1,603 research outputs found
Performing an Invisibility Spell: Global Models, Food Regimes and Smallholders
The present construction of global representations of food and farming is problematic. For example, how can we ‘know’ the world needs to double food production even though we cannot foresee a food crisis? How can we estimate investment opportunities while failing to quantify their impacts on smallholders? Global models constrain the manner in which we perceive the food regime while producing such representations. We need to identify the causal relations embedded inside models’ equations and why they are arrayed in this fashion. This article combines actor-network theory and structuration theory to analyse a sample of 70 global models. It locates the modules and equations of these black boxes in the sociotechnical and political context of their production. Finally, a bibliometric analysis sketches the overall epistemic community that drove models into success or extinction. Dominant global models recycle equations, modules and databases to effectuate narrow worlds. They make smallholder farming invisible in spite of its prevalence around the world. They do not address food needs and construct pixellated representations of underutilized land. They systematically favour large-scale agricultural trade and investments in production and productivity. This reflects the structure of signification modellers adhere to as well as the structure of domination they are embedded in. Securing clients ensures the success of global models independently from their validation. The article demonstrates the manner in which modelling is a social practice embedded in power relations. Considering simultaneously the structure of domination formalized inside models and surrounding modelling is crucial. Future research should investigate how various actors resort to global models to champion their goals. It should question the policy recommendations drawn from such models and their relevance as decision support tools.ualisms, what leads us to believe that dualistic oppositions are still a part of the agri-food reality and are something to take into account when different actors have to collaborate
Bottomonium from NRQCD with Dynamical Wilson Fermions
We present results for the b \bar b spectrum obtained using an
O(M_bv^6)-correct non-relativistic lattice QCD action. Propagators are
evaluated on SESAM's three sets of dynamical gauge configurations generated
with two flavours of Wilson fermions at beta = 5.6. Compared to a quenched
simulation at equivalent lattice spacing we find better agreement of our
dynamical data with experimental results in the spin-independent sector but
observe no unquenching effects in hyperfine-splittings. To pin down the
systematic errors we have also compared quenched results in different
``tadpole'' schemes and used a lower order action.Comment: Talk presented at LATTICE'97, 3 pages, Late
B Physics on the Lattice: Present and Future
Recent experimental measurements and lattice QCD calculations are now
reaching the precision (and accuracy) needed to over-constrain the CKM
parameters and . In this brief review, I discuss the
current status of lattice QCD calculations needed to connect the experimental
measurements of meson properties to quark flavor-changing parameters.
Special attention is given to , which is becoming a competitive
way to determine , and to mixings, which now include
reliable extrapolation to the physical light quark mass. The combination of the
recent measurement of the mass difference and current lattice
calculations dramatically reduces the uncertainty in . I present an
outlook for reducing dominant lattice QCD uncertainties entering CKM fits, and
I remark on lattice calculations for other decay channels.Comment: Invited brief review for Mod. Phys. Lett. A. 15 pages. v2: typos
corrected, references adde
Development and validation of clinical profiles of patients hospitalized due to behavioral and psychological symptoms of dementia.
Patients hospitalized on acute psychogeriatric wards are a heterogeneous population. Cluster analysis is a useful statistical method for partitioning a sample of patients into well separated groups of patients who present common characteristics. Several patient profile studies exist, but they are not adapted to acutely hospitalized psychogeriatric patients with cognitive impairment. The present study aims to partition patients hospitalized due to behavioral and psychological symptoms of dementia into profiles based on a global evaluation of mental health using cluster analysis.
Using nine of the 13 items from the Health of the Nation Outcome Scales for elderly people (HoNOS65+), data were collected from a sample of 542 inpatients with dementia who were hospitalized between 2011 and 2014 in acute psychogeriatric wards of a Swiss university hospital. An optimal clustering solution was generated to represent various profiles, by using a mixed approach combining hierarchical and non-hierarchical (k-means) cluster analyses associated with a split-sample cross-validation. The quality of the clustering solution was evaluated based on a cross-validation, on a k-means method with 100 random initial seeds, on validation indexes, and on clinical interpretation.
The final solution consisted of four clinically distinct and homogeneous profiles labeled (1) BPSD-affective, (2) BPSD-functional, (3) BPSD-somatic and (4) BPSD-psychotic according to their predominant clinical features. The four profiles differed in cognitive status, length of hospital stay, and legal admission status.
In the present study, clustering methods allowed us to identify four profiles with distinctive characteristics. This clustering solution may be developed into a classification system that may allow clinicians to differentiate patient needs in order to promptly identify tailored interventions and promote better allocation of available resources
Unquenched Charmonium with NRQCD - Lattice 2000
We present results from a series of NRQCD simulations of the charmonium
system, both in the quenched approximation and with n_f = 2 dynamical quarks.
The spectra show evidence for quenching effects of ~10% in the S- and
P-hyperfine splittings. We compare this with other systematic effects.
Improving the NRQCD evolution equation altered the S-hyperfine by as much as 20
MeV, and we estimate radiative corrections may be as large as 40%.Comment: Lattice 2000 (Heavy Quark Physics
To what distances do we know the confining potential?
We argue that asymptotically linear static potential is built in into the
common procedure of extracting it from lattice Wilson loop measurements. To
illustrate the point, we extract the potential by the standard lattice method
in a model vacuum made of instantons. A beautiful infinitely rising linear
potential is obtained in the case where the true potential is actually
flattening. We argue that the flux tube formation might be also an artifact of
the lattice procedure and not necessarily a measured physical effect.
We conclude that at present the rising potential is known for sure up to no
more than about 0.7 fm. It may explain why no screening has been clearly
observed so far for adjoint sources and for fundamental sources but with
dynamical fermions.
Finally, we speculate on how confinement could be achieved even if the static
potential in the pure glue theory is not infinitely rising.Comment: 16 pages, 5 figures. Additional arguments presented, a new figure and
references adde
Perturbative expansions from Monte Carlo simulations at weak coupling: Wilson loops and the static-quark self-energy
Perturbative coefficients for Wilson loops and the static-quark self-energy
are extracted from Monte Carlo simulations at weak coupling. The lattice
volumes and couplings are chosen to ensure that the lattice momenta are all
perturbative. Twisted boundary conditions are used to eliminate the effects of
lattice zero modes and to suppress nonperturbative finite-volume effects due to
Z(3) phases. Simulations of the Wilson gluon action are done with both periodic
and twisted boundary conditions, and over a wide range of lattice volumes (from
to ) and couplings (from to ).
A high precision comparison is made between the simulation data and results
from finite-volume lattice perturbation theory. The Monte Carlo results are
shown to be in excellent agreement with perturbation theory through second
order. New results for third-order coefficients for a number of Wilson loops
and the static-quark self-energy are reported.Comment: 36 pages, 15 figures, REVTEX documen
Unstable Modes in Three-Dimensional SU(2) Gauge Theory
We investigate SU(2) gauge theory in a constant chromomagnetic field in three
dimensions both in the continuum and on the lattice. Using a variational method
to stabilize the unstable modes, we evaluate the vacuum energy density in the
one-loop approximation. We compare our theoretical results with the outcomes of
the numerical simulations.Comment: 24 pages, REVTEX 3.0, 3 Postscript figures included. (the whole
postscript file (text+figures) is available on request from
[email protected]
The Savvidy ``ferromagnetic vacuum'' in three-dimensional lattice gauge theory
The vacuum effective potential of three-dimensional SU(2) lattice gauge
theory in an applied color-magnetic field is computed over a wide range of
field strengths. The background field is induced by an external current, as in
continuum field theory. Scaling and finite volume effects are analyzed
systematically. The first evidence from lattice simulations is obtained of the
existence of a nontrivial minimum in the effective potential. This supports a
``ferromagnetic'' picture of gluon condensation, proposed by Savvidy on the
basis of a one-loop calculation in (3+1)-dimensional QCD.Comment: 9pp (REVTEX manuscript). Postscript figures appende
Chiral Symmetry Breaking and Cooling in Lattice QCD
Chiral symmetry breaking is calculated as a function of cooling in quenched
lattice QCD. A non-zero signal is found for the chiral condensate beyond one
hundred cooling steps, suggesting that there is chiral symmetry breaking
associated with instantons. Quantitatively, the chiral condensate in cooled
gauge field configurations is small compared to the value without cooling.Comment: 11 pages in REVTEX including 4 PS figures embedded using psfig.sty,
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