Carbon nanotubes (CNT) are remarkable materials with a simple and inert molecular structure that gives rise to a range of potentially valuable physical and electronic properties, including high ...aspect ratio, high mechanical strength and excellent electrical conductivity. This review summarizes recent research on the application of CNT-based materials to study and control cells of the nervous system. It includes the use of CNT as cell culture substrates, to create patterned surfaces and to study cell-matrix interactions. It also summarizes recent investigations of CNT toxicity, particularly as related to neural cells. The application of CNT-based materials to directing the differentiation of progenitor and stem cells toward neural lineages is also discussed. The emphasis is on how CNT surface chemistry and nanotopography can be altered, and how such changes can affect neural cell function. This knowledge can be applied to creating improved neural interfaces and devices, as well as providing new approaches to neural tissue engineering and regeneration.
Carbon nanotubes are attractive as additives in fiber-reinforced composites due to their high aspect ratio, strength and electrical conductivity. In the present study, solubilized collagen Type I was ...polymerized in the presence of dispersed single-walled carbon nanotubes (SWNT) and human dermal fibroblast cells (HDF) to produce collagen–SWNT composite biomaterials with HDF embedded directly in the matrix. The resulting constructs, with SWNT loadings of 0 (control), 0.8, 2.0 and 4.0 wt.% SWNT, were cultured and electrical properties were evaluated in the frequency range 5–500
kHz at days 3 and 7. All collagen–SWNT hydrogel matrices underwent HDF-mediated gel compaction over time in culture, but the presence of SWNT significantly decreased the rate and extent of gel compaction. Viability of HDF in all constructs was consistently high and cell morphology was not affected by the presence of SWNT. However, cell number at day 7 in culture decreased with increasing SWNT loading. Electrical conductivity of the constructs varied from 3 to 7
mS
cm
−1, depending on SWNT loading level. Conductivity increased uniformly with increasing wt.% of SWNT (
R
=
0.78) and showed a modest frequency dependence, suggesting that the electrical percolation threshold had not been reached in these materials. These data demonstrate that the electrical conductivity of cell-seeded collagen gels can be increased through the incorporation of carbon nanotubes. Protein–SWNT composite materials may have application as scaffolds for tissue engineering, as substrates to study electrical stimulation of cells, and as transducers or leads for biosensors.
Between 2011 March and 2014 August Swift responded to 20 triggers from the IceCube neutrino observatory, observing the IceCube 50 per cent confidence error circle in X-rays, typically within 5 h of ...the trigger. No confirmed counterpart has been detected. We describe the Swift follow-up strategy and data analysis and present the results of the campaign. We discuss the challenges of distinguishing the X-ray counterpart to a neutrino trigger from serendipitous uncatalogued X-ray sources in the error circle, and consider the implications of our results for future strategies for multimessenger astronomy, with particular reference to the follow-up of gravitational wave triggers from the advanced-era detectors.
Merapi Volcano, Indonesia, is one of the most active dome building volcanoes worldwide. Instabilities at the growing dome cause rockfalls and hot block and ash flows, which can reach run-out ...distances of several kilometers. Therefore, Merapi has been monitored extensively for many years. However, direct visual observation of the dome is often impossible due to cloud coverage of the summit. In October 2001, a first prototype Doppler radar system was installed to overcome this shortcoming. The system is able to penetrate clouds and observe material movements at the dome, giving valuable information about dynamic processes in the dome area. The system also allows detection of rainfall in several distance intervals. For precise positioning of the beam, the system was equipped with an electromechanical mounting in 2003. A charge-coupled device (CCD) camera attached to the radar mirror documents the radar beam position and provides visual observation of the dome. Recorded data, camera images, and status information are telemetered to the Merapi Volcano Observatory, where they can be processed and interpreted. Status information is also sent via short message service via a global system for mobile communications (GSM) modem. By processing the Doppler radar data, we are able to discriminate between three different types of instability events: sliding dome material, dome material gravitationally breaking off the dome, and explosive outbursts of dome material due to expansion of volcanic gas. In order to independently verify our observations, we compared rockfall events detected by the radar system to seismic recordings and found a good correlation.
ABSTRACT IceTop is an air-shower array located on the Antarctic ice sheet at the geographic South Pole. IceTop can detect an astrophysical flux of neutrons from Galactic sources as an excess of ...cosmic-ray air showers arriving from the source direction. Neutrons are undeflected by the Galactic magnetic field and can typically travel 10 (E/PeV) pc before decay. Two searches are performed using 4 yr of the IceTop data set to look for a statistically significant excess of events with energies above 10 PeV (1016 eV) arriving within a small solid angle. The all-sky search method covers from −90° to approximately −50° in declination. No significant excess is found. A targeted search is also performed, looking for significant correlation with candidate sources in different target sets. This search uses a higher-energy cut (100 PeV) since most target objects lie beyond 1 kpc. The target sets include pulsars with confirmed TeV energy photon fluxes and high-mass X-ray binaries. No significant correlation is found for any target set. Flux upper limits are determined for both searches, which can constrain Galactic neutron sources and production scenarios.
Since the recent detection of an astrophysical flux of high-energy neutrinos, the question of its origin has not yet fully been answered. Much of what is known about this flux comes from a small ...event sample of high neutrino purity, good energy resolution, but large angular uncertainties. In searches for point-like sources, on the other hand, the best performance is given by using large statistics and good angular reconstructions. Track-like muon events produced in neutrino interactions satisfy these requirements. We present here the results of searches for point-like sources with neutrinos using data acquired by the IceCube detector over 7 yr from 2008 to 2015. The discovery potential of the analysis in the northern sky is now significantly below = 10−12 TeV cm−2 s−1, on average 38% lower than the sensitivity of the previously published analysis of 4 yr exposure. No significant clustering of neutrinos above background expectation was observed, and implications for prominent neutrino source candidates are discussed.
We report on results of an all-sky search for high-energy neutrino events interacting within the IceCube neutrino detector conducted between May 2010 and May 2012. The search follows up on the ...previous detection of two PeV neutrino events, with improved sensitivity and extended energy coverage down to about 30 TeV. Twenty-six additional events were observed, substantially more than expected from atmospheric backgrounds. Combined, both searches reject a purely atmospheric origin for the 28 events at the 4σ level. These 28 events, which include the highest energy neutrinos ever observed, have flavors, directions, and energies inconsistent with those expected from the atmospheric muon and neutrino backgrounds. These properties are, however, consistent with generic predictions for an additional component of extraterrestrial origin.
PDF
