Examining the Quasi-Static Uniaxial Compressive Behaviour of Commercial High-Performance Epoxy Matrices.

Four commercial high-performance aerospace aromatic epoxy matrices, CYCOM890, CYCOM977-2, PR520, and PRISM EP2400, were cured to a standardised 2 h, 180 °C cure cycle and evaluated in quasi-static uniaxial compression, as well as by dynamic scanning calorimetry (DSC) and thermogravimetric analysis (TGA). The thermoplastic toughened CYCOM977-2 formulation displayed an overall increase in true axial stress values across the entire stress-strain curve relative to the baseline CYCOM890 sample. The particle-toughened PR520 sample exhibited an overall decrease in true axial stress values past the yield point of the material.

Automated analysis of soft material microindentation.

An understanding of the mechanical properties of soft hydrogel materials over multiple length scales is important for their application in many fields. Typical measurement methods provide either bulk mechanical properties (compression, tensile, rheology) or probing of nano or microscale properties and heterogeneity (nanoindentation, AFM). In this work we demonstrate the complementarity of instrumented microindentation to these techniques, as it provides representative Young's moduli for soft materials with minimal influence of the experimental parameters chosen, and allows mechanical property mapping across macroscopic areas.

The structural efficiency of the sea sponge Euplectella aspergillum skeleton: bio-inspiration for 3D printed architectures.

In Nature, despite the diversity of materials, patterns and structural designs, the majority of biomineralized systems share a common feature: the incorporation of multiple sets of discrete elements across different length scales. This paper is the first to assess whether the design features observed in the hexactinellid sea sponge Euplectella aspergillum can be transferred and implemented for the development of new structurally efficient engineering architectures manufactured by three-dimensional (3D) additive manufacturing (AM). We present an investigation into the design and survival strategies found in the biological system and evaluate their translation into a scaled engineering analogue assessed experimentally and through finite-element (FE) simulations.

Curved Layer Fused Filament Fabrication Using Automated Toolpath Generation.

An automated method for the generation of curved layer toolpaths is demonstrated to produce 3D printed components with improved aesthetic and structural properties using fused filament fabrication printing. Three case studies are shown, which demonstrate the ability of the G-code generating algorithm to resolve concave and convex structures. The combination of conventionally printed layers and curved layers within a single print is also demonstrated by producing double skin curved layer sandwich structures with static printed cores.

Counterpropagating wave acoustic particle manipulation device for the effective manufacture of composite materials.

An ultrasonic assembly device exhibiting broadband behavior and a sacrificial plastic frame is described. This device is used to assemble a variety of microscopic particles differing in size, shape, and material into simple patterns within several host fluids. When the host fluid is epoxy, the assembled materials can be cured and the composite sample extracted from the sacrificial frame.

Concentration-dependent activation of dopamine receptors differentially modulates GABA release onto orexin neurons.

Dopamine (DA) and orexin neurons play important roles in reward and food intake. There are anatomical and functional connections between these two cell groups: orexin peptides stimulate DA neurons in the ventral tegmental area and DA inhibits orexin neurons in the hypothalamus. However, the cellular mechanisms underlying the action of DA on orexin neurons remain incompletely understood.

Ultrasonic assembly of anisotropic short fibre reinforced composites.

We report the successful manufacture of short fibre reinforced polymer composites via the process of ultrasonic assembly. An ultrasonic device is developed allowing the manufacture of thin layers of anisotropic composite material. Strands of unidirectional reinforcement are, in response to the acoustic radiation force, shown to form inside various matrix media.

Ex vivo evaluation of the biomechanical effect of varying monocortical screw numbers on a plate-rod canine femoral gap model.

Objective: To compare the biomechanical behaviour of plate-rod constructs with varying numbers of monocortical screws applied to an ex vivo canine femoral-gap ostectomy model.

Sample Population: Twenty Greyhound dog cadaveric femurs.

Methods: Bone mineral density (BMD) was assessed with dual x-ray absorptiometry.

Biologically inspired crack delocalization in a high strain-rate environment.

Biological materials possess unique and desirable energy-absorbing mechanisms and structural characteristics worthy of consideration by engineers. For example, high levels of energy dissipation at low strain rates via triggering of crack delocalization combined with interfacial hardening by platelet interlocking are observed in brittle materials such as nacre, the iridescent material in seashells. Such behaviours find no analogy in current engineering materials.

Dopamine acts as a partial agonist for α2A adrenoceptor in melanin-concentrating hormone neurons.

Melanin-concentrating hormone (MCH) is a hypothalamic neuropeptide that promotes positive energy balance and anxiety. Since dopamine (DA) is also closely implicated in these functions, the present study investigated the effect of DA on MCH neurons. Using whole-cell patch-clamp recordings in rat brain slices, we found that DA hyperpolarizes MCH neurons by activating G-protein-activated inwardly rectifying K(+) (GIRK) channels.

Characterization and analysis of carbon fibre-reinforced polymer composite laminates with embedded circular vasculature.

A study of the influence of embedded circular hollow vascules on structural performance of a fibre-reinforced polymer (FRP) composite laminate is presented. Incorporating such vascules will lead to multi-functional composites by bestowing functions such as self-healing and active thermal management. However, the presence of off-axis vascules leads to localized disruption to the fibre architecture, i.

Bioinspired engineering study of Plantae vascules for self-healing composite structures.

This paper presents the first conceptual study into creating a Plantae-inspired vascular network within a fibre-reinforced polymer composite laminate, which provides an ongoing self-healing functionality without incurring a mass penalty. Through the application of a 'lost-wax' technique, orthogonal hollow vascules, inspired by the 'ray cell' structures found in ring porous hardwoods, were successfully introduced within a carbon fibre-reinforced epoxy polymer composite laminate. The influence on fibre architecture and mechanical behaviour of single vascules (located on the laminate centreline) when aligned parallel and transverse to the local host ply was characterized experimentally using a compression-after-impact test methodology.

Biomimetic reliability strategies for self-healing vascular networks in engineering materials.

Self-healing via a vascular network is an active research topic, with several recent publications reporting the application and optimization of these systems. This work represents the first consideration of the probable failure modes of a self-healing system as a driver for network design. The critical failure modes of a proposed self-healing system based on a vascular network were identified via a failure modes, effects and criticality analysis and compared to those of the human circulatory system.

Self-healing polymer composites: mimicking nature to enhance performance.

Autonomic self-healing materials, where initiation of repair is integral to the material, are being developed for engineering applications. This bio-inspired concept offers the designer an ability to incorporate secondary functional materials capable of counteracting service degradation whilst still achieving the primary, usually structural, requirement. Most materials in nature are themselves self-healing composite materials.

Minimum mass vascular networks in multifunctional materials.

A biomimetic analysis is presented in which an expression for the optimum vessel diameter for the design of minimum mass branching or vascular networks in engineering applications is derived. Agreement with constructal theory is shown. A simple design case is illustrated and application to more complex cases with branching networks of several generations discussed.

Carbonic anhydrase related protein 8 mutation results in aberrant synaptic morphology and excitatory synaptic function in the cerebellum.

Carbonic anhydrase related protein 8 (Car8) is known to be abundantly expressed in Purkinje cells (PCs), and its genetic mutation causes a motor coordination defect. To determine the underlying mechanism, we analyzed the mouse cerebellum carrying a Car8 mutation. Electrophysiological analysis showed that spontaneous excitatory transmission was largely diminished while paired pulse ratio at parallel fiber-PC synapses was comparable to wild-type, suggesting functional synapses have normal release probability but the number of functional synapses may be lower in mutants.

Bioinspired self-healing of advanced composite structures using hollow glass fibres.

Self-healing is receiving an increasing amount of worldwide interest as a method to autonomously address damage in materials. The incorporation of a self-healing capability within fibre-reinforced polymers has been investigated by a number of workers previously. The use of functional repair components stored inside hollow glass fibres (HGF) is one such bioinspired approach being considered.

Bidirectional dopaminergic modulation of excitatory synaptic transmission in orexin neurons.

Orexin neurons in the lateral hypothalamus (LH)/perifornical area (PFA) are known to promote food intake as well as provide excitatory influence on the dopaminergic reward pathway. Dopamine (DA), in turn, inhibits the reward pathway and food intake through its action in the LH/PFA. However, the cellular mechanism by which DA modulates orexin neurons remains largely unknown.

Impact of abciximab and coronary stenting on outcomes and costs of percutaneous coronary interventions in a community hospital.

Objective: To assess costs and outcomes of coronary stenting and balloon angioplasty with and without adjunctive treatment with abciximab for 3758 consecutive elective percutaneous coronary interventions at a single community center over the 2.5-year period between 1 January 1995 and 30 June 1997.

Results: Abciximab was more common among patients who had recently suffered myocardial infarction, patients with unstable angina, and patients with more complex coronary lesions.

Phase I study of adenoviral delivery of the HSV-tk gene and ganciclovir administration in patients with current malignant brain tumors.

Between December 1996 and September 1998, 13 patients with advanced recurrent malignant brain tumors (9 with glioblastoma multiforme, 1 with gliosarcoma, and 3 with anaplastic astrocytoma) were treated with a single intratumoral injection of 2 x 10(9), 2 x 10(10), 2 x 10(11), or 2 x 10(12) vector particles (VP) of a replication-defective adenoviral vector bearing the herpes simplex virus thymidine kinase gene driven by the Rous sarcoma virus promoter (Adv.RSVtk), followed by ganciclovir (GCV) treatment. The VP to infectious unit ratio was 20:1.

Evaluation of a bileaflet aortic valve prosthesis before and after thrombolytic tissue plasminogen activator therapy by continuous wave Doppler ultrasound.

Thrombotic obstruction of mechanical prosthetic valves is a frequently encountered cause of prosthetic valve dysfunction, which can result in stenosis and regurgitation. We present a case of thrombotic obstruction of a bileaflet mechanical aortic valve prosthesis that resulted in severe stenosis and regurgitation. Considering the known risk factors associated with both surgical and thrombolytic treatments, a decision was made to use tissue plasminogen activator therapy to relieve the burden of the thrombotic valvular obstruction.

One balloon, one stent: an effective cost-containment strategy for elective stent deployment.

A cost-containment strategy to reduce stent procedure-related resources utilizing an integrated system comprised of a Stablizer guide wire, a Brite-Tip guiding catheter, and a single Titan balloon catheter for both lesion predilatation and poststent deployment was compared to a conventional strategy utilizing a nonintegrated guide wire, guiding catheter, and balloon components. Both groups were comparable with respect to demographics, number of lesions stented, and stents deployed per lesion. No differences in lesion length or pre- and poststent minimal luminal diameter were observed.

Assessment of the results of percutaneous transluminal coronary angioplasty using an integrated ultrasound imaging-angioplasty catheter.

To evaluate the results percutaneous transluminal coronary angioplasty (PTCA), intravascular ultrasound imaging was performed in 32 proximal coronary arterial segments and in 16 atherosclerotic lesions after PTCA in 13 patients using a 5 Fr balloon catheter with an ultrasound transducer mounted just proximal to the balloon. Simultaneous angiographic measurements of vessel diameter were also performed using electronic calipers from contrast cine angiograms. There was good correlation between ultrasound and angiographic minimum luminal diameters of the normal proximal vessel (y = 0.