Anti-drift and auto-alignment mechanism for an astigmatic atomic force microscope system based on a digital versatile disk optical head

In this work, an anti-drift and auto-alignment mechanism is applied to an astigmatic detection system (ADS)-based atomic force microscope (AFM) for drift compensation and cantilever alignment. The optical path of the ADS adopts a commercial digital versatile disc (DVD) optical head using the astigmatic focus error signal. The ADS-based astigmatic AFM is lightweight, compact size, low priced, and easy to use. Furthermore, the optical head is capable of measuring sub-atomic displacements of high-frequency AFM probes with a sub-micron laser spot (~570 nm, FWHM) and a high-working bandwidth (80 MHz). Nevertheless, conventional DVD optical heads suffer from signal drift problems. In a previous setup, signal drifts of even thousands of nanometers had been measured. With the anti-drift and auto-alignment mechanism, the signal drift is compensated by actuating a voice coil motor of the DVD optical head. A nearly zero signal drift was achieved. Additional benefits of this mechanism are automatic cantilever alignment and simplified design.     

Long-range transfer of electron-phonon coupling in oxide superlattices

The electron-phonon interaction is of central importance for the electrical and thermal properties of solids, and its influence on superconductivity, colossal magnetoresistance and other many-body phenomena in correlated-electron materials is the subject of intense research at present. However, the non-local nature of the interactions between valence electrons and lattice ions, often compounded by a plethora of vibrational modes, presents formidable challenges for attempts to experimentally control and theoretically describe the physical properties of complex materials. Here we report a Raman scattering study of the lattice dynamics in superlattices of the high-temperature superconductor YBa(2)Cu(3)O(7) (YBCO) and the colossal-magnetoresistance compound La(2/3)Ca(1/3)MnO(3) that suggests a new approach to this problem. We find that a rotational mode of the MnO(6) octahedra in La(2/3)Ca(1/3)MnO(3) experiences pronounced superconductivity-induced line-shape anomalies, which scale linearly with the thickness of the YBCO layers over a remarkably long range of several tens of nanometres. The transfer of the electron-phonon coupling between superlattice layers can be understood as a consequence of long-range Coulomb forces in conjunction with an orbital reconstruction at the interface. The superlattice geometry thus provides new opportunities for controlled modification of the electron-phonon interaction in complex materials.     

Controlled release by permeability alteration of cationic ammonio methacrylate copolymers using ionic interactions

A multiparticulate drug delivery system was studied in which the drug release of a model drug theophylline could be modulated by interactions of ammonio methacrylate polymer and anions. The system consisted of a EUDRAGIT® NE coated anionic core, layered with drug and further layered with EUDRAGIT® RS. The effects of different anions like chloride, succinate, citrate, and acetate as well as the thickness of the polymer layers on the in vitro drug release were studied. It was seen that succinate and acetate anions had permeability enhancing effects and citrate and chloride anions had permeability retarding effects on the polymer. The results indicate that changing these variables would enable us to get a desired release profile and hence the proposed system could be a viable alternative to existing technologies for the development of a controlled drug delivery system.     

Correlation between evolution of resistive switching and oxygen vacancy configuration in La₀.₅Ca₀.₅MnO₃ based memristive devices

We here report a study of the correlation between the evolution of resistive switching and the oxygen vacancy configuration in La?.?Ca?.?MnO? (LCMO) based memristive devices. By taking advantage of LCMO located at a phase boundary of the metal-to-insulator transition, we observe the development of the high resistive states, depending upon not only the electrical pulse magnitude but also the switching cycles. We discuss the experimental results by an oxygen migration model that involves both single isolated and clustered oxygen vacancies, which are later verified using aberration-corrected scanning transmission electron microscopy.