Enhancement of heat transfer at boiling in electrohydrodynamic flow

The influence of the electric field strength and interelectrode spacing on the heat transfer intensity at boiling in an electrohydrodynamic flow was studied. It was stated that the heat transfer coefficient increases with the increasing of the field strength. The influence of the interelectrode spacing is ambiguous. The efficiency of the action of a electrohydrodynamic flow on the heat transfer intensity at boiling was evaluated using the ratio of the heat transfer coefficient at boiling in the field to the heat transfer coefficient at boiling without the field. The relationships for calculation were obtained that satisfactorily agree with the experimental data.

Abstract 17013: Voltage Resolution of Standard Bipolar and Omnipolar Ventricular Electrograms

Introduction: Standard bipolar voltage (BiV) mapping is dependent on bipole axis orientation compared to the direction of the activation wavefront. In contrast, omnipolar mapping technology (OmniT) allows for direction-independent voltage measurement, yielding a maximum for each site sampled. However, it is unclear if normal voltage values are the same for BiV and OmniT. Hypothesis: To determine whether electrical signal obtained with OmniT are greater than BiV, using a single 4x4 grid array catheter (HD Grid) inserted in the left ventricle (LV) of an experimental animal. Methods: HD Grid consists of 4 splines, allowing for orthogonal bipoles along (AL) a single spline and across (AC) adjacent splines, allowing for simultaneous OmniT and BiV evaluation. Animals (n=3) underwent transseptal LV mapping during sinus rhythm (SR) and right ventricular pacing (RVP) using HD Grid (4mm interelectrode spacing). Abbott Precision research software was used to generate electroanatomic maps. Peak-to-peak voltage data for OmniT and BiV, both along and across the splines, were exported to a spreadsheet. Data were normalized via log transformation and compared with t-test. Results: Mean voltages and 95% confidence interval for OmniT were consistently greater than BiV AL and AC for both SR and RVP (p<0.05), while BiV AL and AC were comparable. No difference was seen when comparing each method during SR and RVP. The absolute BiV difference due to orientation was significant. See Table. Conclusions: Amplitude of OmiT electorgrams are greater with respect to BiV, which is consistent with the ability of omnipolar technology to capture maximal signals independently from waveform direction. This should be taken into account when determining the optimal OmniT value for ventricular scar.

Tuning Nanopore Diameter of Titanium Surfaces to Improve Human Gingival Fibroblast Response

The aim of this study was to determine the optimal nanopore diameter of titanium nanostructured surfaces to improve human gingival fibroblast (hGF) response, with the purpose of promoting gingiva integration to dental implant abutments. Two TiO2 nanoporous groups with different diameters (NP-S ~48 nm and NP-B ~74 nm) were grown on Ti foils using an organic electrolyte containing fluoride by electrochemical oxidation, varying the applied voltage and the interelectrode spacing. The surfaces were characterized by scanning electron microscope (SEM), atomic force microscopy (AFM), and contact angle. The hGF were cultured onto the different surfaces, and metabolic activity, cytotoxicity, cell adhesion, and gene expression were analyzed. Bigger porous diameters (NP-B) were obtained by increasing the voltage used during anodization. To obtain the smallest diameter (NP-S), apart from lowering the voltage, a lower interelectrode spacing was needed. The greatest surface area and number of peaks was found for NP-B, despite these samples not being the roughest as defined by Ra. NP-B had a better cellular response compared to NP-S. However, these effects had a significant dependence on the cell donor. In conclusion, nanoporous groups with a diameter in the range of 74 nm induce a better hGF response, which may be beneficial for an effective soft tissue integration around the implant.

Ultraviolet Photodetectors Based on MgZnO Thin Films

In recent years, MgZnO alloy becomes one of the most suitable materials for the fabrication of ultraviolet detectors. In this paper, we have fabricated three metal semiconductor metal (MSM) photodetectors on Mg0.42Zn0.58O film grown by radio frequency magnetron sputtering. The interdigital electrodes are 500 um long and 5 um wide with an interelectrode spacing 2, 5 and 10 um, respectively. The structural, electrical and optical properties of epilayers were characterized by various techniques. At 5 V bias, a peak responsivity of 1.09 mA/W was achieved at 283 nm for the device with 2 um interelectrode spacing. The peak responsivity at 283 nm increased with the reduction of the finger pitch for three devices and the ultraviolet-visible rejection ratio (R283 nm/R400 nm) was more than one order of magnitude at 5 V bias.