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Notes: Abstract. This study was undertaken to test the hypothesis that gingival inflammation and dental calculus are important determinants of the development and progression of early-onset periodontitis. The study sample included 156 individuals who were 13–20 years old at baseline and who were examined 2× during 6 years to assess the attachment loss, gingival state and the presence of dental calculus. 33 (21%), 62 (40%), and 61 (39%) individuals were classified as having localized, generalized, or incidental EOP, respectively. The results showed an increase in the % of teeth with overt gingivitis and subgingival calculus, and also an increase in the % of teeth showing attachment loss during the 6-year period in ail classification groups. Of teeth with 0–2 mm attachment loss at the beginning of the study and which developed ≥3 mm attachment loss during the following 6 years, there were 2× as many teeth with overt gingival inflammation, and 4× more teeth with subgingival calculus at baseline than teeth without. Gingivitis and subgingival calculus when present at both examinations resulted in a stronger association with the development of new lesions than presence of these variables at baseline. Teeth with gingivitis at baseline had a significantly higher mean attachment loss during 6 years than teeth without gingivitis (p〈0.0001), and teeth with subgingival calculus at baseline had a significantly higher mean attachment loss than teeth without subgingival calculus (p〈0.0001), The presence of gingivitis and subgingival calculus at baseline and 6 years later was associated with the occurrence of even higher disease progression during this period. The association between gingival inflammation and subgingival calculus and the development and progression of attachment loss during the study period in the generalized and the localized EOP groups was significantly higher than the association in the incidental EOP group. In an appreciable % of the sites in all 3 groups, however, the presence of the 2 factors was not associated with attachment loss during 6 years. The results suggest a significant association between gingival inflammation and subgingival calculus and the development and progression of early-onset periodontitis.

Notes: The photochemistry of carbonyl sulfide (OCS) adsorbed to small silver clusters is shown to exhibit a striking odd–even dependence on the number of Ag atoms in the cluster. OCS is found to desorb nondissociatively from even numbered silver clusters. In contrast, on odd silver clusters, a new product channel corresponding to AgnS is observed. Parallels are found with the photochemistry of adsorbates on extended surfaces. Cross-section measurements for OCS desorption from Ag10 and wavelength-dependent measurements of OCS dissociation on Ag9 both indicate that electronic excitation of the cluster initiates chemistry, analogous to substrate mediated surface photochemistry. The size dependence is reasonably explained in terms of a charge-transfer mechanism involving an ion-pair state of the AgnOCS complex. © 1998 American Institute of Physics.

Notes: Vibrational energy distributions in CO2 molecules formed in the catalytic oxidation of CO on platinum have been measured by using a variety of filtering techniques to analyze infrared chemiluminescent emission. For surface temperatures in the range of 650–1100 K the product molecules were vibrationally excited substantially beyond thermal equilibrium with the surface. Emission spectra observed in the 4.3 μm region were significantly red shifted from the fundamental of the asymmetric stretch at 2349 cm−1, indicating that much of the emission originated from higher lying bend–stretch combination states. The vibrational energy of the product, particularly in the asymmetric stretching mode, was sensitive to the coverage of oxygen present on the catalyst surface. These results are consistent with a model in which bending and asymmetric stretching motions contribute strongly to the reaction coordinate for CO oxidation.

Notes: Abstract Cells of N. bacillaris have been selected that are resistant to the toxic proline analogue azetidine-2-carboxylic acid (A2C) in 7% artificial seawater (ASW). This phenotype is stable in the absence of selection pressure. A2C resistance at low salinity was demonstrated to be due to an overproduction of proline in these cells, while levels of other amino acids were unaffected. Both wild-type and A2C-resistant cells respond to growth in high salinity media (100% ASW, 200% ASW) by accumulation of proline, but proline levels at all salinities are higher in the A2C-resistant cells than in the wild-type. Proline overproduction in the A2C-resislant cells did not affect fluctuations in the levels of other salinity-dependent solutes, such as homarine. A mutant with this level of specificity over a wide range of water potentials has not been reported for other plants and algae. Both the wild-type and A2C-resistant cells were able to grow over the entire salinity range tested (7%-300% ASW). However, the A2C-resistant cells showed a lower division rate than the wild-type in 300% ASW, and yield of A2C-resislant cells was lower than yield of wild-type cells at the salinity extremes (7% ASW, 300% ASW). The response or wild-type and A2C-resistant cells to rapid increases in salinity were similar for both growth and photosynthesis. The presence of a constitutive high level of proline in the A2C-resistant cell line did not confer any obvious increased tolerance to salinity shocks, indicating that there are other important factors in the biochemical adaptation to salinity in these cells.

Notes: Six histopathologists allocated 100 sections from patients with long-standing ulcerative colitis into four diagnostic categories, regular hyperplasia, reactive atypia, low-grade and high-grade dysplasia. Their allocations were analysed using kappa statistics, including Fleiss's multiple kappa for groups of observers, and agreement on specific diagnoses was explored by constructing a conditional probability matrix. The nature of their disagreements was investigated using coefficients for systematic and haphazard errors. Over the four diagnostic categories there was a wide range of pairwise agreement from a low of 49% up to 72% and kappa values were only ‘fair’ or ‘moderate’. As expected, agreement over the two categories ‘dysplasia’vs‘no dysplasia’ was better, ranging from 68% to 84%, and for ‘atypia present’ (reactive atypia, low- and high-grade dysplasia) vs‘no atypia’ two pairings achieved over 90% and 11 pairings over 80% agreement. In view of its clinical importance, conditional agreement on high-grade dysplasia was examined. Given that a first observer allocates a case as high-grade dysplasia, pairwise agreement on this diagnosis ranged from 100% down to as low as 33%. However, most of these disagreements fell into the low-grade dysplasia category so that closer follow-up and further biopsies would still have been indicated. It is a truism that the basis for safe management is careful co-operation between clinicians and pathologists who have all the relevant facts and who know and trust one another's judgement. Thus, several aspects of the ideal diagnostic process cannot be evaluated in inter-observer studies and the element of artificiality should be borne in mind when applying the findings to diagnostic practice. Nevertheless, the low level of agreement on the diagnosis of high-grade dysplasia achieved by certain pairings of specialist pathologists is a disturbing outcome of this study. Inaccuracies should be minimized by a concensus approach and we therefore recommend referral of putative cases of dysplasia to interested pathologists for further opinions. We would also advocate that pathologists faced with appearances which are indefinite between reactive atypia and dysplasia, would do better to describe them in terms of ‘atypia, significance uncertain’, so that closer surveillance is undertaken, rather than force them into more precise diagnostic categories which may be incorrect.

Notes: Upper airway patency can be compromised when children (or adults) receive sedative medication. The study examines the effect of two different positioning techniques (use of the ‘sniff position pillow’ (SPP) and shoulder elevation (SE) on maintenance of upper airway patency using MRI in 21 children sedated with intravenous pentobarbital (5–8 mg·kg-1). Children positioned on the SPP had a significantly greater degree of atlanto-occipital extension (P 〈 0.05), and a significantly greater nasopharyngeal diameter (P 〈 0.05) than those with shoulder elevation. The degree of atlanto-occipital extension was not significantly correlated with pharyngeal diameter (R = -0.68). No clinical signs of upper airway obstruction were noted and oxygen desaturation did not occur. Both positioning techniques were consistently associated with upper airway patency under the study conditions described. In obligate nose breathers to whom sedative agents are administered, the SPP is more likely to maintain nasopharyngeal patency than shoulder elevation.