Search

Here we show an interplay between the structures present in ionization tracks and nucleocapsid RNA structural biology, using fast ion-beam inactivation of the severe acute respiratory syndrome coronavirus (SARS-CoV) virion as an example. This interplay could be a key factor in predicting dose-inactivation curves for high-energy ion-beam inactivation of virions. We also investigate the adaptation of well-established cross-section data derived from radiation interactions with water to the interactions involving the components of a virion, going beyond the density-scaling approximation developed previously. We conclude that solving one of the grand challenges of structural biology — the determination of RNA tertiary/quaternary structure — is linked to predicting ion-beam inactivation of viruses and that the two problems can be mutually informative. Indeed, our simulations show that fast ion beams have a key role to play in elucidating RNA tertiary/quaternary structure. [ABSTRACT FROM AUTHOR]

Recently, measurements of few-picosecond (ps, 10−12 s) pulses of laser-driven protons were realised by the observation of transient opacity in SiO2. This ultrafast response could be understood by the formation of self-trapped excitonic states in the material, creating a rapid de-excitation channel for conduction band electrons. Here we extend this work to examine the onset and evolution of an ion-induced opacity in transparent dielectrics, namely multicomponent variants of SiO2. The fast recovery observed in SiO2 is in sharp contrast to borosilicate (BK7) and soda-lime glasses. We find that the opacity decay timescales for BK7 and soda-lime glass are orders of magnitude greater than the 3.5 ps proton pump pulse duration and discuss the underlying processes which may be affecting the extended recovery of the material. Simultaneous probing with 2nd harmonic radiation allows estimates of ultrafast electron dynamics due to proton interactions in matter to be investigated, this indicates that a rapid evolution of an initially unstructured ion-induced dose distribution seeds the longer term recovery pathways in the irradiated dielectrics. When combined, these results demonstrate the efficacy of utilising ultrafast laser-driven ionising radiation along with highly synchronised probe pulses to enable the study of ion-induced damage in matter on ultrafast timescales in real time. [ABSTRACT FROM AUTHOR]

Nanoparticles offer alternative options in cancer therapy both as drug delivery carriers and as direct therapeutic agents for cancer cell inactivation. More recently, gold nanoparticles (AuNPs) have emerged as promising radiosensitizers achieving significantly elevated radiation dose enhancement factors when irradiated with both kilo-electron-volt and mega-electronvolt X-rays. Use of AuNPs in radiobiology is now being intensely driven by the desire to achieve precise energy deposition in tumours. As a consequence, there is a growing demand for efficient and simple techniques for detection, imaging and characterization of AuNPs in both biological and tumour samples. Spatially accurate imaging on the nanoscale poses a serious challenge requiring high- or super-resolution imaging techniques. In this mini review, we discuss the challenges in using AuNPs as radiosensitizers as well as various current and novel imaging techniques designed to validate the uptake, distribution and localization in mammalian cells. In our own work, we have used multiphoton excited plasmon resonance imaging to map the AuNP intracellular distribution. The benefits and limitations of this approach will also be discussed in some detail. In some cases, the same "excitation'' mechanism as is used in an imaging modality can be harnessed to make it also a part of therapy modality (e.g. phototherapy)--such examples are discussed in passing as extensions to the imaging modality concerned. [ABSTRACT FROM AUTHOR]

Radiotherapy employs ionizing radiation to induce lethal DNA lesions in cancer cells while minimizing damage to healthy tissues. Due to their pattern of energy deposition, better therapeutic outcomes can, in theory, be achieved with ions compared to photons. Antiprotons have been proposed to offer a further enhancement due to their annihilation at the end of the path. The work presented here aimed to establish and validate an experimental procedure for the quantification of plasmid and genomic DNA damage resulting from antiproton exposure. Immunocytochemistry was used to assess DNA damage in directly and indirectly exposed human fibroblasts irradiated in both plateau and Bragg peak regions of a 126 MeV antiproton beam at CERN. Cells were stained post irradiation with an anti- γ-H2AX antibody. Quantification of the γ-H2AX foci-dose relationship is consistent with a linear increase in the Bragg peak region. A qualitative analysis of the foci detected in the Bragg peak and plateau region indicates significant differences highlighting the different severity of DNA lesions produced along the particle path. Irradiation of desalted plasmid DNA with 5 Gy antiprotons at the Bragg peak resulted in a significant portion of linear plasmid in the resultant solution. [ABSTRACT FROM AUTHOR]

Sharp resonant structures in the cross section of the atomic electron-ion collision process of dielectronic recombination are exploited to study isotope shifts and hyperfine interaction of heavy highly-charged ions. This novel approach provides a conceptual alternative to existing methods. In this contribution, we present a series of measurements, which we performed at the heavy ion storage ring ESR of the GSI Helmholtzzentrum für Schwerionenforschung, Darmstadt, Germany. In a first experiment the stable isotopes A = 142 and A = 150 of three-electron neodymium ANd57+ were studied. Isotope shifts of dielectronic resonances associated with 2s - 2pj ( j = 1/2, 3/2) transitions were extracted from the measured data. The evaluation of the energy shift was performed within a full QED framework and yielded a change in the mean-square charge radius of 142,150δ⟨r²⟩ = -1.36(1)(3) fm². At GSI, in addition to the investigation of stable isotopes unstable species can be artificially synthesized and studied. Radioisotopes produced in-flight from fragmentation of a 238U primary beam were injected into the ESR and were subsequently separated by their mass-to-charge ratio. This enabled us to perform first DR experiments with the exotic nuclei 237U89+ (Z = 92) and 234Pa88+ (Z = 91). [ABSTRACT FROM AUTHOR]

Discusses the highlights of a research planned within the Stored Particle Atomic Physics Research Collaboration (SPARC) and Facility of Low-Energy Antiproton and Ion Research (FLAIR) in the U.S. Background on SPARC which has already become the largest atomic physics collaboration in the world; Four types of experimental studies at the Facility for Antiproton and Ion Research such as high-energy and low-energy beams; Two storage rings which are significant to FLAIR.

Describes the design and construction of a device for nondestructively monitoring the position of an electron beam. Mechanism for the detection of charges induced on the monitor electrodes; Calculations and experimental results which illustrate the performance of the device; Suitable applications.

A novel position-sensitive detector has been developed which consists of an array of electronsensing electrodes and a corresponding array of amplifiers and counters all integrated onto a single silicon chip. The integrated circuit is coupled with a microchannel plate electron multiplier so that it counts individual charged particles or photons. The detector array is capable of being extended by abutting individual detector chips side by side in the form of a hybrid circuit. The detector is currently in use on both electron-energy-loss and photoelectron spectrometers. [ABSTRACT FROM AUTHOR]

The effect of a cold (<40 °C) radio frequency-driven atmospheric pressure plasma jet on plasmid DNA has been investigated. Gel electrophoresis was used to analyze the DNA forms post-treatment. The experimental data are fitted to a rate equation model that allows for quantitative determination of the rates of single and double strand break formation. The formation of double strand breaks correlates well with the atomic oxygen density. Taken with other measurements, this indicates that neutral components in the jet are effective in inducing double strand breaks. [ABSTRACT FROM AUTHOR]

The string mode of operation for an electron beam ion source uses axially oscillating electrons in order to reduce power consumption, also simplifying the construction by omitting the collector with cooling requirements and has been called electron string ion source (ESIS). We have started a project (supported by INTAS and GSI) to use Schottky field emitting cathode tips for generating the electron string. The emission from these specially conditioned tips is higher by orders of magnitude than the focused Brillouin current density at magnetic fields of some Tesla and electron energies of some keV. This may avoid the observed instabilities in the transition from axially oscillating electrons to the string state of the electron plasma, opening a much wider field of possible operating parameters for an ESIS. Besides the presentation of the basic features, we emphasize in this paper a method to avoid damaging of the field emission tip by backstreaming ions. [ABSTRACT FROM AUTHOR]

An electron-beam ion trap (EBIT) has been designed for atomic physics experiments at the Queen’s University of Belfast. A pair of permanent magnets will be used to produce an axial magnetic field to compress an electron beam, whereas pairs of superconducting magnets have been used for traditional EBITs. The design of the new EBIT is detailed and possible experiments are explained to show the feasibility of the EBIT. © 2004 American Institute of Physics. [ABSTRACT FROM AUTHOR]

Describes the development of the electron beam ion trap (EBIT) in Tokyo, Japan. Limitation of the maximum electron energy through the insulation; Use of the EBIT as a tool for electron collision experiments; Suitability of the EBIT for spectroscopic studies.

Here we show that the determining factor for physical radiation enhancement effects for a clinically realistic cluster of heavy-atom bearing nanoparticles is the total number of heavy atoms packed into the cluster. We do this through a multiscale Monte Carlo approach which permits the consideration of radiation transport through clusters of millions of nanoparticles. The finding is in contrast to that predicted when isolated nanoparticles are considered and is a direct consequence of the Auger electrons playing less of a role for clusters compared to isolate nanoparticles. We further show that this result is agnostic to selection of the subcellular region considered to be sensitive to the effects of radiation, provided the inside the cluster of nanoparticles is not considered to be biologically active. [ABSTRACT FROM AUTHOR]

A method of injecting metallic elements into an electron-beam ion trap (EBIT) is described. The method is advantageous over the conventional coaxial and pulsed injection methods in two ways: (a) complicated switching of injection and extraction beams can be avoided when extracting beams of highly charged ions from the EBIT and (b) a beam of stable intensity can be achieved. This method may be applicable to any metallic elements or metallic compounds that have vapor pressures of ∼0.1 Pa at a temperature lower than 1900 °C. We have employed this method for the extraction of highly charged ions of Bi, Er, Fe, and Ho. [ABSTRACT FROM AUTHOR]