Looking Back and Pressing Forward: Lessons for Today Found in the Story of Barbara Smith Conrad

Educatio

EDUCATION ON PUBLIC POLICY IN AGRICULTURE THROUGH THE LEAGUE OF WOMEN VOTERS

Teaching/Communication/Extension/Profession,

Incompressibility in finite nuclei and nuclear matter

The incompressibility (compression modulus) $K_{\rm 0}$ of infinite symmetric nuclear matter at saturation density has become one of the major constraints on mean-field models of nuclear many-body systems as well as of models of high density matter in astrophysical objects and heavy-ion collisions. We present a comprehensive re-analysis of recent data on GMR energies in even-even $^{\rm 112-124}$Sn and $^{\rm 106,100-116}$Cd and earlier data on 58 $\le$ A $\le$ 208 nuclei. The incompressibility of finite nuclei $K_{\rm A}$ is expressed as a leptodermous expansion with volume, surface, isospin and Coulomb coefficients $K_{\rm vol}$, $K_{\rm surf}$, $K_\tau$ and $K_{\rm coul}$. \textit{Assuming} that the volume coefficient $K_{\rm vol}$ is identified with $K_{\rm 0}$, the $K_{\rm coul}$ = -(5.2 $\pm$ 0.7) MeV and the contribution from the curvature term K$_{\rm curv}$A$^{\rm -2/3}$ in the expansion is neglected, compelling evidence is found for $K_{\rm 0}$ to be in the range 250 $< K_{\rm 0} <$ 315 MeV, the ratio of the surface and volume coefficients $c = K_{\rm surf}/K_{\rm vol}$ to be between -2.4 and -1.6 and $K_{\rm \tau}$ between -840 and -350 MeV. We show that the generally accepted value of $K_{\rm 0}$ = (240 $\pm$ 20) MeV can be obtained from the fits provided $c \sim$ -1, as predicted by the majority of mean-field models. However, the fits are significantly improved if $c$ is allowed to vary, leading to a range of $K_{\rm 0}$, extended to higher values. A self-consistent simple (toy) model has been developed, which shows that the density dependence of the surface diffuseness of a vibrating nucleus plays a major role in determination of the ratio K$_{\rm surf}/K_{\rm vol}$ and yields predictions consistent with our findings.Comment: 26 pages, 13 figures; corrected minor typos in line with the proof in Phys. Rev.

The plasma dynamics of hypersonic spacecraft: Applications of laboratory simulations and active in situ experiments

Attempts to gain an understanding of spacecraft plasma dynamics via experimental investigation of the interaction between artificially synthesized, collisionless, flowing plasmas and laboratory test bodies date back to the early 1960's. In the past 25 years, a number of researchers have succeeded in simulating certain limited aspects of the complex spacecraft-space plasma interaction reasonably well. Theoretical treatments have also provided limited models of the phenomena. Several active experiments were recently conducted from the space shuttle that specifically attempted to observe the Orbiter-ionospheric interaction. These experiments have contributed greatly to an appreciation for the complexity of spacecraft-space plasma interaction but, so far, have answered few questions. Therefore, even though the plasma dynamics of hypersonic spacecraft is fundamental to space technology, it remains largely an open issue. A brief overview is provided of the primary results from previous ground-based experimental investigations and the preliminary results of investigations conducted on the STS-3 and Spacelab 2 missions. In addition, several, as yet unexplained, aspects of the spacecraft-space plasma interaction are suggested for future research

School Choice and Student Performance: Are Private Schools Really Better?

Are private schools really better than public schools, or is it simply that better students attend private schools? Although a number of recent studies find that students perform better in private schools (more specifically, Catholic schools), others do not. Typically, however, the instruments used to adjust for nonrandom selection are weak. This study employs uniquely detailed local instruments and jointly models selection into religious and nonreligious private high schools, relative to public high schools—improving instrument power in predicting private sector attendance to roughly three times that of prior studies. Failing to correct adequately for selection leads to a systematic upward bias in the estimated treatment effect for religious schools, but a downward bias for nonreligious private schools. With adequate correction, religious schools are modestly inferior in mathematics and science, while nonreligious schools are substantially superior. However, minority students, particularly in urban areas, benefit from religious schools. Other factors that may make both religious and nonreligious private schools attractive include possibly better retention rates, increased security and discipline, and greater opportunities for a variety of specialized school-day and extracurricular activities.

Tests of a single tube-in-shell water-boiling heat exchanger with a helical-wire insert and several inlet flow-stabilizing devices

Single tube-in-shell water-boiling heat exchanger performance with helical wire insert and flow stabilizing device

Local heat transfer for water in entrance regions of tubes with tapered flow areas and nonuniform heat fluxes

Convective heat transfer data for water flow in heated circular tubes with varying heat fluxes and flow area

Experimental study of blade-type helical flow inducers in a 5/8-inch electrically heated boiler tube

Effects of blade-type flow swirlers on maximum exit quality of 5/8-inch boiler tube