New Light Species and the CMB

We consider the effects of new light species on the Cosmic Microwave Background. In the massless limit, these effects can be parameterized in terms of a single number, the relativistic degrees of freedom. We perform a thorough survey of natural, minimal models containing new light species and numerically calculate the precise contribution of each of these models to this number in the framework of effective field theory. After reviewing the relevant details of early universe thermodynamics, we provide a map between the parameters of any particular theory and the predicted effective number of degrees of freedom. We then use this map to interpret the recent results from the Cosmic Microwave Background survey done by the Planck satellite. Using this data, we present new constraints on the parameter space of several models containing new light species. Future measurements of the Cosmic Microwave Background can be used with this map to further constrain the parameter space of all such models.Comment: 38 pages plus appendices and references; 10 figures and 1 table; references added, discussion of anapole moments added; supernovae cooling bounds added, discussion of models condense

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

Light trapping in ultrathin plasmonic solar cells

We report on the design, fabrication, and measurement of ultrathin film a-Si:H solar cells with nanostructured plasmonic back contacts, which demonstrate enhanced short circuit current densities compared to cells having flat or randomly textured back contacts. The primary photocurrent enhancement occurs in the spectral range from 550 nm to 800 nm. We use angle-resolved photocurrent spectroscopy to confirm that the enhanced absorption is due to coupling to guided modes supported by the cell. Full-field electromagnetic simulation of the absorption in the active a-Si:H layer agrees well with the experimental results. Furthermore, the nanopatterns were fabricated via an inexpensive, scalable, and precise nanopatterning method. These results should guide design of optimized, non-random nanostructured back reflectors for thin film solar cells

Numerical simulation of transom-stern waves

The flow field generated by a transom-stern hullform is a complex, broad-banded, three-dimensional phenomenon marked by a large breaking wave. This unsteady multiphase turbulent flow feature is difficult to study experimentally and simulate numerically. The results of a set of numerical simulations, which use the Numerical Flow Analysis (NFA) code, of the flow around the Model 5673 transom stern at speeds covering both wet- and dry-transom operating conditions are shown in the accompanying fluid dynamics video. The numerical predictions for wet-transom and dry-transom conditions are presented to demonstrate the current state of the art in the simulation of ship generated breaking waves. The interested reader is referred to Drazen et al. (2010) for a detailed and comprehensive comparison with experiments conducted at the Naval Surface Warfare Center Carderock Division (NSWCCD).Comment: Fluid Dynamics Video for 2010 APS Division of Fluid Dynamics Gallery of Fluid Motion include

Prediction of equilibrium isotopic fractionation of the gypsum/bassanite/water system using first-principles calculations

The stable isotopes (18O/16O, 17O/16O and 2H/1H) of structurally-bound water (also called hydration water) in gypsum (CaSO4•2H2O) and bassanite (CaSO4•0.5H2O) can be used to reconstruct the isotopic composition of paleo-waters. Understanding the variability of the isotope fractionation factors between the solution and the solid α17Omineral-water, α18Omineral-water and αDmineral-water) is crucial for applying this proxy to paleoclimatic research. Here we predict the theoretical equilibrium fractionation factors for triple oxygen and hydrogen isotopes in the gypsum-water and bassanite-water systems between 0 ⁰C and 60 ⁰C. We apply first-principles using density functional theory within the harmonic approximation. Our theoretical results for α18Ogypsum-water (1.00347±0.00037) are in agreement with previous experimental studies, whereas Dgypsum-water agrees only at temperatures above 25 ⁰C. At lower temperatures, the experimental values of αDgypsumwater are consistently higher than theoretical values (e.g. 0.9749 and 0.9782, respectively, at 3 ⁰C), which can be explained by kinetic effects that affect gypsum precipitation under laboratory conditions at low temperature. We predict that α18Obassanite-water is similar to α18Ogypsum-water in the temperature range of 0 ⁰C to 60 ⁰C. Both α18Ogypsum-water and α18Obassanite-water show a small temperature dependence of ~0.0000122 per ⁰C, which is negligible for most paleoclimate studies. The theoretical relationship between α17Ogypsumwater and α18Ogypsum-water from 0 °C to 60 °C is 0.5274±0.00063. The relationship is very insensitive to temperature (0.00002 per ⁰C). The fact that α18O values of gypsum hydration water are greater than free water (α18Ogypsum-water >1) whereas αD values of gypsum hydration water are less than free water (αDgypsum-water <1) is explained by phonon theory. We conclude that calculations from first-principles using density functional theory within the harmonic approximation can accurately predict fractionation factors between structurally-bound water of minerals and free water.ER

Black Hole Entropy, Topological Entropy and the Baum-Connes Conjecture in K-Theory

We shall try to exhibit a relation between black hole entropy and topological entropy using the famous Baum-Connes conjecture for foliated manifolds which are particular examples of noncommutative spaces. Our argument is qualitative and it is based on the microscopic origin of the Beckenstein-Hawking area-entropy formula for black holes, provided by superstring theory, in the more general noncommutative geometric context of M-Theory following the Connes- Douglas-Schwarz article.Comment: 17 pages, Latex, contains an important paragraph in section 2 which gives a better understandin

Greenland turbot Reinhardtius hippoglossoides of the eastern Bering Sea and Aleutian Islands region

Greenland turbot (Reinhardtius hippoglossoides) is a commercially important flounder in both the North Atlantic and North Pacific Oceans. In the latter, its center of abundance is in the eastern Bering Sea and along the Aleutian Islands chain where its population is managed as a single stock. Harvest levels in this region of the North Pacific during the period 1970-81 were comparable with those in the northwest and northeast Atlantic, with annual average catches of 53,000 metric tons (t). However, the catch in 1984 dropped sharply to 23,100 t, in part because of reduced quotas arising from concern over continued poor recruitment and declining catch-per-unit-effort. Recruitment failure was manifested in 1) the sharp decline in the catch rate of young flsh in annual research trawl surveys on the continental shelf of the eastern Bering Sea and 2) an increasing proportion of older and larger fish in the commercial catch from the continental slope of both the eastern Bering Sea and Aleutian Islands. The cause ofthe decline in recruitment could not be clearly identifled. Greenland turbot of the Bering Sea-Aleutian Islands share certain distributional features with the North Atlantic form. There is an apparent bathymetric change in the size and age of fish, with younger animals occupying continental shelf depths and the older individuals residing at depths of the continental slope. At shallow depths the young are exposed to temperature fluctuations, whereas older animals along the slope are exposed to relatively stable temperatures. A hypothesis is proposed for describing the temporal and spatial paths by which young animals reach the mature or spawning portion of the population. (PDF file contains 38 pages.

Impact of Manure Application on Phosphorus in Surface Runoff and Soil Erosion

Effects of method of manure management and dietary P were compared on 21 natural runoff plots to monitor the long-term impact of dietary P to P losses in runoff and erosion. Reducing feed P resulted in a 33% reduction in manure P content and soil test P buildup and runoff losses of P also were directly proportional to feed P inputs. The timing and management of manure are also important considerations for controlling P losses in runoff in the year of application. However, residual effects of timing and management are probably small. Management criteria designed to assess the potential for landscape P-loading (i.e. “P-index”) correctly weight winter applications as more detrimental than planting time applications

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