130 research outputs found
Aquaculture in Zambia: An overview and evaluation of the sector’s responsiveness to the needs of the poor
Given the recent expansion and commercialization of aquaculture in Zambia, an important question that needs to be explored is how have the recent changes in the Zambian aquaculture sector contributed to the needs of the poor? The aim of this report is to (a) outline the current trajectory of aquaculture development in Zambia and (b) evaluate whether these development efforts are inclusive of and responsive to the needs of the poor
Statistics of Wave Functions in Coupled Chaotic Systems
Using the supersymmetry technique, we calculate the joint distribution of
local densities of electron wavefunctions in two coupled disordered or chaotic
quantum billiards. We find novel spatial correlations that are absent in a
single chaotic system. Our exact result can be interpreted for small coupling
in terms of the hybridization of eigenstates of the isolated billiards. We show
that the presented picture is universal, independent of microscopic details of
the coupling.Comment: 4 pages, 2 figures; acknowledgements and references adde
pi^0 pi^0 Scattering Amplitudes and Phase Shifts Obtained by the pi^- P Charge Exchange Process
The results of the analysis of the pi^0 pi^0 scattering amplitudes obtained
with pi^- P charge exchange reaction, pi^- P --> pi^0 pi^0 n, data at 9 GeV/c
are presented. The pi^0 pi^0 scattering amplitudes show clear f_0(1370) and
f_2(1270) signals in the S and D waves, respectively. The pi^0 pi^0 scattering
phase shifts have been obtained below Kbar K threshold and been analyzed by the
Interfering Amplitude method with introduction of negative background phases.
The results show a S wave resonance, sigma. Its Breit-Wigner parameters are in
good agreement with those of our previous analysis on the pi^+ pi^- phase shift
data.Comment: 4 pages, 4 figures. Proceedings of the int. conf. Hadron'99 at
Beijing, Aug. 1999. Presented for the collaboration of A.M.Ma, K.Takamatsu,
M.Y.Ishida, S.Ishida, T.Ishida, T. Tsuru and H. Shimizu, and the E135
collaboration. For our activities on sigma, visit
http://amaterasu.kek.jp/sigm
Statistics of Coulomb blockade peak spacings for a partially open dot
We show that randomness of the electron wave functions in a quantum dot
contributes to the fluctuations of the positions of the conductance peaks. This
contribution grows with the conductance of the junctions connecting the dot to
the leads. It becomes comparable with the fluctuations coming from the
randomness of the single particle spectrum in the dot while the Coulomb
blockade peaks are still well-defined. In addition, the fluctuations of the
peak spacings are correlated with the fluctuations of the conductance peak
heights.Comment: 13 pages, 1 figur
A surface containing a line and a circle through each point is a quadric
We prove that a surface in real 3-space containing a line and a circle
through each point is a quadric. We also give some particular results on the
classification of surfaces containing several circles through each point.Comment: Improved exposition, 4 figures adde
Low temperature transport in AC-driven Quantum Dots in the Kondo regime
We present a fully nonequilibrium calculation of the low temperature
transport properties of a quantum dot in the Kondo regime when an AC potential
is applied to the gate voltage. We solve a time dependent Anderson model with
finite on-site Coulomb interaction. The interaction self-energy is calculated
up to second order in perturbation theory in the on-site interaction, in the
context of the Keldysh non-equilibrium technique, and the effect of the AC
voltage is taken into account exactly for all ranges of AC frequencies and AC
intensities. The obtained linear conductance and time-averaged density of
states of the quantum dot evolve in a non trivial way as a function of the AC
frequency and AC intensity of the harmonic modulation.Comment: 30 pages,7 figure
Kondo effect induced by a magnetic field
We study peculiarities of transport through a Coulomb blockade system tuned
to the vicinity of the spin transition in its ground state. Such transitions
can be induced in practice by application of a magnetic field. Tunneling of
electrons between the dot and leads mixes the states belonging to the ground
state manifold of the dot. Remarkably, both the orbital and spin degrees of
freedom of the electrons are engaged in the mixing at the singlet-triplet
transition point. We present a model which provides an adequate theoretical
description of recent experiments with semiconductor quantum dots and carbon
nanotubes
Anomalous behavior of spin wave resonances in Ga_{1-x}Mn_{x}As thin films
We report ferromagnetic and spin wave resonance absorption measurements on
high quality epitaxially grown Ga_{1-x}Mn_{x}As thin films. We find that these
films exhibit robust ferromagnetic long-range order, based on the fact that up
to seven resonances are detected at low temperatures, and the resonance
structure survives to temperatures close to the ferromagnetic transition. On
the other hand, we observe a spin wave dispersion which is linear in mode
number, in qualitative contrast with the quadratic dispersion expected for
homogeneous samples. We perform a detailed numerical analysis of the
experimental data and provide analytical calculations to demonstrate that such
a linear dispersion is incompatible with uniform magnetic parameters. Our
theoretical analysis of the ferromagnetic resonance data, combined with the
knowledge that strain-induced anisotropy is definitely present in these films,
suggests that a spatially dependent magnetic anisotropy is the most likely
reason behind the anomalous behavior observed.Comment: 9 pages, including 6 figure
A review of inclusive business models and their application in aquaculture development
Open Access Journal; Published online: 30 Jan 2020For aquaculture to continue along its current growth trajectory and contribute towards achieving the Sustainable Development Goals, value chains must become more inclusive. Smallholders and other local value chain actors are often constrained by circumstances and market failures in the global aquaculture industry. Integrating these actors into aquaculture value chains through inclusive business models (IBMs) is often touted as a solution to sustainable and ethical trade and business that can generate development outcomes. We reviewed 36 papers under seven business models commonly used in agriculture development to assess their application in aquaculture value chains in lower‐income countries. A global value chain (GVC) analysis is used to unpack the economic and social upgrading objectives of the different IBMs, as well as the types of relational coordination used between actors in the chain to achieve development outcomes. The extent to which these IBMs helped poor actors overcome certain barriers is evaluated with a focus on how they may ensure or be a risk to inclusiveness through the relations and upgrading opportunities evident in their make‐up. The analysis found that the majority of the models focused on economic upgrading over social upgrading. Providing opportunities for the latter is key to achieving the inclusive objectives of IBMs. Greater horizontal coordination between actors can create further opportunities for economic upgrading established under vertical coordination with other nodes upstream and downstream in a value chain. There is a need to further contextualize these models to aquaculture systems and develop clear indicators of inclusiveness
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