Attempts to understand the individual and collective properties of neurons are made from numerous scientific perspectives. We describe the results of traditional approaches that emphasize the importance of physical laws and the elucidation of mechanisms, and discuss recent developments regarding the properties of interacting neuronal systems. The present view of the structure of ion channels is summarized, followed by an explanation of their role in the generation and propagation of action potentials. Important dynamical processes that occur in systems of neurons are treated, including processes that occur in sensory systems, neural networks, and in the volume transmission of electrical and chemical systems in the central nervous system. Uses of nonlinear analysis to characterize brain electrical activity are delineated, and new experimental methods for studying memory and learning are outlined. Further insights into how the nervous system mediates behavior seems likely to emerge from an approach that integrates well-established reductionistic strategies with reliance on abstract concepts and the use of nonlinear methods.

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... [15] In an ionic crystal the point defects formed must maintain electroneutrality and therefore will occur in pairs or multiplets. [23,28,29] The basic point defects are either Schottky defects – cation vacancies and anion vacancies (e.g. MgO), or cation-Frenkel defects – cation vacancies and interstitial cations (e.g. ...

... [30] The diffusion of the ions in an ionic crystal is a classical jump process via the point defects. [23,28,29] Taking ZrO 2 as an example, the mobile species is the oxide ion which jumps via the oxygen ion vacancies. The tracer diffusion coefficient, D t , of the oxide ion can be written as ...

... H R is the Haven ratio, the ratio of the correlation factors for diffusion and conduction. [23,28] Usually only one of the defects in the pair is the more mobile species and this will dominate the ionic conductivity, e.g. the oxide ion vacancies in ZrO 2 . The diffusion coefficients or conductivity measurements are plotted in Arrhenius form, i.e. log D t or log s versus 1/T, ...

... The Green's functions [1] present a powerful tool to calculate the response of complex systems, as an evolution in time or the effect of a stimulus at any location in space. Electromagnetics methods mostly aim at solving boundary value problems [2], however, evaluations of field distributions and optical densities of states in open systems [3] dominated by multiple scattering rely on the same propagators. ...

... This approach also works with renormalized transfer functions, interactions or susceptibilities. However, the Dyson equation for these in the second 1 analogy to G 2 -call the transfer function taking account of both V 2 . Had the perturbations been put in at once together, we would have to work with the Dyson equations ...

... From the second to the third line on the left the conversion is G 2 (v 1 + v 2 ) = gV 2 according to at once full inclusion of all interactions in the Green's functions. On the right we needed G 1 v 1 = gV 1 and v 1 G 1 = V 1 g as well as again G 2 (v 1 + v 2 ) = gV 2 . A factor g on the left of all terms is skipped in the end. ...

  • Ursula Schröter
  • Elke Scheer

For systems governed by two kinds of interactions it is shown that these can be built successively into the Green's functions describing the system's response. Whereas for the ordinary Green's function the Dyson equation to solve has the same form in each step, we derive the non-trivial second-step equation for the transfer or coupling function, which on the one hand is closely related to the self-energy and on the other hand of practical relevance in transport calculations.

... LJ interactions were truncated at L = 10 Å, and standard long-range corrections were applied [245,246]. where B and A are constants, and β = 0.325 is the critical exponent for Ising-type fluids in three dimensions [249]. T c and ρ c are the critical temperature and density, respectively. ...

... This is a typical assumption made for small molecules, where the intramolecular degree of freedom represents a small contribution for the overall energy of the system [113,252]. The geometry of HFA134a was minimized using SPARTAN'02 [276], under the MMFF94 approximation and is shown in Previous works indicate that while polarizabilities might strongly affect dynamical interfacial properties and the overall dipole moment of the interfacial region [269], structural interfacial properties are not expected to be strongly influenced by polarization effects [249,277]. It is also interesting to note that, in two independent investigations, while the tension reported for the CCl 4 |Air and CCl 4 |W interfaces with polarizable potential models compares poorly with the experiments [269], excellent agreement was observed with nonpolarizable models [278]. ...

  • Robson Peguin Robson Peguin

Aerosol inhalation therapy is an alternative to oral and parenteral approaches for the systemic delivery of drugs to and through the lungs. Pressurized metered-dose inhalers (pMDIs) are the least expensive aerosol therapy devices available, and have been suggested as potential candidates for the delivery of therapeutic biomolecules. However, there have been several challenges in the design of pMDIs as CFCs are being replaced with more environmentally friendly alternatives, the hydrofluoroalkanes (HFAs). In spite of the fact that the operation of pMDIs with HFAs is similar to those with CFCs, previous formulations are not compatible due to the significantly different properties between these two classes of fluids. Lack of fundamental knowledge on the solvation forces in HFAs, and on the interfacial properties of volatile propellant mixtures is preventing us from extending the applicability of reliable and simple formulations for the delivery of polar drugs using pMDIs. A combination of computational and experimental approaches was used in this dissertation to develop novel HFA-philes that find applications in dispersion formulations, including reverse aqueous microemulsions in HFAs. Their design depends on our ability to relate the chemistry of candidate tail moieties to their HFA-philicity. Chemical force microscopy and ab initio calculations show that the ester-based fragment is highly HFA-philic. The results also indicate that all investigated fragments (including linear and branched ethers, fluorinated and methylated moieties) are better solvated in HFA227 than in HFA134a. Electrostatic forces are seen to greatly contribute to the stabilization of HFA-fragment complexes. Thermodynamic and microstructural properties of the neat and surfactant-modified HFA:Water interface were obtained using in situ high-pressure tensiometry and atomistic computer simulations. A new force field for HFA able to accurately predict the vapor-liquid equilibria and those interfacial properties is also proposed. These studies pave the road for the screening of interfacially active species for the HFA:Water interface using computer simulations. These studies are relevant not only for the development of reverse aqueous microemulsion-based pMDI formulations, but all HFA-related pMDIs where amphiphiles are generally required. ^

... Green's functions [1, 2, 3, 4] are encountered as response functions, time-ordered expectation values, certain solutions of boundary-value problems or resolvent kernels. This introduction to Green's functions is based on their role as kernels of differential equations. ...

  • Ursula Schröter

This introduction to Green's functions is based on their role as kernels of differential equations. The procedures to construct solutions to a differential equation with an external source or with an inhomogeneity term are put together to derive the Dyson equation for the Green's function of the inhomogeneous system. Very different areas of physics such as, for example, electrodynamics and quantum transport, can profit from this Green's function formalism. The fundamental homogeneous-medium Green's tensor of electrodynamics is deduced from the field of a dipole. Based upon that a numerical procedure is presented to solve the wave-equation for the near-field in a scattering setup for arbitrary material distributions. The full inhomogeneous system's Green's function is not explicitly needed to get the fields, although it can be obtained by a very similar calculation and in optics can be interpreted as a density of states. It is demonstrated how the transport problem for two open free-electron gas reservoirs with arbitrary coupling can be solved by finding the system's Green's function. In this sense the article is an introduction on Green's functions for treating interaction. A very detailed discussion of the current formula is given on an elementary basis.

  • Lonny Douglas Meinecke Lonny Douglas Meinecke

This paper posits the need for a fourth component in the tripartite model of attitude. Attributions by spiritual persons differ from those of individualists and collectivists in that attributions of blame are dismissed (using forgiveness), and attributions of self-credit are ignored (credited instead to God). Arguments include the need to consider transcendence, the evolution of attitudinal models, unique concepts, cultural impact, and nonsecular attribution. Spirituality's framework allows attributions to something other than people and situations, and attribution error avoidance using forgiveness and glory. Benefits include a fuller view of attitude, and applications to aid grief and family connectedness. Supported by previous developing research on attitude, the paper suggests adding a spiritual dimension to the existing affective, cognitive, and behavioral components.

Gap junctions (GJ), specialised membrane structures that mediate cell-to-cell communication in almost all animal tissues, are composed of intercellular channel-forming integral membrane proteins termed connexins (Cxs), innexins or pannexins. The activity of these channels is closely regulated, particularly by intramolecular modifications as phosphorylation of proteins, via the formation of multiprotein complexes where pore-forming subunits bind to auxiliary channel subunits and associate with scaffolding proteins that play essential roles in channel localization and activity. Scaffolding proteins link signalling enzymes, substrates, and potential effectors (such as channels) into multiprotein signalling complexes that may be anchored to the cytoskeleton. Protein-protein interactions play essential roles in channel localization and activity and, besides their cell-to-cell channel-forming functions, gap junctional proteins now appear involved in different cellular functions (e.g. transcriptional and cytoskeletal regulation). The present review summarizes the recent progress regarding the proteins capable of interacting with junctional proteins and their functional importance.

  • P. L. Nunez

This text is the second edition of this book. It expands the widely acclaimed 1981 book, filling more gaps between EEG and the physical sciences. EEG opens a "window on the mind" by finding new connections between psychology and physiology. Topics include synaptic sources, electrode placement, choice of reference, volume conduction, power and coherence, projection of scalp potentials to dura surface, dynamic signatures of conscious experience, and neural networks immersed in global fields of synaptic action.

  • Wilfrid Rall

This paper is concerned with the interpretation of passive membrane potential transients produced in a neuron when intracellular microelectrodes are used to apply current across the soma membrane. It is also concerned with the specific problem of estimating the nerve membrane time constant from experimental transients in neurons having extensive dendritic trees. When this theory is applied to the most recent results published for cat motoneurons, the resulting membrane time constant estimates are significantly larger than the values estimated by Eccles and collaborators. The time course of soma membrane potential is solved for a variety of applied currents: current step, brief pulse of current, sinusoidal current, voltage clamping current, and a current of arbitrary time course. The sinusoidal case provides a theoretical basis for a purely electrophysiological method of estimating the fundamental ratio between combined dendritic input conductance and soma membrane conductance. Also included is the time course of passive decay to be expected to follow various somadendritic distributions of membrane depolarization or hyperpolarization. The discussion includes an assessment of the observations, hypotheses, and interpretations that have recently complicated our understanding of synaptic potentials in cat motoneurons. It appears that electrotonic spread between the dendrites and soma can account for the observations which led Eccles and collaborators to postulate a prolonged residual phase of synaptic current in cat motoneurons.

  • Gordon M. Shepherd

Synapses are the contact sites that enable neurons to form connections between each other in order to transmit and process neural information. Synaptic organization is concerned with the principles by which neurons form circuits that mediate the specific functional operations of different brain regions. One of the aims of this book is to show that the study of synaptic organization-in its full multidisciplinary, multilevel, and theoretical dimension-is a powerful means of integrating brain information to give clear insights into the neural basis of behavior. This book, which has been revised in this the fifth edition, details local circuits in the different regions of the brain. The results of the mouse and human genome projects are incorporated. Also the book contains support from neuroscience databases. Among the new advances covered are 2-photon confocal laser microscopy of dendrites and dendritic spines, biochemical analyses, and dual patch and multielectrode recordings, applied together with an increasing range of behavioral and gene-targeting methods. © 974, 1979, 1990, 1998, 2004 by Oxford University Press, Inc. All rights reserved.