Comment: Distinguishing Cohort Effects from Age*Period Effects on Non-Marital Fertility

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Martin, Steve

2009-01-01

In the article "Cohort Effects on Non-marital Fertility," in this issue of "Social Forces," Jean Stockard employs a novel strategy for disentangling cohort, period, and age effects on the non-marital fertility ratio. In a model with fixed-effect controls for age and for time period, the author documents evidence for three cohort-specific factors…

Decomposable log-linear models

DEFF Research Database (Denmark)

Eriksen, Poul Svante

can be characterized by a structured set of conditional independencies between some variables given some other variables. We term the new model class decomposable log-linear models, which is illustrated to be a much richer class than decomposable graphical models.It covers a wide range of non...... The present paper considers discrete probability models with exact computational properties. In relation to contingency tables this means closed form expressions of the maksimum likelihood estimate and its distribution. The model class includes what is known as decomposable graphicalmodels, which......-hierarchical models, models with structural zeroes, models described by quasi independence and models for level merging. Also, they have a very natural interpretation as they may be formulated by a structured set of conditional independencies between two events given some other event. In relation to contingency...

Separating the effects of age, period and birth cohort on seafood consumption in Norway

DEFF Research Database (Denmark)

Scholderer, Joachim; Trondsen, Torbjørn; Lund, Eiliv

Effects of age, period and birth cohort on consumption of fat fish, lean fish and processed fish were estimated based on panel data from the Norwegian Women and Seafood Consumption Study (NOWAC). Cohorts selected for the present analysis were women born between 1951 and 1966. Survey questionnaires...... fish increased between 1996 and 2001, while consumption of lean fish decreased. All three period effects were stable across birth cohorts. Estimation of polynomial contrasts indicated that birth cohort itself had linear effects on consumption, with older generations consuming significantly more fat...... and lean fish, but less processed fish than younger generations. Finally, the effects of cohort and period on consumption of lean and processed fish remained stable when biological age was controlled for, whilst the effect of period on fat fish consumption vanished. Regarding total consumption of fat fish...

A class of non-linear exposure-response models suitable for health impact assessment applicable to large cohort studies of ambient air pollution.

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Nasari, Masoud M; Szyszkowicz, Mieczysław; Chen, Hong; Crouse, Daniel; Turner, Michelle C; Jerrett, Michael; Pope, C Arden; Hubbell, Bryan; Fann, Neal; Cohen, Aaron; Gapstur, Susan M; Diver, W Ryan; Stieb, David; Forouzanfar, Mohammad H; Kim, Sun-Young; Olives, Casey; Krewski, Daniel; Burnett, Richard T

2016-01-01

The effectiveness of regulatory actions designed to improve air quality is often assessed by predicting changes in public health resulting from their implementation. Risk of premature mortality from long-term exposure to ambient air pollution is the single most important contributor to such assessments and is estimated from observational studies generally assuming a log-linear, no-threshold association between ambient concentrations and death. There has been only limited assessment of this assumption in part because of a lack of methods to estimate the shape of the exposure-response function in very large study populations. In this paper, we propose a new class of variable coefficient risk functions capable of capturing a variety of potentially non-linear associations which are suitable for health impact assessment. We construct the class by defining transformations of concentration as the product of either a linear or log-linear function of concentration multiplied by a logistic weighting function. These risk functions can be estimated using hazard regression survival models with currently available computer software and can accommodate large population-based cohorts which are increasingly being used for this purpose. We illustrate our modeling approach with two large cohort studies of long-term concentrations of ambient air pollution and mortality: the American Cancer Society Cancer Prevention Study II (CPS II) cohort and the Canadian Census Health and Environment Cohort (CanCHEC). We then estimate the number of deaths attributable to changes in fine particulate matter concentrations over the 2000 to 2010 time period in both Canada and the USA using both linear and non-linear hazard function models.

Defining a Family of Cognitive Diagnosis Models Using Log-Linear Models with Latent Variables

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Henson, Robert A.; Templin, Jonathan L.; Willse, John T.

2009-01-01

This paper uses log-linear models with latent variables (Hagenaars, in "Loglinear Models with Latent Variables," 1993) to define a family of cognitive diagnosis models. In doing so, the relationship between many common models is explicitly defined and discussed. In addition, because the log-linear model with latent variables is a general model for…

Age, Period, and Cohort Differences in Work Centrality and Work Values

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Gábor Hajdu

2018-02-01

Full Text Available In this paper, we analyze whether work values differ between three dimensions of time (age, birth cohort, period. Using data of five waves of the World Values Survey and the European Values Study from more than forty countries and hierarchical age-period-cohort regression models, we did not find relevant gaps between birth cohorts with respect to the relative importance of work or with respect to work values. Thus, we claim that, in European and Euro-Atlantic countries, birth cohorts, on average, do not differ significantly with regard to their work values. Our results suggest, however, that the relative importance of work is significantly higher in the middle-age groups than among the younger or older groups. Regarding work values, we found that the importance of having an interesting job, good pay, and good hours decreases with age, and that job security is equally important at every age, whereas the importance of having a useful job increases with age.

Patterns of lung cancer mortality in 23 countries: Application of the Age-Period-Cohort model

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Huang Yi-Chia

2005-03-01

Full Text Available Abstract Background Smoking habits do not seem to be the main explanation of the epidemiological characteristics of female lung cancer mortality in Asian countries. However, Asian countries are often excluded from studies of geographical differences in trends for lung cancer mortality. We thus examined lung cancer trends from 1971 to 1995 among men and women for 23 countries, including four in Asia. Methods International and national data were used to analyze lung cancer mortality from 1971 to 1995 in both sexes. Age-standardized mortality rates (ASMR were analyzed in five consecutive five-year periods and for each five-year age group in the age range 30 to 79. The age-period-cohort (APC model was used to estimate the period effect (adjusted for age and cohort effects for mortality from lung cancer. Results The sex ratio of the ASMR for lung cancer was lower in Asian countries, while the sex ratio of smoking prevalence was higher in Asian countries. The mean values of the sex ratio of the ASMR from lung cancer in Taiwan, Hong Kong, Singapore, and Japan for the five 5-year period were 2.10, 2.39, 3.07, and 3.55, respectively. These values not only remained quite constant over each five-year period, but were also lower than seen in the western countries. The period effect, for lung cancer mortality as derived for the 23 countries from the APC model, could be classified into seven patterns. Conclusion Period effects for both men and women in 23 countries, as derived using the APC model, could be classified into seven patterns. Four Asian countries have a relatively low sex ratio in lung cancer mortality and a relatively high sex ratio in smoking prevalence. Factors other than smoking might be important, especially for women in Asian countries.

Age, period and cohort influences on beer, wine and spirits consumption trends in the US National Alcohol Surveys.

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Kerr, William C; Greenfield, Thomas K; Bond, Jason; Ye, Yu; Rehm, Jürgen

2004-09-01

To estimate the separate influences of age, period and cohort on the consumption of beer wine and spirits in the United States. Linear age-period-cohort models controlling for demographic change with extensive specification testing. Setting US general population 1979-2000. Monthly average of past-year consumption of beer, wine and spirits in five National Alcohol Surveys. Findings The strongest cohort effects are found for spirits; cohorts born before 1940 are found to have significantly higher consumption than those born after 1946, with especially high spirits consumption for men in the pre-1930s cohorts. Significant cohort effects are also found for beer with elevated consumption in the 1946-65 cohorts for men but in the pre-1940 cohorts for women. Significant negative effects of age are found for beer and spirits consumption, although not for wine. Significant period effects are found for men's beer and wine consumption and for women's spirits consumption. Increased educational attainment in the population over time is associated with reduced beer consumption and increased wine consumption. Changing cohort demographics are found to have significant effects on beverage-specific consumption, indicating the importance of controlling for these effects in the evaluation of alcohol policy effectiveness and the potential for substantial improvement in the forecasting of future beverage-specific consumption trends, alcohol dependence treatment demand and morbidity and mortality outcomes.

Log-normal frailty models fitted as Poisson generalized linear mixed models.

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Hirsch, Katharina; Wienke, Andreas; Kuss, Oliver

2016-12-01

The equivalence of a survival model with a piecewise constant baseline hazard function and a Poisson regression model has been known since decades. As shown in recent studies, this equivalence carries over to clustered survival data: A frailty model with a log-normal frailty term can be interpreted and estimated as a generalized linear mixed model with a binary response, a Poisson likelihood, and a specific offset. Proceeding this way, statistical theory and software for generalized linear mixed models are readily available for fitting frailty models. This gain in flexibility comes at the small price of (1) having to fix the number of pieces for the baseline hazard in advance and (2) having to "explode" the data set by the number of pieces. In this paper we extend the simulations of former studies by using a more realistic baseline hazard (Gompertz) and by comparing the model under consideration with competing models. Furthermore, the SAS macro %PCFrailty is introduced to apply the Poisson generalized linear mixed approach to frailty models. The simulations show good results for the shared frailty model. Our new %PCFrailty macro provides proper estimates, especially in case of 4 events per piece. The suggested Poisson generalized linear mixed approach for log-normal frailty models based on the %PCFrailty macro provides several advantages in the analysis of clustered survival data with respect to more flexible modelling of fixed and random effects, exact (in the sense of non-approximate) maximum likelihood estimation, and standard errors and different types of confidence intervals for all variance parameters. Copyright © 2016 Elsevier Ireland Ltd. All rights reserved.

Life-course and cohort trajectories of mental health in the UK, 1991-2008--a multilevel age-period-cohort analysis.

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Bell, Andrew

2014-11-01

There is ongoing debate regarding the shape of life-course trajectories in mental health. Many argue the relationship is U-shaped, with mental health declining with age to mid-life, then improving. However, I argue that these models are beset by the age-period-cohort (APC) identification problem, whereby age, cohort and year of measurement are exactly collinear and their effects cannot be meaningfully separated. This means an apparent life-course effect could be explained by cohorts. This paper critiques two sets of literature: the substantive literature regarding life-course trajectories in mental health, and the methodological literature that claims erroneously to have 'solved' the APC identification problem statistically (e.g. using Yang and Land's Hierarchical APC-HAPC-model). I then use a variant of the HAPC model, making strong but justified assumptions that allow the modelling of life-course trajectories in mental health (measured by the General Health Questionnaire) net of any cohort effects, using data from the British Household Panel Survey, 1991-2008. The model additionally employs a complex multilevel structure that allows the relative importance of spatial (households, local authority districts) and temporal (periods, cohorts) levels to be assessed. Mental health is found to increase throughout the life-course; this slows at mid-life before worsening again into old age, but there is no evidence of a U-shape--I argue that such findings result from confounding with cohort processes (whereby more recent cohorts have generally worse mental health). Other covariates were also evaluated; income, smoking, education, social class, urbanity, ethnicity, gender and marriage were all related to mental health, with the latter two in particular affecting life-course and cohort trajectories. The paper shows the importance of understanding APC in life-course research generally, and mental health research in particular. Copyright © 2014 Elsevier Ltd. All rights

Reconciling the Log-Linear and Non-Log-Linear Nature of the TSH-Free T4 Relationship: Intra-Individual Analysis of a Large Population.

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Rothacker, Karen M; Brown, Suzanne J; Hadlow, Narelle C; Wardrop, Robert; Walsh, John P

2016-03-01

The TSH-T4 relationship was thought to be inverse log-linear, but recent cross-sectional studies report a complex, nonlinear relationship; large, intra-individual studies are lacking. Our objective was to analyze the TSH-free T4 relationship within individuals. We analyzed data from 13 379 patients, each with six or more TSH/free T4 measurements and at least a 5-fold difference between individual median TSH and minimum or maximum TSH. Linear and nonlinear regression models of log TSH on free T4 were fitted to data from individuals and goodness of fit compared by likelihood ratio testing. Comparing all models, the linear model achieved best fit in 31% of individuals, followed by quartic (27%), cubic (15%), null (12%), and quadratic (11%) models. After eliminating least favored models (with individuals reassigned to best fitting, available models), the linear model fit best in 42% of participants, quartic in 43%, and null model in 15%. As the number of observations per individual increased, so did the proportion of individuals in whom the linear model achieved best fit, to 66% in those with more than 20 observations. When linear models were applied to all individuals and averaged according to individual median free T4 values, variations in slope and intercept indicated a nonlinear log TSH-free T4 relationship across the population. The log TSH-free T4 relationship appears linear in some individuals and nonlinear in others, but is predominantly linear in those with the largest number of observations. A log-linear relationship within individuals can be reconciled with a non-log-linear relationship in a population.

Modelling regional variation of first-time births in Denmark 1980-1994 by an age-period-cohort model

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Lisbeth B. Knudsen

2005-12-01

Full Text Available Despite the small size of Denmark, there have traditionally been rather consistent regional differences in fertility rates. We apply the statistical age-period-cohort model to include the effect of these three time-related factors thereby concisely illuminating the regional differences of first-time births in Denmark. From the Fertility of Women and Couples Dataset we obtain data on number of births by nulliparous women by year (1980-1994, age (15-45 and county of residence. We show that the APC-model describes the fertility rates of nulliparous women satisfactorily. To catch the regional variation an interaction parameter between age and county is necessary, which provides a surprisingly good description suggesting that the county-specific age-distributions of first-time fertility rates differ. Our results are in general agreement with the 'moral geography' concepts of Tonboe (2001.

Modelling regional variation of first-time births in Denmark 1980-1994 by an age-period-cohort model

DEFF Research Database (Denmark)

Thygesen, Lau Caspar; Knudsen, Lisbeth B.; Keiding, Niels

2005-01-01

Despite the small size of Denmark, there have traditionally been rather consistent regional differences in fertility rates. We apply the statistical age-period-cohort model to include the effect of these three time-related factors thereby concisely illuminating the regional differences of first......-time births in Denmark. From the Fertility of Women and Couples Dataset we obtain data on number of births by nulliparous women by year (1980-1994), age (15-45) and county of residence. We show that the APC-model describes the fertility rates of nulliparous women satisfactorily. To catch the regional...... variation an interaction parameter between age and county is necessary, which provides a surprisingly good description suggesting that the county-specific age-distributions of first-time fertility rates differ. Our results are in general agreement with the 'moral geography' concepts of Tonboe (2001)....

Mortality of breast cancer in Taiwan, 1971-2010: temporal changes and an age-period-cohort analysis.

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Ho, M-L; Hsiao, Y-H; Su, S-Y; Chou, M-C; Liaw, Y-P

2015-01-01

The current paper describes the age, period and cohort effects on breast cancer mortality in Taiwan. Female breast cancer mortality data were collected from the Taiwan death registries for 1971-2010. The annual percentage changes, age- standardised mortality rates (ASMR) and age-period-cohort model were calculated. The mortality rates increased with advancing age groups when fixing the period. The percentage change in the breast cancer mortality rate increased from 54.79% at aged 20-44 years, to 149.78% in those aged 45-64 years (between 1971-75 and 2006-10). The mortality rates in the 45-64 age group increased steadily from 1971 to 1975 and 2006-10. The 1951 birth cohorts (actual birth cohort; 1947-55) showed peak mortalities in both the 50-54 and 45-49 age groups. We found that the 1951 birth cohorts had the greatest mortality risk from breast cancer. This might be attributed to the DDT that was used in large amounts to prevent deaths from malaria in Taiwan. However, future researches require DDT data to evaluate the association between breast cancer and DDT use.

Support for Marijuana (Cannabis Legalization: Untangling Age, Period, and Cohort Effects

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William Campbell

2017-02-01

Full Text Available In three large, nationally representative surveys of U.S. 12th graders, college students, and adults ('N' = 9 million conducted 1968–2015, Americans became significantly more supportive of legal marijuana (cannabis starting in the mid-1980’s. Hierarchical models using age-period-cohort analysis on the adult (General Social Survey sample showed that the increased support for legalization is primarily a time period effect rather than generational or age effect; thus, Americans of all ages became more supportive of legal marijuana. Among 12th graders, support for marijuana legalization was closely linked to perceptions of marijuana safety.

Age-period-cohort analysis of infectious disease mortality in urban-rural China, 1990-2010.

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Li, Zhi; Wang, Peigang; Gao, Ge; Xu, Chunling; Chen, Xinguang

2016-03-31

Although a number of studies on infectious disease trends in China exist, these studies have not distinguished the age, period, and cohort effects simultaneously. Here, we analyze infectious disease mortality trends among urban and rural residents in China and distinguish the age, period, and cohort effects simultaneously. Infectious disease mortality rates (1990-2010) of urban and rural residents (5-84 years old) were obtained from the China Health Statistical Yearbook and analyzed with an age-period-cohort (APC) model based on Intrinsic Estimator (IE). Infectious disease mortality is relatively high at age group 5-9, reaches a minimum in adolescence (age group 10-19), then rises with age, with the growth rate gradually slowing down from approximately age 75. From 1990 to 2010, except for a slight rise among urban residents from 2000 to 2005, the mortality of Chinese residents experienced a substantial decline, though at a slower pace from 2005 to 2010. In contrast to the urban residents, rural residents experienced a rapid decline in mortality during 2000 to 2005. The mortality gap between urban and rural residents substantially narrowed during this period. Overall, later birth cohorts experienced lower infectious disease mortality risk. From the 1906-1910 to the 1941-1945 birth cohorts, the decrease of mortality among urban residents was significantly faster than that of subsequent birth cohorts and rural counterparts. With the rapid aging of the Chinese population, the prevention and control of infectious disease in elderly people will present greater challenges. From 1990 to 2010, the infectious disease mortality of Chinese residents and the urban-rural disparity have experienced substantial declines. However, the re-emergence of previously prevalent diseases and the emergence of new infectious diseases created new challenges. It is necessary to further strengthen screening, immunization, and treatment for the elderly and for older cohorts at high risk.

The bystander effect model of Brenner and Sachs fitted to lung cancer data in 11 cohorts of underground miners, and equivalence of fit of a linear relative risk model with adjustment for attained age and age at exposure

International Nuclear Information System (INIS)

Little, M P

2004-01-01

Bystander effects following exposure to α-particles have been observed in many experimental systems, and imply that linearly extrapolating low dose risks from high dose data might materially underestimate risk. Brenner and Sachs (2002 Int. J. Radiat. Biol. 78 593-604; 2003 Health Phys. 85 103-8) have recently proposed a model of the bystander effect which they use to explain the inverse dose rate effect observed for lung cancer in underground miners exposed to radon daughters. In this paper we fit the model of the bystander effect proposed by Brenner and Sachs to 11 cohorts of underground miners, taking account of the covariance structure of the data and the period of latency between the development of the first pre-malignant cell and clinically overt cancer. We also fitted a simple linear relative risk model, with adjustment for age at exposure and attained age. The methods that we use for fitting both models are different from those used by Brenner and Sachs, in particular taking account of the covariance structure, which they did not, and omitting certain unjustifiable adjustments to the miner data. The fit of the original model of Brenner and Sachs (with 0 y period of latency) is generally poor, although it is much improved by assuming a 5 or 6 y period of latency from the first appearance of a pre-malignant cell to cancer. The fit of this latter model is equivalent to that of a linear relative risk model with adjustment for age at exposure and attained age. In particular, both models are capable of describing the observed inverse dose rate effect in this data set

Trends in ischemic heart disease mortality in Korea, 1985-2009: an age-period-cohort analysis.

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Lee, Hye Ah; Park, Hyesook

2012-09-01

Economic growth and development of medical technology help to improve the average life expectancy, but the western diet and rapid conversions to poor lifestyles lead an increasing risk of major chronic diseases. Coronary heart disease mortality in Korea has been on the increase, while showing a steady decline in the other industrialized countries. An age-period-cohort analysis can help understand the trends in mortality and predict the near future. We analyzed the time trends of ischemic heart disease mortality, which is on the increase, from 1985 to 2009 using an age-period-cohort model to characterize the effects of ischemic heart disease on changes in the mortality rate over time. All three effects on total ischemic heart disease mortality were statistically significant. Regarding the period effect, the mortality rate was decreased slightly in 2000 to 2004, after it had continuously increased since the late 1980s that trend was similar in both sexes. The expected age effect was noticeable, starting from the mid-60's. In addition, the age effect in women was more remarkable than that in men. Women born from the early 1900s to 1925 observed an increase in ischemic heart mortality. That cohort effect showed significance only in women. The future cohort effect might have a lasting impact on the risk of ischemic heart disease in women with the increasing elderly population, and a national prevention policy is need to establish management of high risk by considering the age-period-cohort effect.

The marriage boom and marriage bust in the United States: An age-period-cohort analysis.

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Schellekens, Jona

2017-03-01

In the 1950s and 1960s there was an unprecedented marriage boom in the United States. This was followed in the 1970s by a marriage bust. Some argue that both phenomena are cohort effects, while others argue that they are period effects. The study reported here tested the major period and cohort theories of the marriage boom and bust, by estimating an age-period-cohort model of first marriage for the years 1925-79 using census microdata. The results of the analysis indicate that the marriage boom was mostly a period effect, although there were also cohort influences. More specifically, the hypothesis that the marriage boom was mostly a response to rising wages is shown to be consistent with the data. However, much of the marriage bust can be accounted for by unidentified cohort influences, at least until 1980.

Effects of age, time period, and birth cohort on the prevalence of diabetes and obesity in Korean men.

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Kwon, Jin-Won; Song, Yun-mi; Park, Hye soon; Sung, Joohon; Kim, Ho; Cho, Sung-il

2008-02-01

We examined changes in the prevalence of diabetes, obesity, and overweight in 412,881 Korean men in birth cohorts from 1933 to 1972 over 8 years from 1992 to 2000 and separately analyzed the effects of age, time period, and birth cohort. The study included male employees of Korean government organizations and schools who were between 20 and 59 years of age in 1992. Diabetes was diagnosed on the basis of self-reports in 1992 or fasting blood glucose levels (>or=126 mg/ml, 7.0 mmol/l). The age-period-cohort model was used to estimate the effects of age, time period, and birth cohort. In Korean male birth cohorts from 1933 to 1972, the age-specific prevalence of diabetes, obesity, and overweight in men aged 28-59 years increased annually by 0.41% (3.03 to 6.29%), 0.18% (0.70 to 2.16%), and 1.49% (23.48 to 35.41%), respectively, from 1992 to 2000. The relative change in diabetes was largest among the younger cohorts (>400% increase over 8 years) and corresponded to the change in obesity. Apart from the contribution of age, clear cohort and period effects were evident for diabetes, although the magnitude of the effect was slightly less than that for obesity. Prevention of diabetes through the control of obesity, particularly in young men, clearly needs to be emphasized.

Life satisfaction and age : Dealing with underidentification in age-period-cohort models

NARCIS (Netherlands)

de Ree, Joppe; Alessie, Rob

Recent literature typically finds a U shaped relationship between life satisfaction and age. Age profiles, however, are not identified without forcing arbitrary restrictions on the cohort and/or time profiles. In this paper we report what can be identified about the relationship between life

Sexual Inactivity During Young Adulthood Is More Common Among U.S. Millennials and iGen: Age, Period, and Cohort Effects on Having No Sexual Partners After Age 18.

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Twenge, Jean M; Sherman, Ryne A; Wells, Brooke E

2017-02-01

Examining age, time period, and cohort/generational changes in sexual experience is key to better understanding sociocultural influences on sexuality and relationships. Americans born in the 1980s and 1990s (commonly known as Millennials and iGen) were more likely to report having no sexual partners as adults compared to GenX'ers born in the 1960s and 1970s in the General Social Survey, a nationally representative sample of American adults (N = 26,707). Among those aged 20-24, more than twice as many Millennials born in the 1990s (15 %) had no sexual partners since age 18 compared to GenX'ers born in the 1960s (6 %). Higher rates of sexual inactivity among Millennials and iGen also appeared in analyses using a generalized hierarchical linear modeling technique known as age-period-cohort analysis to control for age and time period effects among adults of all ages. Americans born early in the 20th century also showed elevated rates of adult sexual inactivity. The shift toward higher rates of sexual inactivity among Millennials and iGen'ers was more pronounced among women and absent among Black Americans and those with a college education. Contrary to popular media conceptions of a "hookup generation" more likely to engage in frequent casual sex, a higher percentage of Americans in recent cohorts, particularly Millennials and iGen'ers born in the 1990s, had no sexual partners after age 18.

Maternal mortality in Mexico, beyond millennial development objectives: An age-period-cohort model.

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Rodríguez-Aguilar, Román

2018-01-01

The maternal mortality situation is analyzed in México as an indicator that reflects the social development level of the country and was one of the millennial development objectives. The effect of a maternal death in the related social group has multiplier effects, since it involves family dislocation, economic impact and disruption of the orphans' normal social development. Two perspectives that causes of maternal mortality were analyzed, on one hand, their relationship with social determinants and on the other, factors directly related to the health system. Evidence shows that comparing populations based on group of selected variables according to social conditions and health care access, statistically significant differences prevail according to education and marginalization levels, and access to medical care. In addition, the Age-Period-Cohort model raised, shows significant progress in terms of a downward trend in maternal mortality in a generational level. Those women born before 1980 had a greater probability of maternal death in relation to recent generations, which is a reflection of the improvement in social determinants and in the Health System. The age effect shows a problem in maternal mortality in women under 15 years old, so teen pregnancy is a priority in health and must be addressed in short term. There is no clear evidence of a period effect.

Comparing Multiple-Group Multinomial Log-Linear Models for Multidimensional Skill Distributions in the General Diagnostic Model. Research Report. ETS RR-08-35

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Xu, Xueli; von Davier, Matthias

2008-01-01

The general diagnostic model (GDM) utilizes located latent classes for modeling a multidimensional proficiency variable. In this paper, the GDM is extended by employing a log-linear model for multiple populations that assumes constraints on parameters across multiple groups. This constrained model is compared to log-linear models that assume…

Log Linear Models for Religious and Social Factors affecting the practice of Family Planning Methods in Lahore, Pakistan

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Farooq Ahmad

2006-01-01

Full Text Available This is cross sectional study based on 304 households (couples with wives age less than 48 years, chosen from urban locality (city Lahore. Fourteen religious, demographic and socio-economic factors of categorical nature like husband education, wife education, husband’s monthly income, occupation of husband, household size, husband-wife discussion, number of living children, desire for more children, duration of marriage, present age of wife, age of wife at marriage, offering of prayers, political view, and religiously decisions were taken to understand acceptance of family planning. Multivariate log-linear analysis was applied to identify association pattern and interrelationship among factors. The logit model was applied to explore the relationship between predictor factors and dependent factor, and to explore which are the factors upon which acceptance of family planning is highly depending. Log-linear analysis demonstrate that preference of contraceptive use was found to be consistently associated with factors Husband-Wife discussion, Desire for more children, No. of children, Political view and Duration of married life. While Husband’s monthly income, Occupation of husband, Age of wife at marriage and Offering of prayers resulted in no statistical explanation of adoption of family planning methods.

A new approach to age-period-cohort analysis using partial least squares regression: the trend in blood pressure in the Glasgow Alumni cohort.

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Yu-Kang Tu

2011-04-01

Full Text Available Due to a problem of identification, how to estimate the distinct effects of age, time period and cohort has been a controversial issue in the analysis of trends in health outcomes in epidemiology. In this study, we propose a novel approach, partial least squares (PLS analysis, to separate the effects of age, period, and cohort. Our example for illustration is taken from the Glasgow Alumni cohort. A total of 15,322 students (11,755 men and 3,567 women received medical screening at the Glasgow University between 1948 and 1968. The aim is to investigate the secular trends in blood pressure over 1925 and 1950 while taking into account the year of examination and age at examination. We excluded students born before 1925 or aged over 25 years at examination and those with missing values in confounders from the analyses, resulting in 12,546 and 12,516 students for analysis of systolic and diastolic blood pressure, respectively. PLS analysis shows that both systolic and diastolic blood pressure increased with students' age, and students born later had on average lower blood pressure (SBP: -0.17 mmHg/per year [95% confidence intervals: -0.19 to -0.15] for men and -0.25 [-0.28 to -0.22] for women; DBP: -0.14 [-0.15 to -0.13] for men; -0.09 [-0.11 to -0.07] for women. PLS also shows a decreasing trend in blood pressure over the examination period. As identification is not a problem for PLS, it provides a flexible modelling strategy for age-period-cohort analysis. More emphasis is then required to clarify the substantive and conceptual issues surrounding the definitions and interpretations of age, period and cohort effects.

An international contrast of rates of placental abruption: an age-period-cohort analysis.

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Ananth, Cande V; Keyes, Katherine M; Hamilton, Ava; Gissler, Mika; Wu, Chunsen; Liu, Shiliang; Luque-Fernandez, Miguel Angel; Skjærven, Rolv; Williams, Michelle A; Tikkanen, Minna; Cnattingius, Sven

2015-01-01

Although rare, placental abruption is implicated in disproportionately high rates of perinatal morbidity and mortality. Understanding geographic and temporal variations may provide insights into possible amenable factors of abruption. We examined abruption frequencies by maternal age, delivery year, and maternal birth cohorts over three decades across seven countries. Women that delivered in the US (n = 863,879; 1979-10), Canada (4 provinces, n = 5,407,463; 1982-11), Sweden (n = 3,266,742; 1978-10), Denmark (n = 1,773,895; 1978-08), Norway (n = 1,780,271, 1978-09), Finland (n = 1,411,867; 1987-10), and Spain (n = 6,151,508; 1999-12) were analyzed. Abruption diagnosis was based on ICD coding. Rates were modeled using Poisson regression within the framework of an age-period-cohort analysis, and multi-level models to examine the contribution of smoking in four countries. Abruption rates varied across the seven countries (3-10 per 1000), Maternal age showed a consistent J-shaped pattern with increased rates at the extremes of the age distribution. In comparison to births in 2000, births after 2000 in European countries had lower abruption rates; in the US there was an increase in rate up to 2000 and a plateau thereafter. No birth cohort effects were evident. Changes in smoking prevalence partially explained the period effect in the US (P = 0.01) and Sweden (Prate has plateaued since 2000 in the US, all other countries show declining rates. These findings suggest considerable variation in abruption frequencies across countries; differences in the distribution of risk factors, especially smoking, may help guide policy to reduce abruption rates.

Decomposing the effects of time on the social acceptability of biotechnology using age-period-cohort-country models.

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Rousselière, Damien; Rousselière, Samira

2017-08-01

The study of European attitudes toward biotechnologies underlines a situation that is relatively contrasting in Europe. However, as different effects of time can influence the social attitudes (a life-cycle effect, a generational effect, and an exogenous temporal effect potentially affecting the entire population), an appropriate methodology should be used. To this end, age-period-cohort-country models have thus been estimated based on Eurobarometer data from 1991 onward. Applied to different data subsets, these models give similar results underlining the importance of the life-cycle effects as well as the heterogeneity of the link between political affiliation and biotechnologies attitudes across the European countries.

An international contrast of rates of placental abruption: an age-period-cohort analysis.

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Cande V Ananth

Full Text Available Although rare, placental abruption is implicated in disproportionately high rates of perinatal morbidity and mortality. Understanding geographic and temporal variations may provide insights into possible amenable factors of abruption. We examined abruption frequencies by maternal age, delivery year, and maternal birth cohorts over three decades across seven countries.Women that delivered in the US (n = 863,879; 1979-10, Canada (4 provinces, n = 5,407,463; 1982-11, Sweden (n = 3,266,742; 1978-10, Denmark (n = 1,773,895; 1978-08, Norway (n = 1,780,271, 1978-09, Finland (n = 1,411,867; 1987-10, and Spain (n = 6,151,508; 1999-12 were analyzed. Abruption diagnosis was based on ICD coding. Rates were modeled using Poisson regression within the framework of an age-period-cohort analysis, and multi-level models to examine the contribution of smoking in four countries.Abruption rates varied across the seven countries (3-10 per 1000, Maternal age showed a consistent J-shaped pattern with increased rates at the extremes of the age distribution. In comparison to births in 2000, births after 2000 in European countries had lower abruption rates; in the US there was an increase in rate up to 2000 and a plateau thereafter. No birth cohort effects were evident. Changes in smoking prevalence partially explained the period effect in the US (P = 0.01 and Sweden (P<0.01.There is a strong maternal age effect on abruption. While the abruption rate has plateaued since 2000 in the US, all other countries show declining rates. These findings suggest considerable variation in abruption frequencies across countries; differences in the distribution of risk factors, especially smoking, may help guide policy to reduce abruption rates.

Thyroid Cancer Incidences From Selected South America Population-Based Cancer Registries: An Age-Period-Cohort Study

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Anne Karin da Mota Borges

2017-08-01

Full Text Available Purpose: The incidence of thyroid cancer (TC has increased substantially worldwide. However, there is a lack of knowledge about age-period-cohort (APC effects on incidence rates in South American countries. This study describes the TC incidence trends and analyzes APC effects in Cali, Colombia; Costa Rica; Goiânia, Brazil; and Quito, Ecuador. Materials and Methods: Data were obtained from the Cancer Incidence in Five Continents series, and the crude and age-standardized incidence rates were calculated. Trends were assessed using the estimated annual percentage change, and APC models were estimated using Poisson regression for individuals between age 20 and 79 years. Results: An increasing trend in age-standardized incidence rates was observed among women from Goiânia (9.2%, Costa Rica (5.7%, Quito (4.0%, and Cali (3.4%, and in men from Goiânia (10.0% and Costa Rica (3.4%. The APC modeling showed that there was a period effect in all regions and for both sexes. Increasing rate ratios were observed among women over the periods. The best fit model was the APC model in women from all regions and in men from Quito, whereas the age-cohort model showed a better fit in men from Cali and Costa Rica, and the age-drift model showed a better fit among men from Goiânia. Conclusion: These findings suggest that overdiagnosis is a possible explanation for the observed increasing pattern of TC incidence. However, some environmental exposures may also have contributed to the observed increase.

Significant calendar period deviations in testicular germ cell tumors indicate that postnatal exposures are etiologically relevant.

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Speaks, Crystal; McGlynn, Katherine A; Cook, Michael B

2012-10-01

The current working model of type II testicular germ cell tumor (TGCT) pathogenesis states that carcinoma in situ arises during embryogenesis, is a necessary precursor, and always progresses to cancer. An implicit condition of this model is that only in utero exposures affect the development of TGCT in later life. In an age-period-cohort analysis, this working model contends an absence of calendar period deviations. We tested this contention using data from the SEER registries of the United States. We assessed age-period-cohort models of TGCTs, seminomas, and nonseminomas for the period 1973-2008. Analyses were restricted to whites diagnosed at ages 15-74 years. We tested whether calendar period deviations were significant in TGCT incidence trends adjusted for age deviations and cohort effects. This analysis included 32,250 TGCTs (18,475 seminomas and 13,775 nonseminomas). Seminoma incidence trends have increased with an average annual percentage change in log-linear rates (net drift) of 1.25 %, relative to just 0.14 % for nonseminoma. In more recent time periods, TGCT incidence trends have plateaued and then undergone a slight decrease. Calendar period deviations were highly statistically significant in models of TGCT (p = 1.24(-9)) and seminoma (p = 3.99(-14)), after adjustment for age deviations and cohort effects; results for nonseminoma (p = 0.02) indicated that the effects of calendar period were much more muted. Calendar period deviations play a significant role in incidence trends of TGCT, which indicates that postnatal exposures are etiologically relevant.

Spatiotemporal Scan and Age-Period-Cohort Analysis of Hepatitis C Virus in Henan, China: 2005-2012.

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Fangfang Chen

Full Text Available Studies have shown that hepatitis C virus (HCV infection increased during the past decades in China. However, little evidence is available on when, where, and who were infected with HCV. There are gaps in knowledge on the epidemiological burden and evolution of the HCV epidemic in China.Data on HCV cases were collected by the disease surveillance system from 2005 to 2012 to explore the epidemic in Henan province. Spatiotemporal scan statistics and age-period-cohort (APC model were used to examine the effects of age, period, birth cohort, and spatiotemporal clustering.177,171 HCV cases were reported in Henan province between 2005 and 2012. APC modelling showed that the HCV reported rates significantly increased in people aged > 50 years. A moderate increase in HCV reported rates was observed for females aged about 25 years. HCV reported rates increased over the study period. Infection rates were greatest among people born between 1960 and 1980. People born around 1970 had the highest relative risk of HCV infection. Women born between 1960 and 1980 had a five-fold increase in HCV infection rates compared to men, for the same birth cohort. Spatiotemporal mapping showed major clustering of cases in northern Henan, which probably evolved much earlier than other areas in the province.Spatiotemporal mapping and APC methods are useful to help delineate the evolution of the HCV epidemic. Birth cohort should be part of the criteria screening programmes for HCV in order to identify those at highest risk of infection and unaware of their status. As Henan is unique in the transmission route for HCV, these methods should be used in other high burden provinces to help identify subpopulations at risk.

Age, period and cohort effects on adult physical activity levels from 1991 to 2011 in China.

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Zang, Jiajie; Ng, Shu Wen

2016-04-20

To date no work has differentiated the effects of age, period, and cohort on physical activity (PA) among Chinese adults, while also considering biological, behavioral, economic, and environmental factors over time. We used data from the China Health and Nutrition Survey (CHNS) between 1991 and 2011 (20 years). The outcomes of interest are metabolic equivalent of task (MET) hours per week from work and domestic activities. Age, individual characteristics, household size, asset ownership, urbanization were included as covariates. Analyses for adult (≥20y) males (n = 29,343) and females (n = 31,094) was conducted to explicitly assess differences in PA due to age vs period effects, and implicitly assess differences by cohorts due to the period-specific experiences across individuals of varying ages. The mean age of the sample rose from 41.31 to 50.8 years and PA decreased from 427.75 ± 264.35 MET hours per week (MET-hr/wk) in 1991 to 245.99 ± 206.65 MET-hr/wk in 2011, with much steeper declines for women compared to men. For both genders, we found non-linear decreases in PA with age over time. Controlling for age effects, negative period effects on PA were observed in each survey year, and were substantial from 1993 to 2000 for males and from 1993 to 2011 for females. The interaction between survey year and age (P < 0.05) were observed from 2004 to 2011. Higher community urbanicity, vehicle ownership, TV and computer ownership, overweight and obese, higher education served as negative predictors. Bicycle ownership, bigger household size, non-professional jobs, being married and having more children (for women) were positive predictors of PA (P < 0.05). Furthermore, at any given age, individuals who were younger at baseline had higher mean PA compared with individuals older at baseline. This study followed a large cohort of adults over a significant portion of their lives. Strong age and secular trends were observed, resulting in an

Log-Linear Model Based Behavior Selection Method for Artificial Fish Swarm Algorithm

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Zhehuang Huang

2015-01-01

Full Text Available Artificial fish swarm algorithm (AFSA is a population based optimization technique inspired by social behavior of fishes. In past several years, AFSA has been successfully applied in many research and application areas. The behavior of fishes has a crucial impact on the performance of AFSA, such as global exploration ability and convergence speed. How to construct and select behaviors of fishes are an important task. To solve these problems, an improved artificial fish swarm algorithm based on log-linear model is proposed and implemented in this paper. There are three main works. Firstly, we proposed a new behavior selection algorithm based on log-linear model which can enhance decision making ability of behavior selection. Secondly, adaptive movement behavior based on adaptive weight is presented, which can dynamically adjust according to the diversity of fishes. Finally, some new behaviors are defined and introduced into artificial fish swarm algorithm at the first time to improve global optimization capability. The experiments on high dimensional function optimization showed that the improved algorithm has more powerful global exploration ability and reasonable convergence speed compared with the standard artificial fish swarm algorithm.

Log-linear model based behavior selection method for artificial fish swarm algorithm.

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Huang, Zhehuang; Chen, Yidong

2015-01-01

Artificial fish swarm algorithm (AFSA) is a population based optimization technique inspired by social behavior of fishes. In past several years, AFSA has been successfully applied in many research and application areas. The behavior of fishes has a crucial impact on the performance of AFSA, such as global exploration ability and convergence speed. How to construct and select behaviors of fishes are an important task. To solve these problems, an improved artificial fish swarm algorithm based on log-linear model is proposed and implemented in this paper. There are three main works. Firstly, we proposed a new behavior selection algorithm based on log-linear model which can enhance decision making ability of behavior selection. Secondly, adaptive movement behavior based on adaptive weight is presented, which can dynamically adjust according to the diversity of fishes. Finally, some new behaviors are defined and introduced into artificial fish swarm algorithm at the first time to improve global optimization capability. The experiments on high dimensional function optimization showed that the improved algorithm has more powerful global exploration ability and reasonable convergence speed compared with the standard artificial fish swarm algorithm.

Aggregation of log-linear risks

DEFF Research Database (Denmark)

Embrechts, Paul; Hashorva, Enkeleijd; Mikosch, Thomas Valentin

2014-01-01

In this paper we work in the framework of a k-dimensional vector of log-linear risks. Under weak conditions on the marginal tails and the dependence structure of a vector of positive risks, we derive the asymptotic tail behaviour of the aggregated risk {and present} an application concerning log...

Changing Attitudes Toward Euthanasia and Suicide for Terminally Ill Persons, 1977 to 2016: An Age-Period-Cohort Analysis.

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Attell, Brandon K

2017-01-01

Several longitudinal studies show that over time the American public has become more approving of euthanasia and suicide for terminally ill persons. Yet, these previous findings are limited because they derive from biased estimates of disaggregated hierarchical data. Using insights from life course sociological theory and cross-classified logistic regression models, I better account for this liberalization process by disentangling the age, period, and cohort effects that contribute to longitudinal changes in these attitudes. The results of the analysis point toward a continued liberalization of both attitudes over time, although the magnitude of change was greater for suicide compared with euthanasia. More fluctuation in the probability of supporting both measures was exhibited for the age and period effects over the cohort effects. In addition, age-based differences in supporting both measures were found between men and women and various religious affiliations.

Mortality in Danish women: age, period and cohort analysis

DEFF Research Database (Denmark)

Lindahl-Jacobsen, Rune

smokers throughout their adult life, suggesting that these smoking habits may be an important factor for their increased mortality. Study aim 3 The analysis of causes of death suggested an increased risk for deaths associated with the respiratory system and from causes traditionally associated....... Conclusion This study has shown that examination of total mortality trends in relation to age, period and cohort is a powerful exploratory tool for understanding changes in mortality and thus life expectancy. The analysis of differences in mortality trends among women in Denmark, Norway and Sweden...

An Age-Period-Cohort Analysis

OpenAIRE

Ananth, Cande V.; Keyes, Katherine M.; Hamilton, Ava; Gissler, Mika; Wu, Chunsen; Liu, Shiliang; Luque-Fernandez, Miguel Angel; Skjaerven, Rolv; Williams, Michelle A.; Tikkanen, Minna; Cnattingius, Sven

2015-01-01

Background. Although rare, placental abruption is implicated in disproportionately high rates of perinatal morbidity and mortality. Understanding geographic and temporal variations may provide insights into possible amenable factors of abruption. We examined abruption frequencies by maternal age, delivery year, and maternal birth cohorts over three decades across seven countries. Methods. Women that delivered in the US (n = 863,879; 1979–10), Canada (4 provinces, n = 5,407,463; 1982–11), ...

Educational expansion and the education gradient in health: A hierarchical age-period-cohort analysis.

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Delaruelle, Katrijn; Buffel, Veerle; Bracke, Piet

2015-11-01

Researchers have recently been investigating the temporal variation in the educational gradient in health. While there is abundant literature concerning age trajectories, theoretical knowledge about cohort differences is relatively limited. Therefore, in analogy with the life course perspective, we introduce two contrasting cohort-specific hypotheses. The diminishing health returns hypothesis predicts a decrease in educational disparities in health across cohorts. By contrast, the cohort accretion hypothesis suggests that the education-health gap will be more pronounced among younger cohorts. To shed light on this, we perform a hierarchical age-period-cohort analysis (HAPC), using data from a subsample of individuals between 25 and 85 years of age (N = 232,573) from 32 countries in the European Social Survey (six waves: 2002-2012). The analysis leads to three important conclusions. First, we observe a widening health gap between different educational levels over the life course. Second, we find that these educational differences in the age trajectories of health seem to strengthen with each successive birth cohort. However, the two age-related effects disappear when we control for employment status, household income, and family characteristics. Last, when adjusting for these mediators, we reveal evidence to support the diminishing health returns hypothesis, implying that it is primarily the direct association between education and health that decreases across cohorts. This finding raises concerns about potential barriers to education being a vehicle for empowerment and the promotion of health. Copyright © 2015 Elsevier Ltd. All rights reserved.

An Empirical Study on Stochastic Mortality Modelling under the Age-Period-Cohort Framework: The Case of Greece with Applications to Insurance Pricing

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Apostolos Bozikas

2018-04-01

Full Text Available During the last decades, life expectancy has risen significantly in the most developed countries all over the world. Greece is a case in point; consequently, higher governmental financial responsibilities occur as well as serious concerns are raised owing to population ageing. To address this issue, an efficient forecasting method is required. Therefore, the most important stochastic models were comparatively applied to Greek data for the first time. An analysis of their fitting behaviour by gender was conducted and the corresponding forecasting results were evaluated. In particular, we incorporated the Greek population data into seven stochastic mortality models under a common age-period-cohort framework. The fitting performance of each model was thoroughly evaluated based on information criteria values as well as the likelihood ratio test and their robustness to period changes was investigated. In addition, parameter risk in forecasts was assessed by employing bootstrapping techniques. For completeness, projection results for both genders were also illustrated in pricing insurance-related products.

Mortality of colorectal cancer in Taiwan, 1971-2010: temporal changes and age-period-cohort analysis.

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Su, Shih-Yung; Huang, Jing-Yang; Jian, Zhi-Hong; Ho, Chien-Chang; Lung, Chia-Chi; Liaw, Yung-Po

2012-12-01

Colorectal cancer (CRC) is the second most common cause of cancer death in developed countries among men (after lung cancer) and the third most common among women. This study thus examines the long-term trends of CRC mortality in Taiwan. CRC cases were collective between patients aged 30 years or older and younger than 85 years from the Taiwan death registries during 1971-2010. Standard descriptive techniques such as age-standardized mortality rates (ASMR), aural percent change, and age-period-cohort analyses were used. The increase of percentage change by each age group in men was higher than in women. The ASMR of CRC increased 2-fold for men and almost 1.5-fold for women during the periods 1971-1975 and 2006-2010. For age-period-cohort analysis, the estimated mortality rate increased steadily with age in both sexes, and plateaued at 175.29 per 100,000 people for men and 128.14 per 100,000 for women in the 80- to 84-year-old group. Period effects were weak in both sexes. Cohort effects were strong. Between 30 and 59 years of age, the sex ratio showed that the female CRC mortality rate was higher than that of their male counterparts. Conversely, the mortality risk of CRC in men was higher than that in women when they were between 60 and 84 years old. The current findings showed a consistent increase in mortality from CRC over the years. Changes in the patient sex ratio indicated an important etiological role of sex hormones, especially in women aged 60 years or younger.

Time trends for prostate cancer mortality in Brazil and its geographic regions: An age-period-cohort analysis.

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Braga, Sonia Faria Mendes; de Souza, Mirian Carvalho; Cherchiglia, Mariangela Leal

2017-10-01

In the 1980s, an increase in mortality rates for prostate cancer was observed in North America and developed European countries. In the 1990s, however, mortality rates decreased for these countries, an outcome related to early detection of the disease. Conversely, an upward trend in mortality rates was observed in Brazil. This study describe the trends in mortality for prostate cancer in Brazil and geographic regions (North, Northeast, South, Southeast, and Central-West) between 1980 until 2014 and analyze the influence of age, period, and cohort effects on mortality rates. This time-series study used data from the Mortality Information System (SIM) and population data from Brazilian Institute for Geography and Statistics (IBGE). The effects on mortality rates were examined using age-period-cohort (APC) models. Crude and standardized mortality rates showed an upward trend for Brazil and its regions more than 2-fold the last 30 years. Age effects showed an increased risk of death in all regions. Period effects showed a higher risk of death in the finals periods for the North and Northeast. Cohort effects showed risk of death was higher for younger than older generations in Brazil and regions, mainly Northeast (RR Adjusted =3.12, 95% CI 1.29-1.41; RR Adjusted =0.28, 95% CI 0.26-0.30, respectively). The increase in prostate cancer mortality rates in Brazil and its regions was mainly due to population aging. The differences in mortality rates and APC effects between regions are related to demographic differences and access of health services across the country. Copyright © 2017 Elsevier Ltd. All rights reserved.

Less overdiagnosis of kidney cancer? an age-period-cohort analysis of incidence trends in 16 populations worldwide.

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Znaor, Ariana; Laversanne, Mathieu; Bray, Freddie

2017-09-01

The increasing rates of kidney cancer incidence, reported in many populations globally, have been attributed both to increasing exposures to environmental risk factors, as well as increasing levels of incidental diagnosis due to widespread use of imaging. To better understand these trends, we examine long-term cancer registry data worldwide, focusing on the roles of birth cohort and calendar period, proxies for changes in risk factor prevalence and detection practice respectively. We used an augmented version of the Cancer Incidence in Five Continents series to analyze kidney cancer incidence rates 1978-2007 in 16 geographically representative populations worldwide by sex for ages 30-74, using age-period-cohort (APC) analysis. The full APC model provided the best fit to the data in most studied populations. While kidney cancer incidence rates have been increasing in successive generations born from the early twentieth century in most countries, equivalent period-specific rises were observed from the late-1970s, although these have subsequently stabilized in certain European countries (the Czech Republic, Lithuania, Finland, Spain) as well as Japan from the mid-1990s, and from the mid-2000s, in Colombia, Costa Rica and Australia. Our results indicate that the effects of both birth cohort and calendar period contribute to the international kidney cancer incidence trends. While cohort-specific increases may partly reflect the rising trends in obesity prevalence and the need for more effective primary prevention policies, the attenuations in period-specific increases (observed in 8 of the 16 populations) highlight a possible change in imaging practices that could lead to mitigation of overdiagnosis and overtreatment. © 2017 UICC.

Linear spline multilevel models for summarising childhood growth trajectories: A guide to their application using examples from five birth cohorts.

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Howe, Laura D; Tilling, Kate; Matijasevich, Alicia; Petherick, Emily S; Santos, Ana Cristina; Fairley, Lesley; Wright, John; Santos, Iná S; Barros, Aluísio Jd; Martin, Richard M; Kramer, Michael S; Bogdanovich, Natalia; Matush, Lidia; Barros, Henrique; Lawlor, Debbie A

2016-10-01

Childhood growth is of interest in medical research concerned with determinants and consequences of variation from healthy growth and development. Linear spline multilevel modelling is a useful approach for deriving individual summary measures of growth, which overcomes several data issues (co-linearity of repeat measures, the requirement for all individuals to be measured at the same ages and bias due to missing data). Here, we outline the application of this methodology to model individual trajectories of length/height and weight, drawing on examples from five cohorts from different generations and different geographical regions with varying levels of economic development. We describe the unique features of the data within each cohort that have implications for the application of linear spline multilevel models, for example, differences in the density and inter-individual variation in measurement occasions, and multiple sources of measurement with varying measurement error. After providing example Stata syntax and a suggested workflow for the implementation of linear spline multilevel models, we conclude with a discussion of the advantages and disadvantages of the linear spline approach compared with other growth modelling methods such as fractional polynomials, more complex spline functions and other non-linear models. © The Author(s) 2013.

TESTING THE ASSUMPTIONS AND INTERPRETING THE RESULTS OF THE RASCH MODEL USING LOG-LINEAR PROCEDURES IN SPSS

NARCIS (Netherlands)

TENVERGERT, E; GILLESPIE, M; KINGMA, J

This paper shows how to use the log-linear subroutine of SPSS to fit the Rasch model. It also shows how to fit less restrictive models obtained by relaxing specific assumptions of the Rasch model. Conditional maximum likelihood estimation was achieved by including dummy variables for the total

Trend analysis and modelling of gender-specific age, period and birth cohort effects on alcohol abstention and consumption level for drinkers in Great Britain using the General Lifestyle Survey 1984-2009.

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Meng, Yang; Holmes, John; Hill-McManus, Daniel; Brennan, Alan; Meier, Petra Sylvia

2014-02-01

British alcohol consumption and abstinence rates have increased substantially in the last 3 decades. This study aims to disentangle age, period and birth cohort effects to improve our understanding of these trends and suggest groups for targeted interventions to reduce resultant harms. Age, period, cohort analysis of repeated cross-sectional surveys using separate logistic and negative binomial models for each gender. Great Britain 1984-2009. Annual nationally representative samples of approximately 20 000 adults (16+) within 13 000 households. Age (eight groups: 16-17 to 75+ years), period (six groups: 1980-84 to 2005-09) and birth cohorts (19 groups: 1900-04 to 1990-94). Outcome measures were abstinence and average weekly alcohol consumption. Controls were income, education, ethnicity and country. After accounting for period and cohort trends, 18-24-year-olds have the highest consumption levels (incident rate ratio = 1.18-1.15) and lower abstention rates (odds ratio = 0.67-0.87). Consumption generally decreases and abstention rates increase in later life. Until recently, successive birth cohorts' consumption levels were also increasing. However, for those born post-1985, abstention rates are increasing and male consumption is falling relative to preceding cohorts. In contrast, female drinking behaviours have polarized over the study period, with increasing abstention rates accompanying increases in drinkers' consumption levels. Rising female consumption of alcohol and progression of higher-consuming birth cohorts through the life course are key drivers of increased per capita alcohol consumption in the United Kingdom. Recent declines in alcohol consumption appear to be attributable to reduced consumption and increased abstinence rates among the most recent birth cohorts, especially males, and general increased rates of abstention across the study period. © 2013 Society for the Study of Addiction.

Age, Period, and Cohort Effects in Psychological Distress in the United States and Canada

Science.gov (United States)

Keyes, Katherine M.; Nicholson, Ryan; Kinley, Jolene; Raposo, Sarah; Stein, Murray B.; Goldner, Elliot M.; Sareen, Jitender

2014-01-01

Although treatment utilization for depression and anxiety symptoms has increased substantially in the United States and elsewhere, it remains unclear whether the underlying population distribution of psychological distress is changing over time. We estimated age, period, and cohort effects using data from 2 countries over more than 20 years, including National Health Interview Surveys from 1997 to 2010 (n = 447,058) and Canadian Community Health Surveys from 2000 to 2007 (n = 125,306). Psychological distress was measured with the Kessler Psychological Distress Scale. By period, both countries showed the highest levels of psychological distress in 2001 and the lowest levels in 2007. By age, psychological distress was highest in adolescence and during the late 40s and early 50s. By cohort, Canadian Community Health Survey results indicated a decreasing cohort effect among those born in 1922–1925 through 1935–1939 (β = −0.36, 95% confidence interval: −0.45, −0.27) and then a continuously increasing cohort effect during the remainder of the 20th century through 1989–1992 (β = 0.49, 95% confidence interval: 0.38, 0.61). The National Health Interview Survey data captured earlier-born cohorts and indicated an increased cohort effect for the earliest born (for 1912–1914, β = 0.44, 95% confidence interval: 0.26, 0.61). In sum, individuals in the oldest and more recently born birth cohorts have higher mean psychological distress symptoms compared with those born in midcentury, underscoring the importance of a broad, population-level lens for conceptualizing mental health. PMID:24692432

Periodicity in Age-Resolved Populations

Science.gov (United States)

Esipov, Sergei

We discuss the interplay between the non-linear diffusion and age-resolved population dynamics. Depending on the age properties of collective migration the system may exhibit continuous joint expansion of all ages or continuous expansion with age segregation. Between these two obvious limiting regimes there is an interesting window of periodic expansion, which has been previously used by us in modeling bacterial colonies of Proteus mirabilis. In order to test whether the age-dependent collective migration leads to periodicity in other systems we performed a Fourier analysis of historical data on ethnic expansions and found multiple co-existing periods of activity.

Risk evaluations of aging phenomena: The linear aging reliability model and its extensions

International Nuclear Information System (INIS)

Vesely, W.E.; Wolford, A.J.

1988-01-01

A model for component failure rates due to aging mechanisms is developed from basic phenomenological considerations. In the treatment, the occurrences of deterioration are modeled as following a Poisson process. The severity of damage is allowed to have any distribution, however the damage is assumed to accumulate independently. Finally, the failure rate is modeled as being proportional to the accumulated damage. Using this treatment, the linear aging failure rate model is obtained. The applicability of the linear aging model to various mechanisms is discussed. Extensions of the model to cover nonlinear and dependent aging phenomena are also described. The implementability of the linear aging model is demonstrated by applying it to the aging data collected in the U.S. NRC Nuclear Plant Aging Research (NPAR) Program. (orig./HP)

Global patterns and trends in stomach cancer incidence: Age, period and birth cohort analysis.

Science.gov (United States)

Luo, Ganfeng; Zhang, Yanting; Guo, Pi; Wang, Li; Huang, Yuanwei; Li, Ke

2017-10-01

The cases of stomach cancer (SC) incidence are increasing per year and the SC burden has remained very high in some countries. We aimed to evaluate the global geographical variation in SC incidence and temporal trends from 1978 to 2007, with an emphasis on the effect of birth cohort. Joinpoint regression and age-period-cohort model were applied. From 2003 to 2007, male rate were 1.5- to 3-fold higher than female in all countries. Rates were highest in Eastern Asian and South American countries. Except for Uganda, all countries showed favorable trends. Pronounced cohort-specific increases in risk for recent birth cohorts were seen in Brazil, Colombia, Iceland, New Zealand, Norway, Uganda and US white people for males and in Australia, Brazil, Colombia, Costa Rica, Czech Republic, Ecuador, Iceland, India, Malta, New Zealand, Norway, Switzerland, United Kingdom, Uganda, US black and white people for females. The cohort-specific ratio for male significantly decreased in Japan, Malta and Spain for cohorts born since 1950 and in Austria, China, Croatia, Ecuador, Russia, Switzerland and Thailand for cohorts born since 1960 and for female in Japan for cohorts born since 1950 and in Canada, China, Croatia, Latvia, Russia and Thailand for cohorts born since 1960. Disparities in incidence and carcinogenic risk persist worldwide. The favorable trends may be due to changes in environmental exposure and lifestyle, including decreased Helicobacter pylori prevalence, increased intake of fresh fruits and vegetables, the availability of refrigeration and decreased intake of salted and preserved food and smoking prevalence. © 2017 UICC.

Risk evaluations of aging phenomena: the linear aging reliability model and its extensions

International Nuclear Information System (INIS)

Vesely, W.E.

1987-01-01

A model for component failure rates due to aging mechanisms has been developed from basic phenomenological considerations. In the treatment, the occurrences of deterioration are modeled as following a Poisson process. The severity of damage is allowed to have any distribution, however the damage is assumed to accumulate independently. Finally, the failure rate is modeled as being proportional to the accumulated damage. Using this treatment, the linear aging failure rate model is obtained. The applicability of the linear aging model to various mechanisms is discussed. The model can be extended to cover nonlinear and dependent aging phenomena. The implementability of the linear aging model is demonstrated by applying it to the aging data collected in NRC's Nuclear Plant Aging Research (NPAR) Program. The applications show that aging as observed in collected data have significant effects on the component failure probability and component reliability when aging is not effectively detected and controlled by testing and maintenance

Risk evaluations of aging phenomena: The linear aging reliability model and its extensions

International Nuclear Information System (INIS)

Vesely, W.E.

1986-01-01

A model for component failure rates due to aging mechanisms has been developed from basic phenomenological considerations. In the treatment, the occurrences of deterioration are modeled as following a Poisson process. The severity of damage is allowed to have any distribution, however the damage is assumed to accumulate independently. Finally, the failure rate is modeled as being proportional to the accumulated damage. Using this treatment, the linear aging failure rate model is obtained. The applicability of the linear aging model to various mechanisms is discussed. The model can be extended to cover nonlinear and dependent aging phenomena. The implementability of the linear aging model is demonstrated by applying it of the aging data collected in NRC's Nuclear Plant Aging Research (NPAR) Program. The applications show that aging as observed in collected data have significant effects on the component failure probability and component reliability when aging is not effectively detected and controlled by testing and maintenance

Trends in esophageal cancer mortality in China during 1987-2009: age, period and birth cohort analyzes.

Science.gov (United States)

Guo, Pi; Li, Ke

2012-04-01

Esophageal cancer is one of the most commonly diagnosed malignant tumors in China. The aim of this study was to provide the representative and comprehensive informations about the long-term mortality trends of this disease in China between 1987 and 2009, using joinpoint regression and generalized additive models (GAMs). Age-standardized mortality rates (ASMR), overall and truncated (35-64 years), were calculated using the direct calculation method, and joinpoint regression was performed to obtain the estimated annual percentage changes (EAPC). GAMs were fitted to study the effects of age, period and birth cohort on mortality trends. ASMR exhibited an overall remarked decline for rural females (EAPC=-2.3 95%CI: -3.3, -1.2), urban males (EAPC=-1.8 95%CI: -2.6, -1.0) and urban females (EAPC=-3.7 95%CI: -4.9, -2.4), but a small drop observed was not statistically significant for rural males (EAPC=-0.9 95%CI: -2.0, 0.3). The declines in ASMR were more noticeable for urban residents in recent years. Among all the residents, age effect showed an progressively increasing trend, whereas cohort effect declined steadily after the year corresponding to the maximum risk value. Period effect seemed to remain substantially unchanged throughout the years. Although variations in mortality rates were observed according to sex and area, the overall decreasing trends in esophageal cancer mortality were found in most Chinese people, aside from rural males. The findings could correspond to the changes in age- and cohort-related factors in the population. Further study is required to understand these potential factors. Copyright © 2011 Elsevier Ltd. All rights reserved.

Age-specific mortality trends in France and Italy since 1900: period and cohort effects.

Science.gov (United States)

Caselli, G; Vallin, J; Vaupel, J W; Yashin, A

1987-11-01

The age/sex-specific mortality trends of France and Italy were studied over the 1899-1979 period in as much detail as possible in an effort to distinguish between cohort effects and those related to period changes. Complete series of mortality data by individual years of age and calendar years were available from 1869 to 1979 for Italy and from 1899 to 1982 for France. For both countries, these data include the military and civil deaths not registered in vital statistics during the war periods. They cover each national territory as defined by its present boundaries. The graphical representation method of mortality surfaces, elaborated by Vaupel, Gambill, and Yashin (1985), was adopted. The age/sex-specific mortality patterns of France and Italy have not followed the same trends, and the differences observed today are not those of 100 years ago. The mean death probabilities for the 1975-79 period were used to illustrate the age-specific patterns of mortality. Although infant mortality was higher in Italy than in France, the death probabilities at ages 1-15 for both sexes were roughly the same for both countries. At ages 15-23, they were much higher in France than in Italy, and they remained considerably higher in France up to age 55. From then on, the sexes differ: for males, the 2 countries showed similar patterns, whereas for females the probabilities were noticeably higher for France. The situation was very different for both countries at the beginning of the century. For both sexes, higher mortality was observed in Italy not only during infancy but throughout childhood and the adolescent years up to age 15. The 2 countries showed similar patterns from 15-25. Above age 25, the 2 countries had similar patterns for females, whereas male mortality was higher in France right up to the old age groups. Such differences in the age-specific mortality trends depend in part on a different development of health and social conditions but also may be due to factors concerning

Cohort Differences in Cognitive Aging in the Longitudinal Aging Study Amsterdam.

Science.gov (United States)

Brailean, Anamaria; Huisman, Martijn; Prince, Martin; Prina, A Matthew; Deeg, Dorly J H; Comijs, Hannie

2016-09-30

This study aims to examine cohort differences in cognitive performance and rates of change in episodic memory, processing speed, inductive reasoning, and general cognitive performance and to investigate whether these cohort effects may be accounted for by education attainment. The first cohort (N = 705) was born between 1920 and 1930, whereas the second cohort (N = 646) was born between 1931 and 1941. Both birth cohorts were aged 65 to 75 years at baseline and were followed up 3 and 6 years later. Data were analyzed using linear mixed models. The later born cohort had better general cognitive performance, inductive reasoning, and processing speed at baseline, but cohort differences in inductive reasoning and general cognitive performance disappeared after adjusting for education. The later born cohort showed steeper decline in processing speed. Memory decline was steeper in the earlier born cohort but only from Time 1 to Time 3 when the same memory test was administered. Education did not account for cohort differences in cognitive decline. The later born cohort showed better initial performance in certain cognitive abilities, but no better preservation of cognitive abilities overtime compared with the earlier born cohort. These findings carry implications for healthy cognitive aging. © The Author 2016. Published by Oxford University Press on behalf of The Gerontological Society of America.

Model linear absolute and relative risk estimates for cancer induced by ionizing radiation in Mexican cohort of occupationally exposed

International Nuclear Information System (INIS)

Alvarez, R.J.T.; Trovar, M.V.M; González, J.F.

2015-01-01

From the rate of natural mortality m s cancer (t) for every 100 thousand habitants, modeled by a fourth-degree polynomial function of the age data of the Mexican population (2008), and assuming: a) a relationship 1: 5 of cancer induced radiation respect to presented spontaneously, b) a size of initial cohort No = 100 k SOPs, c) a speed of H E = (2 ± 1) mSv / received by the SOPs from 18 to 65 years, d) a latency of 8 years for cancer induction after irradiation, e) a time tracking cohort to 75 years, f) and taking the coefficients absolute and relative risk BEIRs induction of cancer models II and VII (excluding leukemia); It determined: BEIR II for a total of 125 and 400 deaths from cancer for absolute and relative linear models respectively. For BEIR VII has a number of fatal cases of 345 and 927 deaths respectively for absolute and relative linear model cancer. [es

Changing BMI scores among Canadian Indigenous and non-Indigenous children, youth, and young adults: Untangling age, period, and cohort effects

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Piotr Wilk

2017-04-01

Full Text Available The objective of this study was to examine age, period and cohort effects on BMI among Indigenous and non-Indigenous populations, using repeated cross-sectional survey data from the CCHS (2001 to 2014. Cross-classified random-effect two-level models were used to estimate fixed effects for age and its quadratic term (Level 1, and also to estimate random effects for time periods and birth cohorts (Level 2, while controlling for the effects of Level 1 control variables: sex, model of interview and response by proxy. Overall, the results support the hypothesis that age and period effects are primarily responsible for the current obesity epidemic. L’objectif de cette étude était d’examiner les effets de l’âge, de la période et de la cohorte sur l’IMC chez les populations autochtones et non autochtones, en utilisant des données d’enquêtes transversales répétées de l’ESCC (2001 à 2014. On a utilisé des modèles à deux niveaux à effets aléatoires croisés pour estimer les effets fixes pour l’âge et son terme quadratique (niveau 1, et également estimer les effets aléatoires pour les périodes et les cohortes de naissance (niveau 2, tout en contrôlant les effets du niveau 1 Variables de contrôle: sexe, modèle d’interview et réponse par procuration. Dans l’ensemble, les résultats confirment l’hypothèse selon laquelle les effets de l’âge et de la période sont les principaux responsables de l’épidémie actuelle d’obésité.

Period Effects, Cohort Effects, and the Narrowing Gender Wage Gap

OpenAIRE

Campbell, Colin; Pearlman, Jessica

2013-01-01

Despite the abundance of sociological research on the gender wage gap, questions remain. In particular, the role of cohorts is under investigated. Using data from the Current Population Survey, we use Age-Period-Cohort analysis to uniquely estimate age, period, and cohort effects on the gender wage gap. The narrowing of the gender wage gap that occurred between 1975 and 2009 is largely due to cohort effects. Since the mid-1990s, the gender wage gap has continued to close absent of period effe...

Log-binomial models: exploring failed convergence.

Science.gov (United States)

Williamson, Tyler; Eliasziw, Misha; Fick, Gordon Hilton

2013-12-13

Relative risk is a summary metric that is commonly used in epidemiological investigations. Increasingly, epidemiologists are using log-binomial models to study the impact of a set of predictor variables on a single binary outcome, as they naturally offer relative risks. However, standard statistical software may report failed convergence when attempting to fit log-binomial models in certain settings. The methods that have been proposed in the literature for dealing with failed convergence use approximate solutions to avoid the issue. This research looks directly at the log-likelihood function for the simplest log-binomial model where failed convergence has been observed, a model with a single linear predictor with three levels. The possible causes of failed convergence are explored and potential solutions are presented for some cases. Among the principal causes is a failure of the fitting algorithm to converge despite the log-likelihood function having a single finite maximum. Despite these limitations, log-binomial models are a viable option for epidemiologists wishing to describe the relationship between a set of predictors and a binary outcome where relative risk is the desired summary measure. Epidemiologists are encouraged to continue to use log-binomial models and advocate for improvements to the fitting algorithms to promote the widespread use of log-binomial models.

The log-linear return approximation, bubbles, and predictability

DEFF Research Database (Denmark)

Engsted, Tom; Pedersen, Thomas Quistgaard; Tanggaard, Carsten

We study in detail the log-linear return approximation introduced by Campbell and Shiller (1988a). First, we derive an upper bound for the mean approximation error, given stationarity of the log dividendprice ratio. Next, we simulate various rational bubbles which have explosive conditional expec...

Time trends of esophageal and gastric cancer mortality in China, 1991?2009: an age-period-cohort analysis

OpenAIRE

Li, Mengmeng; Wan, Xia; Wang, Yanhong; Sun, Yuanyuan; Yang, Gonghuan; Wang, Li

2017-01-01

Esophageal and gastric cancers share some risk factors. This study aimed to compare the long-term trends in mortality rates of esophageal and gastric cancers in China to provide evidence for cancer prevention and control. Mortality data were derived from 103 continuous points of the Disease Surveillance Points system during 1991?2009, stratified by gender and urban-rural locations. Age-period-cohort models were used to disentangle the time trends of esophageal and gastric cancer mortality. Th...

The Log-Linear Return Approximation, Bubbles, and Predictability

DEFF Research Database (Denmark)

Engsted, Tom; Pedersen, Thomas Quistgaard; Tanggaard, Carsten

2012-01-01

We study in detail the log-linear return approximation introduced by Campbell and Shiller (1988a). First, we derive an upper bound for the mean approximation error, given stationarity of the log dividend-price ratio. Next, we simulate various rational bubbles which have explosive conditional expe...

Análisis edad-periodo-cohorte de la mortalidad por accidentes de tráfico en España Age-period-cohort analysis of traffic accident mortality in Spain

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Carmen Saiz-Sánchez

1999-05-01

Full Text Available OBJETIVO. Estudiar la evolución de la mortalidad por accidentes de tráfico en España y su posible aplicación a un modelo edad-periodo-cohorte, así como el efecto que pueden tener algunas medidas de seguridad vial seleccionadas. MATERIAL Y MÉTODOS. Se obtuvieron las tasas de mortalidad por accidentes de tráfico y las tasas en intervalos quinquenales de edad para cada sexo, lo que permite su estudio como tasas específicas de edad por cohortes de nacimiento. Para determinar la asociación entre las medidas de seguridad vial seleccionadas y la mortalidad se han construido modelos de regresión de Poisson. RESULTADOS. Se observaron dos ondas evolutivas en la mortalidad por accidentes de tráfico. Respecto a la edad, no podemos hablar de un efecto claro; tampoco se encontró un efecto cohorte ni para varones ni para mujeres. En relación con las medidas de seguridad vial, se discutió la consistencia que guardaban los modelos seleccionados con los resultados gráficos, y se obtuvo que el uso obligatorio del casco y de las luces de cruce en motocicletas se ha asociado significativamente a la reducción de la mortalidad (RR 0.73, pOBJECTIVE. To study the evolution of traffic accidents mortality in Spain and its possible application to an age-period-cohort analysis, as well as the effect of selected road safety measures. MATERIAL AND METHODS. Road accidents rates of mortality were obtained, and five-year interval age rates for each sex, which allows the study of specific rates of age by birth cohorts. To determine the association between the selected road safety measures and mortality, Poisson regression models were adjusted. RESULTS. Two waves emerge in the evolution of traffic accidents. There was no clear effect with respect to age, nor was there a cohort effect for men or women. As to the road safety measures, we discuss the consistency between the selected models and graphic results. The compulsory use of helmet and of crossing lights is

Advanced maternal age and adverse pregnancy outcome: evidence from a large contemporary cohort.

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Louise C Kenny

Full Text Available BACKGROUND: Recent decades have witnessed an increase in mean maternal age at childbirth in most high-resourced countries. Advanced maternal age has been associated with several adverse maternal and perinatal outcomes. Although there are many studies on this topic, data from large contemporary population-based cohorts that controls for demographic variables known to influence perinatal outcomes is limited. METHODS: We performed a population-based cohort study using data on all singleton births in 2004-2008 from the North Western Perinatal Survey based at The University of Manchester, UK. We compared pregnancy outcomes in women aged 30-34, 35-39 and ≥40 years with women aged 20-29 years using log-linear binomial regression. Models were adjusted for parity, ethnicity, social deprivation score and body mass index. RESULTS: The final study cohort consisted of 215,344 births; 122,307 mothers (54.19% were aged 20-29 years, 62,371(27.63% were aged 30-34 years, 33,966(15.05% were aged 35-39 years and 7,066(3.13% were aged ≥40 years. Women aged 40+ at delivery were at increased risk of stillbirth (RR = 1.83, [95% CI 1.37-2.43], pre-term (RR = 1.25, [95% CI: 1.14-1.36] and very pre-term birth (RR = 1.29, [95% CI:1.08-1.55], Macrosomia (RR = 1.31, [95% CI: 1.12-1.54], extremely large for gestational age (RR = 1.40, [95% CI: 1.25-1.58] and Caesarean delivery (RR = 1.83, [95% CI: 1.77-1.90]. CONCLUSIONS: Advanced maternal age is associated with a range of adverse pregnancy outcomes. These risks are independent of parity and remain after adjusting for the ameliorating effects of higher socioeconomic status. The data from this large contemporary cohort will be of interest to healthcare providers and women and will facilitate evidence based counselling of older expectant mothers.

Period Effects, Cohort Effects, and the Narrowing Gender Wage Gap

Science.gov (United States)

Campbell, Colin; Pearlman, Jessica

2015-01-01

Despite the abundance of sociological research on the gender wage gap, questions remain. In particular, the role of cohorts is under investigated. Using data from the Current Population Survey, we use Age-Period-Cohort analysis to uniquely estimate age, period, and cohort effects on the gender wage gap. The narrowing of the gender wage gap that occurred between 1975 and 2009 is largely due to cohort effects. Since the mid-1990s, the gender wage gap has continued to close absent of period effects. While gains in female wages contributed to declines in the gender wage gap for cohorts born before 1950, for later cohorts the narrowing of the gender wage gap is primarily a result of declines in male wages. PMID:24090861

A probit- log- skew-normal mixture model for repeated measures data with excess zeros, with application to a cohort study of paediatric respiratory symptoms

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Johnston Neil W

2010-06-01

Full Text Available Abstract Background A zero-inflated continuous outcome is characterized by occurrence of "excess" zeros that more than a single distribution can explain, with the positive observations forming a skewed distribution. Mixture models are employed for regression analysis of zero-inflated data. Moreover, for repeated measures zero-inflated data the clustering structure should also be modeled for an adequate analysis. Methods Diary of Asthma and Viral Infections Study (DAVIS was a one year (2004 cohort study conducted at McMaster University to monitor viral infection and respiratory symptoms in children aged 5-11 years with and without asthma. Respiratory symptoms were recorded daily using either an Internet or paper-based diary. Changes in symptoms were assessed by study staff and led to collection of nasal fluid specimens for virological testing. The study objectives included investigating the response of respiratory symptoms to respiratory viral infection in children with and without asthma over a one year period. Due to sparse data daily respiratory symptom scores were aggregated into weekly average scores. More than 70% of the weekly average scores were zero, with the positive scores forming a skewed distribution. We propose a random effects probit/log-skew-normal mixture model to analyze the DAVIS data. The model parameters were estimated using a maximum marginal likelihood approach. A simulation study was conducted to assess the performance of the proposed mixture model if the underlying distribution of the positive response is different from log-skew normal. Results Viral infection status was highly significant in both probit and log-skew normal model components respectively. The probability of being symptom free was much lower for the week a child was viral positive relative to the week she/he was viral negative. The severity of the symptoms was also greater for the week a child was viral positive. The probability of being symptom free was

On the relationship between period and cohort mortality

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John R. Wilmoth

2005-11-01

Full Text Available In this paper I explore the formal relationship between period and cohort mortality, focusing on a comparison of measures of mean lifespan. I consider not only the usual measures (life expectancy at birth for time periods and birth cohorts but also some alternative measures that have been proposed recently. I examine (and reject the claim made by Bongaarts and Feeney that the level of period is distorted, or biased, due to changes in the timing of mortality. I show that their proposed alternative measure, called "tempo-adjusted" life expectancy, is exactly equivalent in its generalized form to a measure proposed by both Brouard and Guillot, the cross-sectional average length of life (or CAL, which substitutes cohort survival probabilities for their period counterparts in the calculation of mean lifespan. I conclude that this measure does not in any sense correct for a distortion in period life expectancy at birth, but rather offers an alternative measure of mean lifespan that is approximately equal to two analytically interesting quantities: 1 the mean age at death in a given year for a hypothetical population subject to observed historical mortality conditions but with a constant annual number of births; and 2 the mean age at death, , for a cohort born years ago. However, I also observe that the trend in period does indeed offer a biased depiction of the pace of change in mean lifespan from cohort to cohort. Holding other factors constant, an historical increase in life expectancy at birth is somewhat faster when viewed from the perspective of cohorts (i.e., year of birth than from the perspective of periods (i.e., year of death.

Period effects, cohort effects, and the narrowing gender wage gap.

Science.gov (United States)

Campbell, Colin; Pearlman, Jessica

2013-11-01

Despite the abundance of sociological research on the gender wage gap, questions remain. In particular, the role of cohorts is under investigated. Using data from the Current Population Survey, we use age-period-cohort analysis to uniquely estimate age, period, and cohort effects on the gender wage gap. The narrowing of the gender wage gap that occurred between 1975 and 2009 is largely due to cohort effects. Since the mid-1990s, the gender wage gap has continued to close absent of period effects. While gains in female wages contributed to declines in the gender wage gap for cohorts born before 1950, for later cohorts the narrowing of the gender wage gap is primarily a result of declines in male wages. Copyright © 2013 Elsevier Inc. All rights reserved.

Colorectal cancer mortality trends in Serbia during 1991-2010: an age-period-cohort analysis and a joinpoint regression analysis.

Science.gov (United States)

Ilic, Milena; Ilic, Irena

2016-06-22

For both men and women worldwide, colorectal cancer is among the leading causes of cancer-related death. This study aimed to assess the mortality trends of colorectal cancer in Serbia between 1991 and 2010, prior to the introduction of population-based screening. Joinpoint regression analysis was used to estimate average annual percent change (AAPC) with the corresponding 95% confidence interval (CI). Furthermore, age-period-cohort analysis was performed to examine the effects of birth cohort and calendar period on the observed temporal trends. We observed a significantly increased trend in colorectal cancer mortality in Serbia during the study period (AAPC = 1.6%, 95% CI 1.3%-1.8%). Colorectal cancer showed an increased mortality trend in both men (AAPC = 2.0%, 95% CI 1.7%-2.2%) and women (AAPC = 1.0%, 95% CI 0.6%-1.4%). The temporal trend of colorectal cancer mortality was significantly affected by birth cohort (P < 0.05), whereas the study period did not significantly affect the trend (P = 0.072). Colorectal cancer mortality increased for the first several birth cohorts in Serbia (from 1916 to 1955), followed by downward flexion for people born after the 1960s. According to comparability test, overall mortality trends for colon cancer and rectal and anal cancer were not parallel (the final selected model rejected parallelism, P < 0.05). We found that colorectal cancer mortality in Serbia increased considerably over the past two decades. Mortality increased particularly in men, but the trends were different according to age group and subsite. In Serbia, interventions to reduce colorectal cancer burden, especially the implementation of a national screening program, as well as treatment improvements and measures to encourage the adoption of a healthy lifestyle, are needed.

Standardizing effect size from linear regression models with log-transformed variables for meta-analysis.

Science.gov (United States)

Rodríguez-Barranco, Miguel; Tobías, Aurelio; Redondo, Daniel; Molina-Portillo, Elena; Sánchez, María José

2017-03-17

Meta-analysis is very useful to summarize the effect of a treatment or a risk factor for a given disease. Often studies report results based on log-transformed variables in order to achieve the principal assumptions of a linear regression model. If this is the case for some, but not all studies, the effects need to be homogenized. We derived a set of formulae to transform absolute changes into relative ones, and vice versa, to allow including all results in a meta-analysis. We applied our procedure to all possible combinations of log-transformed independent or dependent variables. We also evaluated it in a simulation based on two variables either normally or asymmetrically distributed. In all the scenarios, and based on different change criteria, the effect size estimated by the derived set of formulae was equivalent to the real effect size. To avoid biased estimates of the effect, this procedure should be used with caution in the case of independent variables with asymmetric distributions that significantly differ from the normal distribution. We illustrate an application of this procedure by an application to a meta-analysis on the potential effects on neurodevelopment in children exposed to arsenic and manganese. The procedure proposed has been shown to be valid and capable of expressing the effect size of a linear regression model based on different change criteria in the variables. Homogenizing the results from different studies beforehand allows them to be combined in a meta-analysis, independently of whether the transformations had been performed on the dependent and/or independent variables.

Log-periodic dipole antenna with low cross-polarization

DEFF Research Database (Denmark)

Pivnenko, Sergey

2006-01-01

In this work, log-periodic antennas with improved cross-polarization level were studied. It was found that some modifications of the traditional design lead to an essential improvement of the co-to-cross polarization ratio up to 40 dB. An improved design of a log-periodic dipole antenna with low...

Structural equation and log-linear modeling: a comparison of methods in the analysis of a study on caregivers' health

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Rosenbaum Peter L

2006-10-01

Full Text Available Abstract Background In this paper we compare the results in an analysis of determinants of caregivers' health derived from two approaches, a structural equation model and a log-linear model, using the same data set. Methods The data were collected from a cross-sectional population-based sample of 468 families in Ontario, Canada who had a child with cerebral palsy (CP. The self-completed questionnaires and the home-based interviews used in this study included scales reflecting socio-economic status, child and caregiver characteristics, and the physical and psychological well-being of the caregivers. Both analytic models were used to evaluate the relationships between child behaviour, caregiving demands, coping factors, and the well-being of primary caregivers of children with CP. Results The results were compared, together with an assessment of the positive and negative aspects of each approach, including their practical and conceptual implications. Conclusion No important differences were found in the substantive conclusions of the two analyses. The broad confirmation of the Structural Equation Modeling (SEM results by the Log-linear Modeling (LLM provided some reassurance that the SEM had been adequately specified, and that it broadly fitted the data.

Age-period-cohort projections of ischaemic heart disease mortality by socio-economic position in a rapidly transitioning Chinese population.

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Irene O L Wong

Full Text Available BACKGROUND: With economic development and population aging, ischaemic heart disease (IHD is becoming a leading cause of mortality with widening inequalities in China. To forewarn the trends in China we projected IHD trends in the most economically developed part of China, i.e., Hong Kong. METHODS: Based on sex-specific IHD mortality rates from 1976 to 2005, we projected mortality rates by neighborhood-level socio-economic position (i.e., low- or high-income groups to 2020 in Hong Kong using Poisson age-period-cohort models with autoregressive priors. RESULTS: In the low-income group, age-standardized IHD mortality rates among women declined from 33.3 deaths in 1976-1980 to 19.7 per 100,000 in 2016-2020 (from 55.5 deaths to 34.2 per 100,000 among men. The rates in the high-income group were initially higher in both sexes, particularly among men, but this had reversed by the end of the study periods. The rates declined faster for the high-income group than for the low-income group in both sexes. The rates were projected to decline faster in the high-income group, such that by the end of the projection period the high-income group would have lower IHD mortality rates, particularly for women. Birth cohort effects varied with sex, with a marked upturn in IHD mortality around 1945, i.e., for the first generation of men to grow up in a more economically developed environment. There was no such upturn in women. Birth cohort effects were the main drivers of change in IHD mortality rates. CONCLUSION: IHD mortality rates are declining in Hong Kong and are projected to continue to do so, even taking into account greater vulnerability for the first generation of men born into a more developed environment. At the same time social disparities in IHD have reversed and are widening, partly as a result of a cohort effect, with corresponding implications for prevention.

Exposure-lag-response in Longitudinal Studies: Application of Distributed Lag Non-linear Models in an Occupational Cohort.

Science.gov (United States)

Neophytou, Andreas M; Picciotto, Sally; Brown, Daniel M; Gallagher, Lisa E; Checkoway, Harvey; Eisen, Ellen A; Costello, Sadie

2018-02-13

Prolonged exposures can have complex relationships with health outcomes, as timing, duration, and intensity of exposure are all potentially relevant. Summary measures such as cumulative exposure or average intensity of exposure may not fully capture these relationships. We applied penalized and unpenalized distributed lag non-linear models (DLNMs) with flexible exposure-response and lag-response functions in order to examine the association between crystalline silica exposure and mortality from lung cancer and non-malignant respiratory disease in a cohort study of 2,342 California diatomaceous earth workers, followed 1942-2011. We also assessed associations using simple measures of cumulative exposure assuming linear exposure-response and constant lag-response. Measures of association from DLNMs were generally higher than from simpler models. Rate ratios from penalized DLNMs corresponding to average daily exposures of 0.4 mg/m3 during lag years 31-50 prior to the age of observed cases were 1.47 (95% confidence interval (CI) 0.92, 2.35) for lung cancer and 1.80 (95% CI: 1.14, 2.85) for non-malignant respiratory disease. Rate ratios from the simpler models for the same exposure scenario were 1.15 (95% CI: 0.89-1.48) and 1.23 (95% CI: 1.03-1.46) respectively. Longitudinal cohort studies of prolonged exposures and chronic health outcomes should explore methods allowing for flexibility and non-linearities in the exposure-lag-response. © The Author(s) 2018. Published by Oxford University Press on behalf of the Johns Hopkins Bloomberg School of Public Health.

Recent hip fracture trends in Sweden and Denmark with age-period-cohort effects

DEFF Research Database (Denmark)

Rosengren, B E; Björk, J; Cooper, C

2017-01-01

This study used nationwide hip fracture data from Denmark and Sweden during 1987-2010 to examine effects of (birth) cohort and period. We found that time trends, cohort, and period effects were different in the two countries. Results also indicated that hip fracture rates may increase in the not ...

Breast cancer mortality in mexico: an age-period-cohort analysis Mortalidad por cáncer de mama en méxico: un análisis de edad-periodo-cohorte

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Francisco Franco-Marina

2009-01-01

Full Text Available OBJECTIVE: To assess the age, period and cohort effects on breast cancer (BC mortality in Mexico. MATERIAL AND METHODS: Age, period and cohort curvature trends for BC mortality were estimated through the Poisson Regression model proposed by Holford. RESULTS: Nationally, BC death rates have leveled off since 1995 in most age groups. BC mortality trends are mainly determined by birth cohort and age effects in Mexico. Women born between 1940 and 1955 show the highest rate of increase in BC mortality. Women born afterwards still show an increasing trend but at a much lower rate. Mammography and adjuvant therapy have had a limited impact on mortality. Potential reasons for observed patterns are discussed. An increase in BC mortality in Mexico is expected in the following decades. CONCLUSIONS: Mammography screening programs and timely access to effective treatment should be a national priority to reverse the expected increasing BC mortality trend.OBJETIVO: Evaluar efectos de edad-periodo-cohorte en la mortalidad por cáncer de mama (CaMa en México. MATERIAL Y MÉTODOS: Las tendencias de los efectos de edad-periodo-cohorte fueron estimados mediante un modelo de regresión de Poisson propuesto por Holford. RESULTADOS: Las tasas de mortalidad por CaMa se han estabilizado en la mayoría de los grupos de edad desde 1995 y están determinadas principalmente por efectos de cohorte y edad. Las mujeres nacidas entre 1940 y 1955 muestran los mayores aumentos en la mortalidad en comparación con las nacidas después de este período. La mamografía y la terapia adyuvante han tenido un impacto limitado sobre la mortalidad. Se discuten posibles explicaciones de las tendencias observadas. En las siguientes décadas se espera continúe aumentando la mortalidad por CaMa. CONCLUSIONES: El acceso a mamografía y a tratamiento oportuno y efectivo debieran ser una prioridad para revertir la tendencia creciente esperada de la mortalidad por CM.

Well logging system with linearity control

International Nuclear Information System (INIS)

Jones, J.M.

1973-01-01

Apparatus is described for controlling the gain of a nuclear well logging system comprising: (1) means for measuring the energy spectrum of gamma rays produced by earth formation materials surrounding a well borehole; (2) means for measuring the number of counts of a gamma rays having an energy falling within each of at least two predetermined energy band portions of the gamma ray energy spectrum; (3) means for generating a signal proportional to the ratio of the gamma ray counts and for comparing the ratio signal with at least one constant ratio calibration signal; (4) means for generating an error signal representative of the difference of the ratio signal and the constant ratio calibration signal; and (5) means for using the error signal to control the linearity of the well logging system. (author)

Log-periodic self-similarity: an emerging financial law?

OpenAIRE

S. Drozdz; F. Grummer; F. Ruf; J. Speth

2002-01-01

A hypothesis that the financial log-periodicity, cascading self-similarity through various time scales, carries signatures of a law is pursued. It is shown that the most significant historical financial events can be classified amazingly well using a single and unique value of the preferred scaling factor lambda=2, which indicates that its real value should be close to this number. This applies even to a declining decelerating log-periodic phase. Crucial in this connection is identification o...

Working Life and Retirement Expectancies at Age 50 by Social Class: Period and Cohort Trends and Projections for Finland.

Science.gov (United States)

Leinonen, Taina; Martikainen, Pekka; Myrskylä, Mikko

2018-01-11

The balance between the amount of time spent in work and in retirement underlies the long-term sustainability of the social security system. We examined socioeconomic differences in how increasing longevity is distributed between labor market statuses in Finland. We used register data and the Sullivan method to analyze life expectancy at age 50 spent in different labor market statuses over the period 1989-2012 and across cohorts born in 1938-1953. We projected the future mortality and labor market participation rates of partially observed cohorts. Both working life expectancy at age 50 and the share of remaining life spent in work have increased across periods following the recession of the early 1990s, and across successive cohorts. The trends were similar across the social classes, but there were large differences in the numbers of years spent in various states: for the most recent period and the youngest cohort, we find that compared with upper non-manual employees, male and female manual workers were expected to spend 3.6-3.7 fewer years in work, 1.7-4.7 fewer years in statutory retirement, and 3.2-3.9 more years in other forms of nonemployment. Our finding that the share of remaining life at age 50 spent in work is increasing implies that pressure on the welfare system is not as severe as is commonly thought. © The Author(s) 2015. Published by Oxford University Press on behalf of The Gerontological Society of America. All rights reserved. For permissions, please e-mail: journals.permissions@oup.com.

Log-gamma linear-mixed effects models for multiple outcomes with application to a longitudinal glaucoma study

Science.gov (United States)

Zhang, Peng; Luo, Dandan; Li, Pengfei; Sharpsten, Lucie; Medeiros, Felipe A.

2015-01-01

Glaucoma is a progressive disease due to damage in the optic nerve with associated functional losses. Although the relationship between structural and functional progression in glaucoma is well established, there is disagreement on how this association evolves over time. In addressing this issue, we propose a new class of non-Gaussian linear-mixed models to estimate the correlations among subject-specific effects in multivariate longitudinal studies with a skewed distribution of random effects, to be used in a study of glaucoma. This class provides an efficient estimation of subject-specific effects by modeling the skewed random effects through the log-gamma distribution. It also provides more reliable estimates of the correlations between the random effects. To validate the log-gamma assumption against the usual normality assumption of the random effects, we propose a lack-of-fit test using the profile likelihood function of the shape parameter. We apply this method to data from a prospective observation study, the Diagnostic Innovations in Glaucoma Study, to present a statistically significant association between structural and functional change rates that leads to a better understanding of the progression of glaucoma over time. PMID:26075565

Trends in breast, ovarian and cervical cancer incidence in Mumbai, India over a 30-year period, 1976–2005: an age–period–cohort analysis

Science.gov (United States)

Dhillon, P K; Yeole, B B; Dikshit, R; Kurkure, A P; Bray, F

2011-01-01

Background: Demographic, socioeconomic and cultural changes in India have increased longevity, delayed childbearing, decreased parity and resulted in a more westernised lifestyle, contributing to the increasing burden of cancer, especially among women. Methods: We evaluated secular changes in the incidence of breast, cervical and ovarian cancer in Mumbai women aged 30–64 between 1976 and 2005. Age-standardised incidence rates were calculated and presented by site and calendar period. An age–period–cohort (APC) analysis quantified recent time trends and the significance of birth cohort and calendar period effects. The estimated annual percent change (EAPC) was obtained from the drift parameter, expressing the linear time trend common to both calendar period and birth cohort. Results: Over the 30-year study period, the age-standardised rates significantly increased for breast cancer (EAPC: 1.1% (95% confidence interval (CI): 1.0, 1.3)), significantly decreased for cervical cancer (EAPC: −1.8% (95% CI: −2.0, −1.6)) and there was no statistically significant change for ovarian cancer (EAPC: 0.3% (95% CI: −0.1, 0.6)). For breast and cervical cancer, the best-fitting model was the APC model. Conclusions: The rates of breast, cervical and ovarian cancer remain low in comparison with western countries, and the divergent trends of breast (increasing) and cervical cancer (decreasing) in Mumbai were similar to those observed in several other Asian countries. The changing risk profile in successive generations – improved education, higher socioeconomic status, later age at marriage and at first child, and lower parity – may in combination partially explain the diverging generational changes in breast and cervical cancer in Mumbai in the last decades. PMID:21829198

Introduction to generalized linear models

CERN Document Server

Dobson, Annette J

2008-01-01

Introduction Background Scope Notation Distributions Related to the Normal Distribution Quadratic Forms Estimation Model Fitting Introduction Examples Some Principles of Statistical Modeling Notation and Coding for Explanatory Variables Exponential Family and Generalized Linear Models Introduction Exponential Family of Distributions Properties of Distributions in the Exponential Family Generalized Linear Models Examples Estimation Introduction Example: Failure Times for Pressure Vessels Maximum Likelihood Estimation Poisson Regression Example Inference Introduction Sampling Distribution for Score Statistics Taylor Series Approximations Sampling Distribution for MLEs Log-Likelihood Ratio Statistic Sampling Distribution for the Deviance Hypothesis Testing Normal Linear Models Introduction Basic Results Multiple Linear Regression Analysis of Variance Analysis of Covariance General Linear Models Binary Variables and Logistic Regression Probability Distributions ...

Analysis of RIA standard curve by log-logistic and cubic log-logit models

International Nuclear Information System (INIS)

Yamada, Hideo; Kuroda, Akira; Yatabe, Tami; Inaba, Taeko; Chiba, Kazuo

1981-01-01

In order to improve goodness-of-fit in RIA standard analysis, programs for computing log-logistic and cubic log-logit were written in BASIC using personal computer P-6060 (Olivetti). Iterative least square method of Taylor series was applied for non-linear estimation of logistic and log-logistic. Hear ''log-logistic'' represents Y = (a - d)/(1 + (log(X)/c)sup(b)) + d As weights either 1, 1/var(Y) or 1/σ 2 were used in logistic or log-logistic and either Y 2 (1 - Y) 2 , Y 2 (1 - Y) 2 /var(Y), or Y 2 (1 - Y) 2 /σ 2 were used in quadratic or cubic log-logit. The term var(Y) represents squares of pure error and σ 2 represents estimated variance calculated using a following equation log(σ 2 + 1) = log(A) + J log(y). As indicators for goodness-of-fit, MSL/S sub(e)sup(2), CMD% and WRV (see text) were used. Better regression was obtained in case of alpha-fetoprotein by log-logistic than by logistic. Cortisol standard curve was much better fitted with cubic log-logit than quadratic log-logit. Predicted precision of AFP standard curve was below 5% in log-logistic in stead of 8% in logistic analysis. Predicted precision obtained using cubic log-logit was about five times lower than that with quadratic log-logit. Importance of selecting good models in RIA data processing was stressed in conjunction with intrinsic precision of radioimmunoassay system indicated by predicted precision. (author)

Area under the curve predictions of dalbavancin, a new lipoglycopeptide agent, using the end of intravenous infusion concentration data point by regression analyses such as linear, log-linear and power models.

Science.gov (United States)

Bhamidipati, Ravi Kanth; Syed, Muzeeb; Mullangi, Ramesh; Srinivas, Nuggehally

2018-02-01

1. Dalbavancin, a lipoglycopeptide, is approved for treating gram-positive bacterial infections. Area under plasma concentration versus time curve (AUC inf ) of dalbavancin is a key parameter and AUC inf /MIC ratio is a critical pharmacodynamic marker. 2. Using end of intravenous infusion concentration (i.e. C max ) C max versus AUC inf relationship for dalbavancin was established by regression analyses (i.e. linear, log-log, log-linear and power models) using 21 pairs of subject data. 3. The predictions of the AUC inf were performed using published C max data by application of regression equations. The quotient of observed/predicted values rendered fold difference. The mean absolute error (MAE)/root mean square error (RMSE) and correlation coefficient (r) were used in the assessment. 4. MAE and RMSE values for the various models were comparable. The C max versus AUC inf exhibited excellent correlation (r > 0.9488). The internal data evaluation showed narrow confinement (0.84-1.14-fold difference) with a RMSE models predicted AUC inf with a RMSE of 3.02-27.46% with fold difference largely contained within 0.64-1.48. 5. Regardless of the regression models, a single time point strategy of using C max (i.e. end of 30-min infusion) is amenable as a prospective tool for predicting AUC inf of dalbavancin in patients.

Dissemination of periodic mammography and patterns of use, by birth cohort, in Catalonia (Spain)

Science.gov (United States)

Rue, Montserrat; Carles, Misericordia; Vilaprinyo, Ester; Martinez-Alonso, Montserrat; Espinas, Josep-Alfons; Pla, Roger; Brugulat, Pilar

2008-01-01

Background In Catalonia (Spain) breast cancer mortality has declined since the beginning of the 1990s. The dissemination of early detection by mammography and the introduction of adjuvant treatments are among the possible causes of this decrease, and both were almost coincident in time. Thus, understanding how these procedures were incorporated into use in the general population and in women diagnosed with breast cancer is very important for assessing their contribution to the reduction in breast cancer mortality. In this work we have modeled the dissemination of periodic mammography and described repeat mammography behavior in Catalonia from 1975 to 2006. Methods Cross-sectional data from three Catalan Health Surveys for the calendar years 1994, 2002 and 2006 was used. The dissemination of mammography by birth cohort was modeled using a mixed effects model and repeat mammography behavior was described by age and survey year. Results For women born from 1938 to 1952, mammography clearly had a period effect, meaning that they started to have periodic mammograms at the same calendar years but at different ages. The age at which approximately 50% of the women were receiving periodic mammograms went from 57.8 years of age for women born in 1938–1942 to 37.3 years of age for women born in 1963–1967. Women in all age groups experienced an increase in periodic mammography use over time, although women in the 50–69 age group have experienced the highest increase. Currently, the target population of the Catalan Breast Cancer Screening Program, 50–69 years of age, is the group that self-reports the highest utilization of periodic mammograms, followed by the 40–49 age group. A higher proportion of women of all age groups have annual mammograms rather than biennial or irregular ones. Conclusion Mammography in Catalonia became more widely implemented during the 1990s. We estimated when cohorts initiated periodic mammograms and how frequently women are receiving them

Linearity improvement on wide-range log signal of neutron measurement system for HANARO

International Nuclear Information System (INIS)

Kim, Young-Ki; Tuetken, Jeffrey S.

1998-01-01

This paper discusses engineering activities for improving the linearity characteristics of the Log Power signal from the neutron measurement system for HANARO. This neutron measurement system uses a fission chamber based detector which covers 10.3 decade-wide range from 10 -8 % full power(FP) up to 200%FP, The Log Power signal is designed to control the reactor at low power levels where most of the reactor physics tests are carried out. Therefore, the linearity characteristics of the Log Power signal is the major factor for accurate reactor power control. During the commissioning of the neutron measurement system, it was found that the linearity characteristics of the Log Power signal, especially near 10 -2 %FP, were not accurate enough for controlling the reactor during physics testing. Analysis of the system linearity data directly measured with reactor operating determined that the system was not operating per the design characteristics established from previous installations. The linearity data, which were taken as the reactor was increased in power, were sent to manufacturer's engineering group and a follow-up measures based on the analysis were then fed back to the field. Through step by step trouble-shooting activities, which included minor circuit modifications and alignment procedure changes, the linearity characteristics have been successfully improved and now exceed minimum performance requirements. This paper discusses the trouble-shooting techniques applied, the changes in the linearity characteristics, special circumstances in the HANARO application and the final resolution. (author)

Time trends in exposure of cattle to bovine spongiform encephalopathy and cohort effect in France and Italy: value of the classical Age-Period-Cohort approach.

Science.gov (United States)

Sala, Carole; Ru, Giuseppe

2009-09-18

The Age-Period-Cohort (APC) analysis is routinely used for time trend analysis of cancer incidence or mortality rates, but in veterinary epidemiology, there are still only a few examples of this application. APC models were recently used to model the French epidemic assuming that the time trend for BSE was mainly due to a cohort effect in relation to the control measures that may have modified the BSE exposure of cohorts over time. We used a categorical APC analysis which did not require any functional form for the effect of the variables, and examined second differences to estimate the variation of the BSE trend. We also reanalysed the French epidemic and performed a simultaneous analysis of Italian data using more appropriate birth cohort categories for comparison. We used data from the exhaustive surveillance carried out in France and Italy between 2001 and 2007, and comparatively described the trend of the epidemic in both countries. At the end, the shape and irregularities of the trends were discussed in light of the main control measures adopted to control the disease. In Italy a decrease in the epidemic became apparent from 1996, following the application of rendering standards for the processing of specific risk material (SRM). For the French epidemic, the pattern of second differences in the birth cohorts confirmed the beginning of the decrease from 1995, just after the implementation of the meat and bone meal (MBM) ban for all ruminants (1994). The APC analysis proved to be highly suitable for the study of the trend in BSE epidemics and was helpful in understanding the effects of management and control of the disease. Additionally, such an approach may help in the implementation of changes in BSE regulations.

Dendroclimatic transfer functions revisited: Little Ice Age and Medieval Warm Period summer temperatures reconstructed using artificial neural networks and linear algorithms

Energy Technology Data Exchange (ETDEWEB)

Helama, S.; Holopainen, J.; Eronen, M. [Department of Geology, University of Helsinki, (Finland); Makarenko, N.G. [Russian Academy of Sciences, St. Petersburg (Russian Federation). Pulkovo Astronomical Observatory; Karimova, L.M.; Kruglun, O.A. [Institute of Mathematics, Almaty (Kazakhstan); Timonen, M. [Finnish Forest Research Institute, Rovaniemi Research Unit (Finland); Merilaeinen, J. [SAIMA Unit of the Savonlinna Department of Teacher Education, University of Joensuu (Finland)

2009-07-01

Tree-rings tell of past climates. To do so, tree-ring chronologies comprising numerous climate-sensitive living-tree and subfossil time-series need to be 'transferred' into palaeoclimate estimates using transfer functions. The purpose of this study is to compare different types of transfer functions, especially linear and nonlinear algorithms. Accordingly, multiple linear regression (MLR), linear scaling (LSC) and artificial neural networks (ANN, nonlinear algorithm) were compared. Transfer functions were built using a regional tree-ring chronology and instrumental temperature observations from Lapland (northern Finland and Sweden). In addition, conventional MLR was compared with a hybrid model whereby climate was reconstructed separately for short- and long-period timescales prior to combining the bands of timescales into a single hybrid model. The fidelity of the different reconstructions was validated against instrumental climate data. The reconstructions by MLR and ANN showed reliable reconstruction capabilities over the instrumental period (AD 1802-1998). LCS failed to reach reasonable verification statistics and did not qualify as a reliable reconstruction: this was due mainly to exaggeration of the low-frequency climatic variance. Over this instrumental period, the reconstructed low-frequency amplitudes of climate variability were rather similar by MLR and ANN. Notably greater differences between the models were found over the actual reconstruction period (AD 802-1801). A marked temperature decline, as reconstructed by MLR, from the Medieval Warm Period (AD 931-1180) to the Little Ice Age (AD 1601-1850), was evident in all the models. This decline was approx. 0.5 C as reconstructed by MLR. Different ANN based palaeotemperatures showed simultaneous cooling of 0.2 to 0.5 C, depending on algorithm. The hybrid MLR did not seem to provide further benefit above conventional MLR in our sample. The robustness of the conventional MLR over the calibration

Age, cohort and period effects in the prevalence of sleep disturbances among older people: the impact of economic downturn.

Science.gov (United States)

Dregan, Alex; Armstrong, David

2009-11-01

Using two longitudinal and nationally representative datasets, this study employs a cross-cohort analysis to examine age, cohort and period effects in the prevalence of sleep loss through worry for people over the age of 50 in the UK. The likelihood of reporting sleep loss through worry is calculated at two time-points for 7785 respondents from the Health and Activity Survey (HALs) and 21,834 respondents from the English Longitudinal Study of Ageing (ELSA), with baseline information on sleep loss through worry. Descriptive statistical methods were applied to determine the prevalence rates in sleep loss through worry at each survey within both datasets. The results of analysis reveal that sleep loss through worry declined with age, but this pattern was tempered by a temporary increase in the early 1990s. The contemporary economic downturn is suggested as a possible explanation for the significant increase in the prevalence of sleep loss through worry in 1991.

Sorting Real Numbers in $O(n\\sqrt{\\log n})$ Time and Linear Space

OpenAIRE

Han, Yijie

2017-01-01

We present an $O(n\\sqrt{\\log n})$ time and linear space algorithm for sorting real numbers. This breaks the long time illusion that real numbers have to be sorted by comparison sorting and take $\\Omega (n\\log n)$ time to be sorted.

Periodic feedback stabilization for linear periodic evolution equations

CERN Document Server

Wang, Gengsheng

2016-01-01

This book introduces a number of recent advances regarding periodic feedback stabilization for linear and time periodic evolution equations. First, it presents selected connections between linear quadratic optimal control theory and feedback stabilization theory for linear periodic evolution equations. Secondly, it identifies several criteria for the periodic feedback stabilization from the perspective of geometry, algebra and analyses respectively. Next, it describes several ways to design periodic feedback laws. Lastly, the book introduces readers to key methods for designing the control machines. Given its coverage and scope, it offers a helpful guide for graduate students and researchers in the areas of control theory and applied mathematics.

Combined Log Inventory and Process Simulation Models for the Planning and Control of Sawmill Operations

Science.gov (United States)

Guillermo A. Mendoza; Roger J. Meimban; Philip A. Araman; William G. Luppold

1991-01-01

A log inventory model and a real-time hardwood process simulation model were developed and combined into an integrated production planning and control system for hardwood sawmills. The log inventory model was designed to monitor and periodically update the status of the logs in the log yard. The process simulation model was designed to estimate various sawmill...

Weighted log-linear models for service delivery points in Ethiopia: a case of modern contraceptive users at health facilities.

Science.gov (United States)

Workie, Demeke Lakew; Zike, Dereje Tesfaye; Fenta, Haile Mekonnen; Mekonnen, Mulusew Admasu

2018-05-10

Ethiopia is among countries with low contraceptive usage prevalence rate and resulted in high total fertility rate and unwanted pregnancy which intern affects the maternal and child health status. This study aimed to investigate the major factors that affect the number of modern contraceptive users at service delivery point in Ethiopia. The Performance Monitoring and Accountability2020/Ethiopia data collected between March and April 2016 at round-4 from 461 eligible service delivery points were in this study. The weighted log-linear negative binomial model applied to analyze the service delivery point's data. Fifty percent of service delivery points in Ethiopia given service for 61 modern contraceptive users with the interquartile range of 0.62. The expected log number of modern contraceptive users at rural was 1.05 (95% Wald CI: - 1.42 to - 0.68) lower than the expected log number of modern contraceptive users at urban. In addition, the expected log count of modern contraceptive users at others facility type was 0.58 lower than the expected log count of modern contraceptive users at the health center. The numbers of nurses/midwives were affecting the number of modern contraceptive users. Since, the incidence rate of modern contraceptive users increased by one due to an additional nurse in the delivery point. Among different factors considered in this study, residence, region, facility type, the number of days per week family planning offered, the number of nurses/midwives and number of medical assistants were to be associated with the number of modern contraceptive users. Thus, the Government of Ethiopia would take immediate steps to address causes of the number of modern contraceptive users in Ethiopia.

Who theorizes age? The "socio-demographic variables" device and age-period-cohort analysis in the rhetoric of survey research.

Science.gov (United States)

Rughiniș, Cosima; Humă, Bogdana

2015-12-01

In this paper we argue that quantitative survey-based social research essentializes age, through specific rhetorical tools. We outline the device of 'socio-demographic variables' and we discuss its argumentative functions, looking at scientific survey-based analyses of adult scientific literacy, in the Public Understanding of Science research field. 'Socio-demographics' are virtually omnipresent in survey literature: they are, as a rule, used and discussed as bundles of independent variables, requiring little, if any, theoretical and measurement attention. 'Socio-demographics' are rhetorically effective through their common-sense richness of meaning and inferential power. We identify their main argumentation functions as 'structure building', 'pacification', and 'purification'. Socio-demographics are used to uphold causal vocabularies, supporting the transmutation of the descriptive statistical jargon of 'effects' and 'explained variance' into 'explanatory factors'. Age can also be studied statistically as a main variable of interest, through the age-period-cohort (APC) disambiguation technique. While this approach has generated interesting findings, it did not mitigate the reductionism that appears when treating age as a socio-demographic variable. By working with age as a 'socio-demographic variable', quantitative researchers convert it (inadvertently) into a quasi-biological feature, symmetrical, as regards analytical treatment, with pathogens in epidemiological research. Copyright © 2015 Elsevier Inc. All rights reserved.

Seventy Years of Asthma in Italy: Age, Period and Cohort Effects on Incidence and Remission of Self-Reported Asthma from 1940 to 2010.

Directory of Open Access Journals (Sweden)

Giancarlo Pesce

Full Text Available It is well known that asthma prevalence has been increasing all over the world in the last decades. However, few data are available on temporal trends of incidence and remission of asthma.To evaluate the rates of asthma incidence and remission in Italy from 1940 to 2010.The subjects were randomly sampled from the general Italian population between 1991 and 2010 in the three population-based multicentre studies: ECRHS, ISAYA, and GEIRD. Individual information on the history of asthma (age at onset, age at the last attack, use of drugs for asthma control, co-presence of hay-fever was collected on 35,495 subjects aged 20-84 and born between 1925-1989. Temporal changes in rates of asthma incidence and remission in relation to age, birth cohort and calendar period (APC were modelled using Poisson regression and APC models.The average yearly rate of asthma incidence was 2.6/1000 (3,297 new cases among 1,263,885 person-years. The incidence rates have been linearly increasing, with a percentage increase of +3.9% (95%CI: 3.1-4.5, from 1940 up to the year 1995, when the rates begun to level off. The stabilization of asthma incidence was mainly due to a decrease in the rates of atopic asthma after 1995, while non-atopic asthma has continued to increase. The overall rate of remission was 43.2/1000person-years, and it did not vary significantly across generations, but was associated with atopy, age at asthma onset and duration of the disease.After 50 years of a continuous upward trend, the rates of asthma incidence underwent a substantial stabilization in the late 90s. Despite remarkable improvements in the treatment of asthma, the rate of remission did not change significantly in the last seventy years. Some caveats are required in interpreting our results, given that our estimates are based on self-reported events that could be affected by the recall bias.

Trends of stomach cancer mortality in Eastern Asia in 1950-2004: comparative study of Japan, Hong Kong and Singapore using age, period and cohort analysis.

Science.gov (United States)

Tanaka, Masahiro; Ma, Enbo; Tanaka, Hideo; Ioka, Akiko; Nakahara, Toshitaka; Takahashi, Hideto

2012-02-15

To characterize the temporal trends of stomach cancer mortality in Eastern Asia and to better interpret the causes of the trends, we performed age, period and cohort analysis (APC analysis) on the mortality rates in Japan, Hong Kong and Singapore during 1950-2004, as well as the rates in the US as a control population. For the APC analysis, Holford's approach was used to avoid the identification problem. Age-standardized mortality rates (ASMR) decreased consistently in all four areas during the observation period in both males and females. Japan had the highest ASMR in both sexes, followed by Singapore, Hong Kong and the US, but the differences in ASMR among the four areas diminished with time. The results of APC analysis suggested that the decreasing mortality rates in Eastern Asia were caused by the combination of decreasing cohort effect since the end of the 1800s and decreasing period effect from the 1950s. The US showed similar results, but its decreases in the period and cohort effect preceded those of Eastern Asia. Possible causes for the decrease in the cohort effect include improvement in the socioeconomic conditions during childhood and a decrease in the prevalence of H. pylori infection, while possible causes for the decrease in the period effect include a decrease in dietary salt intake and improvements in cancer detection and treatment. These findings may help us to predict future changes in the mortality rates of stomach cancer. Copyright © 2011 UICC.

Economic independence in survivors of cancer diagnosed at a young age: A Norwegian national cohort study.

Science.gov (United States)

Gunnes, Maria W; Lie, Rolv Terje; Bjørge, Tone; Syse, Astri; Ruud, Ellen; Wesenberg, Finn; Moster, Dag

2016-12-15

The impact of cancer on socioeconomic outcomes is attracting attention as the number of survivors of cancer in young age continues to rise. This study examines economic independence in a national cohort of survivors of cancer at a young age in Norway. Through the linkage of several national registries, the study cohort comprised 1,212,013 individuals born in Norway during 1965 through 1985, of which 5440 had received a cancer diagnosis before age 25 years. Follow-up was through 2007, and the main outcomes were receipt of governmental financial assistance, employment, income, and occupation. Analytic methods included Cox proportional hazard regression, log-binomial regression, and quantile regression models. Individuals in the cancer survivor group had an increased probability of receiving governmental financial assistance (men: hazard ratio [HR], 1.4; 95% confidence interval [CI], 1.3-1.5; women: HR, 1.5; 95% CI, 1.3-1.6) and of not being employed (men: HR, 1.4; 95% CI, 1.2-1.7; women: HR, 1.4; 95% CI, 1.2-1.6) compared with those in the noncancer group. Income discrepancies were particularly pronounced for survivors of central nervous system tumors. There was no difference in representation in higher skilled occupations. Survivors of cancer at a young age in Norway had an increased risk of being economically dependent and unemployed. This was evident in several tumor groups and was most pronounced in female survivors. There were only small differences in income or representation in higher skilled occupations for most employed survivors compared with the noncancer group. The current results are important for understanding the impact of a cancer diagnosis at a young age on subsequent job market outcomes. Cancer 2016;122:3873-3882. © 2016 The Authors. Cancer published by Wiley Periodicals, Inc. on behalf of American Cancer Society. © 2016 The Authors. Cancer published by Wiley Periodicals, Inc. on behalf of American Cancer Society.

Cognitive Ageing in Great Britain in the New Century: Cohort Differences in Episodic Memory.

Directory of Open Access Journals (Sweden)

Gindo Tampubolon

Full Text Available Dementias in high income countries are set to be the third major burden of disease even as older people are increasingly required to think for themselves how to provide for their lives in retirement. Meanwhile the period of older age continues to extend with increase in life expectancy. This challenge demands an understanding of how cognition changes over an extended period in later life. But studying cognitive ageing in the population faces a difficulty from the fact that older respondents are liable to leave (attrite before study completion. This study tested three hypotheses: trajectories of cognitive ageing in Britain show an improvement beyond the age of 50; and they are lifted by secular improvement in cognition across cohorts; lastly they are susceptible to distortion due to attrition.Using the English Longitudinal Study of Ageing, this paper studied trajectories of episodic memory of Britons aged 50-89 from 2002 to 2013 (N = 5931. Using joint models the analysis found that levels of episodic memory follow a curvilinear shape, not a steady decline, in later life. The findings also revealed secular improvement in cognitive ageing such that as a cohort is being replaced episodic memory levels in the population improve. The analysis lastly demonstrated that failure to simultaneously model attrition can produce distorted pictures of cognitive ageing.Old age in this century is not necessarily a period dominated by cognitive decline. In identifying behavioural factors associated with better cognitive ageing, such as social connections of traditional and online kinds, the paper raises possibilities of mustering an adequate response to the cognition challenge.

[Using log-binomial model for estimating the prevalence ratio].

Science.gov (United States)

Ye, Rong; Gao, Yan-hui; Yang, Yi; Chen, Yue

2010-05-01

To estimate the prevalence ratios, using a log-binomial model with or without continuous covariates. Prevalence ratios for individuals' attitude towards smoking-ban legislation associated with smoking status, estimated by using a log-binomial model were compared with odds ratios estimated by logistic regression model. In the log-binomial modeling, maximum likelihood method was used when there were no continuous covariates and COPY approach was used if the model did not converge, for example due to the existence of continuous covariates. We examined the association between individuals' attitude towards smoking-ban legislation and smoking status in men and women. Prevalence ratio and odds ratio estimation provided similar results for the association in women since smoking was not common. In men however, the odds ratio estimates were markedly larger than the prevalence ratios due to a higher prevalence of outcome. The log-binomial model did not converge when age was included as a continuous covariate and COPY method was used to deal with the situation. All analysis was performed by SAS. Prevalence ratio seemed to better measure the association than odds ratio when prevalence is high. SAS programs were provided to calculate the prevalence ratios with or without continuous covariates in the log-binomial regression analysis.

Homicides among women in the different Brazilian regions in the last 35 years: an analysis of age-period-birth cohort effects.

Science.gov (United States)

Souza, Edinilsa Ramos de; Meira, Karina Cardoso; Ribeiro, Adalgisa Peixoto; Santos, Juliano Dos; Guimarães, Raphael Mendonça; Borges, Laiane Felix; Oliveira, Lannuzya Veríssimo E; Simões, Taynãna César

2017-09-01

The aim of this study is to estimate the effects of age-period-birth cohort (APC) on female homicides. This is an ecological study which analyzed the violence-related death records of women aged 10 years and older, in the Brazilian geographic regions, between 1980 and 2014. Data on mortality were extracted from the Mortality Information System. The trend analysis was conducted using negative binomial regression and APC effects were analyzed using estimable functions. The average mortality rate for the period was 5.13 deaths per 100,000 women, with the highest rates observed in the Central-West (7.98 deaths), followed by the Southeast (4.78 deaths), North (4.77 deaths), Northeast (4.05 deaths) and South (3.82 deaths) regions. All regions presented a decrease in the risk of death in the period from 2010 to 2014, except for the Northeast region (RR = 1.06, 95% CI 1.02 to 1.10). There was a progressive increase in the homicide risk for women born from 1955 to 1959 in all Brazilian regions. Younger women are at higher risk of dying from homicides in all Brazilian geographic regions. The upward trend of homicide mortality rates according to birth cohort was significant and the highest risk was observed in women born between 2000 and 2004.

Age, period, and cohort effects in motor vehicle mortality in the United States, 1980-2010: the role of sex, alcohol involvement, and position in vehicle.

Science.gov (United States)

Macinko, James; Silver, Diana; Bae, Jin Yung

2015-02-01

Although substantive declines in motor vehicle fatalities in 1980-2010 have been observed, declines by position in the vehicle and alcohol involvement have not been well elucidated. Analyses of FARS data use the Intrinsic Estimator (IE) to produce estimates of all age, period, and cohort effects simultaneously by position in the car and by alcohol involvement. Declines in MVC deaths by position in the car vary for men and women by age and cohort over time. Cohorts born before 1970 had higher risks than those born later. Analyses using proxy indicators of alcohol involvement found the highest risks for those aged 16-24. By period, these risks declined more rapidly than non- alcohol related traffic fatalities. Changes in risk patterns are consistent with evidence regarding the contributions of new technologies and public policy efforts to reduce fatalities, but gains have not been shared evenly by sex or position in the car. Greater attention is needed in reducing deaths among older drivers and pedestrians. Gender differences should be addressed in prevention efforts aimed at reducing MVCs due to alcohol involvement. Copyright © 2014 Elsevier Ltd and National Safety Council. All rights reserved.

The log-linear response function of the bounded number-line task is unrelated to the psychological representation of quantity.

Science.gov (United States)

Cohen, Dale J; Quinlan, Philip T

2018-02-01

The bounded number-line task has been used extensively to assess the numerical competence of both children and adults. One consistent finding has been that young children display a logarithmic response function, whereas older children and adults display a more linear response function. Traditionally, these log-linear functions have been interpreted as providing a transparent window onto the nature of the participants' psychological representations of quantity (termed here a direct response strategy). Here we show that the direct response strategy produces the log-linear response function regardless of whether the psychological representation of quantity is compressive or expansive. Simply put, the log-linear response function results from task constraints rather than from the psychological representation of quantities. We also demonstrate that a proportion/subtraction response strategy produces response patterns that almost perfectly correlate with the psychological representation of quantity. We therefore urge researchers not to interpret the log-linear response pattern in terms of numerical representation.

Identifying Plant Part Composition of Forest Logging Residue Using Infrared Spectral Data and Linear Discriminant Analysis

Directory of Open Access Journals (Sweden)

Gifty E. Acquah

2016-08-01

Full Text Available As new markets, technologies and economies evolve in the low carbon bioeconomy, forest logging residue, a largely untapped renewable resource will play a vital role. The feedstock can however be variable depending on plant species and plant part component. This heterogeneity can influence the physical, chemical and thermochemical properties of the material, and thus the final yield and quality of products. Although it is challenging to control compositional variability of a batch of feedstock, it is feasible to monitor this heterogeneity and make the necessary changes in process parameters. Such a system will be a first step towards optimization, quality assurance and cost-effectiveness of processes in the emerging biofuel/chemical industry. The objective of this study was therefore to qualitatively classify forest logging residue made up of different plant parts using both near infrared spectroscopy (NIRS and Fourier transform infrared spectroscopy (FTIRS together with linear discriminant analysis (LDA. Forest logging residue harvested from several Pinus taeda (loblolly pine plantations in Alabama, USA, were classified into three plant part components: clean wood, wood and bark and slash (i.e., limbs and foliage. Five-fold cross-validated linear discriminant functions had classification accuracies of over 96% for both NIRS and FTIRS based models. An extra factor/principal component (PC was however needed to achieve this in FTIRS modeling. Analysis of factor loadings of both NIR and FTIR spectra showed that, the statistically different amount of cellulose in the three plant part components of logging residue contributed to their initial separation. This study demonstrated that NIR or FTIR spectroscopy coupled with PCA and LDA has the potential to be used as a high throughput tool in classifying the plant part makeup of a batch of forest logging residue feedstock. Thus, NIR/FTIR could be employed as a tool to rapidly probe/monitor the variability

An Alternative Approach to Non-Log-Linear Thermal Microbial Inactivation: Modelling the Number of Log Cycles Reduction with Respect to Temperature

Directory of Open Access Journals (Sweden)

Vasilis Panagiotis Valdramidis

2005-01-01

Full Text Available A mathematical approach incorporating the shoulder effect during the quantification of microbial heat inactivation is being developed based on »the number of log cycles of reduction « concept. Hereto, the heat resistance of Escherichia coli K12 in BHI broth has been quantitatively determined in a generic and accurate way by defining the time t for x log reductions in the microbial population, i.e. txD, as a function of the treatment temperature T. Survival data of the examined microorganism are collected in a range of temperatures between 52–60.6 °C. Shoulder length Sl and specific inactivation rate kmax are derived from a mathematical expression that describes a non-log-linear behaviour. The temperature dependencies of Sl and kmax are used for structuring the txD(T function. Estimation of the txD(T parameters through a global identification procedure permits reliable predictions of the time to achieve a pre-decided microbial reduction. One of the parameters of the txD(T function is proposed as »the reference minimum temperature for inactivation«. For the case study considered, a value of 51.80 °C (with a standard error, SE, of 3.47 was identified. Finally, the time to achieve commercial sterilization and pasteurization for the product at hand, i.e. BHI broth, was found to be 11.70 s (SE=5.22, and 5.10 min (SE=1.22, respectively. Accounting for the uncertainty (based on the 90 % confidence intervals, CI a fail-safe treatment of these two processes takes 20.36 s and 7.12 min, respectively.

Modelling lactation curve for milk fat to protein ratio in Iranian buffaloes (Bubalus bubalis) using non-linear mixed models.

Science.gov (United States)

Hossein-Zadeh, Navid Ghavi

2016-08-01

The aim of this study was to compare seven non-linear mathematical models (Brody, Wood, Dhanoa, Sikka, Nelder, Rook and Dijkstra) to examine their efficiency in describing the lactation curves for milk fat to protein ratio (FPR) in Iranian buffaloes. Data were 43 818 test-day records for FPR from the first three lactations of Iranian buffaloes which were collected on 523 dairy herds in the period from 1996 to 2012 by the Animal Breeding Center of Iran. Each model was fitted to monthly FPR records of buffaloes using the non-linear mixed model procedure (PROC NLMIXED) in SAS and the parameters were estimated. The models were tested for goodness of fit using Akaike's information criterion (AIC), Bayesian information criterion (BIC) and log maximum likelihood (-2 Log L). The Nelder and Sikka mixed models provided the best fit of lactation curve for FPR in the first and second lactations of Iranian buffaloes, respectively. However, Wood, Dhanoa and Sikka mixed models provided the best fit of lactation curve for FPR in the third parity buffaloes. Evaluation of first, second and third lactation features showed that all models, except for Dijkstra model in the third lactation, under-predicted test time at which daily FPR was minimum. On the other hand, minimum FPR was over-predicted by all equations. Evaluation of the different models used in this study indicated that non-linear mixed models were sufficient for fitting test-day FPR records of Iranian buffaloes.

Delirium symptoms are associated with decline in cognitive function between ages 53 and 69 years: Findings from a British birth cohort study.

Science.gov (United States)

Tsui, Alex; Kuh, Diana; Richards, Marcus; Davis, Daniel

2017-11-21

Few population studies have investigated whether longitudinal decline after delirium in mid-to-late life might affect specific cognitive domains. Participants from a birth cohort completing assessments of search speed, verbal memory, and the Addenbrooke's Cognitive Examination at age 69 were asked about delirium symptoms between ages 60 and 69 years. Linear regression models estimated associations between delirium symptoms and cognitive outcomes. Period prevalence of delirium between 60 and 69 years was 4% (95% confidence interval 3.2%-4.9%). Self-reported symptoms of delirium over the seventh decade were associated with worse scores in the Addenbrooke's Cognitive Examination (-1.7 points; 95% confidence interval -3.2, -0.1; P = .04). In association with delirium symptoms, verbal memory scores were initially lower, with subsequent decline in search speed by the age of 69 years. These effects were independent of other Alzheimer's risk factors. Delirium symptoms may be common even at relatively younger ages, and their presence may herald cognitive decline, particularly in search speed, over this time period. Copyright © 2017 The Authors. Published by Elsevier Inc. All rights reserved.

Disparities of time trends and birth cohort effects on invasive breast cancer incidence in Shanghai and Hong Kong pre- and post-menopausal women.

Science.gov (United States)

Wang, Feng; Tse, Lap Ah; Chan, Wing-Cheong; Kwok, Carol Chi-Hei; Leung, Siu-Lan; Wu, Cherry; Mang, Oscar Wai-Kong; Ngan, Roger Kai-Cheong; Li, Mengjie; Yu, Wai-Cho; Tsang, Koon-Ho; Law, Sze-Hong; Miao, Xiaoping; Wu, Chunxiao; Zheng, Ying; Wu, Fan; Yang, Xiaohong R; Yu, Ignatius Tak-Sun

2017-05-23

Breast cancer is the leading cause of cancer morbidity among Shanghai and Hong Kong women, which contributes to 20-25% of new female cancer incidents. This study aimed to describe the temporal trend of breast cancer and interpret the potential effects on the observed secular trends. Cancer incident data were obtained from the cancer registries. Age-standardized incidence rate was computed by the direct method using the World population of 2000. Average annual percentage change (AAPC) in incidence rate was estimated by the Joinpoint regression. Age, period and cohort effects were assessed by using a log-linear model with Poisson regression. During 1976-2009, an increasing trend of breast cancer incidence was observed, with an AAPC of 1.73 [95% confidence interval (CI): 1.54-1.92)] for women in Hong Kong and 2.83 (95% CI, 2.26-3.40) in Shanghai. Greater upward trends were revealed in Shanghai women aged 50 years old or above (AAPC = 3.09; 95% CI, 1.48-4.73). Using age at 50 years old as cut-point, strong birth cohort effects were shown in both pre- and post-menopausal women, though a more remarkable effect was suggested in Shanghai post-menopausal women. No evidence for a period effect was indicated. Incidence rate of breast cancer has been more speedy in Shanghai post-menopausal women than that of the Hong Kong women over the past 30 years. Decreased birth rate and increasing environmental exposures (e.g., light-at-night) over successive generations may have constituted major impacts on the birth cohort effects, especially for the post-menopausal breast cancer; further analytic studies are warranted.

Modeling Precipitation Extremes using Log-Histospline

Science.gov (United States)

Huang, W. K.; Nychka, D. W.; Zhang, H.

2017-12-01

One of the commonly used approaches to modeling univariate extremes is the peaks-overthreshold (POT) method. The POT method models exceedances over a (sufficiently high/low) threshold as a generalized Pareto distribution (GPD). To apply this method, a threshold has to be chosen and the estimates might be sensitive to the chosen threshold. Here we propose an alternative, the "Log-Histospline", to explore modeling the tail behavior and the remainder of the density in one step using the full range of the data. Log-Histospline applies a smoothing spline model on a finely binned histogram of the log transformed data to estimate its log density. By construction, we are able to preserve the polynomial upper tail behavior, a feature commonly observed in geophysical observations. The Log-Histospline can be extended to the spatial setting by treating the marginal (log) density at each location as spatially indexed functional data, and perform a dimension reduction and spatial smoothing. We illustrate the proposed method by analyzing precipitation data from regional climate model output (North American Regional Climate Change and Assessment Program (NARCCAP)).

Nonparametric Analyses of Log-Periodic Precursors to Financial Crashes

Science.gov (United States)

Zhou, Wei-Xing; Sornette, Didier

We apply two nonparametric methods to further test the hypothesis that log-periodicity characterizes the detrended price trajectory of large financial indices prior to financial crashes or strong corrections. The term "parametric" refers here to the use of the log-periodic power law formula to fit the data; in contrast, "nonparametric" refers to the use of general tools such as Fourier transform, and in the present case the Hilbert transform and the so-called (H, q)-analysis. The analysis using the (H, q)-derivative is applied to seven time series ending with the October 1987 crash, the October 1997 correction and the April 2000 crash of the Dow Jones Industrial Average (DJIA), the Standard & Poor 500 and Nasdaq indices. The Hilbert transform is applied to two detrended price time series in terms of the ln(tc-t) variable, where tc is the time of the crash. Taking all results together, we find strong evidence for a universal fundamental log-frequency f=1.02±0.05 corresponding to the scaling ratio λ=2.67±0.12. These values are in very good agreement with those obtained in earlier works with different parametric techniques. This note is extracted from a long unpublished report with 58 figures available at , which extensively describes the evidence we have accumulated on these seven time series, in particular by presenting all relevant details so that the reader can judge for himself or herself the validity and robustness of the results.

Accumulation of unstable periodic orbits and the stickiness in the two-dimensional piecewise linear map.

Science.gov (United States)

Akaishi, A; Shudo, A

2009-12-01

We investigate the stickiness of the two-dimensional piecewise linear map with a family of marginal unstable periodic orbits (FMUPOs), and show that a series of unstable periodic orbits accumulating to FMUPOs plays a significant role to give rise to the power law correlation of trajectories. We can explicitly specify the sticky zone in which unstable periodic orbits whose stability increases algebraically exist, and find that there exists a hierarchy in accumulating periodic orbits. In particular, the periodic orbits with linearly increasing stability play the role of fundamental cycles as in the hyperbolic systems, which allows us to apply the method of cycle expansion. We also study the recurrence time distribution, especially discussing the position and size of the recurrence region. Following the definition adopted in one-dimensional maps, we show that the recurrence time distribution has an exponential part in the short time regime and an asymptotic power law part. The analysis on the crossover time T(c)(*) between these two regimes implies T(c)(*) approximately -log[micro(R)] where micro(R) denotes the area of the recurrence region.

DOE-Grand Junction logging model data synopsis

International Nuclear Information System (INIS)

Mathews, M.A.; Koizumi, C.J.; Evans, H.B.

1978-05-01

This synopsis provides the available data concerning the logging models at the DoE-Grand Junction facility, to date (1976). Because gamma-ray logs are used in uranium exploration to estimate the grade (percent U 3 O 8 ) and the thickness of uranium ore zones in exploration drill holes, logging models are required to calibrate the gamma-ray logging equipment in order to obtain accuracy, uniformity, standardization, and repeatability during logging. This quality control is essential for accurate ore reserve calculations and for estimates of ore potential. The logging models at the DoE-Grand Junction facility are available for use by private industry in calibrating their gamma-ray logging equipment. 21 figures, 26 tables

Age at exposure and attained age variations of cancer risk in the Japanese A-bomb and radiotherapy cohorts.

Science.gov (United States)

Schneider, Uwe; Walsh, Linda

2015-08-01

Phenomenological risk models for radiation-induced cancer are frequently applied to estimate the risk of radiation-induced cancers at radiotherapy doses. Such models often include the effect modification, of the main risk to radiation dose response, by age at exposure and attained age. The aim of this paper is to compare the patterns in risk effect modification by age, between models obtained from the Japanese atomic-bomb (A-bomb) survivor data and models for cancer risks previously reported for radiotherapy patients. Patterns in risk effect modification by age from the epidemiological studies of radiotherapy patients were also used to refine and extend the risk effect modification by age obtained from the A-bomb survivor data, so that more universal models can be presented here. Simple log-linear and power functions of age for the risk effect modification applied in models of the A-bomb survivor data are compared to risks from epidemiological studies of second cancers after radiotherapy. These functions of age were also refined and fitted to radiotherapy risks. The resulting age models provide a refined and extended functional dependence of risk with age at exposure and attained age especially beyond 40 and 65 yr, respectively, and provide a better representation than the currently available simple age functions. It was found that the A-bomb models predict risk similarly to the outcomes of testicular cancer survivors. The survivors of Hodgkin's disease show steeper variations of risk with both age at exposure and attained age. The extended models predict solid cancer risk increase as a function of age at exposure beyond 40 yr and the risk decrease as a function of attained age beyond 65 yr better than the simple models. The standard functions for risk effect modification by age, based on the A-bomb survivor data, predict second cancer risk in radiotherapy patients for ages at exposure prior to 40 yr and attained ages before 55 yr reasonably well. However, for

Age, period, and cohort analysis of regular dental care behavior and edentulism: A marginal approach

Science.gov (United States)

2011-01-01

Background To analyze the regular dental care behavior and prevalence of edentulism in adult Danes, reported in sequential cross-sectional oral health surveys by the application of a marginal approach to consider the possible clustering effect of birth cohorts. Methods Data from four sequential cross-sectional surveys of non-institutionalized Danes conducted from 1975-2005 comprising 4330 respondents aged 15+ years in 9 birth cohorts were analyzed. The key study variables were seeking dental care on an annual basis (ADC) and edentulism. For the analysis of ADC, survey year, age, gender, socio-economic status (SES) group, denture-wearing, and school dental care (SDC) during childhood were considered. For the analysis of edentulism, only respondents aged 35+ years were included. Survey year, age, gender, SES group, ADC, and SDC during childhood were considered as the independent factors. To take into account the clustering effect of birth cohorts, marginal logistic regressions with an independent correlation structure in generalized estimating equations (GEE) were carried out, with PROC GENMOD in SAS software. Results The overall proportion of people seeking ADC increased from 58.8% in 1975 to 86.7% in 2005, while for respondents aged 35 years or older, the overall prevalence of edentulism (35+ years) decreased from 36.4% in 1975 to 5.0% in 2005. Females, respondents in the higher SES group, in more recent survey years, with no denture, and receiving SDC in all grades during childhood were associated with higher probability of seeking ADC regularly (P dental health policy was demonstrated by a continued increase of regular dental visiting habits and tooth retention in adults because school dental care was provided to Danes in their childhood. PMID:21410991

The Dangers of Estimating V˙O2max Using Linear, Nonexercise Prediction Models.

Science.gov (United States)

Nevill, Alan M; Cooke, Carlton B

2017-05-01

This study aimed to compare the accuracy and goodness of fit of two competing models (linear vs allometric) when estimating V˙O2max (mL·kg·min) using nonexercise prediction models. The two competing models were fitted to the V˙O2max (mL·kg·min) data taken from two previously published studies. Study 1 (the Allied Dunbar National Fitness Survey) recruited 1732 randomly selected healthy participants, 16 yr and older, from 30 English parliamentary constituencies. Estimates of V˙O2max were obtained using a progressive incremental test on a motorized treadmill. In study 2, maximal oxygen uptake was measured directly during a fatigue limited treadmill test in older men (n = 152) and women (n = 146) 55 to 86 yr old. In both studies, the quality of fit associated with estimating V˙O2max (mL·kg·min) was superior using allometric rather than linear (additive) models based on all criteria (R, maximum log-likelihood, and Akaike information criteria). Results suggest that linear models will systematically overestimate V˙O2max for participants in their 20s and underestimate V˙O2max for participants in their 60s and older. The residuals saved from the linear models were neither normally distributed nor independent of the predicted values nor age. This will probably explain the absence of a key quadratic age term in the linear models, crucially identified using allometric models. Not only does the curvilinear age decline within an exponential function follow a more realistic age decline (the right-hand side of a bell-shaped curve), but the allometric models identified either a stature-to-body mass ratio (study 1) or a fat-free mass-to-body mass ratio (study 2), both associated with leanness when estimating V˙O2max. Adopting allometric models will provide more accurate predictions of V˙O2max (mL·kg·min) using plausible, biologically sound, and interpretable models.

[Evaluation of estimation of prevalence ratio using bayesian log-binomial regression model].

Science.gov (United States)

Gao, W L; Lin, H; Liu, X N; Ren, X W; Li, J S; Shen, X P; Zhu, S L

2017-03-10

To evaluate the estimation of prevalence ratio ( PR ) by using bayesian log-binomial regression model and its application, we estimated the PR of medical care-seeking prevalence to caregivers' recognition of risk signs of diarrhea in their infants by using bayesian log-binomial regression model in Openbugs software. The results showed that caregivers' recognition of infant' s risk signs of diarrhea was associated significantly with a 13% increase of medical care-seeking. Meanwhile, we compared the differences in PR 's point estimation and its interval estimation of medical care-seeking prevalence to caregivers' recognition of risk signs of diarrhea and convergence of three models (model 1: not adjusting for the covariates; model 2: adjusting for duration of caregivers' education, model 3: adjusting for distance between village and township and child month-age based on model 2) between bayesian log-binomial regression model and conventional log-binomial regression model. The results showed that all three bayesian log-binomial regression models were convergence and the estimated PRs were 1.130(95 %CI : 1.005-1.265), 1.128(95 %CI : 1.001-1.264) and 1.132(95 %CI : 1.004-1.267), respectively. Conventional log-binomial regression model 1 and model 2 were convergence and their PRs were 1.130(95 % CI : 1.055-1.206) and 1.126(95 % CI : 1.051-1.203), respectively, but the model 3 was misconvergence, so COPY method was used to estimate PR , which was 1.125 (95 %CI : 1.051-1.200). In addition, the point estimation and interval estimation of PRs from three bayesian log-binomial regression models differed slightly from those of PRs from conventional log-binomial regression model, but they had a good consistency in estimating PR . Therefore, bayesian log-binomial regression model can effectively estimate PR with less misconvergence and have more advantages in application compared with conventional log-binomial regression model.

Linear and nonlinear methods in modeling the aqueous solubility of organic compounds.

Science.gov (United States)

Catana, Cornel; Gao, Hua; Orrenius, Christian; Stouten, Pieter F W

2005-01-01

Solubility data for 930 diverse compounds have been analyzed using linear Partial Least Square (PLS) and nonlinear PLS methods, Continuum Regression (CR), and Neural Networks (NN). 1D and 2D descriptors from MOE package in combination with E-state or ISIS keys have been used. The best model was obtained using linear PLS for a combination between 22 MOE descriptors and 65 ISIS keys. It has a correlation coefficient (r2) of 0.935 and a root-mean-square error (RMSE) of 0.468 log molar solubility (log S(w)). The model validated on a test set of 177 compounds not included in the training set has r2 0.911 and RMSE 0.475 log S(w). The descriptors were ranked according to their importance, and at the top of the list have been found the 22 MOE descriptors. The CR model produced results as good as PLS, and because of the way in which cross-validation has been done it is expected to be a valuable tool in prediction besides PLS model. The statistics obtained using nonlinear methods did not surpass those got with linear ones. The good statistic obtained for linear PLS and CR recommends these models to be used in prediction when it is difficult or impossible to make experimental measurements, for virtual screening, combinatorial library design, and efficient leads optimization.

Model wells for nuclear well logging

International Nuclear Information System (INIS)

Tittle, C.W.

1989-01-01

Considerations needed in the design and construction of model wells for nuclear log calibration are covered, with special attention to neutron porosity logging and total γ-ray logging. Pulsed neutron decay-time and spectral γ-ray logging are discussed briefly. The American Petroleum Institute calibration facility for nuclear logs is a good starting point for similar or expanded facilities. A few of its shortcomings are mentioned; they are minor. The problem of fluid saturation is emphasized. Attention is given to models made of consolidated rock and those containing unconsolidated material such as Ottawa sand. Needed precautions are listed. A similarity method is presented for estimating the porosity index of formations that are not fully saturated. (author)

Economic Stressors and Psychological Distress: Exploring Age Cohort Variation in the Wake of the Great Recession.

Science.gov (United States)

Brown, Robyn Lewis; Richman, Judith A; Rospenda, Kathleen M

2017-08-01

This study examined processes linking age cohort, economic stressors, coping strategies and two indicators of psychological distress (i.e. depressive symptoms and anxiety symptoms). Structural equation models were conducted utilizing data from a national survey that was undertaken in order to understand life change consequences of the period of economic downturn from 2007 to 2009 known as the Great Recession. Findings revealed that the associations between economic stressors and symptoms of both depression and anxiety were significantly greater for members of the millennial cohort compared with baby boomers. These effects are partly explained by the greater tendency of members of the baby boomer cohort to use active coping strategies. These findings clarify the circumstances in which age matters most for the associations among economy-related stressors, coping strategies and psychological well-being. They highlight how difficult economic circumstances influence the availability of coping strategies and, in turn, psychological well-being-and differently for younger and older age cohorts. Copyright © 2016 John Wiley & Sons, Ltd. Copyright © 2016 John Wiley & Sons, Ltd.

Minimizing bias in biomass allometry: Model selection and log transformation of data

Science.gov (United States)

Joseph Mascaro; undefined undefined; Flint Hughes; Amanda Uowolo; Stefan A. Schnitzer

2011-01-01

Nonlinear regression is increasingly used to develop allometric equations for forest biomass estimation (i.e., as opposed to the raditional approach of log-transformation followed by linear regression). Most statistical software packages, however, assume additive errors by default, violating a key assumption of allometric theory and possibly producing spurious models....

A Hierarchical Poisson Log-Normal Model for Network Inference from RNA Sequencing Data

Science.gov (United States)

Gallopin, Mélina; Rau, Andrea; Jaffrézic, Florence

2013-01-01

Gene network inference from transcriptomic data is an important methodological challenge and a key aspect of systems biology. Although several methods have been proposed to infer networks from microarray data, there is a need for inference methods able to model RNA-seq data, which are count-based and highly variable. In this work we propose a hierarchical Poisson log-normal model with a Lasso penalty to infer gene networks from RNA-seq data; this model has the advantage of directly modelling discrete data and accounting for inter-sample variance larger than the sample mean. Using real microRNA-seq data from breast cancer tumors and simulations, we compare this method to a regularized Gaussian graphical model on log-transformed data, and a Poisson log-linear graphical model with a Lasso penalty on power-transformed data. For data simulated with large inter-sample dispersion, the proposed model performs better than the other methods in terms of sensitivity, specificity and area under the ROC curve. These results show the necessity of methods specifically designed for gene network inference from RNA-seq data. PMID:24147011

Age-related changes in cortical bone mass: data from a German female cohort

International Nuclear Information System (INIS)

Toledo, V.A. Molina; Jergas, M.

2006-01-01

To describe data from digital radiogrammetry (DXR) in an unselected German female cohort over a wide age range. Using a retrospective study design we analyzed radiographs of the hand from 540 German women (aged 5-96 years) using an automated assessment of cortical thickness, metacarpal index (MCI), and estimated cortical bone mineral density (DXR-BMD) on digitized radiographs. Both hands were radiographed in 97 women. In this group DXR-BMD and cortical thickness were significantly higher in the right metacarpals while there was no significant difference in MCI. To study the association with age we differentiated young ( 45 years). In young women all parameters increased significantly with age in a linear fashion (r=0.8 for DXR-BMD, r=0.7 for MCI). In those aged 25-45 years DXR-BMD and MCI were highest (peak bone mass). In women aged 45 or older all parameters decreased with age in an almost linear fashion with an annual change ranging from 0.7% to 0.9%. Our results for an unselected German female cohort indicate that DXR is a reliable, widely available osteodensitometric technique based on the refinement of conventional radiogrammetry. These findings are comparable to those from other studies and represent a valid resource for clinical application and for comparisons with other ethnic groups. (orig.)

Trends in Female Breast Cancer by Age Group in the Chiang

Science.gov (United States)

Sripan, Patumrat; Sriplung, Hutcha; Pongnikorn, Donsuk; Virani, Shama; Bilheem, Surichai; Chaisaengkhaum, Udomlak; Maneesai, Puttachart; Waisri, Narate; Hanpragopsuk, Chirapong; Tansiri, Panrada; Khamsan, Varunee; Poungsombat, Malisa; Mawoot, Aumnart; Chitapanarux, Imjai

2017-05-01

Objectives: This study was conducted to determine incidence trends of female breast cancer according to age groups and to predict future change in Chiang Mai women through 2028. Method: Data were collected from all hospitals in Chiang Mai in northern Thailand, from 1989 through 2013, and used to investigate effects of age, year of diagnosis (period) and year of birth (cohort) on female breast cancer incidences using an age-period-cohort model. This model features geometric cut trends to predict change by young (<40 years), middle-aged (40-59) and elderly (≥60) age groups. Result: Of 5, 417 female breast cancer patients with a median age of 50 years (interquartile range: 43 to 59 years), 15%, 61% and 24% were young, middle-aged and elderly, respectively. Seventy nine percent of cancer cases in this study were detected at advanced stage. The trend in stage classification showed an increase in percentage of early stage and a decrease in metastatic cancers. Linear trends for cohort and period were not found in young females but were observed in middle-aged and elderly groups. Age-standardized rates (ASR) can be expected to remain stable around 6.8 per 100,000 women-years in young females. In the other age groups, the ASR trends were calculated to increase and reach peaks in 2024 of 120.2 and 138.2 per 100,000 women-years, respectively. Conclusion: Cohort effects or generation-specific effects, such as life style factors and the year of diagnosis (period) might have impacted on increased incidence in women aged over 40 years but not those under 40 years. A budget should be provided for treatment facilities and strategies to detect early stage cancers. The cost effectiveness of screening measures i.e. mammographic screening may need to be reconsidered for women age over 40 years. Creative Commons Attribution License

Age at exposure and attained age variations of cancer risk in the Japanese A-bomb and radiotherapy cohorts

Energy Technology Data Exchange (ETDEWEB)

Schneider, Uwe, E-mail: uwe.schneider@uzh.ch [Institute of Physics, Science Faculty, University of Zürich, Zürich 8057, Switzerland and Radiotherapy Hirslanden, Uwe Schneider Institute of Radiotherapy, Witellikerstr. 40, Zürich 8032 (Switzerland); Walsh, Linda [Institute of Physics, Science Faculty, University of Zürich, Zürich 8057, Switzerland and BfS - Federal Office for Radiation Protection, Radiation Protection and Health, Neuherberg 85764 (Germany)

2015-08-15

Purpose: Phenomenological risk models for radiation-induced cancer are frequently applied to estimate the risk of radiation-induced cancers at radiotherapy doses. Such models often include the effect modification, of the main risk to radiation dose response, by age at exposure and attained age. The aim of this paper is to compare the patterns in risk effect modification by age, between models obtained from the Japanese atomic-bomb (A-bomb) survivor data and models for cancer risks previously reported for radiotherapy patients. Patterns in risk effect modification by age from the epidemiological studies of radiotherapy patients were also used to refine and extend the risk effect modification by age obtained from the A-bomb survivor data, so that more universal models can be presented here. Methods: Simple log-linear and power functions of age for the risk effect modification applied in models of the A-bomb survivor data are compared to risks from epidemiological studies of second cancers after radiotherapy. These functions of age were also refined and fitted to radiotherapy risks. The resulting age models provide a refined and extended functional dependence of risk with age at exposure and attained age especially beyond 40 and 65 yr, respectively, and provide a better representation than the currently available simple age functions. Results: It was found that the A-bomb models predict risk similarly to the outcomes of testicular cancer survivors. The survivors of Hodgkin’s disease show steeper variations of risk with both age at exposure and attained age. The extended models predict solid cancer risk increase as a function of age at exposure beyond 40 yr and the risk decrease as a function of attained age beyond 65 yr better than the simple models. Conclusions: The standard functions for risk effect modification by age, based on the A-bomb survivor data, predict second cancer risk in radiotherapy patients for ages at exposure prior to 40 yr and attained ages

Periodic motions and grazing in a harmonically forced, piecewise, linear oscillator with impacts

International Nuclear Information System (INIS)

Luo, Albert C.J.; Chen Lidi

2005-01-01

In this paper, an idealized, piecewise linear system is presented to model the vibration of gear transmission systems. Periodic motions in a generalized, piecewise linear oscillator with perfectly plastic impacts are predicted analytically. The analytical predictions of periodic motion are based on the mapping structures, and the generic mappings based on the discontinuous boundaries are developed. This method for the analytical prediction of the periodic motions in non-smooth dynamic systems can give all possible periodic motions based on the adequate mapping structures. The stability and bifurcation conditions for specified periodic motions are obtained. The periodic motions and grazing motion are demonstrated. This model is applicable to prediction of periodic motion in nonlinear dynamics of gear transmission systems

Comprehensive Analysis of Large Sets of Age-Related Physiological Indicators Reveals Rapid Aging around the Age of 55 Years.

Science.gov (United States)

Lixie, Erin; Edgeworth, Jameson; Shamir, Lior

2015-01-01

While many studies show a correlation between chronological age and physiological indicators, the nature of this correlation is not fully understood. To perform a comprehensive analysis of the correlation between chronological age and age-related physiological indicators. Physiological aging scores were deduced using principal component analysis from a large dataset of 1,227 variables measured in a cohort of 4,796 human subjects, and the correlation between the physiological aging scores and chronological age was assessed. Physiological age does not progress linearly or exponentially with chronological age: a more rapid physiological change is observed around the age of 55 years, followed by a mild decline until around the age of 70 years. These findings provide evidence that the progression of physiological age is not linear with that of chronological age, and that periods of mild change in physiological age are separated by periods of more rapid aging. © 2015 S. Karger AG, Basel.

Trends in Female Breast Cancer by Age Group in the Chiang Mai Population

Science.gov (United States)

Sripan, Patumrat; Sriplung, Hutcha; Pongnikorn, Donsuk; Virani, Shama; Bilheem, Surichai; Chaisaengkhaum, Udomlak; Maneesai, Puttachart; Waisri, Narate; Hanpragopsuk, Chirapong; Tansiri, Panrada; Khamsan, Varunee; Poungsombat, Malisa; Mawoot, Aumnart; Chitapanarux, Imjai

2017-01-01

Objectives: This study was conducted to determine incidence trends of female breast cancer according to age groups and to predict future change in Chiang Mai women through 2028. Method: Data were collected from all hospitals in Chiang Mai in northern Thailand, from 1989 through 2013, and used to investigate effects of age, year of diagnosis (period) and year of birth (cohort) on female breast cancer incidences using an age-period-cohort model. This model features geometric cut trends to predict change by young (<40 years), middle-aged (40-59) and elderly (≥60) age groups. Result: Of 5, 417 female breast cancer patients with a median age of 50 years (interquartile range: 43 to 59 years), 15%, 61% and 24% were young, middle-aged and elderly, respectively. Seventy nine percent of cancer cases in this study were detected at advanced stage. The trend in stage classification showed an increase in percentage of early stage and a decrease in metastatic cancers. Linear trends for cohort and period were not found in young females but were observed in middle-aged and elderly groups. Age-standardized rates (ASR) can be expected to remain stable around 6.8 per 100,000 women-years in young females. In the other age groups, the ASR trends were calculated to increase and reach peaks in 2024 of 120.2 and 138.2 per 100,000 women-years, respectively. Conclusion: Cohort effects or generation-specific effects, such as life style factors and the year of diagnosis (period) might have impacted on increased incidence in women aged over 40 years but not those under 40 years. A budget should be provided for treatment facilities and strategies to detect early stage cancers. The cost effectiveness of screening measures i.e. mammographic screening may need to be reconsidered for women age over 40 years. PMID:28612595

Effects of socioeconomic position and social mobility on linear growth from early childhood until adolescence.

Science.gov (United States)

Muraro, Ana Paula; Souza, Rita Adriana Gomes de; Rodrigues, Paulo Rogério Melo; Ferreira, Márcia Gonçalves; Sichieri, Rosely

2017-01-01

To assess the effect of socioeconomic position (SEP) in childhood and social mobility on linear growth through adolescence in a population-based cohort. Children born in Cuiabá-MT, central-western Brazil, were evaluated during 1994 - 1999. They were first assessed during 1999 - 2000 (0 - 5 years) and again during 2009 - 2011 (10 - 17 years), and their height-for-age was evaluated during these two periods.Awealth index was used to classify the SEP of each child's family as low, medium, or high. Social mobility was categorized as upward mobility or no upward mobility. Linear mixed models were used. We evaluated 1,716 children (71.4% of baseline) after 10 years, and 60.6% of the families showed upward mobility, with a higher percentage among the lowest economic classes. A higher height-for-age was also observed among those from families with a high SEP both in childhood (low SEP= -0.35 z-score; high SEP= 0.15 z-score, p childhood and social mobility did not greatly influence linear growth through childhood in this central-western Brazilian cohort.

Genetic evaluation of calf and heifer survival in Iranian Holstein cattle using linear and threshold models.

Science.gov (United States)

Forutan, M; Ansari Mahyari, S; Sargolzaei, M

2015-02-01

Calf and heifer survival are important traits in dairy cattle affecting profitability. This study was carried out to estimate genetic parameters of survival traits in female calves at different age periods, until nearly the first calving. Records of 49,583 female calves born during 1998 and 2009 were considered in five age periods as days 1-30, 31-180, 181-365, 366-760 and full period (day 1-760). Genetic components were estimated based on linear and threshold sire models and linear animal models. The models included both fixed effects (month of birth, dam's parity number, calving ease and twin/single) and random effects (herd-year, genetic effect of sire or animal and residual). Rates of death were 2.21, 3.37, 1.97, 4.14 and 12.4% for the above periods, respectively. Heritability estimates were very low ranging from 0.48 to 3.04, 0.62 to 3.51 and 0.50 to 4.24% for linear sire model, animal model and threshold sire model, respectively. Rank correlations between random effects of sires obtained with linear and threshold sire models and with linear animal and sire models were 0.82-0.95 and 0.61-0.83, respectively. The estimated genetic correlations between the five different periods were moderate and only significant for 31-180 and 181-365 (r(g) = 0.59), 31-180 and 366-760 (r(g) = 0.52), and 181-365 and 366-760 (r(g) = 0.42). The low genetic correlations in current study would suggest that survival at different periods may be affected by the same genes with different expression or by different genes. Even though the additive genetic variations of survival traits were small, it might be possible to improve these traits by traditional or genomic selection. © 2014 Blackwell Verlag GmbH.

Doubly Periodic Traveling Waves in a Cellular Neural Network with Linear Reaction

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Lin JianJhong

2009-01-01

Full Text Available Szekeley observed that the dynamic pattern of the locomotion of salamanders can be explained by periodic vector sequences generated by logical neural networks. Such sequences can mathematically be described by "doubly periodic traveling waves" and therefore it is of interest to propose dynamic models that may produce such waves. One such dynamic network model is built here based on reaction-diffusion principles and a complete discussion is given for the existence of doubly periodic waves as outputs. Since there are 2 parameters in our model and 4 a priori unknown parameters involved in our search of solutions, our results are nontrivial. The reaction term in our model is a linear function and hence our results can also be interpreted as existence criteria for solutions of a nontrivial linear problem depending on 6 parameters.

Influence of birth cohort on age of onset cluster analysis in bipolar I disorder

DEFF Research Database (Denmark)

Bauer, M; Glenn, T; Alda, M

2015-01-01

Purpose: Two common approaches to identify subgroups of patients with bipolar disorder are clustering methodology (mixture analysis) based on the age of onset, and a birth cohort analysis. This study investigates if a birth cohort effect will influence the results of clustering on the age of onset...... cohort. Model-based clustering (mixture analysis) was then performed on the age of onset data using the residuals. Clinical variables in subgroups were compared. Results: There was a strong birth cohort effect. Without adjusting for the birth cohort, three subgroups were found by clustering. After...... on the age of onset, and that there is a birth cohort effect. Including the birth cohort adjustment altered the number and characteristics of subgroups detected when clustering by age of onset. Further investigation is needed to determine if combining both approaches will identify subgroups that are more...

COHORT EFFECTS OF SUICIDE MORTALITY ARE SEX SPECIFIC IN THE RAPIDLY DEVELOPED HONG KONG CHINESE POPULATION, 1976-2010.

Science.gov (United States)

Chung, Roger Y; Yip, Benjamin H K; Chan, Sandra S M; Wong, Samuel Y S

2016-06-01

To examine temporal variations of age, period, and cohort on suicide mortality rate in Hong Kong (HK) from 1976 to 2010, and speculate the macroenvironmental mechanisms of the observed trends. Poisson age-period-cohort modeling was used to delineate the effects of age, period, and cohort on suicide mortality. Analysis by sex was also conducted to examine if gender difference exists for suicidal behaviours. Age-cohort model provides the best fit to the mortality data, implying that the cohort effect is likely to explain more of the contributions to HK's suicide mortality pattern than the period effect. Risk of suicide mortality increases nonlinearly with age and accelerates after age 65-69 for both sexes. Moreover, the cohort effects differ between the sexes-risk of mortality increases continually for men born after 1961, but no change is observed for women since the 1941 cohort. With increased risk of suicide mortality in younger cohorts and the age effect of suicide mortality, we may see future increase in suicide mortality as these younger cohorts age. Further studies are needed to clarify plausible associations between broader sociohistorical changes in the population impacting psychological risk factors and suicidal behaviour to better inform suicide prevention strategies. © 2015 Wiley Periodicals, Inc.

Uneven transitions: Period- and cohort-related changes in gender attitudes in China, 1995-2007.

Science.gov (United States)

Shu, Xiaoling; Zhu, Yifei

2012-09-01

This paper analyzes temporal variations in two gender attitudes in China: beliefs about gender equality and perspectives on women's combined work and family roles. It uses the most currently available population series from the 1995, 2001 and 2007 World Value Surveys of 4500 respondents and a series of multilevel cross-classified models to properly estimate period and cohort effects. Attitudes toward women's dual roles manifest neither period nor cohort effects; the population displays a universal high level of acceptance of women's paid employment. Orientations toward gender equality manifest both cohort and period effects: members of the youngest cohort of both sexes hold the most liberal attitudes; the positive effect of college education has increased over time. Attitude toward gender equality in China displays neither a shift toward conservatism nor an over-time trend toward egalitarianism in 1995-2007, a time of rapid economic growth. Copyright © 2012 Elsevier Inc. All rights reserved.

Comparison of robustness to outliers between robust poisson models and log-binomial models when estimating relative risks for common binary outcomes: a simulation study.

Science.gov (United States)

Chen, Wansu; Shi, Jiaxiao; Qian, Lei; Azen, Stanley P

2014-06-26

To estimate relative risks or risk ratios for common binary outcomes, the most popular model-based methods are the robust (also known as modified) Poisson and the log-binomial regression. Of the two methods, it is believed that the log-binomial regression yields more efficient estimators because it is maximum likelihood based, while the robust Poisson model may be less affected by outliers. Evidence to support the robustness of robust Poisson models in comparison with log-binomial models is very limited. In this study a simulation was conducted to evaluate the performance of the two methods in several scenarios where outliers existed. The findings indicate that for data coming from a population where the relationship between the outcome and the covariate was in a simple form (e.g. log-linear), the two models yielded comparable biases and mean square errors. However, if the true relationship contained a higher order term, the robust Poisson models consistently outperformed the log-binomial models even when the level of contamination is low. The robust Poisson models are more robust (or less sensitive) to outliers compared to the log-binomial models when estimating relative risks or risk ratios for common binary outcomes. Users should be aware of the limitations when choosing appropriate models to estimate relative risks or risk ratios.

Cohort Differences in Received Social Support in Later Life: The Role of Network Type.

Science.gov (United States)

Suanet, Bianca; Antonucci, Toni C

2017-07-01

The objective is to assess cohort differences in received emotional and instrumental support in relation to network types. The main guiding hypothesis is that due to increased salience of non-kin with recent social change, those in friend-focused and diverse network types receive more support in later birth cohorts than earlier birth cohorts. Data from the Longitudinal Aging Study Amsterdam are employed. We investigate cohort differences in total received emotional and instrumental support in a series of linear regression models comparing birth cohorts aged 55-64, 65-74, 75-84, and 85-94 across three time periods (1992, 2002, and 2012). Four network types (friend, family, restricted, and diverse) are identified. Friend-focused networks are more common in later birth cohorts, restrictive networks less common. Those in friend-focused networks in later cohorts report receiving more emotional and instrumental support. No differences in received support are evident upon diverse networks. The increased salience of non-kin is reflected in an increase in received emotional and instrumental support in friend-focused networks in later birth cohorts. The preponderance of non-kin in networks should not be perceived as a deficit model for social relationships as restrictive networks are declining across birth cohorts. © The Author 2016. Published by Oxford University Press on behalf of The Gerontological Society of America. All rights reserved. For permissions, please e-mail: journals.permissions@oup.com.

Cohort profile: the lidA Cohort Study-a German Cohort Study on Work, Age, Health and Work Participation.

Science.gov (United States)

Hasselhorn, Hans Martin; Peter, Richard; Rauch, Angela; Schröder, Helmut; Swart, Enno; Bender, Stefan; du Prel, Jean-Baptist; Ebener, Melanie; March, Stefanie; Trappmann, Mark; Steinwede, Jacob; Müller, Bernd Hans

2014-12-01

The lidA Cohort Study (German Cohort Study on Work, Age, Health and Work Participation) was set up to investigate and follow the effects of work and work context on the physical and psychological health of the ageing workforce in Germany and subsequently on work participation. Cohort participants are initially employed people subject to social security contributions and born in either 1959 (n = 2909) or 1965 (n = 3676). They were personally interviewed in their homes in 2011 and will be visited every 3 years. Data collection comprises socio-demographic data, work and private exposures, work ability, work and work participation attitudes, health, health-related behaviour, personality and attitudinal indicators. Employment biographies are assessed using register data. Subjective health reports and physical strength measures are complemented by health insurance claims data, where permission was given. A conceptual framework has been developed for the lidA Cohort Study within which three confirmatory sub-models assess the interdependencies of work and health considering age, gender and socioeconomic status. The first set of the data will be available to the scientific community by 2015. Access will be given by the Research Data Centre of the German Federal Employment Agency at the Institute for Employment Research (http://fdz.iab.de/en.aspx). © The Author 2014. Published by Oxford University Press on behalf of the International Epidemiological Association.

Practical likelihood analysis for spatial generalized linear mixed models

DEFF Research Database (Denmark)

Bonat, W. H.; Ribeiro, Paulo Justiniano

2016-01-01

We investigate an algorithm for maximum likelihood estimation of spatial generalized linear mixed models based on the Laplace approximation. We compare our algorithm with a set of alternative approaches for two datasets from the literature. The Rhizoctonia root rot and the Rongelap are......, respectively, examples of binomial and count datasets modeled by spatial generalized linear mixed models. Our results show that the Laplace approximation provides similar estimates to Markov Chain Monte Carlo likelihood, Monte Carlo expectation maximization, and modified Laplace approximation. Some advantages...... of Laplace approximation include the computation of the maximized log-likelihood value, which can be used for model selection and tests, and the possibility to obtain realistic confidence intervals for model parameters based on profile likelihoods. The Laplace approximation also avoids the tuning...

Non-linear relationship between maternal work hours and child body weight: Evidence from the Western Australian Pregnancy Cohort (Raine) Study.

Science.gov (United States)

Li, Jianghong; Akaliyski, Plamen; Schäfer, Jakob; Kendall, Garth; Oddy, Wendy H; Stanley, Fiona; Strazdins, Lyndall

2017-08-01

Using longitudinal data from the Western Australia Pregnancy Cohort (Raine) Study and both random-effects and fixed-effects models, this study examined the connection between maternal work hours and child overweight or obesity. Following children in two-parent families from early childhood to early adolescence, multivariate analyses revealed a non-linear and developmentally dynamic relationship. Among preschool children (ages 2 to 5), we found lower likelihood of child overweight and obesity when mothers worked 24 h or less per week, compared to when mothers worked 35 or more hours. This effect was stronger in low-to-medium income families. For older children (ages 8 to 14), compared to working 35-40 h a week, working shorter hours (1-24, 25-34) or longer hours (41 or more) was both associated with increases in child overweight and obesity. These non-linear effects were more pronounced in low-to-medium income families, particularly when fathers also worked long hours. Copyright © 2017 Elsevier Ltd. All rights reserved.

A versatile curve-fit model for linear to deeply concave rank abundance curves

NARCIS (Netherlands)

Neuteboom, J.H.; Struik, P.C.

2005-01-01

A new, flexible curve-fit model for linear to concave rank abundance curves was conceptualized and validated using observational data. The model links the geometric-series model and log-series model and can also fit deeply concave rank abundance curves. The model is based ¿ in an unconventional way

Periodic linear differential stochastic processes

NARCIS (Netherlands)

Kwakernaak, H.

1975-01-01

Periodic linear differential processes are defined and their properties are analyzed. Equivalent representations are discussed, and the solutions of related optimal estimation problems are given. An extension is presented of Kailath and Geesey’s [1] results concerning the innovations representation

Reducing Monte Carlo error in the Bayesian estimation of risk ratios using log-binomial regression models.

Science.gov (United States)

Salmerón, Diego; Cano, Juan A; Chirlaque, María D

2015-08-30

In cohort studies, binary outcomes are very often analyzed by logistic regression. However, it is well known that when the goal is to estimate a risk ratio, the logistic regression is inappropriate if the outcome is common. In these cases, a log-binomial regression model is preferable. On the other hand, the estimation of the regression coefficients of the log-binomial model is difficult owing to the constraints that must be imposed on these coefficients. Bayesian methods allow a straightforward approach for log-binomial regression models and produce smaller mean squared errors in the estimation of risk ratios than the frequentist methods, and the posterior inferences can be obtained using the software WinBUGS. However, Markov chain Monte Carlo methods implemented in WinBUGS can lead to large Monte Carlo errors in the approximations to the posterior inferences because they produce correlated simulations, and the accuracy of the approximations are inversely related to this correlation. To reduce correlation and to improve accuracy, we propose a reparameterization based on a Poisson model and a sampling algorithm coded in R. Copyright © 2015 John Wiley & Sons, Ltd.

Cohort difference in age-related trajectories in network size in old age: are networks expanding?

NARCIS (Netherlands)

Suanet, B.; Huxhold, O.

2018-01-01

Objectives. Contemporary societal views on old age as well as a rise in retirement age raise the question whether patterns of stability and/or decline in network size as found in earlier studies similarly apply to later birth cohorts of older adults. Methods. Change score models are estimated to

Monte Carlo Numerical Models for Nuclear Logging Applications

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Fusheng Li

2012-06-01

Full Text Available Nuclear logging is one of most important logging services provided by many oil service companies. The main parameters of interest are formation porosity, bulk density, and natural radiation. Other services are also provided from using complex nuclear logging tools, such as formation lithology/mineralogy, etc. Some parameters can be measured by using neutron logging tools and some can only be measured by using a gamma ray tool. To understand the response of nuclear logging tools, the neutron transport/diffusion theory and photon diffusion theory are needed. Unfortunately, for most cases there are no analytical answers if complex tool geometry is involved. For many years, Monte Carlo numerical models have been used by nuclear scientists in the well logging industry to address these challenges. The models have been widely employed in the optimization of nuclear logging tool design, and the development of interpretation methods for nuclear logs. They have also been used to predict the response of nuclear logging systems for forward simulation problems. In this case, the system parameters including geometry, materials and nuclear sources, etc., are pre-defined and the transportation and interactions of nuclear particles (such as neutrons, photons and/or electrons in the regions of interest are simulated according to detailed nuclear physics theory and their nuclear cross-section data (probability of interacting. Then the deposited energies of particles entering the detectors are recorded and tallied and the tool responses to such a scenario are generated. A general-purpose code named Monte Carlo N– Particle (MCNP has been the industry-standard for some time. In this paper, we briefly introduce the fundamental principles of Monte Carlo numerical modeling and review the physics of MCNP. Some of the latest developments of Monte Carlo Models are also reviewed. A variety of examples are presented to illustrate the uses of Monte Carlo numerical models

The incidence of injuries in young people: II. Log-linear multivariable models for risk factors in a collaborative study in Brazil, Chile, Cuba and Venezuela.

Science.gov (United States)

Bangdiwala, S I; Anzola-Pérez, E

1990-03-01

Injuries and accidents are acknowledged as leading causes of morbidity and mortality among children and adolescents in the developing countries of the world. The Pan American Health Organization sponsored a collaborative study in four selected countries in Latin America to study the extent of the problem as well as to examine the potential risk factors associated with selected non-fatal injuries in the countries. The study subjects were injured children and adolescents (0-19 years of age) presenting at the study hospitals in chosen urban centres, as well as injured that were surveyed in households in the catchment areas of the hospitals. Study methods and descriptive frequency results were presented earlier. In this paper, log-linear multivariate regression models are used to examine the potentiating effects within country of several measured variables on specific types of injuries. The significance of risk factors varied between countries; however, some general patterns emerged. Falls were more likely in younger children, and occurred at home. The main risk factor for home accidents was the age of the child. The education of the head of the household was an important risk factor for the type of injury suffered. The likelihood of traffic accident injury varied with time of day and day of the week, but also was more likely in higher educated households. The results found are consistent with those found in other studies in the developed world and suggest specific areas of concern for health planners to address.

Risk of lower extremity arterial disease in a cohort of workers occupationally exposed to ionizing radiation over a prolonged period

Energy Technology Data Exchange (ETDEWEB)

Azizova, Tamara V.; Bannikova, Maria V.; Grigorieva, Evgenia S.; Bagaeva, Yaroslava P.; Azizova, Elena V. [Southern Urals Biophysics Institute, Ozyorsk Chelyabinsk Region (Russian Federation)

2016-05-15

In this study the incidence risk of lower extremity arterial disease (LEAD; international classification of diseases version 9 code 440.2) was assessed in a cohort of workers occupationally exposed to radiation over a prolonged period. The study cohort includes 22,377 workers of the Mayak Production Association (25 % of whom are females) first employed at one of the main facilities in 1948-1982 and followed up to the end of 2008. Dose estimates used in the study are provided by Mayak Worker Dosimetry System 2008. The mean total dose from external gamma-rays is 0.54 Gy for males and 0.44 Gy for females. The mean absorbed liver dose from internal alpha-radiation due to incorporated plutonium is 0.23 Gy in males and 0.44 Gy in females. Relative risks and excess relative risks per unit dose (ERR/Gy) are calculated based on maximum likelihood. A total of 943 cases of LEAD are registered in the study cohort during the follow-up of 512,801 person-years. A significant association of LEAD incidence with total dose from external gamma-rays (based on a linear model) was revealed, and the ERR/Gy is 0.27 (95 % confidence interval (CI) 0.11; 0.48). It turned out that a linear-exponential model provides a better fit of the data (∇AIC = 9.957). Inclusion of an adjustment for internal alpha-radiation dose resulted in the reduction of the ERR/Gy to 0.19 (95 % CI 0.05; 0.39), but the risk remains significant. No association of LEAD incidence with dose from internal alpha-radiation was found in the study worker cohort. It is concluded that this study provides evidence for an association of LEAD incidence with dose from external gamma-rays taking non-radiation factors into account. (orig.)

The Lothian Birth Cohort 1936: a study to examine influences on cognitive ageing from age 11 to age 70 and beyond

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Whalley Lawrence J

2007-12-01

Full Text Available Abstract Background Cognitive ageing is a major burden for society and a major influence in lowering people's independence and quality of life. It is the most feared aspect of ageing. There are large individual differences in age-related cognitive changes. Seeking the determinants of cognitive ageing is a research priority. A limitation of many studies is the lack of a sufficiently long period between cognitive assessments to examine determinants. Here, the aim is to examine influences on cognitive ageing between childhood and old age. Methods/Design The study is designed as a follow-up cohort study. The participants comprise surviving members of the Scottish Mental Survey of 1947 (SMS1947; N = 70,805 who reside in the Edinburgh area (Lothian of Scotland. The SMS1947 applied a valid test of general intelligence to all children born in 1936 and attending Scottish schools in June 1947. A total of 1091 participants make up the Lothian Birth Cohort 1936. They undertook: a medical interview and examination; physical fitness testing; extensive cognitive testing (reasoning, memory, speed of information processing, and executive function; personality, quality of life and other psycho-social questionnaires; and a food frequency questionnaire. They have taken the same mental ability test (the Moray House Test No. 12 at age 11 and age 70. They provided blood samples for DNA extraction and testing and other biomarker analyses. Here we describe the background and aims of the study, the recruitment procedures and details of numbers tested, and the details of all examinations. Discussion The principal strength of this cohort is the rarely captured phenotype of lifetime cognitive change. There is additional rich information to examine the determinants of individual differences in this lifetime cognitive change. This protocol report is important in alerting other researchers to the data available in the cohort.

Effects of combined linear and nonlinear periodic training on physical fitness and competition times in finswimmers.

Science.gov (United States)

Yu, Kyung-Hun; Suk, Min-Hwa; Kang, Shin-Woo; Shin, Yun-A

2014-10-01

The purpose of this study was to investigate the effect of combined linear and nonlinear periodic training on physical fitness and competition times in finswimmers. The linear resistance training model (6 days/week) and nonlinear underwater training (4 days/week) were applied to 12 finswimmers (age, 16.08± 1.44 yr; career, 3.78± 1.90 yr) for 12 weeks. Body composition measures included weight, body mass index (BMI), percent fat, and fat-free mass. Physical fitness measures included trunk flexion forward, trunk extension backward, sargent jump, 1-repetition-maximum (1 RM) squat, 1 RM dead lift, knee extension, knee flexion, trunk extension, trunk flexion, and competition times. Body composition and physical fitness were improved after the 12-week periodic training program. Weight, BMI, and percent fat were significantly decreased, and trunk flexion forward, trunk extension backward, sargent jump, 1 RM squat, 1 RM dead lift, and knee extension (right) were significantly increased. The 50- and 100-m times significantly decreased in all 12 athletes. After 12 weeks of training, all finswimmers who participated in this study improved their times in a public competition. These data indicate that combined linear and nonlinear periodic training enhanced the physical fitness and competition times in finswimmers.

Ajuste de modelos estocásticos lineares e não-lineares para a descrição do perfil longitudinal de árvores Fitting linear and nonlinear stochastic models to describe longitudinal tree profile

Directory of Open Access Journals (Sweden)

Leonardo Machado Pires

2007-10-01

Full Text Available Os modelos polinomiais são mais difundidos no meio florestal brasileiro na descrição do perfil de árvores devido à sua facilidade de ajuste e precisão. O mesmo não ocorre com os modelos não-lineares, os quais possuem maior dificuldade de ajuste. Dentre os modelos não-lineares clássicos, na descrição do perfil, podem-se citar o de Gompertz, o Logístico e o de Weibull. Portanto, este estudo visou comparar os modelos lineares e não lineares para a descrição do perfil de árvores. As medidas de comparação foram o coeficiente de determinação (R², o erro-padrão residual (s yx, o coeficiente de determinação corrigido (R²ajustado, o gráfico dos resíduos e a facilidade de ajuste. Os resultados ressaltaram que, dentre os modelos não-lineares, o que obteve melhor desempenho, de forma geral, foi o modelo Logístico, apesar de o modelo de Gompertz ser melhor em termos de erro-padrão residual. Nos modelos lineares, o polinômio proposto por Pires & Calegario foi superior aos demais. Ao comparar os modelos não-lineares com os lineares, o modelo Logístico foi melhor em razão, principalmente, do fato de o comportamento dos dados ser não-linear, à baixa correlação entre os parâmetros e à fácil interpretação deles, facilitando a convergência e o ajuste.Polynomial models are most commonly used in Brazilian forestry for taper modeling due to its straightforwardly fitting and precision. The use of nonlinear regression classic models, like Gompertz, Logistic and Weibull, is not very common in Brazil. Therefore, this study aimed to verify the best nonlinear and linear models, and among these the best model to describe the longitudinal tree profile. The comparison measures were: R², syx, R²adjusted, residual graphics and fitting convergence. The results pointed out that among the non-linear models the best behavior, in general, was given by the Logistic model, although the Gompertz model was superior compared with the Weibull

Cohort change and the diffusion of environmental concern: A cross-national analysis.

Science.gov (United States)

Nawrotzki, Raphael J; Pampel, Fred C

2013-09-01

This study explores value change across cohorts for a multinational population sample. Employing a diffusion-of-innovations approach, we combine competing theories predicting the relationship between socio-economic status (SES) and environmentalism: post-materialism and affluence theories, and global environmentalism theory. The diffusion argument suggests that high-SES groups first adopt pro-environmental views, but as time passes by, environmentalism diffuses to lower-SES groups. We test the diffusion argument using a sample of 18 countries for two waves (years 1993 and 2000) from the International Social Survey Project (ISSP). Cross-classified multilevel modeling allows us to identify a non-linear interaction between cohort and education, our core measure of SES, in predicting environmental concern, while controlling for age and period. We find support for the diffusion argument and demonstrate that the positive effect of education on environmental concern first increases among older cohorts, then starts to level off until a bend-point is reached for individuals born around 1940 and becomes progressively weaker for younger cohorts.

The role of under-employment and unemployment in recent birth cohort effects in Australian suicide.

Science.gov (United States)

Page, Andrew; Milner, Allison; Morrell, Stephen; Taylor, Richard

2013-09-01

High suicide rates evident in Australian young adults during an epidemic period in the 1990s appear to have been sustained in older age-groups in the subsequent decade. This period also coincides with changes in employment patterns in Australia. This study investigates age, period, and birth cohort effects in Australian suicide over the 20th century, with particular reference to the period subsequent to the 1990s youth suicide epidemic in young males. Period- and cohort-specific trends in suicide were examined for 1907-2010 based on descriptive analysis of age-specific suicide rates and a series of age-period-cohort (APC) models using Poisson regression. Under-employment rates (those employed part-time seeking additional hours of work) and unemployment rates (those currently seeking employment) for the latter part of this time series (1978-2010) were also examined and compared with period- and cohort-specific trends in suicide. A significant increasing birth cohort effect in male suicide rates was evident in birth cohorts born after 1970-74, after adjusting for the effects age and period. An increasing birth cohort effect was also evident in female suicide rates, but was of a lesser magnitude. Increases in male cohort-specific suicide rates were significantly correlated with increases in cohort-specific under-employment and unemployment rates. Birth cohorts that experienced the peak of the suicide epidemic during the 1990s have continued to have higher suicide rates than cohorts born in earlier epochs. This increase coincides with changes to a labour force characterised by greater 'flexibility' and 'casualised' employment, especially in younger aged cohorts. Copyright © 2013 Elsevier Ltd. All rights reserved.

Green space and cognitive ageing: A retrospective life course analysis in the Lothian Birth Cohort 1936.

Science.gov (United States)

Cherrie, Mark P C; Shortt, Niamh K; Mitchell, Richard J; Taylor, Adele M; Redmond, Paul; Thompson, Catharine Ward; Starr, John M; Deary, Ian J; Pearce, Jamie R

2018-01-01

International evidence suggests that green space has beneficial effects on general and mental health but little is known about how lifetime exposure to green space influences cognitive ageing. Employing a novel longitudinal life course approach, we examined the association between lifetime availability of public parks and cognitive ageing. Lifetime residential information was gathered from the participants of the Lothian Birth Cohort 1936 using a "life-grid" questionnaire at age 78 years. Parks information from 1949, 1969 and 2009 was used to determine a percentage of parks within a 1500 m buffer zone surrounding residence for childhood, adulthood, and later adulthood periods. Linear regressions were undertaken to test for association with age-standardised, residualised change in cognitive function (Moray House Test score) from age 11 to 70 years, and from age 70 to 76 (n = 281). The most appropriate model was selected using the results of a partial F-test, and then stratified by demographic, genetic and socioeconomic factors. The local provision of park space in childhood and adulthood were both important in explaining the change in cognitive function in later life. The association between childhood and adulthood park availability and change in the Moray House Test Score from age 70 to 76 was strongest for women, those without an APOE e4 allele (a genetic risk factor), and those in the lowest socioeconomic groups. Greater neighbourhood provision of public parks from childhood through to adulthood may help to slow down the rate of cognitive decline in later life, recognising that such environmental associations are always sensitive to individual characteristics. Copyright © 2017 The Authors. Published by Elsevier Ltd.. All rights reserved.

Age and fecundability in a North American preconception cohort study.

Science.gov (United States)

Wesselink, Amelia K; Rothman, Kenneth J; Hatch, Elizabeth E; Mikkelsen, Ellen M; Sørensen, Henrik T; Wise, Lauren A

2017-12-01

There is a well-documented decline in fertility treatment success with increasing female age; however, there are few preconception cohort studies that have examined female age and natural fertility. In addition, data on male age and fertility are inconsistent. Given the increasing number of couples who are attempting conception at older ages, a more detailed characterization of age-related fecundability in the general population is of great clinical utility. The purpose of this study was to examine the association between female and male age with fecundability. We conducted a web-based preconception cohort study of pregnancy planners from the United States and Canada. Participants were enrolled between June 2013 and July 2017. Eligible participants were 21-45 years old (female) or ≥21 years old (male) and had not been using fertility treatments. Couples were followed until pregnancy or for up to 12 menstrual cycles. We analyzed data from 2962 couples who had been trying to conceive for ≤3 cycles at study entry and reported no history of infertility. We used life-table methods to estimate the unadjusted cumulative pregnancy proportion at 6 and 12 cycles by female and male age. We used proportional probabilities regression models to estimate fecundability ratios, the per-cycle probability of conception for each age category relative to the referent (21-24 years old), and 95% confidence intervals. Among female patients, the unadjusted cumulative pregnancy proportion at 6 cycles of attempt time ranged from 62.0% (age 28-30 years) to 27.6% (age 40-45 years); the cumulative pregnancy proportion at 12 cycles of attempt time ranged from 79.3% (age 25-27 years old) to 55.5% (age 40-45 years old). Similar patterns were observed among male patients, although differences between age groups were smaller. After adjusting for potential confounders, we observed a nearly monotonic decline in fecundability with increasing female age, with the exception of 28-33 years, at which

Age related neuromuscular changes in sEMG of m. Tibialis Anterior using higher order statistics (Gaussianity & linearity test).

Science.gov (United States)

Siddiqi, Ariba; Arjunan, Sridhar P; Kumar, Dinesh K

2016-08-01

Age-associated changes in the surface electromyogram (sEMG) of Tibialis Anterior (TA) muscle can be attributable to neuromuscular alterations that precede strength loss. We have used our sEMG model of the Tibialis Anterior to interpret the age-related changes and compared with the experimental sEMG. Eighteen young (20-30 years) and 18 older (60-85 years) performed isometric dorsiflexion at 6 different percentage levels of maximum voluntary contractions (MVC), and their sEMG from the TA muscle was recorded. Six different age-related changes in the neuromuscular system were simulated using the sEMG model at the same MVCs as the experiment. The maximal power of the spectrum, Gaussianity and Linearity Test Statistics were computed from the simulated and experimental sEMG. A correlation analysis at α=0.05 was performed between the simulated and experimental age-related change in the sEMG features. The results show the loss in motor units was distinguished by the Gaussianity and Linearity test statistics; while the maximal power of the PSD distinguished between the muscular factors. The simulated condition of 40% loss of motor units with halved the number of fast fibers best correlated with the age-related change observed in the experimental sEMG higher order statistical features. The simulated aging condition found by this study corresponds with the moderate motor unit remodelling and negligible strength loss reported in literature for the cohorts aged 60-70 years.

Changes in the use practitioner-based complementary and alternative medicine over time in Canada: Cohort and period effects.

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Mayilee Canizares

Full Text Available The use of complementary and alternative medicine (CAM is growing. However the factors contributing to changes over time and to birth cohort differences in CAM use are not well understood.We used data from 10186 participants, who were aged 20-69 years at the first cycle of data collection in the longitudinal component of the Canadian National Population Health Survey (1994/95-2010/11. We examined chiropractic and other practitioner-based CAM use with a focus on five birth cohorts: pre-World War II (born 1925-1934; World War II (born 1935-1944; older baby boomers (born 1945-1954; younger baby boomers (born 1955-1964; and Gen Xers (born 1965-1974. The survey collected data every two years on predisposing (e.g., sex, education, enabling (e.g., income, behavior-related factors (e.g., obesity, need (e.g., chronic conditions, and use of conventional care (primary care and specialists.The findings suggest that, at corresponding ages, more recent cohorts reported greater CAM (OR = 25.9, 95% CI: 20.0; 33.6 for Gen Xers vs. pre-World War and chiropractic use than their predecessors (OR = 2.2, 95% CI: 1.7; 2.8 for Gen Xers vs. pre-World War. There was also a secular trend of increasing CAM use, but not chiropractic use, over time (period effect across all ages. Factors associated with cohort differences were different for CAM and chiropractic use. Cohort differences in CAM use were partially related to a period effect of increasing CAM use over time across all ages while cohort differences in chiropractic use were related to the higher prevalence of chronic conditions among recent cohorts. The use of conventional care was positively related to greater CAM use (OR = 1.8, 95% CI: 1.6; 2.0 and chiropractic use (OR = 1.2, 95% CI: 1.1; 1.4 but did not contribute to changes over time or to cohort differences in CAM and chiropractic use.The higher CAM use over time and in recent cohorts could reflect how recent generations are approaching their healthcare needs

The Simulation and Experiment of a Non-Cross-Feeding Printed Log-Periodic Antenna

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Chun-Ying Kang

2015-01-01

Full Text Available A non-cross-fed printed log-periodic antenna is simulated and studied experimentally. To avoid complex feeding with long coaxial line, the non-cross-feeding structure is applied in this antenna. The software CST Microwave Studio is employed to simulate the proposed antenna, and the optimized antenna model is obtained. According to the simulation results, the antenna prototype is produced and measured. Simulation and measured results show that the antenna is with S11<-10 dB in band of 4.2–9.2 GHz. And the radiation pattern and gain vary steadily in this band, which achieves requirements for wideband antenna. This antenna design can be extended to the design of the antenna integrated in communication circuit.

Linear theory period ratios for surface helium enhanced double-mode Cepheids

International Nuclear Information System (INIS)

Cox, A.N.; Hodson, S.W.; King, D.S.

1979-01-01

Linear nonadiabatic theory period ratios for models of double-mode Cepheids with their two periods between 1 and 7 days have been computed, assuming differing amounts and depths of surface helium enhancement. Evolution theory masses and luminosities are found to be consistent with the observed periods. All models give Pi 1 /Pi 0 approx. =0.70 as observed for the 11 known variables, contrary to previous theoretical conclusions. The composition structure that best fits the period ratios has the helium mass fraction in the outer 10 -3 of the stellar mass (T< or =250,000 K) as 0.65, similar to a previous model for the triple-mode pulsator AC And. This enrichment can be established by a Cepheid wind and downward inverted μ gradient instability mixing in the lifetime of these low-mass classical Cepheids

Development of interpretation models for PFN uranium log analysis

International Nuclear Information System (INIS)

Barnard, R.W.

1980-11-01

This report presents the models for interpretation of borehole logs for the PFN (Prompt Fission Neutron) uranium logging system. Two models have been developed, the counts-ratio model and the counts/dieaway model. Both are empirically developed, but can be related to the theoretical bases for PFN analysis. The models try to correct for the effects of external factors (such as probe or formation parameters) in the calculation of uranium grade. The theoretical bases and calculational techniques for estimating uranium concentration from raw PFN data and other parameters are discussed. Examples and discussions of borehole logs are included

Periodic inventory system in cafeteria using linear programming

Science.gov (United States)

Usop, Mohd Fais; Ishak, Ruzana; Hamdan, Ahmad Ridhuan

2017-11-01

Inventory management is an important factor in running a business. It plays a big role of managing the stock in cafeteria. If the inventories are failed to be managed wisely, it will affect the profit of the cafeteria. Therefore, the purpose of this study is to find the solution of the inventory management in cafeteria. Most of the cafeteria in Malaysia did not manage their stock well. Therefore, this study is to propose a database system of inventory management and to develop the inventory model in cafeteria management. In this study, new database system to improve the management of the stock in a weekly basis will be provided using Linear Programming Model to get the optimal range of the inventory needed for selected categories. Data that were collected by using the Periodic Inventory System at the end of the week within three months period being analyzed by using the Food Stock-take Database. The inventory model was developed from the collected data according to the category of the inventory in the cafeteria. Results showed the effectiveness of using the Periodic Inventory System and will be very helpful to the cafeteria management in organizing the inventory. Moreover, the findings in this study can reduce the cost of operation and increased the profit.

Predictive models of forest logging residues of Triplochiton ...

African Journals Online (AJOL)

The model developed indicated that logarithmic functions performed better than other form of equation. The findings of this study revealed that there is significant logging residues left to waste in the forest after timber harvest and quantifying this logging residue in terms of biomass model can serve as management tools in ...

Age, Cohort and Co-Authorship

OpenAIRE

Hamermesh, Daniel S.

2015-01-01

The previously documented trend toward more co- and multi-authored research in economics is partly (perhaps 20 percent) due to different research styles of scholars in different birth cohorts (of different ages). Most of the trend reflects profession-wide changes in research style. Older scholars show greater variation in their research styles than younger ones, who use similar numbers of co-authors in each published paper; but there are no differences across cohorts in scholars’ willingness ...

Effects of socioeconomic position and social mobility on linear growth from early childhood until adolescence

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Ana Paula Muraro

Full Text Available ABSTRACT: Objective: To assess the effect of socioeconomic position (SEP in childhood and social mobility on linear growth through adolescence in a population-based cohort. Methods: Children born in Cuiabá-MT, central-western Brazil, were evaluated during 1994 - 1999. They were first assessed during 1999 - 2000 (0 - 5 years and again during 2009 - 2011 (10 - 17 years, and their height-for-age was evaluated during these two periods.Awealth index was used to classify the SEP of each child’s family as low, medium, or high. Social mobility was categorized as upward mobility or no upward mobility. Linear mixed models were used. Results: We evaluated 1,716 children (71.4% of baseline after 10 years, and 60.6% of the families showed upward mobility, with a higher percentage among the lowest economic classes. A higher height-for-age was also observed among those from families with a high SEP both in childhood (low SEP= -0.35 z-score; high SEP= 0.15 z-score, p < 0.01 and adolescence (low SEP= -0.01 z-score; high SEP= 0.45 z-score, p < 0.01, whereas upward mobility did not affect their linear growth. Conclusion: Expressive social mobility was observed, but SEP in childhood and social mobility did not greatly influence linear growth through childhood in this central-western Brazilian cohort.

Air Pollution and Cognitive Development at Age 7 in a Prospective Italian Birth Cohort.

Science.gov (United States)

Porta, Daniela; Narduzzi, Silvia; Badaloni, Chiara; Bucci, Simone; Cesaroni, Giulia; Colelli, Valentina; Davoli, Marina; Sunyer, Jordi; Zirro, Eleonora; Schwartz, Joel; Forastiere, Francesco

2016-03-01

Early life exposure to air pollution has been linked with cognitive impairment in children, but the results have not been conclusive. We analyzed the association between traffic-related air pollution and cognitive function in a prospective birth cohort in Rome. A cohort of 719 newborns was enrolled in 2003-2004 as part of the GASPII project. At age 7 years, 474 children took the Wechsler Intelligence Scale for Children-III to assess their cognitive development in terms of IQ composite scores. Exposure to air pollutants (NO2, PMcoarse, PM2.5, PM2.5 absorbance) at birth was assessed using land use regression models. We also considered variables indicating traffic intensity. The effect of environmental pollution on IQ was evaluated performing a linear regression model for each outcome, adjusting for gender, child age at cognitive test, maternal age at delivery, parental educational level, siblings, socio-economic status, maternal smoking during pregnancy, and tester. To account for selection bias at enrollment and during follow-up, the regression models were weighted for the inverse probabilities of participation and follow-up. A 10 μg/m³ higher NO2 exposure during pregnancy was associated with 1.4 fewer points (95% confidence interval = -2.6, -0.20) of verbal IQ, and 1.4 fewer points (95% confidence interval = -2.7, -0.20) of verbal comprehension IQ. Similar associations were found for traffic intensity in a 100 m buffer around home. Other pollutants showed negative associations with larger confidence intervals. Consistent with previous evidence, this study suggests an association of exposure to NO2 and traffic intensity with the verbal area of cognitive development.See Video Abstract at http://links.lww.com/EDE/B12.

Um modelo de otimização linear para o planejamento agregado da produção e logística de sementes de milho A linear optimization model to the aggregate production and logistics planning of corn seeds

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Rogério de Ávila Ribeiro Junqueira

2006-12-01

Full Text Available A produção de sementes de milho envolve uma cadeia de produção agroindustrial complexa cujos agentes devem primar por oferecer produtos de alta qualidade a um baixo custo para se manterem competitivos no mercado. Neste trabalho, um modelo de otimização linear é proposto para auxiliar nas decisões do planejamento tático da produção, estocagem e transporte de sementes de milho, de forma a minimizar custos de produção, logísticos e fiscais, atendendo às restrições de programação da colheita, capacidade das plantas e demanda dos clientes. Para verificar a coerência do modelo e validar a abordagem, o modelo foi implementado na linguagem de modelagem GAMS e aplicado para resolver diferentes cenários de um exemplo baseado em dados realistas de uma empresa. Os resultados mostraram a importância de se considerar os custos fiscais de ICMS no planejamento agregado da produção e logística de sementes de milho.The production of corn seeds involves a complex agro-industrial production chain whose main agents must offer products of high quality and low price to stay competitive in the market. This work proposes a linear optimization model to support decisions in the tactical planning of production, storing and transportation of corn seeds, designed to minimize production, logistics and tax costs and to satisfy crop planning, plant capacity and client demand constraints. In order to verify the consistency of the model and validate the approach, the model was implemented in the GAMS modeling language and applied to solve different scenarios of an example based on realistic data of a company. The results showed the importance of considering tax costs in the production and logistics aggregate planning of corn seeds.

Crash forecasting in the Korean stock market based on the log-periodic structure and pattern recognition

Science.gov (United States)

Ko, Bonggyun; Song, Jae Wook; Chang, Woojin

2018-02-01

The aim of this research is to propose an alarm index to forecast the crash of the Korean financial market in extension to the idea of Johansen-Ledoit-Sornette model, which uses the log-periodic functions and pattern recognition algorithm. We discover that the crashes of the Korean financial market can be classified into domestic and global crises where each category requires different window length of fitted datasets. Therefore, we add the window length as a new parameter to enhance the performance of alarm index. Distinguishing the domestic and global crises separately, our alarm index demonstrates more robust forecasting than previous model by showing the error diagram and the results of trading performance.

Application of computer mathematical modeling in nuclear well-logging industry

International Nuclear Information System (INIS)

Cai Shaohui

1994-01-01

Nuclear well logging techniques have made rapid progress since the first well log calibration facility (the API pits) was dedicated in 1959. Then came the first computer mathematical model in the late 70's. Mathematical modeling can now minimize design and experiment time, as well as provide new information and idea on tool design, environmental effects and result interpretation. The author gives a brief review on the achievements of mathematical modeling on nuclear logging problems

Persistent Organic Pollutants in Norwegian Men from 1979 to 2007: Intraindividual Changes, Age–Period–Cohort Effects, and Model Predictions

Science.gov (United States)

Breivik, Knut; Fuskevåg, Ole-Martin; Nieboer, Evert; Odland, Jon Øyvind; Sandanger, Torkjel Manning

2013-01-01

Background: Longitudinal monitoring studies of persistent organic pollutants (POPs) in human populations are important to better understand changes with time and age, and for future predictions. Objectives: We sought to describe serum POP time trends on an individual level, investigate age–period–cohort effects, and compare predicted polychlorinated biphenyl (PCB) concentrations to measured values. Methods: Serum was sampled in 1979, 1986, 1994, 2001, and 2007 from a cohort of 53 men in Northern Norway and analyzed for 41 POPs. Time period, age, and birth cohort effects were assessed by graphical analyses and mixed-effect models. We derived the predicted concentrations of four PCBs for each sampling year using the CoZMoMAN model. Results: The median decreases in summed serum POP concentrations (lipid-adjusted) in 1986, 1994, 2001, and 2007 relative to 1979 were –22%, –52%, –54%, and –68%, respectively. We observed substantial declines in all POP groups with the exception of chlordanes. Time period (reflected by sampling year) was the strongest descriptor of changes in PCB-153 concentrations. Predicted PCB-153 concentrations were consistent with measured concentrations in the study population. Conclusions: Our results suggest substantial intraindividual declines in serum concentrations of legacy POPs from 1979 to 2007 in men from Northern Norway. These changes are consistent with reduced environmental exposure during these 30 years and highlight the relation between historic emissions and POP concentrations measured in humans. Observed data and interpretations are supported by estimates from the CoZMoMAN emission-based model. A longitudinal decrease in concentrations with age was evident for all birth cohorts. Overall, our findings support the relevance of age–period–cohort effects to human biomonitoring of environmental contaminants. Citation: Nøst TH, Breivik K, Fuskevåg OM, Nieboer E, Odland JØ, Sandanger TM. 2013. Persistent organic pollutants

LINEAR2007, Linear-Linear Interpolation of ENDF Format Cross-Sections

International Nuclear Information System (INIS)

2007-01-01

1 - Description of program or function: LINEAR converts evaluated cross sections in the ENDF/B format into a tabular form that is subject to linear-linear interpolation in energy and cross section. The code also thins tables of cross sections already in that form. Codes used subsequently need thus to consider only linear-linear data. IAEA1311/15: This version include the updates up to January 30, 2007. Changes in ENDF/B-VII Format and procedures, as well as the evaluations themselves, make it impossible for versions of the ENDF/B pre-processing codes earlier than PREPRO 2007 (2007 Version) to accurately process current ENDF/B-VII evaluations. The present code can handle all existing ENDF/B-VI evaluations through release 8, which will be the last release of ENDF/B-VI. Modifications from previous versions: - Linear VERS. 2007-1 (JAN. 2007): checked against all ENDF/B-VII; increased page size from 60,000 to 600,000 points 2 - Method of solution: Each section of data is considered separately. Each section of File 3, 23, and 27 data consists of a table of cross section versus energy with any of five interpolation laws. LINEAR will replace each section with a new table of energy versus cross section data in which the interpolation law is always linear in energy and cross section. The histogram (constant cross section between two energies) interpolation law is converted to linear-linear by substituting two points for each initial point. The linear-linear is not altered. For the log-linear, linear-log and log- log laws, the cross section data are converted to linear by an interval halving algorithm. Each interval is divided in half until the value at the middle of the interval can be approximated by linear-linear interpolation to within a given accuracy. The LINEAR program uses a multipoint fractional error thinning algorithm to minimize the size of each cross section table

Exposure to Perfluoroalkyl Substances and Metabolic Outcomes in Pregnant Women: Evidence from the Spanish INMA Birth Cohorts.

Science.gov (United States)

Matilla-Santander, Nuria; Valvi, Damaskini; Lopez-Espinosa, Maria-Jose; Manzano-Salgado, Cyntia B; Ballester, Ferran; Ibarluzea, Jesús; Santa-Marina, Loreto; Schettgen, Thomas; Guxens, Mònica; Sunyer, Jordi; Vrijheid, Martine

2017-11-13

Exposure to perfluoroalkyl substances (PFASs) may increase risk for metabolic diseases; however, epidemiologic evidence is lacking at the present time. Pregnancy is a period of enhanced tissue plasticity for the fetus and the mother and may be a critical window of PFAS exposure susceptibility. We evaluated the associations between PFAS exposures and metabolic outcomes in pregnant women. We analyzed 1,240 pregnant women from the Spanish INMA [Environment and Childhood Project (INfancia y Medio Ambiente)] birth cohort study (recruitment period: 2003-2008) with measured first pregnancy trimester plasma concentrations of four PFASs (in nanograms/milliliter). We used logistic regression models to estimate associations of PFASs (log 10 -transformed and categorized into quartiles) with impaired glucose tolerance (IGT) and gestational diabetes mellitus (GDM), and we used linear regression models to estimate associations with first-trimester serum levels of triglycerides, total cholesterol, and C-reactive protein (CRP). Perfluorooctane sulfonate (PFOS) and perfluorohexane sulfonate (PFHxS) were positively associated with IGT (137 cases) [OR per log 10 -unit increase=1.99 (95% CI: 1.06, 3.78) and OR=1.65 ( 95% CI: 0.99, 2.76), respectively]. PFOS and PFHxS associations with GDM (53 cases) were in a similar direction, but less precise. PFOS and perfluorononanoate (PFNA) were negatively associated with triglyceride levels [percent median change per log 10 -unit increase=-5.86% (95% CI: -9.91%, -1.63%) and percent median change per log 10 -unit increase=-4.75% (95% CI: -8.16%, -0.61%, respectively], whereas perfluorooctanoate (PFOA) was positively associated with total cholesterol [percent median change per log 10 -unit increase=1.26% (95% CI: 0.01%, 2.54%)]. PFASs were not associated with CRP in the subset of the population with available data ( n =640). Although further confirmation is required, the findings from this study suggest that PFAS exposures during pregnancy may

Trends in colorectal cancer incidence: a period and birth-cohort analysis in a well-defined French population.

Science.gov (United States)

Chauvenet, Marion; Cottet, Vanessa; Lepage, Côme; Jooste, Valérie; Faivre, Jean; Bouvier, Anne-Marie

2011-06-30

France stands among high-risk areas for colorectal cancer. Different trends in CRC incidence are reported around the world. The aim of this study was to provide temporal trends in CRC incidence over a 30-year period in a French well-defined population. Between 1976 and 2005, 17,028 new cases were registered by the Burgundy digestive cancer registry. The mean variations in age-standardized incidence rates were estimated using a Poisson regression adjusted for age for each gender and location. The cumulative risk by birth cohort of developing a cancer over the age range 0-74 years was estimated using an age-cohort model. Incidence rates for right and left colon cancers increased more rapidly in males (respectively +11.7% and +10.3% on average by 5-year period) than in females (respectively +5.9% and +6.1%). It remained stable for sigmoid cancers in males (-0.1%) and decreased in females (-5.2%). It also decreased for rectal cancers both in males (-2.7%) and in females (-2.0%). The cumulative risk increased from 3.9% for males born around 1900 to 4.9% for those born around 1930 and then slightly decreased (4.5% among those born around 1950). It remained at the same level for females born around 1900 (2.7%) as for those born around 1930 (2.7%) and then slightly increased (2.9%) for those born around 1950. For right colon cancers, the cumulative risk increased strikingly in successive birth cohorts from 0.53% to 1.2% in males and 0.55% to 0.77% in females. The corresponding cumulative risks for the left colon were 0.24% and 0.42% in males and 0.14% and 0.29% in females. For sigmoid cancer, they decreased from 1.59% to 1.08% in males, and 0.88% to 0.80% in females. Temporal variations in incidence rates of colorectal cancers differed according to subsite, suggesting different aetiological factors and implications for diagnosis and screening strategies. Total colonoscopy must be the preferred strategy in high-risk groups or after a positive faecal occult blood test.

Trends in colorectal cancer incidence: a period and birth-cohort analysis in a well-defined French population

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Faivre Jean

2011-06-01

Full Text Available Abstract Background France stands among high-risk areas for colorectal cancer. Different trends in CRC incidence are reported around the world. The aim of this study was to provide temporal trends in CRC incidence over a 30-year period in a French well-defined population. Methods Between 1976 and 2005, 17,028 new cases were registered by the Burgundy digestive cancer registry. The mean variations in age-standardized incidence rates were estimated using a Poisson regression adjusted for age for each gender and location. The cumulative risk by birth cohort of developing a cancer over the age range 0-74 years was estimated using an age-cohort model. Results Incidence rates for right and left colon cancers increased more rapidly in males (respectively +11.7% and +10.3% on average by 5-year period than in females (respectively +5.9% and +6.1%. It remained stable for sigmoid cancers in males (-0.1% and decreased in females (-5.2%. It also decreased for rectal cancers both in males (-2.7% and in females (-2.0%. The cumulative risk increased from 3.9% for males born around 1900 to 4.9% for those born around 1930 and then slightly decreased (4.5% among those born around 1950. It remained at the same level for females born around 1900 (2.7% as for those born around 1930 (2.7% and then slightly increased (2.9% for those born around 1950. For right colon cancers, the cumulative risk increased strikingly in successive birth cohorts from 0.53% to 1.2% in males and 0.55% to 0.77% in females. The corresponding cumulative risks for the left colon were 0.24% and 0.42% in males and 0.14% and 0.29% in females. For sigmoid cancer, they decreased from 1.59% to 1.08% in males, and 0.88% to 0.80% in females. Conclusion Temporal variations in incidence rates of colorectal cancers differed according to subsite, suggesting different aetiological factors and implications for diagnosis and screening strategies. Total colonoscopy must be the preferred strategy in high

Základní pojmy a principy konstrukce modelů typu věk-období-kohorta

Czech Academy of Sciences Publication Activity Database

Reissigová, Jindra; Rychtaříková, J.

2015-01-01

Roč. 57, č. 1 (2015), s. 21-39 ISSN 0011-8265 Grant - others:GA ČR(CZ) GAP404/12/0883 Institutional support: RVO:67985807 Keywords : Lexis diagram * age-period-cohort * identification problem * generalised linear model * prediction * male mortality * Czech Republic Subject RIV: BB - Applied Statistics, Operational Research

Cohort change and the diffusion of environmental concern: A cross-national analysis

Science.gov (United States)

Nawrotzki, Raphael J.; Pampel, Fred C.

2013-01-01

This study explores value change across cohorts for a multinational population sample. Employing a diffusion-of-innovations approach, we combine competing theories predicting the relationship between socio-economic status (SES) and environmentalism: post-materialism and affluence theories, and global environmentalism theory. The diffusion argument suggests that high-SES groups first adopt pro-environmental views, but as time passes by, environmentalism diffuses to lower-SES groups. We test the diffusion argument using a sample of 18 countries for two waves (years 1993 and 2000) from the International Social Survey Project (ISSP). Cross-classified multilevel modeling allows us to identify a non-linear interaction between cohort and education, our core measure of SES, in predicting environmental concern, while controlling for age and period. We find support for the diffusion argument and demonstrate that the positive effect of education on environmental concern first increases among older cohorts, then starts to level off until a bend-point is reached for individuals born around 1940 and becomes progressively weaker for younger cohorts. PMID:24179313

Teacher characteristics and student performance: An analysis using hierarchical linear modelling

Directory of Open Access Journals (Sweden)

Paula Armstrong

2015-12-01

Full Text Available This research makes use of hierarchical linear modelling to investigate which teacher characteristics are significantly associated with student performance. Using data from the SACMEQ III study of 2007, an interesting and potentially important finding is that younger teachers are better able to improve the mean mathematics performance of their students. Furthermore, younger teachers themselves perform better on subject tests than do their older counterparts. Identical models are run for Sub Saharan countries bordering on South Africa, as well for Kenya and the strong relationship between teacher age and student performance is not observed. Similarly, the model is run for South Africa using data from SACMEQ II (conducted in 2002 and the relationship between teacher age and student performance is also not observed. It must be noted that South African teachers were not tested in SACMEQ II so it was not possible to observe differences in subject knowledge amongst teachers in different cohorts and it was not possible to control for teachers’ level of subject knowledge when observing the relationship between teacher age and student performance. Changes in teacher education in the late 1990s and early 2000s may explain the differences in the performance of younger teachers relative to their older counterparts observed in the later dataset.

Age Effects and Temporal Trends in HPV-Related and HPV-Unrelated Oral Cancer in the United States: A Multistage Carcinogenesis Modeling Analysis.

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Andrew F Brouwer

Full Text Available Differences in prognosis in HPV-positive and HPV-negative oral (oropharyngeal and oral cavity squamous cell carcinomas (OSCCs and increasing incidence of HPV-related cancers have spurred interest in demographic and temporal trends in OSCC incidence. We leverage multistage clonal expansion (MSCE models coupled with age-period-cohort (APC epidemiological models to analyze OSCC data in the SEER cancer registry (1973-2012. MSCE models are based on the initiation-promotion-malignant conversion paradigm in carcinogenesis and allow for interpretation of trends in terms of biological mechanisms. APC models seek to differentiate between the temporal effects of age, period, and birth cohort on cancer risk. Previous studies have looked at the effect of period and cohort on tumor initiation, and we extend this to compare model fits of period and cohort effects on each of tumor initiation, promotion, and malignant conversion rates. HPV-related, HPV-unrelated except oral tongue, and HPV-unrelated oral tongue sites are best described by placing period and cohort effects on the initiation rate. HPV-related and non-oral-tongue HPV-unrelated cancers have similar promotion rates, suggesting similar tumorigenesis dynamics once initiated. Estimates of promotion rates at oral tongue sites are lower, corresponding to a longer sojourn time; this finding is consistent with the hypothesis of an etiology distinct from HPV or alcohol and tobacco use. Finally, for the three subsite groups, men have higher initiation rates than women of the same race, and black people have higher promotion than white people of the same sex. These differences explain part of the racial and sex differences in OSCC incidence.

Analyzing age-specific genetic effects on human extreme age survival in cohort-based longitudinal studies

DEFF Research Database (Denmark)

Tan, Qihua; Jacobsen, Rune; Sørensen, Mette

2013-01-01

The analysis of age-specific genetic effects on human survival over extreme ages is confronted with a deceleration pattern in mortality that deviates from traditional survival models and sparse genetic data available. As human late life is a distinct phase of life history, exploring the genetic...... effects on extreme age survival can be of special interest to evolutionary biology and health science. We introduce a non-parametric survival analysis approach that combines population survival information with individual genotype data in assessing the genetic effects in cohort-based longitudinal studies...

Simple, efficient estimators of treatment effects in randomized trials using generalized linear models to leverage baseline variables.

Science.gov (United States)

Rosenblum, Michael; van der Laan, Mark J

2010-04-01

Models, such as logistic regression and Poisson regression models, are often used to estimate treatment effects in randomized trials. These models leverage information in variables collected before randomization, in order to obtain more precise estimates of treatment effects. However, there is the danger that model misspecification will lead to bias. We show that certain easy to compute, model-based estimators are asymptotically unbiased even when the working model used is arbitrarily misspecified. Furthermore, these estimators are locally efficient. As a special case of our main result, we consider a simple Poisson working model containing only main terms; in this case, we prove the maximum likelihood estimate of the coefficient corresponding to the treatment variable is an asymptotically unbiased estimator of the marginal log rate ratio, even when the working model is arbitrarily misspecified. This is the log-linear analog of ANCOVA for linear models. Our results demonstrate one application of targeted maximum likelihood estimation.

Simple, Efficient Estimators of Treatment Effects in Randomized Trials Using Generalized Linear Models to Leverage Baseline Variables

Science.gov (United States)

Rosenblum, Michael; van der Laan, Mark J.

2010-01-01

Models, such as logistic regression and Poisson regression models, are often used to estimate treatment effects in randomized trials. These models leverage information in variables collected before randomization, in order to obtain more precise estimates of treatment effects. However, there is the danger that model misspecification will lead to bias. We show that certain easy to compute, model-based estimators are asymptotically unbiased even when the working model used is arbitrarily misspecified. Furthermore, these estimators are locally efficient. As a special case of our main result, we consider a simple Poisson working model containing only main terms; in this case, we prove the maximum likelihood estimate of the coefficient corresponding to the treatment variable is an asymptotically unbiased estimator of the marginal log rate ratio, even when the working model is arbitrarily misspecified. This is the log-linear analog of ANCOVA for linear models. Our results demonstrate one application of targeted maximum likelihood estimation. PMID:20628636

[Risk factors of small for the gestational age neonates in a hospital of Lima, Peru].

Science.gov (United States)

Tejeda-Mariaca, J Eduardo; Pizango-Mallqui, Orion; Alburquerque-Duglio, Miguel; Mayta-Tristán, Percy

2015-01-01

Identify risk factors for at-term small for gestational age newborns. Retrospective cohort study using data from the Maternal Perinatal Information System of the Maria Auxiliadora Hospital of Lima, from the period 2000-2010. Maternal age, parity, education level, marital status, pregestational body mass index, number of prenatal care visits, presence of conditions such as preeclampsia, eclampsia, urinary tract infection and gestational diabetes as risk factors in small for gestational age newborns were evaluated. The weight for gestational age was calculated based on Peruvian percentiles. Crude relative risk (RR) and adjusted (ARR) were calculated with confidence intervals of 95% using log-binomial generalized linear models. 64,670 pregnant women were included. The incidence for small for gestational age was 7.2%. Preeclampsia (ARR 2.0, 95% CI: 1.86 to 2.15), eclampsia (ARR 3.22, 95% CI: 2.38 to 4.35), low maternal weight (ARR 1.38; 95% CI: 1.23 to 1.54), nulliparity (ARR 1.32, 95% CI: 1.23 to 1.42), age ≥35 years (ARR 1.16, 95% CI: 1.04 -1.29), having prenatal care visits from 0 to 2 (ARR 1.43, 95% CI: 1.32 to 1.55) and 3 to 5 (ARR 1.22, 95% CI: 1.14 to 1.32) were risk factors for small for gestational age. It is necessary to identify pregnant women with risk factors such as those found to decrease the condition of small for gestational age. Actions should emphasize modifiable factors, such as the frequency of prenatal care visits.

Random-effects linear modeling and sample size tables for two special crossover designs of average bioequivalence studies: the four-period, two-sequence, two-formulation and six-period, three-sequence, three-formulation designs.

Science.gov (United States)

Diaz, Francisco J; Berg, Michel J; Krebill, Ron; Welty, Timothy; Gidal, Barry E; Alloway, Rita; Privitera, Michael

2013-12-01

Due to concern and debate in the epilepsy medical community and to the current interest of the US Food and Drug Administration (FDA) in revising approaches to the approval of generic drugs, the FDA is currently supporting ongoing bioequivalence studies of antiepileptic drugs, the EQUIGEN studies. During the design of these crossover studies, the researchers could not find commercial or non-commercial statistical software that quickly allowed computation of sample sizes for their designs, particularly software implementing the FDA requirement of using random-effects linear models for the analyses of bioequivalence studies. This article presents tables for sample-size evaluations of average bioequivalence studies based on the two crossover designs used in the EQUIGEN studies: the four-period, two-sequence, two-formulation design, and the six-period, three-sequence, three-formulation design. Sample-size computations assume that random-effects linear models are used in bioequivalence analyses with crossover designs. Random-effects linear models have been traditionally viewed by many pharmacologists and clinical researchers as just mathematical devices to analyze repeated-measures data. In contrast, a modern view of these models attributes an important mathematical role in theoretical formulations in personalized medicine to them, because these models not only have parameters that represent average patients, but also have parameters that represent individual patients. Moreover, the notation and language of random-effects linear models have evolved over the years. Thus, another goal of this article is to provide a presentation of the statistical modeling of data from bioequivalence studies that highlights the modern view of these models, with special emphasis on power analyses and sample-size computations.

Orbital stability of periodic traveling-wave solutions for the log-KdV equation

Science.gov (United States)

Natali, Fábio; Pastor, Ademir; Cristófani, Fabrício

2017-09-01

In this paper we establish the orbital stability of periodic waves related to the logarithmic Korteweg-de Vries equation. Our motivation is inspired in the recent work [3], in which the authors established the well-posedness and the linear stability of Gaussian solitary waves. By using the approach put forward recently in [20] to construct a smooth branch of periodic waves as well as to get the spectral properties of the associated linearized operator, we apply the abstract theories in [13] and [25] to deduce the orbital stability of the periodic traveling waves in the energy space.

Geography of breast cancer incidence according to age & birth cohorts.

Science.gov (United States)

Gregorio, David I; Ford, Chandler; Samociuk, Holly

2017-06-01

Geographic variation in breast cancer incidence across Connecticut was examined according to age and birth cohort -specific groups. We assigned each of 60,937 incident breast cancer cases diagnosed in Connecticut, 1986-2009, to one of 828 census tracts around the state. Global and local spatial statistics estimated rate variation across the state according to age and birth cohorts. We found the global distribution of incidence rates across places to be more heterogeneous for younger women and later birth cohorts. Concurrently, the spatial scan identified more locations with significantly high rates that pertained to larger proportions of at-risk women within these groups. Geographic variation by age groups was more pronounced than by birth cohorts. Geographic patterns of cancer incidence exhibit differences within and across age and birth cohorts. With the continued insights from descriptive epidemiology, our capacity to effectively limit spatial disparities in cancer will improve. Copyright © 2017 Elsevier Ltd. All rights reserved.

How does socioeconomic development affect COPD mortality? An age-period-cohort analysis from a recently transitioned population in China.

Directory of Open Access Journals (Sweden)

Jing Chen

Full Text Available BACKGROUND: Chronic obstructive pulmonary disease (COPD is a leading cause of death, particularly in developing countries. Little is known about the effects of economic development on COPD mortality, although economic development may potentially have positive and negative influences over the life course on COPD. We took advantage of a unique population whose rapid and recent economic development is marked by changes at clearly delineated and identifiable time points, and where few women smoke, to examine the effect of macro-level events on COPD mortality. METHODS: We used Poisson regression to decompose sex-specific COPD mortality rates in Hong Kong from 1981 to 2005 into the effects of age, period and cohort. RESULTS: COPD mortality declined strongly over generations for people born from the early to mid 20th century, which was particularly evident for the first generation to grow up in a more economically developed environment for both sexes. Population wide COPD mortality decreased when air quality improved and increased with increasing air pollution. COPD mortality increased with age, particularly after menopause among women. CONCLUSIONS: Economic development may reduce vulnerability to COPD by reducing long-lasting insults to the respiratory system, such as infections, poor nutrition and indoor air pollution. However, some of these gains may be offset if economic development results in increasing air pollution or increasing smoking.

The end of the decline in cervical cancer mortality in Spain: trends across the period 1981-2012.

Science.gov (United States)

Cervantes-Amat, Marta; López-Abente, Gonzalo; Aragonés, Nuria; Pollán, Marina; Pastor-Barriuso, Roberto; Pérez-Gómez, Beatriz

2015-04-15

In Spain, cervical cancer prevention is based on opportunistic screening, due to the disease's traditionally low incidence and mortality rates. Changes in sexual behaviour, tourism and migration have, however, modified the probability of exposure to human papilloma virus among Spaniards. This study thus sought to evaluate recent cervical cancer mortality trends in Spain. We used annual female population figures and individual records of deaths certified as cancer of cervix, reclassifying deaths recorded as unspecified uterine cancer to correct coding quality problems. Joinpoint models were fitted to estimate change points in trends, as well as the annual (APC) and average annual percentage change. Log-linear Poisson models were also used to study age-period-cohort effects on mortality trends and their change points. 1981 marked the beginning of a decline in cervical cancer mortality (APC(1981-2003): -3.2; 95% CI:-3.4;-3.0) that ended in 2003, with rates reaching a plateau in the last decade (APC2003-2012: 0.1; 95% CI:-0.9; 1.2). This trend, which was observable among women aged 45-46 years (APC(2003-2012): 1.4; 95% CI:-0.1;2.9) and over 65 years (APC(2003-2012): -0.1; 95% CI:-1.9;1.7), was clearest in Spain's Mediterranean and Southern regions. The positive influence of opportunistic screening is not strong enough to further reduce cervical cancer mortality rates in the country. Our results suggest that the Spanish Health Authorities should reform current prevention programmes and surveillance strategies in order to confront the challenges posed by cervical cancer.

Summary goodness-of-fit statistics for binary generalized linear models with noncanonical link functions.

Science.gov (United States)

Canary, Jana D; Blizzard, Leigh; Barry, Ronald P; Hosmer, David W; Quinn, Stephen J

2016-05-01

Generalized linear models (GLM) with a canonical logit link function are the primary modeling technique used to relate a binary outcome to predictor variables. However, noncanonical links can offer more flexibility, producing convenient analytical quantities (e.g., probit GLMs in toxicology) and desired measures of effect (e.g., relative risk from log GLMs). Many summary goodness-of-fit (GOF) statistics exist for logistic GLM. Their properties make the development of GOF statistics relatively straightforward, but it can be more difficult under noncanonical links. Although GOF tests for logistic GLM with continuous covariates (GLMCC) have been applied to GLMCCs with log links, we know of no GOF tests in the literature specifically developed for GLMCCs that can be applied regardless of link function chosen. We generalize the Tsiatis GOF statistic originally developed for logistic GLMCCs, (TG), so that it can be applied under any link function. Further, we show that the algebraically related Hosmer-Lemeshow (HL) and Pigeon-Heyse (J(2) ) statistics can be applied directly. In a simulation study, TG, HL, and J(2) were used to evaluate the fit of probit, log-log, complementary log-log, and log models, all calculated with a common grouping method. The TG statistic consistently maintained Type I error rates, while those of HL and J(2) were often lower than expected if terms with little influence were included. Generally, the statistics had similar power to detect an incorrect model. An exception occurred when a log GLMCC was incorrectly fit to data generated from a logistic GLMCC. In this case, TG had more power than HL or J(2) . © 2015 John Wiley & Sons Ltd/London School of Economics.

Trends in Dementia Incidence in a Birth Cohort Analysis of the Einstein Aging Study.

Science.gov (United States)

Derby, Carol A; Katz, Mindy J; Lipton, Richard B; Hall, Charles B

2017-11-01

Trends in dementia incidence rates have important implications for planning and prevention. To better understand incidence trends over time requires separation of age and cohort effects, and few prior studies have used this approach. To examine trends in dementia incidence and concomitant trends in cardiovascular comorbidities among individuals aged 70 years or older who were enrolled in the Einstein Aging Study between 1993 and 2015. In this birth cohort analysis of all-cause dementia incidence in persons enrolled in the Einstein Aging Study from October 20, 1993, through November 17, 2015, a systematically recruited, population-based sample of 1348 participants from Bronx County, New York, who were 70 years or older without dementia at enrollment and at least one annual follow-up was studied. Poisson regression was used to model dementia incidence as a function of age, sex, educational level, race, and birth cohort, with profile likelihood used to identify the timing of significant increases or decreases in incidence. Birth year and age. Incident dementia defined by consensus case conference based on annual, standardized neuropsychological and neurologic examination findings, using criteria from the DSM-IV. Among 1348 individuals (mean [SD] baseline age, 78.5 [5.4] years; 830 [61.6%] female; 915 [67.9%] non-Hispanic white), 150 incident dementia cases developed during 5932 person-years (mean [SD] follow-up, 4.4 [3.4] years). Dementia incidence decreased in successive birth cohorts. Incidence per 100 person-years was 5.09 in birth cohorts before 1920, 3.11 in the 1920 through 1924 birth cohorts, 1.73 in the 1925 through 1929 birth cohorts, and 0.23 in cohorts born after 1929. Change point analyses identified a significant decrease in dementia incidence among those born after July 1929 (95% CI, June 1929 to January 1930). The relative rate for birth cohorts before July 1929 vs after was 0.13 (95% CI, 0.04-0.41). Prevalence of stroke and myocardial infarction

Serum Folate Shows an Inverse Association with Blood Pressure in a Cohort of Chinese Women of Childbearing Age: A Cross-Sectional Study.

Directory of Open Access Journals (Sweden)

Minxue Shen

Full Text Available It has been reported that higher folate intake from food and supplementation is associated with decreased blood pressure (BP. The association between serum folate concentration and BP has been examined in few studies. We aim to examine the association between serum folate and BP levels in a cohort of young Chinese women.We used the baseline data from a pre-conception cohort of women of childbearing age in Liuyang, China, for this study. Demographic data were collected by structured interview. Serum folate concentration was measured by immunoassay, and homocysteine, blood glucose, triglyceride and total cholesterol were measured through standardized clinical procedures. Multiple linear regression and principal component regression model were applied in the analysis.A total of 1,532 healthy normotensive non-pregnant women were included in the final analysis. The mean concentration of serum folate was 7.5 ± 5.4 nmol/L and 55% of the women presented with folate deficiency (< 6.8 nmol/L. Multiple linear regression and principal component regression showed that serum folate levels were inversely associated with systolic and diastolic BP, after adjusting for demographic, anthropometric, and biochemical factors.Serum folate is inversely associated with BP in non-pregnant women of childbearing age with high prevalence of folate deficiency.

Are baby boomer women unique? The moderating effect of birth cohort on age in substance use patterns during midlife.

Science.gov (United States)

Sarabia, Stephanie Elias; Martin, James I

2016-01-01

This study examined the relationships of age to use of alcohol, marijuana, and illicit drugs, and misuse of prescription drugs, among midlife women and whether these relationships are modified by birth cohort. Structural Equation Modeling was used to analyze National Survey on Drug Use and Health data, which included 2,035 baby boomer and silent generation cohort women, ages 30 to 55. Midlife women across cohorts reduced alcohol and marijuana use, but not illicit and prescription drug misuse, as they aged. A modifying effect of birth cohort was not supported, but findings did support differential aging effects across substances. Implications are discussed.

Plasma adiponectin and depressive symptoms during pregnancy and the postpartum period: A prospective cohort study.

Science.gov (United States)

Rebelo, Fernanda; Farias, Dayana R; Struchiner, Claudio J; Kac, Gilberto

2016-04-01

Some authors have described an inverse association between adiponectin and depression, but this association has not yet been investigated during the perinatal period. To evaluate the association between the plasma adiponectin levels and symptoms of depression in women from early pregnancy to 30-45 days postpartum. A prospective cohort of 235 women was analyzed, with four waves of follow-up: 5-13th, 22-26th, and 30-36th gestational weeks and 30-45 days postpartum. Depressive symptoms were measured using the Edinburgh Postnatal Depression Scale (EPDS; cutoff ≥ 11). The plasma adiponectin concentrations were measured using an enzyme-linked immunosorbent assay. The statistical analyses included linear mixed effects regressions to model the association between these time-dependent variables. The prevalence of depressive symptoms was 35.5%, 22.8%, 21.8%, and 16.9% and the median (µg/mL) adiponectin levels were 4.8, 4.7, 4.4, and 7.5 in the 1st, 2nd, and 3rd trimesters and the postpartum period, respectively. Women who remained non-depressed throughout the study tended to have higher values of adiponectin throughout pregnancy and the postpartum period compared to those who had depressive symptoms at least once, but this difference was not statistically significant (β=-0.14; p=0.071). There was no statistically significant association between the plasma adiponectin levels and the EPDS scores in the multiple model (β=-0.07; p=0.320). Losses to follow-up, different procedures for the blood draws at the prenatal and postpartum visits, and the presence of a nested clinical trial with omega-3 supplementation. The plasma adiponectin levels were not associated with depressive symptoms during the perinatal period. Copyright © 2016 Elsevier B.V. All rights reserved.

The Relationship between Health and Community across Aging Cohorts

Directory of Open Access Journals (Sweden)

Julie Norstrand

2014-01-01

Full Text Available Research is needed to examine the connection between older adults and their community as they age. This is important as increasing numbers of older adults wish to age in place. Regression models were examined across 3 cohorts testing relationships among social capital indicators (neighborhood trust, neighborhood support, neighborhood cohesion, neighborhood participation, and telephone interaction with health outcomes (self-rated health, activities of daily living (ADL, and instrumental activities of daily living (IADL. Results showed that most social capital indicators remained significant for all health outcomes into very old age. Development of tools for individual and community interventions to ensure optimal fit between the aging individual and their environment is discussed, along with recommendations for enhancing social work theory and practice.

Confirming the cognition of rising scores: Fox and Mitchum (2013) predicts violations of measurement invariance in series completion between age-matched cohorts.

Science.gov (United States)

Fox, Mark C; Mitchum, Ainsley L

2014-01-01

The trend of rising scores on intelligence tests raises important questions about the comparability of variation within and between time periods. Descriptions of the processes that mediate selection of item responses provide meaningful psychological criteria upon which to base such comparisons. In a recent paper, Fox and Mitchum presented and tested a cognitive theory of rising scores on analogical and inductive reasoning tests that is specific enough to make novel predictions about cohort differences in patterns of item responses for tests such as the Raven's Matrices. In this paper we extend the same proposal in two important ways by (1) testing it against a dataset that enables the effects of cohort to be isolated from those of age, and (2) applying it to two other inductive reasoning tests that exhibit large Flynn effects: Letter Series and Word Series. Following specification and testing of a confirmatory item response model, predicted violations of measurement invariance are observed between two age-matched cohorts that are separated by only 20 years, as members of the later cohort are found to map objects at higher levels of abstraction than members of the earlier cohort who possess the same overall level of ability. Results have implications for the Flynn effect and cognitive aging while underscoring the value of establishing psychological criteria for equating members of distinct groups who achieve the same scores.

Confirming the cognition of rising scores: Fox and Mitchum (2013 predicts violations of measurement invariance in series completion between age-matched cohorts.

Directory of Open Access Journals (Sweden)

Mark C Fox

Full Text Available The trend of rising scores on intelligence tests raises important questions about the comparability of variation within and between time periods. Descriptions of the processes that mediate selection of item responses provide meaningful psychological criteria upon which to base such comparisons. In a recent paper, Fox and Mitchum presented and tested a cognitive theory of rising scores on analogical and inductive reasoning tests that is specific enough to make novel predictions about cohort differences in patterns of item responses for tests such as the Raven's Matrices. In this paper we extend the same proposal in two important ways by (1 testing it against a dataset that enables the effects of cohort to be isolated from those of age, and (2 applying it to two other inductive reasoning tests that exhibit large Flynn effects: Letter Series and Word Series. Following specification and testing of a confirmatory item response model, predicted violations of measurement invariance are observed between two age-matched cohorts that are separated by only 20 years, as members of the later cohort are found to map objects at higher levels of abstraction than members of the earlier cohort who possess the same overall level of ability. Results have implications for the Flynn effect and cognitive aging while underscoring the value of establishing psychological criteria for equating members of distinct groups who achieve the same scores.

CS model coil experimental log book

International Nuclear Information System (INIS)

Nishijima, Gen; Sugimoto, Makoto; Nunoya, Yoshihiko; Wakabayashi, Hiroshi; Tsuji, Hiroshi

2001-02-01

Charging test of the ITER CS Model Coil which is the world's largest superconducting pulse coil and the CS Insert Coil had started at April 11, 2000 and had completed at August 18, 2000. In the campaign, total shot numbers were 356 and the size of the data file in the DAS (Data Acquisition System) was over 20 GB. This report is a database that consists of the log list and the log sheets of every shot. One can access the database, make a search, and browse results via Internet (http://1ogwww.naka.jaeri.go.jp). The database will be useful to quick search to choose necessary shots. (author)

Static dictionaries on AC⁰ RAMs: query time (√log n/log log n) is necessary and sufficient

DEFF Research Database (Denmark)

Andersson, Arne; Miltersen, Peter Bro; Riis, Søren

1996-01-01

) on the time for answering membership queries in a set of size n when reasonable space is used for the data structure storing the set; the upper bound can be obtained using O(n) space, and the lower bound holds even if we allow space 2polylog n. Several variations of this result are also obtained. Among others......, we show a tradeoff between time and circuit depth under the unit-cost assumption: any RAM instruction set which permits a linear space, constant query time solution to the static dictionary problem must have an instruction of depth Ω(log w/log log to), where w is the word size of the machine (and log...

Exposure–response relationships for select cancer and non-cancer health outcomes in a cohort of US firefighters from San Francisco, Chicago and Philadelphia (1950–2009)

Science.gov (United States)

Daniels, Robert D.; Bertke, Stephen; Dahm, Matthew M.; Yiin, James H.; Kubale, Travis L.; Hales, Thomas R.; Baris, Dalsu; Zahm, Shelia H.; Beaumont, James J.; Waters, Kathleen M.; Pinkerton, Lynne E.

2015-01-01

Objectives To examine exposure–response relationships between surrogates of firefighting exposure and select outcomes among previously studied US career firefighters. Methods Eight cancer and four non-cancer outcomes were examined using conditional logistic regression. Incidence density sampling was used to match each case to 200 controls on attained age. Days accrued in firefighting assignments (exposed-days), run totals (fire-runs) and run times (fire-hours) were used as exposure surrogates. HRs comparing 75th and 25th centiles of lagged cumulative exposures were calculated using loglinear, linear, log-quadratic, power and restricted cubic spline general relative risk models. Piecewise constant models were used to examine risk differences by time since exposure, age at exposure and calendar period. Results Among 19 309 male firefighters eligible for the study, there were 1333 cancer deaths and 2609 cancer incidence cases. Significant positive associations between fire-hours and lung cancer mortality and incidence were evident. A similar relation between leukaemia mortality and fire-runs was also found. The lung cancer associations were nearly linear in cumulative exposure, while the association with leukaemia mortality was attenuated at higher exposure levels and greater for recent exposures. Significant negative associations were evident for the exposure surrogates and colorectal and prostate cancers, suggesting a healthy worker survivor effect possibly enhanced by medical screening. Conclusions Lung cancer and leukaemia mortality risks were modestly increasing with firefighter exposures. These findings add to evidence of a causal association between firefighting and cancer. Nevertheless, small effects merit cautious interpretation. We plan to continue to follow the occurrence of disease and injury in this cohort. PMID:25673342

Delineating the third age: joint models of older people's quality of life and attrition in Britain 2002-2010.

Science.gov (United States)

Tampubolon, Gindo

2015-07-01

In the public mind, later life is being transformed by the emerging possibility of a flourishing third age with sustained quality of life. We draw trajectories of life quality measured using CASP-19 over eight years. We refine these trajectories by jointly modelling attrition, since older people tend to leave longitudinal studies (attrite) not at random. Growth curve models are applied to the English Longitudinal Study of Ageing waves 1 to 5. Then joint model is estimated where attrition is considered. Extensive predictors are entered including demographic attributes, social and economic status, health conditions, and behaviours. Strong non-linear age trajectory of life quality is revealed by the growth curve models where the peak is achieved in the late 60s. Then the joint model uncovers the peak somewhat later in time, and also reveals secular improvement in life quality experienced by recent cohorts. Sharp estimates for many predictors of higher levels of life quality are also found. For the first time, the trajectories of life quality in the third age are drawn and improvement across cohorts is demonstrated. The contributions are estimated for predictors amenable to intervention such as social capital. This can help in policy discussion on improving the lives of older people in the third age.

Foundations of linear and generalized linear models

CERN Document Server

Agresti, Alan

2015-01-01

A valuable overview of the most important ideas and results in statistical analysis Written by a highly-experienced author, Foundations of Linear and Generalized Linear Models is a clear and comprehensive guide to the key concepts and results of linear statistical models. The book presents a broad, in-depth overview of the most commonly used statistical models by discussing the theory underlying the models, R software applications, and examples with crafted models to elucidate key ideas and promote practical model building. The book begins by illustrating the fundamentals of linear models,

Log-balanced combinatorial sequences

Directory of Open Access Journals (Sweden)

Tomislav Došlic

2005-01-01

Full Text Available We consider log-convex sequences that satisfy an additional constraint imposed on their rate of growth. We call such sequences log-balanced. It is shown that all such sequences satisfy a pair of double inequalities. Sufficient conditions for log-balancedness are given for the case when the sequence satisfies a two- (or more- term linear recurrence. It is shown that many combinatorially interesting sequences belong to this class, and, as a consequence, that the above-mentioned double inequalities are valid for all of them.

voom: Precision weights unlock linear model analysis tools for RNA-seq read counts.

Science.gov (United States)

Law, Charity W; Chen, Yunshun; Shi, Wei; Smyth, Gordon K

2014-02-03

New normal linear modeling strategies are presented for analyzing read counts from RNA-seq experiments. The voom method estimates the mean-variance relationship of the log-counts, generates a precision weight for each observation and enters these into the limma empirical Bayes analysis pipeline. This opens access for RNA-seq analysts to a large body of methodology developed for microarrays. Simulation studies show that voom performs as well or better than count-based RNA-seq methods even when the data are generated according to the assumptions of the earlier methods. Two case studies illustrate the use of linear modeling and gene set testing methods.

Log-Normal Turbulence Dissipation in Global Ocean Models

Science.gov (United States)

Pearson, Brodie; Fox-Kemper, Baylor

2018-03-01

Data from turbulent numerical simulations of the global ocean demonstrate that the dissipation of kinetic energy obeys a nearly log-normal distribution even at large horizontal scales O (10 km ) . As the horizontal scales of resolved turbulence are larger than the ocean is deep, the Kolmogorov-Yaglom theory for intermittency in 3D homogeneous, isotropic turbulence cannot apply; instead, the down-scale potential enstrophy cascade of quasigeostrophic turbulence should. Yet, energy dissipation obeys approximate log-normality—robustly across depths, seasons, regions, and subgrid schemes. The distribution parameters, skewness and kurtosis, show small systematic departures from log-normality with depth and subgrid friction schemes. Log-normality suggests that a few high-dissipation locations dominate the integrated energy and enstrophy budgets, which should be taken into account when making inferences from simplified models and inferring global energy budgets from sparse observations.

CS model coil experimental log book

Energy Technology Data Exchange (ETDEWEB)

Nishijima, Gen; Sugimoto, Makoto; Nunoya, Yoshihiko; Wakabayashi, Hiroshi; Tsuji, Hiroshi [Japan Atomic Energy Research Inst., Naka, Ibaraki (Japan). Naka Fusion Research Establishment

2001-02-01

Charging test of the ITER CS Model Coil which is the world's largest superconducting pulse coil and the CS Insert Coil had started at April 11, 2000 and had completed at August 18, 2000. In the campaign, total shot numbers were 356 and the size of the data file in the DAS (Data Acquisition System) was over 20 GB. This report is a database that consists of the log list and the log sheets of every shot. One can access the database, make a search, and browse results via Internet (http://1ogwww.naka.jaeri.go.jp). The database will be useful to quick search to choose necessary shots. (author)

Being Small for Gestational Age: Does it Matter for the Neurodevelopment of Premature Infants? A Cohort Study.

Directory of Open Access Journals (Sweden)

Myriam Bickle Graz

Full Text Available Whether being small for gestational age (SGA increases the risk of adverse neurodevelopmental outcome in premature infants remains controversial.to study the impact of SGA (birthweight < percentile 10 on cognition, behavior, neurodevelopmental impairment and use of therapy at 5 years old.This population-based prospective cohort included infants born before 32 weeks of gestation. Cognition was evaluated with the K-ABC, and behavior with the Strengths and Difficulties Questionnaire (SDQ. Primary outcomes were cognitive and behavioral scores, as well as neurodevelopmental impairment (cognitive score < 2SD, hearing loss, blindness, or cerebral palsy. The need of therapy, an indirect indicator of neurodevelopmental impairment, was a secondary outcome. Linear and logistic regression models were used to analyze the association of SGA with neurodevelopment.342/515 (76% premature infants were assessed. SGA was significantly associated with hyperactivity scores of the SDQ (coefficient 0.81, p < 0.04, but not with cognitive scores, neurodevelopmental impairment or the need of therapy. Gestational age, socio-economic status, and major brain lesions were associated with cognitive outcome in the univariate and multivariate model, whereas asphyxia, sepsis and bronchopulmonary dysplasia were associated in the univariate model only. Severe impairment was associated with fetal tobacco exposition, asphyxia, gestational age and major brain lesions. Different neonatal factors were associated with the use of single or multiple therapies: children with one therapy were more likely to have suffered birth asphyxia or necrotizing enterocolitis, whereas the need for several therapies was predicted by major brain lesions.In this large cohort of premature infants, assessed at 5 years old with a complete panel of tests, SGA was associated with hyperactive behavior, but not with cognition, neurodevelopmental impairment or use of therapy. Birthweight <10th percentile alone

Study of the reservoirs of Jurassic and Cretaceous periods in the south-cast slope of Central Kara-Kum vault using combination of acoustic logging, neutron-gamma logging, gamma logging, and electrical logging

International Nuclear Information System (INIS)

Meredov, T.M.; Baranov, M.I.

1978-01-01

Considered is the possibility of application of the combination of neutron-gamma logging, gamma logging al partitioncoustic logging and electrical logging to lithologica of sections, discovery reservoir layers in carbonate and terrigeneous sections as well as quantitative estimation of the porosity coefficients values at prospecting areas in the south-east slope of Central Kara-Kum vault. Neutron-gamma logging mostly makes it possible to partition carbonate rocks into limestones, dolomites and their interstitial variaties and to indicate sand stone layers with different degree of carbonate content

Computer model for calculating gamma-ray pulse-height spectra for logging applications

International Nuclear Information System (INIS)

Evans, M.L.

1981-01-01

A generalized computer model has been devised to simulate the emission, transport, and detection of natural gamma radiation from various logging environments. The model yields high-resolution gamma-ray pulse-height spectra that can be used to correct both gross gamma and spectral gamma-ray logs. The technique can help provide corrections to airborne and surface radiometric survey logs for the effects of varying altitude, formation composition, and overburden. Applied to borehole logging, the model can yield estimates of the effects of varying borehole fluid and casing attenuations, as well as varying formation porosity and saturation

Cohort-based income gradients in obesity among U.S. adults.

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Heo, Jongho; Beck, Audrey N; Lin, Shih-Fan; Marcelli, Enrico; Lindsay, Suzanne; Karl Finch, Brian

2018-03-01

No studies have focused on socioeconomic disparities in obesity within and between cohorts. Our objectives were to examine income gradients in obesity between birth-cohorts (inter-cohort variations) and within each birth-cohort (intra-cohort variations) by gender and race/ethnicity. Our sample includes 56,820 white and black adults from pooled, cross-sectional National Health and Nutrition Examination Surveys (1971-2012). We fit a series of logistic hierarchical Age-Period-Cohort models to control for the effects of age and period, simultaneously. Predicted probabilities of obesity by poverty-to-income ratio were estimated and graphed for 5-year cohort groups from 1901-1990. We also stratified this relationship for four gender and racial/ethnic subgroups. Obesity disparities due to income were weaker for post-World War I and II generations, specifically the mid-1920s and the mid-1940s to 1950s cohorts, than for other cohorts. In contrast, we found greater income gradients in obesity among cohorts from the 1930s to mid-1940s and mid-1960s to 1970s. Moreover, obesity disparities due to income across cohorts vary markedly by gender and race/ethnicity. White women with higher income consistently exhibited a lower likelihood of obesity than those with lower income since early 1900s cohorts; whereas, black men with higher income exhibited higher risks of obesity than those with lower income in most cohorts. Our findings suggest that strategies that address race and/or gender inequalities in obesity should be cognizant of significant historical factors that may be unique to cohorts. Period-based approaches that ignore life-course experiences captured in significant cohort-based experiences may limit the utility of policies and interventions. © 2017 Wiley Periodicals, Inc.

On the analysis of clonogenic survival data: Statistical alternatives to the linear-quadratic model

International Nuclear Information System (INIS)

Unkel, Steffen; Belka, Claus; Lauber, Kirsten

2016-01-01

The most frequently used method to quantitatively describe the response to ionizing irradiation in terms of clonogenic survival is the linear-quadratic (LQ) model. In the LQ model, the logarithm of the surviving fraction is regressed linearly on the radiation dose by means of a second-degree polynomial. The ratio of the estimated parameters for the linear and quadratic term, respectively, represents the dose at which both terms have the same weight in the abrogation of clonogenic survival. This ratio is known as the α/β ratio. However, there are plausible scenarios in which the α/β ratio fails to sufficiently reflect differences between dose-response curves, for example when curves with similar α/β ratio but different overall steepness are being compared. In such situations, the interpretation of the LQ model is severely limited. Colony formation assays were performed in order to measure the clonogenic survival of nine human pancreatic cancer cell lines and immortalized human pancreatic ductal epithelial cells upon irradiation at 0-10 Gy. The resulting dataset was subjected to LQ regression and non-linear log-logistic regression. Dimensionality reduction of the data was performed by cluster analysis and principal component analysis. Both the LQ model and the non-linear log-logistic regression model resulted in accurate approximations of the observed dose-response relationships in the dataset of clonogenic survival. However, in contrast to the LQ model the non-linear regression model allowed the discrimination of curves with different overall steepness but similar α/β ratio and revealed an improved goodness-of-fit. Additionally, the estimated parameters in the non-linear model exhibit a more direct interpretation than the α/β ratio. Dimensionality reduction of clonogenic survival data by means of cluster analysis was shown to be a useful tool for classifying radioresistant and sensitive cell lines. More quantitatively, principal component analysis allowed

Improving linear accelerator service response with a real- time electronic event reporting system.

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Hoisak, Jeremy D P; Pawlicki, Todd; Kim, Gwe-Ya; Fletcher, Richard; Moore, Kevin L

2014-09-08

To track linear accelerator performance issues, an online event recording system was developed in-house for use by therapists and physicists to log the details of technical problems arising on our institution's four linear accelerators. In use since October 2010, the system was designed so that all clinical physicists would receive email notification when an event was logged. Starting in October 2012, we initiated a pilot project in collaboration with our linear accelerator vendor to explore a new model of service and support, in which event notifications were also sent electronically directly to dedicated engineers at the vendor's technical help desk, who then initiated a response to technical issues. Previously, technical issues were reported by telephone to the vendor's call center, which then disseminated information and coordinated a response with the Technical Support help desk and local service engineers. The purpose of this work was to investigate the improvements to clinical operations resulting from this new service model. The new and old service models were quantitatively compared by reviewing event logs and the oncology information system database in the nine months prior to and after initiation of the project. Here, we focus on events that resulted in an inoperative linear accelerator ("down" machine). Machine downtime, vendor response time, treatment cancellations, and event resolution were evaluated and compared over two equivalent time periods. In 389 clinical days, there were 119 machine-down events: 59 events before and 60 after introduction of the new model. In the new model, median time to service response decreased from 45 to 8 min, service engineer dispatch time decreased 44%, downtime per event decreased from 45 to 20 min, and treatment cancellations decreased 68%. The decreased vendor response time and reduced number of on-site visits by a service engineer resulted in decreased downtime and decreased patient treatment cancellations.

Materialism across the lifespan : An age-period-cohort analysis

NARCIS (Netherlands)

Jaspers, Esther; Pieters, Rik

This research examined the development of materialism across the lifespan. Two initial studies revealed that: 1) lay beliefs were that materialism declines with age; and 2) previous research findings also implied a modest, negative relationship between age and materialism. Yet, previous research has

Semi-automatic logarithmic converter of logs

International Nuclear Information System (INIS)

Gol'dman, Z.A.; Bondar's, V.V.

1974-01-01

Semi-automatic logarithmic converter of logging charts. An original semi-automatic converter was developed for use in converting BK resistance logging charts and the time interval, ΔT, of acoustic logs from a linear to a logarithmic scale with a specific ratio for subsequent combining of them with neutron-gamma logging charts in operative interpretation of logging materials by a normalization method. The converter can be used to increase productivity by giving curves different from those obtained in manual, pointwise processing. The equipment operates reliably and is simple in use. (author)

Exposure to Perfluoroalkyl Substances and Metabolic Outcomes in Pregnant Women: Evidence from the Spanish INMA Birth Cohorts

Science.gov (United States)

Matilla-Santander, Nuria; Valvi, Damaskini; Lopez-Espinosa, Maria-Jose; Manzano-Salgado, Cyntia B.; Ballester, Ferran; Ibarluzea, Jesús; Santa-Marina, Loreto; Schettgen, Thomas; Guxens, Mònica; Sunyer, Jordi

2017-01-01

Background: Exposure to perfluoroalkyl substances (PFASs) may increase risk for metabolic diseases; however, epidemiologic evidence is lacking at the present time. Pregnancy is a period of enhanced tissue plasticity for the fetus and the mother and may be a critical window of PFAS exposure susceptibility. Objective: We evaluated the associations between PFAS exposures and metabolic outcomes in pregnant women. Methods: We analyzed 1,240 pregnant women from the Spanish INMA [Environment and Childhood Project (INfancia y Medio Ambiente)] birth cohort study (recruitment period: 2003–2008) with measured first pregnancy trimester plasma concentrations of four PFASs (in nanograms/milliliter). We used logistic regression models to estimate associations of PFASs (log10-transformed and categorized into quartiles) with impaired glucose tolerance (IGT) and gestational diabetes mellitus (GDM), and we used linear regression models to estimate associations with first-trimester serum levels of triglycerides, total cholesterol, and C-reactive protein (CRP). Results: Perfluorooctane sulfonate (PFOS) and perfluorohexane sulfonate (PFHxS) were positively associated with IGT (137 cases) [OR per log10-unit increase=1.99 (95% CI: 1.06, 3.78) and OR=1.65 ( 95% CI: 0.99, 2.76), respectively]. PFOS and PFHxS associations with GDM (53 cases) were in a similar direction, but less precise. PFOS and perfluorononanoate (PFNA) were negatively associated with triglyceride levels [percent median change per log10-unit increase=−5.86% (95% CI: −9.91%, −1.63%) and percent median change per log10-unit increase=−4.75% (95% CI: −8.16%, −0.61%, respectively], whereas perfluorooctanoate (PFOA) was positively associated with total cholesterol [percent median change per log10-unit increase=1.26% (95% CI: 0.01%, 2.54%)]. PFASs were not associated with CRP in the subset of the population with available data (n=640). Conclusions: Although further confirmation is required, the findings from this

Modeling exposure–lag–response associations with distributed lag non-linear models

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Gasparrini, Antonio

2014-01-01

In biomedical research, a health effect is frequently associated with protracted exposures of varying intensity sustained in the past. The main complexity of modeling and interpreting such phenomena lies in the additional temporal dimension needed to express the association, as the risk depends on both intensity and timing of past exposures. This type of dependency is defined here as exposure–lag–response association. In this contribution, I illustrate a general statistical framework for such associations, established through the extension of distributed lag non-linear models, originally developed in time series analysis. This modeling class is based on the definition of a cross-basis, obtained by the combination of two functions to flexibly model linear or nonlinear exposure-responses and the lag structure of the relationship, respectively. The methodology is illustrated with an example application to cohort data and validated through a simulation study. This modeling framework generalizes to various study designs and regression models, and can be applied to study the health effects of protracted exposures to environmental factors, drugs or carcinogenic agents, among others. © 2013 The Authors. Statistics in Medicine published by John Wiley & Sons, Ltd. PMID:24027094

Population age and initial density in a patchy environment affect the occurrence of abrupt transitions in a birth-and-death model of Taylor's law

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Jiang, Jiang; DeAngelis, Donald L.; Zhang, B.; Cohen, J.E.

2014-01-01

Taylor's power law describes an empirical relationship between the mean and variance of population densities in field data, in which the variance varies as a power, b, of the mean. Most studies report values of b varying between 1 and 2. However, Cohen (2014a) showed recently that smooth changes in environmental conditions in a model can lead to an abrupt, infinite change in b. To understand what factors can influence the occurrence of an abrupt change in b, we used both mathematical analysis and Monte Carlo samples from a model in which populations of the same species settled on patches, and each population followed independently a stochastic linear birth-and-death process. We investigated how the power relationship responds to a smooth change of population growth rate, under different sampling strategies, initial population density, and population age. We showed analytically that, if the initial populations differ only in density, and samples are taken from all patches after the same time period following a major invasion event, Taylor's law holds with exponent b=1, regardless of the population growth rate. If samples are taken at different times from patches that have the same initial population densities, we calculate an abrupt shift of b, as predicted by Cohen (2014a). The loss of linearity between log variance and log mean is a leading indicator of the abrupt shift. If both initial population densities and population ages vary among patches, estimates of b lie between 1 and 2, as in most empirical studies. But the value of b declines to ~1 as the system approaches a critical point. Our results can inform empirical studies that might be designed to demonstrate an abrupt shift in Taylor's law.

Modeling and validating the grabbing forces of hydraulic log grapples used in forest operations

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Jingxin Wang; Chris B. LeDoux; Lihai Wang

2003-01-01

The grabbing forces of log grapples were modeled and analyzed mathematically under operating conditions when grabbing logs from compact log piles and from bunch-like log piles. The grabbing forces are closely related to the structural parameters of the grapple, the weight of the grapple, and the weight of the log grabbed. An operational model grapple was designed and...

Cognitive impacts of ambient air pollution in the National Social Health and Aging Project (NSHAP) cohort.

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Tallon, Lindsay A; Manjourides, Justin; Pun, Vivian C; Salhi, Carmel; Suh, Helen

2017-07-01

Pathways through which air pollution may impact cognitive function are poorly understood, particularly with regard to whether and how air pollution interacts with social and emotional factors to influence cognitive health. To examine the association between air pollutant exposures and cognitive outcomes among older adults participating in the National Social Life, Health, and Aging Project (NSHAP) cohort study. Measures of cognitive function, social connectedness, and physical and mental health were obtained for each NSHAP participant starting with Wave 1 of the study in 2005. Cognitive function was assessed using the Chicago Cognitive Function Measure (CCFM) for 3377 participants. Exposures to fine particles (PM 2.5 ) were estimated for each participant using GIS-based spatio-temporal models, and exposures to nitrogen dioxide (NO 2 ) were obtained from the nearest EPA monitors. In adjusted linear regression models, IQR increases in 1 to 7year PM 2.5 exposures were associated with a 0.22 (95% CI: -0.44, -0.01) to a 0.25 (95% CI: -0.43, -0.06) point decrease in CCFM scores, equivalent to aging 1.6years, while exposures to NO 2 were equivalent to aging 1.9years. The impacts of PM 2.5 on cognition were modified by stroke, anxiety, and stress, and were mediated by depression. The impacts of NO 2 were mediated by stress and effect modification by impaired activities of daily living for NO 2 was found. Exposures to long-term PM 2.5 and NO 2 were associated with decreased cognitive function in our cohort of older Americans, and individuals who experienced a stroke or elevated anxiety were more susceptible to the effects of PM 2.5 on cognition. Additionally, mediation results suggest that PM 2.5 may impact cognition through pathways related to mood disorders. Copyright © 2017 Elsevier Ltd. All rights reserved.

Modelling tropical forests response to logging

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Cazzolla Gatti, Roberto; Di Paola, Arianna; Valentini, Riccardo; Paparella, Francesco

2013-04-01

Tropical rainforests are among the most threatened ecosystems by large-scale fragmentation due to human activity such as heavy logging and agricultural clearance. Although, they provide crucial ecosystem goods and services, such as sequestering carbon from the atmosphere, protecting watersheds and conserving biodiversity. In several countries forest resource extraction has experienced a shift from clearcutting to selective logging to maintain a significant forest cover and understock of living biomass. However the knowledge on the short and long-term effects of removing selected species in tropical rainforest are scarce and need to be further investigated. One of the main effects of selective logging on forest dynamics seems to be the local disturbance which involve the invasion of open space by weed, vines and climbers at the expense of the late-successional state cenosis. We present a simple deterministic model that describes the dynamics of tropical rainforest subject to selective logging to understand how and why weeds displace native species. We argue that the selective removal of tallest tropical trees carries out gaps of light that allow weeds, vines and climbers to prevail on native species, inhibiting the possibility of recovery of the original vegetation. Our results show that different regime shifts may occur depending on the type of forest management adopted. This hypothesis is supported by a dataset of trees height and weed/vines cover that we collected from 9 plots located in Central and West Africa both in untouched and managed areas.

The relationship between sugar-sweetened beverages and liver enzymes among healthy premenopausal women: a prospective cohort study.

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Shimony, Maya K; Schliep, Karen C; Schisterman, Enrique F; Ahrens, Katherine A; Sjaarda, Lindsey A; Rotman, Yaron; Perkins, Neil J; Pollack, Anna Z; Wactawski-Wende, Jean; Mumford, Sunni L

2016-03-01

To prospectively assess the association between sugar-sweetened beverages (SSB), added sugar, and total fructose and serum concentrations of liver enzymes among healthy, reproductive-age women. A prospective cohort of 259 premenopausal women (average age 27.3 ± 8.2 years; BMI 24.1 ± kg/m(2)) were followed up for up to two menstrual cycles, providing up to eight fasting blood specimens/cycle and four 24-h dietary recalls/cycle. Women with a history of chronic disease were excluded. Alanine and aspartate aminotransferases (ALT and AST, respectively) were measured in serum samples. Linear mixed models estimated associations between average SSB, added sugar, and total fructose intake and log-transformed liver enzymes adjusting for age, race, body mass index, total energy and alcohol intake, and Mediterranean diet score. For every 1 cup/day increase in SSB consumption and 10 g/day increase in added sugar and total fructose, log ALT increased by 0.079 U/L (95 % CI 0.022, 0.137), 0.012 U/L (95 % CI 0.002, 0.022), and 0.031 (0.012, 0.050), respectively, and log AST increased by 0.029 U/L (-0.011, 0.069), 0.007 U/L (0.000, 0.014), and 0.017 U/L (0.004, 0.030), respectively. Women who consumed ≥1.50 cups/day (12 oz can) SSB versus less had 0.127 U/L (95 % CI 0.001, 0.254) higher ALT [percent change 13.5 % (95 % CI 0.1, 28.9)] and 0.102 (95 % CI 0.015, 0.190) higher AST [percent change 10.8 % (95 % CI 1.5, 20.9)]. Sugar-sweetened beverages were associated with higher serum ALT and AST concentrations among healthy premenopausal women, indicating that habitual consumption of even moderate SSB may elicit hepatic lipogenesis.

Mortality of first world war military personnel: comparison of two military cohorts.

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Wilson, Nick; Clement, Christine; Summers, Jennifer A; Bannister, John; Harper, Glyn

2014-12-16

To identify the impact of the first world war on the lifespan of participating military personnel (including in veterans who survived the war). Comparison of two cohorts of military personnel, followed to death. Military personnel leaving New Zealand to participate in the first world war. From a dataset of the New Zealand Expeditionary Forces, we randomly selected participants who embarked on troopships in 1914 and a comparison non-combat cohort who departed on troopships in late 1918 (350 in each group). Lifespan based on dates of birth and death from a range of sources (such as individual military files and an official database of birth and death records). A quarter of the 1914 cohort died during the war, with deaths from injury predominating (94%) over deaths from disease (6%). This cohort had a significantly shorter lifespan than the late 1918 "non-combat" cohort, with median ages of death being 65.9 versus 74.2, respectively (a difference of 8.3 years shown also in Kaplan-Meier survival curves, log rank Pworld war in 1914 from New Zealand lost around eight years of life (relative to a comparable military cohort). In the postwar period they continued to have an increased risk of premature death. © Wilson et al 2014.

Prenatal Phthalate Exposures and Childhood Fat Mass in a New York City Cohort.

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Buckley, Jessie P; Engel, Stephanie M; Mendez, Michelle A; Richardson, David B; Daniels, Julie L; Calafat, Antonia M; Wolff, Mary S; Herring, Amy H

2016-04-01

Experimental animal studies and limited epidemiologic evidence suggest that prenatal exposure to phthalates may be obesogenic, with potential sex-specific effects of phthalates having anti-androgenic activity. We aimed to assess associations between prenatal phthalate exposures and childhood fat mass in a prospective cohort study. We measured phthalate metabolite concentrations in third-trimester maternal urine in a cohort of women enrolled in New York City between 1998 and 2002 (n = 404). Among 180 children (82 girls and 98 boys), we evaluated body composition using a Tanita scale at multiple follow-up visits between ages 4 and 9 years (363 total visits). We estimated associations of standard deviation differences or tertiles of natural log phthalate metabolite concentrations with percent fat mass using linear mixed-effects regression models with random intercepts for repeated outcome measurements. We assessed associations in multiple metabolite models and adjusted for covariates including prepregnancy body mass index, gestational weight gain, maternal smoking during pregnancy, and breastfeeding. We did not observe associations between maternal urinary phthalate concentrations and percent body fat in models examining continuous exposures. Fat mass was 3.06% (95% CI: -5.99, -0.09%) lower among children in the highest tertile of maternal urinary concentrations of summed di(2-ethylhexyl) phthalate (ΣDEHP) metabolites than in children in the lowest tertile. Though estimates were imprecise, there was little evidence that associations between maternal urinary phthalate concentrations and percent fat mass were modified by child's sex. Prenatal phthalate exposures were not associated with increased body fat among children 4-9 years of age, though high prenatal DEHP exposure may be associated with lower fat mass in childhood. Buckley JP, Engel SM, Mendez MA, Richardson DB, Daniels JL, Calafat AM, Wolff MS, Herring AH. 2016. Prenatal phthalate exposures and childhood fat

Source rock formation evaluation using TOC & Ro log model based on well-log data procesing: study case of Ngimbang formation, North East Java basin

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Fatahillah Yosar

2017-01-01

Full Text Available Ngimbang Formation is known as one major source of hydrocarbon supply in the North Eastern Java Basin. Aged Mid-Eocene, Ngimbang is dominated by sedimentary clastic rocks mostly shale, shaly sandstone, and thick layers of limestone (CD Limestone, with thin layers of coal. Although, laboratory analyses show the Ngimbang Formation to be a relatively rich source-rocks, such data are typically too limited to regionally quantify the distribution of organic matter. To adequately sample the formation both horizontally and vertically on a basin–wide scale, large number of costly and time consuming laboratory analyses would be required. Such analyses are prone to errors from a number of sources, and core data are frequently not available at key locations. In this paper, the authors established four TOC (Total Organic Carbon Content logging calculation models; Passey, Schmoker-Hester, Meyer-Nederloff, and Decker/Density Model by considering the geology of Ngimbang. Well data along with its available core data was used to determine the most suitable model to be applied in the well AFA-1, as well as to compare the accuracy of these TOC model values. The result shows good correlation using Decker (TOC Model and Mallick-Raju (Ro- Vitrinite Reflectance Model. Two source rocks potential zones were detected by these log models.

The period-age relation for cepheids

International Nuclear Information System (INIS)

Efremov, Yu.N.

1978-01-01

The list of 119 cepheid-members of 55 clusters and associations of the Magellanic Clouds, the Galaxy, and M31 is given. The period-age relation is found from the data on 64 cepheids in 29 clusters for which the age determinations are available, the ages of extragalactic clusters were determined mainly from their integral colours. The U-B colours are found to be of much better age parameters than the B-V ones. The composite period-age relation agrees well with the theoretical one. The observed dispersion of the period-age relation leads to an estimate of the age dispersion about 1x10 7 years in the associations. Some peculiarities of the cepheids with the shortest periods amongst others in the same clusters are probably explained if they are overtone pulsators. The period-age relation may be used for an investigation of the recent history of star formation in the galaxies. This relation allows to determine the age gradient across the spiral arm in M31 which is in agreement with the density wave theory predictions. The distribution of cepheids in our Galaxy and neighbouring galaxies is consistent with the conception of star formation lasting for some dozen million years in cells with a dimension of some hundreds of parsecs

Health effects of low doses at low dose rates: dose-response relationship modeling in a cohort of workers of the nuclear industry

International Nuclear Information System (INIS)

Metz-Flamant, Camille

2011-01-01

The aim of this thesis is to contribute to a better understanding of the health effects of chronic external low doses of ionising radiation. This work is based on the French cohort of CEA-AREVA NC nuclear workers. The mains stages of this thesis were (1) conducting a review of epidemiological studies on nuclear workers, (2) completing the database and performing a descriptive analysis of the cohort, (3) quantifying risk by different statistical methods and (4) modelling the exposure-time-risk relationship. The cohort includes monitored workers employed more than one year between 1950 and 1994 at CEA or AREVA NC companies. Individual annual external exposure, history of work, vital status and causes of death were reconstructed for each worker. Standardized mortality ratios using French national mortality rates as external reference were computed. Exposure-risk analysis was conducted in the cohort using the linear excess relative risk model, based on both Poisson regression and Cox model. Time dependent modifying factors were investigated by adding an interaction term in the model or by using exposure time windows. The cohort includes 36, 769 workers, followed-up until age 60 in average. During the 1968- 2004 period, 5, 443 deaths, 2, 213 cancers, 62 leukemia and 1, 314 cardiovascular diseases were recorded. Among the 57% exposed workers, the mean cumulative dose was 21.5 milli-sieverts (mSv). A strong Healthy Worker Effect is observed in the cohort. Significant elevated risks of pleura cancer and melanoma deaths were observed in the cohort but not associated with dose. No significant association was observed with solid cancers, lung cancer and cardiovascular diseases. A significant dose-response relationship was observed for leukemia excluding chronic lymphatic leukemia, mainly for doses received less than 15 years before and for yearly dose rates higher than 10 mSv. This PhD work contributes to the evaluation of risks associated to chronic external radiation

Mothers, places and small for gestational age births: a cohort study.

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Sundquist, Jan; Sundquist, Kristina; Johansson, Sven-Erik; Li, Xinjun; Winkleby, Marilyn

2011-04-01

This study examines whether neighbourhood deprivation increases the risk of giving birth to a small for gestational age (SGA) infant, after accounting for individual-level maternal socioeconomic characteristics. An open cohort of women, aged 20-44 years, was followed from 1 January 1992 through 31 December 2004 for first singleton births. The women's residential addresses during the two consecutive years preceding the birth of their infants were geocoded and classified into three levels of neighbourhood deprivation. Gestational age was confirmed by ultrasound examinations. Multilevel logistic regression models were used in the statistical analysis. Sweden. During the study period, women gave birth to 720 357 infants, of whom 20 487 (2.8%) were SGA. Age-adjusted incidence rates of SGA births increased with increasing level of neighbourhood deprivation. In the total population, 2.5% of births in the least deprived neighbourhoods and 3.5% of births in the most deprived neighbourhoods were SGA. A similar pattern of higher incidence with increasing level of neighbourhood-level deprivation was observed across all individual-level sociodemographic categories, including maternal age, marital status, family income, educational attainment, employment, mobility and urban/rural status. High neighbourhood-level deprivation remained significantly associated with SGA risk after adjusting for maternal sociodemographic characteristics (OR 1.28, 95% CI 1.22 to 1.34). This study is the largest to date of the influence of neighbourhood on SGA birth, with SGA confirmed by ultrasound examination. Results suggest that the characteristics of a mother's neighbourhood affect the risk of delivering an SGA infant independently of maternal sociodemographic characteristics.

Liquidity crisis detection: An application of log-periodic power law structures to default prediction

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Wosnitza, Jan Henrik; Denz, Cornelia

2013-09-01

We employ the log-periodic power law (LPPL) to analyze the late-2000 financial crisis from the perspective of critical phenomena. The main purpose of this study is to examine whether LPPL structures in the development of credit default swap (CDS) spreads can be used for default classification. Based on the different triggers of Bear Stearns’ near bankruptcy during the late-2000 financial crisis and Ford’s insolvency in 2009, this study provides a quantitative description of the mechanism behind bank runs. We apply the Johansen-Ledoit-Sornette (JLS) positive feedback model to explain the rise of financial institutions’ CDS spreads during the global financial crisis 2007-2009. This investigation is based on CDS spreads of 40 major banks over the period from June 2007 to April 2009 which includes a significant CDS spread increase. The qualitative data analysis indicates that the CDS spread variations have followed LPPL patterns during the global financial crisis. Furthermore, the univariate classification performances of seven LPPL parameters as default indicators are measured by Mann-Whitney U tests. The present study supports the hypothesis that discrete scale-invariance governs the dynamics of financial markets and suggests the application of new and fast updateable default indicators to capture the buildup of long-range correlations between creditors.

APPLICATION OF GIS AND GROUNDWATER MODELLING TECHNIQUES TO IDENTIFY THE PERCHED AQUIFERS TO DEMARKATE WATER LOGGING CONDITIONS IN PARTS OF MEHSANA

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D. Rawal

2016-06-01

The study highlights the application of GIS in establishing the basic parameters of soil, land use and the distribution of water logging over a period of time and the groundwater modelling identifies the groundwater regime of the area and estimates the total recharge to the area due to surface water irrigation and rainfall and suggests suitable method to control water logging in the area.

Perceived age as clinically useful biomarker of ageing: cohort study

DEFF Research Database (Denmark)

Christensen, Kaare; Thinggaard, Mikael; McGue, Matt

2009-01-01

OBJECTIVE: To determine whether perceived age correlates with survival and important age related phenotypes. DESIGN: Follow-up study, with survival of twins determined up to January 2008, by which time 675 (37%) had died. SETTING: Population based twin cohort in Denmark. PARTICIPANTS: 20 nurses, 10...... young men, and 11 older women (assessors); 1826 twins aged >or=70. MAIN OUTCOME MEASURES: Assessors: perceived age of twins from photographs. Twins: physical and cognitive tests and molecular biomarker of ageing (leucocyte telomere length). RESULTS: For all three groups of assessors, perceived age...... increased with increasing discordance in perceived age within the twin pair-that is, the bigger the difference in perceived age within the pair, the more likely that the older looking twin died first. Twin analyses suggested that common genetic factors influence both perceived age and survival. Perceived...

The optimization model of the logging machinery usage in forestry practice

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Jitka Janová

2009-01-01

Full Text Available The decision support systems commonly used in industry and economy managerial practice for optimizing the processes are based on algoritmization of the typical decision problems. In Czech forestry business, there is a lack of developed decision support systems, which could be easily used in daily practice. This stems from the fact, that the application of optimization methods is less successful in forestry decision making than in industry or economy due to inherent complexity of the forestry decision problems. There is worldwide ongoing research on optimization models applicable in forestry decision making, but the results are not globally applicable and moreover the cost of possibly arising software tools are indispensable. Especially small and medium forestry companies in Czech Republic can not afford such additional costs, although the results of optimization could positively in­fluen­ce not only the business itself but also the impact of forestry business on the environment. Hence there is a need for user friendly optimization models for forestry decision making in the area of Czech Republic, which could be easily solved in commonly available software, and whose results would be both, realistic and easily applicable in the daily decision making.The aim of this paper is to develop the optimization model for the machinery use planning in Czech logging firm in such a way, that the results can be obtained using MS EXCEL. The goal is to identify the integer number of particular machines which should be outsourced for the next period, when the total cost minimization is required. The linear programming model is designed covering the typical restrictions on available machinery and total volume of trees to be cut and transported. The model offers additional result in the form of optimal employment of particular machines. The solution procedure is described in detail and the results obtained are discussed with respect to its applicability in

Modeling bioaccumulation in humans using poly-parameter linear free energy relationships (PPLFERS)

Energy Technology Data Exchange (ETDEWEB)

Undeman, Emma, E-mail: emma.undeman@itm.su.se; Czub, Gertje; McLachlan, Michael S.

2011-04-01

Chemical partition coefficients between environmental media and biological tissues are a key component of bioaccumulation models. The single-parameter linear free energy relationships (spLFERs) commonly used for predicting partitioning are often derived using apolar chemicals and may not accurately capture polar chemicals. In this study, a poly-parameter LFER (ppLFER) based model of organic chemical bioaccumulation in humans is presented. Chemical partitioning was described by an air-body partition coefficient that was a volume weighted average of ppLFER based partition coefficients for the major organs and tissues constituting the human body. This model was compared to a spLFER model treating the body as a mixture of lipid ({approx} octanol) and water. Although model agreement was good for hydrophobic chemicals (average difference 15% for log K{sub OW} > 4 and log K{sub OA} > 8), the ppLFER model predicted {approx} 90% lower body burdens for hydrophilic chemicals (log K{sub OW} < 0). This was mainly due to lower predictions of muscle and adipose tissue sorption capacity for these chemicals. A comparison of the predicted muscle and adipose tissue sorption capacities of hydrophilic chemicals with measurements indicated that the ppLFER and spLFER models' uncertainties were similar. Consequently, little benefit from the implementation of ppLFERs in this model was identified. - Research Highlights: {yields}Implementation of ppLFERs resulted in on average 90% lower predicted body burdens. {yields}Uncertainties in spLFER and ppLFER predictions were similar. {yields}The benefit from implementation of ppLFERs in bioaccumulation models was limited.

Preliminary report on NTS spectral gamma logging and calibration models

International Nuclear Information System (INIS)

Mathews, M.A.; Warren, R.G.; Garcia, S.R.; Lavelle, M.J.

1985-01-01

Facilities are now available at the Nevada Test Site (NTS) in Building 2201 to calibrate spectral gamma logging equipment in environments of low radioactivity. Such environments are routinely encountered during logging of holes at the NTS. Four calibration models were delivered to Building 2201 in January 1985. Each model, or test pit, consists of a stone block with a 12-inch diameter cored borehole. Preliminary radioelement values from the core for the test pits range from 0.58 to 3.83% potassium (K), 0.48 to 29.11 ppm thorium (Th), and 0.62 to 40.42 ppm uranium (U). Two satellite holes, U19ab number2 and U19ab number3, were logged during the winter of 1984-1985. The response of these logs correlates with contents of the naturally radioactive elements K. Th. and U determined in samples from petrologic zones that occur within these holes. Based on these comparisons, the spectral gamma log aids in the recognition and mapping of subsurface stratigraphic units and alteration features associated with unusual concentration of these radioactive elements, such as clay-rich zones

Transitions in cognitive test scores over 5 and 10 years in elderly people: Evidence for a model of age-related deficit accumulation

Directory of Open Access Journals (Sweden)

Rockwood Kenneth

2008-02-01

Full Text Available Abstract Background On average, health worsens with age, but many people have periods of improvement. A stochastic model provides an excellent description of how such changes occur. Given that cognition also changes with age, we wondered whether the same model might also describe the accumulation of errors in cognitive test scores in community-dwelling older adults. Methods In this prospective cohort study, 8954 older people (aged 65+ at baseline from the Canadian Study of Health and Aging were followed for 10 years. Cognitive status was defined by the number of errors on the 100-point Modified Min-Mental State Examination. The error count was chosen to parallel the deficit count in the general model of aging, which is based on deficit accumulation. As with the deficit count, a Markov chain transition model was employed, with 4 parameters. Results On average, the chance of making errors increased linearly with the number of errors present at each time interval. Changes in cognitive states were described with high accuracy (R2 = 0.96 by a modified Poisson distribution, using four parameters: the background chance of accumulating additional errors, the chance of incurring more or fewer errors, given the existing number, and the corresponding background and incremental chances of dying. Conclusion The change in the number of errors in a cognitive test corresponded to a general model that also summarizes age-related changes in deficits. The model accounts for both improvement and deterioration and appears to represent a clinically relevant means of quantifying how various aspects of health status change with age.

Periodic solutions of asymptotically linear Hamiltonian systems without twist conditions

Energy Technology Data Exchange (ETDEWEB)

Cheng Rong [Coll. of Mathematics and Physics, Nanjing Univ. of Information Science and Tech., Nanjing (China); Dept. of Mathematics, Southeast Univ., Nanjing (China); Zhang Dongfeng [Dept. of Mathematics, Southeast Univ., Nanjing (China)

2010-05-15

In dynamical system theory, especially in many fields of applications from mechanics, Hamiltonian systems play an important role, since many related equations in mechanics can be written in an Hamiltonian form. In this paper, we study the existence of periodic solutions for a class of Hamiltonian systems. By applying the Galerkin approximation method together with a result of critical point theory, we establish the existence of periodic solutions of asymptotically linear Hamiltonian systems without twist conditions. Twist conditions play crucial roles in the study of periodic solutions for asymptotically linear Hamiltonian systems. The lack of twist conditions brings some difficulty to the study. To the authors' knowledge, very little is known about the case, where twist conditions do not hold. (orig.)

Pricing FX Options in the Heston/CIR Jump-Diffusion Model with Log-Normal and Log-Uniform Jump Amplitudes

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Rehez Ahlip

2015-01-01

model for the exchange rate with log-normal jump amplitudes and the volatility model with log-uniformly distributed jump amplitudes. We assume that the domestic and foreign stochastic interest rates are governed by the CIR dynamics. The instantaneous volatility is correlated with the dynamics of the exchange rate return, whereas the domestic and foreign short-term rates are assumed to be independent of the dynamics of the exchange rate and its volatility. The main result furnishes a semianalytical formula for the price of the foreign exchange European call option.

Stability Analysis for Multi-Parameter Linear Periodic Systems

DEFF Research Database (Denmark)

Seyranian, A.P.; Solem, Frederik; Pedersen, Pauli

1999-01-01

This paper is devoted to stability analysis of general linear periodic systems depending on real parameters. The Floquet method and perturbation technique are the basis of the development. We start out with the first and higher-order derivatives of the Floquet matrix with respect to problem...

Exposure-response relationships for select cancer and non-cancer health outcomes in a cohort of U.S. firefighters from San Francisco, Chicago and Philadelphia (1950-2009).

Science.gov (United States)

Daniels, Robert D; Bertke, Stephen; Dahm, Matthew M; Yiin, James H; Kubale, Travis L; Hales, Thomas R; Baris, Dalsu; Zahm, Shelia H; Beaumont, James J; Waters, Kathleen M; Pinkerton, Lynne E

2015-10-01

To examine exposure-response relationships between surrogates of firefighting exposure and select outcomes among previously studied US career firefighters. Eight cancer and four non-cancer outcomes were examined using conditional logistic regression. Incidence density sampling was used to match each case to 200 controls on attained age. Days accrued in firefighting assignments (exposed-days), run totals (fire-runs) and run times (fire-hours) were used as exposure surrogates. HRs comparing 75th and 25th centiles of lagged cumulative exposures were calculated using loglinear, linear, log-quadratic, power and restricted cubic spline general relative risk models. Piecewise constant models were used to examine risk differences by time since exposure, age at exposure and calendar period. Among 19,309 male firefighters eligible for the study, there were 1333 cancer deaths and 2609 cancer incidence cases. Significant positive associations between fire-hours and lung cancer mortality and incidence were evident. A similar relation between leukaemia mortality and fire-runs was also found. The lung cancer associations were nearly linear in cumulative exposure, while the association with leukaemia mortality was attenuated at higher exposure levels and greater for recent exposures. Significant negative associations were evident for the exposure surrogates and colorectal and prostate cancers, suggesting a healthy worker survivor effect possibly enhanced by medical screening. Lung cancer and leukaemia mortality risks were modestly increasing with firefighter exposures. These findings add to evidence of a causal association between firefighting and cancer. Nevertheless, small effects merit cautious interpretation. We plan to continue to follow the occurrence of disease and injury in this cohort. Published by the BMJ Publishing Group Limited. For permission to use (where not already granted under a licence) please go to http://group.bmj.com/group/rights-licensing/permissions.

Doubly robust estimation of generalized partial linear models for longitudinal data with dropouts.

Science.gov (United States)

Lin, Huiming; Fu, Bo; Qin, Guoyou; Zhu, Zhongyi

2017-12-01

We develop a doubly robust estimation of generalized partial linear models for longitudinal data with dropouts. Our method extends the highly efficient aggregate unbiased estimating function approach proposed in Qu et al. (2010) to a doubly robust one in the sense that under missing at random (MAR), our estimator is consistent when either the linear conditional mean condition is satisfied or a model for the dropout process is correctly specified. We begin with a generalized linear model for the marginal mean, and then move forward to a generalized partial linear model, allowing for nonparametric covariate effect by using the regression spline smoothing approximation. We establish the asymptotic theory for the proposed method and use simulation studies to compare its finite sample performance with that of Qu's method, the complete-case generalized estimating equation (GEE) and the inverse-probability weighted GEE. The proposed method is finally illustrated using data from a longitudinal cohort study. © 2017, The International Biometric Society.

Lifecourse Activity Participation From Early, Mid, and Later Adulthood as Determinants of Cognitive Aging: The Lothian Birth Cohort 1921.

Science.gov (United States)

Gow, Alan J; Pattie, Alison; Deary, Ian J

2017-01-01

To examine potential sensitive periods for activity participation across adulthood to reduce cognitive decline and to determine whether associations persist after accounting for the lifetime stability of cognitive ability. The Lothian Birth Cohort 1921 is a longitudinal study of cognitive aging. Participants were born in 1921 and most completed a mental ability test at the age of 11 years. Cognitive assessments were completed at mean ages 79 (N = 550), 83 (N = 321), 87 (N = 235), and 90 years (N = 129). Participants provided retrospective details of their activity participation for young (20-35 years), mid (40-55 years), and later adulthood (60-75 years), and contemporaneously at age 79. Associations between activity and the level of, and change in, cognitive ability in old age were examined with latent growth curve models. Accounting for demographics and childhood cognitive ability, engagement in leisure activities in midlife was positively associated with cognitive ability level (path coefficient = .32), whereas higher physical activity in later adulthood was associated with less cognitive decline (.27). The findings support a lifecourse approach in identifying determinants of cognitive aging; leisure and physical activity during different periods of adulthood may enhance cognitive abilities or reduce decline. © The Author 2016. Published by Oxford University Press on behalf of The Gerontological Society of America.

Non-linear vibrational modes in biomolecules: A periodic orbits description

International Nuclear Information System (INIS)

Kampanarakis, Alexandros; Farantos, Stavros C.; Daskalakis, Vangelis; Varotsis, Constantinos

2012-01-01

Graphical abstract: Vibrational frequency shifts in Fe IV = O species of the active site of cytochrome c oxidase are attributed to changes in the surrounding Coulomb field. Periodic orbits analysis assists to find the most anharmonic modes in model biomolecules. Highlights: ► Periodic orbits are extended to multidimensional potentials of biomolecules. ► Highly anharmonic vibrational modes and center-saddle bifurcations are detected. ► Vibrational frequencies shifts in Oxoferryl species of CcO are observed. - Abstract: The vibrational harmonic normal modes of a molecule, which are valid at energies close to an equilibrium point (a minimum, maximum or saddle of the potential energy surface), are extended by periodic orbits to high energies where anharmonicity and coupling of the degrees of freedom are significant. In this way the assignment of the spectra, and thus the extraction of dynamics in highly excited molecules, can be obtained. New vibrational modes emanating from bifurcations of periodic orbits and long living localized trajectories signal the birth and localization of new quantum states. In this article we review and further study non-linear vibrational modes for model biomolecules such as alanine dipeptide and the active site in the oxoferryl oxidation state of the enzyme cytochrome c oxidase. We locate periodic orbits which exhibit high anhamonicity and lead to center-saddle bifurcations. These modes are associated to an isomerization process in alanine dipeptide and to frequency shifts in the oxoferryl observed by modifying the Coulomb field around the Imidazole–Fe IV = O species.

Piecewise linear regression splines with hyperbolic covariates

International Nuclear Information System (INIS)

Cologne, John B.; Sposto, Richard

1992-09-01

Consider the problem of fitting a curve to data that exhibit a multiphase linear response with smooth transitions between phases. We propose substituting hyperbolas as covariates in piecewise linear regression splines to obtain curves that are smoothly joined. The method provides an intuitive and easy way to extend the two-phase linear hyperbolic response model of Griffiths and Miller and Watts and Bacon to accommodate more than two linear segments. The resulting regression spline with hyperbolic covariates may be fit by nonlinear regression methods to estimate the degree of curvature between adjoining linear segments. The added complexity of fitting nonlinear, as opposed to linear, regression models is not great. The extra effort is particularly worthwhile when investigators are unwilling to assume that the slope of the response changes abruptly at the join points. We can also estimate the join points (the values of the abscissas where the linear segments would intersect if extrapolated) if their number and approximate locations may be presumed known. An example using data on changing age at menarche in a cohort of Japanese women illustrates the use of the method for exploratory data analysis. (author)

Observed temporal evolution of global mean age of stratospheric air for the 2002 to 2010 period

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G. P. Stiller

2012-04-01

Full Text Available An extensive observational data set, consisting of more than 10⁶ SF₆ vertical profiles from MIPAS measurements distributed over the whole globe has been condensed into monthly zonal means of mean age of air for the period September 2002 to January 2010, binned at 10° latitude and 1–2 km altitude. The data were analysed with respect to their temporal variation by fitting a regression model consisting of a constant and a linear increase term, 2 proxies for the QBO variation, sinusoidal terms for the seasonal and semi-annual variation and overtones for the correction of the shapes to the observed data set. The impact of subsidence of mesospheric SF₆-depleted air and in-mixing into non-polar latitudes on mid-latitudinal absolute age of air and its linear increase was assessed and found to be small.

The linear increase of mean age of stratospheric air was found to be positive and partly larger than the trend derived by Engel et al. (2009 for most of the Northern mid-latitudes, the middle stratosphere in the tropics, and parts of the Southern mid-latitudes, as well as for the Southern polar upper stratosphere. Multi-year decrease of age of air was found for the lowermost and the upper stratospheric tropics, for parts of Southern mid-latitudes, and for the Northern polar regions. Analysis of the amplitudes and phases of the seasonal variation shed light on the coupling of stratospheric regions to each other. In particular, the Northern mid-latitude stratosphere is well coupled to the tropics, while the Northern lowermost mid-latitudinal stratosphere is decoupled, confirming the separation of the shallow branch of the Brewer-Dobson circulation from the deep branch. We suggest an overall increased tropical upwelling, together with weakening of mixing barriers, especially in the Northern Hemisphere, as a hypothetical model to explain the observed pattern of linear multi-year increase/decrease, and amplitudes

Birth cohort effects on mortality in Danish women

DEFF Research Database (Denmark)

Jacobsen, Rune; Keiding, Niels; Lynge, Elsebeth

the mothers of the babyboomers, and the women most heavily hit by the epidemic of sexually transmitted diseases in the mid 1940s. These generations of women furthermore entered the Danish labour market in massive numbers in the 1960s. In the present study we examine the mortality of Danish women and compare...... it to mortality of Danish men, Norwegian women and Swedish women. Specifically we aim to answer the questions: 1) Are there comparable birth cohort effects on mortality in Norway and Sweden and what is the impact of the respective Danish birth cohorts on the life expectancy measure 2) Are there specific causes...... groups. The data was analysed using descriptive techniques, Age-period-cohort modelling and age-decomposing of life expectancies. Results: The results showed no similar birth cohort effect for Norway and Sweden when compared to Denmark and a relatively high impact of the birth cohort effect on life...

Non-linear modelling to describe lactation curve in Gir crossbred cows

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Yogesh C. Bangar

2017-02-01

Full Text Available Abstract Background The modelling of lactation curve provides guidelines in formulating farm managerial practices in dairy cows. The aim of the present study was to determine the suitable non-linear model which most accurately fitted to lactation curves of five lactations in 134 Gir crossbred cows reared in Research-Cum-Development Project (RCDP on Cattle farm, MPKV (Maharashtra. Four models viz. gamma-type function, quadratic model, mixed log function and Wilmink model were fitted to each lactation separately and then compared on the basis of goodness of fit measures viz. adjusted R2, root mean square error (RMSE, Akaike’s Informaion Criteria (AIC and Bayesian Information Criteria (BIC. Results In general, highest milk yield was observed in fourth lactation whereas it was lowest in first lactation. Among the models investigated, mixed log function and gamma-type function provided best fit of the lactation curve of first and remaining lactations, respectively. Quadratic model gave least fit to lactation curve in almost all lactations. Peak yield was observed as highest and lowest in fourth and first lactation, respectively. Further, first lactation showed highest persistency but relatively higher time to achieve peak yield than other lactations. Conclusion Lactation curve modelling using gamma-type function may be helpful to setting the management strategies at farm level, however, modelling must be optimized regularly before implementing them to enhance productivity in Gir crossbred cows.

Effect of maternal age on the risk of preterm birth: A large cohort study.

Science.gov (United States)

Fuchs, Florent; Monet, Barbara; Ducruet, Thierry; Chaillet, Nils; Audibert, Francois

2018-01-01

Maternal age at pregnancy is increasing worldwide as well as preterm birth. However, the association between prematurity and advanced maternal age remains controversial. To evaluate the impact of maternal age on the occurrence of preterm birth after controlling for multiple known confounders in a large birth cohort. Retrospective cohort study using data from the QUARISMA study, a large Canadian randomized controlled trial, which collected data from 184,000 births in 32 hospitals. Inclusion criteria were maternal age over 20 years. Exclusion criteria were multiple pregnancy, fetal malformation and intra-uterine fetal death. Five maternal age categories were defined and compared for maternal characteristics, gestational and obstetric complications, and risk factors for prematurity. Risk factors for preterm birth births were included in the study. Chronic hypertension, assisted reproduction techniques, pre-gestational diabetes, invasive procedure in pregnancy, gestational diabetes and placenta praevia were linearly associated with increasing maternal age whereas hypertensive disorders of pregnancy followed a "U" shaped distribution according to maternal age. Crude rates of preterm birth before 37 weeks followed a "U" shaped curve with a nadir at 5.7% for the group of 30-34 years. In multivariate analysis, the adjusted odds ratio (aOR) of prematurity stratified by age group followed a "U" shaped distribution with an aOR of 1.08 (95%CI; 1.01-1.15) for 20-24 years, and 1.20 (95% CI; 1.06-1.36) for 40 years and older. Confounders found to have the greatest impact were placenta praevia, hypertensive complications, and maternal medical history. Even after adjustment for confounders, advanced maternal age (40 years and over) was associated with preterm birth. A maternal age of 30-34 years was associated with the lowest risk of prematurity.

Modeling the dielectric logging tool at high frequency

International Nuclear Information System (INIS)

Chew, W.C.

1987-01-01

The high frequency dielectric logging tool has been used widely in electromagnetic well logging, because by measuring the dielectric constant at high frequencies (1 GHz), the water saturation of rocks could be known without measuring the water salinity in the rocks. As such, it could be used to delineate fresh water bearing zones, as the dielectric constant of fresh water is much higher than that of oil while they may have the same resistivity. The authors present a computer model, though electromagnetic field analysis, the response of such a measurement tool in a well logging environment. As the measurement is performed at high frequency, usually with small separation between the transmitter and receivers, some small geological features could be measured by such a tool. They use the computer model to study the behavior of such a tool across geological bed boundaries, and also across thin geological beds. Such a study could be very useful in understanding the limitation on the resolution of the tool. Furthermore, they could study the standoff effect and the depth of investigation of such a tool. This could delineate the range of usefulness of the measurement

Use of reflectance spectrophotometry and colorimetry in a general linear model for the determination of the age of bruises.

Science.gov (United States)

Hughes, Vanessa K; Langlois, Neil E I

2010-12-01

Bruises can have medicolegal significance such that the age of a bruise may be an important issue. This study sought to determine if colorimetry or reflectance spectrophotometry could be employed to objectively estimate the age of bruises. Based on a previously described method, reflectance spectrophotometric scans were obtained from bruises using a Cary 100 Bio spectrophotometer fitted with a fibre-optic reflectance probe. Measurements were taken from the bruise and a control area. Software was used to calculate the first derivative at 490 and 480 nm; the proportion of oxygenated hemoglobin was calculated using an isobestic point method and a software application converted the scan data into colorimetry data. In addition, data on factors that might be associated with the determination of the age of a bruise: subject age, subject sex, degree of trauma, bruise size, skin color, body build, and depth of bruise were recorded. From 147 subjects, 233 reflectance spectrophotometry scans were obtained for analysis. The age of the bruises ranged from 0.5 to 231.5 h. A General Linear Model analysis method was used. This revealed that colorimetric measurement of the yellowness of a bruise accounted for 13% of the bruise age. By incorporation of the other recorded data (as above), yellowness could predict up to 32% of the age of a bruise-implying that 68% of the variation was dependent on other factors. However, critical appraisal of the model revealed that the colorimetry method of determining the age of a bruise was affected by skin tone and required a measure of the proportion of oxygenated hemoglobin, which is obtained by spectrophotometric methods. Using spectrophotometry, the first derivative at 490 nm alone accounted for 18% of the bruise age estimate. When additional factors (subject sex, bruise depth and oxygenation of hemoglobin) were included in the General Linear Model this increased to 31%-implying that 69% of the variation was dependent on other factors. This

Association of prenatal exposure to benzodiazepines and child internalizing problems: A sibling-controlled cohort study.

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Ragnhild E Brandlistuen

Full Text Available During pregnancy, many women experience sleep problems and anxiety that require treatment. The long-term safety for the child of maternal benzodiazepine (BZD and z-hypnotic use during pregnancy remains controversial.We conducted a cohort and a sibling control study using data from the Norwegian Mother and Child Cohort Study. Data on use of BZD and z-hypnotics, internalizing and externalizing outcomes, and covariates were collected from mothers at gestational weeks 17 and 30 and when children were 0.5, 1.5, and 3 years of age. The total sample consisted of 71,996 children (19,297 siblings at 1.5 years and 55,081 children (13,779 siblings at 3 years. Short-term use was defined as use in one pregnancy period only. Long-term use was defined as use in two or more pregnancy periods. Linear full cohort random-effect and sibling-matched fixed-effect regression models were used to compare internalizing and externalizing behavior in children prenatally exposed compared to those unexposed in the full cohort of pregnancies accounting for family clusters, as well as within sibling clusters comparing pregnancies with discordant exposures. Propensity score (PS adjustment included variables on indication for use (sleep problems, symptoms of anxiety and depression and other potential confounding factors.Long-term prenatal exposure to BZD or z-hypnotics was associated with increased internalizing behavior in crude cohort analyses and at age 1.5 years after PS adjustment in sibling-matched fixed-effect models [β 0.60, 95% confidence interval 0.17-0.95]. Analyses on specific drug groups showed that prenatal exposure to BZD-anxiolytics was associated with increased internalizing problems at both 1.5 years [β 0.25, 0.01-0.49] and 3 years [β 0.26, 0.002-0.52] while exposure to z-hypnotics was not associated with any adverse outcomes after adjustment.The findings suggest a moderate association between BZD-anxiolytic exposure and child internalizing problems that is

Modelling female fertility traits in beef cattle using linear and non-linear models.

Science.gov (United States)

Naya, H; Peñagaricano, F; Urioste, J I

2017-06-01

Female fertility traits are key components of the profitability of beef cattle production. However, these traits are difficult and expensive to measure, particularly under extensive pastoral conditions, and consequently, fertility records are in general scarce and somehow incomplete. Moreover, fertility traits are usually dominated by the effects of herd-year environment, and it is generally assumed that relatively small margins are kept for genetic improvement. New ways of modelling genetic variation in these traits are needed. Inspired in the methodological developments made by Prof. Daniel Gianola and co-workers, we assayed linear (Gaussian), Poisson, probit (threshold), censored Poisson and censored Gaussian models to three different kinds of endpoints, namely calving success (CS), number of days from first calving (CD) and number of failed oestrus (FE). For models involving FE and CS, non-linear models overperformed their linear counterparts. For models derived from CD, linear versions displayed better adjustment than the non-linear counterparts. Non-linear models showed consistently higher estimates of heritability and repeatability in all cases (h 2  linear models; h 2  > 0.23 and r > 0.24, for non-linear models). While additive and permanent environment effects showed highly favourable correlations between all models (>0.789), consistency in selecting the 10% best sires showed important differences, mainly amongst the considered endpoints (FE, CS and CD). In consequence, endpoints should be considered as modelling different underlying genetic effects, with linear models more appropriate to describe CD and non-linear models better for FE and CS. © 2017 Blackwell Verlag GmbH.

Periodic orbits from Δ-modulation of stable linear systems

OpenAIRE

Xia, X.; Zinober, A.

2004-01-01

The �-modulated control of a single input, discrete time, linear stable system is investigated. The modulation direction is given by cTx where c �Rn/{0} is a given, otherwise arbitrary, vector. We obtain necessary and sufficient conditions for the existence of periodic points of a finite order. Some concrete results about the existence of a certain order of periodic points are also derived. We also study the relationship between certain polyhedra and the periodicity of the �-modulated orb...

Mortality of breast cancer in Taiwan, 1971–2010: Temporal changes and an age–period–cohort analysis

Science.gov (United States)

Ho, M.-L.; Hsiao, Y.-H.; Su, S.-Y.

2015-01-01

The current paper describes the age, period and cohort effects on breast cancer mortality in Taiwan. Female breast cancer mortality data were collected from the Taiwan death registries for 1971–2010. The annual percentage changes, age- standardised mortality rates (ASMR) and age–period–cohort model were calculated. The mortality rates increased with advancing age groups when fixing the period. The percentage change in the breast cancer mortality rate increased from 54.79% at aged 20–44 years, to 149.78% in those aged 45–64 years (between 1971–75 and 2006–10). The mortality rates in the 45–64 age group increased steadily from 1971 to 1975 and 2006–10. The 1951 birth cohorts (actual birth cohort; 1947–55) showed peak mortalities in both the 50–54 and 45–49 age groups. We found that the 1951 birth cohorts had the greatest mortality risk from breast cancer. This might be attributed to the DDT that was used in large amounts to prevent deaths from malaria in Taiwan. However, future researches require DDT data to evaluate the association between breast cancer and DDT use. PMID:25020211

Radiation dose dependent risk of liver cancer mortality in the German uranium miners cohort 1946–2003

International Nuclear Information System (INIS)

Dufey, F; Walsh, L; Sogl, M; Tschense, A; Schnelzer, M; Kreuzer, M

2013-01-01

An increased risk of mortality from primary liver cancers among uranium miners has been observed in various studies. An analysis of the data from a German uranium miner cohort (the ‘Wismut cohort’) was used to assess the relationship with ionising radiation. To that end the absorbed organ dose due to high and low linear energy transfer radiation was calculated for 58 987 miners with complete information on radiation exposure from a detailed job–exposure matrix. 159 deaths from liver cancer were observed in the follow-up period from 1946 to 2003. Relative risk models with either linear or categorical dependence on high and low linear energy transfer radiation liver doses were fitted by Poisson regression, stratified on age and calendar year. The linear trend of excess relative risk in a model with both low and high linear transfer radiation is −0.8 (95% confidence interval (CI): −3.7, 2.1) Gy −1 and 48.3 (95% CI: −32.0, 128.6) Gy −1 for low and high linear energy transfer radiation, respectively, and thus not statistically significant for either dose. The increase of excess relative risk with equivalent liver dose is 0.57 (95% CI: −0.69, 1.82) Sv −1 . Adjustment for arsenic only had a negligible effect on the radiation risk. In conclusion, there is only weak evidence for an increase of liver cancer mortality with increasing radiation dose in the German uranium miners cohort considered. However, both a lack of statistical power and potential misclassification of primary liver cancer are issues. (paper)

Uranium logging in earth formations

International Nuclear Information System (INIS)

Givens, W.W.

1979-01-01

A technique is provided for assaying the formations surrounding a borehole for uranium. A borehole logging tool cyclically irradiates the formations with neutrons and responds to neutron fluxes produced during the period of time that prompt neutrons are being produced by the neutron fission of uranium in the formations. A borehole calibration tool employs a steady-state (continuous output) neutron source, firstly, to produce a response to neutron fluxes in models having known concentrations of uranium and, secondly, to to produce a response to neutron fluxes in the formations surrounding the borehole. The neutron flux responses of the borehole calibration tool in both the model and the formations surrounding the borehole are utilized to correct the neutron flux response of the borehole logging tool for the effects of epithermal/thermal neutron moderation, scattering, and absorption within the borehole itself

Stunted at 10 Years. Linear Growth Trajectories and Stunting from Birth to Pre-Adolescence in a Rural Bangladeshi Cohort.

Directory of Open Access Journals (Sweden)

Pernilla Svefors

Full Text Available Few studies in low-income settings analyse linear growth trajectories from foetal life to pre-adolescence. The aim of this study is to describe linear growth and stunting from birth to 10 years in rural Bangladesh and to analyse whether maternal and environmental determinants at conception are associated with linear growth throughout childhood and stunting at 10 years.Pregnant women participating in the MINIMat trial were identified in early pregnancy and a birth cohort (n = 1054 was followed with 19 growth measurements from birth to 10 years. Analyses of baseline predictors and mean height-for-age Z-scores (HAZ over time were modelled using GLMM. Logistic regression analysis was used to investigate the associations between baseline predictors and stunting (HAZ<-2 at 10 years. HAZ decreased to 2 years, followed by an increase up to 10 years, while the average height-for-age difference in cm (HAD to the WHO reference median continued to increase up to 10 years. Prevalence of stunting was highest at 2 years (50% decreasing to 29% at 10 years. Maternal height, maternal educational level and season of conception were all independent predictors of HAZ from birth to pre-adolescence (p<0.001 and stunting at 10 years. The highest probability to be stunted at 10 years was for children born by short mothers (<147.5 cm (ORadj 2.93, 95% CI: 2.06-4.20, mothers with no education (ORadj 1.74, 95% CI 1.17-2.81 or those conceived in the pre-monsoon season (ORadj 1.94, 95% CI 1.37-2.77.Height growth trajectories and prevalence of stunting in pre-adolescence showed strong intergenerational associations, social differentials, and environmental influence from foetal life. Targeting women before and during pregnancy is needed for the prevention of impaired child growth.

Cigarette smoking and the risk of adult leukemia: results from the Three Mile Island cohort study.

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Xu, Xiaohui; Talbott, Evelyn O; Zborowski, Jeanne V; Rager, Judith R

2007-01-01

Smoking is an unconfirmed risk factor for the development of leukemia. The authors examined the potential link using data from the Three Mile Island cohort for the period 1979-1995. Eligible for analysis were 24,539 individuals aged 14 years or older who were followed up over 16 years from the Three Mile Island cohort. The authors identified all incident leukemia cases through the Pennsylvania Department of Health Cancer Registry. They used the Cox proportional hazards model to evaluate the relationships and observed 42 incident leukemia cases, including 15 acute myeloid leukemia (AML) cases, in the cohort. After controlling for other confounding factors, the authors found current smoking to be associated with an increased risk of adult AML (relative risk = 3.47; 95% confidence interval = 1.002-11.99). The authors also observed a marginally significant linear trend of risk of AML associated with the number of years smoked (p = .06). The results from this study suggested that cigarette smoking was associated with an increased risk of adult AML. Further investigation is required to confirm these findings.

Generating log-normal mock catalog of galaxies in redshift space

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Agrawal, Aniket; Makiya, Ryu; Saito, Shun; Komatsu, Eiichiro [Max-Planck-Institut für Astrophysik, Karl-Schwarzschild-Str. 1, 85741 Garching (Germany); Chiang, Chi-Ting [C.N. Yang Institute for Theoretical Physics, Department of Physics and Astronomy, Stony Brook University, Stony Brook, NY 11794 (United States); Jeong, Donghui, E-mail: aniket@mpa-garching.mpg.de, E-mail: makiya@mpa-garching.mpg.de, E-mail: chi-ting.chiang@stonybrook.edu, E-mail: djeong@psu.edu, E-mail: ssaito@mpa-garching.mpg.de, E-mail: komatsu@mpa-garching.mpg.de [Department of Astronomy and Astrophysics, The Pennsylvania State University, University Park, PA 16802 (United States)

2017-10-01

We present a public code to generate a mock galaxy catalog in redshift space assuming a log-normal probability density function (PDF) of galaxy and matter density fields. We draw galaxies by Poisson-sampling the log-normal field, and calculate the velocity field from the linearised continuity equation of matter fields, assuming zero vorticity. This procedure yields a PDF of the pairwise velocity fields that is qualitatively similar to that of N-body simulations. We check fidelity of the catalog, showing that the measured two-point correlation function and power spectrum in real space agree with the input precisely. We find that a linear bias relation in the power spectrum does not guarantee a linear bias relation in the density contrasts, leading to a cross-correlation coefficient of matter and galaxies deviating from unity on small scales. We also find that linearising the Jacobian of the real-to-redshift space mapping provides a poor model for the two-point statistics in redshift space. That is, non-linear redshift-space distortion is dominated by non-linearity in the Jacobian. The power spectrum in redshift space shows a damping on small scales that is qualitatively similar to that of the well-known Fingers-of-God (FoG) effect due to random velocities, except that the log-normal mock does not include random velocities. This damping is a consequence of non-linearity in the Jacobian, and thus attributing the damping of the power spectrum solely to FoG, as commonly done in the literature, is misleading.

Modelling discontinuous well log signal to identify lithological ...

Indian Academy of Sciences (India)

1Indian School of Mines (ISM), Dhanbad 826 004, India. ... new wavelet transform-based algorithm to model the abrupt discontinuous changes from well log data by taking care of ...... the 11th ACM International Conference on Multimedia,.

Age- and cohort-related variance of type-A behavior over 24 years: the Young Finns Study.

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Hintsa, Taina; Jokela, Markus; Pulkki-Råback, Laura; Keltikangas-Järvinen, Liisa

2014-12-01

Over the recent decades, the incidence of cardiovascular and heart diseases has decreased while levels of type-A behavior, i.e., a potential risk factor, appear to have increased. However, the long-term developmental patterns of type-A behavior is poorly understood. Both age- and cohort-related changes may be involved in these developments. The purpose of this study was to examine an age- and cohort-related changes of Hunter-Wolf type-A behavior from adolescence to adulthood. Type-A behavior and its components (aggressiveness, leadership, hard driving, and eagerness energy) were assessed using the Hunter-Wolf A-B rating scale at five time points (1983, 1986, 1989, 2001, and 2007) in a population-based sample consisting of six birth cohorts born between 1962 and 1977 (n = 3,341, a total of 10,506 person observations). Development of type-A behavior and its components was examined with cohort-sequential multilevel modeling. Aggressiveness decreased with age, eagerness energy, hard driving, and global type-A behavior increased, and leadership exhibited no mean level changes. Younger cohorts had higher aggressiveness, lower hard driving, and global type-A behavior. The findings suggest that in order to understand the health consequences of type-A behavior, both life span and societal changes should be considered.

Linear models for assessing mechanisms of sperm competition: the trouble with transformations.

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Eggert, Anne-Katrin; Reinhardt, Klaus; Sakaluk, Scott K

2003-01-01

Although sperm competition is a pervasive selective force shaping the reproductive tactics of males, the mechanisms underlying different patterns of sperm precedence remain obscure. Parker et al. (1990) developed a series of linear models designed to identify two of the more basic mechanisms: sperm lotteries and sperm displacement; the models can be tested experimentally by manipulating the relative numbers of sperm transferred by rival males and determining the paternity of offspring. Here we show that tests of the model derived for sperm lotteries can result in misleading inferences about the underlying mechanism of sperm precedence because the required inverse transformations may lead to a violation of fundamental assumptions of linear regression. We show that this problem can be remedied by reformulating the model using the actual numbers of offspring sired by each male, and log-transforming both sides of the resultant equation. Reassessment of data from a previous study (Sakaluk and Eggert 1996) using the corrected version of the model revealed that we should not have excluded a simple sperm lottery as a possible mechanism of sperm competition in decorated crickets, Gryllodes sigillatus.

Modelling survival and mortality risk to 15 years of age for a national cohort of children with serious congenital heart defects diagnosed in infancy.

Directory of Open Access Journals (Sweden)

Rachel L Knowles

Full Text Available Congenital heart defects (CHDs are a significant cause of death in infancy. Although contemporary management ensures that 80% of affected children reach adulthood, post-infant mortality and factors associated with death during childhood are not well-characterised. Using data from a UK-wide multicentre birth cohort of children with serious CHDs, we observed survival and investigated independent predictors of mortality up to age 15 years.Data were extracted retrospectively from hospital records and death certificates of 3,897 children (57% boys in a prospectively identified cohort, born 1992-1995 with CHDs requiring intervention or resulting in death before age one year. A discrete-time survival model accounted for time-varying predictors; hazards ratios were estimated for mortality. Incomplete data were addressed through multilevel multiple imputation.By age 15 years, 932 children had died; 144 died without any procedure. Survival to one year was 79.8% (95% confidence intervals [CI] 78.5, 81.1% and to 15 years was 71.7% (63.9, 73.4%, with variation by cardiac diagnosis. Importantly, 20% of cohort deaths occurred after age one year. Models using imputed data (including all children from birth demonstrated higher mortality risk as independently associated with cardiac diagnosis, female sex, preterm birth, having additional cardiac defects or non-cardiac malformations. In models excluding children who had no procedure, additional predictors of higher mortality were younger age at first procedure, lower weight or height, longer cardiopulmonary bypass or circulatory arrest duration, and peri-procedural complications; non-cardiac malformations were no longer significant.We confirm the high mortality risk associated with CHDs in the first year of life and demonstrate an important persisting risk of death throughout childhood. Late mortality may be underestimated by procedure-based audit focusing on shorter-term surgical outcomes. National monitoring

Modelling survival and mortality risk to 15 years of age for a national cohort of children with serious congenital heart defects diagnosed in infancy.

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Knowles, Rachel L; Bull, Catherine; Wren, Christopher; Wade, Angela; Goldstein, Harvey; Dezateux, Carol

2014-01-01

Congenital heart defects (CHDs) are a significant cause of death in infancy. Although contemporary management ensures that 80% of affected children reach adulthood, post-infant mortality and factors associated with death during childhood are not well-characterised. Using data from a UK-wide multicentre birth cohort of children with serious CHDs, we observed survival and investigated independent predictors of mortality up to age 15 years. Data were extracted retrospectively from hospital records and death certificates of 3,897 children (57% boys) in a prospectively identified cohort, born 1992-1995 with CHDs requiring intervention or resulting in death before age one year. A discrete-time survival model accounted for time-varying predictors; hazards ratios were estimated for mortality. Incomplete data were addressed through multilevel multiple imputation. By age 15 years, 932 children had died; 144 died without any procedure. Survival to one year was 79.8% (95% confidence intervals [CI] 78.5, 81.1%) and to 15 years was 71.7% (63.9, 73.4%), with variation by cardiac diagnosis. Importantly, 20% of cohort deaths occurred after age one year. Models using imputed data (including all children from birth) demonstrated higher mortality risk as independently associated with cardiac diagnosis, female sex, preterm birth, having additional cardiac defects or non-cardiac malformations. In models excluding children who had no procedure, additional predictors of higher mortality were younger age at first procedure, lower weight or height, longer cardiopulmonary bypass or circulatory arrest duration, and peri-procedural complications; non-cardiac malformations were no longer significant. We confirm the high mortality risk associated with CHDs in the first year of life and demonstrate an important persisting risk of death throughout childhood. Late mortality may be underestimated by procedure-based audit focusing on shorter-term surgical outcomes. National monitoring systems should

Log-layer mismatch and modeling of the fluctuating wall stress in wall-modeled large-eddy simulations

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Yang, Xiang I. A.; Park, George Ilhwan; Moin, Parviz

2017-10-01

Log-layer mismatch refers to a chronic problem found in wall-modeled large-eddy simulation (WMLES) or detached-eddy simulation, where the modeled wall-shear stress deviates from the true one by approximately 15 % . Many efforts have been made to resolve this mismatch. The often-used fixes, which are generally ad hoc, include modifying subgrid-scale stress models, adding a stochastic forcing, and moving the LES-wall-model matching location away from the wall. An analysis motivated by the integral wall-model formalism suggests that log-layer mismatch is resolved by the built-in physics-based temporal filtering. In this work we investigate in detail the effects of local filtering on log-layer mismatch. We show that both local temporal filtering and local wall-parallel filtering resolve log-layer mismatch without moving the LES-wall-model matching location away from the wall. Additionally, we look into the momentum balance in the near-wall region to provide an alternative explanation of how LLM occurs, which does not necessarily rely on the numerical-error argument. While filtering resolves log-layer mismatch, the quality of the wall-shear stress fluctuations predicted by WMLES does not improve with our remedy. The wall-shear stress fluctuations are highly underpredicted due to the implied use of LES filtering. However, good agreement can be found when the WMLES data are compared to the direct numerical simulation data filtered at the corresponding WMLES resolutions.

Cohorts based on decade of death: no evidence for secular trends favoring later cohorts in cognitive aging and terminal decline in the AHEAD study.

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Hülür, Gizem; Infurna, Frank J; Ram, Nilam; Gerstorf, Denis

2013-03-01

Studies of birth-year cohorts examined over the same age range often report secular trends favoring later-born cohorts, who are cognitively fitter and show less steep cognitive declines than earlier-born cohorts. However, there is initial evidence that those advantages of later-born cohorts do not carry into the last years of life, suggesting that pervasive mortality-related processes minimize differences that were apparent earlier in life. Elaborating this work from an alternative perspective on cohort differences, we compared rates of cognitive aging and terminal decline in episodic memory between cohorts based on the year participants had died, earlier (between 1993 and 1999) or later in historical time (between 2000 and 2010). Specifically, we compared trajectories of cognitive decline in 2 death-year cohorts of participants in the Asset and Health Dynamics Among the Oldest Old study that were matched on age at death and education and controlled for a variety of additional covariates. Results revealed little evidence of secular trends favoring later cohorts. To the contrary, the cohort that died in the 2000s showed a less favorable trajectory of age-related memory decline than the cohort that died in the 1990s. In examinations of change in relation to time to death, the cohort dying in the 2000s experienced even steeper terminal declines than the cohort dying in the 1990s. We suggest that secular increases in "manufacturing" survival may exacerbate age- and mortality-related cognitive declines among the oldest old.

Non-linearities in tensile creep of concrete at early age

DEFF Research Database (Denmark)

Hauggaard-Nielsen, Anders Boe; Damkilde, Lars

1997-01-01

A meterial model for creep is proposed which takes into consideration some of the couplings in early age concrete. The model is in incremental form and reflect the hydration process where new layers of cement gel are formed in a stress free state. In the present context attention is on non......-linear creep at high stress levels. The parameteres in the model develop in time as a result of hydration. The creep model has been used to analyse the tensile experiments at different stress levels carried out in the HETEK project. The tests were made on dogbone shaped specimen and the test procedure...

Temporal Decay in Timber Species Composition and Value in Amazonian Logging Concessions.

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Richardson, Vanessa A; Peres, Carlos A

2016-01-01

Throughout human history, slow-renewal biological resource populations have been predictably overexploited, often to the point of economic extinction. We assess whether and how this has occurred with timber resources in the Brazilian Amazon. The asynchronous advance of industrial-scale logging frontiers has left regional-scale forest landscapes with varying histories of logging. Initial harvests in unlogged forests can be highly selective, targeting slow-growing, high-grade, shade-tolerant hardwood species, while later harvests tend to focus on fast-growing, light-wooded, long-lived pioneer trees. Brazil accounts for 85% of all native neotropical forest roundlog production, and the State of Pará for almost half of all timber production in Brazilian Amazonia, the largest old-growth tropical timber reserve controlled by any country. Yet the degree to which timber harvests beyond the first-cut can be financially profitable or demographically sustainable remains poorly understood. Here, we use data on legally planned logging of ~17.3 million cubic meters of timber across 314 species extracted from 824 authorized harvest areas in private and community-owned forests, 446 of which reported volumetric composition data by timber species. We document patterns of timber extraction by volume, species composition, and monetary value along aging eastern Amazonian logging frontiers, which are then explained on the basis of historical and environmental variables. Generalized linear models indicate that relatively recent logging operations farthest from heavy-traffic roads are the most selective, concentrating gross revenues on few high-value species. We find no evidence that the post-logging timber species composition and total value of forest stands recovers beyond the first-cut, suggesting that the commercially most valuable timber species become predictably rare or economically extinct in old logging frontiers. In avoiding even more destructive land-use patterns, managing

A cohort study of developmental polychlorinated biphenyl (PCB) exposure in relation to post-vaccination antibody response at 6-months of age

International Nuclear Information System (INIS)

Jusko, Todd A.; De Roos, Anneclaire J.; Schwartz, Stephen M.; Paige Lawrence, B.; Palkovicova, Lubica; Nemessanyi, Tomas; Drobna, Beata; Fabisikova, Anna; Kocan, Anton; Sonneborn, Dean; Jahnova, Eva; Kavanagh, Terrance J.; Trnovec, Tomas; Hertz-Picciotto, Irva

2010-01-01

Background: Extensive experimental data in animals indicate that exposure to polychlorinated biphenyls (PCBs) during pregnancy leads to changes in offspring immune function during the postnatal period. Whether developmental PCB exposure influences immunologic development in humans has received little study. Methods: The study population was 384 mother-infant pairs recruited from two districts of eastern Slovakia for whom prospectively collected maternal, cord, and 6-month infant blood specimens were available. Several PCB congeners were measured in maternal, cord, and 6-month infant sera by high-resolution gas chromatography with electron capture detection. Concentrations of IgG-specific anti-haemophilus influenzae type b, tetanus toxoid, and diphtheria toxoid were assayed in 6-month infant sera using ELISA methods. Multiple linear regression was used to estimate the relation between maternal, cord, and 6-month infant PCB concentrations and the antibody concentrations evaluated at 6-months of age. Results: Overall, there was little evidence of an association between infant antibody concentrations and PCB measures during the pre- and early postnatal period. In addition, our results did not show specificity in terms of associations limited to a particular developmental period (e.g. pre- vs. postnatal), a particular antibody, or a particular PCB congener. Conclusions: At the PCB concentrations measured in this cohort, which are high relative to most human populations today, we did not detect an association between maternal or early postnatal PCB exposure and specific antibody responses at 6-months of age.

A cohort study of developmental polychlorinated biphenyl (PCB) exposure in relation to post-vaccination antibody response at 6-months of age

Energy Technology Data Exchange (ETDEWEB)

Jusko, Todd A., E-mail: juskota@niehs.nih.gov [Epidemiology Branch, National Institute of Environmental Health Sciences, PO Box 12233, MD A3-05, 111 T.W. Alexander Dr, Rall Bldg 101, Rm A361, Research Triangle Park, NC 27709-2233 (United States); Department of Epidemiology, School of Public Health, University of Washington, Seattle, WA (United States); De Roos, Anneclaire J.; Schwartz, Stephen M. [Department of Epidemiology, School of Public Health, University of Washington, Seattle, WA (United States); Program in Epidemiology, Division of Public Health Sciences, Fred Hutchinson Cancer Research Center, Seattle, WA (United States); Paige Lawrence, B. [Department of Environmental Medicine, University of Rochester School of Medicine and Dentistry, Rochester, NY (United States); Palkovicova, Lubica [Department of Environmental Medicine, Slovak Medical University, Bratislava (Slovakia); Nemessanyi, Tomas [Department of Immunology and Immunotoxicology, Slovak Medical University, Bratislava (Slovakia); Drobna, Beata; Fabisikova, Anna; Kocan, Anton [Department of Toxic Organic Pollutants, Slovak Medical University, Bratislava (Slovakia); Sonneborn, Dean [Department of Public Health Sciences, University of California, Davis, CA (United States); Jahnova, Eva [Department of Immunology and Immunotoxicology, Slovak Medical University, Bratislava (Slovakia); Kavanagh, Terrance J. [Department of Environmental and Occupational Health Sciences, School of Public Health, University of Washington, Seattle, WA (United States); Trnovec, Tomas [Department of Toxic Organic Pollutants, Slovak Medical University, Bratislava (Slovakia); Hertz-Picciotto, Irva [Department of Public Health Sciences, University of California, Davis, CA (United States)

2010-05-15

Background: Extensive experimental data in animals indicate that exposure to polychlorinated biphenyls (PCBs) during pregnancy leads to changes in offspring immune function during the postnatal period. Whether developmental PCB exposure influences immunologic development in humans has received little study. Methods: The study population was 384 mother-infant pairs recruited from two districts of eastern Slovakia for whom prospectively collected maternal, cord, and 6-month infant blood specimens were available. Several PCB congeners were measured in maternal, cord, and 6-month infant sera by high-resolution gas chromatography with electron capture detection. Concentrations of IgG-specific anti-haemophilus influenzae type b, tetanus toxoid, and diphtheria toxoid were assayed in 6-month infant sera using ELISA methods. Multiple linear regression was used to estimate the relation between maternal, cord, and 6-month infant PCB concentrations and the antibody concentrations evaluated at 6-months of age. Results: Overall, there was little evidence of an association between infant antibody concentrations and PCB measures during the pre- and early postnatal period. In addition, our results did not show specificity in terms of associations limited to a particular developmental period (e.g. pre- vs. postnatal), a particular antibody, or a particular PCB congener. Conclusions: At the PCB concentrations measured in this cohort, which are high relative to most human populations today, we did not detect an association between maternal or early postnatal PCB exposure and specific antibody responses at 6-months of age.

Mortality (1968-2008) in a French cohort of uranium enrichment workers potentially exposed to rapidly soluble uranium compounds.

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Zhivin, Sergey; Guseva Canu, Irina; Samson, Eric; Laurent, Olivier; Grellier, James; Collomb, Philippe; Zablotska, Lydia B; Laurier, Dominique

2016-03-01

Until recently, enrichment of uranium for civil and military purposes in France was carried out by gaseous diffusion using rapidly soluble uranium compounds. We analysed the relationship between exposure to soluble uranium compounds and exposure to external γ-radiation and mortality in a cohort of 4688 French uranium enrichment workers who were employed between 1964 and 2006. Data on individual annual exposure to radiological and non-radiological hazards were collected for workers of the AREVA NC, CEA and Eurodif uranium enrichment plants from job-exposure matrixes and external dosimetry records, differentiating between natural, enriched and depleted uranium. Cause-specific mortality was compared with the French general population via standardised mortality ratios (SMR), and was analysed via Poisson regression using log-linear and linear excess relative risk models. Over the period of follow-up, 131 161 person-years at risk were accrued and 21% of the subjects had died. A strong healthy worker effect was observed: all causes SMR=0.69, 95% CI 0.65 to 0.74. SMR for pleural cancer was significantly increased (2.3, 95% CI 1.06 to 4.4), but was only based on nine cases. Internal uranium and external γ-radiation exposures were not significantly associated with any cause of mortality. This is the first study of French uranium enrichment workers. Although limited in statistical power, further follow-up of this cohort, estimation of internal uranium doses and pooling with similar cohorts should elucidate potential risks associated with exposure to soluble uranium compounds. Published by the BMJ Publishing Group Limited. For permission to use (where not already granted under a licence) please go to http://www.bmj.com/company/products-services/rights-and-licensing/

Apparent Transition in the Human Height Distribution Caused by Age-Dependent Variation during Puberty Period

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Iwata, Takaki; Yamazaki, Yoshihiro; Kuninaka, Hiroto

2013-08-01

In this study, we examine the validity of the transition of the human height distribution from the log-normal distribution to the normal distribution during puberty, as suggested in an earlier study [Kuninaka et al.: J. Phys. Soc. Jpn. 78 (2009) 125001]. Our data analysis reveals that, in late puberty, the variation in height decreases as children grow. Thus, the classification of a height dataset by age at this stage leads us to analyze a mixture of distributions with larger means and smaller variations. This mixture distribution has a negative skewness and is consequently closer to the normal distribution than to the log-normal distribution. The opposite case occurs in early puberty and the mixture distribution is positively skewed, which resembles the log-normal distribution rather than the normal distribution. Thus, this scenario mimics the transition during puberty. Additionally, our scenario is realized through a numerical simulation based on a statistical model. The present study does not support the transition suggested by the earlier study.

Estimation of the non records logs from existing logs using artificial neural networks

Directory of Open Access Journals (Sweden)

Mehdi Mohammad Salehi

2017-12-01

Full Text Available Finding the information of the hydrocarbon reservoirs from well logs is one of the main objectives of the engineers. But, missing the log records (due to many reasons such as broken instruments, unsuitable borehole and etc. is a major challenge to achieve it. Prediction of the density and resistivity logs (Rt, DT and LLS from the conventional wire-line logs in one of the Iranian southwest oil fields is the main purpose of this study. Multilayer neural network was applied to develop an intelligent predictive model for prediction of the logs. A total of 3000 data sets from 3 wells (A, B and C of the studied field were used. Among them, the data of A, B and C wells were used to constructing and testing the model, respectively. To evaluate the performance of the model, the mean square error (MSE and correlation coefficient (R2 in the test data were calculated. A comparison between the MSE of the proposed model and recently intelligent models shows that the proposed model is more accurate than others. Acceptable accuracy and using conventional well logging data are the highlight advantages of the proposed intelligent model.

Linear models with R

CERN Document Server

Faraway, Julian J

2014-01-01

A Hands-On Way to Learning Data AnalysisPart of the core of statistics, linear models are used to make predictions and explain the relationship between the response and the predictors. Understanding linear models is crucial to a broader competence in the practice of statistics. Linear Models with R, Second Edition explains how to use linear models in physical science, engineering, social science, and business applications. The book incorporates several improvements that reflect how the world of R has greatly expanded since the publication of the first edition.New to the Second EditionReorganiz

Standardized binomial models for risk or prevalence ratios and differences.

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Richardson, David B; Kinlaw, Alan C; MacLehose, Richard F; Cole, Stephen R

2015-10-01

Epidemiologists often analyse binary outcomes in cohort and cross-sectional studies using multivariable logistic regression models, yielding estimates of adjusted odds ratios. It is widely known that the odds ratio closely approximates the risk or prevalence ratio when the outcome is rare, and it does not do so when the outcome is common. Consequently, investigators may decide to directly estimate the risk or prevalence ratio using a log binomial regression model. We describe the use of a marginal structural binomial regression model to estimate standardized risk or prevalence ratios and differences. We illustrate the proposed approach using data from a cohort study of coronary heart disease status in Evans County, Georgia, USA. The approach reduces problems with model convergence typical of log binomial regression by shifting all explanatory variables except the exposures of primary interest from the linear predictor of the outcome regression model to a model for the standardization weights. The approach also facilitates evaluation of departures from additivity in the joint effects of two exposures. Epidemiologists should consider reporting standardized risk or prevalence ratios and differences in cohort and cross-sectional studies. These are readily-obtained using the SAS, Stata and R statistical software packages. The proposed approach estimates the exposure effect in the total population. © The Author 2015; all rights reserved. Published by Oxford University Press on behalf of the International Epidemiological Association.

Stressful life-events in childhood and risk of multiple sclerosis: a Danish nationwide cohort study.

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Nielsen, Nete Munk; Pedersen, Bo V; Stenager, Egon; Koch-Henriksen, Nils; Frisch, Morten

2014-10-01

Current knowledge concerning the association between exposure to stressful life-events (SFLEs) in childhood and later risk of multiple sclerosis (MS) is sparse. We studied the associations between SFLEs in childhood and subsequent risk of MS in a nationwide cohort of 2.9 million Danes born from 1968 to 2011. A SFLE in childhood was defined as exposure before age 18 years to parental divorce, parental death, or death of a sibling, using information from the Danish Civil Registration System. MS cases in the cohort were identified in the Danish Multiple Sclerosis Registry. Associations of SFLE with MS risk were evaluated by incidence rate ratios (RR) of MS obtained in log-linear Poisson regression models. Persons exposed to any SFLE in childhood were at 11% elevated risk of MS (RR = 1.11; 95% confidence interval: 1.03-1.20), compared to non-exposed persons. Stratification by subtype of SFLE showed that parental death and death of a sibling were not associated with MS risk. However, persons exposed to parental divorce were at 13% increased risk of developing MS compared to non-exposed (RR = 1.13; 1.04-1.23). Associations of SFLEs in childhood with risk of MS are weak. However, parental divorce is somehow associated with modestly increased risk of MS. © The Author(s), 2014.

Pleiotropy analysis of quantitative traits at gene level by multivariate functional linear models.

Science.gov (United States)

Wang, Yifan; Liu, Aiyi; Mills, James L; Boehnke, Michael; Wilson, Alexander F; Bailey-Wilson, Joan E; Xiong, Momiao; Wu, Colin O; Fan, Ruzong

2015-05-01

In genetics, pleiotropy describes the genetic effect of a single gene on multiple phenotypic traits. A common approach is to analyze the phenotypic traits separately using univariate analyses and combine the test results through multiple comparisons. This approach may lead to low power. Multivariate functional linear models are developed to connect genetic variant data to multiple quantitative traits adjusting for covariates for a unified analysis. Three types of approximate F-distribution tests based on Pillai-Bartlett trace, Hotelling-Lawley trace, and Wilks's Lambda are introduced to test for association between multiple quantitative traits and multiple genetic variants in one genetic region. The approximate F-distribution tests provide much more significant results than those of F-tests of univariate analysis and optimal sequence kernel association test (SKAT-O). Extensive simulations were performed to evaluate the false positive rates and power performance of the proposed models and tests. We show that the approximate F-distribution tests control the type I error rates very well. Overall, simultaneous analysis of multiple traits can increase power performance compared to an individual test of each trait. The proposed methods were applied to analyze (1) four lipid traits in eight European cohorts, and (2) three biochemical traits in the Trinity Students Study. The approximate F-distribution tests provide much more significant results than those of F-tests of univariate analysis and SKAT-O for the three biochemical traits. The approximate F-distribution tests of the proposed functional linear models are more sensitive than those of the traditional multivariate linear models that in turn are more sensitive than SKAT-O in the univariate case. The analysis of the four lipid traits and the three biochemical traits detects more association than SKAT-O in the univariate case. © 2015 WILEY PERIODICALS, INC.

Bladder cancer mapping in Libya based on standardized morbidity ratio and log-normal model

Science.gov (United States)

Alhdiri, Maryam Ahmed; Samat, Nor Azah; Mohamed, Zulkifley

2017-05-01

Disease mapping contains a set of statistical techniques that detail maps of rates based on estimated mortality, morbidity, and prevalence. A traditional approach to measure the relative risk of the disease is called Standardized Morbidity Ratio (SMR). It is the ratio of an observed and expected number of accounts in an area, which has the greatest uncertainty if the disease is rare or if geographical area is small. Therefore, Bayesian models or statistical smoothing based on Log-normal model are introduced which might solve SMR problem. This study estimates the relative risk for bladder cancer incidence in Libya from 2006 to 2007 based on the SMR and log-normal model, which were fitted to data using WinBUGS software. This study starts with a brief review of these models, starting with the SMR method and followed by the log-normal model, which is then applied to bladder cancer incidence in Libya. All results are compared using maps and tables. The study concludes that the log-normal model gives better relative risk estimates compared to the classical method. The log-normal model has can overcome the SMR problem when there is no observed bladder cancer in an area.

Linear time series modeling of GPS-derived TEC observations over the Indo-Thailand region

Science.gov (United States)

Suraj, Puram Sai; Kumar Dabbakuti, J. R. K.; Chowdhary, V. Rajesh; Tripathi, Nitin K.; Ratnam, D. Venkata

2017-12-01

This paper proposes a linear time series model to represent the climatology of the ionosphere and to investigate the characteristics of hourly averaged total electron content (TEC). The GPS-TEC observation data at the Bengaluru international global navigation satellite system (GNSS) service (IGS) station (geographic 13.02°N , 77.57°E ; geomagnetic latitude 4.4°N ) have been utilized for processing the TEC data during an extended period (2009-2016) in the 24{th} solar cycle. Solar flux F10.7p index, geomagnetic Ap index, and periodic oscillation factors have been considered to construct a linear TEC model. It is evident from the results that solar activity effect on TEC is high. It reaches the maximum value (˜ 40 TECU) during the high solar activity (HSA) year (2014) and minimum value (˜ 15 TECU) during the low solar activity (LSA) year (2009). The larger magnitudes of semiannual variations are observed during the HSA periods. The geomagnetic effect on TEC is relatively low, with the highest being ˜ 4 TECU (March 2015). The magnitude of periodic variations can be seen more significantly during HSA periods (2013-2015) and less during LSA periods (2009-2011). The correlation coefficient of 0.89 between the observations and model-based estimations has been found. The RMSE between the observed TEC and model TEC values is 4.0 TECU (linear model) and 4.21 TECU (IRI2016 Model). Further, the linear TEC model has been validated at different latitudes over the northern low-latitude region. The solar component (F10.7p index) value decreases with an increase in latitude. The magnitudes of the periodic component become less significant with the increase in latitude. The influence of geomagnetic component becomes less significant at Lucknow GNSS station (26.76°N, 80.88°E) when compared to other GNSS stations. The hourly averaged TEC values have been considered and ionospheric features are well recovered with linear TEC model.

Measurement and Evaluation of Finger Tapping Movements Using Log-linearized Gaussian Mixture Networks

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Masaru Yokoe

2009-03-01

Full Text Available This paper proposes a method to quantitatively measure and evaluate finger tapping movements for the assessment of motor function using log-linearized Gaussian mixture networks (LLGMNs. First, finger tapping movements are measured using magnetic sensors, and eleven indices are computed for evaluation. After standardizing these indices based on those of normal subjects, they are input to LLGMNs to assess motor function. Then, motor ability is probabilistically discriminated to determine whether it is normal or not using a classifier combined with the output of multiple LLGMNs based on bagging and entropy. This paper reports on evaluation and discrimination experiments performed on finger tapping movements in 33 Parkinson’s disease (PD patients and 32 normal elderly subjects. The results showed that the patients could be classified correctly in terms of their impairment status with a high degree of accuracy (average rate: 93:1 § 3:69% using 12 LLGMNs, which was about 5% higher than the results obtained using a single LLGMN.

Health effects of low doses at low dose rates: dose-response relationship modeling in a cohort of workers of the nuclear industry; Effets sanitaires des faibles doses a faibles debits de dose: modelisation de la relation dose-reponse dans une cohorte de travailleurs du nucleaire

Energy Technology Data Exchange (ETDEWEB)

Metz-Flamant, Camille

2011-09-19

The aim of this thesis is to contribute to a better understanding of the health effects of chronic external low doses of ionising radiation. This work is based on the French cohort of CEA-AREVA NC nuclear workers. The mains stages of this thesis were (1) conducting a review of epidemiological studies on nuclear workers, (2) completing the database and performing a descriptive analysis of the cohort, (3) quantifying risk by different statistical methods and (4) modelling the exposure-time-risk relationship. The cohort includes monitored workers employed more than one year between 1950 and 1994 at CEA or AREVA NC companies. Individual annual external exposure, history of work, vital status and causes of death were reconstructed for each worker. Standardized mortality ratios using French national mortality rates as external reference were computed. Exposure-risk analysis was conducted in the cohort using the linear excess relative risk model, based on both Poisson regression and Cox model. Time dependent modifying factors were investigated by adding an interaction term in the model or by using exposure time windows. The cohort includes 36, 769 workers, followed-up until age 60 in average. During the 1968- 2004 period, 5, 443 deaths, 2, 213 cancers, 62 leukemia and 1, 314 cardiovascular diseases were recorded. Among the 57% exposed workers, the mean cumulative dose was 21.5 milli-sieverts (mSv). A strong Healthy Worker Effect is observed in the cohort. Significant elevated risks of pleura cancer and melanoma deaths were observed in the cohort but not associated with dose. No significant association was observed with solid cancers, lung cancer and cardiovascular diseases. A significant dose-response relationship was observed for leukemia excluding chronic lymphatic leukemia, mainly for doses received less than 15 years before and for yearly dose rates higher than 10 mSv. This PhD work contributes to the evaluation of risks associated to chronic external radiation

The importance of age dependent mortality and the extrinsic incubation period in models of mosquito-borne disease transmission and control.

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Steve E Bellan

2010-04-01

Full Text Available Nearly all mathematical models of vector-borne diseases have assumed that vectors die at constant rates. However, recent empirical research suggests that mosquito mortality rates are frequently age dependent. This work develops a simple mathematical model to assess how relaxing the classical assumption of constant mortality affects the predicted effectiveness of anti-vectorial interventions. The effectiveness of mosquito control when mosquitoes die at age dependent rates was also compared across different extrinsic incubation periods. Compared to a more realistic age dependent model, constant mortality models overestimated the sensitivity of disease transmission to interventions that reduce mosquito survival. Interventions that reduce mosquito survival were also found to be slightly less effective when implemented in systems with shorter EIPs. Future transmission models that examine anti-vectorial interventions should incorporate realistic age dependent mortality rates.

Readmissions after Hospitalization for Heart Failure, Acute Myocardial Infarction, or Pneumonia among Young and Middle-Aged Adults: A Retrospective Observational Cohort Study

Science.gov (United States)

Ranasinghe, Isuru; Wang, Yongfei; Dharmarajan, Kumar; Hsieh, Angela F.; Bernheim, Susannah M.; Krumholz, Harlan M.

2014-01-01

Background Patients aged ≥65 years are vulnerable to readmissions due to a transient period of generalized risk after hospitalization. However, whether young and middle-aged adults share a similar risk pattern is uncertain. We compared the rate, timing, and readmission diagnoses following hospitalization for heart failure (HF), acute myocardial infarction (AMI), and pneumonia among patients aged 18–64 years with patients aged ≥65 years. Methods and Findings We used an all-payer administrative dataset from California consisting of all hospitalizations for HF (n = 206,141), AMI (n = 107,256), and pneumonia (n = 199,620) from 2007–2009. The primary outcomes were unplanned 30-day readmission rate, timing of readmission, and readmission diagnoses. Our findings show that the readmission rate among patients aged 18–64 years exceeded the readmission rate in patients aged ≥65 years in the HF cohort (23.4% vs. 22.0%, preadmission risk in patients aged 18–64 years was similar to patients ≥65 years in the HF (HR 0.99; 95%CI 0.97–1.02) and pneumonia (HR 0.97; 95%CI 0.94–1.01) cohorts and was marginally lower in the AMI cohort (HR 0.92; 95%CI 0.87–0.96). For all cohorts, the timing of readmission was similar; readmission risks were highest between days 2 and 5 and declined thereafter across all age groups. Diagnoses other than the index admission diagnosis accounted for a substantial proportion of readmissions among age groups readmissions in the HF cohort and 37–45% of readmissions in the AMI cohort, while a non-pulmonary diagnosis represented 61–64% of patients in the pneumonia cohort. Conclusion When adjusted for differences in patient characteristics, young and middle-aged adults have 30-day readmission rates that are similar to elderly patients for HF, AMI, and pneumonia. A generalized risk after hospitalization is present regardless of age. Please see later in the article for the Editors' Summary PMID:25268126

Bayesian log-periodic model for financial crashes

DEFF Research Database (Denmark)

Rodríguez-Caballero, Carlos Vladimir; Knapik, Oskar

2014-01-01

This paper introduces a Bayesian approach in econophysics literature about financial bubbles in order to estimate the most probable time for a financial crash to occur. To this end, we propose using noninformative prior distributions to obtain posterior distributions. Since these distributions...... cannot be performed analytically, we develop a Markov Chain Monte Carlo algorithm to draw from posterior distributions. We consider three Bayesian models that involve normal and Student’s t-distributions in the disturbances and an AR(1)-GARCH(1,1) structure only within the first case. In the empirical...... part of the study, we analyze a well-known example of financial bubble – the S&P 500 1987 crash – to show the usefulness of the three methods under consideration and crashes of Merval-94, Bovespa-97, IPCMX-94, Hang Seng-97 using the simplest method. The novelty of this research is that the Bayesian...

Linear and Generalized Linear Mixed Models and Their Applications

CERN Document Server

Jiang, Jiming

2007-01-01

This book covers two major classes of mixed effects models, linear mixed models and generalized linear mixed models, and it presents an up-to-date account of theory and methods in analysis of these models as well as their applications in various fields. The book offers a systematic approach to inference about non-Gaussian linear mixed models. Furthermore, it has included recently developed methods, such as mixed model diagnostics, mixed model selection, and jackknife method in the context of mixed models. The book is aimed at students, researchers and other practitioners who are interested

Associations of linear growth and relative weight gain during early life with adult health and human capital in countries of low and middle income: findings from five birth cohort studies.

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Adair, Linda S; Fall, Caroline H D; Osmond, Clive; Stein, Aryeh D; Martorell, Reynaldo; Ramirez-Zea, Manuel; Sachdev, Harshpal Singh; Dahly, Darren L; Bas, Isabelita; Norris, Shane A; Micklesfield, Lisa; Hallal, Pedro; Victora, Cesar G

2013-08-10

Fast weight gain and linear growth in children in low-income and middle-income countries are associated with enhanced survival and improved cognitive development, but might increase risk of obesity and related adult cardiometabolic diseases. We investigated how linear growth and relative weight gain during infancy and childhood are related to health and human capital outcomes in young adults. We used data from five prospective birth cohort studies from Brazil, Guatemala, India, the Philippines, and South Africa. We investigated body-mass index, systolic and diastolic blood pressure, plasma glucose concentration, height, years of attained schooling, and related categorical indicators of adverse outcomes in young adults. With linear and logistic regression models, we assessed how these outcomes relate to birthweight and to statistically independent measures representing linear growth and weight gain independent of linear growth (relative weight gain) in three age periods: 0-2 years, 2 years to mid-childhood, and mid-childhood to adulthood. We obtained data for 8362 participants who had at least one adult outcome of interest. A higher birthweight was consistently associated with an adult body-mass index of greater than 25 kg/m(2) (odds ratio 1·28, 95% CI 1·21-1·35) and a reduced likelihood of short adult stature (0·49, 0·44-0·54) and of not completing secondary school (0·82, 0·78-0·87). Faster linear growth was strongly associated with a reduced risk of short adult stature (age 2 years: 0·23, 0·20-0·52; mid-childhood: 0·39, 0·36-0·43) and of not completing secondary school (age 2 years: 0·74, 0·67-0·78; mid-childhood: 0·87, 0·83-0·92), but did raise the likelihood of overweight (age 2 years: 1·24, 1·17-1·31; mid-childhood: 1·12, 1·06-1·18) and elevated blood pressure (age 2 years: 1·12, 1·06-1·19; mid-childhood: 1·07, 1·01-1·13). Faster relative weight gain was associated with an increased risk of adult overweight (age 2 years: 1·51

Does the Spectrum model accurately predict trends in adult mortality? Evaluation of model estimates using empirical data from a rural HIV community cohort study in north-western Tanzania

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Denna Michael

2014-01-01

Full Text Available Introduction: Spectrum epidemiological models are used by UNAIDS to provide global, regional and national HIV estimates and projections, which are then used for evidence-based health planning for HIV services. However, there are no validations of the Spectrum model against empirical serological and mortality data from populations in sub-Saharan Africa. Methods: Serologic, demographic and verbal autopsy data have been regularly collected among over 30,000 residents in north-western Tanzania since 1994. Five-year age-specific mortality rates (ASMRs per 1,000 person years and the probability of dying between 15 and 60 years of age (45Q15, were calculated and compared with the Spectrum model outputs. Mortality trends by HIV status are shown for periods before the introduction of antiretroviral therapy (1994–1999, 2000–2005 and the first 5 years afterwards (2005–2009. Results: Among 30–34 year olds of both sexes, observed ASMRs per 1,000 person years were 13.33 (95% CI: 10.75–16.52 in the period 1994–1999, 11.03 (95% CI: 8.84–13.77 in 2000–2004, and 6.22 (95% CI; 4.75–8.15 in 2005–2009. Among the same age group, the ASMRs estimated by the Spectrum model were 10.55, 11.13 and 8.15 for the periods 1994–1999, 2000–2004 and 2005–2009, respectively. The cohort data, for both sexes combined, showed that the 45Q15 declined from 39% (95% CI: 27–55% in 1994 to 22% (95% CI: 17–29% in 2009, whereas the Spectrum model predicted a decline from 43% in 1994 to 37% in 2009. Conclusion: From 1994 to 2009, the observed decrease in ASMRs was steeper in younger age groups than that predicted by the Spectrum model, perhaps because the Spectrum model under-estimated the ASMRs in 30–34 year olds in 1994–99. However, the Spectrum model predicted a greater decrease in 45Q15 mortality than observed in the cohort, although the reasons for this over-estimate are unclear.

Guidance for the utility of linear models in meta-analysis of genetic association studies of binary phenotypes.

Science.gov (United States)

Cook, James P; Mahajan, Anubha; Morris, Andrew P

2017-02-01

Linear mixed models are increasingly used for the analysis of genome-wide association studies (GWAS) of binary phenotypes because they can efficiently and robustly account for population stratification and relatedness through inclusion of random effects for a genetic relationship matrix. However, the utility of linear (mixed) models in the context of meta-analysis of GWAS of binary phenotypes has not been previously explored. In this investigation, we present simulations to compare the performance of linear and logistic regression models under alternative weighting schemes in a fixed-effects meta-analysis framework, considering designs that incorporate variable case-control imbalance, confounding factors and population stratification. Our results demonstrate that linear models can be used for meta-analysis of GWAS of binary phenotypes, without loss of power, even in the presence of extreme case-control imbalance, provided that one of the following schemes is used: (i) effective sample size weighting of Z-scores or (ii) inverse-variance weighting of allelic effect sizes after conversion onto the log-odds scale. Our conclusions thus provide essential recommendations for the development of robust protocols for meta-analysis of binary phenotypes with linear models.

VT Route Log Points 2017

Data.gov (United States)

Vermont Center for Geographic Information — This data layer is used with VTrans' Integrated Route Log System (IRA). It is also used to calibrate the linear referencing systems, including the End-to-End and...

Linear viscoelastic properties of aging suspensions

NARCIS (Netherlands)

Purnomo, E.H.; Purnomo, E.H; van den Ende, Henricus T.M.; Mellema, J.; Mugele, Friedrich Gunther

2006-01-01

We have examined the linear viscoelastic behavior of poly-N-isopropylacrylamide (PNIPAM) microgel suspensions in order to obtain insight in the aging processes in these densely packed suspensions at various temperatures below the volume transition temperature. The system is found to display a strong

Childhood maltreatment and BMI trajectories to mid-adult life: follow-up to age 50 y in a British birth cohort.

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Chris Power

Full Text Available Childhood maltreatment including abuse and neglect has been associated with adult obesity, but evidence on life-course development of obesity or BMI gain is unclear. We aim to establish whether childhood maltreatments are related to obesity or BMI at different life-stages 7 y-50 y and to identify possible explanations for associations.Childhood physical, psychological and sexual abuse, neglect and BMI at seven ages were recorded in the 1958 birth cohort (n~15,000. Associations of child maltreatments with BMI at separate ages were tested using linear regression or logistic regression for obesity, and with rate of child-to-adult BMI gain using multilevel models. We adjusted for potential covariates.Abuse was reported in ~12% of the population. Abuse was not associated with elevated childhood BMI, but adult associations were observed: i.e. the abused had faster child-adult BMI gain than the non-abused; associations were independent of adult covariates. For physical abuse in both genders there was a positive linear association of ~0.006/y zBMI gain with age after adjustment for all covariates. Similarly, there was a linear association of physical abuse with obesity risk: e.g. among females from a low OR(adjusted of 0.34 (0.16,0.71 at 7 y to 1.67 (1.25,2.24 at 50 y. In females faster zBMI gains with age of ~0.0034/y were observed for sexual abuse and increases in obesity risk were faster: from a low OR(adjusted of 0.23 (0.06,0.84 at 7 y to 1.34 (0.86,2.10 at 50 y. Psychological abuse and neglect associations were less consistent.Childhood maltreatment associations with BMI or obesity varied across life: physical and, in females, sexual abuse were associated with faster lifetime BMI gains, which may have detrimental long-term health consequences.

A penalized framework for distributed lag non-linear models.

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Gasparrini, Antonio; Scheipl, Fabian; Armstrong, Ben; Kenward, Michael G

2017-09-01

Distributed lag non-linear models (DLNMs) are a modelling tool for describing potentially non-linear and delayed dependencies. Here, we illustrate an extension of the DLNM framework through the use of penalized splines within generalized additive models (GAM). This extension offers built-in model selection procedures and the possibility of accommodating assumptions on the shape of the lag structure through specific penalties. In addition, this framework includes, as special cases, simpler models previously proposed for linear relationships (DLMs). Alternative versions of penalized DLNMs are compared with each other and with the standard unpenalized version in a simulation study. Results show that this penalized extension to the DLNM class provides greater flexibility and improved inferential properties. The framework exploits recent theoretical developments of GAMs and is implemented using efficient routines within freely available software. Real-data applications are illustrated through two reproducible examples in time series and survival analysis. © 2017 The Authors Biometrics published by Wiley Periodicals, Inc. on behalf of International Biometric Society.

Associations between maternal long-chain polyunsaturated fatty acid concentrations and child cognition at 7 years of age: The MEFAB birth cohort.

Science.gov (United States)

Brouwer-Brolsma, E M; van de Rest, O; Godschalk, R; Zeegers, M P A; Gielen, M; de Groot, R H M

2017-11-01

Concentrations of the fish fatty acids EPA and DHA are low among Dutch women of reproductive age. As the human brain incorporates high concentrations of these fatty acids in utero, particularly during third trimester of gestation, these low EPA and DHA concentrations may have adverse consequences for fetal brain development and functioning. Analyses were conducted using longitudinal observational data of 292 mother-child pairs participating in the MEFAB cohort. Maternal AA, DHA, and EPA were determined in plasma phospholipids - obtained in three trimesters - by gas-liquid chromatography. Cognitive function was assessed at 7 years of age, using the Kaufman Assessment Battery for Children, resulting in three main outcome parameters: sequential processing (short-term memory), simultaneous processing (problem-solving skills), and the mental processing composite score. Spline regression and linear regression analyses were used to analyse the data, while adjusting for potential relevant covariates. Only 2% of the children performed more than one SD below the mental processing composite norm score. Children with lower test scores (children with higher test scores (≥25%). Fully-adjusted linear regression models did not show associations of maternal AA, DHA, or EPA status during any of the pregnancy trimesters with childhood sequential and simultaneous processing. Maternal fatty acid status during pregnancy was not associated with cognitive performance in Dutch children at age 7. Copyright © 2017 Elsevier Ltd. All rights reserved.

Long sleep duration is associated with lower cognitive function among middle-age adults - the Doetinchem Cohort Study.

Science.gov (United States)

van Oostrom, Sandra H; Nooyens, Astrid C J; van Boxtel, Martin P J; Verschuren, W M Monique

2018-01-01

In older adults, both short and long sleep duration are associated with lower cognitive function, suggesting an inverted U-shaped association between sleep duration and cognitive outcomes. This study examined whether sleep duration is associated with (changes in) cognitive function in a middle-aged population. In the Doetinchem Cohort Study, the cognitive function of 2970 men and women aged 41-75 years at baseline (1995-2007) was examined 2-3 times, with 5-year time intervals. Global cognitive function and the domains memory, information processing speed, and cognitive flexibility were assessed. In multivariable linear regression models, (change in) self-reported sleep duration was studied in association with the level and change in cognitive function. In a subsample of the population (n = 2587), the association of sleep duration and feeling rested with cognitive function was studied. Sleep duration of 9 h and more was statistically significantly associated with lower global cognitive function (p cognitive function. An inverted U-shaped association between sleep duration and cognitive function was observed for speed, flexibility, and global cognitive function. Sleep duration was not associated with change in cognitive function. Middle-age adults with long sleep duration had a lower cognitive function. Copyright © 2017 The Authors. Published by Elsevier B.V. All rights reserved.

Temporal diagnostic analysis of the SWAT model to detect dominant periods of poor model performance

Science.gov (United States)

Guse, Björn; Reusser, Dominik E.; Fohrer, Nicola

2013-04-01

Hydrological models generally include thresholds and non-linearities, such as snow-rain-temperature thresholds, non-linear reservoirs, infiltration thresholds and the like. When relating observed variables to modelling results, formal methods often calculate performance metrics over long periods, reporting model performance with only few numbers. Such approaches are not well suited to compare dominating processes between reality and model and to better understand when thresholds and non-linearities are driving model results. We present a combination of two temporally resolved model diagnostic tools to answer when a model is performing (not so) well and what the dominant processes are during these periods. We look at the temporal dynamics of parameter sensitivities and model performance to answer this question. For this, the eco-hydrological SWAT model is applied in the Treene lowland catchment in Northern Germany. As a first step, temporal dynamics of parameter sensitivities are analyzed using the Fourier Amplitude Sensitivity test (FAST). The sensitivities of the eight model parameters investigated show strong temporal variations. High sensitivities were detected for two groundwater (GW_DELAY, ALPHA_BF) and one evaporation parameters (ESCO) most of the time. The periods of high parameter sensitivity can be related to different phases of the hydrograph with dominances of the groundwater parameters in the recession phases and of ESCO in baseflow and resaturation periods. Surface runoff parameters show high parameter sensitivities in phases of a precipitation event in combination with high soil water contents. The dominant parameters give indication for the controlling processes during a given period for the hydrological catchment. The second step included the temporal analysis of model performance. For each time step, model performance was characterized with a "finger print" consisting of a large set of performance measures. These finger prints were clustered into

Mixed integer linear programming model for dynamic supplier selection problem considering discounts

Directory of Open Access Journals (Sweden)

Adi Wicaksono Purnawan

2018-01-01

Full Text Available Supplier selection is one of the most important elements in supply chain management. This function involves evaluation of many factors such as, material costs, transportation costs, quality, delays, supplier capacity, storage capacity and others. Each of these factors varies with time, therefore, supplier identified for one period is not necessarily be same for the next period to supply the same product. So, mixed integer linear programming (MILP was developed to overcome the dynamic supplier selection problem (DSSP. In this paper, a mixed integer linear programming model is built to solve the lot-sizing problem with multiple suppliers, multiple periods, multiple products and quantity discounts. The buyer has to make a decision for some products which will be supplied by some suppliers for some periods cosidering by discount. To validate the MILP model with randomly generated data. The model is solved by Lingo 16.

Modelling subject-specific childhood growth using linear mixed-effect models with cubic regression splines.

Science.gov (United States)

Grajeda, Laura M; Ivanescu, Andrada; Saito, Mayuko; Crainiceanu, Ciprian; Jaganath, Devan; Gilman, Robert H; Crabtree, Jean E; Kelleher, Dermott; Cabrera, Lilia; Cama, Vitaliano; Checkley, William

2016-01-01

Childhood growth is a cornerstone of pediatric research. Statistical models need to consider individual trajectories to adequately describe growth outcomes. Specifically, well-defined longitudinal models are essential to characterize both population and subject-specific growth. Linear mixed-effect models with cubic regression splines can account for the nonlinearity of growth curves and provide reasonable estimators of population and subject-specific growth, velocity and acceleration. We provide a stepwise approach that builds from simple to complex models, and account for the intrinsic complexity of the data. We start with standard cubic splines regression models and build up to a model that includes subject-specific random intercepts and slopes and residual autocorrelation. We then compared cubic regression splines vis-à-vis linear piecewise splines, and with varying number of knots and positions. Statistical code is provided to ensure reproducibility and improve dissemination of methods. Models are applied to longitudinal height measurements in a cohort of 215 Peruvian children followed from birth until their fourth year of life. Unexplained variability, as measured by the variance of the regression model, was reduced from 7.34 when using ordinary least squares to 0.81 (p linear mixed-effect models with random slopes and a first order continuous autoregressive error term. There was substantial heterogeneity in both the intercept (p modeled with a first order continuous autoregressive error term as evidenced by the variogram of the residuals and by a lack of association among residuals. The final model provides a parametric linear regression equation for both estimation and prediction of population- and individual-level growth in height. We show that cubic regression splines are superior to linear regression splines for the case of a small number of knots in both estimation and prediction with the full linear mixed effect model (AIC 19,352 vs. 19

Dietary Pattern Trajectories from 6 to 12 Months of Age in a Multi-Ethnic Asian Cohort.

Science.gov (United States)

Lim, Geraldine Huini; Toh, Jia Ying; Aris, Izzuddin M; Chia, Ai-Ru; Han, Wee Meng; Saw, Seang Mei; Godfrey, Keith M; Gluckman, Peter D; Chong, Yap-Seng; Yap, Fabian; Lee, Yung Seng; Kramer, Michael S; Chong, Mary Foong-Fong

2016-06-15

Little is known about the dietary patterns of Asian infants in the first year of life, nor of their associations with maternal socio-demographic factors. Based on the Growing Up in Singapore towards healthy Outcomes (GUSTO) mother-offspring cohort, cross-sectional dietary patterns were derived by factor analysis using 24-h recalls and food diaries of infants at 6-, 9- and 12-months of age. Dietary pattern trajectories were modeled by mapping similar dietary patterns across each age using multilevel mixed models. Associations with maternal socio-demographic variables, collected through questionnaires during pregnancy, were assessed using general linear models. In n = 486 infants, four dietary pattern trajectories were established from 6- to 12-months. Predominantly breastmilk: mainly breastmilk and less formula milk, rice porridge, vegetables, fruits and low-fat fish and meat, Easy-to-prepare foods: infant cereals, juices, cakes and biscuits and Noodles (in soup) and seafood: noodle and common accompaniments. In adjusted models, higher maternal education attainment was correlated with higher start scores on Predominantly breastmilk, but lowest education attainment increased its adherence over time. Older mothers had higher start scores on Easy-to-prepare foods, but younger mothers had increased adherence over time. Chinese mothers had higher start scores on Predominantly breastmilk but greater adherence to GUIDELINES over time, while Indian mothers had higher start scores on Easy-to-prepare foods but greater adherence to Predominantly breastmilk with time (p dietary patterns established during weaning are strongly influenced by maternal socio-demographic factors and remain stable over the first year of life.

Teasing apart the relations between age, birth cohort, and vocational interests.

Science.gov (United States)

Leuty, Melanie E; Hansen, Jo-Ida C

2014-04-01

Empirical evidence supports that aging is related to differences in work attitudes and motivation (Inceoglu, Segers, & Bartram, 2012; Kooij, de Lange, Jansen, Kanfer, & Kikkers, 2011; Ng & Feldman, 2008, 2010), but little research has explored the relations between age and vocational interests. Furthermore, recent studies of age and work attitudes suggest that generational experiences (i.e., birth year) may account for age differences in the workplace (Inceoglu et al., 2012; Ng & Feldman, 2008, 2010), which in turn suggests that researchers need to incorporate both age and birth cohort effects in their designs. Thus, this study was designed to explore the relations of age at the time of testing and birth year to vocational interests using a sample of adults (N = 1,792) collected over a period of 3 decades. As expected, age was not a significant predictor of most interests, but birth year also was not found to predict most interests, with the significant prediction of Realistic interests by both age and birth year being the exception. Gender, however, significantly predicted most areas of interests. Neither age nor gender moderated any relationships between birth year and interests. Results suggest that birth year and age were minimally related to interests as all effect sizes were small. Discussion of the results illustrates the need for further research on this issue and also offers considerations for attracting and retaining different generations of workers in light of the findings. (PsycINFO Database Record (c) 2014 APA, all rights reserved).

Linear and non-linear quantitative structure-activity relationship models on indole substitution patterns as inhibitors of HIV-1 attachment.

Science.gov (United States)

Nirouei, Mahyar; Ghasemi, Ghasem; Abdolmaleki, Parviz; Tavakoli, Abdolreza; Shariati, Shahab

2012-06-01

The antiviral drugs that inhibit human immunodeficiency virus (HIV) entry to the target cells are already in different phases of clinical trials. They prevent viral entry and have a highly specific mechanism of action with a low toxicity profile. Few QSAR studies have been performed on this group of inhibitors. This study was performed to develop a quantitative structure-activity relationship (QSAR) model of the biological activity of indole glyoxamide derivatives as inhibitors of the interaction between HIV glycoprotein gp120 and host cell CD4 receptors. Forty different indole glyoxamide derivatives were selected as a sample set and geometrically optimized using Gaussian 98W. Different combinations of multiple linear regression (MLR), genetic algorithms (GA) and artificial neural networks (ANN) were then utilized to construct the QSAR models. These models were also utilized to select the most efficient subsets of descriptors in a cross-validation procedure for non-linear log (1/EC50) prediction. The results that were obtained using GA-ANN were compared with MLR-MLR and MLR-ANN models. A high predictive ability was observed for the MLR, MLR-ANN and GA-ANN models, with root mean sum square errors (RMSE) of 0.99, 0.91 and 0.67, respectively (N = 40). In summary, machine learning methods were highly effective in designing QSAR models when compared to statistical method.

Modeling Interdependent and Periodic Real-World Action Sequences

Science.gov (United States)

Kurashima, Takeshi; Althoff, Tim; Leskovec, Jure

2018-01-01

Mobile health applications, including those that track activities such as exercise, sleep, and diet, are becoming widely used. Accurately predicting human actions in the real world is essential for targeted recommendations that could improve our health and for personalization of these applications. However, making such predictions is extremely difficult due to the complexities of human behavior, which consists of a large number of potential actions that vary over time, depend on each other, and are periodic. Previous work has not jointly modeled these dynamics and has largely focused on item consumption patterns instead of broader types of behaviors such as eating, commuting or exercising. In this work, we develop a novel statistical model, called TIPAS, for Time-varying, Interdependent, and Periodic Action Sequences. Our approach is based on personalized, multivariate temporal point processes that model time-varying action propensities through a mixture of Gaussian intensities. Our model captures short-term and long-term periodic interdependencies between actions through Hawkes process-based self-excitations. We evaluate our approach on two activity logging datasets comprising 12 million real-world actions (e.g., eating, sleep, and exercise) taken by 20 thousand users over 17 months. We demonstrate that our approach allows us to make successful predictions of future user actions and their timing. Specifically, TIPAS improves predictions of actions, and their timing, over existing methods across multiple datasets by up to 156%, and up to 37%, respectively. Performance improvements are particularly large for relatively rare and periodic actions such as walking and biking, improving over baselines by up to 256%. This demonstrates that explicit modeling of dependencies and periodicities in real-world behavior enables successful predictions of future actions, with implications for modeling human behavior, app personalization, and targeting of health interventions. PMID

Modelling binary data

CERN Document Server

Collett, David

2002-01-01

INTRODUCTION Some Examples The Scope of this Book Use of Statistical Software STATISTICAL INFERENCE FOR BINARY DATA The Binomial Distribution Inference about the Success Probability Comparison of Two Proportions Comparison of Two or More Proportions MODELS FOR BINARY AND BINOMIAL DATA Statistical Modelling Linear Models Methods of Estimation Fitting Linear Models to Binomial Data Models for Binomial Response Data The Linear Logistic Model Fitting the Linear Logistic Model to Binomial Data Goodness of Fit of a Linear Logistic Model Comparing Linear Logistic Models Linear Trend in Proportions Comparing Stimulus-Response Relationships Non-Convergence and Overfitting Some other Goodness of Fit Statistics Strategy for Model Selection Predicting a Binary Response Probability BIOASSAY AND SOME OTHER APPLICATIONS The Tolerance Distribution Estimating an Effective Dose Relative Potency Natural Response Non-Linear Logistic Regression Models Applications of the Complementary Log-Log Model MODEL CHECKING Definition of Re...

Numerical proceessing of radioimmunoassay results using logit-log transformation method

International Nuclear Information System (INIS)

Textoris, R.

1983-01-01

The mathematical model and algorithm are described of the numerical processing of the results of a radioimmunoassay by the logit-log transformation method and by linear regression with weight factors. The limiting value of the curve for zero concentration is optimized with regard to the residual sum by the iterative method by multiple repeats of the linear regression. Typical examples are presented of the approximation of calibration curves. The method proved suitable for all hitherto used RIA sets and is well suited for small computers with internal memory of min. 8 Kbyte. (author)

Pulsed neutron generator for logging

International Nuclear Information System (INIS)

Thibideau, F.D.

1977-01-01

A pulsed neutron generator for uranium logging is described. This generator is one component of a prototype uranium logging probe which is being developed by SLA to detect, and assay, uranium by borehole logging. The logging method is based on the measurement of epithermal neutrons resulting from the prompt fissioning of uranium from a pulsed source of 17.6 MeV neutrons. An objective of the prototype probe was that its diameter not exceed 2.75 inches, which would allow its use in conventional rotary drill holes of 4.75-inch diameter. This restriction limited the generator to a maximum 2.375-inch diameter. The performance requirements for the neutron generator specified that it operate with a nominal output of 5 x 10 6 neutrons/pulse at up to 100 pulses/second for a one-hour period. The development of a neutron generator meeting the preliminary design goals was completed and two prototype models were delivered to SLA. These two generators have been used by SLA to log a number of boreholes in field evaluation of the probe. The results of the field evaluations have led to the recommendation of several changes to improve the probe's operation. Some of these changes will require additional development effort on the neutron generator. It is expected that this work will be performed during 1977. The design and operation of the first prototype neutron generators is described

Dimension of linear models

DEFF Research Database (Denmark)

Høskuldsson, Agnar

1996-01-01

Determination of the proper dimension of a given linear model is one of the most important tasks in the applied modeling work. We consider here eight criteria that can be used to determine the dimension of the model, or equivalently, the number of components to use in the model. Four of these cri......Determination of the proper dimension of a given linear model is one of the most important tasks in the applied modeling work. We consider here eight criteria that can be used to determine the dimension of the model, or equivalently, the number of components to use in the model. Four...... the basic problems in determining the dimension of linear models. Then each of the eight measures are treated. The results are illustrated by examples....

Extending the linear model with R generalized linear, mixed effects and nonparametric regression models

CERN Document Server

Faraway, Julian J

2005-01-01

Linear models are central to the practice of statistics and form the foundation of a vast range of statistical methodologies. Julian J. Faraway''s critically acclaimed Linear Models with R examined regression and analysis of variance, demonstrated the different methods available, and showed in which situations each one applies. Following in those footsteps, Extending the Linear Model with R surveys the techniques that grow from the regression model, presenting three extensions to that framework: generalized linear models (GLMs), mixed effect models, and nonparametric regression models. The author''s treatment is thoroughly modern and covers topics that include GLM diagnostics, generalized linear mixed models, trees, and even the use of neural networks in statistics. To demonstrate the interplay of theory and practice, throughout the book the author weaves the use of the R software environment to analyze the data of real examples, providing all of the R commands necessary to reproduce the analyses. All of the ...

Validation of the periodicity of growth increment deposition in ...

African Journals Online (AJOL)

Validation of the periodicity of growth increment deposition in otoliths from the larval and early juvenile stages of two cyprinids from the Orange–Vaal river ... Linear regression models were fitted to the known age post-fertilisation and the age estimated using increment counts to test the correspondence between the two for ...

A primer on linear models

CERN Document Server

Monahan, John F

2008-01-01

Preface Examples of the General Linear Model Introduction One-Sample Problem Simple Linear Regression Multiple Regression One-Way ANOVA First Discussion The Two-Way Nested Model Two-Way Crossed Model Analysis of Covariance Autoregression Discussion The Linear Least Squares Problem The Normal Equations The Geometry of Least Squares Reparameterization Gram-Schmidt Orthonormalization Estimability and Least Squares Estimators Assumptions for the Linear Mean Model Confounding, Identifiability, and Estimability Estimability and Least Squares Estimators F

High resolution gamma spectroscopy well logging system

International Nuclear Information System (INIS)

Giles, J.R.; Dooley, K.J.

1997-01-01

A Gamma Spectroscopy Logging System (GSLS) has been developed to study sub-surface radionuclide contamination. The absolute counting efficiencies of the GSLS detectors were determined using cylindrical reference sources. More complex borehole geometries were modeled using commercially available shielding software and correction factors were developed based on relative gamma-ray fluence rates. Examination of varying porosity and moisture content showed that as porosity increases, and as the formation saturation ratio decreases, relative gamma-ray fluence rates increase linearly for all energies. Correction factors for iron and water cylindrical shields were found to agree well with correction factors determined during previous studies allowing for the development of correction factors for type-304 stainless steel and low-carbon steel casings. Regression analyses of correction factor data produced equations for determining correction factors applicable to spectral gamma-ray well logs acquired under non-standard borehole conditions

Loneliness and the rate of motor decline in old age: the rush memory and aging project, a community-based cohort study

Directory of Open Access Journals (Sweden)

Arnold Steven E

2010-10-01

Full Text Available Abstract Background Being alone, as measured by less frequent social interactions, has been reported to be associated with a more rapid rate of motor decline in older persons. We tested the hypothesis that feeling alone is associated with the rate of motor decline in community-dwelling older persons. Methods At baseline, loneliness was assessed with a 5-item scale in 985 persons without dementia participating in the Rush Memory and Aging Project, a longitudinal community-based cohort study. Annual detailed assessment of 9 measures of muscle strength and 9 motor performances were summarized in a composite measure of global motor function. Results Linear mixed-effects models which controlled for age, sex and education, showed that the level of loneliness at baseline was associated with the rate of motor decline (Estimate, -0.016; S.E. 0.006, p = 0.005. For each 1-point higher level of loneliness at baseline, motor decline was 40% more rapid; this effect was similar to the rate of motor decline observed in an average participant 4 years older at baseline. Furthermore, this amount of motor decline per year was associated with about a 50% increased risk of death. When terms for both feeling alone (loneliness and being alone were considered together in a single model, both were relatively independent predictors of motor decline. The association between loneliness and motor decline persisted even after controlling for depressive symptoms, cognition, physical and cognitive activities, chronic conditions, as well as baseline disability or a history of stroke or Parkinson's disease. Conclusions Among community-dwelling older persons, both feeling alone and being alone are associated with more rapid motor decline, underscoring the importance of psychosocial factors and motor decline in old age.

Self-esteem development from young adulthood to old age: a cohort-sequential longitudinal study.

Science.gov (United States)

Orth, Ulrich; Trzesniewski, Kali H; Robins, Richard W

2010-04-01

The authors examined the development of self-esteem from young adulthood to old age. Data came from the Americans' Changing Lives study, which includes 4 assessments across a 16-year period of a nationally representative sample of 3,617 individuals aged 25 years to 104 years. Latent growth curve analyses indicated that self-esteem follows a quadratic trajectory across the adult life span, increasing during young and middle adulthood, reaching a peak at about age 60 years, and then declining in old age. No cohort differences in the self-esteem trajectory were found. Women had lower self-esteem than did men in young adulthood, but their trajectories converged in old age. Whites and Blacks had similar trajectories in young and middle adulthood, but the self-esteem of Blacks declined more sharply in old age than did the self-esteem of Whites. More educated individuals had higher self-esteem than did less educated individuals, but their trajectories were similar. Moreover, the results suggested that changes in socioeconomic status and physical health account for the decline in self-esteem that occurs in old age.

Centenarians - a useful model for healthy aging?

DEFF Research Database (Denmark)

Engberg, Henriette; Oksuzyan, Anna; Jeune, Bernard

2009-01-01

Centenarians surpass the current human life expectancy with about 20-25 years. However, whether centenarians represent healthy aging still remains an open question. Previous studies have been hampered by a number of methodological shortcomings such as a cross-sectional design and lack...... of an appropriate control group. In a longitudinal population-based cohort, it was examined whether the centenarian phenotype may be a useful model for healthy aging. The study was based on a completefollow up of 39 945 individuals alive in the Danish 1905 birth cohort on January 1, 1977 identified through...... with 68.4% among individuals who died in their early 80s. This trend was evident in both sexes. As a result of their lower hospitalization rates and length of stay in hospital compared with their contemporaries, who died at younger ages, Danish centenarians represent healthy agers. Centenarians constitute...

Testicular cancer: marked birth cohort effects on incidence and a decline in mortality in southern Netherlands since 1970.

Science.gov (United States)

Verhoeven, Rob; Houterman, Saskia; Kiemeney, Bart; Koldewijn, Evert; Coebergh, Jan Willem

2008-02-01

The aim of our study was to interpret the changing incidence, and to describe the mortality of patients with testicular cancer in the south of the Netherlands between 1970 and 2004. On the basis of data from the Eindhoven Cancer Registry and Statistics Netherlands, 5-year moving average standardised incidence and mortality rates were calculated. An age-period-cohort (APC) Poisson regression analysis was performed to disentangle time and birth cohort effects on incidence. The incidence rate remained stable for all ages at about 3 per 100,000 person-years until 1989 but increased annually thereafter by 4% to 6 in 2004. This increase can almost completely be attributed to an increase in localised tumours. The largest increase was found for seminoma testicular cancer (TC) patients aged 35-39 and non-seminoma TC patients aged 20-24 years. Relatively more localised and tumours with lymph node metastases were detected in the later periods. APC analysis showed the best fit with an age-cohort model. An increase in incidence of TC was found for birth cohorts since 1950. The mortality rate dropped from 1.0 per 100,000 person-years in 1970 to 0.3 in 2005, with a steep annual decline of 12% in the period 1979-1986. In conclusion, the increase in incidence of TC was strongly correlated with birth cohorts since 1945. The increase in incidence is possibly caused by in utero or early life exposure to a yet unknown risk factor. There was a steep decline in mortality in the period 1979-1986. (c) 2007 Wiley-Liss, Inc.

Interpretation of horizontal well production logs: influence of logging tool

Energy Technology Data Exchange (ETDEWEB)

Ozkan, E. [Colorado School of Mines, Boulder, CO (United States); Sarica, C. [Pennsylvania State Univ., College Park, PA (United States); Haci, M. [Drilling Measurements, Inc (United States)

1998-12-31

The influence of a production-logging tool on wellbore flow rate and pressure measurements was investigated, focusing on the disturbence caused by the production-logging tool and the coiled tubing on the original flow conditions in the wellbore. The investigation was carried out using an analytical model and single-phase liquid flow was assumed. Results showed that the production-logging tool influenced the measurements as shown by the deviation of the original flow-rate, pressure profiles and low-conductivity wellbores. High production rates increase the effect of the production-logging tool. Recovering or inferring the original flow conditions in the wellbore from the production-logging data is a very complex process which cannot be solved easily. For this reason, the conditions under which the information obtained by production-logging is meaningful is of considerable practical interest. 7 refs., 2 tabs., 15 figs.

Missed epidemics and missing links: international birth cohort trends in multiple sclerosis.

Science.gov (United States)

Ajdacic-Gross, V; Tschopp, A; Schmid, M; Bopp, M; Gutzwiller, F

2013-03-01

Many hypotheses on the etiopathogenesis of multiple sclerosis (MS) focus on risk factors occurring early in life. This study examined the variability of birth cohort trends in international MS data by means of age-period-cohort (APC) analysis. The data from 25 countries were taken from the WHO mortality database. Data were encoded according to the International Classification of Diseases and covered slightly varying periods between 1951 and 2009. The APC analyses were based on logit models applied to cohort tables with 5-year age- and period intervals. In most countries, the birth cohort estimates peaked in those born in the first half of the 20th century. In countries from Central and Western Europe, the peak concerned those born before and around 1920. A second group of countries (Denmark, Sweden, Italy, Ireland, Scotland) shared a later peak amongst cohorts born in the 1920s and 1930s. Group 3 included Commonwealth countries, the USA and Norway, with a double or extended peak starting in the 1910s or 1920s, and ending by the 1950s. The fourth group, consisting of Mediterranean countries and Finland, was characterized by a steady increase in the birth cohort estimates until the 1950s. The fifth group with countries from Eastern Europe and Japan showed no particular pattern. Birth cohort trends have influenced the change in MS risk across the 20th century in many Western countries. This silent epidemic points to a most important but unknown latent risk factor in MS. © 2012 The Author(s) European Journal of Neurology © 2012 EFNS.

Estimating stock parameters from trawl cpue-at-age series using year-class curves

NARCIS (Netherlands)

Cotter, A.J.R.; Mesnil, B.; Piet, G.J.

2007-01-01

A year-class curve is a plot of log cpue (catch per unit effort) over age for a single year class of a species (in contrast to the better known catch curve, fitted to multiple year classes at one time). When linear, the intercept and slope estimate the log cpue at age 0 and the average rate of total

Propagation dynamics for a spatially periodic integrodifference competition model

Science.gov (United States)

Wu, Ruiwen; Zhao, Xiao-Qiang

2018-05-01

In this paper, we study the propagation dynamics for a class of integrodifference competition models in a periodic habitat. An interesting feature of such a system is that multiple spreading speeds can be observed, which biologically means different species may have different spreading speeds. We show that the model system admits a single spreading speed, and it coincides with the minimal wave speed of the spatially periodic traveling waves. A set of sufficient conditions for linear determinacy of the spreading speed is also given.

The Meaning of Logs

NARCIS (Netherlands)

Etalle, Sandro; Massacci, Fabio; Yautsiukhin, Artsiom; Lambrinoudakis, Costas; Pernul, Günther; Tjoa, A Min

While logging events is becoming increasingly common in computing, in communication and in collaborative environments, log systems need to satisfy increasingly challenging (if not conflicting) requirements. In this paper we propose a high-level framework for modeling log systems, and reasoning about

Early nasal continuous positive airway pressure in a cohort of the smallest infants in Denmark

DEFF Research Database (Denmark)

Hansen, Bo M; Esbjørn, Barbara Hoff; Greisen, G

2004-01-01

To evaluate neurodevelopmental outcome at age 5 y of age in a cohort of preterm children treated mainly with nasal continuous positive airway pressure (CPAP) in the neonatal period.......To evaluate neurodevelopmental outcome at age 5 y of age in a cohort of preterm children treated mainly with nasal continuous positive airway pressure (CPAP) in the neonatal period....

Application of Hierarchical Linear Models/Linear Mixed-Effects Models in School Effectiveness Research

Science.gov (United States)

Ker, H. W.

2014-01-01

Multilevel data are very common in educational research. Hierarchical linear models/linear mixed-effects models (HLMs/LMEs) are often utilized to analyze multilevel data nowadays. This paper discusses the problems of utilizing ordinary regressions for modeling multilevel educational data, compare the data analytic results from three regression…

A linear solvation energy relationship model of organic chemical partitioning to dissolved organic carbon.

Science.gov (United States)

Kipka, Undine; Di Toro, Dominic M

2011-09-01

Predicting the association of contaminants with both particulate and dissolved organic matter is critical in determining the fate and bioavailability of chemicals in environmental risk assessment. To date, the association of a contaminant to particulate organic matter is considered in many multimedia transport models, but the effect of dissolved organic matter is typically ignored due to a lack of either reliable models or experimental data. The partition coefficient to dissolved organic carbon (K(DOC)) may be used to estimate the fraction of a contaminant that is associated with dissolved organic matter. Models relating K(DOC) to the octanol-water partition coefficient (K(OW)) have not been successful for many types of dissolved organic carbon in the environment. Instead, linear solvation energy relationships are proposed to model the association of chemicals with dissolved organic matter. However, more chemically diverse K(DOC) data are needed to produce a more robust model. For humic acid dissolved organic carbon, the linear solvation energy relationship predicts log K(DOC) with a root mean square error of 0.43. Copyright © 2011 SETAC.

A DDES model with a Smagorinsky-type eddy viscosity formulation and log-layer mismatch correction

International Nuclear Information System (INIS)

Reddy, K.R.; Ryon, J.A.; Durbin, P.A.

2014-01-01

Highlights: • An alternate DDES formulation is proposed via the eddy viscosity definition. • Eddy viscosity is expressed as a Smagorinsky-type formula. • Log-layer mismatch is corrected by changing the length scale definition. • Model is validated for 2D as well as 3D flows. - Abstract: The current work develops a variant of delayed detached eddy simulation (DDES) that could be characterized as limiting the production term. Previous formulations have been based on limiting the dissipation rate (Spalart et al., 2006). A clipped length scale is applied directly to the eddy viscosity, yielding a Smagorinsky-like formulation when the model is on the eddy simulation branch. That clipped eddy viscosity limits the production rate. The length scale is modified in order to account for the log-layer mismatch (a well-known issue with DDES), without using additional blending functions. Another view of our approach is that the subgrid eddy-viscosity is represented by a mixing length formula l 2 ω; in the eddy field ω acts like a filtered rate of strain. Our model is validated for channel flow as well as separated flows (backward-facing step, 2D periodic hills) and illustrated via an air-blast atomizer

Mortality in the cohort of nuclear workers of the French electricity company: 1968-2003 period

International Nuclear Information System (INIS)

Rogel, A.; Joly, K.; Metz-Flamant, C.; Laurier, D.; Tirmarche, M.; Hubert, D.; Garcier, Y.

2008-01-01

Full text: Background: We conducted a mortality study on a cohort of French nuclear workers employed at Electricite de France (EDF). A first mortality analysis relied on the period 1968-1994. Present results consider an updated mortality analysis including 9 additional years of follow-up and rely on the period 1968-2003. Methods: The cohort includes 22,393 workers, 96% of them are males. Employment data were updated using Personnel EDF file. Vital status was ascertained using the French National Registry of individual identification, and further completed using EDF personnel and pension files. Causes of death were obtained through the National file of causes of death. The observed mortality was compared with national rates by indirect standardisation and expressed by Standardised Mortality Ratios (SMR). All causes, all cancers and external causes SMRs were detailed according to sex, age and calendar year. Variations according to date of entry into cohort, duration of employment and socio-economic status (SES) were studied. Comparison with the earlier follow-up is presented. Results: At the present study end point (31/12/2003), 74% of workers are still in active service. Only 0.3% of workers are lost to follow up. The total number of person-years is nearly 450,000. Causes were ascertained for 96 % of deaths. The total number of deaths is 874: 307 are cancer deaths, including 16 leukaemia. SMRs for all causes of death and all cancers show a significant deficit compared to the French national mortality. Significant variations of all causes and all cancers SMRs according to SES were observed. No significant excess compared to French national mortality was observed for any of the 30 different cancer sites studied. Borderline significant excess were observed however for pancreatic, pleural, kidney and brain cancer. SMR for leukaemia is equal to unity. Conclusion: There is a clear evidence for an effect of selection of healthy individuals into the workforce. Although 9

Long-term impacts of selective logging on two Amazonian tree species with contrasting ecological and reproductive characteristics: inferences from Eco-gene model simulations.

Science.gov (United States)

Vinson, C C; Kanashiro, M; Sebbenn, A M; Williams, T C R; Harris, S A; Boshier, D H

2015-08-01

The impact of logging and subsequent recovery after logging is predicted to vary depending on specific life history traits of the logged species. The Eco-gene simulation model was used to evaluate the long-term impacts of selective logging over 300 years on two contrasting Brazilian Amazon tree species, Dipteryx odorata and Jacaranda copaia. D. odorata (Leguminosae), a slow growing climax tree, occurs at very low densities, whereas J. copaia (Bignoniaceae) is a fast growing pioneer tree that occurs at high densities. Microsatellite multilocus genotypes of the pre-logging populations were used as data inputs for the Eco-gene model and post-logging genetic data was used to verify the output from the simulations. Overall, under current Brazilian forest management regulations, there were neither short nor long-term impacts on J. copaia. By contrast, D. odorata cannot be sustainably logged under current regulations, a sustainable scenario was achieved by increasing the minimum cutting diameter at breast height from 50 to 100 cm over 30-year logging cycles. Genetic parameters were only slightly affected by selective logging, with reductions in the numbers of alleles and single genotypes. In the short term, the loss of alleles seen in J. copaia simulations was the same as in real data, whereas fewer alleles were lost in D. odorata simulations than in the field. The different impacts and periods of recovery for each species support the idea that ecological and genetic information are essential at species, ecological guild or reproductive group levels to help derive sustainable management scenarios for tropical forests.

H-infinity Control of Linear Systems with Almost Periodic Inputs

DEFF Research Database (Denmark)

Larsen, Mikael

1996-01-01

In this paper we consider the class of linear, infinitedimensional systems with bounded input and output operators. Wederive and QTR H-infinity type result, formulated for thecase where the input signals are almost periodic in a generalizedsense. Control probelms, for which this result is relevant...

VTE Risk assessment - a prognostic Model: BATER Cohort Study of young women.

Science.gov (United States)

Heinemann, Lothar Aj; Dominh, Thai; Assmann, Anita; Schramm, Wolfgang; Schürmann, Rolf; Hilpert, Jan; Spannagl, Michael

2005-04-18

BACKGROUND: Community-based cohort studies are not available that evaluated the predictive power of both clinical and genetic risk factors for venous thromboembolism (VTE). There is, however, clinical need to forecast the likelihood of future occurrence of VTE, at least qualitatively, to support decisions about intensity of diagnostic or preventive measures. MATERIALS AND METHODS: A 10-year observation period of the Bavarian Thromboembolic Risk (BATER) study, a cohort study of 4337 women (18-55 years), was used to develop a predictive model of VTE based on clinical and genetic variables at baseline (1993). The objective was to prepare a probabilistic scheme that discriminates women with virtually no VTE risk from those at higher levels of absolute VTE risk in the foreseeable future. A multivariate analysis determined which variables at baseline were the best predictors of a future VTE event, provided a ranking according to the predictive power, and permitted to design a simple graphic scheme to assess the individual VTE risk using five predictor variables. RESULTS: Thirty-four new confirmed VTEs occurred during the observation period of over 32,000 women-years (WYs). A model was developed mainly based on clinical information (personal history of previous VTE and family history of VTE, age, BMI) and one composite genetic risk markers (combining Factor V Leiden and Prothrombin G20210A Mutation). Four levels of increasing VTE risk were arbitrarily defined to map the prevalence in the study population: No/low risk of VTE (61.3%), moderate risk (21.1%), high risk (6.0%), very high risk of future VTE (0.9%). In 10.6% of the population the risk assessment was not possible due to lacking VTE cases. The average incidence rates for VTE in these four levels were: 4.1, 12.3, 47.2, and 170.5 per 104 WYs for no, moderate, high, and very high risk, respectively. CONCLUSION: Our prognostic tool - containing clinical information (and if available also genetic data) - seems to be

Stationarity and periodicities of linear speed of coronal mass ejection: a statistical signal processing approach

Science.gov (United States)

Chattopadhyay, Anirban; Khondekar, Mofazzal Hossain; Bhattacharjee, Anup Kumar

2017-09-01

In this paper initiative has been taken to search the periodicities of linear speed of Coronal Mass Ejection in solar cycle 23. Double exponential smoothing and Discrete Wavelet Transform are being used for detrending and filtering of the CME linear speed time series. To choose the appropriate statistical methodology for the said purpose, Smoothed Pseudo Wigner-Ville distribution (SPWVD) has been used beforehand to confirm the non-stationarity of the time series. The Time-Frequency representation tool like Hilbert Huang Transform and Empirical Mode decomposition has been implemented to unearth the underneath periodicities in the non-stationary time series of the linear speed of CME. Of all the periodicities having more than 95% Confidence Level, the relevant periodicities have been segregated out using Integral peak detection algorithm. The periodicities observed are of low scale ranging from 2-159 days with some relevant periods like 4 days, 10 days, 11 days, 12 days, 13.7 days, 14.5 and 21.6 days. These short range periodicities indicate the probable origin of the CME is the active longitude and the magnetic flux network of the sun. The results also insinuate about the probable mutual influence and causality with other solar activities (like solar radio emission, Ap index, solar wind speed, etc.) owing to the similitude between their periods and CME linear speed periods. The periodicities of 4 days and 10 days indicate the possible existence of the Rossby-type waves or planetary waves in Sun.

Single and multiple object tracking using log-euclidean Riemannian subspace and block-division appearance model.

Science.gov (United States)

Hu, Weiming; Li, Xi; Luo, Wenhan; Zhang, Xiaoqin; Maybank, Stephen; Zhang, Zhongfei

2012-12-01

Object appearance modeling is crucial for tracking objects, especially in videos captured by nonstationary cameras and for reasoning about occlusions between multiple moving objects. Based on the log-euclidean Riemannian metric on symmetric positive definite matrices, we propose an incremental log-euclidean Riemannian subspace learning algorithm in which covariance matrices of image features are mapped into a vector space with the log-euclidean Riemannian metric. Based on the subspace learning algorithm, we develop a log-euclidean block-division appearance model which captures both the global and local spatial layout information about object appearances. Single object tracking and multi-object tracking with occlusion reasoning are then achieved by particle filtering-based Bayesian state inference. During tracking, incremental updating of the log-euclidean block-division appearance model captures changes in object appearance. For multi-object tracking, the appearance models of the objects can be updated even in the presence of occlusions. Experimental results demonstrate that the proposed tracking algorithm obtains more accurate results than six state-of-the-art tracking algorithms.

Dynamic models for estimating the effect of HAART on CD4 in observational studies: Application to the Aquitaine Cohort and the Swiss HIV Cohort Study.

Science.gov (United States)

Prague, Mélanie; Commenges, Daniel; Gran, Jon Michael; Ledergerber, Bruno; Young, Jim; Furrer, Hansjakob; Thiébaut, Rodolphe

2017-03-01

Highly active antiretroviral therapy (HAART) has proved efficient in increasing CD4 counts in many randomized clinical trials. Because randomized trials have some limitations (e.g., short duration, highly selected subjects), it is interesting to assess the effect of treatments using observational studies. This is challenging because treatment is started preferentially in subjects with severe conditions. This general problem had been treated using Marginal Structural Models (MSM) relying on the counterfactual formulation. Another approach to causality is based on dynamical models. We present three discrete-time dynamic models based on linear increments models (LIM): the first one based on one difference equation for CD4 counts, the second with an equilibrium point, and the third based on a system of two difference equations, which allows jointly modeling CD4 counts and viral load. We also consider continuous-time models based on ordinary differential equations with non-linear mixed effects (ODE-NLME). These mechanistic models allow incorporating biological knowledge when available, which leads to increased statistical evidence for detecting treatment effect. Because inference in ODE-NLME is numerically challenging and requires specific methods and softwares, LIM are a valuable intermediary option in terms of consistency, precision, and complexity. We compare the different approaches in simulation and in illustration on the ANRS CO3 Aquitaine Cohort and the Swiss HIV Cohort Study. © 2016, The International Biometric Society.

Why did the breast cancer lymph node status distribution improve in Denmark in the pre-mammography screening period of 1978-1994?

International Nuclear Information System (INIS)

Rostgaard, Klaus; Lynge, Elsebeth; Vaeth, Michael; Rootzen, Helle

2010-01-01

Background. Danish breast cancer patients diagnosed in 1978-1994 experienced a trend over time towards a more favourable distribution of lymph node status at time of diagnosis, which was not due to mammography screening. We investigated how this trend could be explained by patient characteristics at diagnosis: age (biological processes), calendar period (e.g. environmental changes), birth cohort (living conditions over a life time), post-menopausal status (a predictor of less favourable nodal status), and tumour diameter (a marker of detection time). Material and methods. The data set consisted of 22 955 patients aged 30-69 years at time of diagnosis with known lymph node status, known tumour diameter, known menopausal status, and clinically detected tumours, available from the Danish Breast Cancer Cooperative Group (DBCG). Age, period, cohort, menopausal status, and tumour diameter were used as predictors in generalised linear models with either node-positive status (at least one of the excised lymph nodes being tumour-positive) or severely node-positive status (at least half of the excised lymph nodes being tumour-positive) as outcomes. Lymph node status was assessed both empirically and estimated using an EM algorithm in order to reduce misclassification. Results and discussion. We found that the improved lymph node status distribution was most likely a period effect due to a combination of earlier detection of clinical tumours, explaining most of the trend in node-positive breast cancer and half of the trend in severely node-positive breast cancer, and some unknown factor affecting lymph node status but not necessarily other tumour characteristics

PENENTUAN BENTUK FUNGSI MODEL EMPIRIK: STUDI KASUS PERMINTAAN KENDARAAN RODA EMPAT BARU

Directory of Open Access Journals (Sweden)

Andryan Setyadharma

2012-01-01

Full Text Available In many cases, the determination of form of the regression function of the empirical model betweenthe linear model and the log-linear model is neglected when someone starts research. Someoneconcludes the best model only by comparing the R2 value from respective function form and determinesthe best form of the function model only based on the highest R2 value. This is clearly wrong. This studyattempted to find the best regression function model by using two kinds of tests: MacKinnon, White andDavidson Test (MWD Test and Bera and McAleer Test (B-M Test. This Study showed that the twoforms of the empirical function models-both the linear and log-linear functions- could be used to estimatethe demand of the new four wheels vehicle in Indonesia. Furthermore, checking by using classicalassumption, we found that the log-linear function model is the best model to estimate the demand of thenew four wheels vehicle in Indonesia.Keywords: empirical model, linear model, log-linear model

Sexual Quality of Life and Aging: A Prospective Study of a Nationally Representative Sample.

Science.gov (United States)

Forbes, Miriam K; Eaton, Nicholas R; Krueger, Robert F

2017-02-01

Unlike other life domains, sexual quality of life (SQoL) has a negative relationship with age. This study disentangled the effect of age in this relationship from confounding sociocultural influences (e.g., the period of time in which data were collected, and cohort differences) and aimed to understand the roles of other sexual domains (i.e., frequency, perceived control, thought and effort invested in sex, and number of sexual partners). We analyzed data from the longitudinal Midlife in the United States study (n = 6,278; age range 20-93), which were collected between 1995 and 2013. Repeated measures linear mixed-effects models showed that age was the most robust time-related predictor of declining SQoL. However, after the sexual domains were included in the model, age had a positive relationship with SQoL and older adults' SQoL was differentially influenced by the quality-not quantity-of sex. When partnership characteristics were included in the model, age was no longer related to SQoL. These findings suggest that aging may be associated with the acquisition of skills and strategies that can buffer age-related declines in SQoL, particularly in the context of a positive relationship. We summarize these findings as sexual wisdom.