Optimizing cranial implant and fixture design using different materials in cranioplasty

Cranial implants are used to secure intracranial structures, reconstruct the skull contour, normalise cerebral hemodynamic, and repair cranial defects. Larger bone defects require intervention for repair from an implant made from autologous bone or other material. To repair such defects using implants, materials necessitate biocompatibility with the natural bone. Patient Specific Implants (PSI) are designed to repair specific cranial defects following standard procedures for implant design, fabrication and cranioplasty. Autologous bone, bone cement comprising HydroxyApatite (HA), Poly methyl methacrylate (PMMA), Medical Grade Titanium Alloy (Ti-6Al-4V) and Polyether-ether-ketone (PEEK), are widely used to fabricate PSI for repairing different types of bone defects. To optimize a PSI for shape, size and weight, it is essential to design the implant using 3D modelling and fabrication techniques. Effective attachment of an implant material with a defective skull is also influenced by the joints and fixture arrangements at the interface, these fixtures can be of various types, materials and have different joining procedures. In this study, a comparative analysis of different cranial implant materials (Autologous Bone, PMMA, PEEK and Ti-6Al-4V) attached to a defective skull with Ti-6Al-4V and PEEK fixture plates has been performed, using Finite Element Analysis (FEA). Two types of fixture designs were used as Square 'X' and Linear shapes, which were fixed along the interface between implant and the skull. Four fixture plates were fixed symmetrically along the boundary for maximising stability. The findings suggested that all the implant materials were able to sustain extreme boundary conditions such as external loads of 1780N and IntraCranial Pressure (ICP) of 15mmHg without failures. PEEK implants exhibited 13.5 % to 35% lower von Mises stresses in comparison to autologous bone implants and Square 'X' fixture design provided higher stress relieving results in comparison to Linear fixtures by nearly 18.4% for Ti-6Al-4V fixture material and 10.9% for PEEK fixture material, thereby, encouraging PEEK as an alternative to conventional cranial implant and fixture materials

Ultrasonic intensification as a tool for enhanced microbial biofuel yields

peer-reviewedUltrasonication has recently received attention as a novel bioprocessing tool for process intensification in many areas of downstream processing. Ultrasonic intensification (periodic ultrasonic treatment during the fermentation process) can result in a more effective homogenization of biomass and faster energy and mass transfer to biomass over short time periods which can result in enhanced microbial growth. Ultrasonic intensification can allow the rapid selective extraction of specific biomass components and can enhance product yields which can be of economic benefit. This review focuses on the role of ultrasonication in the extraction and yield enhancement of compounds from various microbial sources, specifically algal and cyanobacterial biomass with a focus on the production of biofuels. The operating principles associated with the process of ultrasonication and the influence of various operating conditions including ultrasonic frequency, power intensity, ultrasonic duration, reactor designs and kinetics applied for ultrasonic intensification are also described

Active layers of high-performance lead zirconate titanate at temperatures compatible with silicon nano- and microelecronic devices

Applications of ferroelectric materials in modern microelectronics will be greatly encouraged if the thermal incompatibility between inorganic ferroelectrics and semiconductor devices is overcome. Here, solution-processable layers of the most commercial ferroelectric compound ─ morphotrophic phase boundary lead zirconate titanate, namely Pb(Zr0.52Ti0.48)O3 (PZT) ─ are grown on silicon substrates at temperatures well below the standard CMOS process of semiconductor technology. The method, potentially transferable to a broader range of Zr:Ti ratios, is based on the addition of crystalline nanoseeds to photosensitive solutions of PZT resulting in perovskite crystallization from only 350 °C after the enhanced decomposition of metal precursors in the films by UV irradiation. A remanent polarization of 10.0 μC cm−2 is obtained for these films that is in the order of the switching charge densities demanded for FeRAM devices. Also, a dielectric constant of ~90 is measured at zero voltage which exceeds that of current single-oxide candidates for capacitance applications. The multifunctionality of the films is additionally demonstrated by their pyroelectric and piezoelectric performance. The potential integration of PZT layers at such low fabrication temperatures may redefine the concept design of classical microelectronic devices, besides allowing inorganic ferroelectrics to enter the scene of the emerging large-area, flexible electronics

Dielectric properties of 1 : 1 ordered Pb(Mg1/3Ta2/3)O-3 ceramics

Thermally induced coarsening of the chemically ordered domains in Pb(Mg1/3Ta2/3)O-3 (PMT) ceramics promotes the studying of dielectric behavior of the 1: 1 B-cations ordered PMN-style complex perovskites. In this work, PMT ceramics with different degrees of chemical order were prepared, and their dielectric, and ferroelectric properties of disordered and ordered ceramics were studied as a function of temperature, frequency, and electrical field. It was found that the weak field relaxor nature is insensitive to the chemical order, whereas some non-linear behaviors showed ordering-degree dependence at the low temperature range. (c) 2005 Elsevier Ltd. All rights reserved