Coercive field behavior of permalloy antidot arrays based on self-assembled template fabrication

High-density magnetic antidot arrays have been fabricated by deposition of Fe₂₀Ni₈₀ thin films on self-assembled nanoporous alumina membranes (NAM) with high-order hexagonal symmetry. The magnetic properties induced by the size and the geometry configuration of the holes introduced in a Fe₂₀Ni₈₀ thin film are discussed based on hysteresis loops measured as a function of temperature. The precursor NAMs have pore diameters ranging between 35 and 95 nm (55 and 75 nm after the film deposition) and a lattice parameter of 105 nm. An enormous increase of coercitivity, as compared with the corresponding continuous films, was observed for temperatures between 2 and 300 K. This effect depends on the size and surface density of holes in the Fe₂₀Ni₈₀ antidot arrays. Rutherford backscattering spectrometry (RBS) measurements were performed in order to better clarify the magnetic material that was eventually deposited within the NAM pores.     

Multi-magnetic phases in Fe1−xNixTa2O6

X-ray, neutron diffraction and magnetic susceptibility are reported for Fe_xNi_1−xTa₂O₆ mixed oxides. X-ray refinement indicates homogeneous samples for all the reported concentrations. The neutron-diffraction measurements reveal magnetic structures with double propagation vectors. This system exhibits at least two bicritical points at about x=0.15 and 0.60. For these concentrations, at low temperatures, the system shows the coexistence of two magnetic structures. This bicritical behaviour is interpreted as induced by competition between the different magnetic structures.     

Electronic compressibility of a graphene bilayer

We calculate the electronic compressibility arising from electron-electron interactions for a graphene bilayer within the Hartree-Fock approximation. We show that, due to the chiral nature of the particles in this system, the compressibility is rather different from those of either the two-dimensional electron gas or ordinary semiconductors. We find that an inherent competition between the contributions coming from intraband exchange interactions (dominant at low densities) and interband interactions (dominant at moderate densities) leads to a nonmonotonic behavior of the compressibility as a function of carrier density.     

Enhancement of abdominal organs on hepatic arterial phase: quantitative comparison between 1.5- and 3.0-T magnetic resonance imaging

Purpose

To compare the extent of enhancement of abdominal organs as shown on subphases of hepatic arterial phase quantitatively between 1.5- and 3.0-T MRI among patients with various abdominal conditions.

Materials and Methods

A total of 126 patients, of whom 68 were women (age range, 3–82 years; mean age, 48 years) and 58 were men (age range, 6–73 years; mean age, 50 years), were included in the study. Of 126 patients, 98 were scanned at 1.5 T and 28 were scanned at 3.0 T. The presence of one of three predefined subphases of hepatic arterial phase was determined on early post-gadolinium sequence in each patient by two reviewers in consensus. Extent of enhancement of the kidney, pancreas, spleen and liver on these subphases was determined quantitatively by measuring the signal intensities. Mann Whitney–Wilcoxon test was used to compare the contrast enhancement of organs on each subphase between 1.5- and 3.0-T MRI.

Results

The kidney, spleen, pancreas and liver demonstrated 1.79- to 2.45-, 1.65- to 1.97-, 1.66- to 1.8- and 1.1- to 2.02-fold higher enhancement on the subphases of hepatic arterial phase at 3.0 T compared to 1.5 T, respectively. The differences in contrast enhancement were significant for the kidney, pancreas and spleen on all subphases between 1.5 and 3.0 T.

Conclusion

The relative enhancement of the kidney, spleen and pancreas is consistently and significantly higher at 3.0 T than at 1.5 T in matched subphases of hepatic arterial enhancement.     

Energy‐dispersive X‐ray absorption spectroscopy at LNLS: investigation on strongly correlated metal oxides

An energy‐dispersive X‐ray absorption spectroscopy beamline mainly dedicated to X‐ray magnetic circular dichroism (XMCD) and material science under extreme conditions has been implemented in a bending‐magnet port at the Brazilian Synchrotron Light Laboratory. Here the beamline technical characteristics are described, including the most important aspects of the mechanics, optical elements and detection set‐up. The beamline performance is then illustrated through two case studies on strongly correlated transition metal oxides: an XMCD insight into the modifications of the magnetic properties of Cr‐doped manganites and the structural deformation in nickel perovskites under high applied pressure.     

TeV‐ and MeV‐Physics Out of an Model

The standard electroweak interaction is here re‐assessed to accommodate two different situations in Particle Physics. The first one is a ‐model at the TeV‐scale physics. The second one tackles the recent discussion of a possible fifth force mediated by a 17‐MeV X‐boson associated with an electron‐positron emission in the transition of an excited 8‐Beryllium to its ground state. The anomaly‐free model that provides these two scenarios is based on an ‐symmetry. It yields a new massive neutral boson, an exotic massive neutral fermion, right‐neutrinos and an additional neutral Higgs particle, which stems from a supplementary Higgs field, introduced along with the usual Higgs doublet responsible for the electroweak breaking and the masses of and Z⁰. Yukawa interactions of the two scalars generate the masses of the Standard Model leptons, neutrinos and a new exotic fermion of the model. The vacuum expectation values of the Higgses fix up two independent energy scales. One of them is the well‐confirmed electroweak scale, 246 GeV, whereas the other one is set up by adopting an experimental estimate for the ‐mass.     

Theory of Gravity in Fierz Variables (The Linear Case)

We present a complete theory of massive and massless spin-two field using Fierz variables A_αβμ for flat and curved space-times; its relationship with the standard variable Ψ_μν and the bridge relation which allows the passage from one representation to the other. The theory presented is nothing but the weak approximation of Einstein's General Relativity in the Jordan-Lichnerowicz formulation.