Patterns of Aging in Thailand and Cote D'Ivoire

This paper is broadly concerned with the living standards of older people in two contrasting developing countries, Cote d'Ivoire and Thailand. We use a series of household surveys from these two countries to present evidence on factors affecting the living standards of the elderly: living arrangements, labor force participation, illness, urbanization, income and consumption. One of the issues we examine is whether life-cycle patterns of income aid consumption can be detected in the data. The fact that few of the elderly live alone makes it difficult to accurately measure the welfare levels of the elderly, or to make statements about the life-cycle patterns of income aid consumption of individuals. We find that labor force participation and individual income patterns follow the standard life-cycle hump shapes in both countries, but that avenge living standards within households are quite flat over the life-cycle. The data presented suggest that changes in family composition aid living arrangements of the elderly are likely to be more important sources of old-age insurance than asset accumulation.

Labor Supply Preferences, Hours Constraints, and Hours-Wage Tradeoffs

In a labor market in which firms offer tied hours-wage packages and there is substantial dispersion in the wage offers associated with a particular type of job, the best job available to a worker at a point in time may pay well but require an hours level which is far from the worker's labor supply schedule, or pay poorly but offer desirable hours. Intuitively, one would expect hours constraints to influence the pattern of wage-hours tradeoffs which occur when workers quit to new jobs. Constrained workers may be willing to sacrifice wage gains for better hours. Likewise, workers may accept jobs offering undesirable hours only if the associated wage gains are large. We investigate this issue empirically by examining whether overemployment (underemployment) on the initial job increases (reduces) the partial effect on the wage gain of a positive change in hours for those who quit. We also examine whether overemployment (underemployment) on the new job increases (reduces) the partial effect on the wage gain of a positive change in hours for those who quit. Despite the limitations imposed by small sample sizes and lack of information on the magnitude of hours constraints, our results support the view that an individual requires compensation to work in jobs which, given the individual's particular preferences, offer unattractive hours.

Job Characteristics and Hours of Work

This paper provides evidence that hours of work are heavily influenced by the particular job which a person holds. The empirical work consists of a comparison of the variance in the change in work hours across time intervals containing a job change with the variance in the change in hours across time periods when the job remains the same. To the extent that workers choose hours and these hours choices are influenced by shifts in individual preferences and resources, the variance in the time change of hours should not depend upon whether the worker has switched jobs. The desire to reduce or increase hours could be acted upon in the current job. On the other hand, if hours are influenced by employer preferences or if job specific characteristics dominate the labor supply decision, then hours changes should be larger when persons change jobs than when they do not. Using the Panel Study of Income Dynamics and the Quality of Employment Survey, we find that hours changes are typically two to four times more variable across jobs than within jobs. This result holds for both men and women and for both quits and layoffs, is obtained for weeks per year, hours per week, and annual hours, andis not sensitive to the use of controls for a set of job characteristics (including the wage) which might influence the level of hours persons wish to supply. The findings are also inconsistent with the view that workers may costlessly adjust hours by changing jobs.The finding that the job has a large influence on work hours suggests that much greater emphasis should be given to demand factors and to job specific labor supply factors in future research on hours of work. The overwhelming emphasis upon the wage and personal characteristics inconventional labor supply analyses of work hours may in part be misplaced.

The Dynamics of Dual-Job Holding and Job Mobility

This article concerns the incidence and dynamics of dual-job holding, and its link to job mobility. The first section presents evidence on patterns of dual-job holding, hours changes, and job mobility in the United States, using data from the Panel Study of Income Dynamics and the Current Population Survey. The results indicate that most workers experience dual-job holding sometime during their working lives, and there is a great deal of movement into and out of dual-job holding. Mobility into and out of second jobs is associated with large changes in weekly and annual hours, and there is evidence that dual-job holding is prompted by hours constraints on the main job. The second section of the article turns to theories of dual-job holding. Much of the empirical literature on second jobs is motivated by a simple model of labor supply in which workers face upper constraints on main-job hours: a worker who would like to work more on his main job, but cannot, will take a second job provided the second-job wage is high enough. These models do not account for the fact that workers may also avoid hours constraints by finding new main jobs with higher hours. We develop a stochastic dynamic model of dual-job holding and job mobility in which decisions to take second jobs and/or change main jobs are made simultaneously. This model is consistent with our findings and provides new insights into the economics of dual-job holding and labor mobility.

Approximation Bias in Linearized Euler Equations

A wide range of empirical applications rely on linear approximations to dynamic Euler equations. Among the most notable of these is the large and growing literature on precautionary saving that examines how consumption growth and saving behavior are affected by uncertainty and prudence. Linear approximations to Euler equations imply a linear relationship between expected consumption growth and uncertainty in consumption growth, with a slope coefficient that is a function of the coefficient of relative prudence. This literature has produced puzzling results: Estimates of the coefficient of relative prudence (and the coefficient of relative risk aversion) from regressions of consumption growth on uncertainty in consumption growth imply estimates of prudence and risk aversion that are unrealistically low. Using numerical solutions to a fairly standard intertemporal optimization problem, our results show that the actual relationship between expected consumption growth and uncertainty in consumption growth differs substantially from the relationship implied by a linear approximation. We also present Monte Carlo evidence that shows that the instrumental variables methods commonly used to estimate the parameters correct some, but not all, of the approximation bias.

Summary of Pressure Gain Combustion Research at NASA

NASA has undertaken a systematic exploration of many different facets of pressure gain combustion over the last 25 years in an effort to exploit the inherent thermodynamic advantage of pressure gain combustion over the constant pressure combustion process used in most aerospace propulsion systems. Applications as varied as small-scale UAV's, rotorcraft, subsonic transports, hypersonics and launch vehicles have been considered. In addition to studying pressure gain combustor concepts such as wave rotors, pulse detonation engines, pulsejets, and rotating detonation engines, NASA has studied inlets, nozzles, ejectors and turbines which must also process unsteady flow in an integrated propulsion system. Other design considerations such as acoustic signature, combustor material life and heat transfer that are unique to pressure gain combustors have also been addressed in NASA research projects. In addition to a wide range of experimental studies, a number of computer codes, from 0-D up through 3-D, have been developed or modified to specifically address the analysis of unsteady flow fields. Loss models have also been developed and incorporated into these codes that improve the accuracy of performance predictions and decrease computational time. These codes have been validated numerous times across a broad range of operating conditions, and it has been found that once validated for one particular pressure gain combustion configuration, these codes are readily adaptable to the others. All in all, the documentation of this work has encompassed approximately 170 NASA technical reports, conference papers and journal articles to date. These publications are very briefly summarized herein, providing a single point of reference for all of NASA's pressure gain combustion research efforts. This documentation does not include the significant contributions made by NASA research staff to the programs of other agencies, universities, industrial partners and professional society committees through serving as technical advisors, technical reviewers and research consultants

Exact results for the Barabasi model of human dynamics

Human activity patterns display a bursty dynamics, with interevent times following a heavy tailed distribution. This behavior has been recently shown to be rooted in the fact that humans assign their active tasks different priorities, a process that can be modeled as a priority queueing system [A.-L. Barabasi, Nature 435, 207 (2005)]. In this work we obtain exact results for the Barabasi model with two tasks, calculating the priority and waiting time distribution of active tasks. We demonstrate that the model has a singular behavior in the extremal dynamics limit, when the highest priority task is selected first. We find that independently of the selection protocol, the average waiting time is smaller or equal to the number of active tasks, and discuss the asymptotic behavior of the waiting time distribution. These results have important implications for understanding complex systems with extremal dynamics.Comment: 4 pages, 4 figures, revte

Activation of δ-globin gene expression by erythroid Krupple-like factor: A potential approach for gene therapy of sickle cell disease

Hemoglobin A2 (HbA2; α2δ2) is a powerful inhibitor of HbS (α2β2/(S) polymerization. However, HbA2 levels are normally low in sickle cell patients. We show that a major reason for low δ-globin gene expression is the defective CACCC box at -90 in the δ-globin promoter. When the CACCC box defect in δ is corrected, expression of an HS2 δ/Luciferase reporter is equivalent to HS2 β/Luciferase. Erythroid Krupple-like factor (EKLF), which binds to the CACCC box of the β-globin gene and activates high-level expression, does not bind to the normal δ-globin promoter. Our goal is to design a modified EKLF that binds to the defective δ-globin promoter and enhances δ-globin gene expression. To test the feasibility of this strategy, we inserted the β-globin CACCC box at -90 of the δ-globin gene promoter to produce an HS2 δ(CAC)-β construct and quantitated human δ- and β-globin mRNA in stably transformed murine erythroleukemia (MEL) cells. δ-Globin mRNA in these cells was 22.0% ± 9.0% of total human globin mRNA (δ/δ + β) as compared with 3.0% ± 1.3% in the HS2 δ-β control. In a second set of experiments a GAL4 DNA-binding site was inserted at -90 of the δ-globin gene to produce an HS2 δ(GAL4)-β construct. This construct and a GAL4((1-147))/EKLF expression vector were stably transfected into MEL cells. δ-Globin mRNA in these cells was 27.8% ± 7.1% of total human globin mRNA as compared with 9.9% ± 2.5% in the HS2 δ(GAL4)-β plus GAL4((1-147)) control. These results show that δ-globin gene expression can be significantly increased by a modified EKLF. Based on these results, we suggest that modified EKLFs, which contain zinc fingers designed to bind specifically to the defective δ-globin CACCC box, may be useful in gene therapy approaches to increase HbA2 levels and inhibit HbS polymerization

The Inklings in America

Transcription of a panel discussion at the 19th Mythopoeic Conference

zeek-osquery: Host-Network Correlation for Advanced Monitoring and Intrusion Detection

Intrusion Detection Systems (IDSs) can analyze network traffic for signs of attacks and intrusions. However, encrypted communication limits their visibility and sophisticated attackers additionally try to evade their detection. To overcome these limitations, we extend the scope of Network IDSs (NIDSs) with additional data from the hosts. For that, we propose the integrated open-source zeek-osquery platform that combines the Zeek IDS with the osquery host monitor. Our platform can collect, process, and correlate host and network data at large scale, e.g., to attribute network flows to processes and users. The platform can be flexibly extended with own detection scripts using already correlated, but also additional and dynamically retrieved host data. A distributed deployment enables it to scale with an arbitrary number of osquery hosts. Our evaluation results indicate that a single Zeek instance can manage more than 870 osquery hosts and can attribute more than 96% of TCP connections to host-side applications and users in real-time.Comment: Accepted for publication at ICT Systems Security and Privacy Protection (IFIP) SEC 202