We present a numerical and theoretical study of intense-field single-electron ionization of helium at 390 nm and 780 nm. Accurate ionization rates (over an intensity range of (0.175–34) × 1014 W cm−2, at 390 nm, and (0.275–14.4) × 1014 W cm−2 at 780 nm) are obtained from full-dimensionality integrations of the time-dependent helium-laser Schrödinger equation. We show that the power law of lowest order perturbation theory, modified with a ponderomotive-shifted ionization potential, is capable of modelling the ionization rates over an intensity range that extends up to two orders of magnitude higher than that applicable to perturbation theory alone. Writing the modified perturbation theory in terms of scaled wavelength and intensity variables, we obtain to first approximation a single ionization law for both the 390 nm and 780 nm cases. To model the data in the high intensity limit as well as in the low, a new function is introduced for the rate. This function has, in part, a resemblance to that derived from tunnelling theory but, importantly, retains the correct frequency-dependence and scaling behaviour derived from the perturbative-like models at lower intensities. Comparison with the predictions of classical ADK tunnelling theory confirms that ADK performs poorly in the frequency and intensity domain treated here.

Background Periodontitis is a major cause of tooth loss globally. Risk factors include age, smoking, and diabetes. Intake of specific nutrients has been associated with periodontitis risk but there has been little research into the influence of overall diet, potentially more relevant when formulating dietary recommendations. Objectives We aimed to investigate potential associations between diet and periodontitis using novel statistical techniques for dietary pattern analysis. Methods Two 24-h dietary recalls and periodontal examination data from the cross-sectional US NHANES, 2009–2014 (n = 10,010), were used. Dietary patterns were extracted using treelet transformation, a data-driven hierarchical clustering and dimension reduction technique. Associations between each pattern [treelet component (TC)] and extent of periodontitis [proportion of sites with clinical attachment loss (CAL) ≥ 3 mm] were estimated using robust logistic quantile regression, adjusting for age, sex, ethnicity, education level, smoking, BMI, and diabetes. Results Eight TCs explained 21% of the variation in diet, 1 of which (TC1) was associated with CAL extent. High TC1 scores represented a diet rich in salad, fruit, vegetables, poultry and seafood, and plain water or tea to drink. There was a substantial negative gradient in CAL extent from the lowest to the highest decile of TC1 (median proportion of sites with CAL ≥ 3 mm: decile 1 = 19.1%, decile 10 = 8.1%; OR, decile 10 compared with decile 1: 0.67; 95% CI: 0.46, 0.99). Conclusions Most dietary patterns identified were not associated with periodontitis extent. One pattern, however, rich in salad, fruit, and vegetables and with plain water or tea to drink, was associated with lower CAL extent. Treelet transformation may be a useful approach for calculating dietary patterns in nutrition research.

In recent years, musty-earthy tastes in drinking water have become a seasonal problem (September to November) for communities that draw their water from the upper St. Lawrence River. The source of the problem is attributed to the presence of geosmin and 2-methylisoborneol (MIB) at concentrations ranging from 5 to 60 ng/L. In 1997 and 1998, the Cornwall Water Purification Plant added granular activated carbon (GAC) to conventional gravity filters to control taste and odour compounds. We report on a study to test the efficiency of these conventional GAC-capped filters to reduce geosmin and MIB concentrations in finished water as a function of filter age, initial chlorine residual and contact time. GAC–capped filters removed on average 60% of the MIB and 80% of the geosmin from the source water after 2 and 12 months of filter operation. However, testing after 24 months operation showed reduced efficiency. Amounts removed ranged between 13 and 20% (15% average) for MIB and 50 to 57% (54% average) for geosmin in these filters. Testing also suggested that filter efficiency was greater with longer contact times and with higher chlorine residuals (in the range 0.1 to 0.6 mg free Cl2/L). In addition to carbon age, chlorine residual and contact time, flow channelization and slow release of the taste and odour compound load (particularly MIB) from the GAC bed may affect apparent filter efficiency.

The aim of this study was to present a concise summary of the oral health policies and oral healthcare schemes for older adult populations in a number of selected countries around the world. In this paper, the current and planned national/regional oral health policies and oral healthcare schemes of nine countries (Australia, Brazil, China including Hong Kong, India, Japan, Switzerland, Thailand, the United Kingdom, and the United States) are reported. Barriers and challenges in oral health promotion in terms of devising oral health policies, implementing oral health schemes, and educating the future dental workforce are discussed. In response to the aging of population, individual countries have initiated or reformed their healthcare systems and developed innovative approaches to deliver oral health services for older adults. There is a global shortage of dentists trained in geriatric dentistry. In many countries, geriatric dentistry is not formally recognized as a specialty. Education and training in geriatric dentistry is needed to produce responsive and competent dental professionals to serve the increasing number of older adults. It is expected that oral health policies and oral healthcare services will be changing and reforming in the coming decades to tackle the enduring oral health challenges of aging societies worldwide.

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