The mechanical and electrical properties of direct-spun carbon nanotube mat-epoxy composites

Composites of direct-spun carbon nanotube (CNT) mats and epoxy are manufactured and tested in order to determine their mechanical and electrical properties. The mats are spun directly from a floating catalyst, chemical vapour deposition reactor. The volume fraction of epoxy is varied widely by suitable dilution of the epoxy resin with acetone. Subsequent evaporation of the acetone, followed by a cure cycle, leads to composites of varying volume fraction of CNT, epoxy and air. The modulus, strength, electrical conductivity and piezoresistivity of the composites are measured. The CNT mats and their composites exhibit an elastic-plastic stress-strain response under uniaxial tensile loading, and the degree of anisotropy is assessed by testing specimens in 0{\deg}, 45{\deg} and 90{\deg} directions with respect to the draw direction of mat manufacture. The electrical conductivity scales linearly with CNT volume fraction, irrespective of epoxy volume fraction. In contrast, the modulus and strength depend upon both CNT and epoxy volume fractions in a non-linear manner. The macroscopic moduli of the CNT mat-epoxy composites are far below the Voigt bound based on the modulus of CNT walls and epoxy. A micromechanical model is proposed to relate the macroscopic modulus and yield strength of a CNT mat-epoxy composite to the microstructure

Epilepsy Is a Risk Factor for Sudden Cardiac Arrest in the General Population

Background People with epilepsy are at increased risk for sudden death. The most prevalent cause of sudden death in the general population is sudden cardiac arrest (SCA) due to ventricular fibrillation (VF). SCA may contribute to the increased incidence of sudden death in people with epilepsy. We assessed whether the risk for SCA is increased in epilepsy by determining the risk for SCA among people with active epilepsy in a community-based study. Methods and Results This investigation was part of the Amsterdam Resuscitation Studies (ARREST) in the Netherlands. It was designed to assess SCA risk in the general population. All SCA cases in the study area were identified and matched to controls (by age, sex, and SCA date). A diagnosis of active epilepsy was ascertained in all cases and controls. Relative risk for SCA was estimated by calculating the adjusted odds ratios using conditional logistic regression (adjustment was made for known risk factors for SCA). We identified 1019 cases of SCA with ECG-documented VF, and matched them to 2834 controls. There were 12 people with active epilepsy among cases and 12 among controls. Epilepsy was associated with a three-fold increased risk for SCA (adjusted OR 2.9 [95%CI 1.1–8.0.], p = 0.034). The risk for SCA in epilepsy was particularly increased in young and females. Conclusion Epilepsy in the general population seems to be associated with an increased risk for SCA

Can a falling tree make a noise in two forests at the same time?

It is a commonplace to claim that quantum mechanics supports the old idea that a tree falling in a forest makes no sound unless there is a listener present. In fact, this conclusion is far from obvious. Furthermore, if a tunnelling particle is observed in the barrier region, it collapses to a state in which it is no longer tunnelling. Does this imply that while tunnelling, the particle can not have any physical effects? I argue that this is not the case, and moreover, speculate that it may be possible for a particle to have effects on two spacelike separate apparatuses simultaneously. I discuss the measurable consequences of such a feat, and speculate about possible statistical tests which could distinguish this view of quantum mechanics from a ``corpuscular'' one. Brief remarks are made about an experiment underway at Toronto to investigate these issues.Comment: 9 pp, Latex, 3 figs, to appear in Proc. Obsc. Unr. Conf.; Fig 2 postscript repaired on 26.10.9

On the six-dimensional origin of the AGT correspondence

We argue that the six-dimensional (2,0) superconformal theory defined on M \times C, with M being a four-manifold and C a Riemann surface, can be twisted in a way that makes it topological on M and holomorphic on C. Assuming the existence of such a twisted theory, we show that its chiral algebra contains a W-algebra when M = R^4, possibly in the presence of a codimension-two defect operator supported on R^2 \times C \subset M \times C. We expect this structure to survive the \Omega-deformation.Comment: References added. 14 page

Reduction in stiffness of proximal leg muscles during the first 6 months of glucocorticoid therapy for giant cell arteritis: A pilot study using shear wave elastography.

Aim: To investigate muscle stiffness changes in patients treated for giant cell arteritis (GCA) with high‐dose oral glucocorticoids. Methods: Using ultrasound elastography, shear wave velocity (SWV) was measured in the quadriceps, hamstrings and biceps brachii muscles of 14 patients with GCA (4 male, mean age ± SD, 68.2 ± 4.3 years) within the first 2 weeks of initiating glucocorticoid treatment (baseline) and repeated after 3 and 6 months treatment. Muscle strength and performance tests were performed at each visit. Baseline measures were compared with those from 14 healthy controls. Linear mixed models were used to test for change in patient measures over time. Results: At baseline, muscle SWV in patients was not significantly different from controls. With glucocorticoid treatment, there was a reduction in SWV in the leg but not the arm muscles. SWV decreased by a mean of 14% (range 8.3%‐17.3%; P = .001) after 3 months and 18% (range 10.2%‐25.3%; P < .001) after 6‐months in the quadriceps and hamstrings during the resting position. The baseline, 3 and 6 months mean SWV (±SD) for the vastus lateralis were 1.62 ± 0.16 m/s, 1.40 ± 0.10 m/s and 1.31 ± 0.06 m/s, respectively (P < .001). In the patient group as a whole, there was no significant change in muscle strength. However, there were moderate correlations (r = .54‐.69) between exhibiting weaker muscle strength at follow‐up visits and a greater reduction in SWV. Conclusion: Glucocorticoid therapy in patients with GCA was associated with a significant reduction in proximal leg muscle stiffness during the first 6 months. Future research should study a larger sample of patients for a longer duration to investigate if diminished muscle stiffness precedes signs of glucocorticoid‐induced myopathy

The mechanical and electrical properties of direct-spun carbon nanotube mats

The mechanical and electrical properties of a direct-spun carbon nanotube mat are measured. The mat comprises an interlinked random network of nanotube bundles, with approximately 40 nanotubes in a bundle. A small degree of in-plane anisotropy is observed. The bundles occasionally branch, and the mesh topology resembles a 2D lattice of nodal connectivity slightly below 4. The macroscopic in-plane tensile response is elasto-plastic in nature, with significant orientation hardening. In-situ microscopy reveals that the nanotube bundles do not slide past each other at their junctions under macroscopic stain. A micromechanical model is developed to relate the macroscopic modulus and flow strength to the longitudinal shear response of the nanotube bundles. The mechanical and electrical properties of the mat are compared with those of other nanotube arrangements over a wide range of density

Small molecule additive for low-power accumulation mode organic electrochemical transistors

A small molecule additive, dodecylbenzenesulfonate (DBSA), is added to the electrolyte in OECTs to improve the device performance.ERC IMBIBE EPSRC CDT Plastic Electronic

Biochemical engineering nerve conduits using peptide amphiphiles.

Peripheral nerve injury is a debilitating condition. The gold standard for treatment is surgery, requiring an autologous nerve graft. Grafts are harvested from another part of the body (a secondary site) to treat the affected primary area. However, autologous nerve graft harvesting is not without risks, with associated problems including injury to the secondary site. Research into biomaterials has engendered the use of bioartificial nerve conduits as an alternative to autologous nerve grafts. These include synthetic and artificial materials, which can be manufactured into nerve conduits using techniques inspired by nanotechnology. Recent evidence indicates that peptide amphiphiles (PAs) are promising candidates for use as materials for bioengineering nerve conduits. PAs are biocompatible and biodegradable protein-based nanomaterials, capable of self-assembly in aqueous solutions. Their self-assembly system, coupled with their intrinsic capacity for carrying bioactive epitopes for tissue regeneration, form particularly novel attributes for biochemically-engineered materials. Furthermore, PAs can function as biomimetic materials and advanced drug delivery platforms for sustained and controlled release of a plethora of therapeutic agents. Here we review the realm of nerve conduit tissue engineering and the potential for PAs as viable materials in this exciting and rapidly advancing field