4,367 research outputs found
Diffusion approximation and first–passage–time problem for a model neuron. III. A birth–and–death process approach
No full textA stochastic model for single neuron's activity is constructed as the continuous limit of a birth-and-death process in the presence of a reversal hyperpolarization potential. The resulting process is a one dimensional diffusion with linear drift and infinitesimal variance, somewhat different from that proposed by Lansky and Lanska in a previous paper. A detailed study is performed for both the discrete process and its continuous approximation. In particular, the neuronal firing time problem is discussed and the moments of the firing time are explicitly obtained. Use of a new computation method is then made to obtain the firing p.d.f.. The behaviour of mean, variance and coefficient of variation of the firing time and of its p.d.f. is analysed to pinpoint the role played by the parameters of the model. A mathematical description of the return process for this neuronal diffusion model is finally provided to obtain closed form expressions for the asymptotic moments and steady state p.d.f. of the neuron's membrane potential
Petr Simon (1944-2018)
No full textThis article is a reflection on the mathematical legacy of Professor Petr Simon.Green Open Access added to TU Delft Institutional Repository ‘You share, we take care!’ – Taverne project https://www.openaccess.nl/en/you-share-we-take-care Otherwise as indicated in the copyright section: the publisher is the copyright holder of this work and the author uses the Dutch legislation to make this work public.Analysi
On two diffusion neuronal models with multiplicative noise: The mean first-passage time properties
No full textTwo diffusion processes with multiplicative noise, able to model the changes in the neuronal membrane depolarization between two consecutive spikes of a single neuron, are considered and compared. The processes have the same deterministic part but different stochastic components. The differences in the state-dependent variabilities, their asymptotic distributions, and the properties of the first-passage time across a constant threshold are investigated. Closed form expressions for the mean of the first-passage time of both processes are derived and applied to determine the role played by the parameters involved in the model. It is shown that for some values of the input parameters, the higher variability, given by the second moment, does not imply shorter mean first-passage time. The reason for that can be found in the complete shape of the stationary distribution of the two processes. Applications outside neuroscience are also mentioned
A Gauss-Markov based approach to model the neuronal firing activity in the presence of a time-varying threshold
No full textCentralization of treasury management 2010
No full textThe book consists of five parts: 1. Treasury management and its responsibilities (Chapter 1‐4); 2. Decentralized treasury (Chapter 5); 3. Different phases of the centralization (Chapter 6‐9); 4. Outsourcing (Chapter 10) 5. Regional treasury centres (Chapter 11); 6. Best practices in a bank (Chapter 12); In the first part, the author describes the treasury management focusing on its three core responsibilities, such as assets and liabilities management, cash management, and financial risk management. The second part zooms in on decentralized treasury and decisions about the appropriate degree of centralization/decentralization of the treasury activities. Then we focus on the different phases of the process of centralization, from central interest rate and foreign exchange management through centralization of cash and liquidity management, then transaction processing up to fully centralized treasury. In part four we continue by discussing outsourcing as the next stage following centralization to achieve additional economic benefits. The fifth part contains especially a number of the location criteria, both tax and non‐tax, that must be evaluated during consideration where to establish the regional treasury centre. The last part deals with banking best practices in cash pooling from the point of view of the author that works in one of the top banks in Central and Eastern Europe region
Cyclometalation of phenylpyridines with a ferrocenyl group
No full textNázev práce: Cyklometalace fenylpyridinů s ferrocenylovým substituentem Autor: Bc. Petr Harmach Katedra: Katedra anorganické chemie Vedoucí diplomové práce: prof. RNDr. Petr Štěpnička, Ph.D., DSc. Abstrakt: Cílem této práce byla příprava cyklometalovaných komplexů fenylpyridinů s ferrocenylovým substituentem. Cyklometalované komplexy mají široké spektrum využití, kdy jedním z nejvýznamnějších je použití v katalýze. Připraveny byly iridité a rhodité cyklometalované komplexy s elektrondonorními nebo elektronakceptorními skupinami na pyridinovém kruhu. Všechny tyto látky byly charakterizovány 1 H a 13 C{1 H} NMR spektroskopií, hmotnostní spektrometrií, elementární analýzou a cyklickou voltametrií. U dvou připravených látek byly jejich struktury potvrzeny pomocí metody difrakce rentgenového záření na monokrystalech. Klíčová slova: cyklometalace, pyridin, C-H aktivace, ferrocenTitle: Cyclometalation of phenylpyridines with a ferrocenyl group Author: Bc. Petr Harmach Department: Katedra anorganické chemie Supervisor: prof. RNDr. Petr Štěpnička, Ph.D., DSc. Abstract: The objective of this thesis was the synthesis of cyclometalated complexes of phenylpyridine with a ferrocenyl group. Cyclometalated complexes have a wide range of application, where one of the most important is the use in catalysis. Iridium(III) and rhodium(III) cyclometalated complexes were prepared containing electron-donating or electron-accepting groups on the pyridine ring. All newly prepared complexes were characterized by 1 H a 13 C{1 H} NMR spectroscopy, mass spectrometry, elemetal analysis and cyclic voltammetry. The structures of two complexes were determined by single-crystal X-ray diffraction analysis. Key words: cyclometalation, pyridine, C-H activation, ferroceneDepartment of Inorganic ChemistryKatedra anorganické chemiePřírodovědecká fakultaFaculty of Scienc
Adaptivní volba parametrů stabilizačních metod pro rovnice konvekce-difúze
No full textTitle: Adaptive choice of parameters in stabilization methods for convection- diffusion equations Author: Bc. Petr Lukáš (e-mail: [email protected]) Department: Department of Numerical Mathematics Supervisor: Doc. Mgr. Petr Knobloch, Dr. (e-mail: [email protected]) Abstract: The aim of the work is to propose suitable approaches for adap- tive choice of parameters in stabilization methods for convection-difusion equations discretized by the finite element method. We introduce the L-SR1 method, compare it with other nonlinear methods of minimizing functions with large number of variables, and introduce and compare the adaptive methods based on minimizing of the error indicator. Keywords: Adaptive choice of parameters, finite element method, stabiliza- tion methods, convection-diffusion equation, L-SR1 method, error indicato
Cyclometalation of phenylpyridines with a ferrocenyl group
No full textTitle: Cyclometalation of phenylpyridines with a ferrocenyl group Author: Bc. Petr Harmach Department: Katedra anorganické chemie Supervisor: prof. RNDr. Petr Štěpnička, Ph.D., DSc. Abstract: The objective of this thesis was the synthesis of cyclometalated complexes of phenylpyridine with a ferrocenyl group. Cyclometalated complexes have a wide range of application, where one of the most important is the use in catalysis. Iridium(III) and rhodium(III) cyclometalated complexes were prepared containing electron-donating or electron-accepting groups on the pyridine ring. All newly prepared complexes were characterized by 1 H a 13 C{1 H} NMR spectroscopy, mass spectrometry, elemetal analysis and cyclic voltammetry. The structures of two complexes were determined by single-crystal X-ray diffraction analysis. Key words: cyclometalation, pyridine, C-H activation, ferrocen
Synthesis of gold(I) carbene complexes from isocyanoferrocene
No full textTitle: Synthesis of gold(I) carbene complexes from isocyanoferrocene Author: Petr Harmach Department: Katedra anorganické chemie Supervisor: prof. RNDr. Petr Štěpnička, Ph.D., DSc. Abstract: The objective of this bachelor thesis was the synthesis of gold(I) carbene complexes. These complexes were synthetised from a newly prepared gold(I)-isocyanoferrocene complex and also directly from isocyanoferrocene. Carbene complexes were obtained from primary and secondary amines, and therefore complexes contain disubstituted or trisubstituted diaminocarbene moieties. All newly prepared complexes were characterized by NMR spectroscopy, mass spectrometry, elemental analysis and infrared spectroscopy. The structures of the majority of the prepared complexes were confirmed by single-crystal X-ray diffraction analysis. Key words: isocyanides, ferrocene, carbenes, gold(I) complexe
Homologous ferrocene phosphines
No full textTitle: Homologous ferrocene phosphines Author: Bc. Petr Vosáhlo Department: Department of Inorganic Chemistry Supervisor: prof. RNDr. Petr Štěpnička, Ph.D., DSc. Abstract: This thesis describes the synthesis and coordination behaviour of ferrocene diphosphines derived from 1,1'-bis(diphenylphosphino)ferrocene (dppf). Dppf is one of the most succesful ferrocene ligands, which can be used in various metal-catalyzed reactions. This study aimed to prepare analogous ligands with one dialkylphosphino substituent and one (diphenylphosphino)methyl group. These ligands were oxidized by KSeCN to afford the corresponding phosphinoselenides. The phosphinoselenides were used to assess sigma-donor abilities by measuring the coupling constant 1 JSeP via 31 P NMR spectroscopy. Lastly, the coordination behaviour of these ligands in palladium complexes was studied. The homologous ligands usually formed a mixtures containing a chelate complex and dimeric species with trans- coordinated ligands. Key words: ferrocene, phosphines, homologous ligands, palladium(II) complexes, structure elucidation
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