ZnSe optical ceramic. These specimens have both complex surface geometry and interfaces with complex chemistry. FIB milling was performed sequentially through different layers of cross-sectioned materials so that preferential sputtering was not a factor in preparing TEM specimens. The FIB lift-out method for TEM analysis is a useful technique for the study of complex materials systems for TEM analysis.
When single crystals of two different materials are in contact at a sharp interface, the orientation relationship between them is said to be epitaxial and the configuration of the atoms at the two sides of the interface is such that the lattice mismatch between them is accommodated in the least energetic way. Among other factors, this depends on the bonding between the atoms on the two sides of the interface. In this paper, the relaxation of strain in thin films grown epitaxially on dissimilar substrates is first discussed theoretically for cases of small and large lattice mismatch. In a following section, two metal-ceramics heteroepitaxial systems are investigated in detail by various techniques of transmission electron microscopy. One case, vanadium on MgO, corresponds to a small-mismatched system and the interface changes from coherent to semicoherent above a critical thickness; this turns out to be much larger than the expected value. In the other case-vanadium on the basal and rhombohedral (R) planes of sapphire-the lattice mismatch is large and misfit dislocations exist from the very initial stages of deposition. It is argued that although misfit dislocations in small and large lattice-mismatched systems are geometrically similar, their physical nature is different.