Waveguides in KNbO3 by He implantation

In a KNbO₃ single domain substrate crystal a permanent multimode waveguide has been produced for the first time by implantation of 2 MeV He⁺ ions. Annealing is unnecessary since electronic damage is small. The irradiation flux was controlled such that no unwanted phase transitions or domain formation occured. The refractive index profile was investigated by dark line mode spectroscopy and reconstructed by a new inverse WKB procedure. The waveguiding layer has a thickness of about 3 μm, in the region directly below this layer the refractive index is decreased by more than 0.1.     

Surface channeling experiments on Pb(110)

Low energy ion scattering techniques at 2 keV with Ne⁴ are used to study the surface structure of Pb (110) around 400 K. Surface channeling reveals a phase transition at this temperature. Surface blocking shows that the surface phase transition is of the roughening type.     

Sputtering of adsorbed layers by ion bombardment

Sputtering of adsorbed species by particle bombardment is a major source of contamination in present-day thermonuclear devices. Nevertheless, there have been very few systematic studies of the sputtering processes which produce this contamination. These questions were investigated, both experimentally and numerically, for systems with various projectile and target mass ratios. We studied the sputtering of S and O from Ni (111) and Ni (110) surfaces by Ar⁺, Ne⁺ and He⁺ ions between 100 and 1600 eV. The sputtering cross-sections increase with ion mass and energy from 10^?16 to 10^?14 cm² for S in the observed range of parameters and are lower for oxygen. There is a maximum for an impact angle of about 30° relative to the surface. These results are generally confirmed by numerical studies with a modification of the computer program MARLOWE. Also the influence of various parameters, such as surface binding energy, surface geometry, impact angle, etc. will be discussed. The theoretical estimates of Winters and Sigmund are applied to the system under investigation. These calculations yield the right order of magnitude for the sputtering cross-sections. According to these results the main contributions to sputtering are from direct knock-off effects and from backscattered primaries, with a smaller contribution arising from the sputtering of the base material.     

Principles of low energy ion scattering

Elastic and inelastic processes occurring in ion-solid interactions are discussed together with adsorption and desorption by low energy ion beams.     

Improved compressed sensing reconstruction for $$^{19}$$ F magnetic resonance imaging

Magnetic Resonance Materials in Physics, Biology and Medicine - In magnetic resonance imaging (MRI), compressed sensing (CS) enables the reconstruction of undersampled sparse data sets. Thus,...     

Increased in vitro Anti-HIV Activity of Caffeinium-Functionalized Polyoxometalates

Polyoxometalates (POMs), molecular metal oxide anions, are inorganic clusters with promising antiviral activity. Herein we report increased anti-HIV-1 activity of a POM when electrostatically combined with organic counter-cations. To this end, Keggin-type cerium tungstate POMs have been combined with organic methyl-caffeinium (Caf) cations, and their cytotoxicity, antiviral activity and mode of action have been studied. The novel compound, Caf₄K[β₂-CeSiW₁₁O₃₉]×H₂O, exhibits sub-nanomolar antiviral activity and inhibits HIV-1 infectivity by acting on an early step of the viral infection cycle. This work demonstrates that combination of POM anions and organic bioactive cations can be a powerful new strategy to increase antiviral activity of these inorganic compounds.