1,144 research outputs found
COSMOGRAIL: the COSmological MOnitoring of GRAvItational Lenses XV. Assessing the achievability and precision of time-delay measurements
COSMOGRAIL is a long-term photometric monitoring of gravitationally lensed
QSOs aimed at implementing Refsdal's time-delay method to measure cosmological
parameters, in particular H0. Given long and well sampled light curves of
strongly lensed QSOs, time-delay measurements require numerical techniques
whose quality must be assessed. To this end, and also in view of future
monitoring programs or surveys such as the LSST, a blind signal processing
competition named Time Delay Challenge 1 (TDC1) was held in 2014. The aim of
the present paper, which is based on the simulated light curves from the TDC1,
is double. First, we test the performance of the time-delay measurement
techniques currently used in COSMOGRAIL. Second, we analyse the quantity and
quality of the harvest of time delays obtained from the TDC1 simulations. To
achieve these goals, we first discover time delays through a careful inspection
of the light curves via a dedicated visual interface. Our measurement
algorithms can then be applied to the data in an automated way. We show that
our techniques have no significant biases, and yield adequate uncertainty
estimates resulting in reduced chi2 values between 0.5 and 1.0. We provide
estimates for the number and precision of time-delay measurements that can be
expected from future time-delay monitoring campaigns as a function of the
photometric signal-to-noise ratio and of the true time delay. We make our blind
measurements on the TDC1 data publicly availableComment: 11 pages, 8 figures, published in Astronomy & Astrophysic
Impact of the 3D source geometry on time-delay measurements of lensed type-Ia Supernovae
It has recently been proposed that gravitationally lensed type-Ia supernovae
can provide microlensing-free time-delay measurements provided that the
measurement is taken during the achromatic expansion phase of the explosion and
that color light curves are used rather than single-band light curves. If
verified, this would provide both precise and accurate time-delay measurements,
making lensed type-Ia supernovae a new golden standard for time-delay
cosmography. However, the 3D geometry of the expanding shell can introduce an
additional bias that has not yet been fully explored. In this work, we present
and discuss the impact of this effect on time-delay cosmography with lensed
supernovae and find that on average it leads to a bias of a few tenths of a day
for individual lensed systems. This is negligible in view of the cosmological
time delays predicted for typical lensed type-Ia supernovae but not for the
specific case of the recently discovered type-Ia supernova iPTF16geu, whose
time delays are expected to be smaller than a day.Comment: 7 pages, 4 figures, published in A&
Nationwide introduction of a new competency framework for undergraduate medical curricula: a collaborative approach.
Switzerland recently introduced PROFILES, a revised version of its national outcomes reference framework for the undergraduate medical curriculum. PROFILES is based on a set of competencies adapted from the CanMEDS framework and nine entrustable professional activities (EPAs) that students have to be able to perform autonomously in the context of a predefined list of clinical situations. The nationwide implementation of such a competency- and EPA-based approach to medical education is a complex process that represents an important change to the organisation of undergraduate training in the various medical schools. At the same time, the concepts underlying PROFILES also have to be reflected at the level of the Federal Licencing Examination (FLE) and the national accreditation process. The vice-deans for education mandated a Swiss Working Group for PROFILES Implementation (SWGPI) to elaborate a guide presenting the principles and best practices based on the current scientific literature, to ensure the coherence between the future developments of the medical curricula and the evolution of the FLE, and to propose a coordinated research agenda to evaluate the implementation process. On the basis of the literature and analysis of our national context, we determined the key elements important for a successful implementation. They can be grouped into several areas including curricular design and governance, the assessment system and entrustment process, faculty development and change management. We also identified two dimensions that will be of particular importance to create synergies and facilitate exchange between the medical schools: a systematic approach to curriculum mapping and the longitudinal integration of an e-portfolio to support the student learning process. The nationwide collaborative approach to define strategies and conditions for the implementation of a new reference framework has allowed to develop a shared understanding of the implications of PROFILES, to promote the establishment of Swiss mapping and e-portfolio communities, and to establish the conditions necessary for ensuring the continuous alignment of the FLE with the evolving medical curricula
Calling situated: a survey among medical students supplemented by a qualitative study and a comparison with a surveyed sample of physicians.
Calling within the medical context receives growing academic attention and empirical research has started to demonstrate its beneficial effects. The purpose of this study is to investigate what motivates students to enter medical school and what role calling may play (i), to evaluate if calling influences the way in which they experience their studies (ii), and to compare medical students' experience of calling with those of physicians.
A questionnaire survey was distributed among medical students (N = 1048; response rate above 60%) of the University of Lausanne in Switzerland. It was supplemented by a group discussion between bachelor medical students (N = 8) and senior physicians (N = 4), focusing on different facets of calling. An existing data set of a survey among physicians, addressing calling with the same questionnaire, was used to compare students' and physicians' attitudes towards calling. Survey data were analyzed with the habitual statistical procedures for categorical and continuous variables. The group discussion was analyzed with thematic analysis.
The survey showed that experiencing calling is a motivational factor for study choice and influences positively choice consistency. Students experiencing calling differed from those who did not: they attributed different definitions to calling, indicated more often prosocial motivational factors for entering medical school and perceived the learning context as less burdensome. The analysis of the group discussion revealed that the concept of calling has a fluid definition. It was conceived as having the characteristics of a double-edged sword and as originating from within or outside or from a dialectic interplay between the inner and outer world. Finally, calling is experienced less often by physicians than by medical students, with a decreasing prevalence as the immersion in the clinical years of the study of medicine progresses.
Calling plays an important role in study choice and consistency of medical students. Given its relevance for medical students and its ramifications with the learning context, calling should become a topic of the reflexive parts of the medical curriculum. We critically discuss the role played by calling for medical students and provide some perspectives on how calling could be integrated in the reflection and teaching on physicianhood
Offset-free economic mpc based on modifier adaptation: Investigation of several gradient-estimation techniques
Various offset-free economic model predictive control schemes that include a disturbance model and the modifier-adaptation principle have been proposed in recent years. These schemes are able to reach plant optimality asymptotically even in the presence of plantâmodel mismatch. All schemes are affected by a major issue that is common to all modifier-adaptation formulations, namely, plant optimality (note that convergence per se does not require perfect plant gradients) requires perfect knowledge of static plant gradients, which is a piece of information not known in most practical applications. To address this issue, we present two gradient-estimation techniques, one based on Broydenâs update and the other one on linear regression. We apply these techniques for the estimation of either the plant gradients or the modifiers directly. The resulting economic MPC schemes are tested in a simulation and compared on two benchmark examples of different complexity with respect to both convergence speed and robustness to measurement noise
Dynamic control of selectivity in the ubiquitination pathway revealed by an ASP to GLU substitution in an intra-molecular salt-bridge network
Ubiquitination relies on a subtle balance between selectivity and promiscuity achieved through specific interactions between ubiquitin-conjugating enzymes (E2s) and ubiquitin ligases (E3s). Here, we report how a single aspartic to glutamic acid substitution acts as a dynamic switch to tip the selectivity balance of human E2s for interaction toward E3 RING-finger domains. By combining molecular dynamic simulations, experimental yeast-two-hybrid screen of E2-E3 (RING) interactions and mutagenesis, we reveal how the dynamics of an internal salt-bridge network at the rim of the E2-E3 interaction surface controls the balance between an âopenâ, binding competent, and a âclosedâ, binding incompetent state. The molecular dynamic simulations shed light on the fine mechanism of this molecular switch and allowed us to identify its components, namely an aspartate/glutamate pair, a lysine acting as the central switch and a remote aspartate. Perturbations of single residues in this network, both inside and outside the interaction surface, are sufficient to switch the global E2 interaction selectivity as demonstrated experimentally. Taken together, our results indicate a new mechanism to control E2-E3 interaction selectivity at an atomic level, highlighting how minimal changes in amino acid side-chain affecting the dynamics of intramolecular salt-bridges can be crucial for protein-protein interactions. These findings indicate that the widely accepted sequence-structure-function paradigm should be extended to sequence-structure-dynamics-function relationship and open new possibilities for control and fine-tuning of protein interaction selectivity
A proteinâDNA docking benchmark
We present a proteinâDNA docking benchmark containing 47 unboundâunbound test cases of which 13 are classified as easy, 22 as intermediate and 12 as difficult cases. The latter shows considerable structural rearrangement upon complex formation. DNA-specific modifications such as flipped out bases and base modifications are included. The benchmark covers all major groups of DNA-binding proteins according to the classification of Luscombe et al., except for the zipper-type group. The variety in test cases make this non-redundant benchmark a useful tool for comparison and development of proteinâDNA docking methods. The benchmark is freely available as download from the internet
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