Andrew David Jackson

ON THE ACTION POTENTIAL AS A PROPAGATING DENSITY PULSE AND THE ROLE OF ANESTHETICS

The Hodgkin-Huxley model of nerve pulse propagation relies on ion currents through specific resistors called ion channels. We discuss a number of classical thermodynamic findings on nerves that are not contained in this classical theory. Particularly striking is the finding of reversible heat changes, thickness and phase changes of the membrane during the action potential. Data on various nerves rather suggest that a reversible density pulse accompanies the action potential of nerves. Here, we attempted to explain these phenomena by propagating solitons that depend on the presence of cooperative phase transitions in the nerve membrane. These transitions are, however, strongly influenced by the presence of anesthetics. Therefore, the thermodynamic theory of nerve pulses suggests a explanation for the famous Meyer-Overton rule that states that the critical anesthetic dose is linearly related to the solubility of the drug in the membranes.

Towards a thermodynamic theory of nerve pulse propagation.

Nerve membranes consist of an approximately equal mixture of lipids and proteins. The propagation of nerve pulses is usually described with the ionic hypothesis, also known as the Hodgkin-Huxley model. This model assumes that proteins alone enable nerves to conduct signals due to the ability of various ion channel proteins to transport selectively sodium and potassium ions. While the ionic hypothesis describes electrical aspects of the action potential, it does not provide a theoretical framework for understanding other experimentally observed phenomena associated with nerve pulse propagation. This fact has led to a revised view of the action potential based on the laws of thermodynamics and the assumption that membrane lipids play a fundamental role in the propagation of nerve pulses. In general terms, we describe how pulses propagating in nerve membranes resemble propagating sound waves. We explain how the language of thermodynamics enables us to account for a number of phenomena not addressed by the ionic hypothesis. These include a thermodynamic explanation of the effect of anesthetics, the induction of action potentials by local nerve cooling, the physical expansion of nerves during pulse propagation, reversible heat production and the absence of net heat release during the action potential. We describe how these measurable features of a propagating nerve pulse, as well as the observed voltage change that accompanies an action potential, represent different aspects of a single phenomenon that can be predicted and explained by thermodynamics. We suggest that the proteins and lipids of the nerve membrane naturally constitute a single ensemble with thermodynamic properties appropriate for the description of a broad range of phenomena associated with a propagating nerve pulse.

Brownian Warps for Non-Rigid Registration

A Brownian motion model in the group of diffeomorphisms has been introduced as inducing a least committed prior on warps. This prior is source-destination symmetric, fulfills a natural semi-group property for warps, and with probability 1 creates invertible warps. Using this as a least committed prior, we formulate a Partial Differential Equation for obtaining the maximally likely warp given matching constraints derived from the images. We solve for the free boundary conditions, and the bias toward smaller areas in the finite domain setting. Furthermore, we demonstrate the technique on 2D images, and show that the obtained warps are also in practice source-destination symmetric and in an example on X-ray spine registration provides extrapolations from landmark point superior to those of spline solutions.

Fluctuations of systems in finite heat reservoirs with applications to phase transitions in lipid membranes

In an adiabatically shielded system, the total enthalpy is conserved. Enthalpy fluctuations of an arbitrarily chosen subsystem must be buffered by the remainder of the total system which serves as a heat reservoir. The magnitude of these fluctuations depends on the size of the reservoir. This leads to various interesting consequences for the physical behavior of the subsystem. As an example, we treat a lipid membrane with a phase transition that is embedded in an aqueous reservoir. We find that large fluctuations are attenuated when the reservoir has finite size. This has consequences for the compressibility of the membrane since volume and area fluctuations are also attenuated. We compare the equilibrium fluctuations of subsystems in finite reservoirs with those in periodically driven systems. In such systems, the subsystem has only finite time available to exchange heat with the surrounding medium. A larger frequency therefore reduces the volume of the accessible heat reservoir. Consequently, the fluctuations of the subsystem display a frequency dependence. While this work is of particular interest for a subsystem displaying a transition such as a lipid membrane, some of the results are of a generic nature and may contribute to a better understanding of relaxation processes in general.

The free energy of biomembrane and nerve excitation and the role of anesthetics

In the electromechanical theory of nerve stimulation, the nerve impulse consists of a traveling region of solid membrane in a liquid environment. Therefore, the free energy necessary to stimulate a pulse is directly related to the free energy difference necessary to induce a phase transition in the nerve membrane. It is a function of temperature and pressure, and it is sensitively dependent on the presence of anesthetics which lower melting transitions. We investigate the free energy difference of solid and liquid membrane phases under the influence of anesthetics. We calculate stimulus-response curves of electromechanical pulses and compare them to measured stimulus-response profiles in lobster and earthworm axons. We also compare them to stimulus-response experiments on human median nerve and frog sciatic nerve published in the literature.

Key Papers on Korea: Essays Celebrating 25 Years of the Centre of Korean Studies, SOAS, University of London

Key Papers on Korea is a commemorative collection of papers celebrating 25 years of the Centre of Korean Studies (CKS), SOAS, University of London that have been written by senior academics and emerging scholars. The subjects covered in this collection reflect the different research interests and different strengths of the CKS and include historical perceptions of ancient kingdoms in Manchuria, North Korean propaganda literature, the problematic history of Sino-North Korean borderlands, the millenarian aspects of Won Buddhism, and the importance of the years 1910-11 in the development of Korean music. The collection is framed by two pieces on SOAS, which have been commissioned exclusively for this publication: an introduction that examines the 60-year history of Korean studies at SOAS, and a closing paper that sheds light on the rare collections of Korean art held at SOAS.

Sound Propagation in Lipid Membranes

It has recently been shown that in-plane sound waves can propagate over long distances in lipid monolayers [1]. Earlier it has been proposed that the propagation of nerve signals can be described by sound phenomena called solitons [2]. The implications of sound propagation in lipid membranes for signaling in biology are far reaching and insight into this is essential for further investigation. Particularly interesting are propagation properties in the vicinity of the biologically relevant lipid melting transition, where mechanical and thermodynamical properties of the system change drastically. We have theoretically addressed the properties of sound propagation in lipid membranes throughout the lipid melting transition. We explored dispersion and attenuation for low frequency sound propagation, a regime previously unexplored. We find that dispersion and attenuation is closely related to the relaxation and the state of lipid membranes [3]. Interestingly, the vast significant changes of dispersion and attenuation occur on timescales similar to ion channel open times and the temporal length of the nerve pulse.[1] Griesbauer et al., PRL, 108, 198103 (2012).[2] Heimburg & Jackson, PNAS, 102, 9790 (2005).[3] Mosgaard et al., Adv. Planar Lipid Bilayers Liposomes, 16 (2012).

Korean Screen Cultures

The «Korean Wave», or Hallyu phenomenon, has brought South Korean popular culture to the global population. Studies on Korean visual culture have therefore often focused on this aspect, leaving North Korea sidelined and often considered in a negative light because of its political regime. Korean Screen Cultures sets out to redress this imbalance with a broad selection of essays spanning both North and South as well as different methodological approaches, from ethnographic and audience studies to cultural materialist readings. The first section of the book, «The South», highlights popular media – including online gaming and television drama – and concentrates on the margins, in which the very nature of «The South» is contested. «The South and the North» examines North Korea as an ideological other in South Korean popular culture as well as discussing North Korean cinema itself. «The Global» offers new approaches to Korean popular culture beyond national borders and includes work on K-pop and Korean television drama. This book is a vital addition to existing scholarship on Korean popular culture, offering a unique view by providing an imaginary unification of the two Koreas negotiated through local and transnational popular culture flows.E J-Yongs films are diverse, ranging from melodrama (An Affair, 1998) to musical comedy (Dasepo Naughty Girls, 2006); from historical drama (Untold Scandal, 2003) to mocumentary-style drama (Actresses, 2009), as well as a Korean-Japanese co-produced art-house film (Asako in Ruby Shoes, 2001), but what they share in common are cosmopolitanism and criticism of parochial nationalism. This paper explores palimpsestic characteristics that inscribe cosmopolitanism in Es films, addressing the intertextual dynamics with the source material, narrative structures, and the characters who travel abroad or aspire to go abroad.

Korean screen cultures: interrogating cinema, TV, music and online games

The «Korean Wave», or Hallyu phenomenon, has brought South Korean popular culture to the global population. Studies on Korean visual culture have therefore often focused on this aspect, leaving North Korea sidelined and often considered in a negative light because of its political regime. Korean Screen Cultures sets out to redress this imbalance with a broad selection of essays spanning both North and South as well as different methodological approaches, from ethnographic and audience studies to cultural materialist readings. The first section of the book, «The South», highlights popular media – including online gaming and television drama – and concentrates on the margins, in which the very nature of «The South» is contested. «The South and the North» examines North Korea as an ideological other in South Korean popular culture as well as discussing North Korean cinema itself. «The Global» offers new approaches to Korean popular culture beyond national borders and includes work on K-pop and Korean television drama. This book is a vital addition to existing scholarship on Korean popular culture, offering a unique view by providing an imaginary unification of the two Koreas negotiated through local and transnational popular culture flows.E J-Yongs films are diverse, ranging from melodrama (An Affair, 1998) to musical comedy (Dasepo Naughty Girls, 2006); from historical drama (Untold Scandal, 2003) to mocumentary-style drama (Actresses, 2009), as well as a Korean-Japanese co-produced art-house film (Asako in Ruby Shoes, 2001), but what they share in common are cosmopolitanism and criticism of parochial nationalism. This paper explores palimpsestic characteristics that inscribe cosmopolitanism in Es films, addressing the intertextual dynamics with the source material, narrative structures, and the characters who travel abroad or aspire to go abroad.

From ‘Years of Radical Change’ to ‘Korean Screen Culture’: the story of a conference name

In June 2016, King’s College London will host the fifth Korean Screen Culture Conference. To my knowledge, this is the longest running – perhaps the only – annual international conference devoted to the critical examination of Korean film, K-drama, K-pop videos and online gaming. Since 2012, speakers representing academic institutions in the UK, the USA, South Korea, New Zealand, Germany, Romania, France, Israel and many other countries have presented over 70 papers at four different venues. This special edition of the Journal of Japanese and Korean Cinema includes papers from the fourth Korean Screen Culture Conference held at the University of Copenhagen, Denmark, on 29–30 May 2015. This introduction provides a brief history of this event by exploring some of the difficulties that arose over the naming of the conference – a process that raised fundamental questions about how to locate and conceptualize Korean screen culture (Figure 1). My intention in 2012 was to bring together eminent scholars of Korean film based at UK universities for a one-day workshop. The original title ‘Korean Film: Years of Radical Change’ was supposed to reflect the dramatic shifts that had occurred in South Korean cinema between the 1980s and the 2000s. The period had seen the relaxation of censorship, the lifting of restrictions on production and the opening of the South Korean film market. The term ‘radical’ also referred to a post-dictatorship generation of politically engaged directors like Jang Sun-woo, Park Kwang-su and Chung Ji-young, who produced films that challenged previous representations of the Korean War, as well as addressing urbanization and working practices in South Korea (Paquet 2009, 21–28). These directors’ work had attracted academic analysis, but questions remained – such as why the momentum of this socially conscious period of filmmaking did not continue on the same level into the early part of the new millennium. The first conference was held at the School of Oriental and African Studies in London (SOAS) in May 2012, and invited speakers considered different aspects of South Korean film (Figure 2). Colette Balmain discussed female voices in recent South Korean horror cinema, while Jinhee Choi investigated 1960s actor Kim Seung-ho’s home dramas. Chiyun Shin presented a paper on director E-J Yong, whose films include Dasepo Naughty Girls (Dasepo Sonyo, 2006), Julian Stringer examined sound in contemporary South Korean cinema and Mark Morris presented a paper on the representation of Joseonjok (ethnic Koreans in northeastern China) in the cinema of filmmaker Jang Ryul/Zhang lu. Subjects at the conference ranged from the Golden Age of South Korean cinema to gender in genre film, auteur directors, sound and diasporic film. While the diverse