393 research outputs found
Collective Excitations Spectrum in Density Modulated One-Dimensional Electron Gas in a Magnetic Field
We determine the collective excitations spectrum and discuss the numerical
results for a parabolically confined density modulated quasi-one dimensional
electron gas (1DEG) in the presence of an external magnetic field. We derive
the inter-and intra-band magnetoplasmon spectrum within the Self Consistent
Field (SCF) approach. In this work we focus on magnetoplasmon oscillations in
this system and as such results are presented for the intra-Landau-band
magnetoplasmon spectrum that exhibits oscillatory behavior, these oscillations
are not with constant period in 1/B and are significantly effected at low B and
corresponding high 1/B.Comment: 10 pages, 2 figure
ETHNO-VETERINARY PRACTICES AMONGST LIVESTOCK FARMERS IN NGAMILAND DISTRICT, BOTSWANA
We carried out a study to determine ethno-veterinary knowledge used to treat and prevent livestock diseases in Toteng Village in Ngamiland District, northwestern Botswana. Primary data were collected through simple random sampling of 45 households in Toteng. Respondents were either livestock owners or cattle herders. Respondents were interviewed using a structured questionnaire which had both open and closed-ended questions. Cattle ownership or herdership in Toteng is an inter-generational occupation with people ranging from 15 to 94 years old. Cattle were acquired either through inheritance, buying, mafisa (reciprocal exchange) system or government scheme. Women in the study area were more involved in livestock farming activities. Eleven livestock diseases were reported to be prevalent in the study area. The top six diseases were tlhako le molomo -foot and mouth disease (FMD), matlho - eye infections, letshololo-diarrhea, madi -pasteurollosis, mokokomalo - aphosphorisis and pholoso- contagious abortion. At least nine medicinal plant species having ethno-veterinary applications were recorded in the study area. Single plants are mostly used rather than a combination of plants. A number of social strategies were mentioned such as ‘go fetola mafudiso’ - to change grazing areas, and ‘go thaa lesaka’ – to ritualistically ‘protect a kraal’ or livestock against evil spells and predators (lions). Although the intervention of conventional veterinary medicine is pervasive in Toteng, and many livestock owners are resorting to it, there is evidence, however, of generalized ethno-veterinary knowledge used to treat and prevent livestock diseases. Local farmers and their herders in Ngamiland are not only knowledgeable and experienced in treating a range of livestock diseases, but also in performing other veterinary tasks such as assisting in births, treating fractures and range management strategies to mitigate particular threats from their local environment. The efficacy of ethno-veterinary knowledge for preventing and treating livestock diseases and range management strategies identified in this study need to be fully investigated and integrated in veterinary extension services
Inelastic Coulomb scattering rates due to acoustic and optical plasmon modes in coupled quantum wires
We report a theoretical study on the inelastic Coulomb scattering rate of an
injected electron in two coupled quantum wires in quasi-one-dimensional doped
semiconductors. Two peaks appear in the scattering spectrum due to the optical
and the acoustic plasmon scattering in the system. We find that the scattering
rate due to the optical plasmon mode is similar to that in a single wire but
the acoustic plasmon scattering depends crucially on its dispersion relation at
small . Furthermore, the effects of tunneling between the two wires are
studied on the inelastic Coulomb scattering rate. We show that a weak tunneling
can strongly affect the acoustic plasmon scattering.Comment: 6 Postscript figure
Electronic structure of rectangular quantum dots
We study the ground state properties of rectangular quantum dots by using the
spin-density-functional theory and quantum Monte Carlo methods. The dot
geometry is determined by an infinite hard-wall potential to enable comparison
to manufactured, rectangular-shaped quantum dots. We show that the electronic
structure is very sensitive to the deformation, and at realistic sizes the
non-interacting picture determines the general behavior. However, close to the
degenerate points where Hund's rule applies, we find spin-density-wave-like
solutions bracketing the partially polarized states. In the
quasi-one-dimensional limit we find permanent charge-density waves, and at a
sufficiently large deformation or low density, there are strongly localized
stable states with a broken spin-symmetry.Comment: 8 pages, 9 figures, submitted to PR
Far-infrared edge modes in quantum dots
We have investigated edge modes of different multipolarity sustained by
quantum dots submitted to external magnetic fields. We present a microscopic
description based on a variational solution of the equation of motion for any
axially symmetric confining potential and multipole mode. Numerical results for
dots with different number of electrons whose ground-state is described within
a local Current Density Functional Theory are discussed. Two sum rules, which
are exact within this theory, are derived. In the limit of a large neutral dot
at B=0, we have shown that the classical hydrodynamic dispersion law for edge
waves \omega(q) \sim \sqrt{q \ln (q_0/q)} holds when quantum and finite size
effects are taken into account.Comment: We have changed some figures as well as a part of the tex
Far-infrared edge modes in quantum dots
We have investigated edge modes of different multipolarity sustained by
quantum dots submitted to external magnetic fields. We present a microscopic
description based on a variational solution of the equation of motion for any
axially symmetric confining potential and multipole mode. Numerical results for
dots with different number of electrons whose ground-state is described within
a local Current Density Functional Theory are discussed. Two sum rules, which
are exact within this theory, are derived. In the limit of a large neutral dot
at B=0, we have shown that the classical hydrodynamic dispersion law for edge
waves \omega(q) \sim \sqrt{q \ln (q_0/q)} holds when quantum and finite size
effects are taken into account.Comment: We have changed some figures as well as a part of the tex
Plasmon Modes and Correlation Functions in Quantum Wires and Hall Bars
We present microscopic derivations of the one-dimensional low-energy boson
effective Hamiltonians of quantum wire and quantum Hall bar systems. The
quantum Hall system is distinguished by its spatial separation of oppositely
directed electrons. We discuss qualitative differences in the plasmon
collective mode dispersions and the ground state correlation functions of the
two systems which are consequences of this difference. The slowly-decaying
quasi-solid correlations expected in a quantum wire are strongly suppressed in
quantum Hall bar systems.Comment: 7 pages, RevTex, 3 figures and 1 table included; references updated
and minor typos correcte
BEYOND ACTIVATION REFORMING EUROPEAN UNEMPLOYMENT PROTECTION SYSTEMS IN POST-INDUSTRIAL LABOUR MARKETS
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