30 research outputs found
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Introduction, Copyright's Paradox
No full textThe United States Supreme Court famously labeled copyright “the engine of free expression” because it provides a vital economic incentive for much of the literature, commentary, music, art, and film that makes up our public discourse. Yet today’s greatly expanded copyright law often does the opposite—it can be used to quash news reporting, political commentary, church dissent, historical scholarship, cultural critique, and artistic expression.In Copyright’s Paradox, Neil Weinstock Netanel explores the tensions between copyright law and free speech concerns, revealing how copyright law can impose unacceptable burdens on speech. Netanel provides concrete illustrations of how copyright often prevents speakers from effectively conveying their message, tracing this conflict across both traditional and digital media and considering current controversies such as the YouTube and MySpace copyright infringement cases, Hip-hop music and digital sampling, and the Google Book Search litigation. The author juxtaposes the dramatic expansion of copyright holders’ proprietary control against the individual’s newly found ability to digitally cut, paste, edit, remix, and distribute sound recordings, movies, TV programs, graphics, and texts the world over. He tests whether, in light of these developments and others, copyright still serves as a vital engine of free expression and he assesses how copyright does--and does not--burden speech. Taking First Amendment values as his lodestar, Netanel argues that copyright should be limited to how it can best promote robust debate and expressive diversity, and he presents a blueprint for how that can be accomplished.Copyright and free speech will always stand in some tension. But, as Netanel demonstrates, there are ways in which copyright can continue to serve as an engine of free expression while leaving ample room for speakers to build on copyrighted works to convey their message, express their personal commitments, and fashion new art
Correlation functions in T T ¯ -deformed Conformal Field Theories
No full textAbstract We study the correlation functions of local operators in unitary T T ¯ -deformed field theories, using their formulation in terms of Jackiw-Teitelboim gravity. The position of the operators is defined using the dynamical coordinates of this formalism. We focus on the two-point correlation function in momentum space, when the undeformed theory is a conformal field theory. In particular, we compute the large momentum behavior of the correlation functions, which manifests the non-locality of the T T ¯ -deformed theory. The correlation function has UV-divergences, which are regulated by a point-splitting regulator. Renormalizing the operators requires multiplicative factors depending on the momentum, unlike the behavior in local QFTs. The large momentum limit of the correlator, which is the main result of this paper, is proportional to q − q 2 π Λ , where q is the momentum and 1/|Λ| is the deformation parameter. Interestingly, the exponent here has a different sign from earlier results obtained by resummation of small q computations. The decay at large momentum implies that the operators behave non-locally at the scale set by the deformation parameter
Neuronal morphology as an instrument for information coding: studying the influence of axonal radius and branching points
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Ultrastructural analysis of dendritic spine necks reveals a continuum of spine morphologies: Models
No full textDendritic spines are membranous protrusions, with a bulbous head connected to the dendrite by a thin neck, and receive essentially all excitatory inputs in most mammalian neurons. Spines have a wide variety of morphologies that likely have a significant effect on their biochemical and electrical properties. The question of whether spines belong to distinct morphological or functional subtypes or constitute a continuum is still open. To discern this, it is important to measure spine necks objectively. Recent advances in electron microscopy enable automatic reconstructions of 3D spines with nanometer precision. Analyzing ultrastructural reconstructions from mouse neocortical neurons with computer vision algorithms, we demonstrate that the vast majority of spines can be rigorously separated into head and neck components. Analysis of the head and neck morphologies reveals a continuous distribution of parameters. The spine neck diameter, but not the neck length, was correlated with the head volume. Spines with larger head volumes often had a spine apparatus and pairs of spines in a post-synaptic cell contacted by the same axon had similar head volumes. Our data are consistent with a lack of morphological categories of spines and indicate that the morphologies of the spine neck and head are independently regulated. These results have repercussions for our understanding of the function of dendritic spines in neuronal circuits
Branching morphology determines signal propagation dynamics in neurons
No full textAbstractComputational modeling of signal propagation in neurons is critical to our understanding of basic principles underlying brain organization and activity. Exploring these models is used to address basic neuroscience questions as well as to gain insights for clinical applications. The seminal Hodgkin Huxley model is a common theoretical framework to study brain activity. It was mainly used to investigate the electrochemical and physical properties of neurons. The influence of neuronal structure on activity patterns was explored, however, the rich dynamics observed in neurons with different morphologies is not yet fully understood. Here, we study signal propagation in fundamental building blocks of neuronal branching trees, unbranched and branched axons. We show how these simple axonal elements can code information on spike trains, and how asymmetric responses can emerge in axonal branching points. This asymmetric phenomenon has been observed experimentally but until now lacked theoretical characterization. Together, our results suggest that axonal morphological parameters are instrumental in activity modulation and information coding. The insights gained from this work lay the ground for better understanding the interplay between function and form in real-world complex systems. It may also supply theoretical basis for the development of novel therapeutic approaches to damaged nervous systems.</jats:p
Spike transmission failures in axons from cortical neurons in vivo
No full textThe propagation of action potentials along axons is traditionally considered reliable due to the high safety factor for axonal spike transmission. However, numerical simulations suggest that high-frequency spikes could fail to invade distal axonal branches. To explore this experimentally in vivo, we used an axonal-targeted calcium indicator to image action potentials at axonal terminal branches in the superficial layers of mouse somatosensory cortical neurons. We activated axons with an extracellular electrode, varying stimulation frequencies, and analyzed the images to computationally extract axonal morphologies and associated calcium responses. We found that axonal boutons have higher calcium accumulations than their axonal shafts, as was reported in vitro. However, contrary to previous in vitro results, our data reveal spike failures at high spike frequencies in a significant subset of branches as a function of branching geometry. These findings suggest that axonal morphologies could contribute to signal processing in the cortex
Expert Opinion and Reform in Anglo-American, Continental, and Israeli Adjudication
No full textThe factual framework of modem litigation has become increasingly technical and complex; this development poses new challenges for traditional fact-finders. More and more, expert witnesses are being used to assist judges and juries in the factfinding process. This Article examines the role of the expert witness in the common-law and civil-law judicial systems, emphasizing the manner in which the divergent systems have responded to the need for reform in this area. The author then examines the role of the expert in the hybrid Israeli judicial system, which is rooted in both the civil-law and common-law traditions. Finally, the author demonstrates the relationship between prevailing attitudes toward the nature of adjudication and the response to pressure for the reform of the adjudicative process
Expert Opinion and Reform in Anglo-American, Continental, and Israeli Adjudication
No full textThe factual framework of modem litigation has become increasingly technical and complex; this development poses new challenges for traditional fact-finders. More and more, expert witnesses are being used to assist judges and juries in the factfinding process. This Article examines the role of the expert witness in the common-law and civil-law judicial systems, emphasizing the manner in which the divergent systems have responded to the need for reform in this area. The author then examines the role of the expert in the hybrid Israeli judicial system, which is rooted in both the civil-law and common-law traditions. Finally, the author demonstrates the relationship between prevailing attitudes toward the nature of adjudication and the response to pressure for the reform of the adjudicative process
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Spike transmission failures in axons from mouse cortical pyramidal neurons in vivo - raw data
No full textThe propagation of action potentials along axons is traditionally considered to be reliable, as a consequence of the high safety factor of action potential propagation. However, numerical simulations have suggested that, at high frequencies, spikes could fail to invade distal axonal branches. Given the complex morphologies of axonal trees, with extensive branching and long-distance projections, spike propagation failures could be functionally important. To explore this experimentally in vivo, we used an axonal-targeted calcium indicator to image action potentials at axonal terminal branches in superficial layers from mouse somatosensory cortical pyramidal neurons. We activated axons with an extracellular electrode, varying stimulation frequencies, and computationally extracted axonal morphologies and associated calcium responses. We find that axonal boutons have higher calcium accumulations than their parent axons, as was reported in vitro. But, contrary to previous in vitro results, our data reveal spike failures in a significant subset of branches, as a function of branching geometry and spike frequency. The filtering is correlated with the geometric ratio of the branch diameters, as expected by cable theory. These findings suggest that axonal morphologies contribute to signal processing in the cortex
Structural Analysis of Human and Mouse Dendritic Spines Reveals a Morphological Continuum and Differences across Ages and Species
No full textDendritic spines have diverse morphologies, with a wide range of head and neck sizes, and these morphologic differences likely generate different functional properties. To explore how this morphologic diversity differs across species and ages we analyzed 3D confocal reconstructions of ∼8000 human spines and ∼1700 mouse spines, labeled by intracellular injections in fixed tissue. Using unsupervised algorithms, we computationally separated spine heads and necks and systematically measured morphologic features of spines in apical and basal dendrites from cortical pyramidal cells. Human spines had unimodal distributions of parameters, without any evidence of morphologic subtypes. Their spine necks were longer and thinner in apical than in basal spines, and spine head volumes of an 85-year-old individual were larger than those of a 40-year-old individual. Human spines had longer and thicker necks and larger head volumes than mouse spines. Our results indicate that human spines form part of a continuum, are larger and longer than those of mice, and become larger with increasing adult age. These morphologic differences in spines across species could generate functional differences in biochemical and electrical spine compartmentalization, or in synaptic properties, across species and ages
