Sleeper end resistance of ballasted railway tracks

This paper describes model tests used to investigate how ballast shoulder width and height contribute to a railway sleeper’s resistance to lateral movement for a range of shoulder widths and heights. Deflection and resistance were measured and photographs taken during the tests.The photographs were analyzed using a digital image correlation technique to identify the zones of ballast surface disturbance, which demonstrated that a bulbed failure volume was mobilized at the ultimate limit state. An idealized three-dimensional failure mechanism is proposed, and resistances are calculated using the limit equilibrium approach. The calculation provides a reliable estimate of the measured resistance. The work identifies the optimum shoulder width and height. The calculations are extended to demonstrate that when a number of sleepers are moved simultaneously, the sleeper end resistance may be one-third less per sleeper than that indicated in tests on an isolated sleeper. Image analysis and limit equilibrium calculations show that this is caused by overlapping of mobilized failure volumes from adjacent sleepers

Lattice polarization effects on the screened Coulomb interaction WW of the GW approximation

In polar insulators where longitudinal and transverse optical phonon modes differ substantially, the electron-phonon coupling affects the energy-band structure primarily through the long-range Fr\"ohlich contribution to the Fan term. This diagram has the same structure as the $GW$ self-energy where $W$ originates from the electron part of the screened coulomb interaction. The two can be conveniently combined by combining electron and lattice contributions to the polarizability. Both contributions are nonanalytic at the origin, and diverge as $1/q^2$ so that the predominant contribution comes from a small region around $q{=}0$. Here we adopt a simple estimate for the Fr\"ohlich contribution by assuming that the entire phonon part can be attributed to a small volume of $q$ near $q{=}0$. We estimate the magnitude for $\mathbf{q}{\rightarrow}0$ from a generalized Lyddane-Sachs-Teller relation, and the radius from the inverse of the polaron length scale. The gap correction is shown to agree with Fr\"ohlich's simple estimate $-\alpha_P\omega_L/2$ of the polaron effect

Characterizing the Variability of Physical and Chemical Properties across the Soil Individuals Mapped as Amy Silt Loam Soils in Southeastern Arkansas

Knowledge of physical and chemical properties of soil is relevant for landowners, researchers, and foresters, so that appropriate crop species and management practices to maximize site productivity can be selected. In addition to issues of plant productivity, the need for assessing soil properties has been expanded due to public interest in determining the consequences of management practices on soil quality relative to sustainability of crop ecosystem functions. The USDA-Natural Resources Conservation Service (NRCS) delineated soil mapping units to provide information about physical and chemical properties of soil in each soil series. However, soil mapping units do not provide details about the variability of soil properties within a single soil series. To determine the variability of physical and chemical properties within Amy soil series, 200 soil samples were collected to a depth of 0–15cm and 15–30cm from soil individuals mapped as the Amy silt loam soils in five different locations in southeastern Arkansas. Comparisons of soil texture, bulk density, carbon, nitrogen, Mehlich III extractable macronutrients, and micronutrients revealed significant differences among soil individuals/ locations for both depth increments. Additionally, all nutrients except potassium, magnesium, and copper differed between the two soil depths. The results suggest inherent variation in biogeochemical and geochemical cycling in the surface horizons of soils mapped as the Amy series

Relation between geometric phases of entangled bi-partite systems and their subsystems

This paper focuses on the geometric phase of entangled states of bi-partite systems under bi-local unitary evolution. We investigate the relation between the geometric phase of the system and those of the subsystems. It is shown that (1) the geometric phase of cyclic entangled states with non-degenerate eigenvalues can always be decomposed into a sum of weighted non-modular pure state phases pertaining to the separable components of the Schmidt decomposition, though the same cannot be said in the non-cyclic case, and (2) the geometric phase of the mixed state of one subsystem is generally different from that of the entangled state even by keeping the other subsystem fixed, but the two phases are the same when the evolution operator satisfies conditions where each component in the Schmidt decomposition is parallel transported

In vitro Appraisal of Interactions between Spot Blotch Pathogen B. sorokiniana and Selected Parasitic Fungi of Wheat Leaves

Pathogenic micro-organisms living on wheat foliages may interact with each others. This study was conducted to reveal the interactive relationships existing between spot blotch causing fungus Bipolaris sorokiniana and selected pathogenic fungi subsisting on wheat foliages. Four fungal pathogens of wheat were selected, and the intensity and severity of the selected pathogenic fungi on wheat leaves were assessed. Pure cultures of the fungi were produced by isolating them from the spot blotch infected and blighted wheat leaves. Separate in vitro dual culture studies in completely randomized design with five replications were carried out to assess the interactions between each pair of B. sorokiniana and selected rival pathogens of wheat foliages. Percent inhibition in radial growth of either fungus was calculated. Viability test of the mycelium at the interface zone and pathogenicity test of the isolates were carried out. B. sorokiniana strongly inhibited the colony growth of Cercospora sp. and Phoma sp. under in vitro conditions. Similarly, there was not any effect on colony growth of either B. sorokiniana or Bipolaris sp. due to dual culture with each other. The dual culture of B. sorokiniana and Alternaria triticina results in the suppression of colony growth of both fungi. There were non-significant differences in percent growth inhibition between the first and the second week of dual culture in some of the tested fungi.  The viability of mycelia of all the tested fungi was intact in dual culture. B. sorokiniana exerts antagonistic ability against some minor pathogens of wheat foliages under in-vitro conditions.Â

Reply to `Singularities of the mixed state phase'

The only difference between Bhandari's viewpoint [quant-ph/0108058] and ours [Phys. Rev. Lett. 85, 2845 (2000)] is that our phase is defined modulo $2\pi$, whereas Bhandari argues that two phases that differ by $2\pi n$, $n$ integer, may be distinguished experimentally in a history-dependent manner.Comment: 2 page

Nuclear reactor power as applied to a space-based radar mission

The SP-100 Project was established to develop and demonstrate feasibility of a space reactor power system (SRPS) at power levels of 10's of kilowatts to a megawatt. To help determine systems requirements for the SRPS, a mission and spacecraft were examined which utilize this power system for a space-based radar to observe moving objects. Aspects of the mission and spacecraft bearing on the power system were the primary objectives of this study; performance of the radar itself was not within the scope. The study was carried out by the Systems Design Audit Team of the SP-100 Project