Structural incommensurate modulation rule in hexagonal Ba(Ti1-xMx)O3-δ (M = Mn, Fe) multiferroics AIP Advances 2, 042129 (2012) Water assisted gate induced temporal surface charge distribution probed by electrostatic force microscopy J. Appl. Phys. 112, 084329 (2012) Influence of target composition and deposition temperature on the domain structure of BiFeO3 thin films AIP Advances 2, 042104 (2012) Nanodomain structures formation during polarization reversal in uniform electric field in strontium barium niobate single crystals J. Appl. Phys. 112, 064117 (2012) The effect of the top electrode interface on the hysteretic behavior of epitaxial ferroelectric Pb(Zr,Ti)O3 thin films with bottom SrRuO3 electrode J. Appl. Phys. 112, 064116 (2012) Additional information on J. Appl. Phys. Structural and electrical evidence for a ferroelectric phase in yttrium doped hafnium oxide thin films is presented. A doping series ranging from 2.3 to 12.3 mol% YO 1.5 in HfO 2 was deposited by a thermal atomic layer deposition process. Grazing incidence X-ray diffraction of the 10 nm thick films revealed an orthorhombic phase close to the stability region of the cubic phase. The potential ferroelectricity of this orthorhombic phase was confirmed by polarization hysteresis measurements on titanium nitride based metal-insulator-metal capacitors. For 5.2 mol% YO 1.5 admixture the remanent polarization peaked at 24 lC=cm 2 with a coercive field of about 1.2 MV=cm. Considering the availability of conformal deposition processes and CMOS-compatibility, ferroelectric Y:HfO 2 implies high scaling potential for future, ferroelectric memories.

A mock heart circulation loop (MHCL) is a hydraulic model simulating the human circulatory system. It allows in vitro investigations of the interaction between cardiac assist devices and the human circulatory system. In this study, a preload sensitive MHCL, the MHCL , was developed to investigate the interaction between the left ventricle and left ventricular assist devices (LVADs). The Frank-Starling mechanism was modeled by regulating the stroke volume (SV) based on the measured mean diastolic left atrial pressure (MLAP ). The baroreflex autoregulation mechanism was implemented to maintain a constant mean aortic pressure (MAP) by varying ventricular contractility (E ), heart rate (HR), afterload/systemic vascular resistance (SVR) and unstressed venous volume (UVV). The DP3 blood pump (Medos Medizintechnik GmbH) was used to simulate the LVAD. Characteristic parameters were measured in pathological conditions both with and without LVAD to assess the hemodynamic effect of LVAD on the MHCL . The results obtained from the MHCL show a high correlation to literature data. The study demonstrates the possibility of using the MHCL as a research tool to better understand the physiological interactions between cardiac implants and human circulation.

Mock heart circulation loops (MHCLs) serve as in-vitro platforms to investigate the physiological interaction between circulatory systems and cardiovascular devices. A mock heart (MH) engineered with silicone walls and helical aramid fibers, to mimic the complex contraction of a natural heart, has been developed to advance the MHCL previously developed in our group. A mock aorta with an anatomical shape enables the evaluation of a cannulation method for ventricular assist devices (VADs) and investigation of the usage of clinical measurement systems like pressure-volume catheters. Ventricle and aorta molds were produced based on MRI data and cast with silicone. Aramid fibers were layered in the silicone ventricle to reproduce ventricle torsion. A rotating hollow shaft was connected to the apex enabling the rotation of the MH and the connection of a VAD. Silicone wall thickness, aramid fiber angle and fiber pitch were varied to generate different MH models. All MH models were placed in a tank filled with variable amounts of water and air simulating the compliance. In this work, physiological ventricular torsion angles (15°-26°) and physiological pressure-volume loops were achieved. This MHCL can serve as a comprehensive testing platform for cardiovascular devices, such as artificial heart valves and cannulation of VADs.

Spatially resolved measurement of blood flow is of great interest in the development of artificial blood-carrying devices such as blood pumps, heart valve prostheses, and oxygenators. Particle image velocimetry (PIV) is able to measure instantaneous velocity fields in a plane with high accuracy and is being used more frequently for the development of such devices. However, as this measurement technique is based on optical access, blood flow at physiological hematocrit values is difficult to measure due to its low transparency and multiscattering properties. So far, only very small dimensions (in the range of 400 μm) can be measured using PIV. A suspension of ghost cells (GCs) offers a higher optical transparency than blood while having a similar rheological behavior. In this study, a procedure for the production of GC suspensions containing a very low intracellular hemoglobin concentration is presented. With the help of multiple rounds of controlled cell lysis, the intracellular hemoglobin concentration could be decreased to a point where a standard macroscopic PIV measurement was possible. A velocity profile of a 44% GC suspension in a circular channel with a diameter of 9.5 mm was measured with high spatial resolution. Meanwhile, the rheological behavior was found to be comparable with blood.

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