573 research outputs found
Practices of readiness: punctuation, poise and the contingencies of participatory design
How do we ready ourselves to intervene responsively in the contingent situations that arise in co-designing to make change? How do we attune to group dynamics and respond ethically to unpredictable developments when working with âcommunityâ? Participatory Design (PD) can contribute to social transitions, yet its focus is often tightly tuned to technique for designing ICT at the cost of participatory practice. We challenge PD conventions by addressing what happens as we step into a situation to alter it with others, an aspect of practice that cannot be replicated or interchanged. We do so to argue that practices of readiness are constituted by personal histories, experiences, philosophies and culture. We demonstrate this political argument by giving reflexive accounts of our dimensions of preparation. The narratives here are distinct, yet reveal complementary theories and worldviews that shape PD ontologies. We have organized these around the qualities of punctuation and poise as a way to draw out some less easily articulated aspects of PD practice
Effective Action of Spontaneously Broken Gauge Theories
The effective action of a Higgs theory should be gauge-invariant. However,
the quantum and/or thermal contributions to the effective potential seem to be
gauge-dependent, posing a problem for its physical interpretation. In this
paper, we identify the source of the problem and argue that in a Higgs theory,
perturbative contributions should be evaluated with the Higgs fields in the
polar basis, not in the Cartesian basis. Formally, this observation can be made
from the derivation of the Higgs theorem, which we provide. We show explicitly
that, properly defined, the effective action for the Abelian Higgs theory is
gauge invariant to all orders in perturbation expansion when evaluated in the
covariant gauge in the polar basis. In particular, the effective potential is
gauge invariant. We also show the equivalence between the calculations in the
covariant gauge in the polar basis and the unitary gauge. These points are
illustrated explicitly with the one-loop calculations of the effective action.
With a field redefinition, we obtain the physical effective potential. The
SU(2) non-Abelian case is also discussed.Comment: Expanded version, 32 pages, figures produced by LaTeX, plain LaTe
Preparation and characterization of avenin-enriched oat protein by chill precipitation for feeding trials in celiac disease
The safety of oats for people with celiac disease remains unresolved. While oats have attractive nutritional properties that can improve the quality and palatability of the restrictive, low fiber gluten-free diet, rigorous feeding studies to address their safety in celiac disease are needed. Assessing the oat prolamin proteins (avenins) in isolation and controlling for gluten contamination and other oat components such as fiber that can cause non-specific effects and symptoms is crucial. Further, the avenin should contain all reported immunogenic T cell epitopes, and be deliverable at a dose that enables biological responses to be correlated with clinical effects. To date, isolation of a purified food-grade avenin in sufficient quantities for feeding studies has not been feasible. Here, we report a new gluten isolation technique that enabled 2 kg of avenin to be extracted from 400 kg of wheat-free oats under rigorous gluten-free and food grade conditions. The extract consisted of 85% protein of which 96% of the protein was avenin. The concentration of starch (1.8% dry weight), ÎČ-glucan (0.2% dry weight), and free sugars (1.8% dry weight) were all low in the final avenin preparation. Other sugars including oligosaccharides, small fructans, and other complex sugars were also low at 2.8% dry weight. Liquid chromatography tandem mass spectrometry (LC-MS/MS) analysis of the proteins in these preparations showed they consisted only of oat proteins and were uncontaminated by gluten containing cereals including wheat, barley or rye. Proteomic analysis of the avenin enriched samples detected more avenin subtypes and fewer other proteins compared to samples obtained using other extraction procedures. The identified proteins represented five main groups, four containing known immune-stimulatory avenin peptides. All five groups were identified in the 50% (v/v) ethanol extract however the group harboring the epitope DQ2.5-ave-1b was less represented. The avenin-enriched protein fractions were quantitatively collected by reversed phase HPLC and analyzed by MALDI-TOF mass spectrometry. Three reverse phase HPLC peaks, representing ~40% of the protein content, were enriched in proteins containing DQ2.5-ave-1a epitope. The resultant high quality avenin will facilitate controlled and definitive feeding studies to establish the safety of oat consumption by people with celiac disease
Wall and Anti-Wall in the Randall-Sundrum Model and A New Infrared Regularization
An approach to find the field equation solution of the Randall-Sundrum model
with the extra axis is presented. We closely examine the infrared
singularity. The vacuum is set by the 5 dimensional Higgs field. Both the
domain-wall and the anti-domain-wall naturally appear, at the {\it ends} of the
extra compact axis, by taking a {\it new infrared regularization}. The
stability is guaranteed from the outset by the kink boundary condition. A {\it
continuous} (infrared-)regularized solution, which is a truncated {\it Fourier
series} of a {\it discontinuous} solution, is utilized.The ultraviolet-infrared
relation appears in the regularized solution.Comment: 36 pages, 29 eps figure file
Tunneling and propagation of vacuum bubbles on dynamical backgrounds
In the context of bubble universes produced by a first-order phase transition
with large nucleation rates compared to the inverse dynamical time scale of the
parent bubble, we extend the usual analysis to non-vacuum backgrounds. In
particular, we provide semi-analytic and numerical results for the modified
nucleation rate in FLRW backgrounds, as well as a parameter study of bubble
walls propagating into inhomogeneous (LTB) or FLRW spacetimes, both in the
thin-wall approximation. We show that in our model, matter in the background
often prevents bubbles from successful expansion and forces them to collapse.
For cases where they do expand, we give arguments why the effects on the
interior spacetime are small for a wide range of reasonable parameters and
discuss the limitations of the employed approximations.Comment: 29 pages, 8 figures, typos corrected, matches published versio
Enhancement of the Thermal Conductivity in gapped Quantum Spin Chains
We study mechanism of magnetic energy transport, motivated by recent
measurements of the thermal conductivity in low dimensional quantum magnets. We
point out a possible mechanism of enhancement of the thermal conductivity in
gapped magnetic system, where the magnetic energy transport plays a crucial
role. This mechanism gives an interpretation for the recent experiment of
CuGeO_3, where the thermal conductivity depends on the crystal direction.Comment: 4 pages, 2 figure
An Effective Supergravity for the Thermal Phases of N=4 Strings
A universal effective supergravity Lagrangian describing the thermal phases
of heterotic strings on T^4 x S^1, IIA and IIB strings on K^3 x S^1 is
constructed. The resulting non-perturbative phase structure is discussed.Comment: 9 pages, 6th Hellenic School and Workshop, Corfu, Greece, Sept. 9
Consistency in Polyclonal T-cell Responses to Gluten between Children and Adults with Celiac Disease
BACKGROUND & AIMS:
Developing antigen-specific approaches for diagnosis and treatment of celiac disease requires a detailed understanding of the specificity of T cells for gluten. The existing paradigm is that T-cell lines and clones from children differ from those of adults in the hierarchy and diversity of peptide recognition. We aimed to characterize the T-cell response to gluten in children vs adults with celiac disease.
METHODS:
Forty-one children with biopsy-proven celiac disease (median age, 9 years old; 17 male), who had been on strict gluten-free diets for at least 3 months, were given a 3-day challenge with wheat; blood samples were collected and gluten-specific T cells were measured. We analyzed responses of T cells from these children and from 4 adults with celiac disease to a peptide library and measured T-cell receptor bias. We isolated T-cell clones that recognized dominant peptides and assessed whether gluten peptide recognition was similar between T-cell clones from children and adults.
RESULTS:
We detected gluten-specific responses by T cells from 30 of the children with celiac disease (73%). T cells from the children recognized the same peptides that were immunogenic to adults with celiac disease; deamidation of peptides increased these responses. Age and time since diagnosis did not affect the magnitude of T-cell responses to dominant peptides. T-cell clones specific for dominant α- or Ï-gliadin peptides from children with celiac disease had comparable levels of reactivity to wheat, rye, and barley peptides as T-cell clones from adults with celiac disease. The α-gliadin-specific T cells from children had biases in T-cell receptor usage similar to those in adults.
CONCLUSIONS:
T cells from children with celiac disease recognize similar gluten peptides as T cells from adults with celiac disease. The findings indicate that peptide-based diagnostics and therapeutics for adults may also be used for children.
Copyright © 2015 AGA Institute. Published by Elsevier Inc. All rights reserved
One-loop SYM-supergravity relation for five-point amplitudes
We derive a linear relation between the one-loop five-point amplitude of N=8
supergravity and the one-loop five-point subleading-color amplitudes of N=4
supersymmetric Yang-Mills theory.Comment: 17 pages, 2 figures; v2: very minor correction
Reheating the Universe After Multi-Field Inflation
We study in detail (p)reheating after multi-field inflation models with a
particular focus on N-flation. We consider a variety of different couplings
between the inflatons and the matter sector, including both quartic and
trilinear interactions with a light scalar field. We show that the presence of
multiple oscillating inflatons makes parametric resonance inefficient in the
case of the quartic interactions. Moreover, perturbative processes do not
permit a complete decay of the inflaton for this coupling. In order to recover
the hot big bang, we must instead consider trilinear couplings. In this case we
show that strong nonperturbative preheating is possible via multi-field
tachyonic resonance. In addition, late-time perturbative effects do permit a
complete decay of the condensate. We also study the production of gauge fields
for several prototype couplings, finding similar results to the trilinear
scalar coupling. During the course of our analysis we develop the mathematical
theory of the quasi-periodic Mathieu equation, the multi-field generalization
of the Floquet theory familiar from preheating after single field inflation. We
also elaborate on the theory of perturbative decays of a classical inflaton
condensate, which is applicable in single-field models also.Comment: 46+1 pages, 19 figure
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