Baby boomlet for older mothers?

In recent years, a number of celebrities have begun childbearing after age 35. The phenomena of older first-time mothers has received a great deal of attention in the popular press. Are these celebrities indicative of a national trend? Does the increase in fertility portend a reversal of the declines in fertility which have been occurring since the baby boom? The present paper uses central and cumulative birth rates for cohorts of American white women born between 1882 and 1953 to investigate childbearing between ages 35 and 50. While there has been a noticeable upsurge in first birth rates for cohorts in their mid to late 30s in recent years, overall central birth rates for women in their 30s are among the lowest on record, with cumulative birth rates at record low levels. A major reason for this is that these women are having relatively few third and higher order births. These cohorts will need to have a relatively high proportion of births in their older years of childbearing in order to reach replacement level. However, attaining replacement level is unlikely because such a high proportion of women have remained childless at ages 35–40 and a relatively low proportion are having three or more children.     

SPECIFICATION AND ESTIMATION OF LOGICALLY CONSISTENT LINEAR MODELS

The implications of constrained dependent and independent variables for model parameters are examined. In the context of linear model systems, it is shown that polyhedral constraints on the dependent variables will hold over the domain of the independent variables when a set of polyhedral constraints is satisfied by the model parameters. This result may be used in parameter estimation, in which case all predicted values of the dependent variables are consistent with constraints on the actual values. Also, the implicit constraints that define the set of parameters for many commonly used linear stochastic models with an error term yield values of the dependent variables consistent with the explicit constraints. Models possessing these properties are termed “logically consistent”.     

Developing From Tranditional Microscale Chemistry to Microscale Green Chemistry

Microscale chemistry is appealing to all levels of education.In contrast to conventional macroscale chemistry,only minute amount of chemicals are required to undertaking a chemical investigation.     

Long- and short-term affective states in happiness: Model,paradigm and experimental evidence

The present paper evaluates relevant findings on long- and short-term affective states in subjective well-being and argues for a componential model that combines the two into the more general concept of happiness. Two age parameters, one for long-term and one for short-term affect are added to the simple model to account for age changes in happiness. Measures of long- and short-term affect are presented, as is a paradigm for separating the components. Support for the simple model is provided by an experimental investigation with 64 college students who were exposed to positive and/or negative mood induction. As expected, the induction had substantially greater effect on short- than on long-term affect measures, particularly the negative induction procedure. These findings are consistent with predictions. However, multiple age cohorts will have to be assessed within a longitudinal framework to obtain values for the age parameters.     

A bayesian test for a two-way contingency table using independence priors

One method of testing for independence in a two-way table is based on the Bayes factor, the ratio of the likelihoods under the independence hypothesis H and the alternative hypothesis H. The main difficulty in this approach is the specification of prior distributions on the composite hypotheses H and H. A new Bayesian test statistic is constructed by using a prior distribution on H that is concentrated about the “independence surface” H. Approximations are proposed which simplify the computation of the test statistic. The values of the Bayes factor are compared with values of statistics proposed by Gunel and Dickey (1974), Good and Crook (1987), and Spiegelhalter and Smith (1982) for a number of two-way tables. This investigation suggests a strong relationship between the new statistic and the p-value.     

Grenzen der Geschichte?

The article follows Tony Becher’s suggestion, that scientific disciplines metaphorically spoken may be looked at as different tribes of different habits occupying different territories. The articles reviews then some possibilities to determine a border between the field of historical research and sociology by different methods, different theories, different research objects e. g. past vs. present and so on. The academic field of history is described as a field importing theories, methods and objects from other academic fields, many of them from sociology. The last decades’ processes of innovation and redefinition within the field of historical research diminished cognitive differences between history and sociology so significantly that — this is the main argument of the article — more or less only the borders produced by institutions remained. Nevertheless these kind of borders have major effects all of them responsible for maintaining different disciplinary identities.     

International Terrorism and the World‐System

Theories of international terrorism are reviewed. It then is noted that waves of terrorism appear in semiperipheral zones of the world‐system during pulsations of globalization when the dominant state is in decline. Finally, how these and other factors might combine to suggest a model of terrorism's role in the cyclical undulations of the world‐system is suggested .