Random recursive trees and the Bolthausen-Sznitman coalescent

We describe a representation of the Bolthausen-Sznitman coalescent in terms of the cutting of random recursive trees. Using this representation, we prove results concerning the final collision of the coalescent restricted to [n]: we show that the distribution of the number of blocks involved in the final collision converges as n tends to infinity, and obtain a scaling law for the sizes of these blocks. We also consider the discrete-time Markov chain giving the number of blocks after each collision of the coalescent restricted to [n]; we show that the transition probabilities of the time-reversal of this Markov chain have limits as n tends to infinity. These results can be interpreted as describing a ``post-gelation'' phase of the Bolthausen-Sznitman coalescent, in which a giant cluster containing almost all of the mass has already formed and the remaining small blocks are being absorbed.Comment: 28 pages, 2 figures. Revised version with minor alterations. To appear in Electron. J. Proba

The effects of strain, reproductive condition, and strain of placenta donor on placentophagia in nonpregnant mice

The effects on placentophagia of strain, reproductive condition, and strain of placenta donor were observed in nonpregnant mice. Mice of the C57BL/6By and BALB/cBy strains were exposed to placentas of either strain after either no previous parturitional experience, one parturitional experience without nursing experience, or one parturitional experience with nursing experience. There was a significant effect of strain, a significant effect of reproductive condition, but no significant effect of strain of placenta donor. There was a significant interaction between strain and reproductive condition, but no significant interactions with placenta strain. It was inferred that the ability of a mouse to acquire and utilize relevant stimuli during and after parturition, in order to produce an emancipation of placentophagia from the physiological controls associated with parturition, is influenced by genotype

Abusive Romantic Relationships among Adolescent and Young Adult Mothers

The associations between intimate partner violence (IPV) and mental health among adolescents and young adults were compared in the current study. The connections among marriage status, Latino heritage and abusive experiences were also analyzed. 672 women including 282 adolescents between the ages of 14 and 19 and 390 young adults aged 20 or 21 participated in the study. Significant correlations were discovered between anxiety and depression symptoms among adolescents while anxiety and IPV, anxiety and depression, depression and IPV were all significantly correlated among young adults. In addition, IPV and marriage status as well as marriage status and Latina heritage were significantly correlated among young adults. No significant findings came from linear or logistic regressions conducted with the adolescent data but, among young adults, linear regressions with IPV as the dependent variable led to significant relationships between IPV and marital status. In addition, logistic regressions indicated significant links in the young adult data between IPV and depression and anxiety symptoms. IPV during adolescence may be a different phenomenon than adult IPV or mental health symptoms may be latent variables that are reported later in life. Prevention programs for adolescents as well as young adults are encouraged.

Looking Beyond the Marketing Claims of New Beverages: Health Risks of Consuming Sports Drinks, Energy Drinks, Fortified Waters, and Other Flavored Beverages

Consumption of several new categories of beverages has increased significantly in recent years. Sold in cans and bottles in many venues and heavily marketed as health and strength enhancing, these beverages have become popular among children and adolescents as well as adults. Energy drinks, sports drinks, fruit drinks, flavored waters, and sweetened teas and coffees are known collectively as fortified beverages due to the natural and artificial ingredients that are added in the processing of their main ingredient, water. In view of their rising popularity, it is important to assess the healthfulness of these beverages and the implications of their consumption by the general public. Consumption by youth, to whom marketing is often targeted, is of particular interest in view of children's potentially increased vulnerability to chemicals and other added substances. Further, the possible contribution of these beverages to the high prevalence of childhood obesity merits attention.This report will discuss the major categories of fortified beverages, presenting data on their nature, their ingredients, their similarities and differences, the possible effects on children of their consumption, and areas for further research

Coagulation--fragmentation duality, Poisson--Dirichlet distributions and random recursive trees

In this paper we give a new example of duality between fragmentation and coagulation operators. Consider the space of partitions of mass (i.e., decreasing sequences of nonnegative real numbers whose sum is 1) and the two-parameter family of Poisson--Dirichlet distributions $\operatorname {PD}(\alpha,\theta)$ that take values in this space. We introduce families of random fragmentation and coagulation operators $\mathrm {Frag}_{\alpha}$ and $\mathrm {Coag}_{\alpha,\theta}$, respectively, with the following property: if the input to $\mathrm {Frag}_{\alpha}$ has $\operatorname {PD}(\alpha,\theta)$ distribution, then the output has $\operatorname {PD}(\alpha,\theta+1)$ distribution, while the reverse is true for $\mathrm {Coag}_{\alpha,\theta}$. This result may be proved using a subordinator representation and it provides a companion set of relations to those of Pitman between $\operatorname {PD}(\alpha,\theta)$ and $\operatorname {PD}(\alpha\beta,\theta)$. Repeated application of the $\mathrm {Frag}_{\alpha}$ operators gives rise to a family of fragmentation chains. We show that these Markov chains can be encoded naturally by certain random recursive trees, and use this representation to give an alternative and more concrete proof of the coagulation--fragmentation duality.Comment: Published at http://dx.doi.org/10.1214/105051606000000655 in the Annals of Applied Probability (http://www.imstat.org/aap/) by the Institute of Mathematical Statistics (http://www.imstat.org

The German Public Pension System: How it Was, How it Will Be

Germany still has a very generous public pay-as-you-go pension system. It is characterized by early effective retirement ages and very high effective replacement rates. Most workers receive virtually all of their retirement income from this public retirement insurance. Costs are almost 12 percent of GDP, more than 2.5 times as much as the U.S. Social Security System. The pressures exerted by population aging on this monolithic system, amplified by negative incentive effects, have induced a reform process that began in 1992 and is still ongoing. This process is the topic of this paper. It has two parts. Part A describes the German pension system as it has shaped the labor market until about the year 2000. Part B describes the three staged reform process that will convert the exemplary and monolithic Bismarckian public insurance system after the year 2000 into a complex multipillar system. The paper delivers an assessment in how far these reform steps will solve the pressing problems of a prototypical pay-as-you-go system of old age provision, hopefully with lessons for other countries with similar problems.

Evidence of Program Quality and Youth Outcomes in the DYCD Out-of-School Time Initiative: Report on the Initiative's First Three Years

Examines New York City's progress in improving out-of-school-time program quality and serving more children and youth, participants' and parents' overall satisfaction with quality and accessibility, and links between programming, quality, and benefits

The importance of key supplier relationship management in supply chains

Purpose: This paper investigates the impact of key supplier relationship management (KSRM) – understood as an aggregated supply chain management (SCM) process in the upstream direction – on the overall level of the execution of SCM within organizations. Methodology: A conceptual model is developed from a theoretical framework and proposes the capability to do KSRM as a mediator between internal and external SCM resources and SCM execution. A survey of 174 managers representing different supply chain stages is used to test the model through variance-based structural equation modelling. Findings: The findings reveal that external SCM resources directly affect the capability to do KSRM. Nevertheless, internal resources show a considerable indirect impact through external resources and can thus be considered an indirect determinant. The capability to do KSRM in turn impacts upon the level of SCM execution, measured in terms of the integration of business processes, directly and substantially, as well as mediating the effect between SCM resources and the level of SCM execution. Value: The main contribution of this paper is to empirically demonstrate the potential of KSRM for enhancing the level of SCM execution within organizations and consequently the level of integration in supply chains, leading to higher customer and shareholder value