Fermi edge singularity and finite frequency spectral features in a semi-infinite 1D wire

We theoretically study a charge qubit interacting with electrons in a semi-infinite 1D wire. The system displays the physics of the Fermi edge singularity. Our results generalize known results for the Fermi-edge system to the regime where excitations induced by the qubit can resolve the spatial structure of the scattering region. We find resonant features in the qubit tunneling rate as a function of the qubit level splitting. They occur at integer multiples of h times v_F/l. Here v_F is the Fermi velocity of the electrons in the wire, and l is the distance from the tip of the wire to the point where it interacts with the qubit. These features are due to a single coherent charge fluctuation in the electron gas, with a half-wavelength that fits into l an integer number of times. As the coupling between the qubit and the wire is increased, the resonances are washed out. This is a clear signature of the increasingly violent Fermi-sea shake-up that accompanies strong coupling.Comment: 11 page

Water-Use Efficiency and Infiltration under Different Rangeland Conditions and Cultivation in a Semi-Arid Climate of South Africa

The objective of this study was to determine the impact of rangeland in different botanical composition classes (good, moderate and poor), on water-use efficiency (WUE: crude protein produced per unit of evapotranspiration) and soilwater content. The same measurements were also made on an undisturbed bare soil surface and soil cultivated twice per annum. Evapotranspiration was determined by quantifying the soil-water balance equation with the aid of runoff plots and soil-water content measurements done by a neutron hydroprobe. Water-use efficiency declined significantly (P ≤ 0.01) with rangeland degradation. Rangeland in good condition averaged a WUE of 0.28 kg crude protein ha-1 mm-1. Higher surface runoff occurring in rangeland in poor condition due to less vegetation cover, caused soil-water content to be much lower than that of grassland in good condition. Soil-water storage increased by 31% due to cultivation. The study shows it is important to keep rangeland in optimal condition to utilise limited soil water for sustainable plant and therefore animal production

Philippians 4:10-23 from a rhetorical perspective

This article endeavours to analyse Phil. 4:10-23 from a different perspective to approaches which tend to force ancient rhetorical categories on the letter. On the basis of a text-centred approach, this part of the letter is divided into two sectons, namely 4:10-20 and 21-23. Paul's dominant rhetorical strategy in 4:10-20 could be described as “Strengthening his special relationship with the Philippians by thanking them for their co-operation in the work of the gospel”. In the second section (4:21- 23) Paul instructs the church leaders to greet all God's people in Philippi. In analysing the rhetorical strategies and techniques in 4:10-23, the focus is on the manner in which Paul argues, the type of arguments he uses and the rhetorical techniques that could enhance the impact of his communication. All these strategies and techniques enable Paul to achieve his rhetorical objectives.Acta Theologica Vol. 2 2007: pp. 168-18

Body weight and growth rate of South African Angora goat kids under different pre- and post-weaning management systems

The data used for this study were collected on 16 644 kids born between 2000 and 2004 in 12 different Angora goat studs representing different management systems. Body weight and growth rate of kids from birth to 16 months of age, as well the 18- and 21-month body weights and first kidding performance of ewe kids were evaluated. Variable growth rates were recorded among kids in the different studs, which can be ascribed largely to different environments and supplementary feeding practices. The pre-weaning growth performance of both ram and ewe kids was satisfactory. However, the same did not apply for post-weaning growth rates. In those flocks where kids did not receive any supplementary feeding after weaning, their body weights remained virtually constant from weaning up to eight months of age. This phenomenon where especially ewe kids did not grow well after weaning, needs to be investigated further, since it influences the reproductive ability of young ewes directly. This was evident from the poor reproductive performance of young ewes in some of the studs. On the other hand, the effect of different pre-weaning treatments did not seem to be carried over to body weight and reproductive performance at first kidding age. South African Journal of Animal Science Vol. 37 (2) 2007: pp. 132-14

Influence of Water Stress on Root/Cladode Ratio and Water-Use Efficiency of Opuntia \u3cem\u3eFicus-Indica\u3c/em\u3e and \u3cem\u3eO. Robusta\u3c/em\u3e

Due to the regular occurrence of drought in southern Africa, there is a need for more research on drought tolerant fodder plants such as Opuntia (cactus pear) species. In contrast with the cladode system, the roots of cactus pear have received little attention, however, they certainly differ from other plants, as they develop xeromorphic characteristics, enabling the plant to survive prolonged periods of drought (Nobel, 1988). The influence of different water applications was evaluated in terms of root and cladode mass, water-use efficiency (WUE) and root length for one-year-old plants of Opuntia ficus-indica (cultivar Morado) and O. robusta (cultivar Monterey)

Valley-isospin dependence of the quantum Hall effect in a graphene p-n junction

We calculate the conductance G of a bipolar junction in a graphene nanoribbon, in the high-magnetic field regime where the Hall conductance in the p-doped and n-doped regions is 2e^2/h. In the absence of intervalley scattering, the result G=(e^2/h)(1-cos Phi) depends only on the angle Phi between the valley isospins (= Bloch vectors representing the spinor of the valley polarization) at the two opposite edges. This plateau in the conductance versus Fermi energy is insensitive to electrostatic disorder, while it is destabilized by the dispersionless edge state which may exist at a zigzag boundary. A strain-induced vector potential shifts the conductance plateau up or down by rotating the valley isospin.Comment: 5 pages, 6 figure

Defoliation Impact on the Above and Belowground Productivity of \u3cem\u3eFestuca arundinaceae\u3c/em\u3e Schreb

The main objective of pasture management is to maximize plant productivity and ensure sustainable animal performance, without inducing pasture deterioration. Many researchers indicated that plant survival and sustainable production is a function of seedbed preparation, irrigation and defoliation, with defoliation having the largest impact on plant persistence (Fulkerson and Donaghy, 2001). The net effect of defoliation (degree of intensity and frequency) can therefore either be beneficial or detrimental to survival and productivity of a pasture. The aim of this study was to quantify the impact of different intensities and frequencies of defoliation on above- and belowground phytomass production of the cultivated pasture Festuca arundinaceae Schreb. under irrigation

Polarons in suspended carbon nanotubes

We prove theoretically the possibility of electric-field controlled polaron formation involving flexural (bending) modes in suspended carbon nanotubes. Upon increasing the field, the ground state of the system with a single extra electron undergoes a first order phase transition between an extended state and a localized polaron state. For a common experimental setup, the threshold electric field is only of order $\simeq 10^{-2}$ V/$\mu$m