3,132 research outputs found
Towards Mapping Competencies through Learning Analytics: Real-time Competency Assessment for Career Direction through Interactive Simulation
Assessment and Evaluation in Higher Education, 201, pp. 1-13
Mitigating Case Mix Factors by Choice of Glycemic Control Performance Measure Threshold
OBJECTIVEâPerformance measures are tools for assessing quality of care but may be influenced by patient factors. We investigated how currently endorsed performance measures for glycemic control in diabetes may be influenced by case mix composition. We assessed differences in A1C performance measure threshold attainment by case mix factors for A1C >9% and examined how lowering the threshold to A1C >8% or >7% changed these differences
Turbulence in the Solar Atmosphere: Manifestations and Diagnostics via Solar Image Processing
Intermittent magnetohydrodynamical turbulence is most likely at work in the
magnetized solar atmosphere. As a result, an array of scaling and multi-scaling
image-processing techniques can be used to measure the expected
self-organization of solar magnetic fields. While these techniques advance our
understanding of the physical system at work, it is unclear whether they can be
used to predict solar eruptions, thus obtaining a practical significance for
space weather. We address part of this problem by focusing on solar active
regions and by investigating the usefulness of scaling and multi-scaling
image-processing techniques in solar flare prediction. Since solar flares
exhibit spatial and temporal intermittency, we suggest that they are the
products of instabilities subject to a critical threshold in a turbulent
magnetic configuration. The identification of this threshold in scaling and
multi-scaling spectra would then contribute meaningfully to the prediction of
solar flares. We find that the fractal dimension of solar magnetic fields and
their multi-fractal spectrum of generalized correlation dimensions do not have
significant predictive ability. The respective multi-fractal structure
functions and their inertial-range scaling exponents, however, probably provide
some statistical distinguishing features between flaring and non-flaring active
regions. More importantly, the temporal evolution of the above scaling
exponents in flaring active regions probably shows a distinct behavior starting
a few hours prior to a flare and therefore this temporal behavior may be
practically useful in flare prediction. The results of this study need to be
validated by more comprehensive works over a large number of solar active
regions.Comment: 26 pages, 7 figure
Low-Energy Theorems from Holography
In the context of gauge/gravity duality, we verify two types of gauge theory
low-energy theorems, the dilation Ward identities and the decoupling of heavy
flavor. First, we provide an analytic proof of non-trivial dilation Ward
identities for a theory holographically dual to a background with gluon
condensate (the self-dual Liu--Tseytlin background). In this way an important
class of low-energy theorems for correlators of different operators with the
trace of the energy-momentum tensor is established, which so far has been
studied in field theory only. Another low-energy relationship, the so-called
decoupling theorem, is numerically shown to hold universally in three
holographic models involving both the quark and the gluon condensate. We show
this by comparing the ratio of the quark and gluon condensates in three
different examples of gravity backgrounds with non-trivial dilaton flow. As a
by-product of our study, we also obtain gauge field condensate contributions to
meson transport coefficients.Comment: 32 pages, 4 figures, two references added, typos remove
Structure of the trypanosome transferrin receptor reveals mechanisms of ligand recognition and immune evasion.
To maintain prolonged infection of mammals, African trypanosomes have evolved remarkable surface coats and a system of antigenic variation1. Within these coats are receptors for macromolecular nutrients such as transferrin2,3. These must be accessible to their ligands but must not confer susceptibility to immunoglobulin-mediated attack. Trypanosomes have a wide host range and their receptors must also bind ligands from diverse species. To understand how these requirements are achieved, in the context of transferrin uptake, we determined the structure of a Trypanosoma brucei transferrin receptor in complex with human transferrin, showing how this heterodimeric receptor presents a large asymmetric ligand-binding platform. The trypanosome genome contains a family of around 14 transferrin receptors4, which has been proposed to allow binding to transferrin from different mammalian hosts5,6. However, we find that a single receptor can bind transferrin from a broad range of mammals, indicating that receptor variation is unlikely to be necessary for promiscuity of host infection. In contrast, polymorphic sites and N-linked glycans are preferentially found in exposed positions on the receptor surface, not contacting transferrin, suggesting that transferrin receptor diversification is driven by a need for antigenic variation in the receptor to prolong survival in a host
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