1,247 research outputs found
Bouncing cosmology in f(Q) symmetric teleparallel gravity
No full textWe consider f(Q) extended symmetric teleparallel cosmologies, where Q is the non-metricity scalar, and constrain its functional form through the order reduction method. By using this technique, we are able to reduce and integrate the field equations and thus to select the corresponding models giving rise to bouncing cosmology. The selected Lagrangian is then used to develop the Hamiltonian formalism and to obtain the Wave Function of the Universe which suggests that classical observable universes can be recovered according to the Hartle Criterion
Cerebrovascular assessment for the risk prediction of Alzheimer’s disease.
No full textCerebrovascular Assessment for the Risk Prediction of Alzheimer's Disease.
Silvestrini M, Viticchi G, Altamura C, Luzzi S, Balucani C, Vernieri F.
Neurological Clinic, Marche Polytechnic University, Ancona, Italy.
Increasing evidence is emerging that vascular disease and its risk factors play a
role in the development of Alzheimer's disease (AD) and affect the probability of
an adverse outcome. The aims of this review are to explore the relationship
between vascular risk factors and AD and to discuss the potential use of vascular
markers in the clinical approach to cognitive impairment. Moreover, we present
evidence about the potential use of ultrasonographic and neuroradiologic markers
of cognitive impairment in order to establish possible treatment strategies in
subjects with a clinical profile at risk of developing AD
Equivalence between Palatini and metric formalisms of f(R)-gravity by divergence free current
No full textThe equivalence between metric and Palatini formalisms in f(R)-gravity can be achieved in the general context of theories with divergence-free current. This equivalence is a necessary result of a symmetry which is included in a particular conservation equation of the current. In fact the conservation equation, by an appropriate redefinition of the introduced auxiliary field, may be encoded in a massless scalar field equation. © 2011 World Scientific Publishing Company
New spherically symmetric solutions in f (R)-gravity by Noether symmetries
No full textSpherical symmetry for f (R)-gravity is discussed by searching for Noether symmetries. The method consists in selecting conserved quantities in form of currents that reduce dynamics of f (R)-models compatible with symmetries. In this way we get a general method to obtain constants of motion without setting a priori the form of f (R). In this sense, the Noether symmetry results a physical criterium. Relevant cases are discussed
fMRI-vs-MEG evaluation of post-stroke interhemispheric asymmetries in primary sensorimotor hand areas
No full textGrowing evidence emphasizes a positive role of brain ipsilesional (IL) reorganization in stroke patients with partial recovery. Ten patients affected by a monohemispheric stroke in the middle cerebral artery territory underwent functional magnetic resonance (fMRI) and magnetoencephalography (MEG) evaluation of the primary sensory (S1) activation via the same paradigm (median nerve galvanic stimulation). Four patients did not present S1 fMRI activation [Rossini, P.M., Altamura, C., Ferretti, A., Vernieri, F., Zappasodi, F., Caulo, M., Pizzella, V., Del Gratta, C., Romani, G.L., Tecchio, F., 2004. Does cerebrovascular disease affect the coupling between neuronal activity and local haemodynamics? Brain 127, 99-110], although inclusion criteria required bilateral identifiable MEG responses. Mean Euclidean distance between fMRI and MEG S1 activation Talairach coordinates was 10.1 ± 2.9 mm, with a 3D intra-class correlation (ICC) coefficient of 0.986. Interhemispheric asymmetries, evaluated by an MEG procedure independent of Talairach transformation, were outside or at the boundaries of reference ranges in 6 patients. In 3 of them, the IL activation presented medial or lateral shift with respect to the omega-shaped post-rolandic area while in the other 3, IL areas were outside the peri-rolandic region. In conclusion, despite dissociated intensity, the MEG and fMRI activations displayed good spatial consistency in stroke patients, thus confirming excessive interhemispheric asymmetries as a suitable indicator of unusual recruitments in the ipsilesional hemisphere, within or outside the peri-rolandic region. © 2006 Elsevier Inc. All rights reserved
Correspondence between Jordan-Einstein frames and Palatini-metric formalisms
No full text We discuss the conformal symmetry between Jordan and Einstein frames considering their relations with the metric and Palatini formalisms for modified gravity. Appropriate conformal transformations are taken into account leading to the evident connection between the gravitational actions in the two mentioned frames and the Hilbert–Einstein action with a cosmological constant. We show that the apparent differences between Palatini and metric formalisms strictly depend on the representation while the number of degrees of freedom is preserved. This means that the dynamical content of both formalism is identical. </jats:p
The involvement of ABA in ameliorating plant water status of bean seedlings under chilling conditions
No full textEffetti del paclobutrazolo (PP-333) sull'accrescimento in vivaio e sulla resistenza al freddo di piantine di pomodoro
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