Articles de revues : « Isolated electrons »

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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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Arif, K., M. T. Meftah, K. Chenini, S. Douis, Y. Ben Nana et H. Gossa. « Contribution of Liénard–Wiechert potential to the broadening of spectral lines by electron collisions in plasmas ». Physics of Plasmas 29, n^o 9 (septembre 2022) : 093303. http://dx.doi.org/10.1063/5.0085698.

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In this work, we have calculated the relativistic collision operator representing the line broadening, by collision with free electrons, of isolated lines emitted by hydrogen-like ions (Ly- α line [Formula: see text]) of hydrogenic ions FeXXVI, CrXXIV, and CoXXVII in the temperature range of [Formula: see text] to [Formula: see text] and electron densities of 1021 to [Formula: see text]. To accomplish this task, we have considered the fine structure of these ions and taking into account the relativistic effects related to the free electrons. Specifically, two relativistic effects are considered: the electric field of Liénard–Wiechert, created by the free electron at the emitter ion, and the modification of the hyperbolic trajectory due to the dependent mass on the free electron velocity. The average over the velocities of the free electrons is accomplished by using the Maxwell–Juttner distribution, which is more adequate for the fast (relativistic) electrons. The results are compared to the classical case (when the electric field is the Coulomb's field) to Doppler broadening and to some experimental results (K. Koyama and M. G. Haines) available in the literature. It turns out that, at high temperatures and high densities, the Stark broadening by the relativistic electrons overcomes the Doppler broadening.

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Malki, Moustafa, Antonio L. De Lacey, Nuria Rodríguez, Ricardo Amils et Victor M. Fernandez. « Preferential Use of an Anode as an Electron Acceptor by an Acidophilic Bacterium in the Presence of Oxygen ». Applied and Environmental Microbiology 74, n^o 14 (16 mai 2008) : 4472–76. http://dx.doi.org/10.1128/aem.00209-08.

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ABSTRACT Several anaerobic metal-reducing bacteria have been shown to be able to donate electrons directly to an electrode. This property is of great interest for microbial fuel cell development. To date, microbial fuel cell design requires avoiding O2 diffusion from the cathodic compartment to the sensitive anodic compartment. Here, we show that Acidiphilium sp. strain 3.2 Sup 5 cells that were isolated from an extreme acidic environment are able to colonize graphite felt electrodes. These bacterial electrodes were able to produce high-density electrocatalytic currents, up to 3 A/m2 at a poised potential of +0.15 V (compared to the value for the reference standard calomel electrode) in the absence of redox mediators, by oxidizing glucose even at saturating air concentrations and very low pHs.

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DESFRANÇOIS, CHARLES, HASSAN ABDOUL-CARIME et JEAN-PIERRE SCHERMANN. « GROUND-STATE DIPOLE-BOUND ANIONS ». International Journal of Modern Physics B 10, n^o 12 (30 mai 1996) : 1339–95. http://dx.doi.org/10.1142/s0217979296000520.

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Ground-state dipole-bound anions are fragile molecular species which excess electrons are almost entirely located in a very diffuse orbital outside the molecular frame. They can be created by attachment of very low energy electrons to polar molecules or small clusters which dipole moments are larger than a practical critical value of 2.5 D. They present analogies with Rydberg atoms and their geometrical structures are nearly identical to those of their neutral parents. Experimentally, dipole-binding of electrons to polar systems is a non-perturbative and reversible ionization process, in contrast with conventional valence-binding. Examples of applications such as mass-spectrometric isomer selection of clusters or determination of electron attachment properties of isolated nucleic acid bases are given.

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MAMUN, A. A. « A new electrostatic mode in a dusty plasma due to dust charge fluctuation ». Journal of Plasma Physics 75, n^o 3 (juin 2009) : 389–93. http://dx.doi.org/10.1017/s0022377808007629.

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AbstractA dusty plasma consisting of cold and hot electrons, cold ions, and charge fluctuating isolated cold dust has been considered. It has been shown by a normal mode analysis that in such a dusty plasma there exists a new type of electrostatic perturbation mode due to the charge fluctuation of the isolated dust. The basic features of this new electrostatic perturbation mode, which are different from those of the electron-acoustic waves, have also been analytically identified. The implications of these results in both the space and laboratory dusty plasma conditions are briefly discussed.

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Fedorovich, Viatcheslav, Matthew C. Knighton, Eulyn Pagaling, F. Bruce Ward, Andrew Free et Igor Goryanin. « Novel Electrochemically Active Bacterium Phylogenetically Related to Arcobacter butzleri, Isolated from a Microbial Fuel Cell ». Applied and Environmental Microbiology 75, n^o 23 (2 octobre 2009) : 7326–34. http://dx.doi.org/10.1128/aem.01345-09.

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ABSTRACT Exoelectrogenic bacteria are organisms that can transfer electrons to extracellular insoluble electron acceptors and have the potential to be used in devices such as microbial fuel cells (MFCs). Currently, exoelectrogens have been identified in the Alpha-, Beta-, Gamma- and Deltaproteobacteria, as well as in the Firmicutes and Acidobacteria. Here, we describe use of culture-independent methods to identify two members of the genus Arcobacter in the Epsilon p roteobacteria that are selectively enriched in an acetate-fed MFC. One of these organisms, Arcobacter butzleri strain ED-1, associates with the electrode and rapidly generates a strong electronegative potential as a pure culture when it is supplied with acetate. A mixed-community MFC in which ∼90% of the population is comprised of the two Arcobacter species generates a maximal power density of 296 mW/liter. This demonstration of exoelectrogenesis by strain ED-1 is the first time that this property has been shown for members of this genus.

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Agostino, L., G. Daskalakis, P. Govoni, L. Malgeri et M. Paganoni. « Inter-calibration of the CMS electromagnetic calorimeter with isolated electrons ». Journal of Physics G : Nuclear and Particle Physics 34, n^o 3 (18 janvier 2007) : N67—N83. http://dx.doi.org/10.1088/0954-3899/34/3/n02.

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Datsyuk, Vitaly V., et Iryna V. Ivanytska. « Statistical Properties of Conduction Electrons in an Isolated Metal Nanosphere ». Journal of Statistical Physics 152, n^o 5 (17 juillet 2013) : 969–78. http://dx.doi.org/10.1007/s10955-013-0798-5.

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De Wever, Helene, James R. Cole, Michael R. Fettig, Deborah A. Hogan et James M. Tiedje. « Reductive Dehalogenation of Trichloroacetic Acid byTrichlorobacter thiogenes gen. nov., sp. nov ». Applied and Environmental Microbiology 66, n^o 6 (1 juin 2000) : 2297–301. http://dx.doi.org/10.1128/aem.66.6.2297-2301.2000.

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ABSTRACT A bacterium able to grow via reductive dechlorination of trichloroacetate was isolated from anaerobic soil enrichments. The isolate, designated strain K1, is a member of the δ proteobacteria and is related to other known sulfur and ferric iron reducers. In anaerobic mineral media supplemented with acetate and trichloroacetate, its doubling time was 6 h. Alternative electron donor and acceptors were acetoin and sulfur or fumarate, respectively. Trichloroacetate dehalogenation activity was constitutively present, and the dechlorination product was dichloroacetate and chloride. Trichloroacetate conversion seemed to be coupled to a novel sulfur-sulfide redox cycle, which shuttled electrons from acetate oxidation to trichloroacetate reduction. In view of its unique physiological characteristics, the name Trichlorobacter thiogenes is suggested for strain K1.

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Ishii, Shuya, Seiichi Saiki, Shinobu Onoda, Yuta Masuyama, Hiroshi Abe et Takeshi Ohshima. « Ensemble Negatively-Charged Nitrogen-Vacancy Centers in Type-Ib Diamond Created by High Fluence Electron Beam Irradiation ». Quantum Beam Science 6, n^o 1 (30 décembre 2021) : 2. http://dx.doi.org/10.3390/qubs6010002.

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Electron beam irradiation into type-Ib diamond is known as a good method for the creation of high concentration negatively-charged nitrogen-vacancy (NV−) centers by which highly sensitive quantum sensors can be fabricated. In order to understand the creation mechanism of NV− centers, we study the behavior of substitutional isolated nitrogen (P1 centers) and NV− centers in type-Ib diamond, with an initial P1 concentration of 40–80 ppm by electron beam irradiation up to 8.0 × 1018 electrons/cm2. P1 concentration and NV− concentration were measured using electron spin resonance and photoluminescence measurements. P1 center count decreases with increasing irradiation fluence up to 8.0 × 1018 electrons/cm2. The rate of decrease in P1 is slightly lower at irradiation fluence above 4.0 × 1018 electrons/cm2 especially for samples of low initial P1 concentration. Comparing concentration of P1 centers with that of NV− centers, it suggests that a part of P1 centers plays a role in the formation of other defects. The usefulness of electron beam irradiation to type-Ib diamonds was confirmed by the resultant conversion efficiency from P1 to NV− center around 12–19%.

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Zeng, Jiaolong, Chen Ye, Pengfei Liu, Cheng Gao, Yongjun Li et Jianmin Yuan. « The Strong Enhancement of Electron-Impact Ionization Processes in Dense Plasma by Transient Spatial Localization ». International Journal of Molecular Sciences 23, n^o 11 (27 mai 2022) : 6033. http://dx.doi.org/10.3390/ijms23116033.

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Recent experiments have observed much higher electron–ion collisional ionization cross sections and rates in dense plasmas than predicted by the current standard atomic collision theory, including the plasma screening effect. We suggest that the use of (distorted) plane waves for incident and scattered electrons is not adequate to describe the dissipation that occurs during the ionization event. Random collisions with free electrons and ions in plasma cause electron matter waves to lose their phase, which results in the partial decoherence of incident and scattered electrons. Such a plasma-induced transient spatial localization of the continuum electron states significantly modifies the wave functions of continuum electrons, resulting in a strong enhancement of the electron–ion collisional ionization of ions in plasma compared to isolated ions. Here, we develop a theoretical formulation to calculate the differential and integral cross sections by incorporating the effects of plasma screening and transient spatial localization. The approach is then used to investigate the electron-impact ionization of ions in solid-density magnesium plasma, yielding results that are consistent with experiments. In dense plasma, the correlation of continuum electron energies is modified, and the integral cross sections and rates increase considerably. For the ionization of Mg9+e+1s22s2S→1s21S+2e, the ionization cross sections increase several-fold, and the rates increase by one order of magnitude. Our findings provide new insight into collisional ionization and three-body recombination and may aid investigations of the transport properties and nonequilibrium evolution of dense plasma.

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Tsuna, Daichi, et Norita Kawanaka. « Radio emission from accreting isolated black holes in our galaxy ». Monthly Notices of the Royal Astronomical Society 488, n^o 2 (4 juillet 2019) : 2099–107. http://dx.doi.org/10.1093/mnras/stz1809.

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ABSTRACT Apart from the few tens of stellar-mass black holes discovered in binary systems, an order of 108 isolated black holes (IBHs) are believed to be lurking in our Galaxy. Although some IBHs are able to accrete matter from the interstellar medium, the accretion flow is usually weak and thus radiatively inefficient, which results in significant material outflow. We study electron acceleration generated by the shock formed between this outflow and the surrounding material, and the subsequent radio synchrotron emission from accelerated electrons. By numerically calculating orbits of IBHs to obtain their spatial and velocity distributions, we estimate the number of IBHs detectable by surveys using SKA1-mid (SKA2) as ∼30 (∼700) for the most optimistic case. The SKA’s parallax measurements may accurately give their distances, possibly shedding light on the properties of the black holes in our Galaxy.

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Kato, Souichiro, Isao Yumoto et Yoichi Kamagata. « Isolation of Acetogenic Bacteria That Induce Biocorrosion by Utilizing Metallic Iron as the Sole Electron Donor ». Applied and Environmental Microbiology 81, n^o 1 (10 octobre 2014) : 67–73. http://dx.doi.org/10.1128/aem.02767-14.

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ABSTRACTCorrosion of iron occurring under anoxic conditions, which is termed microbiologically influenced corrosion (MIC) or biocorrosion, is mostly caused by microbial activities. Microbial activity that enhances corrosion via uptake of electrons from metallic iron [Fe(0)] has been regarded as one of the major causative factors. In addition to sulfate-reducing bacteria and methanogenic archaea in marine environments, acetogenic bacteria in freshwater environments have recently been suggested to cause MIC under anoxic conditions. However, no microorganisms that perform acetogenesis-dependent MIC have been isolated or had their MIC-inducing mechanisms characterized. Here, we enriched and isolated acetogenic bacteria that induce iron corrosion by utilizing Fe(0) as the sole electron donor under freshwater, sulfate-free, and anoxic conditions. The enriched communities produced significantly larger amounts of Fe(II) than the abiotic controls and produced acetate coupled with Fe(0) oxidation prior to CH4production. Microbial community analysis revealed thatSporomusasp. andDesulfovibriosp. dominated in the enrichments. Strain GT1, which is closely related to the acetogenSporomusa sphaeroides, was eventually isolated from the enrichment. Strain GT1 grew acetogenetically with Fe(0) as the sole electron donor and enhanced iron corrosion, which is the first demonstration of MIC mediated by a pure culture of an acetogen. Other well-known acetogenic bacteria, includingSporomusa ovataandAcetobacteriumspp., did not grow well on Fe(0). These results indicate that very few species of acetogens have specific mechanisms to efficiently utilize cathodic electrons derived from Fe(0) oxidation and induce iron corrosion.

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Lubchich, A. A., A. G. Yahnin, E. E. Titova, A. G. Demekhov, V. Yu Trakhtengerts, J. Manninen et T. Turunen. « Longitudinal drift of substorm electrons as the reason of impulsive precipitation events and VLF emissions ». Annales Geophysicae 24, n^o 10 (20 octobre 2006) : 2667–84. http://dx.doi.org/10.5194/angeo-24-2667-2006.

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Abstract. Using the data from satellite CRRES and three geostationary LANL spacecraft, the propagation of an electron cloud from midnight to the evening sector is investigated. An electron cloud was injected during a weak isolated substorm that developed on a quiet geomagnetic background. It is found that within the local time sector from 03:00 until at least 08:00 MLT, the propagation of electrons at perpendicular pitch-angles is well described by a simple model of drift in the dipole magnetic field. The flux levels in the field-aligned electrons increase simultaneously with the flux at perpendicular pitch angles, which is attributed to the pitch angle diffusion by the whistler mode. This pitch-angle diffusion leads to precipitation of electrons from a drifting cloud and an increase in the ionospheric electron density, simultaneously observed above Tromsø, Norway, by the EISCAT UHF radar in the morning sector (04:40–05:25 MLT). The precipitation develops as quasi-periodic pulses with a period of about 100 s. We discuss the models of pulsating precipitation due to the whistler cyclotron instability and show that our observations can be explained by such a model.

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Colavecchia, F. D., G. Gasaneo et D. Mitnik. « Double Photoionization of Endohedrally Confined Atoms ». Journal of Atomic, Molecular, and Optical Physics 2011 (27 décembre 2011) : 1–6. http://dx.doi.org/10.1155/2011/817034.

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We study the double electronic emission by photon impact from ground state of two-electron atoms in the center of a model spherical fullerene, which is described by a square-well shell. Cross-sections for different well depth are computed within a separable model for the final state, and a configuration interaction state for the initial one. Triple differential cross-sections show a strong dependence on the well depth and on the energy of the emitted electrons, due to the delocalization of the electrons in the initial state. The fullerene potential also allows higher angular momenta partial waves to be included in the process, which modifies the well-known two-lobe cross-section from isolated atom.

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Arora, Jaspreet, et P. V. Sane. « Histidyl Residues Mediate Electron Transport in Plant Mitochondria ». Zeitschrift für Naturforschung C 44, n^o 5-6 (1 juin 1989) : 537–42. http://dx.doi.org/10.1515/znc-1989-5-630.

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Abstract Plant The effect of chemical modification of histidyl residues using diethyl pyrocarbonate (DEP) on plant mitochondrial electron transport was studied. Mitochondrial membranes from potato tubers were isolated and electron flow from NADH to oxygen, NADH to ferricyanide and ascorbate to oxygen were monitored in pro», nee and/or absence of DEP. Measurements were made at various concentrations of DEP and at different pHs either by using an oxygen electrode or spectro-photometrically. The results show that DEP inhibits flow of electrons from NADH to oxygen, however partial electron transport from NADH to ferricyanide and ascorbate to oxygen was unaffected. Maximum inhibition was observed at pH 6.5. The time course of the DEP action revealed a biphasic nature of inhibition. Effects on the levels of reduction of cytochromes b and c by DEP during electron transport indicated that histidyl residues may be present before or at cytochrome b , which are being modified.

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Song, Myeonghun, Minki Jeong, Byeongki Kang, Soonchil Lee, Tomohiro Ueno, Akira Matsubara, Takao Mizusaki, Yutaka Fujii, Seitaro Mitsudo et Meiro Chiba. « Spin dynamics of isolated donor electrons in phosphorus-doped silicon from high-frequency electron spin resonance ». Journal of Physics : Condensed Matter 22, n^o 20 (26 avril 2010) : 206001. http://dx.doi.org/10.1088/0953-8984/22/20/206001.

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Kimura, Shigeo S., Kazumi Kashiyama et Kenta Hotokezaka. « Multiwavelength Emission from Magnetically Arrested Disks around Isolated Black Holes ». Astrophysical Journal Letters 922, n^o 1 (1 novembre 2021) : L15. http://dx.doi.org/10.3847/2041-8213/ac35dc.

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Abstract We discuss the prospects for identifying the nearest isolated black holes (IBHs) in our Galaxy. IBHs accreting gas from the interstellar medium likely form magnetically arrested disks (MADs). We show that thermal electrons in the MADs emit optical signals through the thermal synchrotron process while nonthermal electrons accelerated via magnetic reconnections emit a flat-spectrum synchrotron radiation in the X-ray to MeV gamma-ray ranges. The Gaia catalog will include at most a thousand IBHs within ≲1 kpc that are distributed on and around the cooling sequence of white dwarfs (WDs) in the Hertzsprung–Russell diagram. These IBH candidates should also be detected by eROSITA, with which they can be distinguished from isolated WDs and neutron stars. Follow-up observations with hard X-ray and MeV gamma-ray satellites will be useful to unambiguously identify IBHs.

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Walker, S. N., M. A. Balikhin, H. St C. K. Alleyne, Y. Hobara, M. André et M. W. Dunlop. « Lower hybrid waves at the shock front : a reassessment ». Annales Geophysicae 26, n^o 3 (26 mars 2008) : 699–707. http://dx.doi.org/10.5194/angeo-26-699-2008.

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Abstract. The primary process occurring at a collisionless shock is the redistribution of the bulk upstream energy into other degrees of freedom. One part of this process results in the acceleration of electrons at the shock front. Accelerated electrons are observed at the terrestrial and other planetary shocks, comets, and their effects are observed in astrophysical phenomena such as supernova remnants and jets in the form of X-ray bremsstrahlung radiation. One of the physical models for electron acceleration at supercritical shocks is based on low-hybrid turbulence due to the presence of reflected ions in the foot region. Since lower hybrid waves propagate almost perpendicular to the magnetic field they can be simultaneously in resonance with both the unmagnetised ions (ω=Vik⊥) and magnetised electrons (ω=Vek||). In this paper, Cluster observations of the electric field are used to study the occurrence of lower hybrid waves in the front of the terrestrial bow shock. It is shown that the lower hybrid waves exist as isolated wave packets. However, the very low level of the observed lower hybrid turbulence is too small to impart significant energisation to the electron population.

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Suzuki, Chihiro, Fumihiro Koike, Izumi Murakami, Tetsutarou Oishi et Naoki Tamura. « Spectra of Ga-Like to Cu-Like Praseodymium and Neodymium Ions Observed in the Large Helical Device ». Atoms 9, n^o 3 (14 juillet 2021) : 46. http://dx.doi.org/10.3390/atoms9030046.

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Extreme ultraviolet (EUV) spectra of highly charged praseodymium (Pr) and neodymium (Nd) ions have been investigated in optically thin high-temperature plasmas produced in the Large Helical Device (LHD), a magnetically confined torus device for fusion research. Discrete spectral lines emitted mainly from highly charged ions having 4s or 4p outermost electrons were observed in plasmas with electron temperatures of 0.8–1.8 keV. Most of the isolated lines of Ga-like to Cu-like Nd ions were identified by a comparison with the recent data recorded in an electron beam ion trap (EBIT). The isolated lines of Pr ions corresponding to the identified lines of Nd ions were easily assigned from a similarity of the spectral feature for these two elements. As a result, some of the lines of Pr ions have been newly identified experimentally for the first time in this study.

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Babenkov, Sergey, Marie Froidevaux, Peng Ye, Ludovic Tortech, Yannick Dappe, Willem Boutu, Nickolas Barrett et Hamed Merdji. « Towards complete band structure of microscopic MoS₂ flakes ». EPJ Web of Conferences 273 (2022) : 01006. http://dx.doi.org/10.1051/epjconf/202227301006.

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The occupied and unoccupied electronic states of MoS2 monolayer isolated flake were studied using laboratory based photoemission electron microscope (PEEM) nanoESCA equipped with He-I photon source. PEEM real-space imaging allowed selecting the high quality flake. Altogether, the data will allow accurately recovering the band structures of MoS2. The band structures will be used in future pump-probe experiments to explore the dynamics of electrons in the conduction band and photo-induced multitopological states using trefoil polarization.

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Uchiyama, Taku, Kimio Ito, Koji Mori, Hirohito Tsurumaru et Shigeaki Harayama. « Iron-Corroding Methanogen Isolated from a Crude-Oil Storage Tank ». Applied and Environmental Microbiology 76, n^o 6 (29 janvier 2010) : 1783–88. http://dx.doi.org/10.1128/aem.00668-09.

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ABSTRACT Microbiologically influenced corrosion of steel in anaerobic environments has been attributed to hydrogenotrophic microorganisms. A sludge sample collected from the bottom plate of a crude-oil storage tank was used to inoculate a medium containing iron (Fe0) granules, which was then incubated anaerobically at 37°C under an N2-CO2 atmosphere to enrich for microorganisms capable of using iron as the sole source of electrons. A methanogen, designated strain KA1, was isolated from the enrichment culture. An analysis of its 16S rRNA gene sequence revealed that strain KA1 is a Methanococcus maripaludis strain. Strain KA1 produced methane and oxidized iron much faster than did the type strain of M. maripaludis, strain JJT, which produced methane at a rate expected from the abiotic H2 production rate from iron. Scanning electron micrographs of iron coupons that had been immersed in either a KA1 culture, a JJT culture, or an aseptic medium showed that only coupons from the KA1 culture had corroded substantially, and these were covered with crystalline deposits that consisted mainly of FeCO3.

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Grotjohann, Norbert, David Messdaghi et Wolfgang Kowallik. « Oxygen Uptake during Photosynthesis of Isolated Pea Chloroplasts ». Zeitschrift für Naturforschung C 54, n^o 3-4 (1 avril 1999) : 209–19. http://dx.doi.org/10.1515/znc-1999-3-411.

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Abstract Mass spectrometric analysis of the gas exchange of illuminated leaflets of 10-14 d old pea seedlings revealed not only 16O2-liberation from photosynthetic H216O-splitting, but also uptake of 18O2, applied to the gas phase of the reaction vessel. Isolated intact chloroplasts of such leaflets suspended in a medium containing NaHCO3 and glycerate 3-phosphate, on irradiation with blue (λ 448 nm) or red (λ 679 nm) light also produced 16O2 from water oxidation and consumed 18O2 from the gas phase. The two reactions were saturated at the same quantum fluence rates. Uptake of 18oxygen was not affected by inhibitors of mitochondrial respiration (alternative pathway included), such as rotenone (5 x l0-5 ᴍ), antimycin A (5 x l0-6 ᴍ), KCN (10-3 ᴍ), SHAM (10-3 ᴍ), or propylgallate (10-3 ᴍ). It was, however, absent, when photosynthetic 16oxygen evolution was completely inhibited by DCMU (10-5 ᴍ). DBMIB (10-5 ᴍ), assumed to prevent electron flow from plastoquinone pool to the cytochrome b6/f-complex, suppressed photosynthetic oxygen evolution, but did not impair uptake of 18O2. A similar result was obtained at application of 4 x l0-5 ᴍ antimycin A. The data are interpreted to show a drain off to molecular oxygen of light-excited electrons from the photosynthetic electron transport chain at the site of plastoquinone pool during photosynthesis. This corresponds to chlororespiration, originally described for Chlamydomonas in darkness by Bennoun (1982). It is discussed, whether O2-uptake during photosynthesis is an additional means for providing ATP for photosynthetic CO2-reduction by increasing the proton gradient across the thylakoid membrane.

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Brown, G. C., et M. D. Brand. « Proton/electron stoichiometry of mitochondrial complex I estimated from the equilibrium thermodynamic force ratio ». Biochemical Journal 252, n^o 2 (1 juin 1988) : 473–79. http://dx.doi.org/10.1042/bj2520473.

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The thermodynamic forces on electrons (delta Eh) and protons (delta p) across mitochondrial complexes I, III and IV were measured in isolated mitochondria respiring on succinate. The force ratio (delta Eh/delta p) across complex I close to equilibrium was found to be about 2. The equilibrium force ratio across complex I was measured during sulphite oxidation and was again close to 2. These results indicate that the proton/electron stoichiometry of complex I is 2, in conditions of high protonmotive force.

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Rossie, B. B., T. L. Shofner, S. R. Brown, D. M. Shuttleworth et D. Nguyen. « Chain Structure Defect Location by Focused Ion Beam Passive Voltage Contrast ». Microscopy and Microanalysis 6, S2 (août 2000) : 520–21. http://dx.doi.org/10.1017/s1431927600035091.

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Defects present in microelectronic devices are often present in test structures as well. This makes test structures useful in identifying defect mechanisms. Chain patterns consists of thousands of contacts and plugs in series. The presence of an open contact in a chain can be detected by a loss of electrical continuity. The specific site of an open contact is difficult to locate for further analysis.The application of the focused ion beam (FIB) for passive voltage contrast (PVC) provides an effective method for contact defect location. Once the defect is located the FIB facilitates efficient site-specific specimen preparation for scanning electron microscopy (SEM), transmission electron microscopy (TEM) or Auger analysis.The FIB is capable of PVC analysis by distinguishing electrically isolated conductors from grounded conductors. Isolated conductors charge as a result of ion beam interaction. Once charged, the quantity of secondary electrons available for detection is greatly reduced.

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Xiao, Yaozong, Chao Feng et Bo Liu. « Generating Isolated Attosecond X-Ray Pulses by Wavefront Control in a Seeded Free-Electron Laser ». Ultrafast Science 2022 (30 juillet 2022) : 1–8. http://dx.doi.org/10.34133/2022/9812478.

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We proposed a simple method based on the seeded free-electron laser (FEL) to generate fully coherent X-ray pulses with durations at dozens of attosecond level. The echo-enabled harmonic generation technique is utilized to generate the fully coherent laser pulse covering the water-window range. A wavefront rotation laser is adopted as the seed to tailor the longitudinal contour of the radiation pulse. Due to the sensitivity of seeded FEL to external lasers, this method can effectively inhibit the bunching of the adjacent regions while preserving an isolated bunching in the middle. Sending such an electron beam into a short undulator, simulation results show that ultrashort X-ray pulses with peak power of GW level and pulse duration as short as 86 attoseconds can be generated. The proposed scheme can make it possible to study the electronic dynamic of the valence electrons of which the time scale is about 100 attoseconds and may open up a new frontier of ultrafast science.

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Dimitrijev, Sima. « Irreversible event-based model for thermal emission of electrons from isolated traps ». Journal of Applied Physics 105, n^o 10 (15 mai 2009) : 103706. http://dx.doi.org/10.1063/1.3132094.

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Andreev, V., B. Andrieu, T. Anthonis, A. Astvatsatourov, A. Babaev, J. Bähr, P. Baranov et al. « Isolated electrons and muons in events with missing transverse momentum at HERA ». Physics Letters B 561, n^o 3-4 (mai 2003) : 241–57. http://dx.doi.org/10.1016/s0370-2693(03)00497-0.

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Kobayashi, Yuzu, Misun Hong, Raymond Wong, Yasuyuki Yokota, Jun Takeya et Yousoo Kim. « Redox Reactions of Isolated Ferrocene Derivatives Observed By Electrochemical Scanning Tunneling Microscope ». ECS Meeting Abstracts MA2022-01, n^o 50 (7 juillet 2022) : 2109. http://dx.doi.org/10.1149/ma2022-01502109mtgabs.

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Redox reactions on electrode surfaces have been widely applied to fundamental technologies such as energy conversion and storage, metal refining, and electronics. Recently, it has become clear that local structures at the single-atom and single-molecule level affect the efficiency and selectivity of redox reactions [1]. EC-STM, a combination of scanning tunneling microscopy (STM) and electrochemical (EC) measurements, allows direct observation of electrochemical interfaces with high spatial resolution [2], and we aimed to observe the redox reactions of single molecules using this technique. As a target molecule, ferrocene (Fc) was coupled to a tripodal base molecule [3], which was known to form an ordered self-assembled monolayer (SAM) on a gold electrode. By preparing mixed SAM with the molecules with and without Fc moieties, we could stably deposit Fc species on the Au (111) electrode in an isolated and dispersed state, which enables us to observe clear changes in the EC-STM images upon the redox reaction of the single Fc derivative. A mixture of 8,13-trimercaptotriptycene (Trip) and its Fc derivative (Fc-Trip) was deposited on an Au(111) electrode (the molecules were provided by the Fukushima Lab., Chemical Biology Laboratory, Tokyo Institute of Technology, and the Suzuki Lab., Graduate School of Science, Hokkaido University). Cyclic voltammetry (CV) was performed with a potentiostat (HZ-7000, Hokuto Denko) at a sweep rate of 100 mV/s in 0.1 M HClO4 solution. STM measurements were performed using an MS-10 STM (Bruker), controlled by a NanoScope V (Bruker). A Pt/Ir wire coated with Apiezon wax was used as a probe in the home-made electrochemical cell. The sample potential (Esample) was varied from 0.2 V (vs Ag/AgCl) to 0.4 V while the potential difference between the tip and the sample was kept at 0.3 V. The CV results are shown in Fig. 1 (a), where the peak originating from the redox reactions of Fc-Trip is observed (dotted line is only for Trip), indicating that the redox potential of Fc-Trip is ~0.3 V. Since the full width at half maximum of the peak is about 0.1 V, Fc-Trip do not interact with each other and are considered to be isolated and dispersed on the Au(111) electrode [4]. Corresponding EC-STM images are shown in Fig. 1 (c)-(e). While the bright spots derived from Fc-Trip are observed at Esample = 0.2 V (the tip potential Etip is 0.5 V), as indicated by white circles, the bright spots almost disappeared at Esample = 0.4 V (Etip = 0.7 V). We confirmed that the change of the height is reversible with respect to the applied potentials, as shown in Fig. 1(c) and 1(e). The height of the bright spot in the EC-STM image reflects the electron transfer rate through the redox molecule between the tip and the sample. When the sample potential is set to 0.2 V, Fc-Trip is formally in the reduced state, but the electrons are readily transferred to the tip regulated at 0.5 V. On the other hand, when the sample potential is set to settle the oxidized state (0.4 V), the molecule cannot pass electrons to the high potential tip. Therefore, in the case of Fig. 1(d), the current between the tip and the sample is not increased with the presence of the Fc moiety, leading to the apparent disappearance of spots. We noticed that some bright spots did not disappear at Esample = 0.4 V (an arrow in Fig. 1(d)), which suggests that there is heterogeneity in the redox reactivity. In the future, we plan to investigate the heterogeneity by combining spectroscopic techniques with the EC-STM measurement. [1] J. H. K. Pfisterer et al., Nature , 74, 549 (2017) [2] Y. Yokota et al., J. Phys. Chem. C, 111, 7561 (2007) [3] F. Ishiwari et al., J. Am. Chem. Soc., 141, 5995 (2019) [4] C. E. D. Chidsey et al., J. Am. Chem. Soc., 112, 4301 (1990) Figure 1

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TEUFEL, STEFAN, et HERBERT SPOHN. « SEMICLASSICAL MOTION OF DRESSED ELECTRONS ». Reviews in Mathematical Physics 14, n^o 01 (janvier 2002) : 1–28. http://dx.doi.org/10.1142/s0129055x02001077.

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We consider an electron coupled to the quantized radiation field and subject to a slowly varying electrostatic potential. We establish that over sufficiently long times radiation effects are negligible and the dressed electron is governed by an effective one-particle Hamiltonian. In the proof only a few generic properties of the full Pauli–Fierz Hamiltonian H PF enter. Most importantly, H PF must have an isolated ground state band for |p|<p c ≤∞ with p the total momentum and p c indicating that the ground state band may terminate. This structure demands a local approximation theorem, in the sense that the one-particle approximation holds until the semiclassical dynamics violates |p|<p c . Within this framework we prove an abstract Hilbert space theorem which uses no additional information on the Hamiltonian away from the band of interest. Our result is applicable to other time-dependent semiclassical problems. We discuss semiclassical distributions for the effective one-particle dynamics and show how they can be translated to the full dynamics by our results.

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Wang, Weizhou, et Pavel Hobza. « Application of Berlin's Theorem to Bond-Length Changes in Isolated Molecules and Red- and Blue-Shifting H-Bonded Clusters ». Collection of Czechoslovak Chemical Communications 73, n^o 6-7 (2008) : 862–72. http://dx.doi.org/10.1135/cccc20080862.

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The origin of the bond-length change in molecule or molecular cluster has been investigated at the MP2/aug-cc-pVDZ level of theory using the electrostatic potential or the electron density difference analysis method. Our results have clearly shown that the bond-length change of a chemical bond is determined mainly by the balance of the electrostatic forces exerted by electrons on the two nuclei. The factors that affect the balance of the electrostatic forces include four parts: (i) The abstraction of the electron density from Berlin's binding region between the two nuclei. (ii) The accumulation of the electron density in Berlin's antibinding regions. (iii) The accumulation of the electron density in Berlin's binding region between the two nuclei. (iv) The abstraction of the electron density from Berlin's antibinding regions. Using the change of the electron density around the two nuclei of a chemical bond, we have succeeded in explaining two important chemical phenomena: (i) breakdown of bond length-bond strength correlation; (ii) the bond-length change in the hydrogen bond.

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Lever, Fabiano, Dennis Mayer, Jan Metje, Skirmantas Alisauskas, Francesca Calegari, Stefan Düsterer, Raimund Feifel et al. « Core-Level Spectroscopy of 2-Thiouracil at the Sulfur L1- and L2,3-Edges Utilizing a SASE Free-Electron Laser ». Molecules 26, n^o 21 (26 octobre 2021) : 6469. http://dx.doi.org/10.3390/molecules26216469.

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In this paper, we report X-ray absorption and core-level electron spectra of the nucleobase derivative 2-thiouracil at the sulfur L1- and L2,3-edges. We used soft X-rays from the free-electron laser FLASH2 for the excitation of isolated molecules and dispersed the outgoing electrons with a magnetic bottle spectrometer. We identified photoelectrons from the 2p core orbital, accompanied by an electron correlation satellite, as well as resonant and non-resonant Coster–Kronig and Auger–Meitner emission at the L1- and L2,3-edges, respectively. We used the electron yield to construct X-ray absorption spectra at the two edges. The experimental data obtained are put in the context of the literature currently available on sulfur core-level and 2-thiouracil spectroscopy.

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Lochmann, Christine, Thomas F. M. Luxford, Samanta Makurat, Andriy Pysanenko, Jaroslav Kočišek, Janusz Rak et Stephan Denifl. « Low-Energy Electron Induced Reactions in Metronidazole at Different Solvation Conditions ». Pharmaceuticals 15, n^o 6 (2 juin 2022) : 701. http://dx.doi.org/10.3390/ph15060701.

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Metronidazole belongs to the class of nitroimidazole molecules and has been considered as a potential radiosensitizer for radiation therapy. During the irradiation of biological tissue, secondary electrons are released that may interact with molecules of the surrounding environment. Here, we present a study of electron attachment to metronidazole that aims to investigate possible reactions in the molecule upon anion formation. Another purpose is to elucidate the effect of microhydration on electron-induced reactions in metronidazole. We use two crossed electron/molecular beam devices with the mass-spectrometric analysis of formed anions. The experiments are supported by quantum chemical calculations on thermodynamic properties such as electron affinities and thresholds of anion formation. For the single molecule, as well as the microhydrated condition, we observe the parent radical anion as the most abundant product anion upon electron attachment. A variety of fragment anions are observed for the isolated molecule, with NO2− as the most abundant fragment species. NO2− and all other fragment anions except weakly abundant OH− are quenched upon microhydration. The relative abundances suggest the parent radical anion of metronidazole as a biologically relevant species after the physicochemical stage of radiation damage. We also conclude from the present results that metronidazole is highly susceptible to low-energy electrons.

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Davidson, John F., et Robert H. Schiestl. « Mitochondrial Respiratory Electron Carriers Are Involved in Oxidative Stress during Heat Stress inSaccharomyces cerevisiae ». Molecular and Cellular Biology 21, n^o 24 (15 décembre 2001) : 8483–89. http://dx.doi.org/10.1128/mcb.21.24.8483-8489.2001.

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ABSTRACT In the present study we sought to determine the source of heat-induced oxidative stress. We investigated the involvement of mitochondrial respiratory electron transport in post-diauxic-phase cells under conditions of lethal heat shock. Petite cells were thermosensitive, had increased nuclear mutation frequencies, and experienced elevated levels of oxidation of an intracellular probe following exposure to a temperature of 50°C. Cells with a deletion in COQ7 leading to a deficiency in coenzyme Q had a much more severe thermosensitivity phenotype for these oxidative endpoints following heat stress compared to that of petite cells. In contrast, deletion of the external NADH dehydrogenases NDE1 and NDE2, which feed electrons from NADH into the electron transport chain, abrogated the levels of heat-induced intracellular fluorescence and nuclear mutation frequency. Mitochondria isolated fromCOQ7-deficient cells secreted more than 30 times as much H2O2 at 42 as at 30°C, while mitochondria isolated from cells simultaneously deficient in NDE1 and NDE2 secreted no H2O2. We conclude that heat stress causes nuclear mutations via oxidative stress originating from the respiratory electron transport chains of mitochondria.

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Simon, M. N., B. Y. Lin et J. S. Wall. « Structural Analysis of Filaments Using the STEM ». Microscopy and Microanalysis 6, S2 (août 2000) : 862–63. http://dx.doi.org/10.1017/s1431927600036801.

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The Scanning Transmission Electron Microscope (STEM) facility at BNL is an NIH Biotechnology Research Resource and as such is available to users with suitable projects, free of charge. Currently, many of our users' projects involve studying the structures of a variety of filaments. Most of these are of biological origin, although a couple involve conducting polymers. The STEM has a long history of being used to study different types of filaments and resolving controversies about their structure.The mainstay of the STEM is mass analysis on unstained, isolated, freeze-dried samples. On these, the STEM can collect in-focus digital data directly. In a scan (8 sec. in real time) of a sample, at each of 512x512 picture elements (pixels), the number of electrons scattered into two annular detectors is recorded. For each pixel, the number of scattered electrons is directly proportional to the mass thickness in that pixel.

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Milosavljević, A. R., P. Rousseau, A. Domaracka, B. A. Huber et A. Giuliani. « Multiple electron capture from isolated protein poly-anions in collision with slow highly charged ions ». Physical Chemistry Chemical Physics 19, n^o 30 (2017) : 19691–98. http://dx.doi.org/10.1039/c7cp02075a.

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Neal, Sonya E., Deepa V. Dabir, Heather L. Tienson, Darryl M. Horn, Kathrin Glaeser, Rachel R. Ogozalek Loo, Antoni Barrientos et Carla M. Koehler. « Mia40 Protein Serves as an Electron Sink in the Mia40-Erv1 Import Pathway ». Journal of Biological Chemistry 290, n^o 34 (17 juin 2015) : 20804–14. http://dx.doi.org/10.1074/jbc.m115.669440.

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A redox-regulated import pathway consisting of Mia40 and Erv1 mediates the import of cysteine-rich proteins into the mitochondrial intermembrane space. Mia40 is the oxidoreductase that inserts two disulfide bonds into the substrate simultaneously. However, Mia40 has one redox-active cysteine pair, resulting in ambiguity about how Mia40 accepts numerous electrons during substrate oxidation. In this study, we have addressed the oxidation of Tim13 in vitro and in organello. Reductants such as glutathione and ascorbate inhibited both the oxidation of the substrate Tim13 in vitro and the import of Tim13 and Cmc1 into isolated mitochondria. In addition, a ternary complex consisting of Erv1, Mia40, and substrate, linked by disulfide bonds, was not detected in vitro. Instead, Mia40 accepted six electrons from substrates, and this fully reduced Mia40 was sensitive to protease, indicative of conformational changes in the structure. Mia40 in mitochondria from the erv1–101 mutant was also trapped in a completely reduced state, demonstrating that Mia40 can accept up to six electrons as substrates are imported. Therefore, these studies support that Mia40 functions as an electron sink to facilitate the insertion of two disulfide bonds into substrates.

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Thorman, Rachel M., Ragesh Kumar T. P., D. Howard Fairbrother et Oddur Ingólfsson. « The role of low-energy electrons in focused electron beam induced deposition : four case studies of representative precursors ». Beilstein Journal of Nanotechnology 6 (16 septembre 2015) : 1904–26. http://dx.doi.org/10.3762/bjnano.6.194.

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Focused electron beam induced deposition (FEBID) is a single-step, direct-write nanofabrication technique capable of writing three-dimensional metal-containing nanoscale structures on surfaces using electron-induced reactions of organometallic precursors. Currently FEBID is, however, limited in resolution due to deposition outside the area of the primary electron beam and in metal purity due to incomplete precursor decomposition. Both limitations are likely in part caused by reactions of precursor molecules with low-energy (<100 eV) secondary electrons generated by interactions of the primary beam with the substrate. These low-energy electrons are abundant both inside and outside the area of the primary electron beam and are associated with reactions causing incomplete ligand dissociation from FEBID precursors. As it is not possible to directly study the effects of secondary electrons in situ in FEBID, other means must be used to elucidate their role. In this context, gas phase studies can obtain well-resolved information on low-energy electron-induced reactions with FEBID precursors by studying isolated molecules interacting with single electrons of well-defined energy. In contrast, ultra-high vacuum surface studies on adsorbed precursor molecules can provide information on surface speciation and identify species desorbing from a substrate during electron irradiation under conditions more representative of FEBID. Comparing gas phase and surface science studies allows for insight into the primary deposition mechanisms for individual precursors; ideally, this information can be used to design future FEBID precursors and optimize deposition conditions. In this review, we give a summary of different low-energy electron-induced fragmentation processes that can be initiated by the secondary electrons generated in FEBID, specifically, dissociative electron attachment, dissociative ionization, neutral dissociation, and dipolar dissociation, emphasizing the different nature and energy dependence of each process. We then explore the value of studying these processes through comparative gas phase and surface studies for four commonly-used FEBID precursors: MeCpPtMe3, Pt(PF3)4, Co(CO)3NO, and W(CO)6. Through these case studies, it is evident that this combination of studies can provide valuable insight into potential mechanisms governing deposit formation in FEBID. Although further experiments and new approaches are needed, these studies are an important stepping-stone toward better understanding the fundamental physics behind the deposition process and establishing design criteria for optimized FEBID precursors.

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Walter, Peter, Micheal Holmes, Razib Obaid, Lope Amores, Xianchao Cheng, James P. Cryan, James M. Glownia et al. « The DREAM Endstation at the Linac Coherent Light Source ». Applied Sciences 12, n^o 20 (19 octobre 2022) : 10534. http://dx.doi.org/10.3390/app122010534.

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Free-electron lasers (FEL), with their ultrashort pulses, ultrahigh intensities, and high repetition rates at short wavelength, have provided new approaches to Atomic and Molecular Optical Science. One such approach is following the birth of a photo electron to observe ion dynamics on an ultrafast timescale. Such an approach presents the opportunity to decipher the photon-initiated structural dynamics of an isolated atomic and molecular species. It is a fundamental step towards understanding single- and non-linear multi-photon processes and coherent electron dynamics in atoms and molecules, ultimately leading to coherent control following FEL research breakthroughs in pulse shaping and polarization control. A key aspect for exploring photoinduced quantum phenomena is visualizing the collective motion of electrons and nuclei in a single reaction process, as dynamics in atoms/ions proceed at femtosecond (10−15 s) timescales while electronic dynamics take place in the attosecond timescale (10−18 s). Here, we report on the design of a Dynamic Reaction Microscope (DREAM) endstation located at the second interaction point of the Time-Resolved Molecular and Optical (TMO) instrument at the Linac Coherent Light Source (LCLS) capable of following the photon–matter interactions by detecting ions and electrons in coincidence. The DREAM endstation takes advantage of the pulse properties and high repetition rate of LCLS-II to perform gas-phase soft X-ray experiments in a wide spectrum of scientific domains. With its design ability to detect multi-ions and electrons in coincidence while operating in step with the high repetition rate of LCLS-II, the DREAM endstation takes advantage of the inherent momentum conservation of reaction product ions with participating electrons to reconstruct the original X-ray photon–matter interactions. In this report, we outline in detail the design of the DREAM endstation and its functionality, with scientific opportunities enabled by this state-of-the-art instrument.

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Ahn, Sung Joon, Pilkyung Moon, Tae-Hoon Kim, Hyun-Woo Kim, Ha-Chul Shin, Eun Hye Kim, Hyun Woo Cha et al. « Dirac electrons in a dodecagonal graphene quasicrystal ». Science 361, n^o 6404 (28 juin 2018) : 782–86. http://dx.doi.org/10.1126/science.aar8412.

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Quantum states of quasiparticles in solids are dictated by symmetry. We have experimentally demonstrated quantum states of Dirac electrons in a two-dimensional quasicrystal without translational symmetry. A dodecagonal quasicrystalline order was realized by epitaxial growth of twisted bilayer graphene rotated exactly 30°. We grew the graphene quasicrystal up to a millimeter scale on a silicon carbide surface while maintaining the single rotation angle over an entire sample and successfully isolated the quasicrystal from a substrate, demonstrating its structural and chemical stability under ambient conditions. Multiple Dirac cones replicated with the 12-fold rotational symmetry were observed in angle-resolved photoemission spectra, which revealed anomalous strong interlayer coupling with quasi-periodicity. Our study provides a way to explore physical properties of relativistic fermions with controllable quasicrystalline orders.

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Konoplev, Vitalii Evgenievich, Maxim Vladimirovich Tachev et Elena Anatolievna Ulyukina. « "POLYHEDRAL CONTRACTION" OF TETRAMETHYLAMMONIUM CLOSO-CARBOUNDECABORATE UNDER THE ACTION OF RUCL2(PPH3)3 ». Herald of Omsk University 25, n^o 1 (22 mai 2020) : 29–35. http://dx.doi.org/10.24147/1812-3996.2020.25(1).29-35.

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In this paper the objectives were not only to investigate new promising methods leading to a deep structural rearrangement of carboranes and metallacarboranes but also to try to fix, to isolate and to characterize the intermediates. At the same time considerable atten-tion is paid to the so-called "anti-wade" clusters formed during the reactions, the elec-tronic structure of which does not correspond to their actually observed geometry. It is shown that the interaction of 11-vertex monocarbon closo-carboundecaborane with tris(triphenylphosphine)ruthenium dichloride leads to a series of new metallacarborane complexes. For the first time it was possible to control the process of "polyhedral contrac-tion" of carborane {CB10} → (RuCB10} → {RuCB9} → {RuCB8} → {RuCB6} on the example of ruthenium complex and also to confirm experimentally each stage of the whole process. As a result of the reaction clusters of classical type and electron-deficient isocloso-/hypercloso-rutenacarborans {RuCB8}, {RuCB9} with 2n skeletal electrons were isolated.

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