2,382 research outputs found
Non-local control in the conduction coefficients: well posedness and convergence to the local limit
We consider a problem of optimal distribution of conductivities in a system
governed by a non-local diffusion law. The problem stems from applications in
optimal design and more specifically topology optimization. We propose a novel
parametrization of non-local material properties. With this parametrization the
non-local diffusion law in the limit of vanishing non-local interaction
horizons converges to the famous and ubiquitously used generalized Laplacian
with SIMP (Solid Isotropic Material with Penalization) material model. The
optimal control problem for the limiting local model is typically ill-posed and
does not attain its infimum without additional regularization. Surprisingly,
its non-local counterpart attains its global minima in many practical
situations, as we demonstrate in this work. In spite of this qualitatively
different behaviour, we are able to partially characterize the relationship
between the non-local and the local optimal control problems. We also
complement our theoretical findings with numerical examples, which illustrate
the viability of our approach to optimal design practitioners
Quantum diffusion beyond slow-roll: implications for primordial black-hole production
Primordial black-holes (PBH) can be produced in single-field models of
inflation with a quasi-inflection point in the potential. In these models, a
large production of PBHs requires a deviation from the slow-roll (SR)
trajectory. In turn, this SR violation can produce an exponential growth of
quantum fluctuations. We study the back-reaction of these quantum modes on the
inflationary dynamics using stochastic inflation in the Hamilton-Jacobi
formalism. We develop a methodology to solve quantum diffusion beyond SR in
terms of the statistical moments of the probability distribution. We apply
these techniques to a toy model potential with a quasi-inflection point. We
find that there is an enhancement of the power spectrum due to the dominance of
the stochastic noise in the phase beyond SR. Moreover, non-Gaussian corrections
become as well relevant with a large positive kurtosis. Altogether, this
produces a significant boost of PBH production. We discuss how our results
extend to other single-field models with similar dynamics. We conclude that the
abundance of PBHs in this class of models should be revisited including quantum
diffusion.Comment: 17+7 pages, 5 figures. Matches JCAP versio
Experimenting with Law: Brecht on Copyright
Can one reject copyright law and be a qualified observer of its dispositives? This question was taken up by Bertolt Brecht in an intriguing essay concerning the litigation surrounding the film adaptation of The Threepenny Opera (1928). Brecht here develops an experimental observation around the nature of film adaptation and cultural production in copyright. While an experimental approach to law was in itself a subversive gesture, the specific legal process enabled him to expose the paradoxical ways in which the copyright system worked
Towards the most general scalar-tensor theories of gravity: a unified approach in the language of differential forms
We use a description based on differential forms to systematically explore
the space of scalar-tensor theories of gravity. Within this formalism, we
propose a basis for the scalar sector at the lowest order in derivatives of the
field and in any number of dimensions. This minimal basis is used to construct
a finite and closed set of Lagrangians describing general scalar-tensor
theories invariant under Local Lorentz Transformations in a pseudo-Riemannian
manifold, which contains ten physically distinct elements in four spacetime
dimensions. Subsequently, we compute their corresponding equations of motion
and find which combinations are at most second order in derivatives in four as
well as arbitrary number of dimensions. By studying the possible exact forms
(total derivatives) and algebraic relations between the basis components, we
discover that there are only four Lagrangian combinations producing second
order equations, which can be associated with Horndeski's theory. In this
process, we identify a new second order Lagrangian, named kinetic Gauss-Bonnet,
that was not previously considered in the literature. However, we show that its
dynamics is already contained in Horndeski's theory. Finally, we provide a full
classification of the relations between different second order theories. This
allows us to clarify, for instance, the connection between different
covariantizations of Galileons theory. In conclusion, our formulation affords
great computational simplicity with a systematic structure. As a first step we
focus on theories with second order equations of motion. However, this new
formalism aims to facilitate advances towards unveiling the most general
scalar-tensor theories.Comment: 28 pages, 1 figure, version published in PRD (minor changes
Flipped classroom based on objective structured clinical examinations analysis by undergraduate students of Pharmacology course from the Podiatry Degree improve their learning and assessment communication skills about medicines
ComunicaciĂłn cartel con defensa oralWe aim to evaluate the impact of the individual and in-group analysis of OSCEs (filmed by other students) looking for correct and incorrect behaviours and contents in their learning of pharmacology.
Summary of work and outcomes: A 5-year prospective study in which students of Pharmacology course from the Podiatry Degree analysed filmed OSCEs individually and in a group in a flipped classroom. Each group (max 5 students) analysed along 1 week a filmed OSCE, prepare a summary of correct and incorrect items related to clinical events, medicines uses, and people behaviours. The students presented their analysis results to the rest of the class. After each presentation, the other students of the class were encouraged to ask questions and after that, the students voluntarily answered a satisfaction survey.
Result and Discussion: 405 students, 65.2% female, 20±5.3 years old were included. Students spend 13.4±5.4 h on making the filmed-OSCE analysis. The percentage of students satisfied with this way of studying pharmacology was 96.5%. OSCEs analysis by students increased their percentage of success in the final assessment in both OSCEs-related and OSCEs-non-related questions (+18.5% and +10.1%).
Conclusion: Filmed Objective Structured Clinical Examinations analysis by undergraduate students on the Pharmacology course of Podiatry Degree improved their knowledge about medicines use and their communication skills during the assessment.Universidad de Málaga. Campus de Excelencia Internacional AndalucĂa Tech
Solar neutrino detection
More than 40 years ago, neutrinos where conceived as a way to test the
validity of the solar models which tell us that stars are powered by nuclear
fusion reactions. The first measurement of the neutrino flux, in 1968 in the
Homestake mine in South Dakota, detected only one third of the expected value,
originating what has been known as the Solar Neutrino Problem. Different
experiments were built in order to understand the origin of this discrepancy.
Now we know that neutrinos undergo oscillation phenomenon changing their nature
traveling from the core of the Sun to our detectors. In the work the 40 year
long saga of the neutrino detection is presented; from the first proposals to
test the solar models to last real time measurements of the low energy part of
the neutrino spectrum.Comment: 8 pages, 5 figures. III School on Cosmic Rays and Astrophysics August
25 to September 5, 2008 Arequipa (Peru) AIP conference proceedin
Postoperative pain and morphine consumption after ultrasound-guided femoral and sciatic combined nerve block versus neurostimulation for femoral and sciatic combined nerve block or neurostimulation for femoral nerve block in primary elective total knee arthroplasty.
Abstract Congreso XXXVII National Meeting of the Spanish Society of Pharmacology with guest society: The British Pharmacological SocietyBackground and Aims:
Total knee arthroplasty injuries are extremely painful and merit prompt attention to adequate postoperative analgesia. We aim to compare femoral and sciatic ultrasound-guided combined nerve block vs. neurostimulation for femoral and sciatic combined nerve block or for femoral nerve block in postoperative pain in primary elective total knee prosthesis.
Summary of work and outcomes:
A three arms, prospective longitudinal study of patients having primary elective unilateral knee prosthesis and randomly assigned to catheter insertion guided by ultrasound or neurostimulation was done: 1) Ultrasound-guided femoral and sciatic combined nerve block (USFSCN) (N=15); 2) Neurostimulation for femoral and sciatic combined nerve block (NSFSCN) (N=17); 3) Neurostimulation for femoral nerve block (NSFN) (N=11). Total analgesia (morphine) consumption after 48 hours was the primary endpoint. The postoperative pain intensity (visual analogue pain scale (VAS)) at post-anaesthetic recovery unit (PARU), 6, 24, 48 h, and during movement and postoperative complications were secondary outcomes.
Results and discussion:
43 patients (68.3±8 years old, 77% female) subjected to elective unilateral knee prosthesis were enrolled. There were no differences in the demographic, anaesthetic and surgical variables between groups. Pain intensity was lower in the USFSCN group compared with NSFSCN and NSFN during the first 48 h post-surgery (% of intense pain at PARU/6h/24h/48h): USFSCN 0.8/1.4/3.2/1.6; NSFSCN 5.6/8.3/7.5/3; NSFN 7.2/5.3/6.4/5.4. The average consumption of morphine within 48 h after surgery was similar in the groups USFSCN and NSFSCN (3 mg vs. 3.11 mg), and significantly lower than NSFN (4.19 mg) (p<0.05). And the number of complications was significantly lower in the USFSCN group compared with NSFSCN and NSFN during the first 48 h of postoperative.
Conclusion:
Ultrasound-guided femoral and sciatic combined nerve block presented better analgesia and was more safety than neurostimulation for femoral and sciatic combined nerve block or for femoral nerve block in primary elective total knee arthroplasty.Universidad de Málaga. Campus de Excelencia Internacional AndalucĂa Tech
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