723 research outputs found
Fabrication and Characterisation of Polyaniline/Laponite based Semiconducting Organic/Inorganic Hybrid Material
Novel organic-inorganic semiconducting hybrid material is developed by chemically grafting polyaniline (PANI) onto an inorganic template, Laponite. The surface active silanol groups of the Laponite sheets were silylated with an aniline functionalised 3-phenylaminopropyltrimethoxysilane (PAPTMOS) coupling agent followed by deposition of PANI onto the silylated surface. The method includes the reaction of Laponite with PAPTMOS dissolved in a very small amount of methanol at 110 °C for 44 h in a vacuum oven, interaction of the silylated product with PANI via in situ polymerisation of aniline and one-step isolation process by means of the removal of the non-connected PANI with N-methylpyrrolidinone-diethylamine binary solvent. After isolation and re-doping with methane sulfonic acid the Laponite-PAPTMOS-PANI hybrid becomes electrically conductive. The chemical attachment of PANI with silylated Laponite in the hybrids were characterised by Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy, elemental analysis, and scanning electron microscopy.Defence Science Journal, Vol. 64, No. 3, May 2014, pp. 193-197, DOI:http://dx.doi.org/10.14429/dsj.64.718
LBT/LUCIFER near-infrared spectroscopy of PV Cephei. An outbursting young stellar object with an asymmetric jet
We present a detailed spectroscopic investigation of the young eruptive star
PV Cep, to improve our understanding of its nature and characterise its
circumstellar environment after its last outburst in 2004. The analysis of our
medium-resolution spectroscopy in the near-IR (0.9-2.35 um), collected in 2012
at the Large Binocular Telescope with the IR spectrograph LUCIFER, allows us to
infer the main stellar parameters (visual extinction, accretion luminosity,
mass accretion and ejection rates), and model the inner disc, jet, and wind.
The NIR spectrum displays several strong emission lines associated with
accretion/ejection activity and circumstellar environment. Our analysis shows
that the brightness of PV Cep is fading, as well as the mass accretion rate
(2x10^-7 Msun/yr^-1 in 2012 vs ~5x10^-6 Msun/yr^-1 in 2004), which is more than
one order of magnitude lower than in the outburst phase. Among the several
emission lines, only the [FeII] intensity increased after the outburst. The
observed [FeII] emission delineates blue- and red-shifted lobes, both with
high- and low-velocity components, which trace an asymmetric jet and wind,
respectively. The observed emission in the jet has a dynamical age of ~8 years,
indicating that it was produced during the last outburst. The mass ejection
rate in both lobes is 1.5x10^-7 Msun/yr^-1, approximately matching the high
accretion rate observed during and immediately after the outburst . The
observed jet/outflow asymmetries are consistent with an inhomogeneous medium.
Our modelling of the CO emission hints at a small-scale gaseous disc ring,
extending from ~0.2-0.4 AU to ~3 AU from the source, with an inner temperature
of ~3000 K. Our HI lines modelling indicates that most of the observed emission
comes from an expanding disc wind at Te=10000 K. The line profiles are strongly
affected by scattering, disc screening, and outflow self-absorption.Comment: To be published in A&
A computational neuroscience framework for quantifying warning signals
Animal warning signals show remarkable diversity, yet subjectively appear to share certain visual features that make defended prey stand out and look different from more cryptic palatable species. For example, many (but far from all) warning signals involve high contrast elements, such as stripes and spots, and often involve the colours yellow and red. How exactly do aposematic species differ from nonâaposematic ones in the eyes (and brains) of their predators? Here, we develop a novel computational modelling approach, to quantify prey warning signals and establish what visual features they share. First, we develop a model visual system, made of artificial neurons with realistic receptive fields, to provide a quantitative estimate of the neural activity in the first stages of the visual system of a predator in response to a pattern. The system can be tailored to specific species. Second, we build a novel model that defines a âneural signatureâ, comprising quantitative metrics that measure the strength of stimulation of the population of neurons in response to patterns. This framework allows us to test how individual patterns stimulate the model predator visual system. For the predatorâprey system of birds foraging on lepidopteran prey, we compared the strength of stimulation of a modelled avian visual system in response to a novel database of hyperspectral images of aposematic and undefended butterflies and moths. Warning signals generate significantly stronger activity in the model visual system, setting them apart from the patterns of undefended species. The activity was also very different from that seen in response to natural scenes. Therefore, to their predators, lepidopteran warning patterns are distinct from their nonâdefended counterparts and stand out against a range of natural backgrounds. For the first time, we present an objective and quantitative definition of warning signals based on how the pattern generates population activity in a neural model of the brain of the receiver. This opens new perspectives for understanding and testing how warning signals have evolved, and, more generally, how sensory systems constrain signal design
The mass ratio and formation mechanisms of Herbig Ae/Be star binary systems
We present B and R band spectroastrometry of a sample of 45 Herbig Ae/Be
stars in order to study their binary properties. All but one of the targets
known to be binary systems with a separation of ~0.1-2.0 arcsec are detected by
a distinctive spectroastrometric signature. Some objects in the sample exhibit
spectroastrometric features that do not appear attributable to a binary system.
We find that these may be due to light reflected from dusty halos or material
entrained in winds. We present 8 new binary detections and 4 detections of an
unknown component in previously discovered binary systems. The data confirm
previous reports that Herbig Ae/Be stars have a high binary fraction, 74+/-6
per cent in the sample presented here. We use a spectroastrometric
deconvolution technique to separate the spatially unresolved binary spectra
into the individual constituent spectra. The separated spectra allow us to
ascertain the spectral type of the individual binary components, which in turn
allows the mass ratio of these systems to be determined. In addition, we
appraise the method used and the effects of contaminant sources of flux. We
find that the distribution of system mass ratios is inconsistent with random
pairing from the Initial Mass Function, and that this appears robust despite a
detection bias. Instead, the mass ratio distribution is broadly consistent with
the scenario of binary formation via disk fragmentation.Comment: Accepted for publication in MNRAS, minor changes made in proof stag
An investigation of the close environment of beta Cep with the VEGA/CHARA interferometer
High-precision interferometric measurements of pulsating stars help to
characterize their close environment. In 1974, a close companion was discovered
around the pulsating star beta Cep using the speckle interferometry technique
and features at the limit of resolution (20 milli-arcsecond or mas) of the
instrument were mentioned that may be due to circumstellar material. Beta Cep
has a magnetic field that might be responsible for a spherical shell or
ring-like structure around the star as described by the MHD models. Using the
visible recombiner VEGA installed on the CHARA long-baseline interferometer at
Mt. Wilson, we aim to determine the angular diameter of beta Cep and resolve
its close environment with a spatial resolution up to 1 mas level. Medium
spectral resolution (R=6000) observations of beta Cep were secured with the
VEGA instrument over the years 2008 and 2009. These observations were performed
with the S1S2 (30m) and W1W2 (100m) baselines of the array. We investigated
several models to reproduce our observations. A large-scale structure of a few
mas is clearly detected around the star with a typical flux relative
contribution of 0.23 +- 0.02. Our best model is a co-rotational geometrical
thin ring around the star as predicted by magnetically-confined wind shock
models. The ring inner diameter is 8.2 +- 0.8 mas and the width is 0.6 +- 0.7
mas. The orientation of the rotation axis on the plane of the sky is PA = 60 +-
1 deg, while the best fit of the mean angular diameter of beta Cep gives UD[V]
= 0.22 +- 0.05 mas. Our data are compatible with the predicted position of the
close companion of beta Cep. These results bring additional constraints on the
fundamental parameters and on the future MHD and asteroseismological models of
the star.Comment: Paper accepted for publication in A&A (in press
Why does entrepreneurial orientation affect company performance?
© 2019 Strategic Management Society Research summary: To better understand why entrepreneurial orientation (EO) is positively associated with company performance, we propose and test a reconceptualization of how the components of EO (risk-taking, innovativeness, proactiveness) combine in driving performance. Drawing on financial economics theory, our conceptualization highlights that all three components positively contribute to performance, but in different ways. Risk-taking has a direct positive relationship with performance, which can be understood through the riskâreturn tradeoff that is central in financial economics theory. The relationship between risk-taking and performance is conditional on the level of innovativeness and thus innovativeness contributes to performance through its effect on the type of risk-taking. Proactiveness contributes to performance through its positive effect on the level of risk-taking. Managerial summary: This study analyzes three key drivers of company performance: risk-taking, innovativeness, and proactiveness. We show that constructive risk-taking is the central driver of company performance, mirroring the principle of risk and return in financial investment settings. Risk- taking that is associated with innovation has a particularly strong positive relationship with performance, consistent with innovation being a driver of growth and profitability. More proactive firms tend to take on more risk and thus also perform better than less proactive firms
Spectroscopic analysis of the B/Be visual binary HR 1847
We studied both components of a slightly overlooked visual binary HR 1847
spectroscopically to determine its basic physical and orbital parameters. Basic
stellar parameters were determined by comparing synthetic spectra to the
observed echelle spectra, which cover both the optical and near-IR regions. New
observations of this system used the Ond\v{r}ejov and Rozhen 2-m telescopes and
their coud\'e spectrographs. Radial velocities from individual spectra were
measured and then analysed with the code {\FOTEL} to determine orbital
parameters. The spectroscopic orbit of HR 1847A is presented for the first
time. It is a single-lined spectroscopic binary with a B-type primary, a period
of 719.79 days, and a highly eccentric orbit with e=0.7. We confirmed that HR
1847B is a Be star. Its H\alpha emission significantly decreased from 2003 to
2008. Both components have a spectral type B7-8 and luminosity class IV-V.Comment: Astronomy and Astrophysics, accepte
Early Life Events Carry Over to Influence Pre-Migratory Condition in a Free-Living Songbird
Conditions experienced during development can have long-term consequences for individual success. In migratory songbirds, the proximate mechanisms linking early life events and survival are not well understood because tracking individuals across stages of the annual cycle can be extremely challenging. In this paper, we first use a 13 year dataset to demonstrate a positive relationship between 1st year survival and nestling mass in migratory Savannah sparrows (Passerculus sandwichensis). We also use a brood manipulation experiment to show that nestlings from smaller broods have higher mass in the nest relative to individuals from larger broods. Having established these relationships, we then use three years of field data involving multiple captures of individuals throughout the pre-migratory period and a multi-level path model to examine the hypothesis that conditions during development limit survival during migration by affecting an individual's ability to accumulate sufficient lean tissue and fat mass prior to migration. We found a positive relationship between fat mass during the pre-migratory period (SeptâOct) and nestling mass and a negative indirect relationship between pre-migratory fat mass and fledging date. Our results provide the first evidence that conditions during development limit survival during migration through their effect on fat stores. These results are particularly important given recent evidence showing that body condition of songbirds at fledging is affected by climate change and anthropogenic changes to landscape structure
Do adults with high functioning autism or Asperger Syndrome differ in empathy and emotion recognition?
The present study examined whether adults with high functioning autism (HFA) showed greater difficulties in (i) their self-reported ability to empathise with others and/or (ii) their ability to read mental states in othersâ eyes than adults with Asperger syndrome (AS). The Empathy Quotient (EQ) and âReading the Mind in the Eyesâ Test (Eyes Test) were compared in 43 adults with AS and 43 adults with HFA. No significant difference was observed on EQ score between groups, while adults with AS performed significantly better on the Eyes Test than those with HFA. This suggests that adults with HFA may need more support, particularly in mentalizing and complex emotion recognition, and raises questions about the existence of subgroups within autism spectrum conditions
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