833 research outputs found
CMB temperature anisotropy at large scales induced by a causal primordial magnetic field
We present an analytical derivation of the Sachs Wolfe effect sourced by a
primordial magnetic field. In order to consistently specify the initial
conditions, we assume that the magnetic field is generated by a causal process,
namely a first order phase transition in the early universe. As for the
topological defects case, we apply the general relativistic junction conditions
to match the perturbation variables before and after the phase transition which
generates the magnetic field, in such a way that the total energy momentum
tensor is conserved across the transition and Einstein's equations are
satisfied. We further solve the evolution equations for the metric and fluid
perturbations at large scales analytically including neutrinos, and derive the
magnetic Sachs Wolfe effect. We find that the relevant contribution to the
magnetic Sachs Wolfe effect comes from the metric perturbations at
next-to-leading order in the large scale limit. The leading order term is in
fact strongly suppressed due to the presence of free-streaming neutrinos. We
derive the neutrino compensation effect dynamically and confirm that the
magnetic Sachs Wolfe spectrum from a causal magnetic field behaves as
l(l+1)C_l^B \propto l^2 as found in the latest numerical analyses.Comment: 31 pages, 2 figures, minor changes, matches published versio
A null test to probe the scale dependence of the growth of structure as a test of general relativity
The main science driver for the coming generation of cosmological surveys is understanding dark energy that relies on testing general relativity on the largest scales. Once we move beyond the simplest explanation for dark energy of a cosmological constant, the space of possible theories becomes both vast and extremely hard to compute realistic observables. A key discriminator of a cosmological constant, however, is that the growth of structure is scale invariant on large scales. By carefully weighting observables derived from distributions of galaxies and a dipole pattern in their apparent sizes, we construct a null test that vanishes for any model of gravity or dark energy where the growth of structure is scale independent. It relies only on very few assumptions about cosmology, and does not require any modelling of the growth of structure. We show that with a survey like the Dark Energy Spectroscopic Instrument (DESI) a scale dependence of the order of 10–20 per cent can be detected at 3σ with the null test, which will drop by a factor of 2 for a survey like the Square Kilometre Array. We also show that the null test is very insensitive to typical uncertainties in other cosmological parameters including massive neutrinos and scale-dependent bias, making this a key null test for dark energy
Combined On-Line and Run-to-Run Optimization of Batch Processes with Terminal Constraints
This paper describes the optimization of batch processes in the presence of uncertainty and constraints. The optimal solution consists of keeping certain path and terminal constraints active and driving the sensitivities to zero. The case where the terminal constraints have a larger bearing on the cost than the sensitivities is considered, for which a two-time-scale methodology is proposed. The problem of meeting the active terminal constraints is addressed on-line using trajectory tracking, whilst pushing the sensitivities to zero is implemented on a run-to-run basis. The paper also discusses the run-to-run improvement of trajectory tracking via iterative learning control. The proposed methodology is illustrated in simulation on a batch distillation system
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
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
The Hubble Constant determined through an inverse distance ladder including quasar time delays and Type Ia supernovae
Context. The precise determination of the present-day expansion rate of the
Universe, expressed through the Hubble constant , is one of the most
pressing challenges in modern cosmology. Assuming flat CDM,
inference at high redshift using cosmic-microwave-background data from Planck
disagrees at the 4.4 level with measurements based on the local
distance ladder made up of parallaxes, Cepheids and Type Ia supernovae (SNe
Ia), often referred to as "Hubble tension". Independent,
cosmological-model-insensitive ways to infer are of critical importance.
Aims. We apply an inverse-distance-ladder approach, combining strong-lensing
time-delay-distance measurements with SN Ia data. By themselves, SNe Ia are
merely good relative distance indicators, but by anchoring them to strong
gravitational lenses one can obtain an measurement that is relatively
insensitive to other cosmological parameters. Methods. A cosmological parameter
estimate is performed for different cosmological background models, both for
strong-lensing data alone and for the combined lensing + SNe Ia data sets.
Results. The cosmological-model dependence of strong-lensing measurements
is significantly mitigated through the inverse distance ladder. In combination
with SN Ia data, the inferred consistently lies around 73-74 km s
Mpc, regardless of the assumed cosmological background model. Our
results agree nicely with those from the local distance ladder, but there is a
>2 tension with Planck results, and a ~1.5 discrepancy with
results from an inverse distance ladder including Planck, Baryon Acoustic
Oscillations and SNe Ia. Future strong-lensing distance measurements will
reduce the uncertainties in from our inverse distance ladder.Comment: 5 pages, 3 figures, A&A letters accepted versio
Первичный умлаут в немецком языке (на материале древних текстов)
Статья из специализированного выпуска научного журнала "Культура народов Причерноморья", материалы которого объединены общей темой "Язык и Мир" и посвящены общим вопросам Языкознания и приурочены к 80-летию со дня рождения Николая Александровича Рудякова.Стаття із спеціалізованого випуску наукового журналу "Культура народов Причерноморья", матеріали якого поєднані загальною темою "Мова і Світ" і присвячені загальним питанням мовознавства і приурочені до 80-річчя з дня народження Миколи Олександровича Рудякова
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