11,848 research outputs found
A model of ant route navigation driven by scene familiarity
In this paper we propose a model of visually guided route navigation in ants that captures the known properties of real behaviour whilst retaining mechanistic simplicity and thus biological plausibility. For an ant, the coupling of movement and viewing direction means that a familiar view specifies a familiar direction of movement. Since the views experienced along a habitual route will be more familiar, route navigation can be re-cast as a search for familiar views. This search can be performed with a simple scanning routine, a behaviour that ants have been observed to perform. We test this proposed route navigation strategy in simulation, by learning a series of routes through visually cluttered environments consisting of objects that are only distinguishable as silhouettes against the sky. In the first instance we determine view familiarity by exhaustive comparison with the set of views experienced during training. In further experiments we train an artificial neural network to perform familiarity discrimination using the training views. Our results indicate that, not only is the approach successful, but also that the routes that are learnt show many of the characteristics of the routes of desert ants. As such, we believe the model represents the only detailed and complete model of insect route guidance to date. What is more, the model provides a general demonstration that visually guided routes can be produced with parsimonious mechanisms that do not specify when or what to learn, nor separate routes into sequences of waypoints
Which anthropometric and lower body power variables are predictive of professional and amateur playing status in male rugby union players?
The purpose of this study was to compare anthropometric and lower body power measurements between current professional and amateur male rugby union players. The present study also sought to determine which anthropometric and physical performance variables were predictive of playing standard. Thirty professional and 30 amateur RU players performed Wattbike 6 s maximal effort (WB6S) and countermovement (CMJ) and squat jump (SJ) assessments, anthropometric measures were also taken. Dependant variables recorded and analysed including: body mass, stature, Σ8 site skinfolds, WB6S absolute and relative peak power, CMJ and SJ average concentric force, jump height, peak velocity, time to peak force, rate of force development (RFD) and absolute and relative peak force and power. Professional players were heavier, taller and leaner than their amateur counterparts (p < 0.05). Professional players performed significantly better in all physical performance measures except CMJ and SJ time to peak force, CMJ RFD and SJ relative peak force. Variables which were predictive of playing standard were: Σ8 skinfolds, CMJ peak velocity and WB6S absolute and relative peak power (p < 0.05). These findings indicate that the current body of male professional RU players is anthropometrically and physically superior to their amateur counterparts, although not all variables assessed here were predictive of playing standard. Data presented here indicate that Σ8 skinfolds, WB6S absolute and relative power and CMJ peak velocity are predictive of playing standard, whereas other anthropometric and strength and power variables are not
Community experiences of organised crime in Scotland
The research explored community experiences of serious organised crime in Scotland (SOC). The report provides information on the nature and extent of the impact of SOC on everyday life in the community, as well as offering suggestions for policy development. The study sought to answer the following questions: 1)What are the relationships that exist between SOC and communities in Scotland? 2)What are the experiences and perceptions of residents, stakeholders and organisations of the scope and nature of SOC within their local area? and 3)How does SOC impact on community wellbeing, and to what extent can the harms associated with SOC be mitigated
Fostering children's relationship with nature : exploring the potential of Forest school
Forest School offers children opportunities to explore the natural environment regularly over an extended period of time. It is based on six key principles, one of which states Forest School fosters a relationship with nature and develops long-term pro-environment attitudes through regular personal experiences in nature. We consider to what extent this aim is achieved by exploring the published evidence. We identify that a relationship with nature could be demonstrated under six themes although there is little robust evidence to support this. We suggest further research is carried out directly linked to this aim of Forest School
Separating baryons and dark matter in cluster cores: a full 2-D lensing and dynamic analysis of Abell 383 and MS2137-23
(abridged) We utilize existing imaging and spectroscopic data for the galaxy
clusters MS2137-23 and Abell 383 to present improved measures of the
distribution of dark and baryonic material in the clusters' central regions.
Our method, based on the combination of gravitational lensing and dynamical
data, is uniquely capable of separating the distribution of dark and baryonic
components at scales below 100 kpc. We find a variety of strong lensing models
fit the available data, including some with dark matter profiles as steep as
expected from recent simulations. However, when combined with stellar velocity
dispersion data for the brightest member, shallower inner slopes than predicted
by numerical simulations are preferred. For Abell 383, the preferred shallow
inner slopes are statistically a good fit only when the multiple image position
uncertainties associated with our lens model are assumed to be 0\farcs5, to
account for unknown substructure. No statistically satisfactory fit was
obtained matching both the multiple image lensing data and the velocity
dispersion profile of the brightest cluster galaxy in MS2137-23. This suggests
that the mass model we are using, which comprises a pseudo-elliptical
generalized NFW profile and a brightest cluster galaxy component may
inadequately represent the inner cluster regions. This may plausibly arise due
to halo triaxiality or by the gravitational interaction of baryons and dark
matter in cluster cores. However, the progress made via this detailed study
highlights the key role that complementary observations of lensed features and
stellar dynamics offer in understanding the interaction between dark and
baryonic matter on non-linear scales in the central regions of clusters.Comment: 18 pages, 9 figures; accepted for publication in the Astrophysical
Journa
Phase-resolved Crab Studies with a Cryogenic TES Spectrophotometer
We are developing time- and energy-resolved near-IR/optical/UV photon
detectors based on sharp superconducting-normal transition edges in thin films.
We report observations of the Crab pulsar made during prototype testing at the
McDonald 2.7m telescope with a fiber-coupled transition-edge sensor (TES)
system. These data show substantial (d[alpha]~0.3), rapid variations in the
spectral index through the pulse profile, with a strong phase-varying IR break
across our energy band. These variations correlate with X-ray spectral
variations, but no single synchrotron population can account for the full
Spectral Energy Distribution (SED). We also describe test
spectrophotopolarimetry observations probing the energy dependence of the
polarization sweep; this may provide a new key to understanding the radiating
particle population.Comment: 12 pages, 10 figures -- to appear in ApJ V56
Unpulsed UBV Optical Emission from the Crab Pulsar
Based on observations of the Crab pulsar using the TRIFFID high speed imaging
photometer in the UBV bands using the Special Astrophysical Observatory's 6m
telescope in the Russian Caucasus, we report the detection of pronounced
emission during the so-called `off' phase of emission. Following de-extinction,
this unpulsed component of emission is shown to be consistent with a power law
with an exponent of alpha = -0.60 +/- 0.37, the uncertainty being dominated by
the error associated with the independent CCD photometry used to reference the
TRIFFID data. This suggests a steeper power law form than that reported
elsewhere in the literature for the total integrated spectrum, which is
essentially flat with alpha ~ 0.1, although the difference in this case is only
significant at the ~ 2 sigma level. Deeper reference integrated and TRIFFID
phase-resolved photometry in these bands in conjunction with further
observations in the UV and R region would constrain this fit further.Comment: 26 pages, 2 figures, uses aasms4.sty, accepted for publication in the
Astrophysical Journa
Enhanced oligonucleotide–nanoparticle conjugate stability using thioctic acid modified oligonucleotides
Metallic nanoparticles of gold functionalized with oligonucleotides conventionally use a terminal thiol modification and have been used in a wide range of applications. Although readily available, the oligonucleotide–nanoparticle conjugates prepared in this way suffer from a lack of stability when exposed to a variety of small molecules or elevated temperatures. If silver is used in place of gold then this lack of stability is even more pronounced. In this study we report the synthesis of highly stabilized oligonucleotide–nanoparticle conjugates using a simple oligonucleotide modification. A modified solid support was used to generate 3′-thioctic acid modified oligonucleotides by treatment with an N-hydroxysuccimidyl ester of thioctic acid. Unusually, both gold and silver nanoparticles have been investigated in this study and show that these disulphide-modified oligonucleotide probes offer significant improvements in nanoparticle stability when treated with dithiothreitol (DTT) compared with monothiol analogues. This is a significant advance in oligonucleotide–nanoparticle conjugate stability and for the first time allows silver nanoparticles to be prepared that are more stable than standard gold-thiol functionalized nanoparticles. This opens up the possibility of using silver nanoparticles functionalized with oligonucleotides as an alternative to gold
Enhanced oligonucleotide–nanoparticle conjugate stability using thioctic acid modified oligonucleotides
Metallic nanoparticles of gold functionalized with oligonucleotides conventionally use a terminal thiol modification and have been used in a wide range of applications. Although readily available, the oligonucleotide–nanoparticle conjugates prepared in this way suffer from a lack of stability when exposed to a variety of small molecules or elevated temperatures. If silver is used in place of gold then this lack of stability is even more pronounced. In this study we report the synthesis of highly stabilized oligonucleotide–nanoparticle conjugates using a simple oligonucleotide modification. A modified solid support was used to generate 3′-thioctic acid modified oligonucleotides by treatment with an N-hydroxysuccimidyl ester of thioctic acid. Unusually, both gold and silver nanoparticles have been investigated in this study and show that these disulphide-modified oligonucleotide probes offer significant improvements in nanoparticle stability when treated with dithiothreitol (DTT) compared with monothiol analogues. This is a significant advance in oligonucleotide–nanoparticle conjugate stability and for the first time allows silver nanoparticles to be prepared that are more stable than standard gold-thiol functionalized nanoparticles. This opens up the possibility of using silver nanoparticles functionalized with oligonucleotides as an alternative to gold
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