Journal articles on the topic 'Delayed electrons'
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Roth, Ilan. "Formation of the delayed relativistic solar electrons." Journal of Atmospheric and Solar-Terrestrial Physics 70, no. 2-4 (February 2008): 490–95. http://dx.doi.org/10.1016/j.jastp.2007.08.073.
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Roth, Ilan. "Energetic Solar Electrons – Whistler Bootstrap, Magnetic Knots and Small-scale Reconnection." Proceedings of the International Astronomical Union 6, S274 (September 2010): 178–81. http://dx.doi.org/10.1017/s1743921311006879.
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AbstractThe (near) relativistic electrons, emanating from the solar corona in long-lasting, gradual events, are generally observed at 1 AU as delayed vs the less energetic, type-III beams. The observations are consistent with the delayed electrons being energized along the stretched post-CME coronal field lines, when the tail of an anisotropic seed population, which is injected in conjunction to the observed radioheliograph bursts, interacts with the self-excited whistler waves (bootstrap mechanism). These bursts indicate efficient processes where suprathermal seed electrons are injected as a result of magnetic reconnection at the marginally stable coronal configuration left behind the emerging CME. The dependence of the bootstrap mechanism on the electron injection raises the general question of the MHD description and its deviation over the small electron skin-depth scale. The similarity between MHD and knot theories allows one to characterize any turbulent magnetic configuration through topological invariants, while deviation over electron skin-depth scale, characterized by the generalized vorticity, which is enhanced due to density inhomogeneity, creates the conditions for the potential injection sites.
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Panaitescu, A. D., and W. T. Vestrand. "Properties of the Prompt Optical Counterpart Arising from the Cooling of Electrons in Gamma-Ray Bursts." Astrophysical Journal 938, no. 2 (October 1, 2022): 155. http://dx.doi.org/10.3847/1538-4357/ac9315.
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Abstract This work extends a contemporaneous effort to study the properties of the lower-energy counterpart synchrotron emission produced by the cooling of relativistic gamma-ray burst (GRB) electrons through radiation (synchrotron and self-Compton) emission and adiabatic losses. We derive the major characteristics (pulse duration, lag time after burst, and brightness relative to the burst) of the prompt optical counterpart (POC) occurring during or after the GRB. Depending on the magnetic field lifetime, duration of electron injection, and electron transit time Δt o from hard X-ray (GRB) to optical-emitting energies, a POC may appear during the GRB pulse (of duration δ t γ ) or after (delayed OC). The signature of counterparts arising from the cooling of GRB electrons is that POC pulses (Δt o < δ t γ ) last as long as the corresponding GRB pulse (δ t o ≃ δ t γ ), while delayed OC pulses (Δt o > δ t γ ) last as long as the transit time (δ t o ≃ Δt o ). If OC variability can be measured, then another signature for this OC mechanism is that the GRB variability is passed on to POCs but not to delayed OCs. Within the GRB electron cooling model for counterparts, POCs should be on average dimmer than delayed ones (consistent with the data), and harder GRB low-energy slopes β LE should be associated more often with the dimmer POCs. The latter sets an observational bias against detecting POCs from (the cooling of electrons in) GRBs with a hard slope β LE, making it more likely that the detected POCs of such bursts arise from another mechanism.
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Stevenson, Kenneth L., and Attila Horváth. "Prompt and Delayed Photoejection of Electrons in Aqueous Solution." Journal of the American Chemical Society 118, no. 25 (January 1996): 6088–89. http://dx.doi.org/10.1021/ja960863l.
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Lee, Sooheyong, Wonhyuk Jo, Anthony D. DiChiara, Timothy P. Holmes, Stephen Santowski, Yong Chan Cho, and Eric C. Landahl. "Probing Electronic Strain Generation by Separated Electron-Hole Pairs Using Time-Resolved X-ray Scattering." Applied Sciences 9, no. 22 (November 8, 2019): 4788. http://dx.doi.org/10.3390/app9224788.
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Photogeneration of excess charge carriers in semiconductors produces electronic strain. Under transient conditions, electron-hole pairs may be separated across a potential barrier. Using time-resolved X-ray diffraction measurements across an intrinsic AlGaAs/n-doped GaAs interface, we find that the electronic strain is only produced by holes, and that electrons are not directly observable by strain measurements. The presence of photoinduced charge carriers in the n-doped GaAs is indirectly confirmed by delayed heat generation via recombination.
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Emary, Clive. "Delayed feedback control in quantum transport." Philosophical Transactions of the Royal Society A: Mathematical, Physical and Engineering Sciences 371, no. 1999 (September 28, 2013): 20120468. http://dx.doi.org/10.1098/rsta.2012.0468.
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Feedback control in quantum transport has been predicted to give rise to several interesting effects, among them quantum state stabilization and the realization of a mesoscopic Maxwell's daemon. These results were derived under the assumption that control operations on the system are affected instantaneously after the measurement of electronic jumps through it. In this contribution, I describe how to include a delay between detection and control operation in the master equation theory of feedback-controlled quantum transport. I investigate the consequences of delay for the state stabilization and Maxwell's daemon schemes. Furthermore, I describe how delay can be used as a tool to probe coherent oscillations of electrons within a transport system and how this formalism can be used to model finite detector bandwidth.
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Yeretzian, Chahan, and Robert L. Whetten. "Delayed emission of electrons from C60 following energetic impact against graphite." Zeitschrift f�r Physik D Atoms, Molecules and Clusters 24, no. 2 (June 1992): 199–202. http://dx.doi.org/10.1007/bf01426705.
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Lee, Ja Min, Sae Won Lee, and Young Sik Kim. "Highly Charge Transport Thermally Activated Delayed Fluorescence Host Materials Based on Benzimidazole-Acridine Derivatives." Journal of Nanoscience and Nanotechnology 20, no. 8 (August 1, 2020): 5070–74. http://dx.doi.org/10.1166/jnn.2020.17821.
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We designed novel thermally activated delayed fluorescence (TADF) host molecules for blue electrophosphorescence by combining the electron acceptor benzimidazole (BI) unit and the electron donor acridine derivatives into a single molecular unit based on density functional theory (DFT). We obtained the energies of the first singlet (S1) and the first triplet (T1) excited states of the TADF materials by performing DFT and time-dependent DFT (TD-DFT) calculations to the ground state using dependence on charge transfer amounts for the optimal Hartree-Fock percentage in the exchange-correlation of TD-DFT. Using DFT and TD-DFT calculations, the large separation between the HOMO and LUMO caused a small difference in energy (ΔEST) between the S1 and T1 states. The host molecules retained high triplet energy and showed great potential for use in blue phosphorescent organic light-emitting diodes. The results showed that these molecules are promising TADF host materials because they have a low barrier to hole and electron injection, balanced charge transport for both holes and electrons, and a small ΔEST.
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Lee, JaMin, Sae Won Lee, and Young Sik Kim. "Noble Dibenzothiophene-Based Bipolar Hosts for Blue Organic Light-Emitting Diodes Using Thermally Activated Delayed Fluorescence." Journal of Nanoscience and Nanotechnology 20, no. 11 (November 1, 2020): 7191–95. http://dx.doi.org/10.1166/jnn.2020.18856.
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Novel thermally activated delayed fluorescence (TADF) host materials for blue electrophosphores-cence were designed by combining the electron acceptor dibenzothiophene (DBT) unit and the electron donor acridine derivatives into a single molecular unit by density functional theory (DFT). Depending on the optimal charge transfer, DFT and time-dependent DFT (TD-DFT) calculations for the ground state were performed to obtain the energy of the singlet (S1) and triplet (T1) excited states of the TADF material for Hartree-Fock percentage of TD-DFT. The sufficiently large separation between the HOMO and LUMO resulted in a small difference in energy (ΔEST) between the S1 and T1 states using DFT and TD-DFT calculations. The host molecules retained high triplet energy and showed great potential for use in blue organic light-emitting diodes (OLED). The results showed that these molecules are a good TADF host materials because they have a low barrier to hole and electron injection with a balanced charge transporting property for both holes and electrons, and a small ΔEST.
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Olshin, Pavel K., Jonathan M. Voss, Marcel Drabbels, and Ulrich J. Lorenz. "Accurate time zero determination in an ultrafast transmission electron microscope without energy filter." Applied Physics Letters 120, no. 10 (March 7, 2022): 104103. http://dx.doi.org/10.1063/5.0087850.
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In ultrafast transmission electron microscopy, time zero can be accurately determined by making use of the photon-induced near-field electron microscopy (PINEM) effect, which causes electrons interacting with the near fields of a nanoparticle to coherently gain or lose energy in multiples of the photon energy when the laser pump and electron probe pulse overlap in time. If the instrument is not equipped with an energy filter, which is required to observe the PINEM effect, the response of a sample is frequently monitored instead. However, the gradual or delayed onset of this response can render an accurate measurement as challenging. Here, we demonstrate a simple and accurate method for determining time zero without an energy filter that is based on the observation that the outline of a nanoparticle blurs when the electron and laser pulse overlap in time. We show that this phenomenon arises from the PINEM effect, which causes some electrons to gain a large energy spread, thus blurring the image due to the chromatic aberration of the imaging system. This effect can also be used to characterize the instrument response and determine the laser polarization in situ. Furthermore, it may find applications for mapping out the near fields of a nanoparticle without the help of an energy filter.
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Pasenow, B., J. V. Moloney, S. W. Koch, S. H. Chen, A. Becker, and A. Jaroń-Becker. "Nonequilibrium evolution of strong-field anisotropic ionized electrons towards a delayed plasma-state." Optics Express 20, no. 3 (January 18, 2012): 2310. http://dx.doi.org/10.1364/oe.20.002310.
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Lee, Ja Min, Sae Won Lee, and Young Sik Kim. "Designing Noble Benzimidazole-Based Bipolar Hosts for Blue Organic Light-Emitting Diodes Using Thermally Activated Delayed Fluorescence Materials." Journal of Nanoscience and Nanotechnology 20, no. 11 (November 1, 2020): 7196–200. http://dx.doi.org/10.1166/jnn.2020.18858.
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We designed a novel thermally activated delayed fluorescence (TADF) host molecules for blue elec-trophosphorescence by combining the electron acceptor benzimidazole (BI) unit and the electron donor acridine derivatives into a single molecular unit based on density functional theory (DFT). We obtained the energies of the first singlet (S1) and the first triplet (T1) excited states of the TADF materials by performing DFT and time-dependent DFT (TD-DFT) calculations on the ground state using dependence on charge transfer amounts for the optimal Hartree–Fock percentage in the exchange-correlation of TD-DFT. The DFT and TD-DFT calculations showed that the large separation between the highest occupied molecular orbital and the lowest unoccupied molecular orbital caused a small difference in energy (ΔEST) between the S1 and T1 states. The host molecules retained a high triplet energy and demonstrated a great potential for use in blue phosphorescent organic light-emitting diodes. The results showed that these molecules are promising host materials for TADF OLEDs because they have a low barrier to hole and electron injection, a balanced charge transport for both holes and electrons, and a small ΔEST.
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Suzuki, N., T. Hirade, F. Saito, and T. Hyodo. "Positronium formation reaction of trapped electrons and free positrons: delayed formation studied by AMOC." Radiation Physics and Chemistry 68, no. 3-4 (October 2003): 647–49. http://dx.doi.org/10.1016/s0969-806x(03)00286-x.
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Bui, Thanh-Tuân, Fabrice Goubard, Malika Ibrahim-Ouali, Didier Gigmes, and Frédéric Dumur. "Recent advances on organic blue thermally activated delayed fluorescence (TADF) emitters for organic light-emitting diodes (OLEDs)." Beilstein Journal of Organic Chemistry 14 (January 30, 2018): 282–308. http://dx.doi.org/10.3762/bjoc.14.18.
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The design of highly emissive and stable blue emitters for organic light emitting diodes (OLEDs) is still a challenge, justifying the intense research activity of the scientific community in this field. Recently, a great deal of interest has been devoted to the elaboration of emitters exhibiting a thermally activated delayed fluorescence (TADF). By a specific molecular design consisting into a minimal overlap between the highest occupied molecular orbital (HOMO) and the lowest unoccupied molecular orbital (LUMO) due to a spatial separation of the electron-donating and the electron-releasing parts, luminescent materials exhibiting small S1–T1 energy splitting could be obtained, enabling to thermally upconvert the electrons from the triplet to the singlet excited states by reverse intersystem crossing (RISC). By harvesting both singlet and triplet excitons for light emission, OLEDs competing and sometimes overcoming the performance of phosphorescence-based OLEDs could be fabricated, justifying the interest for this new family of materials massively popularized by Chihaya Adachi since 2012. In this review, we proposed to focus on the recent advances in the molecular design of blue TADF emitters for OLEDs during the last few years.
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Walker, David C., Stefan Karolczak, Hugh A. Gillis, and Gerald B. Porter. "Hot model of muonium formation in liquids." Canadian Journal of Chemistry 81, no. 3 (March 1, 2003): 199–203. http://dx.doi.org/10.1139/v03-011.
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The mechanism of formation of muonium atoms from positive muons was studied here through measurements of the yield of diamagnetic muon states in dipolar aprotic solvents and for scavenger solutions in hexane and methanol. The results are compared with published data on common solvents covering a full range of the physicochemical properties of liquids that affect an ionic formation mechanism, namely their static dielectric constants, electron mobilities, and radiolysis yields of electrons. It is concluded that muonium is not formed by a thermal charge-neutralization reaction in these chemically-active media, though that mechanism does contribute to muonium formation in inert media like liquefied noble gases. It is clear that muonium materializes on a much shorter timescale than the recently proposed "delayed" mechanism (microseconds) and the earlier "spur" model (nanoseconds). In contrast, the data referring to all these liquids are consistent with the intra-track "hot" model. This is the only Mu-formation model proposed so far in which the immediate precursors of Mu (Mu(hot)) are neither scavengable nor ionic.Key words: muonium atoms, formation mechanism, hot model, spur model, delayed-muonium-formation model, diamagnetic yields.
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Lazutin, L. L., R. Rasinkangas, T. V. Kozelova, A. Korth, H. Singer, G. Reeves, W. Riedler, K. Torkar, and B. B. Gvozdevsky. "Observations of substorm fine structure." Annales Geophysicae 16, no. 7 (July 31, 1998): 775–86. http://dx.doi.org/10.1007/s00585-998-0775-5.
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Abstract. Particle and magnetic field measurements on the CRRES satellite were used, together with geosynchronous satellites and ground-based observations, to investigate the fine structure of a magnetospheric substorm on February 9, 1991. Using the variations in the electron fluxes, the substorm activity was divided into several intensifications lasting about 3–15 minutes each. The two main features of the data were: (1) the intensifications showed internal fine structure in the time scale of about 2 minutes or less. We call these shorter periods activations. Energetic electrons and protons at the closest geosynchronous spacecraft (1990 095) were found to have comparable activation structure. (2) The energetic (>69 keV) proton injections were delayed with respect to electron injections, and actually coincided in time with the end of the intensifications and partial returns to locally more stretched field line configuration. We propose that the energetic protons could be able to control the dynamics of the system locally be quenching the ongoing intensification and possibly preparing the final large-scale poleward movement of the activity. It was also shown that these protons originated from the same intensification as the preceeding electrons. Therefore, the substorm instability responsible for the intensifications could introduce a negative feedback loop into the system, creating the observed fine structure with the intensification time scales.Key words. Magnetospheric Physics (Storms and substorms).
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Rath, M. C., J. A. Mondal, D. K. Palit, T. Mukherjee, and H. N. Ghosh. "Femtosecond Transient Absorption Studies in Cadmium Selenide Nanocrystal Thin Films Prepared by Chemical Bath Deposition Method." Journal of Nanomaterials 2007 (2007): 1–7. http://dx.doi.org/10.1155/2007/36271.
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Dynamics of photo-excited carrier relaxation processes in cadmium selenide nanocrystal thin films prepared by chemical bath deposition method have been studied by nondegenerate femtosecond transient pump-probe spectroscopy. The carriers were generated by exciting at 400 nm laser light and monitored by several other wavelengths. The induced absorption followed by a fast bleach recovery observed near and above the bandgap indicates that the photo-excited carriers (electrons) are first trapped by the available traps and then the trapped electrons absorb the probe light to show a delayed absorption process. The transient decay kinetics was found to be multiexponential in nature. The short time constant,<1 picosecond, was attributed to the trapping of electrons by the surface and/or deep traps and the long time constant,≥20 picoseconds, was due to the recombination of the trapped carriers. A very little difference in the relaxation processes was observed in the samples prepared at bath temperatures from25∘Cto60∘C.
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Dhar, Purbarun, Ankur Chattopadhyay, Lakshmi Sirisha Maganti, and Anilakkad Raman Harikrishnan. "Streamer evolution arrest governed amplified AC breakdown strength of graphene and CNT colloids." European Physical Journal Applied Physics 85, no. 3 (March 2019): 30402. http://dx.doi.org/10.1051/epjap/2019180360.
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The present paper explores the concept of improving the AC dielectric breakdown strength of insulating mineral oils by the addition of graphene or carbon nanotubes (CNTs) to form stable dispersions. Experimental observations of graphene and CNT nano-oils show that not only improved average breakdown voltage, but also significantly improved reliability and survival probabilities of the oils under AC high voltage stressing is achieved. Improvement of the tune of ∼70–80% in the AC breakdown voltage of the oils has been obtained. The study examines the reliability of such nano-colloids using a two-parameter Weibull distribution and the oils show greatly augmented electric field bearing capacity. The fundamental mechanism responsible for such observed outcomes is reasoned to be delayed streamer development and reduced streamer growth rates due to effective electron scavenging. A mathematical model based on the principles of electron scavenging is proposed to quantify the amount of electrons scavenged by the nanostructures.
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KLOTS, C. E., and R. N. COMPTON. "EVIDENCE FOR THERMIONIC EMISSION FROM SMALL AGGREGATES." Surface Review and Letters 03, no. 01 (February 1996): 535–40. http://dx.doi.org/10.1142/s0218625x96000978.
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The delayed emission of electrons from small isolated aggregates has been reported now by several laboratories. When the emission is from a negative ion, it can plausibly be identified with the vibrational autoionization which has been known for many years from ions such as [Formula: see text]. Whether delayed emission from neutral species should be called “thermionic” is more problematic. Do these aggregates sample all of the available phase space prior to emission? We examine the experimental evidence which bears on this question. Particular reference is made to studies of “metallic” aggregates and of caged carbon clusters. Tantalizing evidence for the thermionic paradigm is noted, although recent experiments with niobium clusters can only be understood by postulating that they have unusual thermodynamic properties. Finally, Schottky’s expression for the effect of an externally applied electric field on a work function is extended to aggregates of arbitrary size.
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Schmidt-Böcking, Horst, and Gernot Gruber. "On Producing Long-Lived Spin Polarized Metastable Atoms—Feasibility of Storing Electric Energy." Atoms 10, no. 3 (July 18, 2022): 76. http://dx.doi.org/10.3390/atoms10030076.
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We describe a method of producing long-lived multiply excited spin polarized atoms or ions, the decay of which is strongly delayed or even blocked by intra-ionic magnetic stabilization. Special configurations with huge internal magnetic fields capture only spin polarized electrons in collisions with spin aligned atomic hydrogen gas targets. It is expected that the spin aligned configuration yields an extremely high internal magnetic field which will effectively block spin flip transitions. By this the lifetime of inner shell vacancies is expected to strongly increase.
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Eisfeld, Eugen, Daniel Förster, Dominic Klein, and Johannes Roth. "Atomistic simulation of ultra-short pulsed laser ablation of Al: an extension for non-thermalized electrons and ballistic transport." Journal of Physics D: Applied Physics 55, no. 13 (December 29, 2021): 135301. http://dx.doi.org/10.1088/1361-6463/ac41f9.
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Abstract For our model material aluminum, the influence of laser pulse duration in the range between 0.5 and 16 ps on the ablation depth is investigated in a computational study with a hybrid approach, combining molecular dynamics with the well known two-temperature model. A simple, yet expedient extension is proposed to account for the delayed thermalization as well as ballistic transport of the excited electrons. Comparing the simulated ablation depths to a series of our own experiments, the extension is found to considerably increase the predictive power of the model.
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Vermeeren, Ludo, Willem Leysen, and Benoit Brichard. "Radiation induced currents in mineral-insulated cables and in pick-up coils: model calculations and experimental verification in the BR1 reactor." EPJ Web of Conferences 170 (2018): 02008. http://dx.doi.org/10.1051/epjconf/201817002008.
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Mineral-insulated (MI) cables and Low-Temperature Co-fired Ceramic (LTCC) magnetic pick-up coils are intended to be installed in various position in ITER. The severe ITER nuclear radiation field is expected to lead to induced currents that could perturb diagnostic measurements. In order to assess this problem and to find mitigation strategies models were developed for the calculation of neutron-and gamma-induced currents in MI cables and in LTCC coils. The models are based on calculations with the MCNPX code, combined with a dedicated model for the drift of electrons stopped in the insulator. The gamma induced currents can be easily calculated with a single coupled photon-electron MCNPX calculation. The prompt neutron induced currents requires only a single coupled neutron-photon-electron MCNPX run. The various delayed neutron contributions require a careful analysis of all possibly relevant neutron-induced reaction paths and a combination of different types of MCNPX calculations. The models were applied for a specific twin-core copper MI cable, for one quad-core copper cable and for silver conductor LTCC coils (one with silver ground plates in order to reduce the currents and one without such silver ground plates). Calculations were performed for irradiation conditions (neutron and gamma spectra and fluxes) in relevant positions in ITER and in the Y3 irradiation channel of the BR1 reactor at SCK•CEN, in which an irradiation test of these four test devices was carried out afterwards. We will present the basic elements of the models and show the results of all relevant partial currents (gamma and neutron induced, prompt and various delayed currents) in BR1-Y3 conditions. Experimental data will be shown and analysed in terms of the respective contributions. The tests were performed at reactor powers of 350 kW and 1 MW, leading to thermal neutron fluxes of 1E11 n/cm2s and 3E11 n/cm2s, respectively. The corresponding total radiation induced currents are ranging from 1 to 7 nA only, putting a challenge on the acquisition system and on the data analysis. The detailed experimental results will be compared with the corresponding values predicted by the model. The overall agreement between the experimental data and the model predictions is fairly good, with very consistent data for the main delayed current components, while the lower amplitude delayed currents and some of the prompt contributions show some minor discrepancies.
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Liu, Hui Lan. "Study on Peanut Leaves’ Delayed Luminescence Characteristic under Excitation of Alternating Electric Field." Advanced Materials Research 108-111 (May 2010): 1244–49. http://dx.doi.org/10.4028/www.scientific.net/amr.108-111.1244.
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In this paper, peanut leaves’ delayed luminescence characteristic under excitation of alternating electric field was studied. The decay law of Delayed Luminescence Intensity with time and the change of Initial Light Intensity and Attenuation parameters with the frequency, peak voltage and excitation time of alternating electric field were observed. It was found that: Under the three kinds of excitation, the leaves’ Delayed Luminescence all presented the hyperbolic decay law with the time. In the frequency ranging from 4000HZ to 30000HZ，the Initial Light Intensity showed a trend of first increasing and then decreasing, but attenuation parameters showed a trend of first increasing then decreasing, increasing again and reducing again. In the excitation time ranging from 5min to 30min, the Initial Light Intensity and attenuation parameters all showed a trend of first increasing and then decreasing with the frequency increasing; In the peak voltage ranging from 500v to 10000v, the Initial Light Intensity showed a trend of first decreasing and then increasing with the peak voltage increasing, but attenuation parameters showed a trend of first increasing and then decreasing. The reason is mainly due to that the frequency, the peak voltage and excitation time of alternating electric field have an effect on the electrons transition in non-bonding oxygen atom which locates on chlorophyll’s carbonyl.
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Le Dé, Brieuc, Christian J. Eckhardt, Dante M. Kennes, and Michael A. Sentef. "Cavity engineering of Hubbard U via phonon polaritons." Journal of Physics: Materials 5, no. 2 (April 1, 2022): 024006. http://dx.doi.org/10.1088/2515-7639/ac618e.
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Abstract Pump-probe experiments have suggested the possibility to control electronic correlations by driving infrared-active (IR-active) phonons with resonant midinfrared laser pulses. In this work we study two possible microscopic nonlinear electron-phonon interactions behind these observations, namely coupling of the squared lattice displacement either to the electronic density or to the double occupancy. We investigate whether photon-phonon coupling to quantized light in an optical cavity enables similar control over electronic correlations. We first show that inside a dark cavity electronic interactions increase, ruling out the possibility that T c in superconductors can be enhanced via effectively decreased electron-electron repulsion through nonlinear electron-phonon coupling in a cavity. We further find that upon driving the cavity, electronic interactions decrease. Two different regimes emerge: (i) a strong coupling regime where the phonons show a delayed response at a time proportional to the inverse coupling strength, and (ii) an ultra-strong coupling regime where the response is immediate when driving the phonon polaritons resonantly. We further identify a distinctive feature in the electronic spectral function when electrons couple to phonon polaritons involving an IR-active phonon mode, namely the splitting of the shake-off band into three bands. This could potentially be observed by angle-resolved photoemission spectroscopy.
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Wang, Xiaoyi, Marie-Pierre Chauvat, Pierre Ruterana, and Thomas Walther. "Investigation of phase separation in InGaN alloys by plasmon loss spectroscopy in a TEM." MRS Advances 1, no. 40 (2016): 2749–56. http://dx.doi.org/10.1557/adv.2016.542.
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ABSTRACTPhase separation of InxGa1-xN alloys into Ga-rich and In-rich regions was observed by a number of research groups for samples grown with high indium content, x. Due to the radiation sensitivity of InGaN to beam damage by fast electrons, high-resolution imaging in transmission electron microscopy (TEM) or core-loss electron energy-loss spectroscopy (EELS) may lead to erroneous results. Low-loss EELS can yield spectra of the plasmon loss regions at much lower electron fluxes. Unfortunately, due to their delayed edge onset, the low energetic core losses of Ga and In partially overlap with the plasmon peaks, all of which shift with indium content.Here we demonstrate a method to quantify phase separation in InGaN thin films from the low-loss region in EELS by simultaneously fitting both plasmon and core losses over the energy range of 13-30eV. Phase separation is shown to lead to a broadening of the plasmon peak and the overlapping core losses, resulting in an unreliable determination of the indium concentration from analyzing the plasmon peak position alone if phase separation is present. For x=0.3 and x=0.59, the relative contributions of the binary compounds are negligibly small and indicate random alloys. For xnom.=0.62 we observed strong broadening, indicating phase separation.
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Savel’ev, A., O. Chefonov, A. Ovchinnikov, M. Agranat, and K. M. Spohr. "Direct detection of delayed high energy electrons from the181Ta target irradiated by a moderate intensity femtosecond laser pulse." Plasma Physics and Controlled Fusion 59, no. 3 (January 30, 2017): 035004. http://dx.doi.org/10.1088/1361-6587/aa5427.
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Stevenson, Kenneth L., Pamela B. Bell, Ravi S. Dhawale, Ottó Horváth, and Attila Horváth. "Prompt and delayed photoejection of hydrated electrons in the UV photolysis of aqueous solutions of copper(I) complexes." Radiation Physics and Chemistry 55, no. 5-6 (August 1999): 489–96. http://dx.doi.org/10.1016/s0969-806x(99)00235-2.
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Муллахметов, И. Р., В. С. Саенко, А. П. Тютнев, and Е. Д. Пожидаев. "Низкотемпературная радиационная электропроводность полистирола под действием электронов низких энергий." Журнал технической физики 93, no. 1 (2023): 130. http://dx.doi.org/10.21883/jtf.2023.01.54072.207-22.
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A technique has been developed and, for the first time, sufficiently complete data on the radiation-induced conductivity (RIC) of polystyrene (PS) at a temperature of 79 K, close to the boiling point of liquid nitrogen (77 K). RIC has been studied under pulsed and continuous exposure to electrons with an energy of 50 keV. It is shown that the RIC of PS at a temperature of 79K, as well as at room temperature, determined by the sum of two components: prompt and delayed. Both components at 79K are much smaller than at 298K. The total signal falls off by a factor of 40, while the delayed component falls off by a factor of almost 200, and the prompt component dominant in the RIC signal. The possibility of the occurrence of electrostatic discharges (ESD) in PS with decreasing temperature was studied. It has been shown that PS, which is capable of resisting the occurrence of ESD at room temperature, at 79K passes into the category of materials in which ESD is possible.
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Li, Jinshi, Pingchuan Shen, Zujin Zhao, and Ben Zhong Tang. "Through-Space Conjugation: A Thriving Alternative for Optoelectronic Materials." CCS Chemistry 1, no. 2 (June 2019): 181–96. http://dx.doi.org/10.31635/ccschem.019.20180020.
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Efficient electronic coupling is the key to constructing optoelectronic functional π systems. Generally, the delocalization of π electrons must comply with the framework constructed by covalent bonds (typically σ bonds), representing classic through-bond conjugation. However, through-space conjugation offers an alternative that achieves spatial electron communication with closely stacked π systems instead of covalent bonds thus enabling multidimensional energy and charge transport. Because of the ever-accelerating advances of through-space conjugation studies, researchers are inspired greatly by the beauty of through-space conjugated systems and their potential in high-tech applications. In this mini review, we introduce some representative and newly developed π systems having the through-space conjugation feature. In addition to discussing the profound impacts of through-space conjugation on the luminescence properties and charge transport, we will review some impressive findings of distinctive molecules with attractive characteristics, such as aggregation-induced emission, thermally activated delayed fluorescence, bipolar charge transport, and multichannel. These achievements may bring about new breakthroughs of theory, materials, and devices in the fields of organic electronics and molecular electronics.
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Turk, G. C., and N. Omenetto. "Optical Detection of Laser-Induced Ionization: A Study of the Time Decay of Strontium Ions in the Air-Acetylene Flame." Applied Spectroscopy 40, no. 8 (November 1986): 1085–92. http://dx.doi.org/10.1366/0003702864507756.
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Strontium atoms in the air-acetylene flame are directly photoionized in two steps provided by one dye laser tuned at the resonance ground-state transition (460.733 nm) and by the excimer pump beam at 308 nm, partially split from the amplifier section of the dye laser. The ions produced are then monitored by a third laser beam, colinear and counterpropagating in the flame, tuned to an ionic fluorescence transition and delayed in time with respect to the ionizing beams. In this way a fast decay, which is not affected by variations in the electron number density in the flame and therefore attributed to ion chemistry, and a slow decay, due to recombination, could clearly be observed. The fast decay is affected by variations in the flame stoichiometry and the slow decay by the number density of electrons in the flame, as shown by the addition of varying concentrations of an easily ionized element like caesium. The advantages of this optical probing of the laser-induced ionization in flames are discussed.
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Holmlid, Leif. "MeV particles in a decay chain process from laser-induced processes in ultra-dense deuterium D(0)." International Journal of Modern Physics E 24, no. 04 (April 2015): 1550026. http://dx.doi.org/10.1142/s0218301315500263.
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The ejection of particles with energy up to 20 MeV u-1 was reported previously from laser-induced processes in ultra-dense deuterium D(0). Studies of the kinetics of particle formation and decay, and of particle penetration through thick plates are now reported. Magnetic deflection is used to remove charged particles like electrons formed at the target. The signals at a collector in the beam at 0.9 m distance and a shadowed loop collector behind a 1.5–4.5 mm thick steel plate at 0.6 m are compared. The signal at the distant collector matches an intermediate particle B in a decay chain A → B → C with formation and decay time constants of 5–15 ns. The signal at the loop collector is delayed relative to the more distant collector, thus showing a delay of the particles penetrating through the steel plate. The signal at this collector is due to pair production with charge cancellation. Compton electrons from gamma radiation are observed at peak current densities of 1 mA cm-2 at the distant collector.
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Mazumdar, Ashish Kumar, Gyana Prakash Nanda, Nisha Yadav, Upasana Deori, Upasha Acharyya, Bahadur Sk, and Pachaiyappan Rajamalli. "Thermally activated delayed fluorescence (TADF) emitters: sensing and boosting spin-flipping by aggregation." Beilstein Journal of Organic Chemistry 18 (September 8, 2022): 1177–87. http://dx.doi.org/10.3762/bjoc.18.122.
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Metal-free organic emitters with thermally activated delayed fluorescence (TADF) characteristics are emerging due to the potential applications in optoelectronic devices, time-resolved luminescence imaging, and solid-phase sensing. Herein, we synthesized two (4-bromobenzoyl)pyridine (BPy)-based donor–acceptor (D–A) compounds with varying donor size and strength: the emitter BPy-pTC with tert-butylcarbazole (TC) as the donor and BPy-p3C with bulky tricarbazole (3C) as the donor unit. Both BPy-pTC and BPy-p3C exhibited prominent emission with TADF properties in solution and in the solid phase. The stronger excited-state charge transfer was obtained for BPy-p3C due to the bulkier donor, leading to a more twisted D–A geometry than that of BPy-pTC. Hence, BPy-p3C exhibited aggregation-induced enhanced emission (AIEE) in a THF/water mixture. Interestingly, the singlet–triplet energy gap (ΔEST) was reduced for both compounds in the aggregated state as compared to toluene solution. Consequently, a faster reverse intersystem crossing rate (kRISC) was obtained in the aggregated state, facilitating photon upconversion, leading to enhanced delayed fluorescence. Further, the lone-pair electrons of the pyridinyl nitrogen atom were found to be sensitive to acidic protons. Hence, the exposure to acid and base vapors using trifluoroacetic acid (TFA) and triethylamine (TEA) led to solid-phase fluorescence switching with fatigue resistance. The current study demonstrates the role of the donor strength and size in tuning ΔEST in the aggregated state as well as the relevance for fluorescence-based acid–base sensing.
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MAVROMATOS, NICK E. "STRING QUANTUM GRAVITY, LORENTZ-INVARIANCE VIOLATION AND GAMMA RAY ASTRONOMY." International Journal of Modern Physics A 25, no. 30 (December 10, 2010): 5409–85. http://dx.doi.org/10.1142/s0217751x10050792.
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In the first part of the review, I discuss ways of obtaining Lorentz-Invariance Violating (LIV) space–time foam in the modern context of string theory, involving brane world scenarios. The foamy structures are provided by lower-dimensional background brane defects in a D3-brane universe, whose density is a free parameter to be constrained phenomenologically. Such constraining can be provided by high energy gamma ray photon tests, including ultra-high energy/infrared photon–photon scattering. In the second part, I analyze the currently available data from MAGIC and FERMI telescopes on delayed cosmic photon arrivals in this context. It is understood of course that conventional astrophysics source effects, which currently are far from being understood, might be the dominant reason for the observed delayed arrivals. I also discuss how the stringent constraints from studies of synchrotron-radiation from distant Nebulae, absence of cosmic birefringence and nonobservation of ultra-high energy cosmic photons can be accommodated within the aforementioned stringy space–time foam model. I argue that, at least within the currently available sets of astrophysical data, the stringy foam model can avoid all theses constraints in a natural range of the string coupling and mass scale. The key features are: (i) transparency of the foam to electrons and charged probes in general, (ii) absence of birefringence effects and (iii) a breakdown of the local effective Lagrangian formalism. However, in order to accommodate, in this theoretical framework, the data of the FERMI satellite on the delayed arrival of photons from the short intense Gamma Ray Burst GRB 090510, in a way consistent with the findings of the MAGIC telescope, a nonuniform density of brane foam defects must be invoked.
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Ramachandran, R., A. A. Deshpande, and B. W. Stappers. "Search for Single Scattering Events." International Astronomical Union Colloquium 177 (2000): 565–68. http://dx.doi.org/10.1017/s0252921100060632.
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Radio signals, during their passage through the intervening medium, are scattered due to irregularities in the density of free electrons in the interstellar medium. Signals from distant sources undergo, most often,strong & multiple scatteringwhile the signals from nearby sources may be onlyweakly scatteredeven at meter wavelengths. It is likely that the scattering of signals from some nearby sources is possibly non-multiple in nature and hence may show a distinct signature ofsingle or discrete scattering events. In such a situation we receive, along with the direct unscattered signal, only a few discrete delayed versions of the signal. In such a case, it appears possible to probe the properties (such as the size and the density contrast) of the discrete density-irregularities responsible for the scattering, if the associated delays can be measured.
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Zhang, Jiale, Bin Chen, Sijie Yu, Hui Tian, Yuqian Wei, Hechao Chen, Guangyu Tan, Yingjie Luo, and Xingyao Chen. "Implications for Additional Plasma Heating Driving the Extreme-ultraviolet Late Phase of a Solar Flare with Microwave Imaging Spectroscopy." Astrophysical Journal 932, no. 1 (June 1, 2022): 53. http://dx.doi.org/10.3847/1538-4357/ac6ce3.
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Abstract Extreme-ultraviolet late phase (ELP) refers to the second extreme-ultraviolet (EUV) radiation enhancement observed in certain solar flares, which usually occurs tens of minutes to several hours after the peak of soft X-ray emission. The coronal loop system that hosts the ELP emission is often different from the main flaring arcade, and the enhanced EUV emission therein may imply an additional heating process. However, the origin of the ELP remains rather unclear. Here we present the analysis of a C1.4 flare that features such an ELP, which is also observed in microwave wavelengths by the Expanded Owens Valley Solar Array. Similar to the case of the ELP, we find a gradual microwave enhancement that occurs about 3 minutes after the main impulsive phase microwave peaks. Radio sources coincide with both foot points of the ELP loops and spectral fits on the time-varying microwave spectra demonstrate a clear deviation of the electron distribution from the Maxwellian case, which could result from injected nonthermal electrons or nonuniform heating to the footpoint plasma. We further point out that the delayed microwave enhancement suggests the presence of an additional heating process, which could be responsible for the evaporation of heated plasma that fills the ELP loops, producing the prolonged ELP emission.
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Ahn, C. C., and O. L. Krivanek. "Excited State Lifetime Measurement By EEL-CL Coincidence." Proceedings, annual meeting, Electron Microscopy Society of America 43 (August 1985): 406–7. http://dx.doi.org/10.1017/s0424820100118904.
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The lifetime of an excited state can be measured by detecting both the excitation (by EELS) and the de-excitation (by catho- doluminescence), and measuring the delay between the two events. We have adapted this technique for the measurement of lifetimes in an electron microscope.The experimental set-up is shown in Fig. 1. The arrival time and the energy loss of single electrons is monitored by the EELS (Gatan 607), and the arrival time and wavelength of single photons is monitored by the CL spectrometer. Pulses corresponding to the two events are fed to a time-to-amplitude converter (TAC), which outputs a variable height pulse proportional to the delay between the events. If no second (stop) pulse is detected within a preset time interval, the TAC recognizes a “false start”, does not output anything, and starts looking for a “start” pulse again. Since the count rate in the CL channel was typically 10 to 100 times weaker than in the EEL channel, we minimized the false starts by using the CL signal as the start pulse and the EEL signal, suitably delayed, as the stop pulse. This yields a “reversed time” spectrum, but minimizes the dead time of the electronics.
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Jäger, Patrick, Katrina Brendle, Ulrike Schwarz, Miriam Himmelsbach, Markus K. Armbruster, Karin Fink, Patrick Weis, and Manfred M. Kappes. "Q and Soret Band Photoexcitation of Isolated Palladium Porphyrin Tetraanions Leads to Delayed Emission of Nonthermal Electrons over Microsecond Time Scales." Journal of Physical Chemistry Letters 7, no. 7 (March 15, 2016): 1167–72. http://dx.doi.org/10.1021/acs.jpclett.6b00407.
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Shishkina, N. S., O. V. Karastoyanova, N. I. Fedyanina, and N. V. Korovkina. "Application of complex radiation and refrigeration technology for antiseptic treatment and preservation of the quality of mushrooms." Proceedings of the Voronezh State University of Engineering Technologies 82, no. 3 (October 19, 2020): 58–64. http://dx.doi.org/10.20914/2310-1202-2020-3-58-64.
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The use of effective physical processing methods to preserve food and agricultural products is gaining more and more popularity every year. This article presents a complex technology, including processing by accelerated electrons with doses of 1–3 kGy at a beam energy of 5 MeV. The efficiency of application of processing with accelerated electrons and modification of the composition of the gaseous medium for optimization of the technology of refrigerated storage of champignon mushrooms has been investigated. The technology parameters have been established to ensure microbiological safety and preservation of the consumer qualities of mushrooms under production conditions. The treatment with accelerated electrons at doses of 1–3 kGy in combination with cooling and modification of the composition of the gaseous medium delayed the postharvest maturation processes and led to an increase in the storage time of mushrooms up to 20 days (control 10–14 days). The modification of the composition of the gaseous medium was ensured by the selective gas permeability of the used packaging material (polypropylene, polyethylene, biaxially oriented polypropylene) and the respiration of the raw material. Depending on the intended purpose of the product - fresh sale or further processing (drying, freezing, etc.), the technology under consideration, due to the differentiated choice of technological parameters of storage and processing, allows to control changes in organoleptic, physicochemical and microbiological indicators of the quality of mushrooms in a targeted manner. Packaging made of biaxially oriented polypropylene and polypropylene should be used for mushrooms for processing, due to the best preservation of the structure of plant tissue, as a result of slowing down the ripening processes and delaying aging and spoilage, for the sale of fresh mushrooms, it is most effective to use polyethylene packaging.
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Fujikawa, Mayu, Kazuo Kobayashi, and Takahiro Kozawa. "Direct Oxidation of the [2Fe-2S] Cluster in SoxR Protein by Superoxide." Journal of Biological Chemistry 287, no. 42 (August 20, 2012): 35702–8. http://dx.doi.org/10.1074/jbc.m112.395079.
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The [2Fe-2S] transcription factor SoxR is activated by reversible one-electron oxidation of its [2Fe-2S] cluster, leading to enhanced production of various antioxidant proteins through induction of the soxRS regulon in Escherichia coli. Recently, there has been considerable debate about whether superoxide (O2̇̄) activates SoxR directly. To elucidate the underlying activation mechanism, we investigated SoxR interaction with O2̇̄ using pulse radiolysis. Radiolytically generated hydrated electrons reduced the oxidized form of the [2Fe-2S] cluster of SoxR within 2 μs. A subsequent increase in absorption in the visible region corresponding to reoxidation of the [2Fe-2S] cluster was observed on a time scale of milliseconds. Addition of human copper/zinc superoxide dismutase inhibited this delayed oxidation in a concentration-dependent fashion (I50 = 1.0 μm), indicating that O2̇̄ oxidized the reduced form of SoxR directly. The second-order rate constant of this process was estimated to be 5 × 108m−1 s−1. A similar result was observed after pulse radiolysis of Pseudomonas aeruginosa SoxR. However, superoxide dismutase inhibited the oxidation of reduced SoxR much more effectively in P. aeruginosa, even at a lower concentration (I50 = 80 nm), indicating that the soxRS response is much more sensitive to O2̇̄ in E. coli than in P. aeruginosa. These results suggest that SoxR proteins play a distinct regulatory role in the activation of O2̇̄.
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Wu, Lishuang, Huiwen Xu, and Huishan Yang. "Realization of Efficient Phosphorescent Organic Light-Emitting Devices Using Exciplex-Type Co-Host." Micromachines 13, no. 1 (December 29, 2021): 51. http://dx.doi.org/10.3390/mi13010051.
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High-performance phosphorescent organic light-emitting devices with an exciplex-type co-host were fabricated. The co-host is constituted by 1,3,5-tris(N-phenylbenzimidazol-2-yl) benzene, and 4,4,4-tris (N-carbazolyl) triphenylamine, and has obvious virtues in constructing efficient devices because of the thermally activated delayed fluorescence (TADF) resulting from a reverse intersystem crossing (RISC) process. The highest external quantum efficiency and luminance are 14.60% and 100,900 cd/m2 for the optimal co-host device. For comparison, 9.22% and 25,450 cd/m2 are obtained for a device employing 4,4,4-tris (N-carbazolyl) triphenylamine as a single-host. Moreover, the efficiency roll-off is notably alleviated for the co-host device, indicated by much higher critical current density of 327.8 mA/cm2, compared to 120.8 mA/cm2 for the single-host device. The alleviation of excitons quenching resulting from the captured holes and electrons, together with highly sufficient energy transfer between the co-host and phosphorescent dopant account for the obvious boost in device performances.
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Law, Marcus A., Francis Lockwood Estrin, Mark D. Bowden, and James W. Bradley. "Diagnosing asymmetric bipolar HiPIMS discharges using laser Thomson scattering." Plasma Sources Science and Technology 30, no. 10 (October 1, 2021): 105019. http://dx.doi.org/10.1088/1361-6595/ac2be4.
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Abstract The temporal evolution of the electron temperature T e and density n e has been measured at two positions on the centre-line of an asymmetrically pulsed bi-polar HiPIMS plasma using incoherent laser Thomson scattering (LTS). The magnetron was operated with a tungsten target in argon atmospheres. The results show that in the plasma afterglow when positive voltage pulses are applied (above a threshold of at least 200 V) significant heating of the electrons can occur in which T e can rise to values comparable to the those measured in HiPIMS on-time. The on-set of the rises in T e are significantly delayed relative to the start of the positive pulse, with the delay time decreasing with the magnitude of the positive voltage. The delay is only weakly dependent on the operating pressure. The presence of large positive pulses can also affect the local electron density with n e seen to decay significantly more quickly in the afterglow than for the corresponding unipolar pulsing case, in which no positive pulse is applied. The LTS measurements were complemented by a time-resolved study of the plasma optical emission (neutral argon and tungsten lines). With increasing positive potentials applied in the afterglow the Ar(I) line intensities grow consistent with increasing T e. Interestingly, W(I) line intensities are detected in the afterglow with positive voltages >200 V despite the termination of all target sputtering, suggesting that tungsten is being re-sputtered from the vessel walls. With the aid of emissive probe measurements of the spatial and temporal evolution of plasma potential profile along the centre-line we discuss the phenomena of plasma electron heating and wall sputtering in the positive pulse. This is done in terms of the existence of a non-sustained reverse discharge, in which the vessel walls become an effective cathode.
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Putra, M. E., M. N. Cahyadi, B. Muslim, I. N. Muafiry, and M. Wulansari. "Analysis of Tsunami Traveling Ionospheric Disturbances Due to Tsunami Using The GNSS-TEC Method." IOP Conference Series: Earth and Environmental Science 1127, no. 1 (January 1, 2023): 012003. http://dx.doi.org/10.1088/1755-1315/1127/1/012003.
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Abstract The Global Navigation Satellite System (GNSS) is a navigation satellite system that provides information on the position and speed of 3D objects on the earth’s surface. GNSS is increasingly being used in the field of survey and mapping work because of its high measurement accuracy, and its use can be done anywhere and anytime. The working principle of GNSS is to transmit digital data from satellites to receivers on the earth’s surface. The digital data is carried by a carrier microwave called the L-band. In the propagation path, the carrier microwave will pass through the ionosphere and troposphere. The collection of electrons contained in the ionosphere layer and the wet & dry components in the troposphere can disrupt the wave propagation path to be slower. This slow propagation will cause the accuracy of the results obtained during the measurement to be more inaccurate. The delayed wave data can obtain the Total Electron Content (TEC) value in the ionosphere layer. TEC is a value that represents the electron density in 1m2 in the ionosphere. The vertical movement of the land surface and seawater can suddenly cause acoustic waves that propagate towards the ionosphere layer, which causes the electron density to decompose. These disorders are known as Traveling Ionospheric Disturbances (TID). In this study, we studied the characteristics of the change in electron density in the ionosphere caused by the tsunami. The tsunami observed was a tsunami in the territory of Indonesia due to the eruption of Mount Tonga on January 15, 2022. The change in electron density was calculated from the significant difference in the TEC value during the tsunami propagation time. The calculation of the change in the TEC value is called the TEC reduction. TEC reduction is obtained by calculating the TEC value, calculated with the reference value of the polynomial curve. The result of the TEC reduction, which has a change in value at the same time as the tsunami is coming, is most likely the TID of the tsunami.
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Guarnieri, Fernando L., Bruce T. Tsurutani, Luis E. A. Vieira, Rajkumar Hajra, Ezequiel Echer, Anthony J. Mannucci, and Walter D. Gonzalez. "A correlation study regarding the AE index and ACE solar wind data for Alfvénic intervals using wavelet decomposition and reconstruction." Nonlinear Processes in Geophysics 25, no. 1 (January 31, 2018): 67–76. http://dx.doi.org/10.5194/npg-25-67-2018.
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Abstract. The purpose of this study is to present a wavelet interactive filtering and reconstruction technique and apply this to the solar wind magnetic field components detected at the L1 Lagrange point ∼ 0.01 AU upstream of the Earth. These filtered interplanetary magnetic field (IMF) data are fed into a model to calculate a time series which we call AE∗. This model was adjusted assuming that magnetic reconnection associated with southward-directed IMF Bz is the main mechanism transferring energy into the magnetosphere. The calculated AE∗ was compared to the observed AE (auroral electrojet) index using cross-correlation analysis. The results show correlations as high as 0.90. Empirical removal of the high-frequency, short-wavelength Alfvénic component in the IMF by wavelet decomposition is shown to dramatically improve the correlation between AE∗ and the observed AE index. It is envisioned that this AE∗ can be used as the main input for a model to forecast relativistic electrons in the Earth's outer radiation belts, which are delayed by ∼ 1 to 2 days from intense AE events.
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Carrington, C. D., D. J. Fluke, and M. B. Abou-Donia. "Target size of neurotoxic esterase and acetylcholinesterase as determined by radiation inactivation." Biochemical Journal 231, no. 3 (November 1, 1985): 789–92. http://dx.doi.org/10.1042/bj2310789.
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The target size of neurotoxic esterase (NTE), the putative target site for the initiation of organophosphorus-compound-induced delayed neurotoxicity, and acetylcholinesterase (AChE) from hen brain were examined by determining the rate at which the activities of the esterases were destroyed by ionizing irradiation. Samples of hen brain were prepared by slowly drying a microsomal preparation under vacuum. The dried samples were then irradiated with electrons from a 1 MeV Van de Graaff generator. The doses ranged from 0 to 28 Mrad. The radiation doses were calibrated by the rate of inactivation of T1-bacteriophage plaque induction. Following the irradiation procedure, the samples were resuspended in buffer and enzymic activity was measured. The target size of NTE from hen brain was determined to be about 105 kDa, whereas hen brain AChE was found to have a target size of about 53 kDa. The target size of NTE was found to be similar in experiments with rat brain and cat brain. In addition, commercial preparations of electric-eel electric-organ AChE and horse serum butyrylcholinesterase were found to have target sizes that were identical with each other, and also were very similar to that of AChE from hen brain.
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Held, A., and E. W. Schlag. "The Role of Electric Fields and Ion Concentrations in the Formation and Stabilization of High-n Rydberg States." Laser Chemistry 18, no. 1-2 (January 1, 1998): 13–33. http://dx.doi.org/10.1155/1998/63741.
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ZEro Kinetic Energy (ZEKE) spectroscopy relies on electrons produced through delayed field ionization of the narrow band of high-n Rydberg states which exist just below the ionization limit of each ionic eigenstate. Using the unique properties of these weakly bound, stable, high-n Rydberg states (ZEKE states) below the ionization limit rather than the unbound states above the limit, as in PES, leads to an improvement in resolution of more than two orders of magnitude. Several different types of ZEKE experiments, each designed to probe the formation and stability of these states, are presented here. These experiments were performed with pulsed and static electric fields of different magnitude and duration at different ion concentrations. The results indicate an enhanced ZEKE state decay with increasing electric field strengths and an enhanced formation and stabilization with increasing ion concentrations. A strong interplay between field strength and ion concentration ZEKE state formation is demonstrated. The strong influence of electric fields and ion concentrations on the physical properties of the ZEKE state, above and below the classical ionization threshold, is also demonstrated through late time (tens of microseconds) decay rate measurements.
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Kolmašová, Ivana, Ondřej Santolík, Jakub Šlegl, Jana Popová, Zbyněk Sokol, Petr Zacharov, Ondřej Ploc, et al. "Continental thunderstorm ground enhancement observed at an exceptionally low altitude." Atmospheric Chemistry and Physics 22, no. 12 (June 20, 2022): 7959–73. http://dx.doi.org/10.5194/acp-22-7959-2022.
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Abstract. Two long-lasting thunderstorm ground enhancement (TGE) events were registered at the Milešovka meteorological observatory in Czechia (50.55∘ N, 13.93∘ E; 837 m altitude) on 23 April 2018, during linearly organized thunderstorms. Two intervals of increased photon counts were detected by a plastic scintillator, respectively lasting 70 and 25 min and reaching 31 % and 48 % above the background radiation levels. Using numerical simulations, we verified that the observed increases in count rates are consistent with the energy spectrum of previously observed TGEs. We investigated the relevant data from a suite of meteorological instruments, a Ka-band cloud radar, an electric field mill, and a broadband electromagnetic receiver, all placed at the Milešovka observatory, in order to analyse the context in which these unique continental TGEs occurred at an exceptionally low altitude. The onset of the TGEs preceded the onset of precipitation by 10 and 3 min, respectively, for the two events. Both this delayed rain arrival and an energy threshold of 6.5 MeV for registered particles clearly exclude the detection the decay products of the radon progeny washout during the TGE intervals. At the same time, the European lightning detection network EUCLID detected numerous predominantly negative intracloud lightning discharges at distances closer than 5 km from the particle detector, while the occurrence of cloud-to-ground discharges was suppressed. The cloud radar recorded presence of graupel below the melting level, and the composition of hydrometeors suggested good conditions for cloud electrification. The observed variations in the near-surface electric field were unusual, with very brief negative-electric-field excursions reaching −20 kV in a quick succession. At the same time, sub-microsecond unipolar pulses emitted by close corona discharges saturated the broadband magnetic loop antenna. All these measurements indicate that a strong lower positive-charge region was present inside the thundercloud. The bottom thundercloud dipole was probably responsible for acceleration of the seed electrons in the air. These seed electrons might originate in the secondary cosmic ray particles but could also come from a high concentration of radon in the air collected during the propagation of the convective system above the uranium-rich soils before the thunderstorms overpassed the Milešovka observatory.
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Petheö, Gábor L., Andrés Maturana, András Spät, and Nicolas Demaurex. "Interactions between Electron and Proton Currents in Excised Patches from Human Eosinophils." Journal of General Physiology 122, no. 6 (November 24, 2003): 713–26. http://dx.doi.org/10.1085/jgp.200308891.
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The NADPH–oxidase is a plasma membrane enzyme complex that enables phagocytes to generate superoxide in order to kill invading pathogens, a critical step in the host defense against infections. The oxidase transfers electrons from cytosolic NADPH to extracellular oxygen, a process that requires concomitant H+ extrusion through depolarization-activated H+ channels. Whether H+ fluxes are mediated by the oxidase itself is controversial, but there is a general agreement that the oxidase and H+ channel are intimately connected. Oxidase activation evokes profound changes in whole-cell H+ current (IH), causing an approximately −40-mV shift in the activation threshold that leads to the appearance of inward IH. To further explore the relationship between the oxidase and proton channel, we performed voltage-clamp experiments on inside-out patches from both resting and phorbol-12-myristate-13-acetate (PMA)-activated human eosinophils. Proton currents from resting cells displayed slow voltage-dependent activation, long-term stability, and were blocked by micromolar internal [Zn2+]. IH from PMA-treated cells activated faster and at lower voltages, enabling sustained H+ influx, but ran down within minutes, regaining the current properties of nonactivated cells. Bath application of NADPH to patches excised from PMA-treated cells evoked electron currents (Ie), which also ran down within minutes and were blocked by diphenylene iodonium (DPI). Run-down of both IH and Ie was delayed, and sometimes prevented, by cytosolic ATP and GTP-γ-S. A good correlation was observed between the amplitude of Ie and both inward and outward IH when a stable driving force for e− was imposed. Combined application of NADPH and DPI reduced the inward IH amplitude, even in the absence of concomitant oxidase activity. The strict correlation between Ie and IH amplitudes and the sensitivity of IH to oxidase-specific agents suggest that the proton channel is either part of the oxidase complex or linked by a membrane-limited mediator.
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Ayache, Eliot H., Hendrik J. van Eerten, and Frédéric Daigne. "Late X-ray flares from the interaction of a reverse shock with a stratified ejecta in GRB afterglows: simulations on a moving mesh." Monthly Notices of the Royal Astronomical Society 495, no. 3 (May 25, 2020): 2979–93. http://dx.doi.org/10.1093/mnras/staa1397.
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ABSTRACT Late activity of the central engine is often invoked in order to explain the flares observed in the early X-ray afterglow of gamma-ray bursts, either in the form of an active neutron star remnant or (fall-back) accretion on to a black hole. However, these scenarios are not always plausible, in particular when flares are delayed to very late times after the burst. Recently, a new scenario was proposed that suggests X-ray flares can be the result of the passing of a long-lived reverse shock through a stratified ejecta, with the advantage that it does not require late-time engine activity. In this work, we numerically demonstrate this scenario to be physically plausible, by performing one-dimensional simulations of ejecta dynamics and emission using our novel moving-mesh relativistic hydrodynamics code. Improved efficiency and precision over previous work enables the exploration of a broader range of set-ups. We can introduce a more physically realistic description of the circumburst medium mass density. We can also locally trace the cooling of electrons when computing the broad-band emission from these set-ups. We show that the synchrotron cooling time-scale can dominate the flare decay time if the stratification in the ejecta is constrained to a localized angular region inside the jet, with size corresponding to the relativistic causal connection angle, and that it corresponds to values reported in observations. We demonstrate that this scenario can produce a large range of observed flare times, suggesting a connection between flares and initial ejection dynamics rather than with late-time remnant activity.
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Taylor, N., N. Omenetto, B. W. Smith, and J. D. Winefordner. "Lifetime Measurements of Several S, P, and D States of Thallium in a Glow Discharge by Single-Step and Two-Step Laser-Excited Fluorescence." Applied Spectroscopy 62, no. 1 (January 2008): 78–85. http://dx.doi.org/10.1366/000370208783412582.
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The lifetimes of several states in a thallium see-through hollow cathode discharge, or galvatron, are obtained to characterize its potential as an atomic line filter. The lifetimes of the thallium 6 2D3/2, 6 2D5/2, and 7 2S1/2 states are measured by time-resolved single-step laser-excited fluorescence by use of a 276.787 nm laser pulse or a 535.046 nm laser pulse and measuring the resulting fluorescence waveform at the appropriate wavelength. Values of 6.4 ± 0.1, 7.5 ± 1.1, and 7.7 ± 0.2 ns were obtained for the 6 2D3/2, 6 2D5/2, and 7 2S1/2 states, respectively, which agree with values obtained by previous authors, as well as calculated values. No current dependence was observed for each of these states. The lifetime of the long-lived thallium 6 2P3/2° metastable state was measured by two-step laser-excited fluorescence at various applied currents. The metastable level was pumped by a 276.787 nm laser pulse, and a temporally delayed 535.046 nm laser pulse interrogated the population of the metastable state. Relating the fluorescence intensity to the population of the metastable state as a function of delay time yielded a decay curve for the 6 2P3/2° metastable state. Values of 2.1 ± 0.2, 2.8 ± 0.1, 3.1 ± 0.3, 3.8 ± 0.4, and 4.8 ± 0.6 μs were found for applied currents of 14.0, 12.0, 10.0, 8.0, and 6.0 mA, respectively. The resulting lifetimes for the 6 2P3/2° metastable state clearly show a dependence on the applied current and are expected to be due to collisions with the wall of the cathode, as well as a contribution due to collisions with electrons.
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Kouloumvakos, A., R. Y. Kwon, L. Rodríguez-García, D. Lario, N. Dresing, E. K. J. Kilpua, R. Vainio, et al. "The first widespread solar energetic particle event of solar cycle 25 on 2020 November 29." Astronomy & Astrophysics 660 (April 2022): A84. http://dx.doi.org/10.1051/0004-6361/202142515.
Full textAbstract:
Context. On 2020 November 29, an eruptive event occurred in an active region located behind the eastern solar limb as seen from Earth. The event consisted of an M4.4 class flare, a coronal mass ejection, an extreme ultraviolet (EUV) wave, and a white-light (WL) shock wave. The eruption gave rise to the first widespread solar energetic particle (SEP) event of solar cycle 25, which was observed at four widely separated heliospheric locations (∼230°). Aims. Our aim is to better understand the source of this widespread SEP event, examine the role of the coronal shock wave in the wide distribution of SEPs, and investigate the shock wave properties at the field lines magnetically connected to the spacecraft. Methods. Using EUV and WL data, we reconstructed the global three-dimensional structure of the shock in the corona and computed its kinematics. We determined the magnetic field configurations in the corona and interplanetary space, inferred the magnetic connectivity of the spacecraft with the shock surface, and derived the evolution of the shock parameters at the connecting field lines. Results. Remote sensing observations show formation of the coronal shock wave occurring early during the eruption, and its rapid propagation to distant locations. The results of the shock wave modelling show multiple regions where a strong shock has formed and efficient particle acceleration is expected to take place. The pressure/shock wave is magnetically connected to all spacecraft locations before or during the estimated SEP release times. The release of the observed near-relativistic electrons occurs predominantly close to the time when the pressure/shock wave connects to the magnetic field lines or when the shock wave becomes supercritical, whereas the proton release is significantly delayed with respect to the time when the shock wave becomes supercritical, with the only exception being the proton release at the Parker Solar Probe. Conclusions. Our results suggest that the shock wave plays an important role in the spread of SEPs. Supercritical shock regions are connected to most of the spacecraft. The particle increase at Earth, which is barely connected to the wave, also suggests that the cross-field transport cannot be ignored. The release of energetic electrons seems to occur close to the time when the shock wave connects to, or becomes supercritical at, the field lines connecting to the spacecraft. Energetic protons are released with a time-delay relative to the time when the pressure/shock wave connects to the spacecraft locations. We attribute this delay to the time that it takes for the shock wave to accelerate protons efficiently.