Exclusion Statistics in a trapped two-dimensional Bose gas

We study the statistical mechanics of a two-dimensional gas with a repulsive delta function interaction, using a mean field approximation. By a direct counting of states we establish that this model obeys exclusion statistics and is equivalent to an ideal exclusion statistics gas.Comment: 3 pages; minor changes in notation; typos correcte

A new puzzle for random interaction

We continue a series of numerical experiments on many-body systems with random two-body interactions, by examining correlations in ratios in excitation energies of yrast $J$ = 0, 2, 4, 6, 8 states. Previous studies, limited only to $J$ = 0,2,4 states, had shown strong correlations in boson systems but not fermion systems. By including $J \ge 6$ states and considering different scatter plots, strong and realistic correlations appear in both boson and fermion systems. Such correlations are a challenge to explanations of random interactions.Comment: 4 pages, 4 figure

Comparison of measured and calculated helicopter rotor impulsive noise

The thickness noise theory is discussed. Two full-scale rotors were tested in a wind tunnel with several tips involving changes in chord, thickness, and sweep. Impulsive noise data reduction procedures used are described. The calculated and measured impulsive noise peak pressures as a function of advancing tip Mach number are compared, showing good correlation for all rotors considered

Free-energy landscape of nucleation with an intermediate metastable phase studied using capillarity approximation

Capillarity approximation is used to study the free-energy landscape of nucleation when an intermediate metastable phase exists. The critical nucleus that corresponds to the saddle point of the free-energy landscape as well as the whole free-energy landscape can be studied using this capillarity approximation, and various scenarios of nucleation and growth can be elucidated. In this study we consider a model in which a stable solid phase nucleates within a metastable vapor phase when an intermediate metastable liquid phase exists. We predict that a composite critical nucleus that consists of a solid core and a liquid wetting layer as well as pure liquid and pure solid critical nuclei can exist depending not only on the supersaturation of the liquid phase relative to that of the vapor phase but also on the wetting behavior of the liquid surrounding the solid. The existence of liquid critical nucleus indicates that the phase transformation from metastable vapor to stable solid occurs via the intermediate metastable liquid phase, which is quite similar to the scenario of nucleation observed in proteins and colloidal systems. By studying the minimum-free-energy path on the free-energy landscape, we can study the evolution of the composition of solid and liquid within nuclei not limited to the critical nucleus.Comment: 9 pages, 8 figures, Journal of chemical physics to be publishe

Age Disparities in Unemployment and Reemployment During the Great Recession and Recovery

Analyzes patterns in the percentage of workers unemployed at any point between May 2008 and March 2011, number of months they were unemployed, wage losses at reemployment, and likelihood of workers leaving the labor force by age group

Surface Erosion and Sedimentation Associated with Forest Land Use in Interior Alaska

Completion reportThe magnitude of sheet-rill erosion associated with various landscape manipulations is presented. The Universal Soil Loss Equation's usefulness for predicting annual sheet-rill erosion within interior Alaska is confirmed. Investigations of sheet-rill erosion indicate that removing the trees from forested areas with only minor ground cover disturbance did not increase erosion. Removing the ground cover, however, increased erosion 18 times above that on forested areas. Erosion is substantially reduced when disturbed areas are covered with straw mulch and fertilizer. Comparison of the actual erosion and the quantity of erosion predicted with the Universal Soil Loss Equation indicates that the equation overestimates annual erosion by an average of 21 percent. It overestimates individual storm erosion by an average of 174 percent. Data are also presented concerning sheet-rill erosion in a permafrost trail, distribution of the rainfall erosion index, and suggested cover and management factor values.This work was supported by the Institute of Northern Forestry, Pacific Northwest Forest and Range Experiment Station, USDA. The Institute of Water Resources, University of Alaska, provided facilities for this research

How Much Might Automatic IRAs Improve Retirement Security for Low- and Moderate-Wage Workers?

Estimates the extent to which requiring employers with no retirement plan to set up individual retirement accounts and automatically deposit a portion of pay would improve low- and moderate-wage workers' retirement security. Outlines policy implications

Lattice distortions in YBa2Cu3O7–delta thin films grown in situ by sequential ion beam sputtering

We have analyzed epitaxial, c-axis oriented YBa2Cu3O7–delta thin films grown in situ by sequential ion-beam sputtering on (100) SiTiO3 and (100) MgO substrates. X-ray diffraction studies showed the presence of both homogeneous and inhomogeneous lattice distortions along the c-direction. The c-axis lattice parameters ranged from 11.72 to 12.00 Å. The broadening of the (00l) Bragg peaks in excess of the broadening due to finite film thickness was found to be due to inhomogeneous lattice distortions. The overall trend in the data shows an increase of the inhomogeneous strains with the enlargement of the c-axis lattice parameter. The inhomogeneous lattice distortions are interpreted as fluctuations in the c-axis lattice parameter. The resistive transitions were found to be correlated to the lattice distortions. We show correlations between the midpoint Tc and the c-axis lattice parameter and between the transition widths and the inhomogeneous lattice distortions

Rotorcraft research testing in the National Full-Scale Aerodynamics Complex at NASA Ames Research Center

The unique capabilities of the National Full-Scale Aerodynamics Complex (NFAC) for testing rotorcraft systems are described. The test facilities include the 40- by 80-Foot Wind Tunnel, the 80- by 120-Foot Wind Tunnel, and the Outdoor Aerodynamic Research Facility. The Ames 7- by 10-Foot Subsonic Wind Tunnel is also used in support of the rotor research programs conducted in the NFAC. Detailed descriptions of each of the facilities, with an emphasis on helicopter rotor test capability, are presented. The special purpose rotor test equipment used in conducting helicopter research is reviewed. Test rigs to operate full-scale helicopter main rotors, helicopter tail rotors, and tilting prop-rotors are available, as well as full-scale and small-scale rotor systems for use in various research programs. The test procedures used in conducting rotor experiments are discussed together with representative data obtained from previous test programs. Specific examples are given for rotor performance, loads, acoustics, system interactions, dynamic and aeroelastic stability, and advanced technology and prototype demonstration models