Atomic resolution mapping of phonon excitations in STEM-EELS experiments

Atomically resolved electron energy-loss spectroscopy experiments are commonplace in modern aberrationcorrected transmission electron microscopes. Energy resolution has also been increasing steadily with the continuous improvement of electron monochromators. Electronic excitations however are known to be delocalised due to the long range interaction of the charged accelerated electrons with the electrons in a sample. This has made several scientists question the value of combined high spatial and energy resolution for mapping interband transitions and possibly phonon excitation in crystals. In this paper we demonstrate experimentally that atomic resolution information is indeed available at very low energy losses around 100 meV expressed as a modulation of the broadening of the zero loss peak. Careful data analysis allows us to get a glimpse of what are likely phonon excitations with both an energy loss and gain part. These experiments confirm recent theoretical predictions on the strong localisation of phonon excitations as opposed to electronic excitations and show that a combination of atomic resolution and recent developments in increased energy resolution will offer great benefit for mapping phonon modes in real space

The “Jokari sign”, an imaging feature diagnostic of a wandering accessory spleen

If cross-sectional imaging techniques often disclose the presence of an accessory spleen, they seldom detect a wandering accessory spleen. This latter diagnosis can be challenging but important and derives great benefit from computed tomography with curved multiplanar and three-dimensional reconstructions displaying the long vascular pedicle connecting the small mass to the splenic vessels. We call this anatomical complex the “Jokari sign”, in reference to the ball-on-a-string racket game

Controlling the interfacial conductance in LaAlO₃/SrTiO₃ in 90∘ off-axis sputter deposition

We report on the fabrication of conducting interfaces between LaAlO 3 and SrTiO 3 by 90 ∘ off-axis sputtering in an Ar atmosphere. At a growth pressure of 0.04 mbar the interface is metallic, with a carrier density of the order of 1 × 10 13 cm − 2 at 3 K. By increasing the growth pressure, we observe an increase of the out-of-plane lattice constants of the LaAlO 3 films while the in-plane lattice constants do not change. Also, the low-temperature sheet resistance increases with increasing growth pressure, leading to an insulating interface when the growth pressure reaches 0.10 mbar. We attribute the structural variations to an increase of the La/Al ratio, which also explains the transition from metallic behavior to insulating behavior of the interfaces. Our research shows that the control which is furnished by the Ar pressure makes sputtering as versatile a process as pulsed laser deposition, and emphasizes the key role of the cation stoichiometry of LaAlO 3 in the formation of the conducting interface

Inhomogeneous superconductivity and quasilinear magnetoresistance at amorphous LaTiO3/SrTiO3 interfaces

We have studied the transport properties of LaTiO3/SrTiO3 (LTO/STO) heterostructures. In spite of 2D growth observed in reflection high energy electron diffraction, Transmission Electron Microscopy images revealed that the samples tend to amorphize. Still, we observe that the structures are conducting, and some of them exhibit high conductance and/or superconductivity. We established that conductivity arises mainly on the STO side of the interface, and shows all the signs of the 2-dimensional electron gas usually observed at interfaces between SrTiO3 and LaTiO3 or LaAlO3, including the presence of two electron bands and tunability with a gate voltage. Analysis of magnetoresistance (MR) and superconductivity indicates presence of a spatial fluctuations of the electronic properties in our samples. That can explain the observed quasilinear out-of-plane MR, as well as various features of the in-plane MR and the observed superconductivity.Comment: 10 pages, 6 figures, plus Supplementary Informatio

The 0 and the pi phase Josephson coupling through an insulating barrier with magnetic impurities

We have studied temperature and field dependencies of the critical current $I_{C}$ in the Nb-Fe$_{0.1}$Si$_{0.9}$-Nb Josephson junction with tunneling barrier formed by paramagnetic insulator. We demonstrate that in these junctions the co-existence of both the 0 and the $\pi$ states within one tunnel junction takes place which leads to the appearance of a sharp cusp in the temperature dependence $I_{C}(T)$ similar to the $I_{C}(T)$ cusp found for the $0-\pi$ transition in metallic $\pi$ junctions. This cusp is not related to the $0-\pi$ temperature induced transition itself, but is caused by the different temperature dependencies of the opposing 0 and $\pi$ supercurrents through the barrier.Comment: Accepted in Physical Review

Primary aortic thrombosis: role of enhanced multislice CT demonstrated in three exceptional cases.

Primary aortic thrombosis remains a rare entity that can be defined as clotting of the vessel without any obvious atheromatous lesion. Cancer chemotherapy, cocaine intake, essential thrombocythemia, some hypercoagulable states, heparin-induced thrombocytopenia, inflammatory disease of the digestive tract and acute pancreatitis are, beside some cases of rather unknown etiology, the causes of primary aortic thrombosis. Intravenous contrast-enhanced multislice CT, which is widely available, noninvasive and affordable in terms of cost, is the imaging modality of choice for the investigation of primary aortic thrombosis and the assessment of potential complications. Three cases due to chemotherapy, antiphospholipid syndrome and acute pancreatitis are reported

Dialysis arteriovenous fistulas: the critical role of color doppler ultrasound

Despite being time-consuming and observer-dependent, CDUS is a method of choice for performing and controlling dialysis shunts. It contributes to increasing the number of native AVFs and enables early detection of lesions therefore allowing quick percutaneous or surgical therapy