A Numerical Solution to the Nonhomogeneous Two-Stage MVK Model of Cancer

In this article, we describe a straightforward method for solving the probability of at least one malignant cell by time t, and the associated hazard function, in the general (i.e., nonhomogeneous) two-stage Moolgavkar-Venzon-Knudson (MVK) model of cancer. The method consists of solving four coupled ordinary differential equations derived from the Kolmogorov backward equations for this process. The relationship of this method to previously proposed solutions is discussed.     

Joint Attention,Self‐Recognition,and Neurocognitive Function in Toddlers

Recent studies have attempted to understand the processes involved in joint attention because of its relevance to both atypical and normal development. Data from a recent study of young children with autism suggests that performance on a delay nonmatch to sample (DNMS) task associated with ventromedial prefrontal functions, but not an A‐not‐B/delayed response task associated with dorsolateral prefrontal cortex, was related to joint attention skills (Dawson et al., 2002). Recent research also suggests that joint attention is associated with dorsalmedial brain systems linked to self‐monitoring (Mundy, 2003). This study investigated the relations among joint attention, DNMS, and self‐recognition performance in a longitudinal study of 39 normally developing toddlers from 14 to 18 months. The results indicated that development on the DNMS and self‐recognition tasks, but not a means end task, predicted joint attention at 18 months. Further analysis showed that the model was only significant for initiating joint attention (IJA). The implications of these results for the neuro‐development of IJA are discussed.     

The Ecology of Family Guidance in Low-Income Mexican-American and European-American Families*

This two-part study applied an ecocultural perspective to socialization of daily and long-term goals in low-income Mexican-American and European-American families with children in third, fifth, and seventh grades. The first part of the study examined family members' participation and parents' socialization goals and guidance strategies for their children's daily household chores and homework activities. The second part of the study examined parents' long-term aspirations and guidance strategies for their children's educational, vocational, and moral development. For daily activities, results showed that in Mexican-American families both parents and siblings played important roles, whereas in European-American families parents were the primary socialization agents. As predicted, in both groups parents' expertise influenced their guidance strategies. Finally, Mexican-American and European-American parents differed in their relative endorsement of gender, relational, and self-reliance goals for household chores. For long-term goals, parents in both groups held high educational, vocational, and moral aspirations for their children. However, some parents of seventh-graders had lower educational and vocational aspirations than those of fifth- and third-graders. Although expertise consistently influenced Mexican-American parents' guidance strategies, the pattern for European-American parents was mixed. The discussion highlights between- and within-group differences in daily and long-term socialization practices with an emphasis on resources and vulnerabilities in the families.     

Improving on truncated linear estimates of exponential and gamma scale parameters

We consider the problem of estimating the scale parameter of an exponential or a gamma distribution under squared error loss when the scale parameter θ is known to be greater than some fixed value θ₀. Natural estimators in this setting include truncated linear functions of the sufficient statistic. Such estimators are typically inadmissible, but explicit improvements seem difficult to find. Some are presented here. A particularly interesting finding is that estimators which are admissible in the untruncated problem which take values only in the interior of the truncated parameter space are found to be inadmissible for the truncated problem.     

Leslie matrix models

A review of the Leslie matrix model theory and its literature 1941-1987 is presented. The point of view is that of a mathematician who focuses on the parts of the theory which are relevant to demography. Works of a decidedly applied nature are not dealt with.     

The impact of social networks on the occupational status of migrants

This paper postulates that there is a continuous exchange of information and knowledge between those who share the common bond of having migrated to the US. The individual components of this information exchange constitute social networks. The 2 hypotheses tested are 1) immediate social networks and people known in the US facilitate the flow of information both to new migrants and between established migrants, thus promoting upward social mobility; and 2) access to broader network ties, organization membership, extra-ethnic friendships, and familiarity with established institutions smooths the transition process, resulting in increased social position. The data used comes from a study conducted in 1982-1983 in 4 Mexican sending communities (2 rural, 2 urban), for a total of 440 migrants. Results show that migrants in every socioeconomic bracket reported access to some or all social network characteristics. There was contact with either a family member or acquaintances from the migrants' town of origin. Over 50% of migrants reported knowing many fellow townspeople. Twice as many migrants belong to a sports club as to a social or religious organization. Very few rural migrants report knowing no townspeople, while 32% of urban migrants claim no knowledge of fellow migrants from their town of origin. Urban origin migrants report more contacts with those of other ethnicity than rural migrants. Those employed in agriculture are least acquainted with social information and contacts, while those in skilled and service sectors are well acquainted with them. The results of fact and analysis show that 1) access to personal US networks results in an average 4.4 point advantage in occupational prestige scores over no access, and 2) utilizing institutional US networks combined with any cumulative US experience gives a migrant a 5 point advantage over a fellow migrant with identical experience level but no institutional network contacts. This is also true for institutional Mexican networks. Thus success or failure in migrating is partly due to migrants' societal infrastructure and the fact that available information and social networks are accessed and utilized differently by different migrants.     

Assimilation process and group integration of migrant families

This empirical analysis gives 1st answers to the question of which effects some specific types of interaction structures within migrant families have on the assimilation process of family members and their personal integration. The analysis is based on a sample of 92 Turkish women and 123 Turkish men in the Bonn-Cologne area of West Germany. Questionnaires examine variables such as 1) urbanization of the context of origin, 2) household complexity, 3) availability of ethnic infrastructure, 4) residential proximity of Turkish friends and relatives; 5) school education of respondent and spouse; and 6) occupational prestige before migration. The study considers the following dimensions of social and cultural assimilation: 1) housing quality, 2) use of ethnic and general infrastructure, and 3) use of ethnic minority and mainstream cultural facilities. Results of empirical analyses on the housing conditions of migrants show that 1) motivational factors of the migrant family are unrelated to choice of a housing area, but are related to apartment quality; and 2) housing conditions differ markedly, depending on the type of combination of task-allocation and decision-making power in the family. Use of infrastructure 1) declines in Turkish families in which women's participation in family tasks is relatively high, 2) is determined most by the opportunity structure of the housing area and the interaction structure within the family; and 3) is a necessary step between the reorganization of the family's interaction structure and the participation in a broader spectrum of institutions of the receiving society. The family structure has no significant effect on participation in the minority culture. The extent of minority-culture rise has no direct relationship to the individual assimilation of family members. The empirical data support the basic theoretical assumption that the group integration of the migrant family has considerable effects on the assimilation process of its individual members. In conclusion, 1) opportunities for assimilation are increased by the combined resources of the migrants family household, and 2) continuing individual autonomy contributes severely to a reduced personal integration.     

Policies over time and pareto optimality

This paper is concerned with sequences of policies that occur over time in voting models and planning procedures. The framework for our analysis includes assumptions that are satisfied by models in the corresponding literatures, together with other standard assumptions for microeconomic analysis that involve time. The starting point for our analyses is the prespective that results from combining the following (widely held) views: 1) certain voting models and planning procedures can be interpreted as being non-tatonnement or sequential processes (where each policy in the sequence that is generated is actually experienced by voters or consumers) and 2) an alternative being Pareto optimal in any given period (temporal Pareto optimality) is the appropriate efficiency criterion only if the alternative is the final outcome from a tatonnement process-and that, otherwise, one should examine the efficiency of the entire path (using intertemporal Pareto optimality). Our first observation about the planning literature is that is has (by and large) neglected the efficiency criterion that is appropriate for the discrete-time procedures that can be interpreted as non-tatonnement or sequential processes-and that, what's more, such trajectories will (in general) fail to meet this criterion. Our second observation identifies some results that can be used to establish that some of these trajectories will at least be ultimately intertemporally Pareto optimal. In our discussion of voting theory, we review Buchanan's opposition to requiring (social) choice consistency for voting procedures-and his argument for this position on (Pareto) efficiency grounds. We then consider voting procedures that can be interpreted as non-tatonnement or sequential processes and arrive at the conclusion that, in these cases, (i) majority rule cycles are intertemporally Pareto inefficient and (ii) achieving intertemporal Pareto optimality requires choice consistency. We then go on to show that related observations apply to Kramer's normative conclusions about his dynamical model of political equilibrium — and identify some further references where similar observations apply. In the final part of our discussion of voting models, we arrive at the further conclusion that, in the most relevant cases, a trajectory that stays in the temporal Pareto set is not necessarily more desirable (on efficiency grounds) than one that doesn't.This paper has been improved by helpful comments and suggestions that have been provided by Kenneth Arrow, an anonymous referee, and the editor who handled the paper.Peter Coughlin gratefully acknowledges financial support provided by (i) National Science Foundation Grant No. SES-8409352, and (ii) the Center for Advanced Study in the Behavioral Sciences at Stanford (with support from National Science Foundation Grant No. BNS-8700864 and the Alfred P. Sloan Foundation).     

Enrich marital inventory: a discriminant validity and cross-validation assessment

To assess the validity and clinical utility of the marital inventory ENRICH, a discriminant validity study was conducted using a national sample of 5039 married couples. The sample was randomly split in order to form a cross-validation group. ENRICH is a multidimensional scale and two types of analysis were conducted to assess the value of these various scales. Results from discriminant analysis indicated that using either the individual scores or couples' scores, happily married couples could be discriminated from unhappily married couples with 85–95% accuracy. These results were cross-validated with a second sample. Using regression analysis, it was clearly demonstrated that background factors account for little of the variance in discriminating happy from unhappily married couples compared to their relationship dynamics, i.e., scale scores. All ENRICH scales except equalitarian roles proved significant, indicating the validity of a multidimensional inventory.