Comparison of hydrogen and methane as coolants in regeneratively cooled panels

Comparison of hydrogen and methane as coolants in regeneratively cooled panel

Solidification in soft-core fluids: disordered solids from fast solidification fronts

Using dynamical density functional theory we calculate the speed of solidification fronts advancing into a quenched two-dimensional model fluid of soft-core particles. We find that solidification fronts can advance via two different mechanisms, depending on the depth of the quench. For shallow quenches, the front propagation is via a nonlinear mechanism. For deep quenches, front propagation is governed by a linear mechanism and in this regime we are able to determine the front speed via a marginal stability analysis. We find that the density modulations generated behind the advancing front have a characteristic scale that differs from the wavelength of the density modulation in thermodynamic equilibrium, i.e., the spacing between the crystal planes in an equilibrium crystal. This leads to the subsequent development of disorder in the solids that are formed. For the one-component fluid, the particles are able to rearrange to form a well-ordered crystal, with few defects. However, solidification fronts in a binary mixture exhibiting crystalline phases with square and hexagonal ordering generate solids that are unable to rearrange after the passage of the solidification front and a significant amount of disorder remains in the system.Comment: 18 pages, 14 fig

Journey Beyond the Fair

Journey Beyond the Fair will combine a vast virtual world environment and hand-held devices to develop a tightly coupled home-school-museum paradigm that enhances traditional exhibits. This paradigm is designed to work as a national model where informal humanities education institutions can add depth of learning and heighten the level of interactivity and personalization of an onsite experience by strengthening the connections to a home/school-based virtual world experience. While in this instance we are addressing the 1964/65 New York World's Fair, institutions can adapt the concept based on subjects pertinent to their facility, culture and demographic visitation needs

Development program for 35 watt traveling-wave tube space amplifier Final report, 30 Jun. 1967 - 30 Sep. 1969

Development of 35-watt, S band, traveling wave tube amplifier for Saturn 5 instrument uni

Study of high-speed angular-contact ball bearings under dynamic load

Research program studies behavior of specific high-speed, angular-contact ball bearings. Program is aimed at detailed investigation of ball-separator behavior and lubrication surface-finish effects in a specific gyro wheel

Ideology, Qualifications, and Covert Senate Obstruction of Federal Court Nominations

Scholars, policymakers, and journalists have bemoaned the emphasis on ideology over qualifications and party over performance in the judicial appointment process. Though, for years, the acrimony between the two parties and between the Senate and President remained limited to appointments to the United States Supreme Court, the modern era of judicial appointments has seen the so-called “appointments rigor mortis” spread throughout all levels of judicial appointments. A host of studies have examined the causes and consequences of the growing acrimony and obstruction of lower federal court appointments, but few rely on archival data and empirical evidence to examine the underlying friction between the parties and the two branches. In a unique study, the authors examine archival data to determine the conditions under which Senators obstruct judicial nominations to lower federal courts. More specifically, the authors examine one form of Senate obstruction — the blue slip — and find that Senators use their blue slips to block ideologically distant nominees as well as unqualified nominees. More importantly, however, the authors find that among nominations to federal circuit courts, Senators block highly qualified nominees who are ideologically distant from them just as often as they block unqualified nominees who are ideologically distant from them. That is, stellar qualifications do not appear to mitigate the negative effects of ideological distance. The fact that blue slips occur in private, away from public view, allows Senators to block nominees entirely on ideological grounds, without fear of individualized public retribution. Senators, in short, have taken an aggressive role in blocking highly qualified nominees who would otherwise make significant — but opposing — policy and who might one day become credible nominees to the Supreme Court were their nominations to move forward. By killing these nominations in the cradle, and outside the public view, Senators can block or delay the confirmation of judges with whom they disagree ideologically. The authors point out that policymakers and scholars who seek to reform the judicial appointment process must therefore be very clear about their goals. If a reform’s goal is to minimize the role of Senate ideology in the appointment process, then proposals that insulate the process from the public eye are likely to backfire. For, as the data show, Senators take advantage of insulation to achieve ideological goals. On the other hand, if a reform’s goal is to maximize the role of Senate ideology — perhaps to offset the President’s first mover advantage or to recognize and directly address the fact that courts are policymaking bodies — then proposals that insulate the process from the public eye are likely to accomplish that goal

Competing exchange interactions on the verge of a metal-insulator transition in the two-dimensional spiral magnet Sr3_3Fe2_2O7_7

We report a neutron scattering study of the magnetic order and dynamics of the bilayer perovskite Sr$_3$Fe$_2$O$_7$, which exhibits a temperature-driven metal-insulator transition at 340 K. We show that the Fe$^{4+}$ moments adopt incommensurate spiral order below $T_\text{N}=115$ K and provide a comprehensive description of the corresponding spin wave excitations. The observed magnetic order and excitation spectra can be well understood in terms of an effective spin Hamiltonian with interactions ranging up to third nearest-neighbor pairs. The results indicate that the helical magnetism in Sr$_3$Fe$_2$O$_7$ results from competition between ferromagnetic double-exchange and antiferromagnetic superexchange interactions whose strengths become comparable near the metal-insulator transition. They thus confirm a decades-old theoretical prediction and provide a firm experimental basis for models of magnetic correlations in strongly correlated metals.Comment: PRL, in pres

Mental Health and Weather Extremes in a Southeastern U.S. City: Exploring Group Differences by Race

The connection between mental health and weather extremes is a public health concern, but less studied to date than physical health. This exploratory study examines the mental health impacts of two kinds of weather extremes increasingly linked to climate change—summer heat waves and extreme winter weather—in a low-to middle-income population in the Southeastern U.S. The distribution of mental health impacts, and potential pathways to them, are examined with a focus on race. Data are from a random-sample survey of 426 participants and are analyzed with bivariate statistics and path analysis. Self-reported mental health impacts, in both seasons, were common in our study, with White participants tending to report worse impacts than participants who identified with other racial groups. Physical health had direct effects on mental health across several models, overall and by racial group. For summer heat waves, concern about climate change and social cohesion had direct and indirect effects, respectively, on mental health in White participants only. For extreme winter weather, preparedness had a direct negative effect on mental health in White, but not Black, participants. Results suggest that there may be racial differences in the influence of human and social capital factors on mental health related to weather extremes, warranting further study of this critical topic and with larger racial subgroup samples

Upending a Global Debate: An Empirical Analysis of the U.S. Supreme Court’s Use of Transnational Law to Interpret Domestic Doctrine,

Over the last ten years, judges, scholars, and policymakers have argued — quite vehemently at times — about whether U.S. courts should use transnational sources of law to interpret domestic legal doctrine. All eyes in this debate focus on the U.S. Supreme Court and its use, misuse, and alleged use of transnational law. And almost all the debates are normative. Some scholars and judges argue the Court is correct to use transnational law. Others believe to do so is constitutional apostacy. Still, the controversy seems to have generated more heat than light. Among the clamor can be found little empirical work on the conditions under which Supreme Court Justices actually use transnational law. Is it in fact the case that only liberal Justices employ transnational law — or do conservatives as well? In addition, there is little work on which countries Justices cite when they do use transnational law. Do they cherry pick whichever country works best in the given case, or is there a lower bound of plausibility when selecting countries to examine and cite? The authors provide the most systematic empirical exploration of the Court’s use of transnational law to date. Their results challenge conventional wisdom and prove to upend the existing debates over transnational law. The data show that Justices are more likely to reference transnational law when they exercise judicial review and when they overturn precedent, which likely explains much of the controversy around the practice. Importantly, the data show, further, that all Justices cite transnational law. Liberals cite transnational law when they render liberal decisions, and conservatives cite transnational law when they render conservative decisions. Liberals and conservatives alike employ such law because they are both ideologically conscious, strategic judicial actors who seek to support their decisions with as much persuasive material as possible. Finally, the results suggest that Justices cite countries with regard to their political and legal characteristics. They cite what the public would consider to be among the most legitimate countries across the globe. In other words, on the whole, Justices seem to borrow from countries most like the U.S. Whether these results are good or bad is unclear; what is clear, however, is that the normative debate over using transnational law must take a turn and address the authors’ findings

Invariant Measures and Decay of Correlations for a Class of Ergodic Probabilistic Cellular Automata

We give new sufficient ergodicity conditions for two-state probabilistic cellular automata (PCA) of any dimension and any radius. The proof of this result is based on an extended version of the duality concept. Under these assumptions, in the one dimensional case, we study some properties of the unique invariant measure and show that it is shift-mixing. Also, the decay of correlation is studied in detail. In this sense, the extended concept of duality gives exponential decay of correlation and allows to compute explicitily all the constants involved