High speed external cavity diode laser concept based on a resonantly driven MEMS scanner for the mid-infrared region.

The rapid detection of trace gases is of great relevance for various spectroscopy applications. In this regard, the technology of external cavity diode lasers (ECDLs) has firmly established itself due to its excellent properties. Outside of the laboratory environment, however, these still have some restrictions, especially with regard to high acquisition rates for sensitive spectroscopy applications and mode-hop-free tuning. In this article, we present our innovative GaSb-based ECDL concept, in which a resonantly driven microelectromechanical system actuator is used. With this, a defined frequency range can be tuned extremely fast and without mode hops. Results of the characterization and its use for the rapid detection of trace gases are presented.

Comparison of the spectral excitation behavior of methane according to InP, GaSb, IC, and QC lasers as excitation source by sensor applications.

The MIR wavelength regime promises better gas detection possibilities than the NIR or the visible region because of the higher absorbencies simulated by HITRAN. In the MIR region are many important absorption lines of significant gases, which are relevant in healthcare, production supervision, and safety and environmental monitoring. One of those gases is methane. CH4 shows significant variations in absorbance with a maximum at 3.3 µm, which results in low detection limits in the range of low ppm. Interband-cascade- and quantum-cascade-based lasers emit at higher wavelengths, where the absorbencies of methane are higher. The comparison is done by analyzing the performance of two spectroscopy applications: tunable diode laser absorption spectroscopy and quartz-enhanced photoacoustic spectroscopy.

Community-based clustering of height in Ethiopia, India, Peru, and Vietnam.

OBJECTIVES: Human growth and final height are influenced by many factors such as genetics, nutrition, living conditions, socioeconomic background and, as recently proposed, by social peer groups and the community. In this paper, we aim to evaluate the extent to which spatial proximity, acting as a proxy for the social community, causes height clustering in low and middle income countries. MATERIAL AND METHODS: We analyzed data from the study "Young Lives-Measuring Child Poverty and Health", a study performed in four low and middle income countries (Ethiopia, India, Peru and Vietnam) to describe the health situation of children. We used linear mixed effects models with different random effect structures to analyze the influence of the community on clustering of height in boys and girls. RESULTS: In all analyzed low and middle income countries, linear mixed effects with hierarchical structures with communities nested within regions provide a better fit than the basic models neglecting community-based clustering (p < .001). DISCUSSION: Although the underlying mechanisms require future research, spatial proximity arising from clustering needs to be integrated into explorative modelling of height variability in humans.

Single mode GaSb diode lasers for sensor applications in a long wavelength regime.

The wavelength, λ, range of 1.8 µm≤λ≤3.5 µm contains strong spectral absorption lines of many gases used in health, industry, safety, and medicine and whose sensitive and quantitative detection is desirable. However, the performance of InP diode lasers markedly deteriorates beyond λ∼2 µm. In this paper we present new results on developing tunable high power single mode laser diodes based on the GaSb material system with emission in the wavelength range of 1.8 µm≤λ≤2.2 µm.

Synthetic growth reference charts.

OBJECTIVES: To reanalyze the between-population variance in height, weight, and body mass index (BMI), and to provide a globally applicable technique for generating synthetic growth reference charts. METHODS: Using a baseline set of 196 female and 197 male growth studies published since 1831, common factors of height, weight, and BMI are extracted via Principal Components separately for height, weight, and BMI. Combining information from single growth studies and the common factors using in principle a Bayesian rationale allows for provision of completed reference charts. RESULTS: The suggested approach can be used for generating synthetic growth reference charts with LMS values for height, weight, and BMI, from birth to maturity, from any limited set of height and weight measurements of a given population. CONCLUSION: Generating synthetic growth reference charts by incorporating information from a large set of reference growth studies seems suitable for populations with no autochthonous references at hand yet.

Stunted Growth. Proceedings of the 23rd Aschauer Soiree, Held at Aschauhof, Germany, November 7th 2015.

Twenty-four scientists met at Aschauhof, Altenhof, Germany, to discuss the associations between child growth and development, and nutrition, health, environment and psychology. Meta-analyses of body height, height variability and household inequality, in historic and modern growth studies published since 1794, highlighting the enormously flexible patterns of child and adolescent height and weight increments throughout history which do not only depend on genetics, prenatal development, nutrition, health, and economic circumstances, but reflect social interactions. A Quality of Life in Short Stature Youth Questionnaire was presented to cross-culturally assess health-related quality of life in children. Changes of child body proportions in recent history, the relation between height and longevity in historic Dutch samples and also measures of body height in skeletal remains belonged to the topics of this meeting. Bayesian approaches and Monte Carlo simulations offer new statistical tools for the study of human growth.

Modeling determinants of growth: evidence for a community-based target in height?

BACKGROUND: Human growth is traditionally envisaged as a target-seeking process regulated by genes, nutrition, health, and the state of an individual's social and economic environment; it is believed that under optimal physical conditions, an individual will achieve his or her full genetic potential. METHODS: Using a panel data set on individual height increments, we suggest a statistical modeling approach that characterizes growth as first-order trend stationary and allows for controlling individual growth tempo via observable measures of individual maturity. A Bayesian framework and corresponding Markov-chain Monte Carlo techniques allowing for a conceptually stringent treatment of missing values are adapted for parameter estimation. RESULTS: The model provides evidence for the adjustment of the individual growth rate toward average height of the population. CONCLUSION: The increase in adult body height during the past 150 y has been explained by the steady improvement of living conditions that are now being considered to have reached an optimum in Western societies. The current investigation questions the notion that the traditional concept in the understanding of this target-seeking process is sufficient. We consider an additional regulator that possibly points at community-based target seeking in growth.

A Bayesian Approach Towards Missing Covariate Data in Multilevel Latent Regression Models.

The measurement of latent traits and investigation of relations between these and a potentially large set of explaining variables is typical in psychology, economics, and the social sciences. Corresponding analysis often relies on surveyed data from large-scale studies involving hierarchical structures and missing values in the set of considered covariates. This paper proposes a Bayesian estimation approach based on the device of data augmentation that addresses the handling of missing values in multilevel latent regression models. Population heterogeneity is modeled via multiple groups enriched with random intercepts. Bayesian estimation is implemented in terms of a Markov chain Monte Carlo sampling approach. To handle missing values, the sampling scheme is augmented to incorporate sampling from the full conditional distributions of missing values. We suggest to model the full conditional distributions of missing values in terms of non-parametric classification and regression trees. This offers the possibility to consider information from latent quantities functioning as sufficient statistics. A simulation study reveals that this Bayesian approach provides valid inference and outperforms complete cases analysis and multiple imputation in terms of statistical efficiency and computation time involved. An empirical illustration using data on mathematical competencies demonstrates the usefulness of the suggested approach.

Dilemmas in choosing and using growth charts.

Human growth is both a target seeking process regulated by genes and environment, and a highly dynamic process that even under similar social and economic circumstances varies considerably both in amplitude (being short or tall) and tempo (maturing fast or slow). This has led to vivid discussions about which growth chart is the right chart to use. In contrast to wide-spread opinions emphasizing the similarity in early childhood growth among diverse ethnic groups, it has become apparent that a single "global" reference fails to adequately mirror the diversity in human growth. In view of the raising evidence that growth is also influenced by the peer group, we refer to novel, cost-effective procedures that facilitate producing growth references "on demand", for limited regional purposes, for ethnically, socio-economically or politically defined minorities, but also for matching geographically different groups of children and adolescents for international growth and registry studies.

Chain Reversion for Detecting Associations in Interacting Variables-St. Nicolas House Analysis.

(1) Background: We present a new statistical approach labeled as "St. Nicolas House Analysis" (SNHA) for detecting and visualizing extensive interactions among variables. (2) Method: We rank absolute bivariate correlation coefficients in descending order according to magnitude and create hierarchic "association chains" defined by sequences where reversing start and end point does not alter the ordering of elements. Association chains are used to characterize dependence structures of interacting variables by a graph. (3) Results: SNHA depicts association chains in highly, but also in weakly correlated data, and is robust towards spurious accidental associations. Overlapping association chains can be visualized as network graphs. Between independent variables significantly fewer associations are detected compared to standard correlation or linear model-based approaches. (4) Conclusion: We propose reversible association chains as a principle to detect dependencies among variables. The proposed method can be conceptualized as a non-parametric statistical method. It is especially suited for secondary data analysis as only aggregate information such as correlations matrices are required. The analysis provides an initial approach for clarifying potential associations that may be subject to subsequent hypothesis testing.

Increasing prevalence of overweight and obesity among children in Vilnius, Lithuania: comparison of two longitudinal data sets of children born in 1990 and 1996.

SUMMARY: The aim of this study was to assess changes in prevalence of overweight and obesity among children born in 1996 and 1990 in Vilnius city. The results were based on comparison of two longitudinal data sets (N = 624 and N = 389) collected from the personal health records of children born in 1996 and 1990 respectively. No statistically significant differences in final height and BMI were established between children born in 1990 and 1996; however, both boys and girls born in 1996 appeared to be higher and heavier at different ages compared to their peers born in 1990. After controlling for tempo, the differences in height between the two cohorts have become insignificant for girls, with exceptions at the age of 3 and 10 years; for boys, the differences between the cohorts have remained significant, however at a slightly lower level. More children born in 1996 tended to be overweight and obese. In six years, the prevalence of overweight in Vilnius children has more than doubled; the prevalence of obesity has increased up to five times in some age groups.

Height and skeletal morphology in relation to modern life style.

Height and skeletal morphology strongly relate to life style. Parallel to the decrease in physical activity and locomotion, modern people are slimmer in skeletal proportions. In German children and adolescents, elbow breadth and particularly relative pelvic breadth (50th centile of bicristal distance divided by body height) have significantly decreased in recent years. Even more evident than the changes in pelvic morphology are the rapid changes in body height in most modern countries since the end-19th and particularly since the mid-20th century. Modern Japanese mature earlier; the age at take-off (ATO, the age at which the adolescent growth spurt starts) decreases, and they are taller at all ages. Preece-Baines modelling of six national samples of Japanese children and adolescents, surveyed between 1955 and 2000, shows that this gain in height is largely an adolescent trend, whereas height at take-off (HTO) increased by less than 3 cm since 1955; adolescent growth (height gain between ATO and adult age) increased by 6 cm. The effect of globalization on the modern post-war Japanese society ("community effect in height") on adolescent growth is discussed.

Sex, Sport, IGF-1 and the Community Effect in Height Hypothesis.

We test the hypothesis that differences in social status between groups of people within a population may induce variation in insulin-like growth factor-1(IGF-1) levels and, by extension, growth in height. This is called the community effect in height hypothesis. The relationship between IGF-1, assessed via finger-prick dried blood spot, and elite level sport competition outcomes were analysed for a sample of 116 undergraduate men and women. There was a statistically significant difference between winners and losers of a competition. Winners, as a group, had higher average pre-game and post-game IGF-1 levels than losers. We proposed this type of difference as a proxy for social dominance. We found no evidence that winners increased in IGF-1 levels over losers or that members of the same team were more similar in IGF-1 levels than they were to players from other teams. These findings provide limited support toward the community effect in height hypothesis. The findings are discussed in relation to the action of the growth hormone/IGF-1 axis as a transducer of multiple bio-social influences into a coherent signal which allows the growing human to adjust and adapt to local ecological conditions.

The impact of physical connectedness on body height in Swiss conscripts.

BACKGROUND: Human populations differ in height. Recent evidence suggests that social networks play an important role in the regulation of adolescent growth and adult height. We further investigated the effect of physical connectedness on height. MATERIAL AND METHODS: We considered Switzerland as a geographic network with 169 nodes (district capitals) and 335 edges (connecting roads) and studied effects of connectedness on height in Swiss conscript from 1884 - 1891, 1908 - 1910, and 2004 - 2009. We also created exponential-family random graph models to separate possible unspecific effects of geographic vicinity. RESULTS: In 1884 - 1891, in 1908 - 1910, and in 2004 - 2009, 1(st), 2(nd) and 3(rd) order neighboring districts significantly correlate in height (p < 0.01). The correlations depend on the order of connectedness, they decline with increasing distance. Short stature districts tend to have short, tall stature districts tend to have tall neighbors. Random network analyses suggest direct road effects on height. Whereas in 1884 - 1891, direct road effects were only visible between 1(st) order neighbors, direct road effects extended to 2(nd) and 3(rd) in 1908 - 1910, and in 2004 - 2009, also to 4(th) order neighbors, and might reflect historic improvements in transportation. The spatial correlations did not significantly change when height was controlled for goiter (1884 - 1889) and for median per capita income (2006), suggesting direct road effects also in goiter-allowed-for height and income-allowed-for height. CONCLUSION: Height in a district depends on height of physically connected neighboring districts. The association decreases with increasing distance in the net. The present data suggest that people can be short because their neighbors are short; or tall because their neighbors are tall (community effect on growth). Psycho-biological effects seem to control growth and development within communities that go far beyond our current understanding of growth regulation.