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Paid home care can significantly improve the lives of older adults with disabilities and their families, but recipients often incur substantial out-of-pocket spending. We simulated the financial burden of paid home care for a nationally representative sample of non-Medicaid community-dwelling adults ages sixty-five and older. We found that 74 percent could fund at least two years of a moderate amount of paid home care if they liquidated all of their assets, and 58 percent could fund at least two years of an extensive amount of paid home care. Among older adults with significant disabilities, however, only 57 percent could fund at least two years of moderate paid home care by liquidating all of their assets, and 40 percent could fund at least two years of extensive paid home care. Paid home care could become less affordable if growing labor shortages raise future costs.

A prismatic gas-cooled very high temperature reactor (VHTR) is being developed under the next generation nuclear program. One of the concerns for the reactor design is the effects of a loss of flow accident (LOFA) where the coolant circulators are lost for some reason, causing a loss of forced coolant flow through the core. In the previous studies, the natural circulation in the whole reactor vessel (RV) was obtained by segmentation strategies if the computational fluid dynamic (CFD) analysis with a sufficiently refined mesh was conducted, due to the limits of computer capability. The computational domains in the previous studies were segmented sections which were small flow region models, such as 1/12 sectors, or a combination of a few number of the 1/12 sector (ranging from 2 to 15) using geometric symmetry, for a full dome region. The present paper investigates the flow and heat transfer for a much larger flow region model, a 1/12 core model, using high performance computing. The computation meshes for 1/12 sector and 1/12 reactor core are of 7.8 M and ∼531 M, respectively. Over 85,000 and 35,000 iterations for steady and transient (100 s) calculations are required to achieve convergence, respectively. ∼0.1 min CPU time was required using 192 computer cores for the 1/12 sector model and ∼1.3 min CPU time using 768 cores in parallel for the 1/12 core model, for every iteration, using ALPS, Advanced Large-scale Parallel Superclusters. For the LOFA transient condition, this study employs both laminar flow and different turbulence models to characterize the phenomenon of natural convection. The result of Realizable k–ɛ turbulence model (RKE) model is the most conservative one in the heated blocks (channels) regions, but the result of laminar flow is the most conservative one in the plenum regions. The comparisons of the results from large and small models suggest that large flow model is needed to obtain accurate prediction.

Atomic layer deposition (ALD) is a vapor phase technique capable of producing thin films of a variety of materials. Based on sequential, self-limiting reactions, ALD offers exceptional conformality on high-aspect ratio structures, thickness control at the Angstrom level, and tunable film composition. With these advantages, ALD has emerged as a powerful tool for many industrial and research applications. In this review, we provide a brief introduction to ALD and highlight select applications, including Cu(In,Ga)Se2 solar cell devices, high-k transistors, and solid oxide fuel cells. These examples are chosen to illustrate the variety of technologies that are impacted by ALD, the range of materials that ALD can deposit – from metal oxides such as Zn1−xSnxOy, ZrO2, Y2O3, to noble metals such as Pt – and the way in which the unique features of ALD can enable new levels of performance and deeper fundamental understanding to be achieved.

Bypass flow in the prismatic gas-cooled very high temperature reactor (VHTR) is not intentionally designed to occur, but is present in the gaps between graphite blocks. Previous studies of the bypass flow in the core indicated that the cooling provided by flow in the bypass gaps had a significant effect on temperature and flow distributions for normal operating conditions. However, the flow and heat transports in the core are changed significantly after a Loss of Flow Accident (LOFA). This study aims to study the effect and role of the bypass flow after a LOFA in terms of the temperature and flow distributions and for the heat transport out of the core by natural convection of the coolant for a 1/12 symmetric section of the active core which is composed of images and mirror images of two sub-region models. The two sub-region models, 9 × 1/12 and 15 × 1/12 symmetric sectors of the active core, are employed as the CFD flow models using computational grid systems of 70.2 million and 117 million nodes, respectively. It is concluded that the effect of bypass flow is significant for the initial conditions and the beginning of LOFA, but the bypass flow has little effect after a long period of time in the transient computation of natural circulation.

To better understand the contribution of private lands enrolled in conservation easement programs to wintering waterfowl habitat and energetics, we evaluated effects of management strategies on seed biomass, species richness, and presence of beneficial (i.e., considered to have nutritional value to waterfowl) and introduced species on 32 Wetland Reserve Program easements in Arkansas and Mississippi. We collected soil core samples from seasonal wetlands with active and passive management strategies in 2008–2009. Overall mean (±SE) biomass for all seeds was 527.8 (±28.5) kg/ha, whereas mean biomass of beneficial seeds was 263.5 (±18.5) kg/ha. Actively managed sites in Mississippi had greater beneficial seed mass compared to passively managed sites, whereas management had no effect on beneficial seed mass in Arkansas in fall 2008 and in fall 2009, passive sites had greater beneficial seed mass than active sites. Our estimate of beneficial seed biomass on WRP easements represents a 47 % reduction in estimated food availability for waterfowl on privately owned wetlands. Lower estimates of food availability on privately owned, seasonal wetlands in the lower Mississippi Alluvial Valley may warrant increased conservation efforts for seasonal wetlands or additional emphasis on management techniques to increase moist-soil seed biomass on privately owned seasonal wetlands.

Significant uncertainty exists about the effects of bypass flow in a prismatic gas-cooled very high temperature reactor (VHTR). Bypass flow is the flow in the gaps between prismatic graphite blocks in the core. The gaps are present because of variations in their construction, imperfect installation and expansion and shrinkage from thermal heating and neutron fluence. Calculations are performed using computational fluid dynamics (CFD) for flow of the helium coolant in the gap and coolant channels along with conjugate heat generation and heat transfer in the fuel compacts and graphite. A commercial CFD code is used for all of the computations. A one-twelfth sector of a standard hexagonal block column is used for the CFD model because of its symmetry. Various scenarios are computed by varying the gap width from zero to 5 mm, varying the total heat generation rate to examine average and peak radial generation rates and variation of the graphite block geometry to account for the effects of shrinkage caused by irradiation. The calculations are for a 350 MWth prismatic reactor. It is shown that the effect of increasing gap width, while maintaining the same total mass flow rate, causes increased maximum fuel temperature while providing significant coolingmore » to the near-gap region. The maximum outlet coolant temperature variation is increased by the presence of gap flow and also by an increase in total heat generation with a gap present. The effect of block shrinkage is actually to decrease maximum fuel temperature compared to a similar reference case.« less

Phased retirement programs that allow older workers to reduce their hours and responsibilities and pursue more flexible work schedules could satisfy both the employee’s desire for flexibility and the employer’s need to maintain an experienced workforce. However, few employers have established formal programs, because they often complicate the provision of other benefits and might violate antidiscrimination rules. For example, federal laws limit retirement plan distributions to employees who are still working for the plan sponsor, which discourages phased retirement because few older workers can afford to reduce their work hours unless they can receive at least some retirement benefits. Many employers do not provide fringe benefits to part-time employees, and making exceptions for older workers could violate antidiscrimination rules. Federal laws requiring that benefits provided through tax-qualified plans be evenly distributed between highly compensated and lower-paid employees also complicate formal phased retirement programs. Reforming these policies could promote phased retirement.

Data transfer from one distinct mesh to another may be necessary in any number of applications, including prolongation operations supporting multigrid solution methods, spatial adaptation, remeshing, and arbitrary Lagrangian-Eulerian (ALE) and multiphysics simulation. This data transfer process is also referred to as remapping, rezoning and interpolation. Intermesh data transfer has the potential to introduce error into a simulation; the magnitude and importance of which depends on the transfer scenario and the algorithm used to perform the transfer. For a transient analysis, data transfer may occur many times during a simulation, with possible error accumulation at each transfer. The present study develops selected scenarios that illustrate data transfer error and how it might impact an analysis. This study examines remapping error by using static analytical functions to compare various remapping schemes. It also investigates the significance and nature of data transfer error for a simple multiphysics system involving a transient coupled system of partial differential equations. It concludes that remapping error can be significant both for static functions and for coupled multiphysics systems. Aggregate error is shown to be a function of remapping scheme, mesh coarseness, nature of the remapped function and mesh disparity. In cases of extreme mesh disparity, thismore » study shows that remapping can lead to excessive error and even to solution instability. Further, this work motivates that remapping error should be included in the estimation of numerical error, if data transfer is employed in a numerical simulation.« less

The core bypass flow in a prismatic very high temperature reactor (VHTR) is an important design consideration and can have considerable impact on the condition of reactor core internals including fuels. The interstitial gaps are an inherent presence in the reactor core because of tolerances in manufacturing the blocks and the inexact nature of their installation. Furthermore, the geometry of the graphite blocks changes over the lifetime of the reactor because of thermal expansion and irradiation damage. The occurrence of hot spots in the core and lower plenum and hot streaking in the lower plenum (regions of very hot gas flow) are affected by bypass flow. In the present study, three-dimensional computational fluid dynamic (CFD) calculations of a typical prismatic VHTR are conducted to better understand bypass flow phenomena and establish an evaluation method for the reactor core using the commercial CFD code FLUENT. Parametric calculations changing several factors in a one-twelfth sector of a fuel column are performed. The simulations show the impact of each factor on bypass flow and the resulting flow and temperature distributions in the prismatic core. Factors include inter-column gap-width, turbulence model, axial heat generation profile and geometry change from irradiation-induced shrinkage in the graphite block region. It is shown that bypass flow provides a significant cooling effect on the prismatic block and that the maximum fuel and coolant channel outlet temperatures increase with an increase in gap-width, especially when a peak radial factor is applied to the total heat generation rate. Also, the presence of bypass flow causes a large lateral temperature gradient in the block and also dramatically increases the variation in coolant channel outlet temperatures for a given block that may have repercussions on the structural integrity of the graphite, the neutronics and the potential for hot streaking and hot spots occurring in the lower plenum.

Objectives. The impending retirement of boomers has spurred interest in tapping their productive energies to benefi t society. This study examined volunteer transitions among older adults to understand the factors that affect volunteer dynamics. Methods. Using data from the Health and Retirement Study, the analysis examined entries into and exits from formal volunteer activities between 1996 and 2004 by adults aged 55 – 65 at study baseline. The study showed the duration of volunteer activities, the probability that older adults start and stop volunteering, and the factors that signifi cantly predict volunteer transitions. Results. The fi ndings reveal considerable stability among both volunteers and nonvolunteers; however, older adults are more likely to stop volunteering than to start. Volunteers who contribute intensely and for many years and who are married to volunteers are the least likely to quit. And nonvolunteers are more likely to start volunteering if they have been uninvolved for few years and their spouses volunteer. Conclusions. The results point to the need to focus efforts on retaining older volunteers to maximize volunteer engagement during later years. Recruiting older adults in volunteer activities early on, ideally before they retire, could also help meet volunteer needs.

Validation simulations are presented for turbulent flow in a staggered tube bank, geometry similar to the lower plenum of a gas-cooled high temperature reactor. Steady 2D RANS results are compared to unsteady 2D RANS results and experiment. The unsteady calculations account for the fact that nonturbulent fluctuations (due to vortex-shedding) are present in the flow. The unsteady computations are shown to predict the mean variables and the total shear stress quite well. Previous workers’ results indicate that 3D simulations are needed to obtain reasonable agreement; present results indicate 2D is sufficient. Best practices are based on requirements for the ASME Journal of Fluids Engineering.

We radio-tracked nine Masticophis flagellum (Coachwhips) to determine home range, habitat use, and movements in eastern Texas from April to October 2000. Home ranges of Coachwhips contained more oak savanna macrohabitat than early-successional pine plantation or forested seep, based on the availability of these three macrohabitats in the study area. Likewise, within their individual home ranges, Coachwhips used oak savanna more than the other two macrohabitats, based on availability. An analysis of microhabitat use revealed that, relative to random sites within their home range, Coachwhips were found at sites with fewer pine trees and more herbaceous vegetation taller than 30 cm. Results of the two analyses, macrohabitat and microhabitat, were consistent: oak savannas contained relatively few pine trees but much herbaceous vegetation taller than 30 cm. Coachwhips made frequent long-distance moves, which resulted in large home ranges. Core activity areas, however, were small. These core activity areas were always within the oak savanna macrohabitat. Long movements, large home ranges, and small core activity areas likely were a result of the preferred oak savanna macrohabitat being patchily distributed in the landscape.

Although millions of older Americans rely on employer-sponsored retiree health benefits to help pay their medical expenses, declines in this coverage have been documented. Using data from the Medical Expenditure Panel Survey, our findings reveal steady erosion in retiree health benefits since the mid-1990s. Based on this much larger survey of private establishments than previous studies have used, we conclude that in 2003 only about one-quarter of private-sector employees worked at establishments that offered health benefits to retirees, down from 32 percent in 1997. Private firms have also been passing higher shares of health insurance costs to retirees.

Encouraging work at older ages is a crucial policy goal for an aging society, but many features of the benefits and tax system discourage work. This study computes the implicit tax rate on work at older ages, broadly defined to include standard income and payroll taxes as well as changes in future Social Security benefits, employer–provided pension benefits, and health benefits associated with an additional year of employment. The results show that the implicit tax rate on work increases rapidly with age, rising from 14 percent at age 55 for a typical man to nearly 50 percent at age 70.

Collocation methods are investigated because of their simplicity and inherent efficiency for application to a model problem with similarities to the equations of fluid dynamics. The model problem is a steady, one-dimensional convection-diffusion equation with constant coefficients. The objective of the present research is to compare the efficiency and accuracy of several collocation schemes as applied to the model problem for values of 15 and 50 for the associated Peclet number. The application of standard nodal and orthogonal collocation is compared to the use of the Greville abscissae for the collocation points, in conjunction with cubic and quartic B-splines. The continuity of the B-spline curve solution is varied from C1 continuity for traditional orthogonal collocation of cubic and quartic splines to C2-C3 continuity for cubic and quartic splines employing nodal, orthogonal and Greville point collocation. The application of nodal, one-point orthogonal, and Greville collocation for smoothest quartic B-splines is found to be as accurate as for traditional two-point orthogonal collocation using cubics, while having comparable or better efficiency based on operation count. Greville collocation is more convenient than nodal or 1-point orthogonal collocation because exactly the correct number of collocation points is available.

Employers are beginning to search for ways to elicit more labor supply from older adults as the population ages, the ability to work in later life increases, and younger workers become relatively scarce. Many employers are turning to hybrid pension plans, such as cash balance plans and pension equity plans. Whereas traditional defined benefit plans often subsidize workers who retire early and penalize those who remain at work beyond the plan's retirement age, most hybrid plans reward work at older ages. This paper documents the impact of population aging on the labor market and changes over time in work capacity at older ages. It then shows how movement toward hybrid pension plans, among other types of private and public retirement plan reforms and redesigns, can be used to increase work incentives for older adults.

The conversion of traditional defined benefit plans to cash balance plans is among the most controversial aspects of pension policy today. Because the controversy has focused on the treatment of older workers, however, the debate has generally ignored the long–term implications for retirement security. This article examines the potential impact of cash balance plans on workers who spend their entire careers in these plans, and focuses on the implications for mobile workers and for labor supply at older ages. The evidence suggests that cash balance plans can often provide more retirement security than traditional defined benefit plans or defined contribution plans.

This paper describes contributions to employer–sponsored retirement accounts, using newly available longitudinal data that combine administrative earnings records with survey data. The results reveal a fair amount of individual variability in contribution rates over time. However, potential negative shocks to income and increases in current consumption needs do not appear to lead workers to curtail their contributions. Instead, workers appear to raise their contribution rates after they have achieved key milestones in the lifecourse, such as the birth of a child or the purchase of a home.

Recent pension plan conversions by numerous large employers have sparked debate about the merits of cash balance plans. This article compares pension wealth in traditional defined benefit (DB) plans and cash balance plans for a national sample of covered Americans aged 51 to 61. The simulations indicate that replacing DB plans with cash balance plans would redistribute pension wealth from those with long-term jobs to those with multiple short-term jobs and from those with substantial pension benefits to those with more limited benefits. Perhaps unexpectedly, women at midlife in 1992 with DB coverage would lose wealth in cash balance plans, but future cohorts of women are likely to fare better.

The loss of health insurance may be an important component of the cost of retirement, especially for workers without retiree health insurance coverage. The authors find that insurance costs significantly reduce retirement rates for full-time wage and salary workers ages 51 to 61. Simulations suggest that a $1,000 increase in the net present value of health insurance premium costs reduces the probability of early retirement by 0.17 percentage points for men and by 0.24 percentage points for women, corresponding to elasticities of -0.22 and -0.24, respectively. The authors' models predict that expanding the Medicare program to cover those aged 62-64 would increase retirement rates for workers with employer-sponsored coverage who lack retiree benefits, if the government subsidizes their coverage. However, the impact would be small, increasing overall retirement rates by only 7%. (Author's abstract.) (Free full-text download available at http://digitalcommons.ilr.cornell.edu/ilrreview/.)

The authors discuss the application of solution-focused counseling in support groups designed to help graduate students cope with the demands of writing a doctoral dissertation. The doctoral dissertation is probably the most difficult task in the doctoral student's academic career. According to Davis and Parker (1997), as many as one third of doctoral candidates who have completed their course requirements fail to complete the dissertation. Students who do complete their dissertation often take several years to finish their work. Graduate students often must cope with a number of personal problems that may interfere with work on their dissertation. These problems include procrastination, perfectionism, loss of motivation, feelings of isolation, conflicting responsibilities, and discouragement (Green, 1997). In addition to psychological problems, the student working on a dissertation may also experience other problems such as financial, family, health, and academic difficulties. Attempts to manage these problems may include the use of institutional workshops, improved advising, e-mail discussion groups, professional mentors and consultants, graduate student support organizations, self-help books, and support groups (Association for Support of Graduate Students, 2000; Baird, 1997; Nerad & Miller, 1997). In this article, we describe the use of a solution-focused support group as one means of aiding dissertators in overcoming obstacles in their work. Solution-focused counseling, which builds on client strengths in a collaborative fashion, seems to be particularly well suited for graduate students, all of whom have histories of academic success. Solution-focused counseling has been used successfully with a variety of populations, including parents, couples, and students (Murphy, 1997; O'Hanlon & Weiner-Davis, 1989; Webb, 1999). Principles of Solution-Focused Counseling We have adapted the following principles from solution-focused counseling in conducting dissertators' support groups. All of these principles are solution-focused. Instead of assessing "what's wrong," counselors assist the clients in determining "what's working." 1. Look for strengths. Instead of exploring reasons why clients are having difficulty completing their thesis, counselors help clients understand how they have been able to cope effectively in previous situations. 2. Clarify long-term goals. Solutions are more closely related to goals than they are to presenting problems. 3. Set short-term goals. Change is more likely to occur if daily and weekly goals are established that are limited, salient, specific, and attainable. 4. Build on what is possible. Small changes in one part of a problem can produce a "benevolent spiral" that leads to change in other parts of the problem. 5. Create a positive point of view. Counselors assist students in recognizing that most of their work is likely to be good enough at this stage of their career. The "good enough" standard helps to reduce perfectionistic tendencies and to facilitate a more positive approach to the project. Application of Solution-Focused Counseling A professional counselor leads the support group, often with the assistance of an intern who is working on a dissertation. The groups, which meet weekly for 75 minutes, are interdepartmental. Students, who are primarily self-referred, may enter the group at any point during their dissertation work. Students remain in the group until they finish the dissertation or until they no longer feel a need to belong to the group. Maximum group size is eight members. The support group concentrates on the process of writing the dissertation and not on content. The members of the group set goals for each week. In addition to dissertation goals, clients also list other work goals and personal goals that help maintain balanced schedules. Members report both the degree to which they accomplished their goals during the previous week and their satisfaction with these accomplishments by using a scale that ranges from 0% to 100%. …

Linking theories of social stratification, ethnicity, and mental health with theories of human and social capital, the authors examine the impact of economic, cultural, and social factors on five different dimensions of emotional well-being for immigrants and natives at midlife. Based on data from the 1992 wave of the Health and Retirement Study, the authors found that economic factors and human capital variables are the most important determinants of emotional health for both immigrants and natives. The results indicate that cultural factors can enhance emotional well-being. Religious affiliation and participation are important for both immigrants and natives, but religious participation appears to be more beneficial for immigrants. Being part of a couple was also associated with better emotional health, especially for immigrants. The effects of several determinants of emotional health differed across immigrant groups. It was found that marriage, education, and the presence of economically stable kin are particularly important for Cubans.

This paper evaluates the accuracy of estimates of pension wealth based on self-reports by comparing them to estimates based on provider data. Using data from the Health and Retirement Study, we found that few workers are well informed about their future pension benefits. Self-reports were often incomplete and typically varied widely from those based on information from providers. In defined benefit (DB) plans, discrepancies were greatest for workers who had limited education, earned low wages, and did not expect to retire soon. Differences in median pension wealth were smaller at the aggregate level than the individual level, because individual differences tended to offset each other when aggregated. Provider data appear better than self-reports for DB plans, but not for defined contribution (DC) plans. Where both are available, the best method of computing pension wealth may be to estimate DB wealth from provider data and to estimate DC wealth from self-reports.

Several reform plans have been proposed to reduce the financial strain on Social Security. Many proposals under consider- ation, however, would exacerbate the inequality of income among the elderly. Using data from the Current Population Survey, this paper finds that reducing cost-of-living escalators, even when the reforms are designed to protect low-income beneficiaries, would gen- erally worsen inequality over time and increase the number of elders with income below the poverty level. Raising the retirement age would generate similar results. However, increasing taxes on retirement benefits would improve the financial outlook for Social Security with- out imposing additional hardships on the poorest elderly.

Implementation of high-order discretization for the convective transport terms in the inexact Newton method for a benchmark fluid flow and heat transfer problem using various solution configurations at two Reynolds numbers has been investigated. These configurations include fully consistent discretization of the Jacobian, preconditioner and residual of the Newton method, low-order preconditioning using a matrix-free method to approximate the action of the Jacobian, and defect correction or low-order Jacobian and preconditioning. The residual in each case employs high-order discretization to preserve the high-order solution. Two preconditioners, point incomplete lower-upper factorization ILU(k) and block incomplete lower-upper factorization BILU(k) for k = 0,1,2 were applied. Also, one-way multigriding and capping the inner iterations was applied to determine the behavior of the solution performance. It was determined that, overall, the configuration using low-order preconditioning with ILU(1), BILU(1), or BILU(2), mesh sequencing, and inner linear solve iterations capped at the same value of the dimension n, used with the GMRES(n) iterative solver (i.e., no restarts), performed best for time, memory, and robustness considerations.

Finds evidence that the relative generosity of pensions among state and local government workers is related to the ability to underfund public employee retirement plans. Shows a strong, positive relationship among underfunding levels, individual pension wealth, and taxpayer mobility.

This article develops a model, with deferred compensation and severance pay, that predicts that workers bear all the costs and receive all the returns of human capital investments and that specific investments yield higher returns than general investments. This model also predicts that pensions, which efficiently defer compensation, will be positively related to specific investments. Evidence from the National Longitudinal Survey of Older Men confirms these predictions; participation in company-sponsored training programs, proxying for specific investments, increases the probability of pension receipt and the level of benefits. More general training outside the firm has much smaller effects on pensions. Copyright 1996 by University of Chicago Press.

We examine the characteristics of a fully coupled inexact Newton method using defect correction to obtain high-order solutions for two problems: natural convection in a square cavity and mixed-convection flow over a backward step. Newton's method produces a linearized system with a Jacobian matrix and a residual vector, each of which can be formed using different discrete operators. Solution accuracy depends on the discretization used for the residuals. Defect correction employs low-order operators for the Jacobian but high-order operators for the residuals. We employ an O(h3) convection operator in the residual vector and upwinding in the Jacobian. We find that defect correction is an efficient and effective way to achieve high-order solutions.

Polyolefins are used extensively for thin-gauge, high speed, roll- fed thermoforming. However, polyolefins suffer from a variety of problems, in cluding slow processing speed, a narrow processing window and poor stretch ability. Trial results demonstrated that acrylic modified polypropylene has a broader processing window, improved stretchability and faster processing on conventional roll-fed thermoforming equipment. Trials on commercial equip ment, using sheet from 10-50 mils (.25-1.2 mm) are discussed, as well as the economics of the final parts.

A recent article by Leonard and Mokhtari (1990) discusses the order of accuracy of discrete equations used for numerical simulation. They maintain that discrete operators derived for the finite-volume method should be Taylor-series-analysed using the various points that appear in a finite-volume discrete equation. The current paper argues that any discrete scheme must be analysed from a single point. It is shown that while Leonard's finite-difference QUICK scheme is O(h3)-accurate, his implementation of QUICK for the finite-volume method is only O(h2). An alternative finite-volume formulation is shown to yield a locally third-order-accurate operator in the final discrete equation. Also, third-order-accurate formulae are discussed for various numerical implementations. Numerical examples are included to demonstrate actual rates of convergence for various operators.

A finite-element method is developed which improves accuracy and yields superconvergent approximations to two-dimensional elliptic boundary-value problems on a union of square bilinear elements. This method employs an auxiliary equation which is derived using a Taylor series analysis on the discrete formula obtained from a Galerkin finite-element formulation. Application of the finite-element method to the auxiliary equation results in O(h4) convergence for problems with constant coefficients and improved accuracy for problems with variable coefficients. Supporting numerical examples are given.

Volatilization represents a non-reactive loss mechanism for aqueous halogen biocides. Equilibrium volatilities, as measured by effective Henry's law constants, or effective dimensionless partition coefficients ( m ), for free chlorine and free bromine were estimated to be 0.0604 atm ( m = 4.55 × 10 −5 ) and 0.0293 atm ( m = 2.21 × 10 −5 ), respectively, at 20°C using a stripping column. A true Henry's constant of 0.0600 atm ( m = 4.52 × 10 −5 ) was estimated for HOCl by application of equilibrium data to the system. The effective Henry's constant for free chlorine ( H Cl ) is comparable to a previously published value determined under similar conditions. Prior to this investigation, no published values for a free bromine effective Henry's constant ( H Br ) were available.

High-order compact finite difference schemes for two-dimensional convection-diffusion-type differential equations with constant and variable convection coefficients are derived. The governing equations are employed to represent leading truncation terms, including cross-derivatives, making the overall O(h4) schemes conform to a 3 × 3 stencil. We show that the two-dimensional constant coefficient scheme collapses to the optimal scheme for the one-dimensional case wherein the finite difference equation yields nodally exact results. The two-dimensional schemes are tested against standard model problems, including a Navier-Stokes application. Results show that the two schemes are generally more accurate, on comparable grids, than O(h2) centred differencing and commonly used O(h) and O(h3) upwinding schemes.

Purpose: Retirees in traditional pension plans must generally choose between single life annuities, which provide regular payments until death, and joint and survivor annuities, which pay less each month but continue to make payments to the spouse after the death of the retired worker. This article examines the payout decision and measures the share of married retirees with pension annuities who forego survivor protection. Design and Methods: The analysis consists of a probit model of the pension payout decision, based on data from the 1992–2000 waves of the Health and Retirement Study. Results: More than one quarter (28%) of married men and two thirds of married women receiving employer-sponsored retirement annuities declined survivor protection. Men with small pensions and limited household wealth, men in better health than their spouses, and men whose spouses have pension coverage from their own employers are more likely than other men to reject survivor protection. Implications: Most workers appear to make payout decisions by rationally balancing the costs and benefits of each type of annuity, suggesting that existing measures to encourage joint and survivor annuities are adequate. However, the growth in 401(k) plans, which are generally not covered by existing laws protecting spousal pension rights, may leave widows vulnerable.

Objectives. Recent changes in retirement trends and patterns have raised questions about the likely retirement behavior of baby boomers, the large cohort born between 1946 and 1964. This study examined recent changes in retirement expectations and the factors that drove them. Methods. Using data from the Health and Retirement Study, the analysis compared self-reported probabilities of working full time past ages 62 and 65 among workers aged 51 to 56 in 1992 and 2004. The study modeled retirement expectations for both generations and used the estimated regression coefficients to identify the forces that accounted for generational differences. Results. Between 1992 and 2004, the mean self-reported probability of working full time past age 65 among workers aged 51 to 56 increased from 27% to 33%. Lower rates of retiree health insurance offers from employers, higher levels of educational attainment, and lower rates of defined benefit pension coverage accounted for most of the growth. Discussion. Given the continued erosion in employer-sponsored retiree health benefits and defined benefit pension plans, boomers will likely remain at work longer than members of the previous generation. Lengthier careers will likely promote economic growth, increase government revenue, and improve individual financial security at older ages.

Additives can be used to provide significant performance enhancements to plastics. For PVC, particular performance benefit can be gained from additives that raise HDT, increase impact, improve color fastness, and improve processing. This paper comments on what improvements are desired in these areas, and what benefits and market opportunities would then result.

This paper explores the prevalence and consequences of age discrimination in the workplace by analyzing self-reports of discrimination by respondents in the National Longitudinal Survey of Older Men. Age discrimination was reported in seven percent of our cases, during the period 1966-1980. Workers with positive reports were much more likely to separate from their employer and less likely to remain employed than workers who report no age discrimination. The estimated effect of reported discrimination remains large and significant even when controlling for the existence of mandatory retirement provisions on the current job. These findings are generally robust to numerous attempts to correct the estimates for the inherent limitations of self-reported data, particularly the potential heterogeneity bias that arises from differences in the propensity to report discrimination, and the possibility that discrimination is reported in response to other negative labor market outcomes.

We examine the evidence on whether real wages decline with age among older men. While the general human capital model of wage growth over the life cycle predicts that wages will fall as workers approach the end of their career, alternative models of wage growth do not predict these wage declines. We find that in longitudinal estimates of age-wage profiles wage declines only set in for workers in their 60s. Furthermore, these longitudinal declines are at least partly due to interactions with the Social Security system. The earnings cap or other effects of Social Security appear to lead some workers to choose jobs and job characteristics associated with lower wages. Copyright 1996 by MIT Press.

Axial magnetic resonance (MR) images of non-neoplastic spinal cord cavities were reviewed in 115 patients with otherwise complete neurological and neuroradiological findings. The variations in axial morphology revealed three distinct cavitary patterns. These patterns were as follows: 1) symmetrically enlarged central cavities (28 patients); 2) central cavities that expanded paracentrally in one or more focal areas (36 patients); and 3) eccentric cavities that were off-center, frequently irregular, and sometimes associated with myelomalacia (51 patients). The radiological patterns of spinal cord cavitation correlated well with recently reported histopathological findings that distinguish simple dilations of the central canal, dilations of the central canal that dissect paracentrally, and primary cavitations of the spinal cord parenchyma (extracanalicular syringes). Like histologically confirmed central canal syringes, MR-defined central cavities were associated with pathogenic factors that affect the dynamics of the cerebrospinal fluid, including hindbrain malformations, hydrocephalus, and extramedullary obstructive lesions. Eccentric cavities resembled extracanalicular syringes and occurred typically with disorders that damage spinal cord tissue (e.g., trauma, infarction, meningitis/arachnoiditis, spondylosis/disc herniation, radiation necrosis, and transverse myelitis). Analysis of clinical findings at the time of MR imaging established the following correlations. 1) Symmetrically enlarged central cavities were asymptomatic or produced nonspecific neurological signs. 2) Central cavities that expanded paracentrally were associated with segmental signs referable to the paracentral component. 3) Eccentric cavities produced various combinations of long tract and segmental signs that could usually be related to the level, side, and specific quadrant of spinal cord cavitation.(ABSTRACT TRUNCATED AT 250 WORDS)

We report two patients in whom bullets in the brain migrated into the adjacent lateral ventricle and moved freely as a consequence of gravity. A review of the literature suggests that the spontaneous migration of intracerebral bullets is influenced by cerebral softening, the specific gravity of the bullet compared with brain tissue, and the sink function of the cerebral ventricles. In patients undergoing the surgical removal of intracerebral or intraventricular bullets, it is recommended that an x-ray be obtained after the final positioning of the head. Language: en

The ability of a human observer to perform tasks involving visual search and the determination of visual ranges (i.e., visibilities), is a commonly recognized skill that is presently under increasing competition from a variety of sophisticated electro-optical systems. The paper reviews a few of the pertinent psychophysical characteristics related to the human observer's performance, how they are related to some instrumentally measured quantities, and two of the more commonly encountered sources of error in visual determinations of visibility. Comparisons between several observer and instrumental determinations illustrate the link between the two experimental regimes and introduce some appropriate specialized data obtained with an airborne nephelometer. Since the determination of visibility is the simpler special case of determining horizontal path contrast transmittance, several characteristics of the nephelometer data which influence its use in the more general determination of slant path contrast transmittance are illustrated. In this context, the implication of these data in ones ability to accurately model atmospheric influences upon contrast transmittance is introduced. The basic conclusions to be drawn from this paper are twofold. First, that although human visual performance is a complex psychophysical task, there is little doubt that for visibility determinations it can be adequately related to instrumental measurements of atmospheric volume scattering coefficient and second, that a reliable specification of the directional scattering properties of the atmospheric aerosol can be reasonably deduced from this measurement of total volume scattering coefficient alone.