10,505 research outputs found
Interband polarized absorption in InP polytypic superlattices
Recent advances in growth techniques have allowed the fabrication of
semiconductor nanostructures with mixed wurtzite/zinc-blende crystal phases.
Although the optical characterization of these polytypic structures is well
eported in the literature, a deeper theoretical understanding of how crystal
phase mixing and quantum confinement change the output linear light
polarization is still needed. In this paper, we theoretically investigate the
mixing effects of wurtzite and zinc-blende phases on the interband absorption
and in the degree of light polarization of an InP polytypic superlattice. We
use a single 88 kp Hamiltonian that describes both crystal
phases. Quantum confinement is investigated by changing the size of the
polytypic unit cell. We also include the optical confinement effect due to the
dielectric mismatch between the superlattice and the vaccum and we show it to
be necessary to match experimental results. Our calculations for large wurtzite
concentrations and small quantum confinement explain the optical trends of
recent photoluminescence excitation measurements. Furthermore, we find a high
sensitivity to zinc-blende concentrations in the degree of linear polarization.
This sensitivity can be reduced by increasing quantum confinement. In
conclusion, our theoretical analysis provides an explanation for optical trends
in InP polytypic superlattices, and shows that the interplay of crystal phase
mixing and quantum confinement is an area worth exploring for light
polarization engineering.Comment: 9 pages, 6 figures and 1 tabl
Phenomenological Analysis of and Elastic Scattering Data in the Impact Parameter Space
We use an almost model-independent analytical parameterization for and
elastic scattering data to analyze the eikonal, profile, and
inelastic overlap functions in the impact parameter space. Error propagation in
the fit parameters allows estimations of uncertainty regions, improving the
geometrical description of the hadron-hadron interaction. Several predictions
are shown and, in particular, the prediction for inelastic overlap
function at TeV shows the saturation of the Froissart-Martin
bound at LHC energies.Comment: 15 pages, 16 figure
Stabilization of Extra Dimensions and The Dimensionality of the Observed Space
We present a simple model for the late time stabilization of extra
dimensions. The basic idea is that brane solutions wrapped around extra
dimensions, which is allowed by string theory, will resist expansion due to
their winding mode. The momentum modes in principle work in the opposite way.
It is this interplay that leads to dynamical stabilization. We use the idea of
democratic wrapping \cite{art5}-\cite{art6}, where in a given decimation of
extra dimensions, all possible winding cases are considered. To simplify the
study further we assumed a symmetric decimation in which the total number of
extra dimensions is taken to be where N can be called the order of the
decimation. We also assumed that extra dimensions all have the topology of
tori. We show that with these rather conservative assumptions, there exists
solutions to the field equations in which the extra dimensions are stabilized
and that the conditions do not depend on . This fact means that there exists
at least one solution to the asymmetric decimation case. If we denote the
number of observed space dimensions (excluding time) by , the condition for
stabilization is for pure Einstein gravity and for dilaton
gravity massaged by string theory parameters.Comment: Final versio
Algae bioaccumulation capacity for metals in acid mine drainage (AMD)-a case study in Frongoch Mine, the UK
Algae living in the AMD water around the Frongoch Mine, the UK, were collected
and identified by microscope. Metals’ concentration was evaluated in AMD water
and algae in two seasons (June and October) in 2019 to assess the bioaccumulation
capacity of algae. Two types of algae, Ulothrix sp. and Oedogonium sp., were found to
be the main species at the Frongoch mine, and they revealed a high capacity of metals
bioaccumulation. Concentrations of metals in AMD water from higher to lower were
Zn>>Pb>Cd>Fe>Cu. Study results identified the bioaccumulated metals concentrations
in algae from higher to lower were Fe>Pb>Cu>Cd>Zn
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