Trends in the Economic Independence of Young Adults in the United States: 1973-2007

One of the major milestones of adulthood is achieving economic independence. Without sufficient income, young people have difficulty leaving their childhood home, establishing a union, or having children-or they do so at great peril. Using the National Longitudinal Survey, this article compares the employment and economic circumstances of young adults aged 22-30 in 1973, 1987, and 2007, and their possible determinants. The results show that achieving economic independence is more difficult now than it was in the late 1980s and especially in the 1970s, even for the older age groups (age 27-28). The deterioration is more evident among men. From the 1970s there has been convergence in the trajectories for the achievement of economic self-sufficiency between men and women, suggesting that the increase in gender parity, especially in education and labor market outcomes, is making their opportunities to be employed and to earn good wages more similar. This convergence also suggests that union formation increasingly may depend on a capacity to combine men's and women's wages

Fast approximation of centrality and distances in hyperbolic graphs

We show that the eccentricities (and thus the centrality indices) of all vertices of a $\delta$-hyperbolic graph $G=(V,E)$ can be computed in linear time with an additive one-sided error of at most $c\delta$, i.e., after a linear time preprocessing, for every vertex $v$ of $G$ one can compute in $O(1)$ time an estimate $\hat{e}(v)$ of its eccentricity $ecc_G(v)$ such that $ecc_G(v)\leq \hat{e}(v)\leq ecc_G(v)+ c\delta$ for a small constant $c$. We prove that every $\delta$-hyperbolic graph $G$ has a shortest path tree, constructible in linear time, such that for every vertex $v$ of $G$, $ecc_G(v)\leq ecc_T(v)\leq ecc_G(v)+ c\delta$. These results are based on an interesting monotonicity property of the eccentricity function of hyperbolic graphs: the closer a vertex is to the center of $G$, the smaller its eccentricity is. We also show that the distance matrix of $G$ with an additive one-sided error of at most $c'\delta$ can be computed in $O(|V|^2\log^2|V|)$ time, where $c'< c$ is a small constant. Recent empirical studies show that many real-world graphs (including Internet application networks, web networks, collaboration networks, social networks, biological networks, and others) have small hyperbolicity. So, we analyze the performance of our algorithms for approximating centrality and distance matrix on a number of real-world networks. Our experimental results show that the obtained estimates are even better than the theoretical bounds.Comment: arXiv admin note: text overlap with arXiv:1506.01799 by other author

Global Update and Trends of Hidden Hunger, 1995-2011: The Hidden Hunger Index

Background Deficiencies in essential vitamins and minerals–also termed hidden hunger–are pervasive and hold negative consequences for the cognitive and physical development of children. Methods This analysis evaluates the change in hidden hunger over time in the form of one composite indicator–the Hidden Hunger Index (HHI)–using an unweighted average of prevalence estimates from the Nutrition Impact Model Study for anemia due to iron deficiency, vitamin A deficiency, and stunting (used as a proxy indicator for zinc deficiency). Net changes from 1995–2011 and population weighted regional means for various time periods are measured. Findings Globally, hidden hunger improved (-6.7 net change in HHI) from 1995–2011. Africa was the only region to see a deterioration in hidden hunger (+1.9) over the studied time period; East Asia and the Pacific performed exceptionally well (-13.0), while other regions improved only slightly. Improvements in HHI were mostly due to reductions in zinc and vitamin A deficiencies, while anemia due to iron deficiency persisted and even increased. Interpretation This analysis is critical for informing and tracking the impact of policy and programmatic efforts to reduce micronutrient deficiencies, to advance the global nutrition agenda, and to achieve the Millennium Development Goals (MDGs). However, there remains an unmet need to invest in gathering frequent, nationally representative, high-quality micronutrient data as we renew our efforts to scale up nutrition, and as we enter the post-2015 development agenda. Funding Preparation of this manuscript was funded by Sight and Life. There was no funding involved in the study design, data collection, analysis, or decision to publish

Available transfer capability evaluation by decomposition

A central issue of running a successful electric power market is the evaluation of the associated available transfer capability (ATC) representing the room available for trading. Due to the need to post and update ATC values at regular intervals, the underlying calculation method should be moderately fast with acceptable accuracy. This paper proposes the evaluation of ATC by using Benders decomposition. The problem is first broken up into a master problem expressing the steady state operating condition and subproblems for the contingent conditions. Each subproblem is solved independently and a linear constraint using Lagrange multipliers of the subproblem is generated and added to the master problem. The proposed decomposition scheme is applied to IEEE 30 bus system with satisfactory results as compared with the distribution factors method.published_or_final_versio

Market Allocation Between Bilateral Contracts and Spot Market without Financial Transmission Rights

In the electricity market, it is very important for Generation Companies (Gencos) to decide how to sell energy among different transaction markets in order to maximize profits with relatively low risk. In this paper, two energy transaction markets are considered: spot markets and bilateral contract markets. An energy selling allocation approach with network congestion consideration is established based on modern portfolio theory. Analytical solution for the optimal allocation is derived with given bilateral contract prices and statistical characteristics of the spot market prices. The numerical simulation for energy selling allocation is demonstrated based on the actual data of the USA California power market.published_or_final_versio

Career transitions and occupational well-being of women in leadership: The case of women as sports coaches

Introduction: The United Kingdom (U.K.) is working to develop the world’s leading sports coaching system. However, women currently make up only 28% of the profession and very few reach senior levels. Little is known about why career pathways are gendered or how women coaches’ occupational experiences affect their health and well-being. Therefore, the aim of this study was to further understanding of the occupational health and well-being of female sports coaches and to investigate the facilitators of and barriers to their careers and life transitions. Method: Following institutional ethical approval, women coaches (n = 162) based in the U.K. volunteered to take part. Each coach completed an online version of the Shortened Stress Evaluation Tool (ASSET; Cartwright & Cooper, 2002). This questionnaire is a valid and reliable measure of job characteristics, organisational commitment, health, and psychological well-being. Descriptive statistics were computed using a Statistical Package for the Social Sciences to provide a broad overview of the data. Results: 97% of the sample categorised themselves as ‘White’, ‘White Irish’, or ‘White Other;’ that the number of respondents over the age of 55 (n = 6) was dramatically lower than the number of responses from younger coaches (n = 156); and that 67% of the sample was educated to undergraduate degree level or higher. Over half of the sample (53%) was employed as a head coach at the time of completion and 56% of these head coaches were employed on a part-time basis. When compared to the normative data for ASSET, our sample reported above average psychological well-being (M = 27.75, SD = 4.87), sense of purpose (M = 18.72, SD = 4.01), and engagement (M = 19.18, SD = 3.78), and reported less strain on their psychological health (M = 21.06, SD = 6.91). However, the results also demonstrate that the coaches experience poorer work-life balance (M = 13.33, SD = 5.35), job security (M = 14.20, SD = 5.39), and work relationships (M = 18.02, SD = 7.88) than the normative sample. Conclusions: The findings suggest that, on average, our sample of women coaches are highly engaged with their role, feel a sense of purpose during their coaching practice, and are psychologically well. The results do, however, suggest that women coaches require better work-life balance, more job security, and more meaningful relationships with their colleagues. These findings provide insight to potential facilitators of and barriers to career progression for women coaches and offer interesting applied implications for national governing bodies (NGBs). In particular, NGBs should pay acute attention to interventions that support women coaches to connect with other coaches and effectively balance their personal and occupational commitments

Multiyear transmission expansion planning using ordinal optimization

The increasing complexity of the transmission expansion planning problem in the restructured industry makes simulation the only viable means to evaluate and compare the performances of different plans. Ordinal optimization is an approach suitable for solving the simulation-based multiyear transmission expansion planning problem. It uses crude models and rough estimates to derive a small set of plans for which simulations are necessary and worthwhile to find good enough solutions. In the end, reasonable solutions are obtained with drastically reduced computational burden. © 2007 IEEE.published_or_final_versio

Extended modular operad

This paper is a sequel to [LoMa] where moduli spaces of painted stable curves were introduced and studied. We define the extended modular operad of genus zero, algebras over this operad, and study the formal differential geometric structures related to these algebras: pencils of flat connections and Frobenius manifolds without metric. We focus here on the combinatorial aspects of the picture. Algebraic geometric aspects are treated in [Ma2].Comment: 38 pp., amstex file, no figures. This version contains additional references and minor change

Probing the mechanism of neutrinoless double-beta decay in multiple isotopes

A large experimental program is being mounted to search for neutrinoless double-beta decay over the next decade. Multiple experiments using different target isotopes are being prepared to explore the whole parameter space allowed for inverted-ordered light neutrinos, and have the potential to make discoveries in several other scenarios, including normal-ordered light neutrinos and other exotic mechanisms. We investigate to what extent long-range and exotic short-range contributions may be distinguished by combining measurements of the decay half-life across isotopes in the framework of a global Bayesian analysis. We demonstrate how measurements in two isotopes will constrain the parameter space up to a two-fold degeneracy, and how a further measurement in a third isotope removes such a degeneracy. We also discuss the impact of uncertainties and correlations in nuclear matrix element calculations. Our work motivates an experimental program measuring neutrinoless double-beta decay in more than one isotope, as this would break parameter degeneracies and advance our understanding of particle physics beyond the Standard Model

Simulation and evaluation of optimization problem solutions in distributed energy management systems

Deregulation in electricity markets requires fast and robust optimization tools for a secure and efficient operation of the electric power system. In addition, there is the need of integrating and coordinating operational decisions taken by different utilities acting in the same market. Distributed Energy Management Systems (DEMS) may help to fulfill these requirements. The design of a DEMS requires detailed simulation results for the evaluation of its performance. To simulate the operation of a DEMS from the optimization standpoint, a general purpose distributed optimization software tool, DistOpt, is used, and its capabilities are extended to handle power system problems. The application to the optimal power flow problem is presented.published_or_final_versio