Conformal oxide coating of Carbon Nanotubes

The International Roadmap for Ferroelectric Memories requires three-dimensional integration of high-dielectric materials onto metal interconnects or bottom electrodes by 2010. We report the first integration of high-dielectric oxide films onto carbon nanotube electrodes with an aim of ultra-high integration density of FeRAMs (Tb/in2).Comment: 4 pages, 3 figure

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

Dopamine Signaling and Oxytocin Administration in a Rat Model of Empathy

The rat model is commonly used to study prosocial and empathetic behavior. However, the neural underpinnings of such behavior are unknown. We investigated the potential roles of two neurotransmitters, dopamine (DA) and oxytocin (OT), in prosocial behavior of rats. Our first experiment used a Pavlovian association task with two rats to investigate how DA release was modulated by social context. This experiment used fast-scan cyclic voltammetry (FSCV) to measure subsecond DA release in the nucleus accumbens (NAc). Consistent with previous work, cues that predicted reward were associated with increased DA release, and cues that predicted shock inhibited DA release non-discriminately across trial types. However, during shock trials, DA release was modulated by social context in two ways. First, reductions in DA release during shock trials were weaker in the presence of the conspecific, suggesting a consoling effect which was supported by behavioral indicators. Second, DA release during shock trials increased when shock was administered to the conspecific, suggesting that recording rats used the reactions of the conspecific to verify personal safety. We concluded that DA release is modulated by social context in that rats use social cues to optimize predictions about their own well-being. In our second experiment, we investigated the influence of oxytocin on prosocial behavior. Oxytocin was administered intranasally prior to a distress task in which a lever press resulted in reward delivery and one of three additional outcomes: no shock (‘reward-only’), shock to engaged rat (‘shock-self’), or shock to the conspecific (‘shock-other’). Results demonstrated that oxytocin did not significantly increase prosocial behaviors

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 relaxation in antiferroelectric multigrain PbZrO<SUB>3</SUB> thin films

Antiferroelectric materials are found to be good alternative material compositions for high charge storage devices and transducer applications. Lead zirconate (PZ) is a room temperature antiferroelectric material. Thin films of PZ with various thicknesses were deposited by excimer laser ablation technique on Pt coated Si-substrates at a substrate temperature of 300°C and, subsequently, post annealed at 650° C. The antiferroelectric nature of PZ thin films was studied over a temperature range 30-250° C. Effect of thickness on the net dielectric constant was studied in detail and the calculated interfacial dielectric layer thickness is 0.1 nm approximately, with a bulk dielectric constant of 222 at 100 kHz. Impedance and electric modulus formalisms were employed in order to gain an insight of the microstructural details of multigrain thin films. A comprehensive study on relaxation mechanism revealed that the Maxwell-Wagner type polarization is the basic relaxation phenomenon in the multigrain PZ thin films, due to the presence of multiple grain and grain boundaries across the film thickness. The activation energies from the interior grain relaxation and ac conductivity studies were 0.631 and 0.563 eV, respectively. These activation energies were attributed to the excitation of the charge carriers from a set of shallow traps and/or oxygen vacancies present at an average depth of 0.5-0.6 eV from the bottom of the conduction band

Antiferroelectric thin films for MEMs applications

Antiferroelectric compositions have many potential applications in energy conversion and microelectromechanical systems. Electric field induced phase transitions between ferroelectric and antiferroelectric phases were studied in antiferroelectric lead zirconate and modified lead zirconate titanate stannate family thin films for various smart system applications. Thin films of various antiferroelectric thin film compositions such as PbZrO3, Nb-and La-modified Lead Zirconate Titanate Stannate were processed by pulsed excimer laser ablation technique. Dielectric, hysteresis, pyroelectric and switching properties were studied in detail for a new generation of functional materials. A comparative study of functional properties is presented with these antiferroelectric compositions in comparison with the conventional ferroelectric compositions

Study of La-modified antiferroelectric PbZrO<SUB>3</SUB> thin films

Dielectric and DC electrical properties of antiferroelectric lead zirconate and La-doped lead zirconate thin films deposited using a pulsed excimer-laser ablation technique were studied in detail. Increased La dopant concentration in pure lead zirconate thin films reduced the dielectric maximum and Curie temperature. At 9 mol.% of La in pure lead zirconate, the dielectric transition temperature reduced to room temperature. A gradual change from antiferroelectric to paraelectric through ferroelectric phases was observed with the addition of La to pure lead zirconate. The DC electrical properties of pure lead zirconate and the effect of donor addition on leakage current properties were studied. Correlation between the macroscopic changes observed in the charge transport mechanisms, microscopic defect chemistry and charge-carrier trapping phenomenon was examined in detail

Antiferroelectric lead zirconate thin films by excimer laser ablation

Utilization of antiferroelectric thin films was proposed for high charge storage capacitors and transducer applications. The volume changes that are associated with the AFE⇒FE and FE ⇒ AFE phases are high enough to use them in MEMs device technology. Lead zirconate was the first identified antiferroelectric compound with a reported dielectric phase transition temperature of ~230° C. In this article, deposition of lead zirconate thin films by a pulsed excimer laser ablation technique is reported. The antiferroelectric nature of the lead zirconate thin films were confirmed by the presence of double hysteresis loop in polarization vs. applied electric field response as well as double butterfly behavior in capacitance vs. voltage characteristics. The variations in the polarization hysteresis with temperature were elucidated in detail. The switching times between the field induced FE and AFE phases (backward switching) were studied at various applied electric fields

Study of AC electrical properties in multigrain antiferroelectric lead zirconate thin films

Antiferroelectric lead zirconate (PZ) thin films were deposited by excimer laser ablation technique on Pt-coated Si substrates. Antiferroelectric thin film compositions are potential candidates for high charge storage and microelectromechanical systems. The antiferroelectric nature in PZ thin films was confirmed by means of double hysteresis behaviour in polarisation vs. applied electric field and double butterfly response in capacitance vs. applied voltage measurements. The maximum spontaneous polarisation observed was 37 &#181; C/cm2 with zero remnant polarisation at an applied electric field of 225 kV/cm. PZ thin films showed a polycrystalline multigrain structure and detail comprehensive study of dielectric relaxation and ac electrical properties were carried out