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81.
A coupled map lattice (CML) provides a mathematical model for both spatially extended physical and biological systems, and for a new type of parallel computing system. We analyse a general process to realize a multilayer structured CML by coupling m CMLs together with arbitrary coupling structure. As an application we use this coupling process in the study of a CML with multilayer planar architecture and non-symmetric hierarchical coupling between the layers. These CMLs model neural architectures and use chaotic maps as the basic elements in the lattice. We measure the complexity of the state of each layer and an increase in spatio-temporal coherence as one ascends a hierarchical feedforward layered network. 相似文献
82.
The near field technologies, negative index materials (NIM), photonic crystals and plasmonics combined with innovation in high dielectric antennas, wireless systems, and photonic circuits open the prospect of novel antennas, integrated circuits, sensors (chemical, biological and individual molecule), medical scanners, displays and imagers, which have the potential to outperform conventional technology and create many commercial opportunities [A.J. Holden, Inside the Wavelength, Electromagnetics in the Near Field, State of the Science Review for DTI Foresight, UK, February 2004, available at: http://www.foresight.gov.uk/]. A selection of these applications is reviewed and the challenges for the technologies set in context. 相似文献
83.
Raymond J. Abraham Collette M. Holden Philip Loftus David Whittaker 《Magnetic resonance in chemistry : MRC》1974,6(3):184-189
The 13C spectra of α-thujene ( 1 ), isothujone ( 2 ), (?)isothujol ( 3 ), (+)neoisothujol ( 4 ), sabinol ( 5 ), dihydroumbellulone ( 6 ) and umbellulone ( 7 ) and the alcohol acetates are recorded and assigned. The C-6 chemical shift may be used in conjunction with the steric shift mechanism as a conformational probe in these molecules. The results obtained indicate that isothujol, neoisothujol, isothujone and dihydroumbellulone adopt boat-like conformations whilst sabinol has a much flatter conformation. Conjugation of the isolated double bond of α-thujene and the carbonyl group of dihydroumbellulone with the cyclopropane ring has virtually no effect on the 13C shifts, but those of umbellulone itself are anomalous, indicating conjugation of the α,β unsaturated ketone system with the cyclopropyl ring. 相似文献
84.
85.
86.
R Nirmala V Sankaranarayanan K Sethupathi AV Morozkin T Geethakumary Y Hariharan 《Pramana》2002,58(5-6):1101-1104
New R
2Ti3Ge4 (R=Dy, Ho and Er) intermetallic compounds have been synthesized and characterized by X-ray diffraction and low temperature ac
magnetic susceptibility, electrical resistivity and thermoelectric power measurements were carried out. The compounds crystallize
in the parent, Sm5Ge4-type orthorhombic structure (space group Pnma) and lanthanide contraction is observed as one moves along the rare-earth series.
The changeover from paramagnetic to antiferromagnetic phase happens at low temperatures and the ordering temperature scales
with the de Gennes factor. The electrical resistivity is metallic with a negative curvature above 100 K. Thermopower displays
a weak maximum at temperatures less than 50 K signifying the possible phonon and magnon drag effects. 相似文献
87.
Douglas R Keene Sara F Tufa Gregory P Lunstrum Paul Holden William A Horton 《Microscopy and microanalysis》2008,14(4):342-348
Genetic manipulation allows simultaneous expression of green fluorescent protein (GFP) and its derivatives with a wide variety of cellular proteins in a variety of living systems. Epifluorescent and confocal laser scanning microscopy (confocal) localization of GFP constructs within living tissue and cell cultures has become routine, but correlation of light microscopy and high resolution transmission electron microscopy (TEM) on components within identical cells has been problematic. In this study, we describe an approach that specifically localizes the position of GFP/yellow fluorescent protein (YFP) constructs within the same cultured cell imaged in the confocal and transmission electron microscopes. We present a simplified method for delivering cell cultures expressing fluorescent fusion proteins into LR White embedding media, which allows excellent GFP/YFP detection and also high-resolution imaging in the TEM. Confocal images from 0.5-microm-thick sections are overlaid atop TEM images of the same cells collected from the next serial ultrathin section. The overlay is achieved in Adobe Photoshop by making the confocal image somewhat transparent, then carefully aligning features within the confocal image over the same features visible in the TEM image. The method requires no specialized specimen preparation equipment; specimens are taken from live cultures to embedding within 8 h, and confocal transmission overlay microscopy can be completed within a few hours. 相似文献
88.
Hwang WL Holden MA White S Bayley H 《Journal of the American Chemical Society》2007,129(38):11854-11864
Aqueous droplets submerged in an oil-lipid mixture become enclosed by a lipid monolayer. The droplets can be connected to form robust networks of droplet interface bilayers (DIBs) with functions such as a biobattery and a light sensor. Such DIB networks might be used as model systems for the study of membrane-based biological phenomena. In this study, we develop and experimentally validate an electrical modeling approach for DIB networks by applying it to describe the current flow through a simple network containing protein pores and blocking molecules. We demonstrate the use of SPICE (Simulation Program with Integrated Circuit Emphasis) for simulating the electrical behavior of DIB networks. The modular and scalable nature of DIB networks should enable a straightforward extension of the analysis presented in this paper to large, complex networks. 相似文献
89.
Cardiac ventricular cells and tissues are normally excitable, and are activated by propagating waves of excitation that are initiated in the specialized pacemaking region of the heart. However, isolated or repetitive activity can be initiated at abnormal (ectopic) sites in the ventricles. To trigger an endogenous ectopic beat, there must be a compact focus of cells with changed membrane excitation parameters and kinetics, which initiate activity by after-depolarizations triggered by propagating activity, or that have bifurcated into autorhythmicity. This ectopic focus needs to be large enough, and adequately coupled, to drive the surrounding tissue. We investigate the initiation of ectopic excitation in computational models of human ventricular cells triggered by after-depolarizations and by up/down regulation of specific membrane conductance systems, and the propagation and evolution of ectopic activity in homogeneous or heterogeneous and isotropic, anisotropic, or orthotropic tissues. 相似文献
90.
We prove the existence of a global semigroup for conservative solutions of the nonlinear variational wave equation u
tt
− c(u)(c(u)u
x
)
x
= 0. We allow for initial data u|
t = 0 and u
t
|
t=0 that contain measures. We assume that
0 < k-1 \leqq c(u) \leqq k{0 < \kappa^{-1} \leqq c(u) \leqq \kappa}. Solutions of this equation may experience concentration of the energy density (ut2+c(u)2ux2)dx{(u_t^2+c(u)^2u_x^2){\rm d}x} into sets of measure zero. The solution is constructed by introducing new variables related to the characteristics, whereby
singularities in the energy density become manageable. Furthermore, we prove that the energy may focus only on a set of times
of zero measure or at points where c′(u) vanishes. A new numerical method for constructing conservative solutions is provided and illustrated with examples. 相似文献