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Littérature scientifique sur le sujet « Isolated electrons »

Auteur : Grafiati

Publié le 9 mars 2023

Mis à jour le 10 mars 2023

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Articles de revues sur le sujet "Isolated electrons"

Bowen, Kit. « Interactions of electrons with isolated biomolecules ». Nanomedicine : Nanotechnology, Biology and Medicine 2, n^o 4 (décembre 2006) : 296. http://dx.doi.org/10.1016/j.nano.2006.10.086.

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Dewi, Herlina Arianita, Fanben Meng, Barindra Sana, Chunxian Guo, Birgitta Norling, Xiaodong Chen et Sierin Lim. « Investigation of electron transfer from isolated spinach thylakoids to indium tin oxide ». RSC Adv. 4, n^o 90 (2014) : 48815–20. http://dx.doi.org/10.1039/c4ra07070d.

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MISHRA, M. K., et A. PHUKAN. « Electron heating in a multi-dipole plasma by electrostatic plugging ». Journal of Plasma Physics 79, n^o 2 (12 septembre 2012) : 153–61. http://dx.doi.org/10.1017/s0022377812000815.

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AbstractThe effect of the electrostatic confinement potential on electron number densities and electron temperatures under bi-Maxwellian approximation for electron distribution function has been studied in an electrostatically plugged multi-dipole argon plasma system. Electrostatic plugging is implemented by biasing the electrically isolated multi-dipole magnetic cage. Experimental results show that the density ratio (N) and temperature ratio (T) of the two electron groups can be controlled by changing the voltage applied to the magnetic cage. Out of the two groups of electrons, one group has the cold electrons, which are plasma electrons produced by the ionization process, and the other group has the hot primary electrons.

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Boyd, John K. « Electron Spin Transition Solution Applicable to an Ensemble of Isolated Electrons ». Journal of Magnetic Resonance 139, n^o 1 (juillet 1999) : 109–25. http://dx.doi.org/10.1006/jmre.1999.1770.

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Aksnes, A., J. Stadsnes, J. Bjordal, N. Østgaard, R. R. Vondrak, D. L. Detrick, T. J. Rosenberg, G. A. Germany et D. Chenette. « Instantaneous ionospheric global conductance maps during an isolated substorm ». Annales Geophysicae 20, n^o 8 (31 août 2002) : 1181–91. http://dx.doi.org/10.5194/angeo-20-1181-2002.

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Abstract. Data from the Polar Ionospheric X-ray Imager (PIXIE) and the Ultraviolet Imager (UVI) on board the Polar satellite have been used to provide instantaneous global conductance maps. In this study, we focus on an isolated substorm event occurring on 31 July 1997. From the PIXIE and the UVI measurements, the energy spectrum of the precipitating electrons can be derived. By using a model of the upper atmosphere, the resulting conductivity values are generated. We present global maps of how the 5 min time-averaged height-integrated Hall and Pedersen conductivities vary every 15 min during this isolated substorm. The method presented here enables us to study the time development of the conductivities, with a spatial resolution of ~ 700 km. During the substorm, a single region of enhanced Hall conductance is observed. The Hall conductance maximum remains situated between latitudes 64 and 70 corrected geomagnetic (CGM) degrees and moves eastward. The strongest conductances are observed in the pre-midnight sector at the start of the substorm expansion. Toward the end of the substorm expansion and into the recovery phase, we find the Hall conductance maximum in the dawn region. We also observe that the Hall to Pedersen conductance ratio for the regions of maximum Hall conductance is increasing throughout the event, indicating a hardening of the electron spectrum. By combining PIXIE and UVI measurements with an assumed energy distribution, we can cover the whole electron energy range responsible for the conductances. Electrons with energies contributing most to the Pedersen conductance are well covered by UVI while PIXIE captures the high energetic component of the precipitating electrons affecting the Hall conductance. Most statistical conductance models have derived conductivities from electron precipitation data below approximately 30 keV. Since the intensity of the shortest UVI-wavelengths (LBHS) decreases significantly at higher electron energies, the UVI electron energy range is more or less comparable with the energy ranges of the statistical models. By calculating the conductivities from combined PIXIE and UVI measurements to compare with the conductivities from using UVI data only, we observe significant differences in the Hall conductance. The greatest differences are observed in the early evening and the late morning sector. We therefore suggest that the existing statistical models underestimate the Hall conductance.Key words. Ionosphere (auroral ionosphere, particle precipitation) – Magnetospheric physics (storms and substorms)

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Lazuchenkov, D. N., et N. M. Lazuchenkov. « Mathematical modeling of probe measurements in a supersonic flow of a four-component collisionless plasma ». Technical mechanics 2020, n^o 4 (10 décembre 2020) : 97–109. http://dx.doi.org/10.15407/itm2020.04.097.

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The aim of this work is the development of a procedure for extracting the plasma electron density and temperature and ion composition from the current-voltage characteristic (C –V characteristic) of an isolated probe system of cylindrical electrodes. The plasma is four-component and consists of electrons, ions of two species with significantly different masses, and neutrals. The measuring probe and the reference electrode of the probe system may be made up of several cylinders. The electrodes of the probe system are placed transversely to a supersonic flow of a low-temperature collisionless plasma with a specified mass velocity. Using the familiar theoretical and experimental relationships for the ion and electron currents to a cylinder, a mathematical model of current collection is constructed for an isolated probe system at an arbitrary ratio of the electrode surface areas. The model includes the calculation of the equilibrium potential of the reference electrode as a function of the probe bias voltage. A procedure is developed for the identification of local plasma parameters using a priori information on the plasma properties and the experimental conditions. The effect of the electron density and temperature and the ion composition on the probe current of the isolated probe system at different ratios of the current-collecting electrode surface areas is studied. The ranges of the probe bias potentials and the values of the electrode surface area ratio that maximize and minimize the effect of the sought-for parameters on the probe current are determined. The quantitative restrictions on the bias potentials and the surface area ratio obtained in this study are used in the probe measurement procedure and in the objective function for comparing the theoretical approximation of the probe current with the measured I– characteristics. A numerical simulation of probe measurements under the ionospheric conditions was conducted to verify the efficiency of the procedure for extracting the local parameters of a four-component plasma from the electron branch of the I –V characteristic of an isolated probe system. The results obtained may be used in ionospheric plasma diagnostics onboard nanosatellites.

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Hirano, Shin-ichi, Sota Ihara, Satoshi Wakai, Yuma Dotsuta, Kyohei Otani, Toru Kitagaki, Fumiyoshi Ueno et Akihiro Okamoto. « Novel Methanobacterium Strain Induces Severe Corrosion by Retrieving Electrons from Fe0 under a Freshwater Environment ». Microorganisms 10, n^o 2 (25 janvier 2022) : 270. http://dx.doi.org/10.3390/microorganisms10020270.

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Methanogens capable of accepting electrons from Fe0 cause severe corrosion in anoxic conditions. In previous studies, all iron-corrosive methanogenic isolates were obtained from marine environments. However, the presence of methanogens with corrosion ability using Fe0 as an electron donor and their contribution to corrosion in freshwater systems is unknown. Therefore, to understand the role of methanogens in corrosion under anoxic conditions in a freshwater environment, we investigated the corrosion activities of methanogens in samples collected from groundwater and rivers. We enriched microorganisms that can grow with CO2/NaHCO3 and Fe0 as the sole carbon source and electron donor, respectively, in ground freshwater. Methanobacterium sp. TO1, which induces iron corrosion, was isolated from freshwater. Electrochemical analysis revealed that strain TO1 can uptake electrons from the cathode at lower than −0.61 V vs SHE and has a redox-active component with electrochemical potential different from those of other previously reported methanogens with extracellular electron transfer ability. This study indicated the corrosion risk by methanogens capable of taking up electrons from Fe0 in anoxic freshwater environments and the necessity of understanding the corrosion mechanism to contribute to risk diagnosis.

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Holmes, Dawn E., Julie S. Nicoll, Daniel R. Bond et Derek R. Lovley. « Potential Role of a Novel Psychrotolerant Member of the Family Geobacteraceae, Geopsychrobacter electrodiphilus gen. nov., sp. nov., in Electricity Production by a Marine Sediment Fuel Cell ». Applied and Environmental Microbiology 70, n^o 10 (octobre 2004) : 6023–30. http://dx.doi.org/10.1128/aem.70.10.6023-6030.2004.

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ABSTRACT Previous studies have shown that members of the family Geobacteraceae that attach to the anodes of sediment fuel cells are directly involved in harvesting electricity by oxidizing organic compounds to carbon dioxide and transferring the electrons to the anode. In order to learn more about this process, microorganisms from the anode surface of a marine sediment fuel cell were enriched and isolated with Fe(III) oxide. Two unique marine isolates were recovered, strains A1T and A2. They are gram-negative, nonmotile rods, with abundant c-type cytochromes. Phylogenetic analysis of the 16S rRNA, recA, gyrB, fusA, rpoB, and nifD genes indicated that strains A1T and A2 represent a unique phylogenetic cluster within the Geobacteraceae. Both strains were able to grow with an electrode serving as the sole electron acceptor and transferred ca. 90% of the electrons available in their organic electron donors to the electrodes. These organisms are the first psychrotolerant members of the Geobacteraceae reported thus far and can grow at temperatures between 4 and 30°C, with an optimum temperature of 22°C. Strains A1T and A2 can utilize a wide range of traditional electron acceptors, including all forms of soluble and insoluble Fe(III) tested, anthraquinone 2,6-disulfonate, and S0. In addition to acetate, both strains can utilize a number of other organic acids, amino acids, long-chain fatty acids, and aromatic compounds to support growth with Fe(III) nitrilotriacetic acid as an electron acceptor. The metabolism of these organisms differs in that only strain A1T can use acetoin, ethanol, and hydrogen as electron donors, whereas only strain A2 can use lactate, propionate, and butyrate. The name Geopsychrobacter electrodiphilus gen. nov., sp. nov., is proposed for strains A1T and A2, with strain A1T (ATCC BAA-880T; DSM 16401T; JCM 12469) as the type strain. Strains A1T and A2 (ATCC BAA-770; JCM 12470) represent the first organisms recovered from anodes that can effectively couple the oxidation of organic compounds to an electrode. Thus, they may serve as important model organisms for further elucidation of the mechanisms of microbe-electrode electron transfer in sediment fuel cells.

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CARLI, TANCREDI, DOMINIK DANNHEIM et LORENZO BELLAGAMBA. « EVENTS WITH ISOLATED CHARGED LEPTONS AND LARGE MISSING TRANSVERSE MOMENTUM AT HERA ». Modern Physics Letters A 19, n^o 25 (20 août 2004) : 1881–902. http://dx.doi.org/10.1142/s0217732304015142.

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Striking events with isolated charged leptons, large missing transverse momentum and large transverse momentum of the hadronic final state [Formula: see text] were observed at the electron proton collider HERA in a data sample corresponding to an integrated luminosity of about 130 pb-1. The H1 collaboration observed 11 events with isolated electrons or muons and with [Formula: see text]. Only 3.4±0.6 events were expected from Standard Model (SM) processes. Six of these events have [Formula: see text], while 1.3±0.3 events were expected. The ZEUS collaboration observed good agreement with the SM. However, ZEUS found two events with a similar event topology, but tau leptons instead of electrons or muons in the final state. Only 0.2±0.05 events were expected from SM processes. For various hypotheses, the compatibility of the experimental results was investigated with respect to the SM and with respect to possible explanations beyond the SM. Prospects for the high-luminosity HERA-II data taking period are given.

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Furutani, Y., H. Totsuji, K. Mima et H. Takabe. « Internal structure of a partially ionized heavy ion. Isolated ion model ». Laser and Particle Beams 7, n^o 3 (août 1989) : 581–88. http://dx.doi.org/10.1017/s0263034600007552.

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An effective potential and an associated electron density in a partially ionized high-Z ion are evaluated within the framework of the Thomas–Fermi–Dirac–Weizsäcker statistical model of atoms. The results are then injected as an initial input into the one-electron Schrödinger equation, a procedure based on the density functional theory. The self-consistency between the two approaches is examined. For a partially ionized ion at zero and finite temperatures, a number of bound electrons is counted by a sum over the principal quantum number, which diverges due to the contribution from shallow bound (Rydberg) levels. A truncation of this sum is devised by application of the Planck–Larkin scheme to the Fermi distribution

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Thèses sur le sujet "Isolated electrons"

DI, MATTEO LEONARDO. « CMS ECAL intercalibration with electrons from W and Z decays and Search for the Standard Model Higgs boson in the H > ; WW > ; lvqq channel with the CMS detector ». Doctoral thesis, Università degli Studi di Milano-Bicocca, 2013. http://hdl.handle.net/10281/41813.

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The usage of isolated electrons from W and Z leptonic decays for the intercalibration of the CMS ECAL single channel response is described. The statistics of 5 fb−1, collected at LHC in 2011 at sqrt(s)=7 TeV, allowed to reach a statistical precision of about 1% in the central part of the ECAL barrel and about 4% in the ECAL endcaps. The results obtained with this method are combined with others, and the impact on the Higgs to di-photon search is shown. Subsequently, the thesis describes the search strategy for the Higgs boson in the H > WW > lvqq final state. The results are based on a data sample corresponding to an integrated luminosity of 17 fb−1 of proton-proton collisions accumulated during the 2011-2012 LHC run. The standard model Higgs boson is excluded at 95% confidence level in the mass ranges [215 − 490] + [525 − 600] GeV.

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Simpson, Edward Thomas. « Electron holography of isolated and interacting magnetic nanocrystals ». Thesis, University of Cambridge, 2009. https://www.repository.cam.ac.uk/handle/1810/252128.

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Fuller, G. W. « Electron microscopy and image analysis of isolated myosin filaments ». Thesis, Imperial College London, 1987. http://hdl.handle.net/10044/1/38322.

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Archer, Anthony D. « Spectroscopic studies of field-induced electron emission from isolated microstructures ». Thesis, Aston University, 1992. http://publications.aston.ac.uk/8241/.

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A detailed investigation has been undertaken into the field induced electron emission (FIEE) mechanism that occurs at microscopically localised `sites' on uncoated and dielectric coated metallic electrodes. These processes have been investigated using two dedicated experimental systems that were developed for this study. The first is a novel combined photo/field emission microscope, which employs a UV source to stimulate photo-electrons from the sample surface in order to generate a topographical image. This system utilises an electrostatic lens column to provide identical optical properties under the different operating conditions required for purely topographical and combined photo/field imaging. The system has been demonstrated to have a resolution approaching 1m. Emission images have been obtained from carbon emission sites using this system to reveal that emission may occur from the edge triple junction or from the bulk of the carbon particle. An existing UHV electron spectrometer has been extensively rebuilt to incorporate a computer control and data acquisition system, improved sample handling and manipulation and a specimen heating stage. Details are given of a comprehensive study into the effects of sample heating on the emission process under conditions of both bulk and transient heating. Similar studies were also performed under conditions of both zero and high applied field. These show that the properties of emission sites are strongly temperature and field dependent thus indicating that the emission process is `non-metallic' in nature. The results have been shown to be consistent with an existing hot electron emission model.

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McKinley, A. J. « A study of matrix isolated ions by electron spin resonance spectroscopy ». Thesis, University of Canterbury. Chemistry, 1985. http://hdl.handle.net/10092/9393.

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The objective of this project was to attempt to trap small molecular ions in an argon matrix and study the structure of these ions using electron spin resonance spectroscopy. To this end an apparatus designed for matrix isolation ESR was developed in a number of stages concurrently with matrix isolation experiments. Early experiments used conventional electron impact ion sources but these sources were found to be unsuitable for producing ions to trap in an argon matrix due to the energy of the ions. In these experiments problems arose due to contamination of the matrix by methyl radicals and hydrogen and nitrogen atoms which obscured the spectral range of interest that is around g = 2. Vacuum ultra-violet photolysis was used to produce ions and was found to be successful. The molecular ion NH₃⁺ has been trapped in an argon matrix at 14K by photo-ionisation of an NH₃/Ar mixture during deposition. The NH₃⁺ cation has been found to be rigidly trapped in the argon matrix and exhibits a powder-type ESR spectrum. The derived magnetic parameters agree well with those obtained by other workers in different matrices. A strong reversible temperature dependence of the linewidth of the NH₃⁺ spectrum has been observed. Argon resonance photolysis of methyl iodide and methyl bromide argon mixtures during deposition was found to produce free methyl radicals in addition to methyl radicals interacting weakly with a high spin nucleus or nuclei. These species have been tentatively assigned on chemical evidence as CH3̇ ⋯ and CH3̇ ⋯ Br- respectively. The complexity of the spectra resulted in complete solution not being possible.

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York, Jr John Benson. « An Isolated Micro-Converter for Next-Generation Photovoltaic Infrastructure ». Diss., Virginia Tech, 2013. http://hdl.handle.net/10919/19326.

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Photovoltaic (PV) systems are a rapidly growing segment in the renewable energy industry. Though they have humble origins and an uncertain future, the commercial viability of PV has significantly increased, especially in the past decade. In order to make PV useful, however, significant effort has to go into the power conditioning systems that take the low-voltage dc from the panel and create utility compatible ac output. Popular architectures for this process include the centralized inverter and the distributed micro-inverter, each with its own advantages and disadvantages. One attempt to retain the advantages of both architectures is to centralize the inverter function but construct PV panel-level micro-converters which optimize the panel output and condition the power for the inverter. The main focus of this work is to explore the technical challenges that face the evolution of the dc-dc micro-converter and to use them as a template for a vertically integrated design procedure.

The individual chapters focus on different levels of the process: topology, modulation and control, transient mitigation, and steady-state optimization. Chapter 2 introduces a new dc-dc topology, the Integrated Boost Resonant (IBR) converter, born out of the natural design requirements for the micro-converter, such as high CEC efficiency, simple structure, and inherent Galvanic isolation. The circuit is a combination of a traditional PWM boost converter and a discontinuous conduction mode (DCM), series resonant circuit. The DCM operation of the high-frequency transformer possesses much lower circulating energy when compared to the traditional CCM behavior. When combined with zero-current-switching (ZCS) for the output diode, it results in a circuit with a high weighted efficiency of 96.8%. Chapter 3 improves upon that topology by adding an optimized modulation scheme to the control strategy. This improves the power stage efficiency at nominal input and enhances the available operating range. The new, hybrid-frequency method utilizes areas where the modulator operates in constant-on, constant-off, and fixed-frequency conditions depending on duty cycle, the resonant period length, and the desired input range. The method extends the operating range as wide as 12-48V and improves the CEC efficiency to 97.2% in the 250-W prototype. Chapter 4 considers the soft-start of the proposed system, which can have a very large capacitive load from the inverter. A new capacitor-transient limited (CTL) soft-start method senses the ac transient across the resonant capacitor, prematurely ending the lower switch on-time in order to prevent an excessive current spike. A prototype design is then applied to the IBR system, allowing safe system startup with a range of capacitive loads from 2Î¼F to 500Î¼F and a consistent peak current without the need for current sensing. Chapter 5 further investigates the impact of voltage ripple on the PV output power. A new method for analyzing the maximum power point tracking (MPPT) efficiency is proposed based on panel-derived models. From the panel model, an expression demonstrating the MPPT efficiency is derived, along with a ripple â "budgetâ " for the harmonic sources. These ripple sources are then analyzed and suggestions for controlling their contributions are proposed that enable circuit designers to make informed and cost-effective design decisions. Chapter 6 illustrates how results from a previous iteration can provide a basis for the next generation\'s design. A zero-voltage-switching (ZVS) version of the circuit in Chapter 2 is proposed, requiring only two additional MOSFETs and one inductor on the low-voltage side. The maximum switching frequency is then increased from 70kHz to 170kHz, allowing for a 46% reduction in converter volume (from 430cm3 to 230cm3) while retaining greater than 97% weighted efficiency.

Ph. D.

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Stetler, Fredrik. « Isolated magnetic field structures in the Saturn magnetosphere ». Thesis, KTH, Rymd- och plasmafysik, 2017. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-214821.

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This report’s primary focus is to use the data gathered by the Cassini satellite and analyzeits magnetic field data around Saturn. By looking for isolated changes in magneticfield values locations of potential plasmoids can be determined and examined. Theseso called plasmoids are pockets of higher density plasma ,associated with an increaseor decrease of the magnetic field strength, inside the magnetosheath, which may be importantfor the interaction between the solar wind plasma and the magnetosphere. Thestudy has been made over 7 years, from the beginning of 2010 to the end of 2016. Duringthis period a number of magnetic field structures have been found and documentedin this report, along with analyzing some of their properties such as their width andmagnetic field strength.
Denna rapports primära fokus är att använda data insamlad av Cassini satelliten ochanalysera dess magnetiska fältdata runt Saturnus. Genom att titta efter isolerade förändringari magnetiska fältvärdena går det att lokalisera och examinera potentiella plasmoider.Dessa så kallade plasmoider är fickor med högre densitet av plasma, associerademed en ökning eller minskning av magnetisk fältdata, inne i magnetoskiktet, vilket kanvara viktigt för interaktionen mellan solvindens plasma och magnetosfären. Studien hargjorts över 7 års tid, från början av 2010 till slutet av 2016. Under denna period harett antal magnetiska fältstrukturer hittats och dokumenterats i denna rapport, genom attanalysera några av deras egenskaper så som deras bredd och magnetisk fältstyrka.

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Jayanty, Vivi. « Miniaturized electron-impact-ionization pumps using double-gated isolated vertically aligned carbon nanotube arrays ». Thesis, Massachusetts Institute of Technology, 2012. http://hdl.handle.net/1721.1/75659.

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Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 2012.
Cataloged from PDF version of thesis.
Includes bibliographical references (p. 67-71).
There is a need for microscale vacuum pumps that can be readily integrated with other MEMS and electronic components at the chip-scale level. Miniaturized ion pumps exhibit favorable scaling down because they are surface-limited and miniaturization increases the ratio between the active surface and the chamber volume, resulting in enhanced ionization and pump rates. Therefore, scaled-down ion pumps are a promising choice for a variety of applications including portable mass spectrometers and sub-mm wavelength vacuum amplifiers. Our micropump architecture consist of a field-emission electron source that is an array of double-gated isolated vertically aligned carbon nanotubes (VA-CNTs), an electronimpact- ionization region, and a non-evaporative ion-implantation getter. Single-gated VA-CNT FEAs were tested as field emitters in high vacuum (10-9 Torr). The current density of the tested device is ~0.5A/cm2 (total current of 0.4mA) and a field enhancement factor of 1.41 x106 V/cm was measured, which is comparable to the simulation results by COMSOL. Two ways to fabricate double-gated VA-CNT FEAs were reported: one has the focus gate in plane with the extractor gate and the other has the focus gate above the extractor gate. Due to problems on fabrication process of double-gated VA-CNTs (short circuit between emitters, extractor gate, and focus gate), we were not able to collect four-terminal measurement, electron-impact-ionization, and pump data. However, procedure on how to collect and analyze field emission data with two gates to find [beta]G and [beta]F was described. In addition, procedures on how to collect and analyze data on electron impact ionization pump were also presented.
by Vivi Jayanty.
S.M.

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Monzon, Eric V. « Seismic response of isolated bridge superstructure to incoherent ground motions ». abstract and full text PDF (free order & ; download UNR users only), 2006. http://0-gateway.proquest.com.innopac.library.unr.edu/openurl?url_ver=Z39.88-2004&rft_val_fmt=info:ofi/fmt:kev:mtx:dissertation&res_dat=xri:pqdiss&rft_dat=xri:pqdiss:1438943.

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Murdoch, Fiona. « Evaluation of a manganese oxidising bacterium isolated from an upland water source ». Thesis, University of the West of Scotland, 2000. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.311781.

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Livres sur le sujet "Isolated electrons"

Joshua, Jortner, Bixon M, Prigogine I et Rice Stuart Alan 1932-, dir. Electron transfer- from isolated molecules to biomolecules. New York : J. Wiley, 1999.

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Archer, Anthony David. Spectroscopic studies of field-induced electron emission from isolated microstructures. Birmingham : Aston University. Department of Electrical Engineering and Applied Physics, 1992.

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United States. National Aeronautics and Space Administration., dir. Implementing direct, spatially isolated problems on transputer networks. [Washington, DC] : National Aeronautics and Space Administration, 1988.

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Pontifex, Gregory H. A combined scanning tunnelling microscopy and electron microscopy study of metal electrodeposits isolated from anodic aluminum oxide films and silver colloid particles isolated from a hydrosol. Ottawa : National Library of Canada = Bibliothèque nationale du Canada, 1991.

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Burrow, I. J. OSCADY : A computer program to model capacities, queues and delays at isolated traffic signal junctions. Crowthorne : Transport and Road Research Laboratory, 1987.

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Burrow, I. J. OSCADY : A computer program to model capacities, queues and delays at isolated traffic signal junctions. Crowthorne, Berks : Transport and Road Research Laboratory, Traffic Group Traffic Management Division, 1987.

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Al-Amri, Wafa M. Investigation of the structure of photosystem 1 isolated from the chloroplast of higher plants and microalgae : Purification, characterisation and electron microscopy. Manchester : UMIST, 1998.

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Jortner, Joshua, Ilya Prigogine, Stuart A. Rice et M. Bixon. Electron Transfer : From Isolated Molecules to Biomolecules, Part 1. Wiley & Sons, Incorporated, John, 2009.

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Jortner, Joshua, Ilya Prigogine, Stuart A. Rice et M. Bixon. Electron Transfer : From Isolated Molecules to Biomolecules, Volume 106, Part 1. Wiley & Sons, Incorporated, John, 2007.

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Jortner, Joshua, Ilya Prigogine, Stuart A. Rice et M. Bixon. Electron Transfer : From Isolated Molecules to Biomolecules, Volume 107, Part 2. Wiley & Sons, Incorporated, John, 2007.

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Chapitres de livres sur le sujet "Isolated electrons"

Wang, Y. J., B. D. McCombe et W. Schaff. « Isolated Impurities, Impurity Bands and the Metal-Insulator Transition in Modulation-Doped Multiple-Quantum-Well Structures in Magnetic Fields ». Dans Localization and Confinement of Electrons in Semiconductors, 314–22. Berlin, Heidelberg : Springer Berlin Heidelberg, 1990. http://dx.doi.org/10.1007/978-3-642-84272-6_33.

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Batarseh, Issa, et Ahmad Harb. « Isolated Switch-Mode DC-DC Converters ». Dans Power Electronics, 273–345. Cham : Springer International Publishing, 2017. http://dx.doi.org/10.1007/978-3-319-68366-9_5.

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Thiele, Stefan. « Single Electron Transistor ». Dans Read-Out and Coherent Manipulation of an Isolated Nuclear Spin, 13–21. Cham : Springer International Publishing, 2015. http://dx.doi.org/10.1007/978-3-319-24058-9_2.

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Batarseh, Issa, et Ahmad Harb. « Non-isolated Switch Mode DC-DC Converters ». Dans Power Electronics, 173–271. Cham : Springer International Publishing, 2017. http://dx.doi.org/10.1007/978-3-319-68366-9_4.

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Herper, Heike C., Barbara Brena, Carla Puglia, Sumanta Bhandary, Heiko Wende, Olle Eriksson et Biplab Sanyal. « Electronic Structure of Isolated Molecules ». Dans SpringerBriefs in Applied Sciences and Technology, 25–34. Singapore : Springer Singapore, 2020. http://dx.doi.org/10.1007/978-981-15-3719-6_4.

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Warley, Alice. « X-Ray Microanalysis of Freshly Isolated Cells in Suspension ». Dans Electron Probe Microanalysis, 169–79. Berlin, Heidelberg : Springer Berlin Heidelberg, 1989. http://dx.doi.org/10.1007/978-3-642-74477-8_13.

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Bixon, M., et Joshua Jortner. « Electron Transfer-from Isolated Molecules to Biomolecules ». Dans Advances in Chemical Physics, 35–202. Hoboken, NJ, USA : John Wiley & Sons, Inc., 2007. http://dx.doi.org/10.1002/9780470141656.ch3.

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Grozema, Ferdinand C., Laurens D. A. Siebbeles, Gerwin H. Gelinck et John M. Warman. « The Opto-Electronic Properties of Isolated Phenylenevinylene Molecular Wires ». Dans Molecular Wires and Electronics, 135–64. Berlin, Heidelberg : Springer Berlin Heidelberg, 2005. http://dx.doi.org/10.1007/b136065.

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Dashek, William V. « Methods for the Identification of Isolated Plant Cell Organelles ». Dans Methods in Plant Electron Microscopy and Cytochemistry, 161–67. Totowa, NJ : Humana Press, 2000. http://dx.doi.org/10.1007/978-1-59259-232-6_11.

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Eberhardt, W. « Spectroscopy and Dynamics of the Electronic Decay of Core Electron Excitations in Isolated and Chemisorbed Molecules ». Dans Springer Series in Surface Sciences, 203–62. Berlin, Heidelberg : Springer Berlin Heidelberg, 1995. http://dx.doi.org/10.1007/978-3-642-79024-9_6.

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Actes de conférences sur le sujet "Isolated electrons"

Liu, Y. M., W. L. Nighan, D. A. Young et P. M. Fauchet. « Ultrafast carrier dynamics in a-Si1-xGex:H alloys ». Dans OSA Annual Meeting. Washington, D.C. : Optica Publishing Group, 1990. http://dx.doi.org/10.1364/oam.1990.wk5.

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The ultrafast carrier dynamics in a-Si1-x-Gex:H alloys (energy gap 1.0 to 1.8 eV) were examined using femtosecond time-resolved spectroscopy. Optical pulses from an amplified CPM laser (photon energy = 2 eV and pulse duration d fsec) were used to create a large density (1018 to 1021 cm3) of excited carriers. The time dependence of changes in the reflectivity and transmission were measured with a probe pulse obtained from a white light continuum. By varying the energy of the probe pulse photons to be above or below the energy gap in these materials, the ultrafast electronic and thermal effects1 can be isolated. The effective lifetime of carriers near the mobility edge was found to depend strongly upon the carrier density, becoming as short as 1 ps for the highest densities. The ultrafast rise in lattice temperature indicates that electrons and holes are recombining nonradiatively. The carrier lifetime scales with density in a manner that suggests that the mechanism is Auger recombination2 of geminate electron-hole pairs.

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Zhu, Y., E. Y. Xu et T. F. Gallagher. « Electron Angular Distributions and Branching Ratios of the SrI 5p3/2ns1/2 and 5p1/2ns1/2 J = 1 Autoionizing States ». Dans Multiple Excitations of Atoms. Washington, D.C. : Optica Publishing Group, 1986. http://dx.doi.org/10.1364/mea.1986.tuc10.

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Measurements of the energy distributions, Branching ratios, and angular distributions of electrons ejected from SrI 5p3/2ns1/2 and 5p1/2ns1/2 J=1 doubly excited states with n ranging from 10 to 20 in the autoionization to the SrII 5s, 4d, and 5p ion state have been made by the techniques of Isolated-Core-Excitation and Time-of-Flight Spectroscopy. The experiment consists of three Nd:YAG laser pumped tunable dye lasers which excite the Sr atoms in an atomic beam from the ground state to the 5p3/2ns1/2 or 5p1/2ns1/2 J=1 autoionizing states. The autoionizing electrons are analyzed in energy and angle by a time of flight analyzer, and the electrons and residual ions are collected by two microchannel plate detectors respectively and sent to the computer through the Boxcar Integrators. The measurements show that the doubly excited SrI 5p3/2ns1/2 and 5p1/2ns1/2 J=1 states autoionize predominantly to the excited SrII 4d ion states with a p or f electron. The asymmetry parameter varies continuously within the line profile of the 5p3/2ns1/2 J=1 states as the manifestation of the localized interaction between the SrI 5p3/2ns1/2 and 5p1/2ns1/2 J=1 autoionizing series. This variation is distinguished from that caused by the interference between the excitation to the bound part of the autoionizing state and underlying continua.

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Ditmire, T., J. W. G. Tisch, E. Springate, M. B. Mason, N. Hay, R. A. Smith, J. P. Marangos et M. H. R. Hutchinson. « High Energy Explosion of Super-Heated Atomic Clusters ». Dans Applications of High Field and Short Wavelength Sources. Washington, D.C. : Optica Publishing Group, 1997. http://dx.doi.org/10.1364/hfsw.1997.thb2.

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Though the nature of intense, short pulse laser interactions with single atoms and solid targets has been the subject of extensive experimental and theoretical investigation over the last 15 years, only recently has the nature of intense laser interactions with van der Waals bonded atomic clusters of 20 -100 Å been addressed in experiments. These experiments have suggested that the laser-cluster interaction is much more energetic than that of isolated atoms, producing bright x-ray emission (100 - 5000 eV photons) when a low density gas containing clusters is illuminated [1,2]. While experiments have indicated indirect evidence for keV electron production in the cluster through time resolved x-ray spectroscopic data [2], until recently no direct data on the exact nature of the kinetic energies produced by the intense irradiation of clusters existed. In this paper we present the first energy distribution measurements of both electrons and ions resulting from the interaction of a femtosecond laser pulse with van der Waals bonded clusters. We find that the cluster is rapidly heated by collisional inverse bremsstrahlung. This heats a sizable fraction of the electrons in the cluster to a temperature above 1 keV. The super-heated cluster then explodes, ejecting ions with substantial kinetic energy. In fact, ions with energy up to 1 MeV are produced in Xe clusters.

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Anand, Sandeep V., D. Roy Mahapatra, Niraj Sinha, J. T. W. Yeow et R. V. N. Melnik. « Field Emission Efficiency of a Carbon Nanotube Array Under Parasitic Nonlinearities ». Dans ASME 2010 International Mechanical Engineering Congress and Exposition. ASMEDC, 2010. http://dx.doi.org/10.1115/imece2010-39558.

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Carbon Nanotubes (CNTs) grown on substrates are potential electron sources in field emission applications. Several studies have reported the use of CNTs in field emission devices, including field emission displays, X-ray tube, electron microscopes, cathode-ray lamps, etc. Also, in recent years, conventional cold field emission cathodes have been realized in micro-fabricated arrays for medical X-ray imaging. CNT-based field emission cathode devices have potential applications in a variety of industrial and medical applications, including cancer treatment. Field emission performance of a single isolated CNT is found to be remarkable, but the situation becomes complex when an array of CNTs is used. At the same time, use of arrays of CNTs is practical and economical. Indeed, such arrays on cathode substrates can be grown easily and their collective dynamics can be utilized in a statistical sense such that the average emission intensity is high enough and the collective dynamics lead to longer emission life. The authors in their previous publications had proposed a novel approach to obtain stabilized field emission current from a stacked CNT array of pointed height distribution. A mesoscopic modeling technique was employed, which took into account electro-mechanical forces in the CNTs, as well as transport of conduction electron coupled with electron–phonon induced heat generation from the CNT tips. The reported analysis of pointed arrangements of the array showed that the current density distribution was greatly localized in the middle of the array, the scatter due to electrodynamic force field was minimized, and the temperature transients were much smaller compared to those in an array with random height distribution. In the present paper we develop a method to compute the emission efficiency of the CNT array in terms of the amount of electrons hitting the anode surface using trajectory calculations. Effects of secondary electron emission and parasitic capacitive nonlinearity on the current-voltage signals are accounted. Field emission efficiency of a stacked CNT array with various pointed height distributions are compared to that of arrays with random and uniform height distributions. Effect of this parasitic nonlinearity on the emission switch-on voltage is estimated by model based simulation and Monte Carlo method.

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Kohl, John L. « Instrumentation for Ultraviolet Spectroscopy of the Extended Solar Corona ». Dans Space Optics for Astrophysics and Earth and Planetary Remote Sensing. Washington, D.C. : Optica Publishing Group, 1988. http://dx.doi.org/10.1364/soa.1988.tuc1.

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Instrumentation and plasma diagnostic techniques are being developed to obtain a detailed empirical description of solar wind acceleration regions at heights between the coronal base and about 10 solar radii from sun center (R⊙). The goal of this work is to determine a sufficient number of observational parameters to constrain, significantly, theories of solar wind acceleration, coronal heating and solar wind composition. Although a substantial amount of data on the electron density structure of the corona already exists, there are only isolated measurements of other critical plasma parameters, except for observations of regions near the base of the corona. Ultraviolet spectroscopy provides a capability to expand greatly the number of plasma parameters that can be specified by means of remote sensing techniques. Ultraviolet measurements of spectral line profiles determine the random velocity distributions and effective temperature of protons, minor ions and electrons. Ion densities, and chemical abundances are derivable from the collisional component of the observed resonant line intensities. Outflow velocities can be determined from Doppler shifts and Doppler dimming of spectral lines. The instruments which are being developed for remote sensing of the extended corona, consist of an occulted telescope system and a high resolution spectrometer. The basic design was proven on three sounding rocket flights. Initial data on proton temperatures, and solar wind outflow velocities for heliospheric heights between 1.5 and 3.5 solar radii from sun center have been obtained. More powerful instruments are being developed for Spartan (a shuttle deployed subsatellite) and for the SOHO Mission.

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Hulin, D., A. Migus, A. Antonetti, A. Mysyrowicz, H. M. Gibbs, N. Peyghambarian, H. Morkoç et W. T. Masselink. « Exciton Interaction in GaAs-GaAlAs Superlattice ». Dans Picosecond Electronics and Optoelectronics. Washington, D.C. : Optica Publishing Group, 1985. http://dx.doi.org/10.1364/peo.1985.pdp1.

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A blue shift of the exciton line has been recently observed1 in MQWS (53 Å GaAs-53 Å GaAlAs) after femtosecond excitation. This shift has been proved to originate from the presence of large number of excitons in the system, either directly created by resonant pumping or due at longer delay to the pairing of the electrons and holes initially created by band to band excitation at low temperature. This blue shift has not been reported in the bulk material GaAs. This effect being related to the sample structure, it is important to know whether the two-dimensional confinement within a well is the only origin of this new type of exciton interaction or if the superlattice type of the sample has to play a role. Experiments have been performed in MQWS with different barrier and well thicknesses, ranging from the case of thick barriers (in order to minimize the interactions between the wells) to the case where excitonic wave functions overlap over neighboring wells. The experimental results demonstrate the influence of the superlattice structure- A model is developped which takes into account the difference between the bulk material isolated wells and superlattices.

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Guo, Liang, Stephen L. Hodson, Timothy S. Fisher et Xianfan Xu. « Heat Transfer Across Metal-Dielectric Interfaces During Ultrafast-Laser Heating ». Dans ASME 2011 International Mechanical Engineering Congress and Exposition. ASMEDC, 2011. http://dx.doi.org/10.1115/imece2011-64165.

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Heat transfer across a metal-dielectric interface involves coupled transport of electrons and phonons in metal and phonons in dielectric, which can be accomplished by coupling between phonons in metal and dielectric or direct coupling between electrons in metal and phonons in dielectric. Direct electron-phonon coupling across the metal-dielectric interface is neglected in some studies [1, 2] but considered in some others [3–5]. We investigate heat transfer across metal-dielectric interfaces during ultrafast-laser heating by employing transient thermo-reflectance (TTR) measurements on Au-Si samples. With ultrafast-laser heating that creates strong thermal non-equilibrium between electrons and phonons in metal, it is possible to isolate the effect of direct electron-phonon coupling across the interface. Simulation results based on the two-temperature model (TTM) are compared with the measurement results. The comparison shows a strong direct coupling between electrons in metal and phonons in dielectric.

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Jozelj, Miha, Tobja Košir, Darja Bozič, Matej Hočevar, Samo Penič, Aleš Iglič, Marko Jeran et Veronika Kralj - Iglič. « Morphological Parameters of Erythrocyte Extracellular Vesicles at Hypoosmotic and Isoosmotic Conditions ». Dans Socratic Lectures 7. University of Lubljana Press, 2022. http://dx.doi.org/10.55295/psl.2022.d16.

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Extracellular vesicles (EVs) are membrane-enclosed structures of nanometer dimensions. They are formed by cells and can be found in isolates from body fluids. It is indicated that they play important role in intercellular communication in health and disease. In this work we observed the morpholoical parameters of EVs isolated by differential centrifugation from washed erythrocytes, in which vesiculation was accelerated by addition of detergent (sodium dodecyl sulfate). Aliquots of the isolate were suspended medium of two different osmolarities. Isolates were imaged with a scan-ning electron microscope (SEM) and the images were analyzed by using the contours of EVs from which the volume V, surface area S, and relative volume v = (36S3/V2)1/2 were assessed by a geomet-rical model. EVs were considered as spheres or spheroids. The isolates were rich in erythrocyte EVs so that representative sets (86 vesicles at osmolarity of 50 mOsmol/L and 109 vesicles at osmolarity of 300 mOsmol/L) could be outlined. The EVs at osmolarity of 50 mOsmol/L had shapes close to a sphere, while at osmolarity of 300 mOsmol/L they had elongated shapes. The shapes were approxi-mated by prolate spheroids. The average volume/surface area of EVs at osmolarity 50 mOsmol/L were 3.18×105 nm3/2.20×104 nm2, and at osmolarity 300 mOsmol/L they were 4.3×105 nm3/2.79×104 nm2. The respective differences in favor of the values at 300 mOsmol/L were statistically significant and of sufficient power. The relative volume of EVs at 50 mOsmol/L and 300 mOsmol/L were 1 and 0.96, respectively. While the difference in v suggests that, similarly to erythrocytes, water enters EVs in order to attain the Donnan equilibrium, the differences in V and A suggest that selective popping of (larger) EVs in the hypoosmolar sample took place. Keywords: Extracellular vesicles; Erythrocytes; Osmolarity; Differential centrifugation; Scanning electron microscopy (SEM); Morphology; Interdisciplinary connection; Medicine

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Lu, Frank K., Linda Phonharath, Richard R. Mitchell et Behzad Bigdeli. « Flame Suppression Technique in Arc Tracking of Circuit Boards ». Dans ASME 2007 International Mechanical Engineering Congress and Exposition. ASMEDC, 2007. http://dx.doi.org/10.1115/imece2007-41051.

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The problem of arc tracking in power electronic enclosures was studied through simple bench-top experiments aimed at understanding the phenomenon. Experiments were performed to isolate the causes of arc tracking on PCB boards with high-powered electrodes subjected to a Solventol/water mixture contamination. These experiments show that a minimum electrode spacing of 1 mm would be susceptible to arc tracking. A larger spacing of 3.2 mm appears to prevent arc tracking. In the event that arc tracking causes combustion, a passive flame suppression method is indicated. This method comprises of four layers of off-the-shelf expanded metal network. Tests show that the flame is quenched in about one minute, with minimum damage to the plastic enclosure.

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Islam, Rejaul, et Md Istianatur Rahman. « Comparative Performance Analysis of Isolated and Non-Isolated DC-DC Converters with Solar PV Array for EVs Application ». Dans International Conference on Emerging Trends in Engineering and Advanced Science. AIJR Publisher, 2022. http://dx.doi.org/10.21467/proceedings.123.5.

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Modern day’s power electronics converters are very important for each and every electronic device such as portable devices, cell phones, laptop-computers, electric vehicles, etc. For the Electric Vehicles (EVs) the dc-to-dc converters are the best-suited and essential devices on account of their lightweight, high efficiency, smaller size, and high-power density, bi-directionality, reliability, cost-effectiveness. This paper provides a comparative study on non-isolated and isolated power dc-to-dc converters for EVs in which the main power source is PV (photo-voltaic) array module, in addition, a brief idea about design and calculation of passive components of power dc-to-dc isolated and non-isolated converters both in theoretically, and practically with simulation software. Here all the simulation results are tested by MATLAB simulation software and verified that the multi-phase multi-device interleaved boost dc-dc converter (MDIBC) is the best-suited candidate for both low and high power photo-voltaic based EVs due to their compact size, low cost, reliability, multifunctionality, bi-directionality, high efficiency, etc.

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Rapports d'organisations sur le sujet "Isolated electrons"

Tam, Simon, Michel Macler, Michelle E. DeRose et Mario E. Fajardo. Electronic Spectroscopy of B Atoms and B2 Molecules Isolated in Para-H2, Normal-D2, Ne, Ar, Kr, and Xe Matrices. Fort Belvoir, VA : Defense Technical Information Center, mai 2000. http://dx.doi.org/10.21236/ada408930.

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Zheleva, Antoaneta M., Galina D. Nikolova, Yanka D. Karamalakova, Derek T. Ndinteh et Veselina G. Gadjeva. In Vitro Electron Paramagnetic Resonance (EPR) Spectroscopy Study on Radical Scavenging Abilities of an Extract Isolated from Stem Bark of Piptadeniastrum africanum Tree. "Prof. Marin Drinov" Publishing House of Bulgarian Academy of Sciences, février 2019. http://dx.doi.org/10.7546/crabs.2019.02.07.

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Nealson, Kenneth. Final Scientific Report : Bacterial Nanowires and Extracellular Electron Transfer to Heavy Metals and Radionuclides by Bacterial Isolates from DOE Field Research Centers. Office of Scientific and Technical Information (OSTI), décembre 2016. http://dx.doi.org/10.2172/1337164.

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Raychev, Nikolay. Can human thoughts be encoded, decoded and manipulated to achieve symbiosis of the brain and the machine. Web of Open Science, octobre 2020. http://dx.doi.org/10.37686/nsrl.v1i2.76.

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This article discusses the current state of neurointerface technologies, not limited to deep electrode approaches. There are new heuristic ideas for creating a fast and broadband channel from the brain to artificial intelligence. One of the ideas is not to decipher the natural codes of nerve cells, but to create conditions for the development of a new language for communication between the human brain and artificial intelligence tools. Theoretically, this is possible if the brain "feels" that by changing the activity of nerve cells that communicate with the computer, it is possible to "achieve" the necessary actions for the body in the external environment, for example, to take a cup of coffee or turn on your favorite music. At the same time, an artificial neural network that analyzes the flow of nerve impulses must also be directed at the brain, trying to guess the body's needs at the moment with a minimum number of movements. The most important obstacle to further progress is the problem of biocompatibility, which has not yet been resolved. This is even more important than the number of electrodes and the power of the processors on the chip. When you insert a foreign object into your brain, it tries to isolate itself from it. This is a multidisciplinary topic not only for doctors and psychophysiologists, but also for engineers, programmers, mathematicians. Of course, the problem is complex and it will be possible to overcome it only with joint efforts.

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Musa, Padde, Zita Ekeocha, Stephen Robert Byrn et Kari L. Clase. Knowledge Sharing in Organisations : Finding a Best-fit Model for a Regulatory Authority in East Africa. Purdue University, novembre 2021. http://dx.doi.org/10.5703/1288284317432.

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Knowledge is an essential organisational asset that contributes to organisational effectiveness when carefully managed. Knowledge sharing (KS) is a vital component of knowledge management that allows individuals to engage in new knowledge creation. Until it’s shared, knowledge is considered useless since it resides within the human brain. Public organisations specifically, are more involved in providing and developing knowledge and hence can be classified as knowledge-intensive organisations. Scholarly research conducted on KS has proposed a number of models to help understand the KS process between individuals but none of these models is specifically for a public organisation. Moreover, to really reap the benefits that KS brings to an organization, it’s imperative to apply a model that is attributable to the unique characteristics of that organisation. This study reviews literature from electronic databases that discuss models of KS between individuals. Factors that influence KS under each model were isolated and the extent of each of their influence on KS in a public organization context, were critically analysed. The result of this analysis gave rise to factors that were thought to be most critical in understanding KS process in a public sector setting. These factors were then used to develop a KS model by categorizing them into themes including organisational culture, motivation to share and opportunity to share. From these themes, a KS model was developed and proposed for KS in a medicines regulatory authority in East Africa. The project recommends that an empirical study be conducted to validate the applicability of the proposed KS model at a medicines regulatory authority in East Africa.

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Bacharach, Eran, W. Ian Lipkin et Avigdor Eldar. Identification of the etiological agent of tilapia disease in the Lake of Galillee. United States Department of Agriculture, janvier 2013. http://dx.doi.org/10.32747/2013.7597932.bard.

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Background to the topic. Tilapines serve as the second most important group of farmed fish worldwide. Massive mortality of wild and cultured tilapia has been observed recently in Israel but the pathogen of this disease has not been identified. We proposed to identify the agent responsible for disease.  Major conclusions, solutions, achievements. We characterized the lesions in diseased fish and found that the brain was one of the affected organs. We found conditions to isolate from brains of diseased fish the etiological agent of the tilapia disease and to propagate it in cell culture. This led to the identification of the pathogen as a novel RNA virus, which we named Tilapia Lake Virus (TiLV). Electron microscopy of TiLV revealed virion-like particles and ether/chloroform-sensitivity assays demonstrated that TiLV is enveloped. Low passage TiLV, injected intra-peritoneally to tilapia, induced a disease with over 80% mortality. Cohabitation of healthy with diseased fish demonstrated that the disease is contagious, and that mortalities occur within few days. Fish surviving initial mortality were immune to further TiLV infections, suggesting the mounting of protective immune response. Screening cDNA libraries and high throughput sequencing determined the sequence of TiLV genome. This demonstrated that TiLV is indeed a novel virus and allowed the design of a PCRbased diagnostic test.  Implications, both scientific and agricultural. The characterization of a novel, emerging RNA virus that imposes major threat to the tilapia industry, enables the specific identification of the virus in tilapines. This allows prompt screening and surveillance of TiLV, epidemiological studies, and disease containment. This also potentially opens the way for the development of vaccines against TiLV.

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Tidd, Alexander N., Richard A. Ayers, Grant P. Course et Guy R. Pasco. Scottish Inshore Fisheries Integrated Data System (SIFIDS) : work package 6 final report development of a pilot relational data resource for the collation and interpretation of inshore fisheries data. Sous la direction de Mark James et Hannah Ladd-Jones. Marine Alliance for Science and Technology for Scotland (MASTS), 2019. http://dx.doi.org/10.15664/10023.23452.

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[Extract from Executive Summary] The competition for space from competing sectors in the coastal waters of Scotland has never been greater and thus there is a growing a need for interactive seascape planning tools that encompass all marine activities. Similarly, the need to gather data to inform decision makers, especially in the fishing industry, has become essential to provide advice on the economic impact on fishing fleets both in terms of alternative conservation measures (e.g. effort limitations, temporal and spatial closures) as well as the overlap with other activities, thereby allowing stakeholders to derive a preferred option. The SIFIDS project was conceived to allow the different relevant data sources to be identified and to allow these data to be collated in one place, rather than as isolated data sets with multiple data owners. The online interactive tool developed as part of the project (Work Package 6) brought together relevant data sets and developed data storage facilities and a user interface to allow various types of user to view and interrogate the data. Some of these data sets were obtained as static layers which could sit as background data e.g. substrate type, UK fishing limits; whilst other data came directly from electronic monitoring systems developed as part of the SIFIDS project. The main non-static data source was Work Package 2, which was collecting data from a sample of volunteer inshore fishing vessels (<12m). This included data on location; time; vessel speed; count, time and position of deployment of strings of creels (or as fleets and pots as they are also known respectively); and a count of how many creels were hauled on these strings. The interactive online tool allowed all the above data to be collated in a specially designed database and displayed in near real time on the web-based application.

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Nelson, Nathan, et Charles F. Yocum. Structure, Function and Utilization of Plant Photosynthetic Reaction Centers. United States Department of Agriculture, septembre 2012. http://dx.doi.org/10.32747/2012.7699846.bard.

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Light capturing and energy conversion by PSI is one of the most fundamental processes in nature. In the heart of these adaptations stand PSI, PSII and their light harvesting antenna complexes. The main goal of this grant proposal was to obtain by X-ray crystallography information on the structure of plant photosystem I (PSI) and photosystem II (PSII) supercomplexes. We achieved several milestones along this line but as yet, like several strong laboratories around the world, we have no crystal structure of plant PSII. We have redesigned the purification and crystallization procedures and recently solved the crystal structure of the PSI supercomplex at 3.3 Å resolution. Even though this advance in resolution appears to be relatively small, we obtained a significantly improved model of the supercomplex. The work was published in J. Biol. Chem. (Amunts et al., 2010). The improved electron density map yielded identification and tracing of the PsaK subunit. The location of an additional 10 ß-carotenes, as well as 5 chlorophylls and several loop regions that were previously uninterruptable have been modeled. This represents the most complete plant PSI structure obtained thus far, revealing the locations of and interactions among 17 protein subunits and 193 non-covalently bound photochemical cofactors. We have continued extensive experimental efforts to improve the structure of plant PSI and to obtain PSII preparation amenable to crystallization. Most of our efforts were devoted to obtain well-defined subcomplexes of plant PSII preparations that are amenable to crystallization. We studied the apparent paradox of the high sensitivity of oxygen evolution of isolated thylakoids while BBY particles exhibit remarkable resilience to the same treatment. The integrity of the photosystem II (PSII) extrinsic protein complement as well as calcium effects arise from the Ca2+ atom associated with the site of photosynthetic water oxidation were investigated. This work provides deeper insights into the interaction of PsbO with PSII. Sight-directed mutagenesis indicated the location of critical sites involved in the stability of the water oxidation reaction. When combined with previous results, the data lead to a more detailed model for PsbO binding in eukaryotic PSII.

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Ohad, Itzhak, et Himadri Pakrasi. Role of Cytochrome B559 in Photoinhibition. United States Department of Agriculture, décembre 1995. http://dx.doi.org/10.32747/1995.7613031.bard.

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The aim of this research project was to obtain information on the role of the cytochrome b559 in the function of Photosystem-II (PSII) with special emphasis on the light induced photo inactivation of PSII and turnover of the photochemical reaction center II protein subunit RCII-D1. The major goals of this project were: 1) Isolation and sequencing of the Chlamydomonas chloroplast psbE and psbF genes encoding the cytochrome b559 a and b subunits respectively; 2) Generation of site directed mutants and testing the effect of such mutation on the function of PSII under various light conditions; 3) To obtain further information on the mechanism of the light induced degradation and replacement of the PSII core proteins. This information shall serve as a basis for the understanding of the role of the cytochrome b559 in the process of photoinhibition and recovery of photosynthetic activity as well as during low light induced turnover of the D1 protein. Unlike in other organisms in which the psbE and psbF genes encoding the a and b subunits of cytochrome b559, are part of an operon which also includes the psbL and psbJ genes, in Chlamydomonas these genes are transcribed from different regions of the chloroplast chromosome. The charge distribution of the derived amino-acid sequences of psbE and psbF gene products differs from that of the corresponding genes in other organisms as far as the rule of "positive charge in" is concerned relative to the process of the polypeptide insertion in the thylakoid membrane. However, the sum of the charges of both subunits corresponds to the above rule possibly indicating co-insertion of both subunits in the process of cytochrome b559 assembly. A plasmid designed for the introduction of site-specific mutations into the psbF gene of C. reinhardtii. was constructed. The vector consists of a DNA fragment from the chromosome of C. reinhardtii which spans the region of the psbF gene, upstream of which the spectinomycin-resistance-conferring aadA cassette was inserted. This vector was successfully used to transform wild type C. reinhardtii cells. The spectinomycin resistant strain thus obtained can grow autotrophically and does not show significant changes as compared to the wild-type strain in PSII activity. The following mutations have been introduced in the psbF gene: H23M; H23Y; W19L and W19. The replacement of H23 involved in the heme binding to M and Y was meant to permit heme binding but eventually alter some or all of the electron transport properties of the mutated cytochrome. Tryptophane W19, a strictly conserved residue, is proximal to the heme and may interact with the tetrapyrole ring. Therefore its replacement may effect the heme properties. A change to tyrosine may have a lesser affect on the potential or electron transfer rate while a replacement of W19 by leucine is meant to introduce a more prominent disturbance in these parameters. Two of the mutants, FW19L and FH23M have segregated already and are homoplasmic. The rest are still grown under selection conditions until complete segregation will be obtained. All mutants contain assembled and functional PSII exhibiting an increased sensitivity of PSII to the light. Work is still in progress for the detailed characterization of the mutants PSII properties. A tobacco mutant, S6, obtained by Maliga and coworkers harboring the F26S mutation in the b subunit was made available to us and was characterized. Measurements of PSII charge separation and recombination, polypeptide content and electron flow indicates that this mutation indeed results in light sensitivity. Presently further work is in progress in the detailed characterization of the properties of all the above mutants. Information was obtained demonstrating that photoinactivation of PSII in vivo initiates a series of progressive changes in the properties of RCII which result in an irreversible modification of the RCII-D1 protein leading to its degradation and replacement. The cleavage process of the modified RCII-D1 protein is regulated by the occupancy of the QB site of RCII by plastoquinone. Newly synthesized D1 protein is not accumulated in a stable form unless integrated in reassembled RCII. Thus the degradation of the irreversibly modified RCII-D1 protein is essential for the recovery process. The light induced degradation of the RCII-D1 protein is rapid in mutants lacking the pD1 processing protease such as in the LF-1 mutant of the unicellular alga Scenedesmus obliquus. In this case the Mn binding site of PSII is abolished, the water oxidation process is inhibited and harmful cation radicals are formed following light induced electron flow in PSII. In such mutants photo-inactivation of PSII is rapid, it is not protected by ligands binding at the QB site and the degradation of the inactivated RCII-D1 occurs rapidly also in the dark. Furthermore the degraded D1 protein can be replaced in the dark in absence of light driven redox controlled reactions. The replacement of the RCII-D1 protein involves the de novo synthesis of the precursor protein, pD1, and its processing at the C-terminus end by an unknown processing protease. In the frame of this work, a gene previously isolated and sequenced by Dr. Pakrasi's group has been identified as encoding the RCII-pD1 C-terminus processing protease in the cyanobacterium Synechocystis sp. PCC 6803. The deduced sequence of the ctpA protein shows significant similarity to the bovine, human and insect interphotoreceptor retinoid-binding proteins. Results obtained using C. reinhardtii cells exposes to low light or series of single turnover light flashes have been also obtained indicating that the process of RCII-D1 protein turnover under non-photoinactivating conditions (low light) may be related to charge recombination in RCII due to back electron flow from the semiquinone QB- to the oxidised S2,3 states of the Mn cluster involved in the water oxidation process.

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Epel, Bernard L., Roger N. Beachy, A. Katz, G. Kotlinzky, M. Erlanger, A. Yahalom, M. Erlanger et J. Szecsi. Isolation and Characterization of Plasmodesmata Components by Association with Tobacco Mosaic Virus Movement Proteins Fused with the Green Fluorescent Protein from Aequorea victoria. United States Department of Agriculture, septembre 1999. http://dx.doi.org/10.32747/1999.7573996.bard.

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The coordination and regulation of growth and development in multicellular organisms is dependent, in part, on the controlled short and long-distance transport of signaling molecule: In plants, symplastic communication is provided by trans-wall co-axial membranous tunnels termed plasmodesmata (Pd). Plant viruses spread cell-to-cell by altering Pd. This movement scenario necessitates a targeting mechanism that delivers the virus to a Pd and a transport mechanism to move the virion or viral nucleic acid through the Pd channel. The identity of host proteins with which MP interacts, the mechanism of the targeting of the MP to the Pd and biochemical information on how Pd are alter are questions which have been dealt with during this BARD project. The research objectives of the two labs were to continue their biochemical, cellular and molecular studies of Pd composition and function by employing infectious modified clones of TMV in which MP is fused with GFP. We examined Pd composition, and studied the intra- and intercellular targeting mechanism of MP during the infection cycle. Most of the goals we set for ourselves were met. The Israeli PI and collaborators (Oparka et al., 1999) demonstrated that Pd permeability is under developmental control, that Pd in sink tissues indiscriminately traffic proteins of sizes of up to 50 kDa and that during the sink to source transition there is a substantial decrease in Pd permeability. It was shown that companion cells in source phloem tissue export proteins which traffic in phloem and which unload in sink tissue and move cell to cell. The TAU group employing MP:GFP as a fluorescence probe for optimized the procedure for Pd isolation. At least two proteins kinases found to be associated with Pd isolated from source leaves of N. benthamiana, one being a calcium dependent protein kinase. A number of proteins were microsequenced and identified. Polyclonal antibodies were generated against proteins in a purified Pd fraction. A T-7 phage display library was created and used to "biopan" for Pd genes using these antibodies. Selected isolates are being sequenced. The TAU group also examined whether the subcellular targeting of MP:GFP was dependent on processes that occurred only in the presence of the virus or whether targeting was a property indigenous to MP. Mutant non-functional movement proteins were also employed to study partial reactions. Subcellular targeting and movement were shown to be properties indigenous to MP and that these processes do not require other viral elements. The data also suggest post-translational modification of MP is required before the MP can move cell to cell. The USA group monitored the development of the infection and local movement of TMV in N. benthamiana, using viral constructs expressing GFP either fused to the MP of TMV or expressing GFP as a free protein. The fusion protein and/or the free GFP were expressed from either the movement protein subgenomic promoter or from the subgenomic promoter of the coat protein. Observations supported the hypothesis that expression from the cp sgp is regulated differently than expression from the mp sgp (Szecsi et al., 1999). Using immunocytochemistry and electron microscopy, it was determined that paired wall-appressed bodies behind the leading edge of the fluorescent ring induced by TMV-(mp)-MP:GFP contain MP:GFP and the viral replicase. These data suggest that viral spread may be a consequence of the replication process. Observation point out that expression of proteins from the mp sgp is temporary regulated, and degradation of the proteins occurs rapidly or more slowly, depending on protein stability. It is suggested that the MP contains an external degradation signal that contributes to rapid degradation of the protein even if expressed from the constitutive cp sgp. Experiments conducted to determine whether the degradation of GFP and MP:GFP was regulated at the protein or RNA level, indicated that regulation was at the protein level. RNA accumulation in infected protoplast was not always in correlation with protein accumulation, indicating that other mechanisms together with RNA production determine the final intensity and stability of the fluorescent proteins.

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