921 resultados para Invariance principle
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An unresolved goal in face perception is to identify brain areas involved in face processing and simultaneously understand the timing of their involvement. Currently, high spatial resolution imaging techniques identify the fusiform gyrus as subserving processing of invariant face features relating to identity. High temporal resolution imaging techniques localize an early latency evoked component—the N/M170—as having a major generator in the fusiform region; however, this evoked component is not believed to be associated with the processing of identity. To resolve this, we used novel magnetoencephalographic beamformer analyses to localize cortical regions in humans spatially with trial-by-trial activity that differentiated faces and objects and to interrogate their functional sensitivity by analyzing the effects of stimulus repetition. This demonstrated a temporal sequence of processing that provides category-level and then item-level invariance. The right fusiform gyrus showed adaptation to faces (not objects) at ∼150 ms after stimulus onset regardless of face identity; however, at the later latency of ∼200–300 ms, this area showed greater adaptation to repeated identity faces than to novel identities. This is consistent with an involvement of the fusiform region in both early and midlatency face-processing operations, with only the latter showing sensitivity to invariant face features relating to identity.
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We present a technique for an all-digital on-chip delay measurement system to measure the skews in a clock distribution network. It uses the principle of sub-sampling. Measurements from a prototype fabricated in a 65 nm industrial process, indicate the ability to measure delays with a resolution of 0.5ps and a DNL of 1.2 ps.
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Background: Biomechanical stresses play an important role in determining plaque stability. Quantification of these simulated stresses can be potentially used to assess plaque vulnerability and differentiate different patient groups. Methods and Results: 54 asymptomatic and 45 acutely symptomatic patients underwent in vivo multicontrast magnetic resonance imaging (MRI) of the carotid arteries. Plaque geometry used for finite element analysis was derived from in vivo MRI at the sites of maximum and minimum plaque burden. In total, 198 slices were used for the computational simulations. A pre-shrink technique was used to refine the simulation. Maximum principle stress at the vulnerable plaque sites (ie, critical stress) was extracted for the selected slices and a comparison was performed between the 2 groups. Critical stress in the slice with maximum plaque burden is significantly higher in acutely symptomatic patients as compared to asymptomatic patients (median, inter quartile range: 198.0 kPa (119.8-359.0 kPa) vs 138.4 kPa (83.8-242.6 kPa), P=0.04). No significant difference was found in the slice with minimum plaque burden between the 2 groups (196.7 kPa (133.3-282.7 kPa) vs 182.4 kPa (117.2-310.6 kPa), P=0.82). Conclusions: Acutely symptomatic carotid plaques have significantly high biomechanical stresses than asymptomatic plaques. This might be potentially useful for establishing a biomechanical risk stratification criteria based on plaque burden in future studies.
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Stress analysis within carotid plaques based on in vivo MR imaging has shown to be useful for the identification of vulnerable atheroma. This study is to investigate whether magnetic resonance imaging (MRI) based-biomechanical stress analysis of carotid plaques can differentiate acute symptomatic and asymptomatic patients. 54 asymptomatic and 45 acute symptomatic patients underwent in vivo multi-contrast MRI of the carotid arteries. Plaque geometry used for finite element analysis was derived from in vivo MR images at the site of maximum and minimum plaque burden. In total 198 slices were used for the computational simulations. A pre shrink technique was used to refine the simulation. Maximum principle stress at the vulnerable plaque sites (i.e. critical stress) was extracted for the selected slices and a comparison was performed between the two groups. Critical stress at the site of maximum plaque burden is significantly higher in acute symptomatic patients as compared to asymptomatic patients [median: 198.0kPa (inter quartile range (IQR) = (119.8 - 359.0) vs. 138.4kPa (83.8, 242.6), p=0.04]. No significant difference was found at the minimum plaque burden site between the two groups [196.7kPa (133.3- 282.7) vs. 182.4kPa (117.2 - 310. 6), p=0.82). Stress analysis at the site of maximal plaque burden can be effectively used for differentiating acute symptomatic carotid plaques from asymptomatic plaques. This maybe potentially used for development of biomechanical risk stratification criteria based on plaque burden in future studies.
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We propose a new scheme for the use of constraints in setting up classical, Hamiltonian, relativistic, interacting particle theories. We show that it possesses both Poincaré invariance and invariance of world lines. We discuss the transition to the physical phase space and the nonrelativistic limit.
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We present relativistic, classical particle models that possess Poincaré invariance, invariant world lines, particle interaction, and separability.
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The problem of separability in recent models of classical relativistic interacting particles is examined. This physical requirement is shown to be more subtle than naive separability of all the constraints defining the system: it is adequate to be able to canonically transform the time-fixing constraints from an unseparated to a separated form when clusters emerge. Viewing separability in this way, and within a specific framework, we are led to a new no-interaction theorem which states the incompatibility of nontrivial interaction with relativistic invariance, separability, and invariant world lines for more than two particles.
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The application of multilevel control strategies for load-frequency control of interconnected power systems is assuming importance. A large multiarea power system may be viewed as an interconnection of several lower-order subsystems, with possible change of interconnection pattern during operation. The solution of the control problem involves the design of a set of local optimal controllers for the individual areas, in a completely decentralised environment, plus a global controller to provide the corrective signal to account for interconnection effects. A global controller, based on the least-square-error principle suggested by Siljak and Sundareshan, has been applied for the LFC problem. A more recent work utilises certain possible beneficial aspects of interconnection to permit more desirable system performances. The paper reports the application of the latter strategy to LFC of a two-area power system. The power-system model studied includes the effects of excitation system and governor controls. A comparison of the two strategies is also made.
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A novel method is proposed to treat the problem of the random resistance of a strictly one-dimensional conductor with static disorder. It is suggested, for the probability distribution of the transfer matrix of the conductor, the distribution of maximum information-entropy, constrained by the following physical requirements: 1) flux conservation, 2) time-reversal invariance and 3) scaling, with the length of the conductor, of the two lowest cumulants of ζ, where = sh2ζ. The preliminary results discussed in the text are in qualitative agreement with those obtained by sophisticated microscopic theories.
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Following the method of Ioffe and Smilga, the propagation of the baryon current in an external constant axial-vector field is considered. The close similarity of the operator-product expansion with and without an external field is shown to arise from the chiral invariance of gauge interactions in perturbation theory. Several sum rules corresponding to various invariants both for the nucleon and the hyperons are derived. The analysis of the sum rules is carried out by two independent methods, one called the ratio method and the other called the continuum method, paying special attention to the nondiagonal transitions induced by the external field between the ground state and excited states. Up to operators of dimension six, two new external-field-induced vacuum expectation values enter the calculations. Previous work determining these expectation values from PCAC (partial conservation of axial-vector current) are utilized. Our determination from the sum rules of the nucleon axial-vector renormalization constant GA, as well as the Cabibbo coupling constants in the SU3-symmetric limit (ms=0), is in reasonable accord with the experimental values. Uncertainties in the analysis are pointed out. The case of broken flavor SU3 symmetry is also considered. While in the ratio method, the results are stable for variation of the fiducial interval of the Borel mass parameter over which the left-hand side and the right-hand side of the sum rules are matched, in the continuum method the results are less stable. Another set of sum rules determines the value of the linear combination 7F-5D to be ≊0, or D/(F+D)≊(7/12). .AE
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In his grammatical treatise, the Astadhyayi, Panini includes sutras that state guiding rules for the right interpretation and application of his other directly grammatical sutras. These sutras are called paribhasas. In addition to these paribhasas, the various commentaries on Panini frequently invoke supplementary paribhasas which are not stated explicitly in his Astadhyayi. These paribhasas have been a subject of study since early times after Panini and have also occupied modern scholars on Panini s grammar. In regard to most of them, it remains unsettled even today whether they are used in the Astadhyayi, where they apply, what is their role, and whether they are necessary in arriving at the desired grammatical form. Some scholars go even further and argue that none of such paribhasas were intended by Panini. This study aims to settle this question by dealing with three such of these paribhasas individually considering all the information available in the commentaries in their regard and examining the cases in which, according to commentaries, the paribhasas apply. I select the paribhasas arthavadgrahane nanarthakasya, laksanapratipadoktayoh pratipadoktasyaiva grahanam and ekadesavikrtam ananyavat, which are all considered nyayasiddha or lokanyayasiddha; they express logical and obvious principles which are found in daily life. On this basis, Paniniyas explain why Panini did not mention them in the Astadhyayi. I discuss each paribhasa separately and all the issues it involves. I present and explain the cases where the specified paribhasas are invoked in the major commentaries, the Mahabhasya, the Kasika and the Siddhantakaumudi and the arguments found in the commentaries concerning these cases. If available, I supply other solutions to the difficulties for which these paribhasas are invoked. The study aims to make the issue of these paribhasas clearer, which will help us to reach a solution to the key question, that is, whether Panini has presupposed them in his Astadhyayi. My study shows that Panini has presupposed the paribhasa ekadesavikrtam ananyavat (or a similar principle). He also may have used the paribhasa arthavadgrahane nanarthakasya (or a similar principle) as this paribhasa does not lead to undesired results. As for the paribhasa laksanapratipadoktayoh pratipadoktasyaiva grahanam (or a similar principle), the original scope of this paribhasa was clearly extended by later Paniniyas. Moreover, their interpretation of this paribhasa conflicts with Panini s procedure. If Panini has used this paribhasa, he has used it in a very limited way.
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Purpose This research investigates whether application of a community-based social marketing principle, namely increasing the visibility of a target behaviour in the community, can change social norms surrounding the behaviour. Design/methodology/approach A repeated measures quasi-experimental design was employed to evaluate the Victorian Health Promotion Foundation’s Walk to School 2013 programme, which increases the visibility of walking to and from school through programme participation to promote active transportation for primary school children. The target population for the survey were caregivers of primary school children aged between 5-12 years old. The final sample size across the three online surveys administered was 102 respondents. Findings The results suggest that the programme increased caregivers’ perceptions that children in their community walked to and from school and that walking to and from school is socially acceptable. Originality/value The study contributes to addressing the recent call for research examining the relationship between community-based social marketing principles and programme outcomes. Further, the results provide insight for enhancing the social norms approach, which has traditionally relied on changing social norms exclusively through media campaigns.
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This paper presents two approximate analytical expressions for nonlinear electric fields in the principal direction in axially symmetric (3D) and two dimensional (2D) ion trap mass analysers with apertures (holes in case of 3D traps and slits in case of 2D traps) on the electrodes. Considered together (3D and 2D), we present composite approximations for the principal unidirectional nonlinear electric fields in these ion traps. The composite electric field E has the form E = E-noaperture + E-aperture. where E-noaperture is the field within an imagined trap which is identical to the practical trap except that the apertures are missing and E-aperture is the field contribution due to apertures on the two trap electrodes. The field along the principal axis, of the trap can in this way be well approximated for any aperture that is not too large. To derive E-aperture. classical results of electrostatics have been extended to electrodes with finite thickness and different aperture shapes.E-noaperture is a modified truncated multipole expansion for the imagined trap with no aperture. The first several terms in the multipole expansion are in principle exact(though numerically determined using the BEM), while the last term is chosen to match the field at the electrode. This expansion, once Computed, works with any aperture in the practical trap. The composite field approximation for axially symmetric (3D) traps is checked for three geometries: the Paul trap, the cylindrical ion trap (CIT) and an arbitrary other trap. The approximation for 2D traps is verified using two geometries: the linear ion trap (LIT) and the rectilinear ion trap (RIT). In each case, for two aperture sizes (10% and 50% of the trap dimension), highly satisfactory fits are obtained. These composite approximations may be used in more detailed nonlinear ion dynamics Studies than have been hitherto attempted. (C) 2009 Elsevier B.V. All rights reserved.
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The study is dedicated to the Russian poet and prose writer Anatolii Borisovich Mariengof (1897–1962). Mariengof – “the last dandy of the Republic” – was one of the leaders and main theoreticians in the poetic group of the Russian Imaginists. For his contemporaries, he was an Imaginist par excellence. His Imaginist principles – in theory and practice – are applied to the study of his first fictional novel, Cynics (1928), which served as an epilogue for his Imaginist period (1918–1928). The novel was not published in the Soviet Union until 1988. The method used in the study is a conceptual and literary historical reading, making use of the contemporary semiotic understanding of cultural mechanisms and of intertextual analysis. There are three main concepts used throughout the study: dandy, montage and catachresis. In the first chapter, the history, practice and theory of the Russian Imaginism are analyzed from the point of view of dandyism. The Imaginist theatricalisation of life is juxtaposed with the thematic analysis of their poetry, and Imaginist dandyism appears as a catachrestic category in culture. The second chapter examines the Imaginist poetic theory. It is discussed in the context of the montage principle, defining the post-revolutionary culture in Soviet Russia. The Imaginist montage can be divided into three main theoretical paradigms: S. Yesenin’s “technical montage” (reminiscent of Dadaist collage), V. Shershenevich’s “nominative montage” (catalogues of images) and Anatolii Mariengof’s “catachrestic montage”. The final chapter deals with Mariengof’s first fictional novel, Cynics. The study begins with the complex history of publication of the novel, as well as its relation to the Imaginist poetic principles and to the history of the poetic movement. Cynics is, essentially, an Imaginist montage novel. The fragmentary play of the fictional and the documentary material follows the Imaginist montage principle. The chapter concludes in a thematic analysis of the novel, concentrating on the description of the October Revolution in Cynics.
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Literary tale of A.M. Remizov (1900’s – 1920’s) The thesis is devoted to a detailed historical-literary description of a tale as a genre tradition in the creative work of Alexei Mikhailovich Remizov (1877-1957), one of the major Russian prose writers of the 20’s century. This very approach allows to specify the place and functional meaning of this genre in literary practice of the writer and to appeal to one of the key problems of the 20-21 century literature history – a specific of modernistic literature composition principle and a role of montage techniques in its formation. Remizov was working on tales during his whole life, though the most productive years of folklore studies fell to 1900’s – 1910’s. During this period he intensively studied folklore materials, narrated several hundreds of folk tales and in 1900’s – 1920’s published eight tale collections which played a significant role in the formation of stylistic and compositional principles of his prose of the 1910’s – 1920’s, especially montage techniques, which in its turn influenced the development of the narrative forms in the Russian post-revolutionary literature. At the same time a tale has specified not only poetics but also problematics of Remizov’s creative work, as when choosing folklore sources the writer always alluded to modern themes and relevant intellectual trends. The current research work, based on various archive materials and a wide spectrum of modern historical-literary data, complies four chapters with a consistent description of creation history, publication and critics’ reviews of Remizov’s tale collections and single tales contributing to his creative evolution characteristic. Furthermore, the work refers to composition and subject of the particular collections. On the whole it enables to follow up genre dynamics. The first chapter of the work is devoted to Posolon’ (Sunwise), the earliest tale collection of Remizov. The main feature of the collection is that its composition is oriented on the agrarian calendar and the subject – on the system of mythological views reflected in the Russian folklore. This very collection to a large extent corresponds to the writer’s views on the myth represented in Pis’mo v redaktsiyu (Letter to the Editor). The history of this manifesto appearing is analyzed in the second chapter. The incident which caused its forthcoming contributed to ‘legitimization’ of Remizov’s narrations as a relevant genre of modern literature and to upgrading the writer in professional hierarchy. The third chapter analyzes Remizov’s collections of 1900’s – early 1920’s, a result of Remizov’s scrupulous work with a specific tale material. He is acting here as a tale repertory researcher and in some cases as a collector as well. The means of such collections’ topical organization is not the myth but the hero of the tale. According to this principle single pieces are grouped into cycles, which then form complicated montage constructs. Texts themselves can be viewed as a sort of hyper-quotations, as they in fact entirely coincide with their original sources. Besides, collections usually have their own ideal patterns. In the fourth chapter a connection of Remizov’s creative work with folk fun culture and a tradition of the folklore noel story is being demonstrated on Zavetnyie skazy (Secret Tales) material. A consistent collections’ history creation analysis convinces us that the tale was a sort of laboratory in which main writer’s prose methods were being worked out.