Vibrational density of states of silicon nanoparticles

The vibrational density of states of silicon nanoparticles in the range from 2.3 to 10.3 nm is studied with the help of molecular-dynamics simulations. From these simulations the vibrational density of states and frequencies of bulk-like vibrational modes at high-symmetry points of the Brillouin-zone have been derived. The results show an increase of the density of states at low frequencies and a transfer of modes from the high-frequency end of the spectrum to the intermediate range. At the same time the peak of transverse optical modes is shifted to higher frequencies. These observations are in line with previous simulation studies of metallic nanoparticles and they provide an explanation for a previously observed discrepancy between experimental and theoretical data [C. Meier et al., Physica E, 32, 155 (2006)].Comment: 7 pages, 5 figure; accepted for publication in Phys. Rev.

Compliance with child support orders in divorce cases

This paper examines compliance with child support orders by divorced fathers in Wisconsin. Compliance increases as the income of the father increases, although it falls in the highest income category. The "burden" of awards does not affect compliance unless more than 30 percent of income is owed. More stringent enforcement systems increase compliance. We find that most divorced fathers who are not complying with their orders do not have very low incomes, in contrast to noncomplying fathers in nonmarital cases. This suggests that the best policies to increase compliance among divorced fathers may differ from those for nonmarital fathers.

Health insurance and child support

The child support system has been increasing its efforts to make health insurance a part of child support awards. Data from the 1990 Current Population Survey Child Support Supplement show that 40 percent of child support awards require that the noncustodial parent provide health insurance to his children. However, in a third of the cases, the noncustodial parents are not providing coverage. This matters because 16 percent of the children whose noncustodial fathers are not providing the coverage they were ordered to provide are not insured through other sources (e.g., Medicaid). But expecting noncustodial parents to be the sole providers of health insurance for their children may be unwise. Data from Wisconsin suggest that fewer than half (and probably less than 10 percent) of uninsured children in custodial- parent families have a noncustodial parent who can afford to provide health insurance for them. Health care reform is needed so that all children will have coverage, whether it is provided by their parents or the government.

Mississippi River Research Conclusions Executive Summary

Briefing paper requested by Senator Bond detailing the conclusions from the Mississippi River research to date.Agricultural and Food Policy, Environmental Economics and Policy,

Interaction effects of a child tax credit, national health insurance, and assured child support

If the government offered a refundable tax credit for children, national health insurance, and an assured child support benefit to all families with children - poor families as well as nonpoor families - what would happen to poverty, welfare dependency, and other related issues? The authors simulate the effects of each program operating on its own and of all three acting in concert. They find that the impacts of the programs interacting with one another would be much larger than the sum of the impacts produced by each program alone. With the three programs in place, the poverty rate would fall by 43 percent, the AFDC caseload would shrink by 22 percent, and the annual incomes of poor families would rise by $2500. In addition, AFDC recipients would work more hours. Data come from the 1987 Survey of Income and Program Participation.

Quantum Chinos Game: winning strategies through quantum fluctuations

We apply several quantization schemes to simple versions of the Chinos game. Classically, for two players with one coin each, there is a symmetric stable strategy that allows each player to win half of the times on average. A partial quantization of the game (semiclassical) allows us to find a winning strategy for the second player, but it is unstable w.r.t. the classical strategy. However, in a fully quantum version of the game we find a winning strategy for the first player that is optimal: the symmetric classical situation is broken at the quantum level.Comment: REVTEX4.b4 file, 3 table

Supporting children born outside of marriage: Do child support awards keep pace with changes in fathers' incomes?

Many children born to mothers who are not married are very poor, and in many instances their mothers do not receive child support. Some excuse this by asserting that the fathers of these children do not and never will earn enough to pay adequate support. But the records of paternity cases that came to court in Wisconsin between 1980 and 1988 show that half of the fathers aged twenty-five and older had incomes over $10,000. More important, the men who had the lowest incomes when they became fathers--such men were usually teenagers--were the ones whose incomes increased the most over the years. Even so, the records reveal that there was no relationship between changes in the incomes of the fathers and changes in the amounts of child support awards, a situation the Family Support Act of 1988 is seeking to rectify.

Life after Welfare: The Economic Well-Being of Women and Children Following an Exit from AFDC

Much previous research has focused on the length of welfare spells and returns to welfare following an exit. Few quantitative studies have looked at broader indicators of the economic well-being of those who have exited AFDC. In this paper we use data from the National Longitudinal Survey of Youth (NSLY) to trace welfare use, poverty status, and primary sources of income in the five years following an exit from welfare. We find that while there is a trend toward improved economic status over time, 40 percent of women remain poor five years after exit. Women with more advantaged family backgrounds, those with fewer children, or with more education at exit are more likely to consistently escape poverty. Median income increases over the first five years from about $10,500 to about$15,000 (1992 dollars). Own earnings are the most prevalent income source, followed by spouse's earnings, and mean-tested transfers.

Drag reductions obtained by modifying a box-shaped ground vehicle

A box-shaped ground vehicle was used to simulate the aerodynamic drag of high volume transports, that is, delivery vans, trucks, or motor homes. The coast-down technique was used to define the drag of the original vehicle, having all square corners, and several modifications of the vehicle. Test velocities ranged up to 65 miles per hour, which provided maximum Reynolds numbers of 1 times 10 to the 7th power based on vehicle length. One combination of modifications produced a reduction in aerodynamic drag of 61 percent as compared with the original square-cornered vehicle