2,690 research outputs found
Feasibility study of geospatial mapping of chronic disease risk to inform public health commissioning
No full textThis final article is available for use under the terms of the Creative Commons Attribution Non-Commercial 2.0 Licence; see http://bmjopen.bmj.co
Nanoscale magnetoelectric effects revealed by imaging
No full textWe review our work on continuous Ni films coupled via strain to ferroelectric substrates of BaTiO3 (BTO) and 0.68Pb(Mg1/3Nb2/3)O3–0.32PbTiO3 (PMN-PT). We show that magnetic force microscopy (MFM) and photoemission electron microscopy (PEEM) of the Ni films (during or after electrical treatment) permit to reveal nanoscale converse magnetoelectric effects (CMEs) that are novel and elude macroscopic measurements. As examples, we discuss magnetization reversal without applied field in multilayer capacitors (MLCs), shear-strain-mediated CMEs in thin Ni films on PMN-PT and reversible switching of perpendicular magnetization from out-of-plane to in-plane in Ni films on BTO. In this latter case, we show that PEEM can be used to measure both magnetic and ferroelectric domains, thus providing key mechanistic insight in the magnetoelectric coupling mechanism
Low-temperature transverse magnetic domains in nominally uniaxial La0.67Sr0.33MnO3 films on NdGaO3 (0 0 1)
No full textBogoliubov coefficients for the twist operator in the D1D5 CFT
No full textAbstractThe D1D5 CFT is a holographic dual of a near-extremal black hole in string theory. The interaction in this theory involves a twist operator which joins together different copies of a free CFT. Given a large number of D1 and D5 branes, the effective length of the circle on which the CFT lives is very large. We develop a technique to study the effect of the twist operator in the limit where the wavelengths of excitations are short compared to this effective length, which we call the ‘continuum limit’. The method uses Bogoliubov coefficients to compute the effect of the twist operator in this limit. For bosonic fields, we use the method to reproduce recent results describing the effect of the twist operator when it links together CFT copies with windings M and N, producing a copy of winding M+N. We also comment on possible generalizations of our results. The methods developed here may help in understanding the twist interaction at higher orders. This in turn should provide insight into the thermalization process in the D1D5 CFT, which gives a holographic description of black hole formation
Oxidative dealkylation of a hindered phenol catalyzed by copper (II) bis benzimidazole diamide complex
No full textThe oxidative dealkylation of 2,4,6-tri-tert-butylphenol (TTBP) has been investigated using molecular oxygen and Cu(NO3(GBHA)(NO3) as catalyst, where GBHA is N,N′-bis((benzimidazol-2-yl)methyl)hexanediamide (a) M. Gupta, P. Mathur, R.J. Butcher, Inorg. Chem. 40 (2001) 878; (b) M. Gupta, S.K. Das, P. Mathur, A.W. Cordes, Inorg. Chim. Acta 353 (2003) 197; (c) S. Tehlan, M.S. Hundal, P. Mathur, Inorg. Chem. 43 (2004) 6589; (d) F. Afreen, P. Mathur, A. Rheingold, Inorg. Chim. Acta 358 (2005) 1125.. X-ray structural characterization of complex Cu(NO3)(GBHA)(NO3)·CH3OH confirms that the Cu (II) ion is in a distorted square pyramidal geometry (τ=0.168). The TTBP oxidation reaction proceeds via tri-tert-butylphenoxyl radical producing two products 2,6-di-tert-butyl-1,4-benzoquinone (A) and 4,6-di-tert-butyl-1,2-benzoquinone (B). Both A and B have been well characterized by 1H NMR, 13C NMR, UV–Vis and mass data
An Analytical Criterion for Centrifugal Instability in Non-Axisymmetric Vortices
No full textNon-axisymmetric vortices are ubiquitous in nature; examples include polar vortices in planets, the giant red spot in Jupiter, tornadoes and cyclones on Earth, mesoscale eddies in the ocean. Turbulent flows are furthermore known to be dominated by small- and large-scale vortex structures. Owing to the wide range of applications, knowledge of conditions under which a given vortex becomes unstable is beneficial. Here, the centrifugal instability of two-dimensional, non-axisymmetric vortices in the presence of an axial flow and a background rotation is studied using the local stability approach. The local stability approach, based on geometric optics and similar in formulation to the rapid distortion theory \cite{bib:godeferd2001}, considers the evolution of shortwavelength perturbations along streamlines in the base flow. This approach, developed by Lifschitz Hameiri \cite{bib:lifschitz1991}, is particularly useful for base flows for which a global stability analysis is computationally expensive. A sufficient criterion for centrifugal instability in an axisymmetric vortex with and is first derived by analytically solving the local stability equations for wave vectors that are periodic upon evolution around a closed streamline. This criterion is then heuristically extended to non-axisymmetric vortices and written in terms of integral quantities on a streamline. The criterion is then shown to be accurate in describing centrifugal instability over a reasonably large range of parameters that specify Stuart vortices and Taylor-Green vortices
Non-volatile voltage control of in-plane and out-of-plane magnetization in polycrystalline Ni films on ferroelectric PMN-PT (001)pcsubstrates
No full textWe identify room-temperature converse magnetoelectric effects (CMEs) that are non-volatile by using a single-crystal substrate of PMN-PT (001)pc (pc denotes pseudocubic) to impart voltage-driven strain to a polycrystalline film of Ni. An appropriate magnetic-field history enhances the magnetoelectric coefficient to a near-record peak of ∼10-6 s m-1 and permits electrically driven magnetization reversal of substantial net magnetization. In zero magnetic field, electrically driven ferroelectric domain switching produces large changes of in-plane magnetization that are non-volatile. Microscopically, these changes are accompanied by the creation and destruction of magnetic stripe domains, implying the electrical control of perpendicular magnetic anisotropy. Moreover, the stripe direction can be rotated by a magnetic field or an electric field, the latter yielding the first example of electrically driven rotatable magnetic anisotropy. The observed CMEs are associated with repeatable ferroelectric domain switching that yields a memory effect. This memory effect is well known for PMN-PT (110)pc but not PMN-PT (001)pc. Given that close control of the applied field is not required as for PMN-PT (110)pc, this memory effect could lead the way to magnetoelectric memories based on PMN-PT (001)pc membranes that switch at low voltage
Effect of the twist operator in the D1D5 CFT
No full textThe D1D5 CFT has been very useful in the study of black holes. The interaction in this theory involves a twist operator, which links together different copies of a free CFT. For the bosonic fields, we examine the action of this twist when it links together CFT copies with winding numbers M and N to produce a copy with winding M+N. Starting with the vacuum state generates a squeezed state, which we compute. Starting with an initial excitation on one of the copies gives a linear combination of excitations on the final state, which we also compute. These results generalize earlier computations where these quantities were computed for the special case M=N=1. Our results should help in understanding the thermalization process in the D1D5 CFT, which gives the dual of black hole formation in the bulk
Economic analysis of the coal mining industry: With some empirical explorations in the behavior of costs and input-output relations
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