979 research outputs found
Strong experimental guarantees in ultrafast quantum random number generation
We describe a methodology and standard of proof for experimental claims of
quantum random number generation (QRNG), analogous to well-established methods
from precision measurement. For appropriately constructed physical
implementations, lower bounds on the quantum contribution to the average
min-entropy can be derived from measurements on the QRNG output. Given these
bounds, randomness extractors allow generation of nearly perfect
"{\epsilon}-random" bit streams. An analysis of experimental uncertainties then
gives experimentally derived confidence levels on the {\epsilon} randomness of
these sequences. We demonstrate the methodology by application to
phase-diffusion QRNG, driven by spontaneous emission as a trusted randomness
source. All other factors, including classical phase noise, amplitude
fluctuations, digitization errors and correlations due to finite detection
bandwidth, are treated with paranoid caution, i.e., assuming the worst possible
behaviors consistent with observations. A data-constrained numerical
optimization of the distribution of untrusted parameters is used to lower bound
the average min-entropy. Under this paranoid analysis, the QRNG remains
efficient, generating at least 2.3 quantum random bits per symbol with 8-bit
digitization and at least 0.83 quantum random bits per symbol with binary
digitization, at a confidence level of 0.99993. The result demonstrates
ultrafast QRNG with strong experimental guarantees.Comment: 11 pages, 9 figure
A holistic approach to enhance the use of neglected and underutilized species: the case of Andean grains in Bolivia and Peru
The IFAD-NUS project, implemented over the course of a decade in two phases, represents the first UN-supported global effort on neglected and underutilized species (NUS). This initiative, deployed and tested a holistic and innovative value chain framework using multi-stakeholder, participatory, inter-disciplinary, pro-poor gender- and nutrition-sensitive approaches. The project has been linking aspects often dealt with separately by R&D, such as genetic diversity, selection, cultivation, harvest, value addition, marketing, and final use, with the goal to contribute to conservation, better incomes, and improved nutrition and strengthened livelihood resilience. The project contributed to the greater conservation of Andean grains and their associated indigenous knowledge, through promoting wider use of their diversity by value chain actors, adoption of best cultivation practices, development of improved varieties, dissemination of high quality seed, and capacity development. Reduced drudgery in harvest and postharvest operations, and increased food safety were achieved through technological innovations. Development of innovative food products and inclusion of Andean grains in school meal programs is projected to have had a positive nutrition outcome for targeted communities. Increased income was recorded for all value chain actors, along with strengthened networking skills and self-reliance in marketing. The holistic approach taken in this study is advocated as an effective strategy to enhance the use of other neglected and underutilized species for conservation and livelihood benefits
Participatory varietal selection of potato using the mother & baby trial design: A gender-responsive trainer’s guide.
This guide aims to provide step-by-step guidance on facilitating and documenting the PVS dynamics using the MBT design to select, and eventually release, potato varieties preferred by end-users that suit male and female farmers ’different needs, diverse agro-systems, and management practices, as well as traders ’and consumers’ preferences
A human homologue of the Drosophila sex determination factor transformer-2 has conserved splicing regulatory functions.
Is the Cepheus E Outflow driven by a Class 0 Protostar?
New early release observations of the Cepheus E outflow and its embedded
source, obtained with the Spitzer Space Telescope, are presented. We show the
driving source is detected in all 4 IRAC bands, which suggests that traditional
Class 0 classification, although essentially correct, needs to accommodate the
new high sensitivity infrared arrays and their ability to detected deeply
embedded sources. The IRAC, MIPS 24 and 70 microns new photometric points are
consistent with a spectral energy distribution dominated by a cold, dense
envelope surrounding the protostar. The Cep E outflow, unlike its more famous
cousin the HH 46/47 outflow, displays a very similar morphology in the near and
mid-infrared wavelengths, and is detected at 24 microns. The interface between
the dense molecular gas (where Cep E lies) and less dense interstellar medium,
is well traced by the emission at 8 and 24 microns, and is one of the most
exotic features of the new IRAC and MIPS images. IRS observations of the North
lobe of the flow confirm that most of the emission is due to the excitation of
pure H2 rotational transitions arising from a relatively cold (Tex~700 K) and
dense (N{H}~9.6E20 cm-2 molecular gas.Comment: 14 pages (pre-print format), including 6 figures. Published in ApJ
Special Spitzer Issue (2004
First Principles Study of Nickel Complex with 1,3-dithiole-2-thione-4,5-dithiolate Ligands as Model Photosensitizers
Dye-sensitized solar cells (DSSCs) have become in one important and promising technology in the photovoltaic field. The ability for a sensitizer to harvest light photons and inject the excited electrons into a photoanode, typically a metal oxide, determines the performance and operation range of the solar cell. Metal complexes with 1,3-dithiole-2-thione-4,5-dithiolate (dmit) ligands, which are an important class of functional materials, have received extensive attention due to their intriguing chemical and physical properties. The electronic and molecular properties of isolated and adsorbed nickel complexes with dmit ligands have been investigated using first principles calculations based on the density functional theory (DFT). Adsorption energies of metal complexes supported on the anatase TiO2(101) surface were calculated for three different configurations, linked by sulphur atom of Sthione, Sthiole-Sthiolate, and planar. The most stable adsorption configurations found in this study are the Sthiole-Sthiolate and the planar forms for the nickel complex. TD-DFT molecular calculations reveal that the lowest energy transition in ultraviolet visible near-infrared (UV-Vis-NIR) mainly corresponds to the HOMO-LUMO π–π* excitation for the nickel complex. The effect of the TiO2(101) surface on the absorption spectra of the nickel complex is practically limited to a red shift of about 0.1-0.3 eV. The analysis of the density of states for the dmit/TiO2(101) system shows that the LUMO of the metal complex lies at the edge of the TiO2 conduction band indicating, therefore, that electron injection from the complex excited state into the semiconductor surface is unlikel
Three Bosons in One Dimension with Short Range Interactions I: Zero Range Potentials
We consider the three-boson problem with -function interactions in
one spatial dimension. Three different approaches are used to calculate the
phase shifts, which we interpret in the context of the effective range
expansion, for the scattering of one free particle a off of a bound pair. We
first follow a procedure outlined by McGuire in order to obtain an analytic
expression for the desired S-matrix element. This result is then compared to a
variational calculation in the adiabatic hyperspherical representation, and to
a numerical solution to the momentum space Faddeev equations. We find excellent
agreement with the exact phase shifts, and comment on some of the important
features in the scattering and bound-state sectors. In particular, we find that
the 1+2 scattering length is divergent, marking the presence of a zero-energy
resonance which appears as a feature when the pair-wise interactions are
short-range. Finally, we consider the introduction of a three-body interaction,
and comment on the cutoff dependence of the coupling.Comment: 9 figures, 2 table
Integral representation of one dimensional three particle scattering for delta function interactions
The Schr\"{o}dinger equation, in hyperspherical coordinates, is solved in
closed form for a system of three particles on a line, interacting via pair
delta functions. This is for the case of equal masses and potential strengths.
The interactions are replaced by appropriate boundary conditions. This leads
then to requiring the solution of a free-particle Schr\"{o}dinger equation
subject to these boundary conditions. A generalized Kontorovich - Lebedev
transformation is used to write this solution as an integral involving a
product of Bessel functions and pseudo-Sturmian functions. The coefficient of
the product is obtained from a three-term recurrence relation, derived from the
boundary condition. The contours of the Kontorovich-Lebedev representation are
fixed by the asymptotic conditions. The scattering matrix is then derived from
the exact solution of the recurrence relation. The wavefunctions that are
obtained are shown to be equivalent to those derived by McGuire. The method can
clearly be applied to a larger number of particles and hopefully might be
useful for unequal masses and potentials.Comment: 18 pages, 2 figures, to be published in J. Math. Phy
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