18,993 research outputs found
How can exploratory learning with games and simulations within the curriculum be most effectively evaluated?
There have been few attempts to introduce frameworks that can help support tutors evaluate educational games and simulations that can be most effective in their particular learning context and subject area. The lack of a dedicated framework has produced a significant impediment for uptake of games and simulations particularly in formal learning contexts. This paper aims to address this shortcoming by introducing a four-dimensional framework for helping tutors to evaluate the potential of using games- and simulation- based learning in their practice, and to support more critical approaches to this form of games and simulations. The four-dimensional framework is applied to two examples from practice to test its efficacy and structure critical reflection upon practice
Introduction to Focus Issue : Dynamics in Systems Biology
Peer reviewedPublisher PD
Crystal structure of the catalytic fragment of murine poly(ADP-ribose) polymerase-2.
Poly(ADP-ribose) polymerase-1 (PARP-1) has become an important pharmacological target in the treatment of cancer due to its cellular role as a 'DNA-strand break sensor', which leads in part to resistance to some existing chemo- and radiological treatments. Inhibitors have now been developed which prevent PARP-1 from synthesizing poly(ADP-ribose) in response to DNA-breaks and potentiate the cytotoxicity of DNA damaging agents. However, with the recent discoveries of PARP-2, which has a similar DNA-damage dependent catalytic activity, and additional members containing the 'PARP catalytic' signature, the isoform selectivity and resultant pharmacological effects of existing inhibitors are brought into question. We present here the crystal structure of the catalytic fragment of murine PARP-2, at 2.8 A resolution, and compare this to the catalytic fragment of PARP-1, with an emphasis on providing a possible framework for rational drug design in order to develop future isoform-specific inhibitors
The Brans-Dicke-Rastall theory
We formulate a theory combining the principles of a scalar-tensor gravity and
Rastall's proposal of a violation of the usual conservation laws. We obtain a
scalar-tensor theory with two parameters and , the latter
quantifying the violation of the usual conservation laws. The only exact
spherically symmetric solution is that of Robinson-Bertotti besides
Schwarzschild solution. A PPN analysis reveals that General Relativity results
are reproduced when . The cosmological case displays a possibility
of deceleration/acceleration or acceleration/deceleration transitions during
the matter dominated phase depending on the values of the free parameters.Comment: 17 pages, 3 figure
The Current Ability to Test Theories of Gravity with Black Hole Shadows
Our Galactic Center, Sagittarius A* (Sgr A*), is believed to harbour a
supermassive black hole (BH), as suggested by observations tracking individual
orbiting stars. Upcoming sub-millimetre very-long-baseline-interferometry
(VLBI) images of Sgr A* carried out by the Event-Horizon-Telescope
Collaboration (EHTC) are expected to provide critical evidence for the
existence of this supermassive BH. We assess our present ability to use EHTC
images to determine if they correspond to a Kerr BH as predicted by Einstein's
theory of general relativity (GR) or to a BH in alternative theories of
gravity. To this end, we perform general-relativistic magnetohydrodynamical
(GRMHD) simulations and use general-relativistic radiative transfer (GRRT)
calculations to generate synthetic shadow images of a magnetised accretion flow
onto a Kerr BH. In addition, and for the first time, we perform GRMHD
simulations and GRRT calculations for a dilaton BH, which we take as a
representative solution of an alternative theory of gravity. Adopting the VLBI
configuration from the 2017 EHTC campaign, we find that it could be extremely
difficult to distinguish between BHs from different theories of gravity, thus
highlighting that great caution is needed when interpreting BH images as tests
of GR.Comment: Published in Nature Astronomy on 16.04.18 (including supplementary
information); simulations at https://blackholecam.org/telling_bhs_apart
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