1,459 research outputs found
Individual Scores for Associative Learning in a Differential Appetitive Olfactory Paradigm Using Binary Logistic Regression Analysis
Numerous invertebrates have contributed to our understanding of the biology of learning
and memory. In most cases, learning performance is documented for groups of
individuals, and nearly always based on a single, typically binary, behavioural metric
for a conditioned response. This is unfortunate for several reasons. Foremost, it has
become increasingly apparent that invertebrates exhibit inter-individual differences in
many aspects of their behaviour, and also that the conditioned response probability for
an animal group does not adequately represent the behaviour of individuals in classical
conditioning. Furthermore, a binary response character cannot yield a graded score
for each individual. We also hypothesise that due to the complexity of a conditioned
response, a single metric need not reveal an individual’s full learning potential. In this
paper, we report individual learning scores for freely moving adult male crickets (Gryllus
bimaculatus) based on a multi-factorial analysis of a conditioned response. First, in an
absolute conditioning paradigm, we video-tracked the odour responses of animals that,
in previous training, received either odour plus reward (sugar water), reward alone, or
odour alone to identify behavioural predictors of a conditioned response. Measures of
these predictors were then analysed using binary regression analysis to construct a
variety of mathematical models that give a probability for each individual that it exhibited
a conditioned response (Presp). Using standard procedures to compare model accuracy,
we identified the strongest model which could reliably discriminate between the different
odour responses. Finally, in a differential appetitive olfactory paradigm, we employed
the model after training to calculate the Presp of animals to a conditioned, and to
an unconditioned odour, and from the difference a learning index for each animal.
Comparing the results from our multi-factor model with a single metric analysis (head
bobbing in response to a conditioned odour), revealed advantageous aspects of the
model. A broad distribution of model-learning scores, with modes at low and high values,
support the notion of a high degree of variation in learning capacity, which we discuss
Buoyant melting instabilities beneath extending lithosphere: 1. Numerical models
Buoyant decompression melting instabilities in regions of partially molten upper mantle have been proposed to be an important process that might account for some characteristics of intraplate volcanism on Earth and other terrestrial planets. The instability is driven by variations in the melting rate within a partially molten layer whenever a relative decrease in density accompanies decompression melting of ascending mantle. Here, the development of buoyant decompression melting instabilities in a plane layer of passively upwelling and partially melting mantle beneath diffusely extending lithosphere is studied using numerical convection models covering a wide range of physical parameters. We find that the occurrence and nature of these instabilities in such a scenario is strongly affected by the rate of extension and melt percolation, as well as depth distribution of solid density variations arising from melt depletion. In some cases, instabilities do not occur during extension, but only develop after extension has slowed or stopped completely. This behavior creates two pulses of magma generation due to passive upwelling accompanying extension followed by the subsequent instability and is favored by a faster rate of extension, higher mantle viscosity, higher rate of melt percolation, and smaller amount of solid residuum depletion‐derived buoyancy. Larger degrees of solid density changes accompanying melt depletion can enhance the instability of partially molten mantle during extension but decrease the cumulative volume of generated melt. This kind of behavior modifies the conventional expectation of spatially and temporally correlated volcanism and extension and may lend insight into the observed increase in localized volcanic activity following Miocene Basin and Range extension in the western United States
Buoyant melting instabilities beneath extending lithosphere: 2. Linear analysis
In a companion paper, numerical models reveal that buoyant melting instabilities can occur beneath extending lithosphere for a sufficiently small mantle viscosity, extension rate, and rate of melt percolation. However, in some cases, instabilities do not develop during extension but only occur after extension slows or stops. These results are suggestive of a critical behavior in the onset of these kinds of instabilities and motivate a linear analysis to study the onset of instability in a partially melting, passively upwelling plane layer of mantle beneath extending lithosphere. The model we employ includes the effects of buoyancy arising from thermal expansion, the presence of a retained fraction of partial melt, and depletion of the solid by melt extraction. We find a critical behavior in the onset of instability controlled by melt retention buoyancy that is characterized by a “Rayleigh” number M, such that M must exceed some critical value M_(crit) which depends on the efficiency of Stokes rise of a partially molten body relative to the rate of background percolation. Comparison of this theory to the numerical results in the companion paper yields a close quantitative agreement. We also find that solid depletion buoyancy can either stabilize or destabilize a partially melting layer, depending upon both the distribution of preexisting depletion and the magnitude of density changes with depth. This theory is compared with previous studies of buoyant melting instabilities beneath mid‐ocean ridges where similar behavior was reported, and it suggests that the stability of passively upwelling, partially melting mantle underlying both narrow and wide rift settings is controlled by similar processes
An Integrated Content and Metadata based Retrieval System for Art
In this paper we describe aspects of the Artiste project to develop a distributed content and metadata based analysis, retrieval and navigation system for a number of major European Museums. In particular, after a brief overview of the complete system, we describe the design and evaluation of some of the image analysis algorithms developed to meet the specific requirements of the users from the museums. These include a method for retrievals based on sub images, retrievals based on very low quality images and retrieval using craquelure type
Estimating the effect of Earth elasticity and variable water density on tsunami speeds
The speed of tsunami waves is typically calculated using the shallow-water approximation over a rigid-body Earth. Recent comparisons of tsunami arrival times from the 11 March 2011 tsunami suggest, however, that the standard formulation has errors around the 1% level, and it has been suggested that the elasticity of the Earth can explain the discrepancy. While previous work has indeed shown that such elastic deformation can modify tsunami speeds, the effect has been neglected partly due to the difficulty in understanding how large this elastic effect is. Here, we remedy this by providing a new derivation and expression for how to incorporate the first-order effect that solid Earth elasticity and ocean water compressibility have on tsunami speeds. This result is shown to agree approximately with previous theory and helps to explain observed timing discrepancies from the 11 March 2011 tsunami. The dispersive elastic correction and the non-dispersive compressibility correction together may account for the majority of the observed discrepancy
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PATHS in Context: User Characteristics and the Construction of Cultural Heritage Narratives
There is ample evidence of the influence of individual differences on information-seeking behaviours. Trailways and paths are increasingly important objects to support internet navigation. The EU-funded PATHS (Personalised Access to Cultural Heritage) project is investigating ways of assisting users with exploring a large collection of cultural heritage material taken from Europeana, the European aggregator for museums, archives, libraries, and galleries. A prototype system has been developed that includes innovative functionality for exploring the collection based on Google map-style interfaces, data-driven taxonomies, and supporting the manual creation of guided tours or paths along with the use of personalised (and nonpersonalised) recommendations to promote information discovery. After analysing the paths created by participants during an extended user evaluation, this paper discusses the effect of individual differences on path creation and characteristics
Poverty and Wealth without a Ladder? An Appraisal of the Stages of Progress Method among Agro–Pastoralists in Ethiopia’s Lower Omo Valley
Is it possible to measure wealth and poverty across settings while being faithful to local understandings? The stages of progress method (SoP) attempts to do this by building ladders of wealth in locally relevant terms and using these in comparisons across groups. This approach is potentially useful among pastoralist populations where monetary income and standard asset inventories may be misleading, and where people are discriminated against by the state and neglected by formal systems of accounting. On the basis of fieldwork among Nyangatom agro–pastoralists in Ethiopia, we expose some problematic assumptions of the SoP method. Participants did not endorse ladder-like stages from poverty to wealth distinguished by material assets, nor did they reach consensus on the definition of a poverty line. We caution that the SoP method carries risks of facipulation, and instead we advocate for multidimensional measures of prosperity based on locally relevant forms of wealth
PATHS in Context: User Characteristics and the Construction of Cultural Heritage Narratives
There is ample evidence of the influence of individual differences on information-seeking behaviours. Trailways and paths are increasingly important objects to support internet navigation. The EU-funded PATHS (Personalised Access to Cultural Heritage) project is investigating ways of assisting users with exploring a large collection of cultural heritage material taken from Europeana, the European aggregator for museums, archives, libraries, and galleries. A prototype system has been developed that includes innovative functionality for exploring the collection based on Google map-style interfaces, data-driven taxonomies, and supporting the manual creation of guided tours or paths along with the use of personalised (and nonpersonalised) recommendations to promote information discovery. After analysing the paths created by participants during an extended user evaluation, this paper discusses the effect of individual differences on path creation and characteristics
Genetic background influences tumour development in heterozygous Men1 knockout mice
Multiple endocrine neoplasia type 1 (MEN1), an autosomal dominant disorder caused by MEN1 germline mutations, is characterised by parathyroid, pancreatic and pituitary tumours. MEN1 mutations also cause familial isolated primary hyperparathyroidism (FIHP), a milder condition causing hyperparathyroidism only. Identical mutations can cause either MEN1 or FIHP in different families, thereby implicating a role for genetic modifiers in altering phenotypic expression of tumours. We therefore investigated the effects of genetic background and potential for genetic modifiers on tumour development in adult Men1+/- mice, which develop tumours of the parathyroids, pancreatic islets, anterior pituitary, adrenal cortex and gonads, that had been backcrossed to generate C57BL/6 and 129S6/SvEv congenic strains. A total of 275 Men1+/- mice, aged 5–26 months were macroscopically studied, and this revealed that genetic background significantly influenced the development of pituitary, adrenal and ovarian tumours, which occurred in mice over 12 months of age and more frequently in C57BL/6 females, 129S6/SvEv males and 129S6/SvEv females, respectively. Moreover, pituitary and adrenal tumours developed earlier, in C57BL/6 males and 129S6/SvEv females, respectively, and pancreatic and testicular tumours developed earlier in 129S6/SvEv males. Furthermore, glucagon-positive staining pancreatic tumours occurred more frequently in 129S6/SvEv Men1+/- mice. Whole genome sequence analysis of 129S6/SvEv and C57BL/6 Men1+/- mice revealed >54,000 different variants in >300 genes. These included, Coq7, Dmpk, Ccne2, Kras, Wnt2b, Il3ra and Tnfrsf10a, and qRT-PCR analysis revealed that Kras was significantly higher in pituitaries of male 129S6/SvEv mice. Thus, our results demonstrate that Kras and other genes could represent possible genetic modifiers of Men1
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