Bibliografie tematiche / Intrinsic excitation

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Letteratura scientifica selezionata sul tema "Intrinsic excitation"

Autore: Grafiati

Pubblicato: 2 novembre 2024

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Articoli di riviste sul tema "Intrinsic excitation"

Trukhin, A. N. "Energy Transport in SiO₂ Crystals: Luminescence Excitation Spectra of Stishovite and α-Quartz". Latvian Journal of Physics and Technical Sciences 59, n. 4 (1 agosto 2022): 19–24. http://dx.doi.org/10.2478/lpts-2022-0030.

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Abstract The migration of elementary electronic excitations was studied in a single crystal of stishovite and compared with migration in a crystal of α-quartz and polycrystalline stishovite powder. The research method is based on comparing the transfer of absorbed energy to luminescence centers, used as detectors of quasiparticles, and the near-surface nonradiative annihilation of electronic excitations. A sign of migration is the appearance of some minima in the photoluminescence (PLE) excitation spectrum in the region of maxima in the intrinsic absorption spectrum. The PLE spectrum of stishovite contains the first minimum at 9.8 eV, indicating the migration of electronic excitations and the existence of an intrinsic absorption band in stishovite at 9.8 eV. In α-quartz, the first minimum in the PLE spectrum is located at 10.5 eV and corresponds well to the intrinsic absorption band of the exciton.

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Belsky, A. N., R. Cortes, A. V. Gektin, P. Martin, V. V. Mikhailin e C. Pédrini. "Excitation mechanisms of CsI fast intrinsic luminescence". Journal of Luminescence 72-74 (giugno 1997): 93–95. http://dx.doi.org/10.1016/s0022-2313(97)00028-8.

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Sorbello, C., e R. Etchenique. "Intrinsic optical sectioning with upconverting nanoparticles". Chemical Communications 54, n. 15 (2018): 1861–64. http://dx.doi.org/10.1039/c7cc08443a.

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Hizhnyi, Yuriy, S. G. Nedilko, V. Chornii, T. Nikolaenko, I. V. Zatovsky, K. V. Terebilenko e R. Boiko. "Electronic Structure and Luminescence Spectroscopy of M'Bi(MoO₄)₂ (M' = Li, Na, K), LiY(MoO₄)₂ and NaFe(MoO₄)₂ Molybdates". Solid State Phenomena 200 (aprile 2013): 114–22. http://dx.doi.org/10.4028/www.scientific.net/ssp.200.114.

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The mechanisms of intrinsic luminescence in the set of molybdate crystals of MIMIII(MoO4)2 (MI = Li, Na, K; MIII =Bi, Y, Fe) type are revealed in complex experimental and theoretical studies. The luminescence spectroscopy under vacuum ultraviolet (VUV) synchrotron excitations is applied together with the electronic structure calculations carried out by the FLAPW method. The energy gaps (Eg) values of the crystals are determined in simultaneous analysis of diffuse reflectance and luminescence excitation spectra. It is found that the molybdate groups MoO42- play a dominant role in the processes of intrinsic luminescence in studied molybdate compounds

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Omagari, Shun, e Martin Vacha. "Toward accurate measurement of the intrinsic quantum yield of lanthanide complexes with back energy transfer". Physical Chemistry Chemical Physics 22, n. 6 (2020): 3683–90. http://dx.doi.org/10.1039/c9cp06294g.

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Wu, Ting, Yiting Tao, Panting Wang, Mingjun Zhao e Danping Chen. "ZnCl2-Enhanced Intrinsic Luminescence of Tin Chlorophosphate Glasses". Photonics 9, n. 12 (12 dicembre 2022): 973. http://dx.doi.org/10.3390/photonics9120973.

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This communication reports the intrinsic luminescence of tin chlorophosphate glasses. The glass maintains the low melting point characteristics of tin fluorophosphate glasses, and exhibits a red-shifted and broadened excitation wavelength peak. Tin chlorophosphate glasses can exhibit a broadband luminescence of 400–700 nm under an excitation of 380–430 nm. Furthermore, the introduction of ZnCl2 into tin chlorophosphate glasses can considerably enhance the luminescence without affecting their low-melting characteristics. The luminescence intensity can be increased fourfold, with the enhancement attributed to the reduced visible absorption, improved dispersion of Sn2+ ions, and the energy exchange between Sn2+ and Zn2+ in the glasses owing to the addition of ZnCl2.

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Steiner, T., e M. L. W. Thewalt. "Subnanosecond transient studies of intrinsic and extrinsic luminescence in CdSe". Canadian Journal of Physics 63, n. 9 (1 settembre 1985): 1205–11. http://dx.doi.org/10.1139/p85-197.

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The photoluminescence spectrum and transient behaviour of free and bound excitons in CdSe have been studied with both resonant and above band-gap excitation. The free- and bound-exciton lifetimes were found to be excitation-intensity dependent even at very low levels. In all cases, the free-exciton luminescence decayed more rapidly than that of the bound excitons. A comparison of the no-phonon and longitudinal-optic-phonon replicas of the free-exciton luminescence indicates that the observed doublet structure of the no-phonon spectrum arises from the two polariton branches. Resonant excitation of the donor and acceptor bound excitons revealed two-electron and two-hole replicas, respectively. We believe these to be the first reported two-hole transitions in CdSe. The initial rapid cooling of the free-exciton gas could be observed in a series of time-resolved spectra.

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Zhyshkovych, A. V. "Intrinsic and impurity luminescence of CaF2, CaF2:Eu2+ and CaF2:Eu3+ nanoparticles at high energy excitation". Functional materials 21, n. 1 (30 marzo 2014): 10–14. http://dx.doi.org/10.15407/fm21.01.010.

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Wang, Yangbo, Yingdong Han, Runfa Liu, Cunping Duan e Huaiyong Li. "Excitation-Controlled Host–Guest Multicolor Luminescence in Lanthanide-Doped Calcium Zirconate for Information Encryption". Molecules 28, n. 22 (16 novembre 2023): 7623. http://dx.doi.org/10.3390/molecules28227623.

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Efficient control over lanthanide luminescence by regulating excitations offers a real-time and reversible luminescence-managing strategy, which is of great importance and highly desirable for various applications, including multicolor display and information encryption. Herein, we studied the crystal structure, luminescence properties, and mechanisms of undoped and Tb3+/Eu3+-doped CaZrO3 in detail. The intrinsic purple-blue luminescence from host CaZrO3 and the introduced green/red luminescence from guest dopants Tb3+/Eu3+ were found to have different excitation mechanisms and, therefore, different excitation wavelength ranges. This enables the regulation of luminescent color through controlling the excitation wavelengths of Tb3+/Eu3+-doped CaZrO3. Furthermore, preliminary applications for information encryption with these materials were demonstrated using portable UV lamps of 254 and 302 nm. This study not only promotes the development of multicolor luminescence regulation in fixed-composition materials, but also advances the practical applications of lanthanide luminescent materials in visually readable, high-level anti-counterfeiting and information encryption.

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Yamayose, Y., Y. Kinoshita, Y. Doi, A. Nakatani e T. Kitamura. "Excitation of intrinsic localized modes in a graphene sheet". Europhysics Letters (EPL) 80, n. 4 (24 ottobre 2007): 40008. http://dx.doi.org/10.1209/0295-5075/80/40008.

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Più fonti

Tesi sul tema "Intrinsic excitation"

Carpentier, Paul. "Microscopic and dynamical description of the fission process including intrinsic excitations". Electronic Thesis or Diss., université Paris-Saclay, 2024. http://www.theses.fr/2024UPASP093.

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Parmi les différentes réactions nucléaires, la fission est sans aucun doute l'une des plus difficiles à décrire, reflétant la diversité des aspects dynamiques du problème à N corps. Lors de ce processus, le noyau se retrouve dans des états de déformations extrêmes aboutissant à la formation de deux fragments. Les études réalisées au CEA se concentrent jusqu'ici sur la fission d'actinides à l'hypothèse adiabatique : à chaque étape du mouvement collectif le noyau est considéré dans son état de minimum d'énergie. Seuls les degrés de libertés collectifs, telle que la déformation, sont pris en compte. Néanmoins les mécanismes de brisure de paires de nucléons ont été expérimentalement observés ; l'énergie dissipée dans les excitations individuelles de ces nucléons est estimée de l'ordre de 15-20 MeV au moment de la scission. Ce sujet de thèse s'intéresse à la prise en compte des états excités de basse énergie du noyau pour décrire la fission de basse énergie, jusqu'à quelques MeV au-dessus de la barrière de fission, dans un cadre théorique permettant d'unifier la prise en compte des degrés de liberté collectifs et individuels du noyau. L'estimation de l'énergie dissipée dans les excitations intrinsèques permet une bien meilleure estimation de la répartition de l'énergie disponible à la scission, à savoir dans l'énergie cinétique total de fission, l'émission de neutrons prompts ou de photons. Les résultats obtenus sont directement comparés aux données expérimentales disponibles
Among the various nuclear reactions, fission is undoubtedly one of the most difficult to describe, reflecting the diversity of dynamic aspects of the N-body problem. During this process, the nucleus is found in states of extreme deformations resulting in the formation of two fragments. The studies carried out at CEA are concentrated so far on the fission of actinides in the adiabatic hypothesis: at each stage of collective motion, the nucleus is considered in its minimum state energy. Only collective degrees of freedom, such as deformation, are then used. Nevertheless, the mechanisms of nucleon pair breaking have been experimentally observed; the energy dissipated in the individual (or intrinsic) excitations of these nucleons is estimated to be in the range of 15-20 MeV at scission. This PhD thesis is concerned with taking account of the excited low energy states of the nucleus to describe low energy fission, up to a few MeV above the fission barrier, in a theoretical framework allowing to unify the collective and individual degrees of freedom of the nucleus. The calculation of the energy dissipated in the intrinsic excitations allows a better estimation of the distribution of the energy available at scission, namely in the total kinetic energy of fission, the emission of prompt neutrons or photons. The results obtained are directly comparable to the available experimental data

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Boucetta, Soufiane, e Soufiane Boucetta. "Modulation of intrinsic and synaptic excitability during sleep oscillations and electrographic seizures". Master's thesis, Université Laval, 2005. http://hdl.handle.net/20.500.11794/18026.

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Le présente mémoire fournit des nouvelles évidences montrant la modulation de l’excitabilité neuronale intrinsèque et synaptique, et la conséquence de cette modulation sur l’activité neuronale durant à la fois, les oscillations lentes du sommeil, et les crises électrographiques in vivo chez des animaux anesthésiés. Nous effectuons des enregistrements intracellulaires simultanés de neurones corticaux et des potentiels de champs locaux au niveau du gyrus suprasylvien à l’intérieur du cortex associatif pariétal (aires : 5, 7 et 21). Nous suggérons que la fluctuation de la concentration extracellulaire du calcium durant les oscillations lentes du sommeil module à la fois, l’excitabilité intrinsèque et synaptique des neurones corticaux, ainsi par conséquent, elle module affecte la relation d’input-output de ces neurones. L’apparition durant les oscillations lentes du sommeil, des crises de type Lennex-Gastaut qui sont générées corticalement, nous a permet d’étudier les propriétés spatio-temporelles des ondes paroxysmiques rapides associées avec ce type de crises. Nous suggérons que les ondes paroxysmiques rapides apparaissent comme des oscillations quasi-indépendantes même dans les localisations corticales voisines, suggérant leur origine focal.
Le présente mémoire fournit des nouvelles évidences montrant la modulation de l’excitabilité neuronale intrinsèque et synaptique, et la conséquence de cette modulation sur l’activité neuronale durant à la fois, les oscillations lentes du sommeil, et les crises électrographiques in vivo chez des animaux anesthésiés. Nous effectuons des enregistrements intracellulaires simultanés de neurones corticaux et des potentiels de champs locaux au niveau du gyrus suprasylvien à l’intérieur du cortex associatif pariétal (aires : 5, 7 et 21). Nous suggérons que la fluctuation de la concentration extracellulaire du calcium durant les oscillations lentes du sommeil module à la fois, l’excitabilité intrinsèque et synaptique des neurones corticaux, ainsi par conséquent, elle module affecte la relation d’input-output de ces neurones. L’apparition durant les oscillations lentes du sommeil, des crises de type Lennex-Gastaut qui sont générées corticalement, nous a permet d’étudier les propriétés spatio-temporelles des ondes paroxysmiques rapides associées avec ce type de crises. Nous suggérons que les ondes paroxysmiques rapides apparaissent comme des oscillations quasi-indépendantes même dans les localisations corticales voisines, suggérant leur origine focal.
The present memoir provides new evidences showing the modulation of intrinsic and synaptic excitability of cortical neurons, and the consequence of this modulation on neuronal activity during both slow sleep oscillations and electrographic seizures in vivo in anaesthetized animals. We performed simultaneous recordings of cortical neurons with local field potentials in suprasylvian gyrus within parietal associative cortex (area 5, 7 and 21). We suggest that the fluctuation of extacellular calcium concentration during slow sleep oscillations, modulates both intrinsic and synaptic excitability cortical neurons, thus by consequence modulates the input-output relationship of these neurons. The occurrence during slow-wave sleep of cortically generated Lennox-Gastaut type of seizures admits us to study the spatio-temporal properties of paroxysmal fast runs associated with this type of seizures. We suggest that fast runs appeared as quasi-independent oscillations even in neighbouring cortical locations suggesting their focal origin.
The present memoir provides new evidences showing the modulation of intrinsic and synaptic excitability of cortical neurons, and the consequence of this modulation on neuronal activity during both slow sleep oscillations and electrographic seizures in vivo in anaesthetized animals. We performed simultaneous recordings of cortical neurons with local field potentials in suprasylvian gyrus within parietal associative cortex (area 5, 7 and 21). We suggest that the fluctuation of extacellular calcium concentration during slow sleep oscillations, modulates both intrinsic and synaptic excitability cortical neurons, thus by consequence modulates the input-output relationship of these neurons. The occurrence during slow-wave sleep of cortically generated Lennox-Gastaut type of seizures admits us to study the spatio-temporal properties of paroxysmal fast runs associated with this type of seizures. We suggest that fast runs appeared as quasi-independent oscillations even in neighbouring cortical locations suggesting their focal origin.

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Paul, Uchenna Prince. "Fluorescence Detectors for Proteins and Toxic Heavy Metals". Diss., CLICK HERE for online access, 2004. http://contentdm.lib.byu.edu/ETD/image/etd416.pdf.

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Chang, Chi-Ying, e 張琦英. "Intrinsic fluorescence feature extraction of excitation-emission matrix by using multi-dimensional ensemble empirical mode decomposition". Thesis, 2013. http://ndltd.ncl.edu.tw/handle/r72caw.

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碩士
國立交通大學
生醫工程研究所
102
Excitation-emission matrix (EEM) fluorescence spectroscopy is a noninvasive method for tissue diagnosis and has become important in clinical use. However, the intrinsic characterization of EEM fluorescence remains unclear. Photobleaching and the complexity of the chemical compounds make it difficult to distinguish individual compounds due to overlapping features. Conventional studies use principal component analysis (PCA) for EEM fluorescence analysis, and the relationship between the EEM features extracted by PCA and diseases has been examined. The spectral features of different tissue constituents are not fully separable or clearly defined. Recently, a method called multi-dimensional ensemble empirical mode decomposition (MEEMD) was introduced; this method decomposes data by subtracting local means iteratively and can extract the intrinsic oscillations on multiple spatial scales without loss of information. The aim of this study was to extract the intrinsic characteristics of EEM by using MEEMD. We use simulated signal to examine the decomposition ability of MEEMD on decomposing signal which was similar to EEM but simpler than EEM, and then MEEMD was applied to decompose EEM. PCA was used to compare with MEEMD in this study. The results indicate that although PCA provides the main spectral features associated with chemical compounds, which mainly contributed by collagen, MEEMD can provide additional intrinsic features with more reliable mapping of individual chemical compounds, e.g. collagen and vitamin D. Overall, MEEMD provide a new point of view on EEM analysis and has the potential to extract intrinsic fluorescence features and improve the detection of biological fluorophores.of individual chemical compounds, e.g. collagen and vitamin D. Overall, MEEMD provide a new point of view on EEM analysis and has the potential to extract intrinsic fluorescence features and improve the detection of biological fluorophores.

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Libri sul tema "Intrinsic excitation"

Solymar, L., D. Walsh e R. R. A. Syms. Semiconductors. Oxford University Press, 2018. http://dx.doi.org/10.1093/oso/9780198829942.003.0008.

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Both intrinsic and extrinsic semiconductors are discussed in terms of their band structure. The acceptor and donor energy levels are introduced. Scattering is discussed, from which the conductivity of semiconductors is derived. Some mathematical relations between electron and hole densities are derived. The mobilities of III–V and II–VI compounds and their dependence on impurity concentrations are discussed. Band structures of real and idealized semiconductors are contrasted. Measurements of semiconductor properties are reviewed. Various possibilities for optical excitation of electrons are discussed. The technology of crystal growth and purification are reviewed, in particular, molecular beam epitaxy and metal-organic chemical vapour deposition.

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Asai, H. Theoretical Study of THz Emission from HTS Cuprate. A cura di A. V. Narlikar. Oxford University Press, 2017. http://dx.doi.org/10.1093/oxfordhb/9780198738169.013.9.

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This article examines the THz emission from high-temperature superconducting (HTS) cuprates in the mesoscopic state using the intrinsic Josephson junction model. Cuprate superconductors are high-temperature superconductors that exhibit exotic electromagnetic properties. One of the remarkable features of HTS cuprates is high anisotropy due to their layered structures. Almost all HTS cuprates are composed of stacks of CuO2 layers and blocking layers which supply charge carriers to the CuO2 layers. The crystal structures of the HTS cuprates naturally form Josephson junctions known as intrinsic Josephson junctions (IJJs). This article first describes the basic theory of IJJ and the mechanism of THz emission before discussing the effect of temperature inhomogeneity on the emission properties. It then introduces a novel IJJ-based THz emitter that utilizes laser heating. Theoretical results show that the THz emission is caused by the strong excitation of transverse Josephson plasma waves in IJJs under a direct current bias.

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Capitoli di libri sul tema "Intrinsic excitation"

Ramakrishnan, Subramanian, e Balakumar Balachandran. "Intrinsic Localized Modes in Micro-scale Oscillator Arrays Subjected to Deterministic Excitation and White Noise". In IUTAM Symposium on Multi-Functional Material Structures and Systems, 325–34. Dordrecht: Springer Netherlands, 2009. http://dx.doi.org/10.1007/978-90-481-3771-8_33.

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Bickham, S. R., S. A. Kiselev e A. J. Sievers. "Intrinsic Localized Modes in Anharmonic Lattices". In Spectroscopy and Dynamics of Collective Excitations in Solids, 247–74. Boston, MA: Springer US, 1997. http://dx.doi.org/10.1007/978-1-4615-5835-4_9.

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Adams, David j., e Javier Cuevas. "Electrophysiological Properties of Intrinsic Cardiac Neurons". In Basic and Clinical Neurocardiology, 1–60. Oxford University PressNew York, NY, 2004. http://dx.doi.org/10.1093/oso/9780195141290.003.0001.

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Abstract Cardiac performance is determined by the rate and strength of contraction of the heart. There is increasing evidence indicating that intrinsic cardiac neurons interact with extracardiac intrathoracic ganglia and the central nervous system to control the heart and are capable of independently monitoring and influencing cardiac function. Aspects of cardiac function that are subject to control by intracardiac neurons include chronotropic actions (changes in heart rate), dromotropic actions (changes in conduction of excitation) mediated by pacemaker and conducting cells, and inotropic actions (changes in contractile force) mediated by atrial and ventricular myocytes. In addition, the coronary circulation and aspects of cardiac valve function are likely to be influenced. Evidence obtained from histochemical, electrophysiological, and pharmacological studies both in vivo and in vitro strongly suggest that neurons form functional afferent, efferent, and local circuits within the cardiac nerve plexus. This plexus acts as a complex site for the integration and modification of sensory in put and cardiac output. Indeed, rather than being a simple relay station, the cardiac nerve plexus seems to share many similarities with the complex neural network of the enteric nervous system.

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Lőrincz, Magor L., Vincenzo Crunelli e Francois David. "Excitation-Inhibition Balance in Absence Seizure Ictogenesis". In Jasper's Basic Mechanisms of the Epilepsies, a cura di Massimo Avoli, Marco de Curtis, Christophe Bernard e Ivan Soltesz, 389–400. 5^a ed. Oxford University PressNew York, 2024. http://dx.doi.org/10.1093/med/9780197549469.003.0020.

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Abstract Thirty percent of children with absence seizures are pharmaco-resistant, and 60% suffer from neuropsychiatric comorbidities that often persist even after full pharmacological control of the seizures. This highlights the need for a detailed comprehension of the cellular and network mechanisms of these nonconvulsive seizures. Generally, network hyperexcitability and hypersynchrony underlying seizure ictogenesis are thought to originate from impaired inhibition or enhanced excitation. In absence seizures, there is a markedly enhanced synchrony in cortico-thalamic and cortico-basal ganglia-thalamic networks, but solid evidence from genetic animal models indicates that at the single-cell and neuronal population levels GABAergic inhibition is generally increased while excitation is mostly either unchanged or decreased. Here, recent results on intrinsic conductances and network mechanisms within cortico-thalamic and cortico-basal ganglia-thalamic circuits are highlighted that support this view.

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Shapiro, Howard M. "Fluorescent Probes". In Flow Cytometry for Biotechnology. Oxford University Press, 2005. http://dx.doi.org/10.1093/oso/9780195183146.003.0006.

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In the jargon of cytometry, cellular characteristics, such as size, nucleic acid content, and membrane potential, are usually referred to as parameters, a term that is also used for the physical characteristics, such as absorption, light scattering, and fluorescence intensity, that are measured by cytometric instrumentation. Fluorescence, as a physical parameter, plays a key role in the detection of probes on beads for multiplexed analysis. Cellular parameters can be classed as intrinsic or extrinsic. Intrinsic cellular parameters are those that can be measured without the use of a reagent; measurement of extrinsic parameters requires the use of reagents, which are almost always referred to as probes, thereby occasioning confusion among molecular biologists new to cytometry. Cellular parameters are also characterized as structural or functional; DNA and RNA content and the presence and copy number of an antigen or nucleic acid sequence are structural parameters, whereas internal pH, membrane potential, and enzyme activity are functional parameters. The distinction between structural and functional parameters blurs at the edge, but the concept has been generally useful. Fluorescent probes allow measurement of the widest variety of extrinsic cellular parameters. For an atom or molecule to fluoresce, it must first absorb a photon, raising an electron to a higher energy level that is known as an excited state. Excitation by absorption requires only about a femtosecond. Fluorescence occurs when the electron loses all or some of the absorbed energy by emission of a photon. The fluorescence lifetime, that is, the period between excitation and emission, is typically on the order of a few nanoseconds for fluorescent organic materials but is notably longer (hundreds of microseconds) for some materials (e.g., lanthanide chelates). In almost all cases, some of the excitation energy is lost nonradiatively by transitions between different vibrational energy levels of the electronic excited state; this loss requires that the emitted energy be less than the energy absorbed, meaning that the fluorescence emission will be at a longer wavelength than the excitation. The difference between the principal excitation and emission maxima in the fluorescence spectrum is known as the Stokes shift, honoring George Stokes, who first described fluorescence in the mid-1800s. Typical Stokes shifts are no more than a few tens of nanometers.

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Dunn, Philip M., Paul R. Coote e John N. Wood. "Correlative electrophysiological and biochemical studies in neuronal cell lines". In Neuronal Cell Lines, 105–32. Oxford University PressOxford, 1992. http://dx.doi.org/10.1093/oso/9780199633463.003.0005.

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Abstract Neuronal excitation is usually evoked by a chemical interaction with a specific membrane-associated receptor that results in an alteration in ion fluxes, a change in the transmembrane potential and a self-propagating wave of depolarization mediated by the activation of voltage-gated ion channels (1). The initial depolarizing event may occur through the direct action of a ligand on a receptor that has intrinsic channel activity, or indirectly through the medium of intracellular second messengers.

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Bradrick, Thomas D., e Jorge E. Churchich. "Time-resolved fluorescence and phosphorescence spectroscopy". In Spectrophotometry and Spectrofluorimetry. Oxford University Press, 2000. http://dx.doi.org/10.1093/oso/9780199638130.003.0007.

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In this chapter, we outline the basic theory and methodology for making time resolved fluorescence and phosphorescence measurements. We begin with a brief discussion of the intrinsic time dependence of fluorescence and phosphorescence decays, and also introduce several important photophysical concepts. Energy transfer measurements, which are important for determining molecular distances, are then addressed, followed by the convolution integral (which describes the luminescence decay that is actually observed in pulsed excitation experiments) and the relationships that are used to determine fluorescence lifetimes from phase/modulation data. Polarized fluorescence measurements, which are an important tool for following molecular motions, are then discussed, and the fluorescence portion of the chapter concludes with an overview of data analysis and brief descriptions of the instrumentation that is used in making time-resolved fluorescence measurements. The remainder of the chapter is then devoted to a discussion of phosphorescence spectroscopy. The intrinsic time dependence of fluorescence decays is derived in Section 3.3 of Chapter 2. There it is shown that if a population of excited singlet-state molecules is generated instantaneously, its size decreases exponentially with time, as does the intensity of the emitted photons. The fluorescence lifetime τS is typically used to describe the rate of decay, where τs-1 = kR + kNR + kISC + kPR and kR, kNR, kISC and kpR are the rate constants for the various parallel unimolecular de-excitation processes. If there are several non-interacting fluorophore species in solution, their excited states will decay independently and a sum of exponentials will be needed to describe how the sample’s fluorescence intensity decreases with time.

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Zaza, Antonio. "Anatomy and physiology of the sinus node". In ESC CardioMed, a cura di Giuseppe Boriani, 1940–43. Oxford University Press, 2018. http://dx.doi.org/10.1093/med/9780198784906.003.0446.

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The sinoatrial node (SAN) is the dominant pacemaker structure in the mammalian heart. It is endowed with robust intrinsic automaticity, providing periodic electrical excitation with a cycle widely modulated by autonomic influences. A number of membrane channels and transporters contribute to the net membrane current supporting SAN electrical activity, whose periodicity is determined by the interplay of two oscillators termed ‘membrane’ and ‘calcium’ clock respectively. This chapter describes the structure of the SAN, the peculiarities of its electrical cycle, the nature and modulation of the underlying clocks, and SAN interaction with atrial muscle. Moreover, the features and determinants of the temporal variability of the pacemaker cycle, clinically used to assess autonomic balance, are briefly discussed.

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Samiksha, Ms, Manjeet Singh Gautam, Anand Kumar e Vijay Ghanghas. "FUSION DYNAMICS OF 48TI + 60NI REACTION". In Futuristic Trends in Physical Sciences Volume 3 Book 2, 173–77. Iterative International Publishers, Selfypage Developers Pvt Ltd, 2024. http://dx.doi.org/10.58532/v3bkps2p2ch4.

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The fusion dynamics of 48Ti + 60Ni reaction is studied through simple Wong formula and Symmetric Asymmetric Gaussian Barrier Distribution (SAGBD) model. Fusion excitation function estimated by using Wong formula is significantly deviated from experiment data at sub-barrier energies, which demonstrates significance of intrinsic channels associated with participants in fusion process. Simple Wong formula falls short of explaining data particularly at energies below the barrier but the SAGBD model explained data qualitatively as well as quantitatively for above reaction. The impacts of dominant channels on fusion process for their action 48Ti + 60Ni is examined in terms of channel coupling parameter and .The percentage reduction in height of effective barrier() relative to Coulomb barrier is due to involvement of nuclear structure effect. The non-vanishing values of these parameters indicates significant impacts of nuclear structural properties of fusing pair on the fusion process.

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Atti di convegni sul tema "Intrinsic excitation"

Ikeda, Takashi, Yuji Harata e Keisuke Nishimura. "Intrinsic Localized Modes of Harmonic Oscillations in Pendulum-Arrays Subjected to Horizontal Excitation". In ASME 2013 International Design Engineering Technical Conferences and Computers and Information in Engineering Conference. American Society of Mechanical Engineers, 2013. http://dx.doi.org/10.1115/detc2013-12771.

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Abstract (sommario):

The behavior of intrinsic localized modes (ILMs) is investigated for an array with N pendula which are connected with each other by weak, linear springs when the array is subjected to horizontal, sinusoidal excitation. In the theoretical analysis, van der Pol’s method is employed to determine the expressions for the frequency response curves for fundamental harmonic oscillations. In the numerical calculations, the frequency response curves are presented for N = 2 and 3 and compared with the results of the numerical simulations. Patterns of oscillations are classified according to the stable steady-state solutions of the response curves, and the patterns in which ILMs appear are discussed in detail. The influence of the connecting springs of the pendula on the appearance of ILMs is examined. Increasing the values of the connecting spring constants may affect the excitation frequency range of ILMs and cause Hopf bifurcation to occur, followed by amplitude modulated motions (AMMs) including chaotic vibrations. The influence of the imperfections of the pendula on the system response is also investigated. Bifurcation sets are calculated to examine the influence of the system parameters on the excitation frequency range of ILMs and determine the threshold value for the connecting spring constant after which ILMs do not appear. Experiments were conducted for N = 2, and the data were compared with the theoretical results in order to confirm the validity of the theoretical analysis.

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Ghiner, A. V., e G. I. Surdutovich. "New Mechanism of Intrinsic Bistability of the Optical Media under Repetitive Pulse Excitation". In Nonlinear Dynamics in Optical Systems. Washington, D.C.: Optica Publishing Group, 1990. http://dx.doi.org/10.1364/nldos.1990.ob228.

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A new type of intrinsic bistability is proposed when usually "non-bistable" nonlinear medium shows bistability under action of a time-dependent input signal. A strict criterion for observation of such a bistability is deduced. It depends on the shape of the temporal response of the nonlinear medium under action of a separate rectangular input pulse.

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Haug, H., S. W. Koch, H. E. Schmidt e M. Lindberg. "Soliton Structures in the Excitation due to Induced Absorption". In Instabilities and Dynamics of Lasers and Nonlinear Optical Systems. Washington, D.C.: Optica Publishing Group, 1985. http://dx.doi.org/10.1364/idlnos.1985.fc6.

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It will be shown that in a nonlinear optical medium whoes absorption coefficient increases with the excitation density (e.g., free-carrier concentration in a semiconductor or temperature) , a soliton structure in the excitation density can occur, which in the stationary case is approximately the solution of a Sine-Gordon equation. For changing light intensity the soliton wall between the highly excited front part of the crystal and the weakly excited end part can move only in discrete jumps due to the intrinsic bistability. Experimental observations of these predictions have been obtained recently by Gibbs et al..

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Webb, Watt W., e Chris Xu. "Multi-photon Molecular Excitation to Illuminate Non-linear Laser Microscopy". In International Conference on Ultrafast Phenomena. Washington, D.C.: Optica Publishing Group, 1996. http://dx.doi.org/10.1364/up.1996.wb.1.

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Molecular excitation by two or more infra red photons simultaneously absorbed from strongly focused 100 femtosecond mode locked laser pulses provides intrinsic 3-d resolution for fluorescence microscopy and photochemical micro pharmacology in living biological cells. Confinement of non-linear excitation to the focal volume illuminated by ~1016 photons/nm2s eliminates out of focus photobleaching and photodamage and provides intrinsic 3-d resolution. To facilitate this technology new methods have developed for accurate measurements of multi-photon excitation cross sections and spectra in the absence of adequate data to guide non-linear laser microscopy applications. Absolute cross section measurements have been facilitated by development of a method that takes advantage of the interference of excitation pulse trains that are time shifted by a conventional Michaelson interferometer to allow variable relative delay of two spatially superimposed beams. Two photon excitation with single mode CW lasers provides an independent absolute calibration of cross sections. Measurements of more than twenty useful two-photon excitation spectra (690-1050nm) have revealed some with large blue shifts of the excitation peak. Two photon excitation spectra of some asymmetric molecules superimpose on the one photon absorption spectra (with wavelength doubled) presumably due to relaxation of parity selection rules in these cases. Most of the tested fluorescent molecules show blue shifted excitation peaks with strongly enhanced cross sections exceeding those observed at twice the one photon absorption. No red shifts of the excitation spectra have been detected. Three photon excitation spectra tend to mimic the one photon absorption spectra. Multi- photon excited emission spectra appear to duplicate the one photon fluorescence emission spectra.

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Rand, S. C., e P. Xie. "Intrinsic instabilities of cooperative upconversion dynamics in lasers". In OSA Annual Meeting. Washington, D.C.: Optica Publishing Group, 1993. http://dx.doi.org/10.1364/oam.1993.wss.5.

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When the 2.8 µm erbium laser is pumped well above threshold an instability is observed at a unique pumping wavelength which causes the laser inversion to be produced by interactions among neighboring impurity ions. We show experimentally that this instability does not occur at equivalent levels over threshold when excitation is provided at wavelengths other than 1.5 µm. This behavior is compared with the results of two theoretical approaches to a description of the nonlinear dynamics, namely a rate equation and a density matrix solution. It is shown theoretically that instabilities may originate from two different physical mechanisms in pair-pumped laser systems, both of which are related to the nonlinear upconversion terms. Oscillatory solutions for the laser output may arise either from interplay of the nonlinear upconversion response with cavity photon density or from delocalization of the pair interaction. Details of these predictions are compared with time series of the laser output to shed light on the true origin of the observed instabilities. A possible explanation of excess amplitude noise in conventional infrared Erbium lasers is offered.

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Ikeda, Takashi, Yuji Harata, Chongyue Shi e Keisuke Nishimura. "Localization Phenomena in Pendulum Arrays Subjected to Vertical Excitation". In ASME 2014 International Design Engineering Technical Conferences and Computers and Information in Engineering Conference. American Society of Mechanical Engineers, 2014. http://dx.doi.org/10.1115/detc2014-34461.

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Localization phenomena, also referred to as intrinsic localized modes (ILMs), are investigated in an N-pendulum array subjected to vertical harmonic excitation. The pendula behave nonlinearly and are connected with each other by weak linear springs. In the theoretical analysis, van der Pol’s method is employed to determine the expressions for frequency response curves for the principal parametric resonances, considering the nonlinear restoring moment of the pendula. In the numerical results, frequency response curves for N=2 and 3 are shown to examine the patterns of ILMs, and the influences of the connecting spring constants and the imperfections of the pendula. Bifurcation sets are also calculated to show the excitation frequency range and the conditions for the occurrence of ILMs. Increasing the connecting spring constant results in the appearance of Hopf bifurcation. The numerical simulations reveal the occurrence of ILMs with amplitude modulated motions (AMMs) including chaotic motions. ILMs were observed in experiments, and the experimental data were compared with the theoretical results. The validity of the theoretical analysis was confirmed by the experimental data.

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Wu, Li-Hua, e Yu Huang. "Analysis of intrinsic optical bistability in Tm: YSGG laser crystal pumped under avalanche excitation at around 1um". In Third International Conference on Photonics and Image in Agriculture Engineering (PIAGENG 2013), a cura di Honghua Tan. SPIE, 2013. http://dx.doi.org/10.1117/12.2019449.

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Jarašiūnas, K., M. Sūdžius, J. Storasta, V. Gudelis, L. Bastienė e R. Vasiliauskas. "Optical nonlinearities based on quenching and recovery of metastable EL2 defect in GaAs". In The European Conference on Lasers and Electro-Optics. Washington, D.C.: Optica Publishing Group, 1994. http://dx.doi.org/10.1364/cleo_europe.1994.cthl5.

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Abstract (sommario):

Semi-insulating GaAs with its native mid-gap defect EL2 reveals optical optical nonlinearities of different kinds at short pulse excitation: (i) intrinsic ones based on nonequilibrium free carriers, and (ii) photorefractive ones due to space-charge redistribution. The metastable properties of EL2 open novel possibilities for direct optical modulation of quasi-Fermi level by resonant excitation and quenching of EL2 defect at low temperatures.1 This novel object—a light induced periodic structure of alternating areas with n- and p-type conductivity—needs deeper studies.

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Torkamani, Shahab, Eric A. Butcher, Michael D. Todd e Gyuhae Park. "Damage Assessment Using Hyperchaotic Excitation and State-Space Geometry Changes". In ASME 2010 Conference on Smart Materials, Adaptive Structures and Intelligent Systems. ASMEDC, 2010. http://dx.doi.org/10.1115/smasis2010-3705.

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The current study explores the use of a steady-state hyperchaotic signal to probe a system for state-space geometry changes used for structural health monitoring applications. This is an extension of a previous chaotic interrogation technique approach that exploited the intrinsic high sensitivity of chaotic systems to subtle changes of the parameters. The enhanced technique proposed in this paper explores a novel structural excitation, namely a hyperchaotic excitation, which exhibits a chaotic behavior wherein at least two Lyapunov exponents are positive due to stretching of the phase space in multiple directions. A feature called average local attractor variance ratio (ALAVR), which is based on attractor geometry, is used to compare the geometry of a baseline attractor to a test attractor. The enhanced technique is applied to analytically and experimentally analyze the response of an 8-degree-of-freedom system to the hyperchaotic excitation for the sake of damage assessment. A comparison between the results obtained from current hyperchaotic excitation vs. a chaotic excitation highlights the higher sensitivity of the hyperchaotic excitation. Thus, hyperchaotic interrogation can be used as an alternative damage assessment technique when increased sensitivity to small amounts of damage is required.

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Pumhössel, Thomas. "Investigating Modal Energy Redistributions in Mechanical Systems With Impulsive Stiffness Excitation by Using Effective Damping Measures". In ASME 2018 International Design Engineering Technical Conferences and Computers and Information in Engineering Conference. American Society of Mechanical Engineers, 2018. http://dx.doi.org/10.1115/detc2018-85524.

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In the present contribution, alternating energy transfers across modes of vibration, induced by impulsive stiffness excitation applied at equidistant instants of time are investigated. Therefore, effective damping measures are used, and it is shown that they clearly indicate modal energy transfers and their effect on the decay rate of transient vibrations. It is demonstrated that outstanding values of the time span between adjacent impulses exist, where a strong energy transfer to higher modes, which possess enhanced damping properties, occurs. Hence, the modal redistribution of vibration energy allows the intrinsic structural damping to be more efficient, resulting in a much faster decrease of vibrations compared to the system without impulsive excitation. It is demonstrated that the effective damping measures provide a proper method to investigate mechanical systems with impulsive stiffness excitation.

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