Morphologic studies of the Moon and planets

The impact, volcanic, and tectonic history of the Moon and planets were investigated over an eight year period. Research on the following topics is discussed: lunar craters, lunar basins, lunar volcanoes, correlation of Apollo geochemical data, lunar geology, Mars desert landforms, and Mars impact basins

Desert landforms of southwest Egypt: A basis for comparison with Mars

Geologic interpretations of The Gilf Kebir-Uweinat of Apollo-Soyuz photographs were verified. The photographs and LANDSAT images showed features reminiscent of those depicted by Mariner and Viking missions to Mars. These features were to better understand their morphologic analogs on Mars. It is indicated that climate change played a significant role in the formation of the eastern Sahara. It is also revealed that correlations between the eolian features in southwestern Egypt and the wind blown patterns on the surface of Mars result in a better understanding of eolian activity on both planets

An extension to the Navier-Stokes equations to incorporate gas molecular collisions with boundaries

We investigate a model for micro-gas-flows consisting of the Navier-Stokes equations extended to include a description of molecular collisions with solid boundaries, together with first and second order velocity slip boundary conditions. By considering molecular collisions affected by boundaries in gas flows we capture some of the near-wall affects that the conventional Navier-Stokes equations with a linear stress/strain-rate relationship are unable to describe. Our model is expressed through a geometry-dependent mean-free-path yielding a new viscosity expression, which makes the stress/strain-rate constitutive relationship non-linear. Test cases consisting of Couette and Poiseuille flows are solved using these extended Navier-Stokes equations, and we compare the resulting velocity profiles with conventional Navier-Stokes solutions and those from the BGK kinetic model. The Poiseuille mass flow-rate results are compared with results from the BGK-model and experimental data, for various degrees of rarefaction. We assess the range of applicability of our model and show that it can extend the applicability of conventional fluid dynamic techniques into the early continuum-transition regime. We also discuss the limitations of our model due to its various physical assumptions, and we outline ideas for further development

Discovery of an equal-mass "twin" binary population reaching 1000+ AU separations

We use a homogeneous catalog of 42,000 main-sequence wide binaries identified by Gaia to measure the mass ratio distribution, p(q), of binaries with primary masses $0.1<M_1/M_{\odot}<2.5$, mass ratios $0.1 \lesssim q<1$, and separations $50<s/{\rm AU}<50,000$. A well-understood selection function allows us to constrain p(q) in 35 independent bins of primary mass and separation, with hundreds to thousands of binaries in each bin. Our investigation reveals a sharp excess of equal-mass "twin" binaries that is statistically significant out to separations of 1,000 to 10,000 AU, depending on primary mass. The excess is narrow: a steep increase in p(q) at $0.95 \lesssim q<1$, with no significant excess at $q\lesssim 0.95$. A range of tests confirm the signal is real, not a data artifact or selection effect. Combining the Gaia constraints with those from close binaries, we show that the twin excess decreases with increasing separation, but its width ($q\gtrsim 0.95$) is constant over $0.01<a/{\rm AU}<10,000$. The wide twin population would be difficult to explain if the components of all wide binaries formed via core fragmentation, which is not expected to produce strongly correlated component masses. We conjecture that wide twins formed at closer separations ($a \lesssim 100$ AU), likely via accretion from circumbinary disks, and were subsequently widened by dynamical interactions in their birth environments. The separation-dependence of the twin excess then constrains the efficiency of dynamical widening and disruption of binaries in young clusters. We also constrain p(q) across $0.1 \lesssim q<1$. Besides changes in the twin fraction, p(q) is independent of separation at fixed primary mass over $100 \lesssim s/{\rm AU} < 50,000$. It is flatter than expected for random pairings from the IMF but more bottom-heavy for wide binaries than for binaries with $a\lesssim$100 AU.Comment: 24 pages, 17 figures, plus appendices. Accepted to MNRAS. Fig 17 and Appendix F are new since v

Direct Extraction of QCD Lambda MS-bar from e+e- Jet Observables

We directly fit the QCD dimensional transmutation parameter, Lambda MS-bar, to experimental data on e+e- jet observables, making use of next-to-leading order (NLO) perturbative calculations. In this procedure there is no need to mention, let alone to arbitrarily vary, the unphysical renormalisation scale mu, and one avoids the spurious and meaningless ``theoretical error'' associated with standard alpha_s determinations. PETRA, SLD, and LEP data are considered in the analysis. An attempt is made to estimate the importance of uncalculated next-NLO and higher order perturbative corrections, and power corrections, by studying the scatter in the values of Lambda MS-bar obtained for different observables.Comment: 46 pages, 22 figure

Depressive symptoms and perceived burdens related to being a student: Survey in three European countries

Mikolajczyk RT, Maxwell AE, Naydenova V, Meier S, El Ansari W. Depressive symptoms and perceived burdens related to being a student: survey in three European countries. Clinical Practice and Epidemiology in Mental Health. 2008;4(1): 19.Background: Despite a high prevalence of depressive symptoms among university students, few studies have examined how this mental health problem is associated with perceived stress and perceived burdens related to being a student. Methods: We conducted a cross-sectional study of 2,103 first year students from one western (Germany), one central (Poland), and one south-eastern European country (Bulgaria). The self-administered questionnaires included the modified Beck Depression Inventory and Cohen's Perceived Stress Scale. A 13 item scale measured perceived burdens related to being a student with four subscales: ''Course work'', ''Relationships'', ''Isolation'', and ''Future''. Results: Depressive symptoms were highly prevalent in all three countries (M-BDI &#8805;35: 34% in Poland, 39% in Bulgaria, and 23% in Germany). Students felt more burdened by course work and bad job prospects (''Future'') than by relationship problems or by feelings of isolation. The perceived burdens subscales ''Future'', ''Relationship'' and ''Isolation'' remained associated with depressive symptoms after adjusting for perceived stress, which displayed a strong association with depressive symptoms. The association between perceived stress and depressive symptoms differed by gender. These findings were similar in all three countries. Conclusion: Perceived burdens related to studying are positively associated with higher depression scores among students, not only by mediation through perceived stress but also directly. While the strong association between perceived stress and depressive symptoms suggests the need for interventions that improve stress management, perceived burdens should also be addressed

Opportunities for lattice QCD in quark and lepton flavor physics

This document is one of a series of whitepapers from the USQCD collaboration. Here, we discuss opportunities for lattice QCD in quark and lepton flavor physics. New data generated at Belle II, LHCb, BES III, NA62, KOTO, and Fermilab E989, combined with precise calculations of the relevant hadronic physics, may reveal what lies beyond the Standard Model. We outline a path toward improvements of the precision of existing lattice-QCD calculations and discuss groundbreaking new methods that allow lattice QCD to access new observables.Comment: USQCD whitepape

F17RS SGR No. 3 (Charlottesville)

A RESOLUTION Standing in Solidarity with Charlottesville, Virginia, and the University of Virginia following the Events of August 11-12, 201

Lambda-N scattering length from the reaction gamma d -> K^+ Lambda n

The perspects of utilizing the strangeness-production reaction gamma d -> K^+ Lambda n for the determination of the Lambda n low-energy scattering parameters are investigated. The spin observables that need to be measured in order to isolate the Lambda n singlet (1S0) and triplet (3S1) states are identified. Possible kinematical regions where the extraction of the Lambda n scattering lengths might be feasible are discussed.Comment: 8 pages, 4 figure