9,577 research outputs found
Beyond recurrent costs: an institutional analysis of the unsustainability of donor-supported reforms in agricultural extension
International donors have spent billions of dollars over the past four decades in developing and/or reforming the agricultural extension service delivery arrangements in developing countries. However, many of these reforms, supported through short-term projects, became unsustainable once aid funding had ceased. The unavailability of recurrent funding has predominantly been highlighted in the literature as the key reason for this undesirable outcome, while little has been written about institutional factors. The purpose of this article is to examine the usefulness of taking an institutional perspective in explaining the unsustainability of donor-supported extension reforms and derive lessons for improvement. Using a framework drawn from the school of institutionalism in a Bangladeshi case study, we have found that a reform becomes unsustainable because of poor demands for extension information and advice; missing, weak, incongruent, and perverse institutional frameworks governing the exchange of extension goods (services); and a lack of institutional learning and change during the reform process. Accordingly, we have argued that strategies for sustainable extension reforms should move beyond financial considerations and include such measures as making extension goods (services) more tangible and monetary in nature, commissioning in-depth studies to learn about local institutions, crafting new institutions and/or reforming the weak and perverse institutions prevailing in developing countries. We emphasize the need to address three categories of institutions – regulative, normative, and cultural-cognitive – and call for an alignment among them. We further argue that, in order to be sustainable, a reform should take a systemic approach in institutional capacity building and, for this to be possible, adopt a long-term program approach, as opposed to a short-term project approach
Magnetotransport properties of a magnetically modulated two-dimensional electron gas with the spin-orbit interaction
We study the electrical transport properties of a two-dimensional electron
gas with the Rashba spin-orbit interaction in presence of a constant
perpendicular magnetic field which is weakly modulated by , where and with
is the modulation period. We obtain the analytical expressions of the diffusive
conductivities for spin-up and spin-down electrons. The conductivities for
spin-up and spin-down electrons oscillate with different frequencies and
produce beating patterns in the amplitude of the Weiss and Shubnikov-de Haas
oscillations. We show that the Rashba strength can be determined by analyzing
the beating pattern in the Weiss oscillation. We find a simple equation which
determines the Rashba spin-orbit interaction strength if the number of Weiss
oscillations between any two successive nodes is known from the experiment. We
compare our results with the electrically modulated 2DEG with the Rashba
interaction. For completeness, we also study the beating pattern formation in
the collisional and the Hall conductivities.Comment: 11 pages, 5 figures, re-written with new result
Ga+, In+ and Tl+ Impurities in Alkali Halide Crystals: Distortion Trends
A computational study of the doping of alkali halide crystals (AX: A = Na, K;
X = Cl, Br) by ns2 cations (Ga+, In+ and Tl+) is presented. Active clusters of
increasing size (from 33 to 177 ions) are considered in order to deal with the
large scale distortions induced by the substitutional impurities. Those
clusters are embedded in accurate quantum environments representing the
surrounding crystalline lattice. The convergence of the distortion results with
the size of the active cluster is analyced for some selected impurity systems.
The most important conclusion from this study is that distortions along the
(100) and (110) crystallographic directions are not independent. Once a
reliable cluster model is found, distortion trends as a function of impurity,
alkali cation and halide anion are identified and discussed. These trends may
be useful when analycing other cation impurities in similar host lattices.Comment: LaTeX file. 7 pages and 2 pictures. Accepted for publication in J.
Chem. Phy
Electronic Devices Based on Purified Carbon Nanotubes Grown By High Pressure Decomposition of Carbon Monoxide
The excellent properties of transistors, wires, and sensors made from
single-walled carbon nanotubes (SWNTs) make them promising candidates for use
in advanced nanoelectronic systems. Gas-phase growth procedures such as the
high pressure decomposition of carbon monoxide (HiPCO) method yield large
quantities of small diameter semiconducting SWNTs, which are ideal for use in
nanoelectronic circuits. As-grown HiPCO material, however, commonly contains a
large fraction of carbonaceous impurities that degrade properties of SWNT
devices. Here we demonstrate a purification, deposition, and fabrication
process that yields devices consisting of metallic and semiconducting nanotubes
with electronic characteristics vastly superior to those of circuits made from
raw HiPCO. Source-drain current measurements on the circuits as a function of
temperature and backgate voltage are used to quantify the energy gap of
semiconducting nanotubes in a field effect transistor geometry. This work
demonstrates significant progress towards the goal of producing complex
integrated circuits from bulk-grown SWNT material.Comment: 6 pages, 4 figures, to appear in Nature Material
Asymmetric Thermal Lineshape Broadening in a Gapped 3-Dimensional Antiferromagnet - Evidence for Strong Correlations at Finite Temperature
It is widely believed that magnetic excitations become increasingly
incoherent as temperature is raised due to random collisions which limit their
lifetime. This picture is based on spin-wave calculations for gapless magnets
in 2 and 3 dimensions and is observed experimentally as a symmetric Lorentzian
broadening in energy. Here, we investigate a three-dimensional dimer
antiferromagnet and find unexpectedly that the broadening is asymmetric -
indicating that far from thermal decoherence, the excitations behave
collectively like a strongly correlated gas. This result suggests that a
temperature activated coherent state of quasi-particles is not confined to
special cases like the highly dimerized spin-1/2 chain but is found generally
in dimerized antiferromagnets of all dimensionalities and perhaps gapped
magnets in general
On asymmetry in inclusive pion production
On the basis of the mechanism proposed for one-spin asymmetries in inclusive
hadron production we specify an --dependence of asymmetries in inclusive
processes of pion production. The main role in generation of this asymmetry
belongs to the orbital angular momentum ofquark-antiquark cloud in internal
structure of constituent quarks. The --dependence of asymmetries in the
charged pion production at large reflects the corresponding dependence of
constituent quark polarization in the polarized proton.Comment: LaTeX, 8 pages, 3 figures. One figure added, as it appears in Phys.
Rev.
Charge order, dynamics, and magneto-structural transition in multiferroic LuFeO
We investigated the series of temperature and field-driven transitions in
LuFeO by optical and M\"{o}ssbauer spectroscopies, magnetization, and
x-ray scattering in order to understand the interplay between charge,
structure, and magnetism in this multiferroic material. We demonstrate that
charge fluctuation has an onset well below the charge ordering transition,
supporting the "order by fluctuation" mechanism for the development of charge
order superstructure. Bragg splitting and large magneto optical contrast
suggest a low temperature monoclinic distortion that can be driven by both
temperature and magnetic field.Comment: 4 pages, 3 figures, PRL in prin
Musculoskeletal Manifestations of COVID-19: A Systematic Search and Review
Coronavirus disease (COVID-19) started its journey around the world from Wuhan, China and gradually became a pandemic.
COVID-19 often affects the respiratory system, but symptoms may include fatigue, myalgia, arthralgia, arthritis, and spine and bone pain as presenting complaints. In the present systematic search and review, we aim to highlight the musculoskeletal manifestations during COVID-19.
PubMed Central and Google Scholar search engines were searched for the key words “muscle pain”, “joint pain”, “body ache”, and “fatigue”, in Covid-19 patients.
After screening, a total of 76 articles dated between January 1 and July 1, 2020 met the inclusion criteria and were included in the study. All articles were published in English comprising 36,558 COVID-19 cases.
In cross-sectional studies, fatigue was found in 55%, myalgia in 26%, and arthralgia in 20% of cases, respectively. In cohort studies, fatigue was found in 35%, myalgia in 15%, and arthralgia in 5%, respectively. Sporadic case reports also mention back pain, bone pain, myositis, and arthritis as presenting symptoms of COVID-19.
Fatigue was the most frequent musculoskeletal (MSK) manifestation of COVID-19 followed by myalgia and joint pain. The frequency of the different MSK manifestations in COVID-19 may vary widely among different geographic regions.
MSK like fatigue, myalgia and arthralgia are frequent symptoms in COVID-19 patients and may vary in different countries
Mass measurements in the vicinity of the doubly-magic waiting point 56Ni
Masses of 56,57Fe, 53Co^m, 53,56Co, 55,56,57Ni, 57,58Cu, and 59,60Zn have
been determined with the JYFLTRAP Penning trap mass spectrometer at IGISOL with
a precision of dm/m \le 3 x 10^{-8}. The QEC values for 53Co, 55Ni, 56Ni, 57Cu,
58Cu, and 59Zn have been measured directly with a typical precision of better
than 0.7 keV and Coulomb displacement energies have been determined. The Q
values for proton captures on 55Co, 56Ni, 58Cu, and 59Cu have been measured
directly. The precision of the proton-capture Q value for 56Ni(p,gamma)57Cu,
Q(p,gamma) = 689.69(51) keV, crucial for astrophysical rp-process calculations,
has been improved by a factor of 37. The excitation energy of the proton
emitting spin-gap isomer 53Co^m has been measured precisely, Ex = 3174.3(10)
keV, and a Coulomb energy difference of 133.9(10) keV for the 19/2- state has
been obtained. Except for 53Co, the mass values have been adjusted within a
network of 17 frequency ratio measurements between 13 nuclides which allowed
also a determination of the reference masses 55Co, 58Ni, and 59Cu.Comment: 14 pages, 13 figures, submitted to Phys. Rev.
- …