1,278 research outputs found
Computational convergence of the path integral for real dendritic morphologies
No full textNeurons are characterised by a morphological structure unique amongst biological cells, the core of which is the dendritic tree. The vast number of dendritic geometries, combined with heterogeneous properties of the cell membrane, continue to challenge scientists in predicting neuronal input-output relationships, even in the case of sub-threshold dendritic currents. The Green’s function obtained for a given dendritic geometry provides this functional relationship for passive or quasi-active dendrites and can be constructed by a sum-over-trips approach based on a path integral formalism. In this paper, we introduce a number of efficient algorithms for realisation of the sum-over-trips framework and investigate the convergence of these algorithms on different dendritic geometries. We demonstrate that the convergence of the trip sampling methods strongly depends on dendritic morphology as well as the biophysical properties of the cell membrane. For real morphologies, the number of trips to guarantee a small convergence error might become very large and strongly affect computational efficiency. As an alternative, we introduce a highly-efficient matrix method which can be applied to arbitrary branching structures
Gap junctions, dendrites and resonances : a recipe for tuning network dynamics
No full textGap junctions, also referred to as electrical synapses, are expressed along the entire central nervous system and are important in mediating various brain rhythms in both normal and pathological states. These connections can form between the dendritic trees of individual cells. Many dendrites express membrane channels that confer on them a form of sub-threshold resonant dynamics. To obtain insight into the modulatory role of gap junctions in tuning networks of resonant dendritic trees, we generalise the “sum-over-trips” formalism for calculating the response function of a single branching dendrite to a gap junctionally coupled network. Each cell in the network is modelled by a soma connected to an arbitrary structure of dendrites with resonant membrane. The network is treated as a single extended tree structure with dendro-dendritic gap junction coupling. We present the generalised “sum-over-trips” rules for constructing the network response function in terms of a set of coefficients defined at special branching, somatic and gap-junctional nodes. Applying this framework to a two-cell network, we construct compact closed form solutions for the network response function in the Laplace (frequency) domain and study how a preferred frequency in each soma depends on the location and strength of the gap junction
Monocationic μ-diborolyl triple-decker complexes [CpCo(μ-1,3-C 3B2Me5)M(ring)]+: Synthesis, structures, and electrochemistry
No full textCationic triple-decker complexes with a bridging diborolyl ligand, [CpCo(μ-1,3-C3B2Me5)M(ring)]+ (M(ring) = CoCp (2a), CoCp* (2b), RhCp (3a), RhCp* (3b), IrCp (4a), IrCp* (4b), Ru(C6H6) (5a), Ru(p-MeC 6H4Pri) (5b), Ru(C6Me6) (5c), Ru(η6-cycloheptatriene) (6)), were synthesized by reaction of CpCo(μ-1,3-C3B2Me5)Tl with [M(ring)Hal2]2. The structures of 2aBPh4, 2bPF6, 4aPF6, 5aOTf, and 5cPF6 were determined by X-ray diffraction. The electron-transfer ability of the complexes has been ascertained by electrochemical and spectroelectrochemical techniques. In general, they are able to shuttle reversibly in the sequence 2+/+/0/-, plausibly affording completely delocalized mixed-valence derivatives. DFT calculations revealed structural changes accompanying redox processes and satisfactorily predicted the potentials for the first reduction and first oxidation. © 2013 American Chemical Society
Editorial for special issue on neurodynamics
No full text“Neurodynamics” is an interdisciplinary area of mathematics where dynamical systems theory (deterministic and stochastic) is the primary tool for elucidating the fundamental mechanisms responsible for the behaviour of neural systems (whether biological or synthetic). A meeting on this topic was held at the International Centre for Mathematical Sciences in Edinburgh from March 5–7 in 2012. In this special issue, we have invited seven of the main contributors to this event to expand on their presentations and highlight the use of mathematics in understanding the dynamics of neural systems
Fig. 1. Heterocotyle chinensis Timofeeva, 1983 in Heterocotyle chinensis (Monogenea: Monocotylidae) from the Whip Stingray Dasyatis akajei in the Seto Inland Sea, Japan
No full textFig. 1. Heterocotyle chinensis Timofeeva, 1983. NMST-Pl 6164. A, whole mount (ventral view); B, hamulus; C, hooklet; D, male copulatory organ. Scale bars: A, 200 µm; B–D, 10 µm. Abbreviations: alg, anterolateral gland; amg, anteromedian gland; d, duct; dh, dorsal haptoral accessory structure; ej, ejaculatory bulb; ey, eyespots; h, hamulus; ho, hooklet; in, intestine; m, mouth; mag, male accessory gland; mco, male copulatory organ; mg, Mehlis' gland; o, oötype; od, oviduct; ov, ovary; ph, pharynx; pg, posterior gland; phg, pharyngeal glands; r, sinuous ridge; sr, seminal receptacle; sv, seminal vesicle; t, testis; tv, transverse vitelline duct; u, uterus; vi, vitellaria; v, vagina; vp, vaginal pore; vd, vas deferens.Published as part of Nitta, Masato & Nagasawa, Kazuya, 2015, Heterocotyle chinensis (Monogenea: Monocotylidae) from the Whip Stingray Dasyatis akajei in the Seto Inland Sea, Japan, pp. 89-93 in Species Diversity 20 on page 90, DOI: 10.12782/sd.20.1.089, http://zenodo.org/record/573752
"You Tempt me Grievously to a Mythological Essay": J. R. R. Tolkien’s Correspondence with Arthur Ransome
No full textBranching dendrites with resonant membrane: a “sum-over-trips” approach
No full textDendrites form the major components of neurons. They are complex branching structures that receive and process thousands of synaptic inputs from other neurons. It is well known that dendritic morphology plays an important role in the function of dendrites. Another important contribution to the response characteristics of a single neuron comes from the intrinsic resonant properties of dendritic membrane. In this paper we combine the effects of dendritic branching and resonant membrane dynamics by generalising the “sum-over-trips” approach (Abbott et al. in Biol Cybernetics 66, 49–60 1991). To illustrate how this formalism can shed light on the role of architecture and resonances in determining neuronal output we consider dual recording and reconstruction data from a rat CA1 hippocampal pyramidal cell. Specifically we explore the way in which an Ih current contributes to a voltage overshoot at the soma
Lung Cancer Risk in Never-Smokers of European Descent is Associated With Genetic Variation in the 5p15.33 TERT-CLPTM1Ll Region
No full textInstituto de Salud Carlos III. PI15/01211 grant and Xunta de Galicia grant 10CSA208057PR.Hung, R.J., Spitz, M.R., Houlston, R.S., Schwartz, A.G., Field, J.K., Ying, J., Li, Y., Han, Y., Ji, X., Chen, W., Wu, X., Gorlov, I.P., Na, J., de Andrade, M., Liu, G., Brhane, Y., Diao, N., Wenzlaff, A., Davies, M.P.A., Liloglou, T., Timofeeva, M., Muley, T., Rennert, H., Saliba, W., Ryan, B.M., Bowman, E., Barros-Dios, J.-M., Pérez-Ríos, M., Morgenstern, H., Zienolddiny, S., Skaug, V., Ugolini, D., Bonassi, S., van der Heijden, E.H.F.M., Tardon, A., Bojesen, S.E., Landi, M.T., Johansson, M., Bickeböller, H., Arnold, S., Le Marchand, L., Melander, O., Andrew, A., Grankvist, K., Caporaso, N., Teare, M.D., Schabath, M.B., Aldrich, M.C., Kiemeney, L.A., Wichmann, H.-E., Lazarus, P., Mayordomo, J., Neri, M., Haugen, A., Zhang, Z.-F., Ruano-Raviña, A., Brenner, H., Harris, C.C., Orlow, I., Rennert, G., Risch, A., Brennan, P., Christiani, D.C., Amos, C.I., Yang, P., Gorlova, O.Y
Morphology of hybrid polystyrene-block-poly(ethylene oxide) micelles: Analytical ultracentrifugation and SANS studies
No full textMorphology and structure of aqueous block copolymer solutions based on polystyrene-block-poly(ethylene oxide) (PS-b-PEO) of two different compositions, a cationic surfactant, cetyl pyridinium chloride (CPC), and either platinic acid (H2PtCl6⋅6H2O) or Pt nanoparticles were studied using a combination of analytical ultracentrifugation (AUC), transmission electron microscopy (TEM), and small angle neutron scattering (SANS). These studies combining methods contributing supplemental and analogous structural information allowed us to comprehensively characterize the complex hybrid systems and to discover an isotope effect when H2O was replaced with D2O. In particular, TEM shows formation of both micelles and larger aggregates after incorporation of platinic acid, yet the amount of aggregates depends on the H2PtCl6⋅6H2O concentration. AUC reveals the presence of micelles and micellar clusters in the PS-b-PEO block copolymers solution and even larger (supermicellar) aggregates in hybrids (with CPC). Conversely, SANS applied to D2O solutions of the similar species indicates that micelles are spherical and no other micellar species are found in block copolymer solutions. To reconcile the SANS and AUC data, we carried out AUC examination of the corresponding D2O block copolymer solutions. These measurements demonstrate a pronounced isotope effect on micelle aggregation and micelle size, i.e., no micelle aggregation in D2O solutions, revealing good agreement of AUC and SANS dat
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