scholarly journals Low-Energy Electron Damage to Condensed-Phase DNA and Its Constituents

2021 ◽  
Vol 22 (15) ◽  
pp. 7879
Author(s):  
Yingxia Gao ◽  
Yi Zheng ◽  
Léon Sanche
Keyword(s):  
Condensed Phase ◽  
Genetic Material ◽  
High Energy ◽  
Dna Lesions ◽  
Low Energy ◽  
Experimental Investigations ◽  
Experimental Conditions ◽  
Strand Breaks ◽  
Sequence Of Events ◽  
Wide Range

The complex physical and chemical reactions between the large number of low-energy (0–30 eV) electrons (LEEs) released by high energy radiation interacting with genetic material can lead to the formation of various DNA lesions such as crosslinks, single strand breaks, base modifications, and cleavage, as well as double strand breaks and other cluster damages. When crosslinks and cluster damages cannot be repaired by the cell, they can cause genetic loss of information, mutations, apoptosis, and promote genomic instability. Through the efforts of many research groups in the past two decades, the study of the interaction between LEEs and DNA under different experimental conditions has unveiled some of the main mechanisms responsible for these damages. In the present review, we focus on experimental investigations in the condensed phase that range from fundamental DNA constituents to oligonucleotides, synthetic duplex DNA, and bacterial (i.e., plasmid) DNA. These targets were irradiated either with LEEs from a monoenergetic-electron or photoelectron source, as sub-monolayer, monolayer, or multilayer films and within clusters or water solutions. Each type of experiment is briefly described, and the observed DNA damages are reported, along with the proposed mechanisms. Defining the role of LEEs within the sequence of events leading to radiobiological lesions contributes to our understanding of the action of radiation on living organisms, over a wide range of initial radiation energies. Applications of the interaction of LEEs with DNA to radiotherapy are briefly summarized.

scholarly journals The Dark Side of UV-Induced DNA Lesion Repair

Genes ◽  
2020 ◽  
Vol 11 (12) ◽  
pp. 1450
Author(s):  
Wojciech Strzałka ◽  
Piotr Zgłobicki ◽  
Ewa Kowalska ◽  
Aneta Bażant ◽  
Dariusz Dziga ◽  
...  
Keyword(s):  
Dna Damage ◽  
Dna Repair ◽  
Uv Light ◽  
Genetic Material ◽  
Dna Lesions ◽  
Dark Side ◽  
Repair System ◽  
Strand Breaks ◽  
Dna Lesion ◽  
Pyrimidine Dimers

In their life cycle, plants are exposed to various unfavorable environmental factors including ultraviolet (UV) radiation emitted by the Sun. UV-A and UV-B, which are partially absorbed by the ozone layer, reach the surface of the Earth causing harmful effects among the others on plant genetic material. The energy of UV light is sufficient to induce mutations in DNA. Some examples of DNA damage induced by UV are pyrimidine dimers, oxidized nucleotides as well as single and double-strand breaks. When exposed to light, plants can repair major UV-induced DNA lesions, i.e., pyrimidine dimers using photoreactivation. However, this highly efficient light-dependent DNA repair system is ineffective in dim light or at night. Moreover, it is helpless when it comes to the repair of DNA lesions other than pyrimidine dimers. In this review, we have focused on how plants cope with deleterious DNA damage that cannot be repaired by photoreactivation. The current understanding of light-independent mechanisms, classified as dark DNA repair, indispensable for the maintenance of plant genetic material integrity has been presented.

Neutron Spectroscopy of Superconducting Fullerides

1992 ◽  
Vol 270 ◽  
Author(s):  
Kosmas Prassides ◽  
Christos Christides ◽  
John Tomkinson ◽  
Matthew J. Rosseinsky ◽  
D. W. Murphy ◽  
...  
Keyword(s):  
Low Temperatures ◽  
High Energy ◽  
Inelastic Neutron ◽  
Low Energy ◽  
Vibrational Modes ◽  
Phonon Coupling ◽  
Phonon Spectra ◽  
Electron Phonon Coupling ◽  
Wide Range ◽  
Mechanism Of Superconductivity

ABSTRACTThe phonon spectra of pristine fullerene, superconducting K3C60 and saturation-doped Rb6C60 measured by inelastic neutron scatteringin the energy range 2.5 - 200 meV at low temperatures reveal substantial broadening of five-fold degenerate Hg intramolecular vibrational modes both in the low-energy radial and the high-energy tangential part of the spectrum. This provides strong evidence for a traditional phonon-mediated mechanism of superconductivity in the fullerides but with an electron-phonon coupling strength distributed over a wide range of energies (33-195 meV) as a result of the finite curvature of the fullerene spherical cage.

scholarly journals Unravelling strong electronic interlayer and intralayer correlations in a transition metal dichalcogenide

2021 ◽  
Vol 12 (1) ◽  
Author(s):  
T. J. Whitcher ◽  
Angga Dito Fauzi ◽  
D. Caozheng ◽  
X. Chi ◽  
A. Syahroni ◽  
...  
Keyword(s):  
Transition Metal ◽  
Near Infrared ◽  
Theoretical Calculations ◽  
High Energy ◽  
Low Energy ◽  
Great Effort ◽  
Energy Bands ◽  
Electronic Correlations ◽  
X Ray ◽  
Wide Range

AbstractElectronic correlations play important roles in driving exotic phenomena in condensed matter physics. They determine low-energy properties through high-energy bands well-beyond optics. Great effort has been made to understand low-energy excitations such as low-energy excitons in transition metal dichalcogenides (TMDCs), however their high-energy bands and interlayer correlation remain mysteries. Herewith, by measuring temperature- and polarization-dependent complex dielectric and loss functions of bulk molybdenum disulphide from near-infrared to soft X-ray, supported with theoretical calculations, we discover unconventional soft X-ray correlated-plasmons with low-loss, and electronic transitions that reduce dimensionality and increase correlations, accompanied with significantly modified low-energy excitons. At room temperature, interlayer electronic correlations, together with the intralayer correlations in the c-axis, are surprisingly strong, yielding a three-dimensional-like system. Upon cooling, wide-range spectral-weight transfer occurs across a few tens of eV and in-plane p–d hybridizations become enhanced, revealing strong Coulomb correlations and electronic anisotropy, yielding a two-dimensional-like system. Our result shows the importance of strong electronic, interlayer and intralayer correlations in determining electronic structure and opens up applications of utilizing TMDCs on plasmonic nanolithrography.

scholarly journals MetroMMC: Electron-Capture Spectrometry with Cryogenic Calorimeters for Science and Technology

2019 ◽  
Vol 199 (1-2) ◽  
pp. 441-450 ◽  
Author(s):  
P. C.-O. Ranitzsch ◽  
D. Arnold ◽  
J. Beyer ◽  
L. Bockhorn ◽  
J. J. Bonaparte ◽  
...  
Keyword(s):  
Electron Capture ◽  
Science And Technology ◽  
High Energy ◽  
Low Energy ◽  
Energy Threshold ◽  
High Energy Resolution ◽  
Wide Energy Range ◽  
Good Resolution ◽  
X Ray ◽  
Wide Range

AbstractAccurate decay data of radionuclides are necessary for many fields of science and technology, ranging from medicine and particle physics to metrology. However, data that are in use today are mostly based on measurements or theoretical calculation methods that are rather old. Recent measurements with cryogenic detectors and other methods show significant discrepancies to both older experimental data and theory in some cases. Moreover, the old results often suffer from large or underestimated uncertainties. This is in particular the case for electron-capture (EC) decays, where only a few selected radionuclides have ever been measured. To systematically address these shortcomings, the European metrology project MetroMMC aims at investigating six radionuclides decaying by EC. The nuclides are chosen to cover a wide range of atomic numbers Z, which results in a wide range of decay energies and includes different decay modes, such as pure EC or EC accompanied by $$\gamma $$γ- and/or $$\beta ^{+}$$β+-transitions. These will be measured using metallic magnetic calorimeters (MMCs), cryogenic energy-dispersive detectors with high-energy resolution, low-energy threshold and high, adjustable stopping power that are well suited for measurements of the total decay energy and X-ray spectrometry. Within the MetroMMC project, these detectors are used to obtain X-ray emission intensities of external sources as well as fractional EC probabilities of sources embedded in a $$4\pi $$4π absorber. Experimentally determined nuclear and atomic data will be compared to state-of-the-art theoretical calculations which will be further developed within the project. This contribution introduces the MetroMMC project and in particular its experimental approach. The challenges in EC spectrometry are to adapt the detectors and the source preparation to the different decay channels and the wide energy range involved, while keeping the good resolution and especially the low-energy threshold to measure the EC from outer shells.

KLEIN–NISHINA EFFECTS IN THE PROMPT AND EXTENDED HIGH-ENERGY GAMMA-RAY EMISSION OF GAMMA-RAY BURSTS

2011 ◽  
Vol 20 (10) ◽  
pp. 2023-2027 ◽  
Author(s):  
XIANG-YU WANG ◽  
HAO-NING HE ◽  
ZHUO LI
Keyword(s):  
Gamma Ray ◽  
Early Time ◽  
High Energy ◽  
Gamma Ray Bursts ◽  
Low Energy ◽  
Large Area ◽  
Wide Range ◽  
Inverse Compton ◽  
Energy Gamma ◽  
Gamma Ray Emission

Prompt and extended high-energy (> 100 MeV) gamma-ray emission has been observed from more than ten gamma-ray bursts by Fermi Large Area Telescope (LAT). Such emission is likely to be produced by synchrotron radiation of electrons accelerated in internal or external shocks. We show that IC scattering of these electrons with synchrotron photons are typically in the Klein–Nishina (KN) regime. For the prompt emission, the KN effect can suppress the IC component and as a result, one single component is seen in some strong bursts. The KN inverse-Compton cooling may also affect the low-energy electron number distribution and hence result in a hard low-energy synchrotron photon spectrum. During the afterglow, KN effect makes the Compton-Y parameter generally less than 1 in the first seconds for a wide range of parameter space. Furthermore, we suggest that the KN effect can explain the somewhat faster-than-expected decay of the early-time high-energy emission observed in GRB090510 and GRB090902B.

Rare-Earth Doping by Ion Implantation and Related Techniques

1993 ◽  
Vol 301 ◽  
Author(s):  
Ian G. Brown
Keyword(s):  
Rare Earth ◽  
Ion Implantation ◽  
Rare Earths ◽  
High Energy ◽  
Ion Source ◽  
Low Energy ◽  
Vacuum Arc ◽  
Rare Earth Doping ◽  
Metal Plasma ◽  
Wide Range

ABSTRACTSome metal plasma techniques have been developed that provide a convenient means for the doping of semiconductor hosts with rare-earths. These plasma and ion beam tools are based on the application of vacuum arc discharges for the formation of dense rare-earth plasmas which then can be used in a number of ways for doping and otherwise introducing the rare-earths into substrate materials. At the low energy end of the spectrum, the streaming metal plasma can be used for the deposition of thin films, and if more than one plasma source is used then of multilayer structures also. Or by building the vacuum-arc rare-earth plasma generator into an ion source configuration, high current ion beams can be produced for doing high energy ion implantation; alternatively the substrate can be immersed in the streaming rare-earth plasma and by using appropriately phased high voltage substrate pulsing and pulsed plasma generation, plasma immersion ion implantation can be done. Between these two limiting techniques – low energy plasma deposition and high energy ion implantation – a spectrum of hybrid methods can be utilized for rare earth doping. We've made a number of plasma and ion sources of this kind, and we've doped a wide range of substrates with a wide range of rare-earths. For example we've implanted species including Sc, Y, La, Ce, Pr, Nd, Sm, Gd, Dy, Ho, Er and Yb into host materials including Si, GaAs, InP and more. The implantation dose can range from a low of about 1013 cm−2 up to as high as about 1017 cm−2, and the ion energy can be varied from a few tens of eV up to about 200 keV. Here we review these vacuum-arc-based plasma methods for rare-earth doping, describing both the tools and techniques that are available and the applications to which we've put the methods in our laboratory.

scholarly journals Review of the Geant4-DNA Simulation Toolkit for Radiobiological Applications at the Cellular and DNA Level

Cancers ◽  
2021 ◽  
Vol 14 (1) ◽  
pp. 35
Author(s):  
Ioanna Kyriakou ◽  
Dousatsu Sakata ◽  
Hoang Ngoc Tran ◽  
Yann Perrot ◽  
Wook-Geun Shin ◽  
...  
Keyword(s):  
High Energy ◽  
Low Energy ◽  
Radiation Quality ◽  
Simulation Code ◽  
Entire Genome ◽  
Strand Breaks ◽  
Beta Emitters ◽  
Single Strand Breaks ◽  
Energy Hadron ◽  
Radiobiological Effects

The Geant4-DNA low energy extension of the Geant4 Monte Carlo (MC) toolkit is a continuously evolving MC simulation code permitting mechanistic studies of cellular radiobiological effects. Geant4-DNA considers the physical, chemical, and biological stages of the action of ionizing radiation (in the form of x- and γ-ray photons, electrons and β±-rays, hadrons, α-particles, and a set of heavier ions) in living cells towards a variety of applications ranging from predicting radiotherapy outcomes to radiation protection both on earth and in space. In this work, we provide a brief, yet concise, overview of the progress that has been achieved so far concerning the different physical, physicochemical, chemical, and biological models implemented into Geant4-DNA, highlighting the latest developments. Specifically, the “dnadamage1” and “molecularDNA” applications which enable, for the first time within an open-source platform, quantitative predictions of early DNA damage in terms of single-strand-breaks (SSBs), double-strand-breaks (DSBs), and more complex clustered lesions for different DNA structures ranging from the nucleotide level to the entire genome. These developments are critically presented and discussed along with key benchmarking results. The Geant4-DNA toolkit, through its different set of models and functionalities, offers unique capabilities for elucidating the problem of radiation quality or the relative biological effectiveness (RBE) of different ionizing radiations which underlines nearly the whole spectrum of radiotherapeutic modalities, from external high-energy hadron beams to internal low-energy gamma and beta emitters that are used in brachytherapy sources and radiopharmaceuticals, respectively.

Toward Wideband Piezoelectric Harvesters Through Self-Powered Transitions to High-Energy Response

2019 ◽  
Vol 142 (1) ◽  
Author(s):  
Abdolreza Pasharavesh ◽  
M. T. Ahmadian
Keyword(s):  
Basin Of Attraction ◽  
Excitation Frequency ◽  
High Energy ◽  
Low Energy ◽  
Energy Response ◽  
Multivalued Solution ◽  
Time Period ◽  
Wide Range ◽  
Probabilistic Study ◽  
Self Powered

Abstract Convergence to low-energy responses arising from coexistence of multiple stable nodes is the main drawback of a nonlinear energy harvester preventing it from efficient wideband operation. A switching circuit with a boost-like topology has been proposed in this paper to overcome this substantial challenge. The circuit uses the energy harvested by the device to trigger it to jump from the low- to high-energy response. The performance of the proposed harvesting system when subjected to single harmonic excitations covering a wide range of frequencies is verified through both analytical and numerical investigations. Results indicate that by proper selection of timing parameters of the circuit including ON-time period of the switches together with the phase differences between the switching signals and the mechanical excitation, the applied electrical perturbation will be able to trigger the nonlinear resonating beam to jump from a low-energy response to the basin of attraction of the high-energy one within the whole frequency band in which a multivalued solution exists. Also, a probabilistic study is performed on a system with random phases of switching signals which shows that a successful switching from low- to high-energy response is achievable with a probability more than 80% by just controlling the ON-time period of the switch within the proper ranges with respect to the excitation frequency.

scholarly journals Length and Energy Dependence of Low-Energy Electron-Induced Strand Breaks in Poly(A) DNA

2019 ◽  
Vol 21 (1) ◽  
pp. 111
Author(s):  
Kenny Ebel ◽  
Ilko Bald
Keyword(s):  
Cross Section ◽  
Cross Sections ◽  
Strand Break ◽  
High Energy ◽  
Low Energy ◽  
Negative Ion ◽  
Strand Breaks ◽  
Dna Strand Break ◽  
The Absolute ◽  
Dna Strand

The DNA in living cells can be effectively damaged by high-energy radiation, which can lead to cell death. Through the ionization of water molecules, highly reactive secondary species such as low-energy electrons (LEEs) with the most probable energy around 10 eV are generated, which are able to induce DNA strand breaks via dissociative electron attachment. Absolute DNA strand break cross sections of specific DNA sequences can be efficiently determined using DNA origami nanostructures as platforms exposing the target sequences towards LEEs. In this paper, we systematically study the effect of the oligonucleotide length on the strand break cross section at various irradiation energies. The present work focuses on poly-adenine sequences (d(A4), d(A8), d(A12), d(A16), and d(A20)) irradiated with 5.0, 7.0, 8.4, and 10 eV electrons. Independent of the DNA length, the strand break cross section shows a maximum around 7.0 eV electron energy for all investigated oligonucleotides confirming that strand breakage occurs through the initial formation of negative ion resonances. When going from d(A4) to d(A16), the strand break cross section increases with oligonucleotide length, but only at 7.0 and 8.4 eV, i.e., close to the maximum of the negative ion resonance, the increase in the strand break cross section with the length is similar to the increase of an estimated geometrical cross section. For d(A20), a markedly lower DNA strand break cross section is observed for all electron energies, which is tentatively ascribed to a conformational change of the dA20 sequence. The results indicate that, although there is a general length dependence of strand break cross sections, individual nucleotides do not contribute independently of the absolute strand break cross section of the whole DNA strand. The absolute quantification of sequence specific strand breaks will help develop a more accurate molecular level understanding of radiation induced DNA damage, which can then be used for optimized risk estimates in cancer radiation therapy.

scholarly journals Superintense laser-driven photon activation analysis

2021 ◽  
Vol 4 (1) ◽  
Author(s):  
Francesco Mirani ◽  
Daniele Calzolari ◽  
Arianna Formenti ◽  
Matteo Passoni
Keyword(s):  
Activation Analysis ◽  
Materials Science ◽  
Photon Activation Analysis ◽  
High Energy ◽  
High Repetition Rate ◽  
Intense Laser ◽  
Photon Activation ◽  
Critical Material ◽  
Experimental Conditions ◽  
Wide Range

AbstractLaser-driven radiation sources are attracting increasing attention for several materials science applications. While laser-driven ions, electrons and neutrons have already been considered to carry out the elemental characterization of materials, the possibility to exploit high-energy photons remains unexplored. Indeed, the electrons generated by the interaction of an ultra-intense laser pulse with a near-critical material can be turned into high-energy photons via bremsstrahlung emission when shot into a high-Z converter. These photons could be effectively exploited to perform Photon Activation Analysis (PAA). In the present work, laser-driven PAA is proposed and investigated. We develop a theoretical approach to identify the optimal experimental conditions for laser-driven PAA in a wide range of laser intensities. Lastly, exploiting the Monte Carlo and Particle-In-Cell tools, we successfully simulate PAA experiments performed with both conventional accelerators and laser-driven sources. Under high repetition rate operation (i.e. 1−10 Hz) conditions, the ultra-intense lasers can allow performing PAA with performances comparable with those achieved with conventional accelerators. Moreover, laser-driven PAA could be exploited jointly with complementary laser-driven materials characterization techniques under investigation in existing laser facilities.

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