Individual grain boundary properties and overall performance of metal-organic-deposition coated conductors

We have investigated single grain boundaries (GBs) isolated in coated conductors produced by Metal-Organic Deposition (MOD). When a magnetic field is swept in the film plane, an angle-dependent crossover from boundary to grain limited critical current density Jc is found. In the force-free orientation, even at fields as high as 8 T, the GBs still limit Jc. We deduce that this effect is a direct consequence of GB meandering. We have employed these single GB results to explain the dependence of Jc of polycrystalline tracks on their width: in-plane measurements become flatter as the tracks are narrowed down. This result is consistent with the stronger GB limitation at field configurations close to force-free found from the isolated boundaries. Our study shows that for certain geometries even at high fields the effect of GBs cannot be neglected.

Bayesian classification of acoustical waveforms under environmental variability

We present in this paper a new multivariate probabilistic approach to Acoustic Pulse Recognition (APR) for tangible interface applications. This model uses Principle Component Analysis (PCA) in a probabilistic framework to classify tapping pulses with a high degree of variability. It was found that this model, achieves a higher robustness to pulse variability than simpler template matching methods, specifically when allowed to train on data containing high variability. © 2011 IEEE.

Phototransistors utilizing individual WS2 nanotubes

We report on the photoresponse characteristics of tungsten disulfide (WS2) nanotubes. Field effect transistors (FETs) were fabricated by using individual WS2 multiwall nanotubes. Photo-sensitivity to visible light is clearly observed, with enhancement of the channel conductivity, carrier mobility and carrier concentration upon illumination in the visible regime. Polarization-sensitive measurements reveal a strong anisotropy of the photocurrent on the polarization angle of the incident light with respect to the WS2 nanotube axis. This nano-scale transistor capable of detecting visible light would have a wide range of applications in medical and consumer electronics. © 2008 IEEE. Crown Copyright.

The horizontal response of framed buildings on individual footings to excavation-induced movements

Deep excavations and tunnelling can cause ground movements that affect buildings within their influence zone. The current approach for building damage assessment is based on tensile strains estimated from the deflection ratio and the horizontal strains at the building foundation. This paper examines the significance of horizontal strains in buildings on individual footings. The first part of the paper presents a case study of a framed building in Singapore which was subjected to the effects of bored tunnelling, where significant horizontal strains were observed. The second part of the paper suggests a method to relate the horizontal strains induced in a building to the stiffness of the frame structure. Using a combination of simplified structural analysis and finite element models, design guidance is proposed to estimate excavation-induced horizontal strains in frame buildings on individual footings. © 2012 Taylor & Francis Group.

Ballasted & electrically steerable carbon nanotube field emitters

Here we present our on-going efforts toward the development of stable ballasted carbon nanotube-based field emitters employing hydrothermally synthesized zinc oxide nanowires and thin film silicon-on-insulator substrates. The semiconducting channel in each controllably limits the emission current thereby preventing detrimental burn-out of individual emitters that occurs due to unavoidable statistical variability in emitter characteristics, particularly in their length. Fabrication details and emitter characterization are discussed in addition to their field emission performance. The development of a beam steerable triode electron emitter formed from hexagonal carbon nanotube arrays with central focusing nanotube electrodes, is also described. Numerical ab-initio simulations are presented to account for the empirical emission characteristics. Our engineered ballasted emitters have shown some of the lowest reported lifetime variations (< 0.7%) with on-times of < 1 ms, making them ideally-suited for next-generation displays, environmental lighting and portable x-rays sources. © 2012 SPIE.

Probabilistic computation in human perception under variability in encoding precision.

A key function of the brain is to interpret noisy sensory information. To do so optimally, observers must, in many tasks, take into account knowledge of the precision with which stimuli are encoded. In an orientation change detection task, we find that encoding precision does not only depend on an experimentally controlled reliability parameter (shape), but also exhibits additional variability. In spite of variability in precision, human subjects seem to take into account precision near-optimally on a trial-to-trial and item-to-item basis. Our results offer a new conceptualization of the encoding of sensory information and highlight the brain's remarkable ability to incorporate knowledge of uncertainty during complex perceptual decision-making.

Variability in encoding precision accounts for visual short-term memory limitations.

It is commonly believed that visual short-term memory (VSTM) consists of a fixed number of "slots" in which items can be stored. An alternative theory in which memory resource is a continuous quantity distributed over all items seems to be refuted by the appearance of guessing in human responses. Here, we introduce a model in which resource is not only continuous but also variable across items and trials, causing random fluctuations in encoding precision. We tested this model against previous models using two VSTM paradigms and two feature dimensions. Our model accurately accounts for all aspects of the data, including apparent guessing, and outperforms slot models in formal model comparison. At the neural level, variability in precision might correspond to variability in neural population gain and doubly stochastic stimulus representation. Our results suggest that VSTM resource is continuous and variable rather than discrete and fixed and might explain why subjective experience of VSTM is not all or none.

Self-similar organization of arrays of individual carbon nanotubes and carbon nanotube micropillars

It is well-known that carbon nanotube (CNT) growth from a dense arrangement of catalyst nanoparticles creates a vertically aligned CNT forest. CNT forests offer attractive anisotropic mechanical, thermal, and electrical properties, and their anisotropic structure is enabled by the self-organization of a large number of CNTs. This process is governed by individual CNT diameter, spacing, and the CNT-to-CNT interaction. However, little information is known about the self-organization of CNTs within a forest. Insight into the self-organization is, however, essential for tailoring the properties of the CNT forests for applications such as electrical interconnects, thermal interfaces, dry adhesives and energy storage. We demonstrate that arrays of CNT micropillars having micron-scale diameters organize in a similar manner as individual CNTs within a forest. For example, as previously demonstrated for individual CNTs within a forest, entanglement of small-diameter CNT micropillars during the initial stage of growth creates a film of entwined pillars. This layer enables coordinated subsequent growth of the pillars in the vertical direction, in a case where isolated pillars would not grow in a self-supporting fashion. Finally, we provide a detailed overview of the self-organization as a function of the diameter, length and spacing of the CNT pillars. This study, which is applicable to many one-dimensional nanostructured films, demonstrates guidelines for tailoring the self-organization which can enable control of the collective mechanical, electrical and interfacial properties of the films. © 2009 Elsevier B.V. All rights reserved.

Morphological variability between wild populations and inbred stocks of a Chinese minnow, Gobiocypris rarus

Gobiocypris rarus, a small, native cyprinid fish, is currently widely used in research on fish pathology, genetics, toxicology, embryology, and physiology in China. To develop this species as a model laboratory animal, inbred strains have been successfully created. In this study, to explore a method to discriminate inbred strains and evaluate inbreeding effects, morphological variation among three wild populations and three inbred stocks of G. rarus was investigated by the multivariate analysis of eight meristic and 30 morphometric characters. Tiny intraspecific variations in meristic characters were found, but these were not effective for population distinction. Stepwise discriminant analysis and cluster analysis of conventional measures and truss network data showed considerabe divergence among populations, especially between wild populations and inbred stocks. The average discriminant accuracy for all populations was 82.1% based on conventional measures and 86.4% based on truss data, whereas the discriminant accuracy for inbred strains was much higher. These results suggested that multivariate analyses of morphometric characters are an effective method for discriminating inbred strains of G. rarus. Morphological differences between wild populations and inbred strains appear to result from both genetic differences and environmental factors. Thirteen characters, extracted from stepwise discriminant analysis, played important roles in morphological differentiation. These characters were mainly measures related to body depth and head size.

High variability of the gvpA-gvpC region in Microcystis

Gas vesicles provide buoyancy to Microcystis and other common cyanobacterial bloom-forming species. gvpA and gvpC are structural genes encoding gas vesicle proteins. Phylogenetic analyses of 10 Microcystis strains/uncultured samples showed that gvpC and each intergenic segment of the gvpA-gvpC region can be divided into two types. The combination of different types of gvpC and intergenic segments is an important factor that diversifies this genomic region. Some Microcystis strains isolated in China possess a 172 to 176 bp sequence tag in the intergenic segment between gvpA and gvpC. The gvpA-gvpC region in Microcystis can be divided into at least 4 classes and more numbers of subclasses. Compared to rbcLX and other regions, the high variability of the gvpA-gvpC region should be more useful in identifying geographical isolates or ecotypes of Microcystis.

Microsatellites assessment of Chinese sturgeon (Acipenser sinensis Gray) genetic variability

Four microsatellites were used to examine the genetic variability of the spawning stocks of Chinese sturgeon, Acipenser sinensis, from the Yangtze River sampled over a 3-year period (1999-2001). Within 60 individuals, a total of 28 alleles were detected over four polymorphic microsatellite loci. The number of alleles per locus ranged from 4 to 15, with an average allele number of 7. The number of genotypes per locus ranged from 6 to 41. The genetic diversity of four microsatellite loci varied from 0.34 to 0.67, with an average value of 0.54. For the four microsatellite loci, the deviation from the Hardy-Weinberg equilibrium was mainly due to null alleles. The mean number of alleles per locus and the mean heterozygosity were lower than the average values known for anadromous fishes. Fish were clustered according to their microsatellite characteristics using an unsupervised 'Artificial Neural Networks' method entitled 'Self-organizing Map'. The results revealed no significant genetic differentiation considering genetic distance among samples collected during different years. Lack of heterogeneity among different annual groups of spawning stocks was explained by the complex age structure (from 8 to 27 years for males and 12 to 35 years for females) of Chinese sturgeon, leading to formulate an hypothesis about the maintenance of genetic diversity and stability in long-lived animals.

A method for individual identification of echolocation signals in free-ranging finless porpoises carrying data loggers

Echolocation click events of a free-ranging juvenile and an adult finless porpoise (Neophocaena phocaenoides) were recorded with an acoustic data logger. Additionally, dive depth and swim speed of the juvenile were recorded with a behavior data logger. Echoes of echolocation signals from the water surface were clearly detected in shallow dives approximately less than 2 m. The delay time between a surface echo and a direct signal corresponded with the two-way transmission time for the animal's depth, indicating that the signals originated from the animal wearing the data loggers. The finless porpoises produced echolocation signals frequently and were thought to be able to detect their depth by listening to echoes from the water surface. (C) 2000 Acoustical Society of America. [S0001-4966(00)01609-X].