981 research outputs found
Anticipatory eye movements evoked after active following versus passive observation of a predictable motion stimulus.
We used passive and active following of a predictable smooth pursuit stimulus in order to establish if predictive eye movement responses are equivalent under both passive and active conditions. The smooth pursuit stimulus was presented in pairs that were either âpredictableâ in which both presentations were matched in timing and velocity, or ârandomizedâ in which each presentation in the pair was varied in both timing and velocity. A visual cue signaled the type of response required from the subject; a green cue indicated the subject should follow both the target presentations (Go-Go), a pink cue indicated that the subject should passively observe the 1st target and follow the 2nd target (NoGo-Go), and finally a green cue with a black cross revealed a randomized (Rnd) trial in which the subject should follow both presentations. The results revealed better prediction in the Go-Go trials than in the NoGo-Go trials, as indicated by higher anticipatory velocity and earlier eye movement onset (latency). We conclude that velocity and timing information stored from passive observation of a moving target is diminished when compared to active following of the target. This study has significant consequences for understanding how visuomotor memory is generated, stored and subsequently released from short-term memory
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Form finding and analysis of tension space structures by dynamic relaxation
The thesis is submitted on the basis of papers published between April, 1974 and July, 1976 (chapters 2-8). Minor editing of the papers has been carried out for the sake of continuity of the thesis as a whole. Since each of the papers was written to be largely self-contained, however, a certain amount of repetition, particular to introductory remarks, is unavoidable. For this reason the "contents" lists only those sections which introduce new material. Chapter appendices have been placed immediately following the papers to which they refer. In the majority of cases these were not included with the original texts, but have been added here to expand on points mentioned in the papers or dealt with during presentation. The report supporting the submission is given in two sections: an introduction reviewing the behaviour and analytical requirements of tension structures which relates subsequent chapters to other publications, and a conclusion correlating the papers into an overall context of interactive design and analysis. For the sake of completeness as a thesis, main appendices A-D have been included at the end of the thesis to give comprehensive reviews of published work relating respectively to static analysis, form: -finding, dynamic analy1sis, and the development and mathematical basis of dynamic relaxation. References in these appendices and the introduction (chapter 1) are contained in the main bibliography, appendix E
Relationship between microstructures and grain-scale trace element distribution in komatiite-hosted magmatic sulphide ores
Komatiite-hosted nickel sulphides from the Yilgarn Craton (Australia) consist of two main sulphide phases: pyrrhotite (Fe7S8) and pentlandite ((Fe,Ni)9S8); two minor sulphide phases: chalcopyrite (CuFeS2) and pyrite (FeS2) and trace arsenides. Samples of massive sulphides from three deposits with diverse deformation and metamorphic histories (the Silver Swan, Perseverance and Flying Fox deposits) have been studied by electron backscatter diffraction and laser ablation inductively coupled plasma mass spectrometry and nano-scale secondary ion mass spectrometry. These ore bodies were selected to investigate the relationship between microstructures and mineral trace element chemistry in three dominant sulphide species in each deposit. In all three samples, pyrrhotite preserves a strong evidence of crystal plasticity relative to both pentlandite and pyrite. The trace element composition of pyrrhotite shows significant variation in specific elements (Pb, Bi and Ag). This variation correlates spatially with intragrain pyrrhotite microstructures, such as low angle and twin boundaries. Minor signatures of crystal plasticity in pyrite and pentlandite occur in the form of rare low angle boundaries (pentlandite) and mild lattice misorientation (pyrite). Trace element compositions of pentlandite and pyrite show no correlation with microstructures.Variations in pyrrhotite are interpreted as a result of intragrain diffusion during the syn- and post-deformation history of the deposit. Intragrain diffusion can occur either due to bulk diffusion, dislocationâimpurity pair diffusion, or by âpipe diffusionâ, i.e. along fast diffusion pathways at high and low angle, and twin boundaries. This contribution examines three different diffusion models and suggests that dislocationâimpurity pair diffusion and pipe diffusion are the most likely processes behind increased trace element concentration along the microstructures in pyrrhotite. The same phenomenon is observed in samples from three different deposits that experienced widely different metamorphic conditions, implying that the final disposition of these elements reflects a post peak-metamorphic stage of the geological history of all three deposits
Understanding Earthâ Ocean Processes using Real-time Data from NEPTUNE, Canadaâs Widely Distributed Sensor Networks, Northeast Pacific
After several years of planning, NEPTUNE Canada [www.neptunecanada.ca], as part of the Ocean Networks Canada Observatory, largely completed the installation of the worldâs first regional cabled observatory network in 2009. The 800 km cable loop west of Vancouver Island connects five nodes in coastal, continental slope, abyssal plain and spreading-ridge environments. Abundant power and high-bandwidth communications support a network of hundreds of sensors that deliver data and imagery in real- or near real-time, and will transform our knowledge of the ocean environment and interacting processes. With the worldâs oceans and climate in a state of crisis, the development of cabled observatory technologies is most timely and offers a growing data archive of unparalleled importance for new discoveries.
Sommaire
Apres plusieurs annĂ©es de planification, lâessentiel du premier reseau observatoire rĂ©gional, NEPTUNE Canada [www.neptunecanada.ca], partie intĂ©grante du Ocean Network Observatory, a Ă©tĂ© installĂ© en 2009. Ses 800km de cable forment une boucle Ă lâ Ouest de lâ Isle de Vancouver et sont connectĂ©s Ă cinq noeuds situĂ©s au niveau de la zone cotiĂšre, du talus continental, de la plaine abyssale et de la dorsale ocĂ©anique. Grace Ă cet acces Ă lâ Ă©nergie et la communication Ă haut dĂ©bit, un rĂ©seau de centaines de capteurs transmettent des donnĂ©es et images en temps rĂ©el ou quasi rĂ©el, qui transformeront nos connaissances du mileu et processus ocĂ©aniques. Alors que les ocĂ©ans et le climat sont en Ă©tat de stress, le dĂ©velopment des technologies liĂ©es aux observatoires sous marins reprĂ©sente une opportunitĂ© exceptionelle et un recueil de donnĂ©es sans cesse croissant et dâ un potentiel inĂ©galĂ© pour permettre de nouvelles dĂ©couvertes
Illuminating hadron structure by scattering light on light
The results of an Amplitude Analysis of the world data on integrated and
differential cross-sections on are presented, following
the publication of the Belle charged pion results.Comment: 5 pages, 7 figures. To appear in the Proceedings of the International
Workshop on collisions from to , Frascati, April 2008.
This version rewords the reference to the work of Achasov and Shestakov, with
apologies to them for any misunderstandin
Exclusive channels in reactions: light at the end of the tunnel?
The physics that can be learnt by studying exclusive channels in two photon
interactions is recalled. This serves as an introduction to the Exclusive
Reaction session of Photon'99.Comment: 9 pages,8 figures. Invited introductory talk at Photon'99, Freiburg
im Br., Germany, May 199
Fokker-Planck Equation for Boltzmann-type and Active Particles: transfer probability approach
Fokker-Planck equation with the velocity-dependent coefficients is considered
for various isotropic systems on the basis of probability transition (PT)
approach. This method provides the self-consistent and universal description of
friction and diffusion for Brownian particles. Renormalization of the friction
coefficient is shown to occur for two dimensional (2-D) and three dimensional
(3-D) cases, due to the tensorial character of diffusion. The specific forms of
PT are calculated for the Boltzmann-type of collisions and for the
absorption-type of collisions (the later are typical for dusty plasmas and some
other systems). Validity of the Einstein's relation for the Boltzmann-type
collisions is analyzed for the velocity-dependent friction and diffusion
coefficients. For the Boltzmann-type collisions in the region of very high
grain velocity as well as it is always for non-Boltzmann collisions, such as,
e.g., absorption collisions, the Einstein relation is violated, although some
other relations (determined by the structure of PT) can exist. The generalized
friction force is investigated in dusty plasma in the framework of the PT
approach. The relation between this force, negative collecting friction force
and scattering and collecting drag forces is established.+AFwAXA- The concept
of probability transition is used to describe motion of active particles in an
ambient medium. On basis of the physical arguments the PT for a simple model of
the active particle is constructed and the coefficients of the relevant
Fokker-Planck equation are found. The stationary solution of this equation is
typical for the simplest self-organized molecular machines.+AFwAXA- PACS
number(s): 52.27.Lw, 52.20.Hv, 52.25.Fi, 82.70.-yComment: 18 page
Influence of constitution and charge on radical pairing interactions in tris-radical tricationic complexes
The results of a systematic investigation of trisradical tricationic complexes formed between cyclobis(paraquat-p-phenylene) bisradical dicationic (CBPQT2(âą+)) rings and a series of 18 dumbbells, containing centrally located 4,4âČ-bipyridinium radical cationic (BIPYâą+) units within oligomethylene chains terminated for the most part by charged 3,5-dimethylpyridinium (PY+) and/or neutral 3,5-dimethylphenyl (PH) groups, are reported. The complexes were obtained by treating equimolar amounts of the CBPQT4+ ring and the dumbbells containing BIPY2+ units with zinc dust in acetonitrile solutions. Whereas UVâVisâNIR spectra revealed absorption bands centered on ca. 1100 nm with quite different intensities for the 1:1 complexes depending on the constitutions and charges on the dumbbells, titration experiments showed that the association constants (Ka) for complex formation vary over a wide range, from 800 Mâ1 for the weakest to 180âŻ000 Mâ1 for the strongest. While Coulombic repulsions emanating from PY+ groups located at the ends of some of the dumbbells undoubtedly contribute to the destabilization of the trisradical tricationic complexes, solid-state superstructures support the contention that those dumbbells with neutral PH groups at the ends of flexible and appropriately constituted links to the BIPYâą+ units stand to gain some additional stabilization from CâHÂ·Â·Â·Ï interactions between the CBPQT2(âą+) rings and the PH termini on the dumbbells. The findings reported in this Article demonstrate how structural changes implemented remotely from the BIPYâą+ units influence their non-covalent bonding interactions with CBPQT2(âą+) rings. Different secondary effects (Coulombic repulsions versus CâHÂ·Â·Â·Ï interactions) are uncovered, and their contributions to both binding strengths associated with trisradical interactions and the kinetics of associations and dissociations are discussed at some length, supported by extensive DFT calculations at the M06-D3 level. A fundamental understanding of molecular recognition in radical complexes has relevance when it comes to the design and synthesis of non-equilibrium systems
Boundary Liouville theory at c=1
The c=1 Liouville theory has received some attention recently as the
Euclidean version of an exact rolling tachyon background. In an earlier paper
it was shown that the bulk theory can be identified with the interacting c=1
limit of unitary minimal models. Here we extend the analysis of the c=1-limit
to the boundary problem. Most importantly, we show that the FZZT branes of
Liouville theory give rise to a new 1-parameter family of boundary theories at
c=1. These models share many features with the boundary Sine-Gordon theory, in
particular they possess an open string spectrum with band-gaps of finite width.
We propose explicit formulas for the boundary 2-point function and for the
bulk-boundary operator product expansion in the c=1 boundary Liouville model.
As a by-product of our analysis we also provide a nice geometric interpretation
for ZZ branes and their relation with FZZT branes in the c=1 theory.Comment: 37 pages, 1 figure. Minor error corrected, slight change in result
(1.6
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