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Search Results: 1 - 10 of 301400 matches for " Marcus J. Byrne "
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The Dung Beetle Dance: An Orientation Behaviour?
Emily Baird,Marcus J. Byrne,Jochen Smolka,Eric J. Warrant,Marie Dacke
PLOS ONE , 2012, DOI: 10.1371/journal.pone.0030211
Abstract: An interesting feature of dung beetle behaviour is that once they have formed a piece of dung into a ball, they roll it along a straight path away from the dung pile. This straight-line orientation ensures that the beetles depart along the most direct route, guaranteeing that they will not return to the intense competition (from other beetles) that occurs near the dung pile. Before rolling a new ball away from the dung pile, dung beetles perform a characteristic “dance,” in which they climb on top of the ball and rotate about their vertical axis. This dance behaviour can also be observed during the beetles' straight-line departure from the dung pile. The aim of the present study is to investigate the purpose of the dung beetle dance. To do this, we explored the circumstances that elicit dance behaviour in the diurnal ball-rolling dung beetle, Scarabaeus (Kheper) nigroaeneus. Our results reveal that dances are elicited when the beetles lose control of their ball or lose contact with it altogether. We also find that dances can be elicited by both active and passive deviations of course and by changes in visual cues alone. In light of these results, we hypothesise that the dung beetle dance is a visually mediated mechanism that facilitates straight-line orientation in ball-rolling dung beetles by allowing them to 1) establish a roll bearing and 2) return to this chosen bearing after experiencing a disturbance to the roll path.
Xenopus laevis embryos and tadpoles as models for testing for pollution by zinc, copper, lead and cadmium
Lorren K. Haywood,Graham J. Alexander,Marcus J. Byrne,Ewa Cukrowska
African Zoology , 2011,
Abstract: The toxicity of bio-available Zn, Cu, Pb, and Cd on the life stages ofXenopus laevis embryos and tadpoles was investigated. Cu and Cd were found to affect the hatching success of the embryos, with a strong negative relationship existing between the increase in Cu concentrations and the hatching of the embryos. Only concentrations above 0.6 ppm Cd affected the hatching of the embryos. All metals affected the survival of tadpoles over the seven days of exposure, with Zn and Cu showing a steady linear toxicity and Pb and Cd a threshold toxicity effect. Metals affected the growth of the tadpoles by reducing body length with increasing concentrations. An increase in the concentration of each metal resulted in an increase in the frequency and severity of malformations among the tadpoles. The percentage of malformed tadpoles was dependent on the metal and concentration to which they were exposed. Our data describe the relationships among hatching success, survival, growth rate and the frequency of malformations of tadpoles in relation to different concentrations of the four metals. Xenopus laevis embryos and tadpoles can be used successfully in bioassays to biologically quantify the severity of Zn, Cu, Pb and Cd pollution.
A Technical Review of Penning Trap based Investigations in Neutron Decay
J. Byrne
Physics , 2014,
Abstract: This review is concerned with a detailed analysis of some of the technical problems which arise in the application of the Penning trap method to the experimental study of neutron $\beta $ -decay,a technique which was first successfully tested on the low-flux swimming-pool reactor LIDO (capture flux =3$\cdot 10^6$cm$^(-2)$s$^(-1)$) at AERE Harwell in the 1970's. It does not discuss the scientific merits or demerits of these studies. Of particular importance are the trapping and release of neutron decay protons, and the influence of magnetic mirror effects and radial drifting on the trapped particles. Since these have energies < 1 keV they must be accelerated to energies of order 20-30 keV following release, at which point they are recorded in a silicon surface barrier detector. However serious difficulties were encountered in the post-release acceleration process with vacuum breakdown in the presence of crossed electric and magnetic fields.
Update of cholangioscopy and biliary strictures
Marcus W Chin,Michael F Byrne
World Journal of Gastroenterology , 2011, DOI: 10.3748/wjg.v17.i34.3864
Abstract: Cholangioscopy remains another modality in the investigation of biliary strictures. At cholangioscopy, the “tumour vessel” sign is considered a specific sign for malignancy. Through its ability to not only visualise mucosa, but to take targeted biopsies, it has a greater accuracy, sensitivity and specificity for malignant strictures than endoscopic retrograde cholangiopancreatography guided cytopathological acquisition. Cholangioscopy however, is time consuming and costly, requires greater technical expertise, and should be reserved for the investigation of undifferentiated strictures after standard investigations have failed.
Episodic Learning and Memory in Prodromal Huntington’s Disease: The Role of Multimodal Encoding and Selective Reminding  [PDF]
Tarja-Brita Robins Wahlin, ?ke Wahlin, Gerard J. Byrne
International Journal of Clinical Medicine (IJCM) , 2015, DOI: 10.4236/ijcm.2015.611115
Abstract: This study investigated episodic memory in prodromal HD. Three groups were compared (N = 70): mutation carriers with less than 12.5 years to disease onset (n = 16), mutation carriers with 12.5 or more years to disease onset (n = 16), and noncarriers (n = 38). Episodic memory was assessed using the Fuld Object Memory Evaluation, which included multimodal presentation and selective reminding, and the Claeson-Dahl Learning Test which included verbal repeated presentation and recall trials. Both carrier groups demonstrated deficient episodic memory compared to noncarriers. The results suggest deficient episodic memory in prodromal HD, and that inconsistent retrieval contributes to these deficits. Multimodal presentation attenuates the deficits.
Linear-programming Decoding of Non-binary Linear Codes
Mark F. Flanagan,Vitaly Skachek,Eimear Byrne,Marcus Greferath
Mathematics , 2007,
Abstract: We develop a framework for linear-programming (LP) decoding of non-binary linear codes over rings. We prove that the resulting LP decoder has the `maximum likelihood certificate' property, and we show that the decoder output is the lowest cost pseudocodeword. Equivalence between pseudocodewords of the linear program and pseudocodewords of graph covers is proved. LP decoding performance is illustrated for the (11,6,5) ternary Golay code with ternary PSK modulation over AWGN, and in this case it is shown that the LP decoder performance is comparable to codeword-error-rate-optimum hard-decision based decoding.
Polytope Representations for Linear-Programming Decoding of Non-Binary Linear Codes
Vitaly Skachek,Mark F. Flanagan,Eimear Byrne,Marcus Greferath
Mathematics , 2007,
Abstract: In previous work, we demonstrated how decoding of a non-binary linear code could be formulated as a linear-programming problem. In this paper, we study different polytopes for use with linear-programming decoding, and show that for many classes of codes these polytopes yield a complexity advantage for decoding. These representations lead to polynomial-time decoders for a wide variety of classical non-binary linear codes.
Linear-Programming Decoding of Nonbinary Linear Codes
Mark F. Flanagan,Vitaly Skachek,Eimear Byrne,Marcus Greferath
Mathematics , 2008,
Abstract: A framework for linear-programming (LP) decoding of nonbinary linear codes over rings is developed. This framework facilitates linear-programming based reception for coded modulation systems which use direct modulation mapping of coded symbols. It is proved that the resulting LP decoder has the 'maximum-likelihood certificate' property. It is also shown that the decoder output is the lowest cost pseudocodeword. Equivalence between pseudocodewords of the linear program and pseudocodewords of graph covers is proved. It is also proved that if the modulator-channel combination satisfies a particular symmetry condition, the codeword error rate performance is independent of the transmitted codeword. Two alternative polytopes for use with linear-programming decoding are studied, and it is shown that for many classes of codes these polytopes yield a complexity advantage for decoding. These polytope representations lead to polynomial-time decoders for a wide variety of classical nonbinary linear codes. LP decoding performance is illustrated for the [11,6] ternary Golay code with ternary PSK modulation over AWGN, and in this case it is shown that the performance of the LP decoder is comparable to codeword-error-rate-optimum hard-decision based decoding. LP decoding is also simulated for medium-length ternary and quaternary LDPC codes with corresponding PSK modulations over AWGN.
New Bounds for Codes Over Finite Frobenius Rings
Eimear Byrne,Marcus Greferath,Axel Kohnert,Vitaly Skachek
Mathematics , 2009,
Abstract: We give results on the question of code optimality for linear codes over finite Frobenius rings for the homogeneous weight. This article improves on the existing Plotkin bound derived in an earlier paper, and suggests a version of a Singleton bound. We also present some families of codes meeting these new bounds.
Algebraic Decoding of Negacyclic Codes Over Z_4
Eimear Byrne,Marcus Greferath,Jaume Pernas,Jens Zumbr?gel
Mathematics , 2011,
Abstract: In this article we investigate Berlekamp's negacyclic codes and discover that these codes, when considered over the integers modulo 4, do not suffer any of the restrictions on the minimum distance observed in Berlekamp's original papers. The codes considered here have minimim Lee distance at least 2t+1, where the generator polynomial of the code has roots z,z^3,...,z^{2t+1} for a primitive 2nth root of unity z in a Galois extension of Z4. No restriction on t is imposed. We present an algebraic decoding algorithm for this class of codes that corrects any error pattern of Lee weight at most t. Our treatment uses Grobner bases and the decoding complexity is quadratic in t.
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