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Purpose: The frequency of DNA strand breaks produced by the decay of Auger electron-emitting radionuclides is inversely proportional to the distance of DNA nucleotides from the decay site; and thus is very sensitive to changes in the local conformation of the DNA. Analysis of the frequency of DNA breaks, or radioprobing, gives valuable information about the local DNA structure. More than 10 years ago, we demonstrated the feasibility of radioprobing using a DNA-repressor complex with a known structure. Herein, we used radioprobing to study the conformation of DNA in complex with the tumor suppressor protein 53 (p53). Several structures of p53-DNA complexes have been solved by X-ray crystallography. These structures, obtained with the p53 DNA binding domain, a truncated form, laid the groundwork for understanding p53-DNA interactions and their relation to p53 functions. However, whether all observed stereochemical details are relevant to the native p53-DNA complex remains unclear. A common theme of the crystallographic structures is the lack of significant bending in the central part of the DNA response element. In contrast, gel electrophoresis and electron microscopy data showed strong DNA bending and overtwisting upon binding to the native p53 tetramer. Methods: To analyze DNA in complex with p53, we incorporated 125I-dCTP in two different positions of synthetic duplexes containing the consensus p53-binding site. Results: The most significant changes in the break frequency distributions were detected close to the center of the binding site, which is consistent with an increase in DNA twisting in this region and local DNA bending and sliding. Conclusions: Our data confirm the main results of the studies made in solution and lay a foundation for systematic examination of interactions between DNA and native p53 using 125I radioprobing. [ABSTRACT FROM AUTHOR]

Purpose: The nanodosimetric description of the radiation action of Auger electrons on nitrogen targets of nanometric size is presented. Materials and methods: Experimental microdosimetry at nanometer scale for Auger electrons has been accomplished with the set-up called Jet Counter. This consists of a pulse-operated valve which injects an expanding nitrogen jet into an interaction chamber where a gaseous sensitive volume of cylindrical shape is created. The ionization cluster size distributions (ICSD) created by Auger electrons emitted by 125I while crossing a nanometer-sized volume have been measured. Results: The ICSD for the sensitive volumes corresponding to 3 and 12 nm in diameter (in unit density 1 g/cm3) irradiated by electrons emitted by a 125I source were collected and compared with the corresponding Monte Carlo (MC) simulation. The preliminary results of the experiments with Auger electrons of 125I interacting with a nitrogen jet having nanometric size comparable to a deoxyribonucleic acid (DNA) and nucleosome, showing the discrete spectrum of ICSD with extended cluster size, are described. Conclusions: The presented paper describes for the first time the nanodosimetric experiments with Auger electrons emitted by 125I. A set of the new descriptors of the radiation quality describing the radiation effect at nanometer level is proposed. The ICSD were determined for the first time for an Auger emitter of 125I. [ABSTRACT FROM AUTHOR]

Abstract: In-doped ZnO nanostructures with different indium concentrations were grown using a thermal evaporation method. The In-doped ZnO nanostructures with a low concentration of indium exhibited a javelin shape, while the In-doped ZnO nanostructures with a high concentration of indium showed a flake shape. In addition, undoped ZnO nanojavelins were grown under the same conditions, but the sizes of these undoped ZnO nanojavelins were larger than the In-doped ZnO nanojavelins. It was shown that the In3+ cations played a crucial role in controlling the size. X-ray diffraction and Raman spectroscopy clearly showed hexagonal structures for all of the products. However, the Raman results demonstrated that the In-doped ZnO nanoflakes had a lower crystalline quality than the In-doped ZnO nanojavelins. Furthermore, photoluminescence (PL) measurements confirmed the Raman results. Moreover, the PL results demonstrated a larger band-gap for the In-doped ZnO nanostructures in comparison to the undoped ZnO. [Copyright &y& Elsevier]

Abstract: 111In-DTPA-anti-γH2AX-Tat, which combines an anti-γH2AX antibody with a cell-penetrating peptide, Tat, and the Auger electron-emitting radioisotope, 111In, targets the DNA damage signalling protein, γH2AX, and has potential as a probe for imaging DNA damage in vivo. The goal of this study was to investigate whether 111In-DTPA-anti-γH2AX-Tat labelled to high specific activity (6MBq/μg) can amplify treatment-related DNA damage for therapeutic gain. Methods: MDA-MB-468 and MDA-MB-231/H2N (231-H2N) breast cancer cells were incubated with 111In-DTPA-anti-γH2AX-Tat (3MBq, 6MBq/μg) or a control radioimmunoconjugate, 111In-DTPA-mIgG-Tat, and exposed to IR or bleomycin. DNA damage was studied by counting γH2AX foci and by neutral comet assay. Cytotoxicity was evaluated using clonogenic assays. 111In-DTPA-anti-γH2AX-Tat was administered intravenously to 231-H2N-xenograft-bearing Balb/c nu/nu mice in tumor growth inhibition studies. Results: The number of γH2AX foci was greater after exposure of cells to IR (10Gy) plus 111In-DTPA-anti-γH2AX-Tat compared to IR alone (20.6±2.5 versus 10.4±2.3 foci/cell; P <.001).111In-DTPA-anti-γH2AX-Tat resulted in a reduced surviving fraction in cells co-treated with IR (4Gy) versus IR alone (5.2%±0.9% versus 47.8%±2.8%; P <.001). Similarly, bleomycin (25–200μg/mL) plus 111In-DTPA-anti-γH2AX-Tat resulted in a lower SF compared to bleomycin alone. The combination of a single exposure to IR (10Gy) plus 111In-DTPA-anti-γH2AX-Tat significantly decreased the growth rate of 231-H2N xenografts in vivo compared to either 111In-DTPA-anti-γH2AX-Tat or IR alone (−0.002±0.004 versus 0.036±0.011 and 0.031±0.014mm3/day, respectively, P <.001). Conclusion: 111In-DTPA-anti-γH2AX-Tat amplifies anticancer treatment-related DNA damage in vitro and has a potent anti-tumor effect when combined with IR in vivo. [Copyright &y& Elsevier]

Abstract: The experiment with 125I-Auger electrons, interacting with gaseous nitrogen with size equivalent to segment of DNA in mass per unit area scale, are described. The discrete ionization cluster-size distributions have been obtained. The shapes of which are definitely determined by the size of the interaction volumes. The volume sizes studied in the present work are comparable with a segment of DNA and of nucleosome. The experiments have been carried out with the set up, called Jet Counter, and are the first cluster-size distributions as yet measured for an Auger-electron emitter like 125I. The experimental results have been compared with those obtained by Monte Carlo simulation. The results for 125I have been compared with calculated cluster size distribution for 131I. [Copyright &y& Elsevier]

We explore the optimum growth space for a 47.0Å InAs/21.5 Å Ga0.75In0.25Sb superlattices (SLs) designed for the maximum Auger suppression for a very long wavelength infrared gap. Our growth process produces a consistent gap of 50 ± 5 meV. However, SL quality is sensitive to the growth temperature (Tg). For the SLs grown at 390-470 °C, a photoresponse signal gradually increases as Tg increases from 400 to 440 °C. Outside this temperature window, the SL quality deteriorates very rapidly. All SLs were n-type with mobility of ∼10 000 V/cm² and 300 K recombination lifetime of ∼70 ns for an optimized SL. [ABSTRACT FROM AUTHOR]

This article reviews different methods used to perform quantitative X-ray microanalysis in the electron microscope and also demonstrates the urgency of measuring the fundamental parameters of X-ray generation for the development of accurate standardless quantitative methods. Using ratios of characteristic lines acquired on the same X-ray spectrum, it is shown that the Cliff and Lorimer KA-B factor can be used in a general correction method that is appropriate for all types of specimens and electron microscopes, providing that appropriate corrections are made for X-ray absorption, fluorescence, and indirect generation. Since the fundamental parameters appear in the KA-B factor, only the ratio of the ionization cross sections needs to be known, not their absolute values. In this regard, the measurement of ratios of the KA-B factor (or intensities at different beam energies of the same material with no change of beam spreading in the material) permits the validation for the best models to compute the ratio of ionization cross sections. It is shown, using this method, that the nonrelativistic Bethe equation, to compute ionization cross section, is very close to the equation of E. Casnati et al. (J Phys B15, 155–167, 1982) and also to the equations proposed by D. Bote and F. Salvat (Phys Rev A77, 042701, 2008) for the computation of the ratio of ionization cross sections. The method is extended to show that it could be used to determine the values of the Coster-Kronig transitions factors, an important fundamental parameter for the generation of L and M lines that is mostly known with poor accuracy. The detector efficiency can be measured with specimens where their intensities were measured with an energy dispersive spectrometer detector, the efficiency of which has been measured in an X-ray synchrotron (M. Alvisi et al., Microsc Microanal12, 406–415, 2006). The spatial resolution should always be computed when performing quantitative X-ray microanalysis and the equations of R. Gauvin (Microsc Microanal13(5), 354–357, 2007) for bulk materials and the one presented in this article for thin films should be used. The effects of X-rays generated by fast secondary electrons and by Auger electrons are reviewed, and their effect can be detrimental for the spatial resolution of materials involving low-energy X-ray lines, in certain specific conditions. Finally, quantitative X-ray microanalysis of heterogeneous materials is briefly reviewed. [ABSTRACT FROM PUBLISHER]

Purpose: The open structure of euchromatin renders it susceptible to DNA damage by ionizing radiation (IR) compared with compact heterochromatin. The effect of chromatin configuration on the efficacy of Auger electron radiotherapy was investigated. Methods and Materials: Chromatin structure was altered in MDA-MB-468 and 231-H2N human breast cancer cells by suberoylanilide hydroxamic acid (SAHA), 5-aza-2-deoxycytidine, or hypertonic treatment. The extent and duration of chromatin structural changes were evaluated using the micrococcal nuclease assay. DNA damage (γH2AX assay) and clonogenic survival were evaluated after exposure to 111In-DTPA-hEGF, an Auger electron-emitting radiopharmaceutical, or IR. The intracellular distribution of 111In-DTPA-hEGF after chromatin modification was investigated in cell fractionation experiments. Results: Chromatin remained condensed for up to 20 minutes after NaCl and in a relaxed state 24 hours after SAHA treatment. The number of γH2AX foci per cell was greater in MDA-MB-468 and 231-H2N cells after IR (0.5 Gy) plus SAHA (1 μM) compared with IR alone (16 ± 0.6 and 14 ± 0.3 vs. 12 ± 0.4 and 11 ± 0.2, respectively). More γH2AX foci were observed in MDA-MB-468 and 231-H2N cells exposed to 111In-DTPA-hEGF (6 MBq/μg) plus SAHA vs. 111In-DTPA-hEGF alone (11 ± 0.3 and 12 ± 0.7 vs. 9 ± 0.4 and 7 ± 0.3, respectively). 5-aza-2-deoxycytidine enhanced the DNA damage caused by IR and 111In-DTPA-hEGF. Clonogenic survival was reduced in MDA-MB-468 and 231-H2N cells after IR (6 Gy) plus SAHA (1 μM) vs. IR alone (0.6% ± 0.01 and 0.3% ± 0.2 vs. 5.8% ± 0.2 and 2% ± 0.1, respectively) and after 111In-DTPA-hEGF plus SAHA compared to 111In-DTPA-hEGF alone (21% ± 0.4% and 19% ± 4.6 vs. 33% ± 2.3 and 32% ± 3.7). SAHA did not affect 111In-DTPA-hEGF nuclear localization. Hypertonic treatment resulted in fewer γH2AX foci per cell after IR and 111In-DTPA-hEGF compared to controls but did not significantly alter clonogenic survival. Conclusions: Chromatin structure affects DNA damage and cell survival after exposure to Auger electron radiation. [Copyright &y& Elsevier]

Collision induced excitation and ionization of atoms and molecules by energetic electrons play an important role in thermonuclear fusion plasmas, and in atmospheric science. In this paper, a brief review of the recent experimental works that have been carried out in the Atomic Physics Laboratory at Banaras Hindu University, Varanasi is presented. Some selected examples of the collision induced processes involved in impact of keV electrons with atoms, molecules and solid surfaces is highlighted. In particular, the results obtained on the multiple- and dissociative ionization of Ar atom and SF molecule, the electron backscattering from a pure thick W target and on the electron bremsstrahlung emission from gaseous Ar and thick solid Ti targets are presented and discussed. [ABSTRACT FROM AUTHOR]

Abstract: Evaluation of the intracellular distribution of radionuclides used for targeted radiotherapy (tRT) is essential for accurate dosimetry. Therefore, a direct and quantitative method for subcellular micro-autoradiography using radiation sensitive polymers (PMMA, UV1116 and AZ40XT) was developed. The electron exposure dose in radio-labelled cells due to Auger and internal conversion (IC) electron emissions of indium (111In), a radionuclide currently used for tRT, was calculated using Monte Carlo (MC) simulation. Electron beam lithography using pre-defined exposure doses was used to calibrate the resist response. The topography of the exposed and developed resists was analysed with atomic force microscopy (AFM) and the resulting pattern depth was related to a specific exposure dose. UV1116 exhibited the best contrast as compared to AZ40XT and PMMA, while AZ40XT exhibited the highest sensitivity at low doses (<10μC/cm2). AFM analysis of the exposure pattern from radio-labelled cells and nuclei in UV1116 revealed a non-uniform distribution of 111In-EGF in the cell and nucleus, consistent with less well-resolved data from confocal microscopy and micro-autoradiography. [Copyright &y& Elsevier]

Abstract: In recent years the use of radionuclides in targeted cancer therapy has increased. In this study we have developed a high-current solid target system and demonstrated that by the use of a typical low-energy medical cyclotron, it is possible to produce tens of GBq''s of many unconventional radionuclides relevant for cancer therapy such as 64Cu and 119Sb locally at the hospitals. [Copyright &y& Elsevier]

Increased expression of epidermal growth factor receptors (EGFR) in breast cancer (BC) is often associated with trastuzumab (Herceptin)-resistant forms of the disease and represents an attractive target for novel therapies. Nimotuzumab is a humanized IgG monoclonal antibody that is in clinical trials for treatment of EGFR-overexpressing malignancies. We show here that nimotuzumab derivatized with benzylisothiocyanate diethylenetriaminepentaacetic acid for labelling with the subcellular range Auger electron-emitter, In and modified with nuclear translocation sequence (NLS) peptides (In-NLS-Bn-DTPA-nimotuzumab) was bound, internalized and transported to the nucleus of EGFR-positive BC cells. Emission of Auger electrons in close proximity to the nucleus caused multiple DNA double-strand breaks which diminished the clonogenic survival (CS) of MDA-MB-468 cells that have high EGFR density (2.4 × 10 receptors/cell) to less than 3 %. In-Bn-DTPA-nimotuzumab without NLS peptide modification was sevenfold less effective for killing MDA-MB-468 cells. In-Bn-DTPA-nimotuzumab with/without NLS peptide modification were equivalently cytotoxic to MDA-MB-231 and TrR1 BC cells that have moderate EGFR density (5.4 × 10 or 4.2 × 10 receptors/cell, respectively) reducing their CS by twofold. MDA-MB-231 cells have intrinsic trastuzumab resistance due to low HER2 density, whereas TrR1 cells have acquired resistance despite HER2 overexpression. Biodistribution and microSPECT/CT imaging revealed that In-NLS-Bn-DTPA-nimotuzumab exhibited more rapid elimination from the blood and lower tumour uptake than In-Bn-DTPA-nimotuzumab. Tumour uptake of the radioimmunoconjugates in mice with MDA-MB-468 xenografts was high (8-16 % injected dose/g) and was blocked by administration of an excess of unlabelled nimotuzumab, demonstrating EGFR specificity. We conclude that In-Bn-DTPA-nimotuzumab with/without NLS peptide modification are promising Auger electron-emitting radioimmunotherapeutic agents for EGFR-positive BC, but In-Bn-DTPA-nimotuzumab may be preferred due to its higher tumour uptake in vivo. [ABSTRACT FROM AUTHOR]

A model of the bremsstrahlung produced by photoelectrons, Auger electrons, and Compton electrons arising in an irradiated specimen is proposed. Calculations have shown that the contribution of the Compton electron bremsstrahlung shows up for monochromatic primary radiation of high-energy photons. For the primary radiation of x-ray tubes, only the bremsstrahlung spectrum of photoelectrons and Auger electrons is significant. The factors affecting the proportions between these components are considered. The bremsstrahlung spectral distribution of the mentioned electrons shows considerable deviations from that predicted by the Kramers theory that are due to the large depth of their occurrence and to the ambiguity of their energy. The region of the spectrum has been determined where the intensity of the electron bremsstrahlung is greater than the intensity of the x-ray tube polychromatic primary radiation scattered by the irradiated object. [ABSTRACT FROM AUTHOR]

Abstract: Purpose: In photon activation therapy (PAT), energy deposition at critical sites within a tumor can be increased by complexing the DNA with higher Z atoms, and provoking the emission of Auger electrons after inducing a photoelectric effect. This in vivo study evaluates the hypothesis using X-rays from palladium-103 seeds to excite the L-edge of platinum (Pt) atoms bound to the DNA of cancerous cells. Methods and Materials: Pt (II) tetrakis(N-methyl-4-pyridyl) porphyrin chloride was used to locate Pt atoms adjacent to the DNA of the KHJJ murine mammary carcinoma; a 2.3-mCi palladium-103 seed was implanted in the tumor. Results: The tumor periphery received subtherapeutic doses. The rate of tumor growth in mice treated with PAT was slower than in mice treated with brachytherapy only. Conclusions: The tumor growth delay for PAT-treated mice is attributed to Auger emission from Pt atoms that produced substantial local damage. However, other co-existing mechanisms cannot be ruled out. [Copyright &y& Elsevier]

Abstract: The use of Auger electrons in radionuclide therapy of cancer is a promising tool for specific tumor cell killing of micrometastases and small tumors. The radioisotope 119Sb has recently been identified as a potent Auger-emitter for therapy. We here present a method for producing this isotope using a low-energy cyclotron. With this method, it will be possible to produce clinically relevant amounts of 119Sb radioactivity with high chemical and radionuclidic purity for cancer therapy. [Copyright &y& Elsevier]

Radioactive 125I emits short-range Auger electrons and represents a human health risk when incorporated in thyroglobulin of the thyroid. Quantitative evaluation of this risk can only be realised if local atomic order about iodine in the thyroid is known. Here, extended X-ray absorption fine structure (EXAFS) has been used to probe the local structure about iodine in pure thyroid hormone, thyroxine. These data are consistent with a model where iodine is bound to a single iodinated carbon ring linked to an oxygen atom, similar to a previously published model for monoiodotyrosine, a major iodinated residue in thyroglobulin. Several structural models for the local environment of iodine from rat, human and sheep have been tested and these data are found to be compatible with a slightly modified environment with respect to that found for thyroxine. The best-fit models include the following three components: (i) iodine covalently bonded to a tyrosine ring, as found for thyroxine; (ii) iodine bonded quasi-covalently to a carbonyl ligand in partially filled (50%) sites; (iii) partially filled sites (50-40%) of carbonyl ligands, with oxygen at van der Waals distances from iodine. Advantages of using Fourier-filtered EXAFS for complex crystal structures are discussed. [ABSTRACT FROM AUTHOR]

Auger electron emitting radionuclides in cancer therapy offer the opportunity to deliver a high radiation dose to the tumor cells with high radiotoxicity while minimizing toxicity to normal tissue. We have in this study identified the Auger emitter 119Sb as a potent nuclide for targeted radionuclide therapy based on theoretical dosimetry calculations at a subcellular scale. From these calculations we have determined the cellular S-values for this therapeutic isotope. Moreover, we have demonstrated the possibility of producing this isotope and also the SPECT-analogue 117Sb for patient-specific dosimetry, by measuring the proton irradiation yields for both isotopes using a low-energy cyclotron. The excellent SPECT imaging properties of the 117Sb radionuclide have been shown by scanning a Jaszczak SPECT Phantom. [ABSTRACT FROM AUTHOR]

Low-energy electrons (10–50 keV) can be effective and specific cytotoxic agents when delivered to the cell surface by antibodies, because their path length in tissue is comparable to a cell diameter. In this study, we have begun to evaluate the therapeutic potential of antibodies (Abs) conjugated to 111In against carcinoma xenografts in nude mice. Abs to EGFr or HER-2 were labeled with 111In to a high specific activity of approximately 1.48 GBq/mg (40 mCi/mg). They were injected into nude mice 5–6 days after inoculation of human carcinoma cells, either A431 or SK-OV-3, and tumor growth was monitored. In preliminary in vitro experiments, we calculated the cumulative decays per cell, estimated the centigray dose delivered to the nucleus, and related this to the fraction surviving. Abs to both antigens provided significant protection in nude mouse xenograft models ( p values ranging from <0.05 to <0.001). Some mice appeared to be cured, but most had delayed tumor growth. The specificity of the effect was demonstrated by testing non-reactive Abs labeled in the same way. The radioactivity was required, because unconjugated Abs had no therapeutic effect. The maximum tolerated dose was required in order for therapy to be effective, but most of the treated mice had no significant weight loss or other overt signs of toxicity. Abs labeled with nuclides emitting low-energy electrons, such as 111In, can be effective therapeutic agents against microscopic s.c. tumors. This strategy should be considered for clinical applications. [ABSTRACT FROM AUTHOR]

We discuss here the energy deposition of solar FUV, EUV and X-ray photons, energetic auroral particles, and pickup ions. Photons and the photoelectrons that they produce may interact with thermospheric neutral species producing dissociation, ionization, excitation, and heating. The interaction of X-rays or keV electrons with atmospheric neutrals may produce core-ionized species, which may decay by the production of characteristic X-rays or Auger electrons. Energetic particles may precipitate into the atmosphere, and their collisions with atmospheric particles also produce ionization, excitation, and heating, and auroral emissions. Auroral energetic particles, like photoelectrons, interact with the atmospheric species through discrete collisions that produce ionization, excitation, and heating of the ambient electron population. Auroral particles are, however, not restricted to the sunlit regions. They originate outside the atmosphere and are more energetic than photoelectrons, especially at magnetized planets. The spectroscopic analysis of auroral emissions is discussed here, along with its relevance to precipitating particle diagnostics. Atmospheres can also be modified by the energy deposited by the incident pickup ions with energies of eV’s to MeV’s; these particles may be of solar wind origin, or from a magnetospheric plasma. When the modeling of the energy deposition of the plasma is calculated, the subsequent modeling of the atmospheric processes, such as chemistry, emission, and the fate of hot recoil particles produced is roughly independent of the exciting radiation. However, calculating the spatial distribution of the energy deposition versus depth into the atmosphere produced by an incident plasma is much more complex than is the calculation of the solar excitation profile. Here, the nature of the energy deposition processes by the incident plasma are described as is the fate of the hot recoil particles produced by exothermic chemistry and by knock-on collisions by the incident ions. [ABSTRACT FROM AUTHOR]

Purpose: To determine the mode of killing of B-lymphoma cell lines by 111In-conjugated antibodies (Ab). Materials and methods: Cells were treated with a range of radiolabeled Ab concentrations to produce a level of killing from 80 - 99.9%, as determined by a long-term proliferation assay. On days 1, 2, 3 and 4, apoptosis was evaluated in individual cells by two assays: (i) Mitochondrial function by JC-1 staining; and (ii) presence of cleaved PARP (poly-ADP-ribose-polymerase) by immunofluorescence. Five cell lines were tested, including two non-Burkitt lines, RL and FSCCL. Results: In preliminary experiments, it was realized that the standard JC-1 assay, which is widely used, does not distinguish between apoptotic and necrotic cells. The JC-1 assay becomes useful if it is combined with a stain for lysed cells, Sytox green, and then is able to distinguish between viable, apoptotic and necrotic cells. Of the 5 cell lines tested, only Ramos had a large population of apoptotic cells detected by the modified JC-1 assay, but all four of the other cell lines showed evidence of cleaved PARP, albeit to markedly different degrees. The caspase inhibitor, Z-VAD (N-benzyloxycarbonyl-Val-Ala-Asp(O-Me) fluoromethyl ketone), significantly inhibited the killing of Daudi cells. Conclusions: Apoptosis was activated in at least four of the five cell lines tested, and participated in the killing of the cells. Staining for cleaved PARP was much more sensitive than the modified JC-1 assay, for most cell lines, probably because it can detect cells that have already lysed, but which died via apoptosis. In addition, the methodological issues discussed may lead to a better understanding of the role of apoptosis in tumor cell cytotoxicity. [ABSTRACT FROM AUTHOR]

Abstract: This work focusses on the production and decay properties of inner-shell vacancies and valence-band excitations induced by swift highly charged ions interacting with amorphous and crystalline Si. High resolution electron spectra have been taken for fast heavy ions at 1.78–5MeV/u as well as for electrons of similar velocity incident on atomically clean Si targets of well defined phase. Various Auger-electron structures are analyzed concerning their width, their intensity and exact peak position. All measured peaks show a small shift towards lower energy when the charge of the projectile is increased. This finding is an indication for a nuclear-track potential inside the ion track. A detailed analysis of the Auger-electron spectra for amorphous Si and crystalline Si(111) 7×7 points to a small but significant phase effect in the short-time dynamics of ion tracks. [Copyright &y& Elsevier]

Abstract: The details of our recently developed coincidence electron spectrometer system with the block diagram and characteristics of the coincidence circuit are presented. As a first application we measured the continuous energy spectra of the scattered electron projectiles producing an L2,3 inner-shell ionization/excitation of argon. The studied energy region was the neighbourhood of the ionization edge, where nearly the total excess energy is taken away by the scattered projectile. Above the edge we identify the peaks of the scattered electrons that produced 2p3/2→4s or 2p3/2→3d excitation. [Copyright &y& Elsevier]

Abstract: We report the results of coincidence measurements of Auger electron–ion pairs generated by 1keV electron beam bombardment of argon where, for the first time, the electron energy resolution is comparable to the natural width of 2p hole. The L–MM Auger spectrum is decomposed into contributions related to the specific final ionic charge states to allowing the study of decay schemes which lead to different structures in the non-coincidence Auger spectra. [Copyright &y& Elsevier]

Abstract: To clarify the contribution of apoptosis to cell death in four human solid tumor cell lines, clonogenic cell survival (indicator of radiosensitivity) and induction of caspase-3 (CASP-3)/caspase-3-like proteases (CASP-3LP) and the production of DNA fragmentation (markers for apoptosis) were studied in RKO, LS174T, MCF7 and TE671 cells exposed to DNA-incorporated Auger-electron-emitting 125I (5-[125I]iodo-2′-deoxyuridine) or γ-radiation. Clonogenic survival was assessed by colony-forming assay, CASP-3/CASP-3LP induction with a fluorogenic substrate and DNA fragmentation by ligation-mediated polymerase chain reaction. For 125I, log dose–survival curves had no shoulder [high-linear-energy-transfer (LET)-like] and decreased exponentially at different rates in various cell lines. Induction of CASP-3/CASP-3LP in radiosensitive RKO and LS174T cells was threefold greater than that in radioresistant TE671 and MCF7 cells. Nucleosomal laddering in 125I-radiosensitive cell lines was dose-dependent, and no laddering was detected in radioresistant lines. For γ-radiation, the survival curve for LS174T cells was monoexponential and that for the other lines exhibited a distinct shoulder (low-LET-like). The most radiosensitive cell line, LS174T, showed the highest induction of CASP-3/CASP-3LP, and the most radioresistant line, TE671, showed the lowest induction. Although DNA laddering was not detectable in TE671 cells, it was observed in other lines, being most prominent in LS174T cells. We conclude that apoptosis initiated by DNA-incorporated 125I is dose-dependent, correlates with cell radiosensitivity and takes place through a CASP-3-mediated pathway, whereas that after γ-irradiation probably occurs via a CASP-3-independent pathway and/or a CASP-3-mediated pathway and does not correlate with cell radiosensitivity. [Copyright &y& Elsevier]

Abstract: The standardization of radionuclides decaying by electron capture can be carried out in LS counters by the CIEMAT/NIST method. The KLM model considers a simplified atomic rearrangement model in which all L- and M-subshells have been averaged. In this paper, instead of considering the 22 rearrangement pathways of the KLM model, we concentrate our analysis on the pathways corresponding to L-Auger electron transition. It is proved that the counting efficiency depends strongly on the energy E(LMM). Therefore, it is important to know the optimum value for E(LMM) and how to obtain it. To this end, the equations of the probabilities and the reduced energies for 3816 atomic rearrangement pathways have been derived. To average the equations, a computer program called MOYEN has been developed. The energy E(LMM) has been computed for 55Fe and 125I from different mean value definitions. [Copyright &y& Elsevier]

Abstract: A program has been set up to calculate the K- and L-Auger electron emissions resulting from the radioactive disintegration process, and to study all the possible emissions in detail. Due to the fact that only a small number of experimental results are available in the measurements of K- and L-Auger electrons, the calculated values obtained in this work were compared with the other calculated values available. Good agreement was found between the values. Some of the results are given as examples. [Copyright &y& Elsevier]

Abstract: Electron spectra were measured at GANIL with different heavy ions (C–Mo) and various charge states q (q =6–39) at fixed projectile velocity v (v =19 atomic units, 9.2MeV/u). A projectile dependent broadening of ion induced KVV Auger electron peaks from carbon targets was observed. From this broadening, one can deduce a mean “electronic temperature” of the heavy ion induced track at the corresponding Auger decay time (10fs). We compare the measured temperature values to the predictions of an inelastic-thermal spike model, which takes into account the electron–phonon coupling. The model underestimates the experimental values, but reproduces the increase with ion charge. [Copyright &y& Elsevier]

The measurements of the K x-ray intensity ratio I(Kß)/I(Ka) for the 16 elements, Ag, Cd, Sn, Sb, Cs, Ba, La, Ce, Pr, Sm, Eu, Gd, Tb, Dy, Ho, and Er, have been done following ionization by 59.5 keV ?-rays from a 241 Am point source. Ratios of emission probabilities Auger electrons and the vacancy transfer coefficients have been extracted in terms of the intensity ratios. The obtained results agree with previously published experimental results. [ABSTRACT FROM AUTHOR]

Abstract: Microdosimetric calculations of 131I have been evaluated for a single cell and for cell clusters. A VsBasic program has been used to calculate stopping power, linear energy transfer, range values and deposited energies per decay for beta particles, Auger and conversion electrons of 131I. The chemical composition of the cell has been taken into account in this model; results were compared with water medium. Besides, total absorbed doses have been calculated for the radionuclides distributed randomly within the cell and clusters. Cross-fire irradiation has been considered for clusters of cells. In this case, absorbed doses per cell within a cluster were found to be significantly higher than absorbed doses per single cell, depending on the cluster size. Results showed that 131I is a promising radionuclide for therapy of tumors from millimeter to centimeter dimensions. [Copyright &y& Elsevier]

Abstract: The distortion effects of the post-collision interaction (PCI) on the Ar LMM Auger electron lineshape for electron and photon impact ionization have been calculated. The calculations were based on the eikonal model of Kuchiev and Sheinerman [Sov. Phys. – Tech. Phys. 32 (1987) 879]. It is shown that the Auger peak asymmetry depends on the emission angle of the Auger electron relative to the primary beam (and the polarization vector of the photon beam). At a given excess energy, defined as the difference between the impact energy and the binding energy, the absolute value of the Auger peak asymmetry is always larger for electron impact ionization than for photoionization. At the same time, the angular dependence of the PCI distortion is stronger for photoionization. In both cases the Auger peak asymmetry has a maximum when the energy of the ejected electron and that of the Auger electron are nearly equal. The calculations are in good agreement with our previous experimental results. [Copyright &y& Elsevier]

Abstract: A brief review is given of studies of surfaces and small particles using electron beam techniques. The principal tools are secondary, Auger and backscattered electrons, either energy-filtered using various types of analyzers, or as a stronger signal with coarser energy filtering. These tools have been deployed in wide-beam surface science instruments, but also increasingly in scanning electron and scanning transmission electron microscopes, especially in ultra-high vacuum instruments capable of analyzing clean surfaces. The different choices that need to be made are illustrated with examples of clean surfaces, thin films and catalyst particles at high spatial resolution. [Copyright &y& Elsevier]

Abstract: Introducing the use of the Factor Analysis method to analyze electron emission spectra we identify different mechanisms for electron emission from clean Al surfaces under bombardment by Ar+ and Li+ ions. The analysis of the energy electron emission distributions and their dependence on incoming ion energy allows separation of the direct contribution of Auger neutralization from that of plasmon de-excitation and cascade electrons due to kinetic emission. Similarly, the analysis shows that, under our experimental conditions, plasmons are excited by fast Al-2p Auger electrons produced in symmetric Al–Al encounters in the atomic collision cascades initiated by the projectiles. [Copyright &y& Elsevier]

Titan has an atmosphere consisting mainly of molecular nitrogen and methane. Solar extreme ultraviolet and X-ray radiation and energetic electrons from Saturn’s magnetosphere interact with the upper atmosphere producing an ionosphere. This paper describes improvements to earlier models of Titan’s ionosphere. In particular, we consider in more detail ion production from solar ionizing radiation for solar zenith angles beyond the terminator, and a higher spectral resolution soft X-ray flux is adopted in the ion production rate calculations. We demonstrate that significant photoionization takes place well beyond the terminator. K-shell photoionization is also included, and this process adds Auger electrons to the ionospheric photoelectron spectrum, which we model using the two-stream transport code. Our calculated photoelectron spectrum shows a distinct Auger electron peak near an energy of 400 eV. [Copyright &y& Elsevier]

In most measurements the line shapes of the Auger peaks ejected after electron impact inner shell ionization are definitely asymmetric ones. Among the physical processes which can distort the originally symmetric peaks, the post-collision interaction (PCI) has the greatest importance. The PCI is the Coulomb interaction of the charged particles in the final state. In non-coincidence experiments, when the scattered and the ejected electrons are not detected, the peak shapes can be obtained by integrating the triple coincidence peak shapes over the non-measured quantities. Calculations were carried out in order to determine the energy- and angular dependence of Auger peak shapes. In addition to the peak shapes some interesting features of the L2,3MM Auger electron spectra of Ar and Kr are shown. [Copyright &y& Elsevier]

We present a set of experimental values for relative cross sections of Auger electron production in carbon foils for projectile charges QP ranging from 6 to 39 and fixed projectile velocity 19.2 atomic units. We deduce the 1s single and double ionisation cross sections and their relative variation with respect to the projectile charge. The cross section saturates for the largest projectile charges. However, the comparison of the experimental data with continuum distorted wave-eikonal initial state (CDW-EIS) and classical trajectory Monte Carlo (CTMC) calculations shows that this saturation effect is not well reproduced by the calculations. We suggest that the observed saturation effect in 1s-shell ionisation could be due to multiple electron effects not included in these models based on independent electron approximation. We have then simulated the backward electron emission yield γB taking into account this strong saturation effect for the 1s shell. We obtained a better agreement for both the emission yield γB and the stopping power. The electron emission simulation gives some insight on the relative contribution of valence and 1s-shell to saturation effects. [Copyright &y& Elsevier]

Auger electron interaction with matter is gaining importance in particular in medical application of radiation. The production probability and energy spectrum is therefore of great importance. A good source of Auger electrons is the 157Gd(n,γ)158Gd reaction. The present article describes calculations of electron levels in Gd atoms and provides missing data of outer electron energy levels. The energy of these electron levels missing in published tables, was found to be in the 23–24 and 6–7 eV energy ranges respectively. The probability of Auger emission was calculated as an interaction of wave function of the initial and final electron states. The wave functions were calculated using the Hartree–Fock–Slater approximation with relativistic correction. The equations were solved using a spherical symmetry potential. The error for inner shell level is less than 10%, it is increased to the order of 10–15% for the outer shells. The width of the Auger process changes from 0.1 to 1.2 eV for atomic number Z from 5 to 70. The fluorescence yield width changes five orders of magnitude in this range. Auger electron emission width from the K shell changes from 10−2 to ∼1 eV with Z changing from 10 to 64, depending on the final state. For the L shell it changes from 0 to 0.25 when it Z changes from 20 to 64. [Copyright &y& Elsevier]

Cancer stem cells (CSCs) are resistant to conventional therapy and present a major clinical challenge since they are responsible for the relapse of many cancers, including non-small cell lung cancer (NSCLC). Hence, future successful therapy should also eradicate CSCs. Auger electrons have demonstrated promising therapeutic potential and can induce DNA damage while sparing surrounding cells. Here, we sort primary patient-derived NSCLC cells based on their expression of the CSC-marker CD44 and investigate the effects of cisplatin and a thymidine analog (deoxyuridine) labeled with an Auger electron emitter ( 125 I). We show that the CD44 + populations are more resistant to cisplatin than the CD44 - populations. Interestingly, incubation with the thymidine analog 5-[ 125 I]iodo-2'-deoxyuridine ([ 125 I]I-UdR) induces equal DNA damage, G2/M cell cycle arrest, and apoptosis in the CD44 - and CD44 + populations. Our results suggest that Auger electron emitters can also eradicate resistant lung cancer CD44 + populations.

Since we are able to bring ionizing radiation in the form of a gas cloud to the respiratory system, we have wondered whether Xenon-133 inhalation could be exploited as a treatment option against Covid-19 respiratory virus infections, and urge colleagues in the scientific research community who have the capability to do so to explore the merits of using Xenon-133 in this way to determine whether its usefulness against the Covid-19 virus is indeed genuine. • Perfusion of the respiratory system with ionizing radiation. • Auger electrons hypothesized impact on the Covid-19 virus. • Free radicals impacting the Covid-19 virus in the respiratory space. [ABSTRACT FROM AUTHOR]

The article focuses on a study by Alex Pronschinske appeared in the periodical "Nature Materials" related to cancer treatment using low-energy electron therapy. Topics include deposition of radioisotope 1 to a gold surface, damage to cancerous cells by the radiation energy of LEEs, and emission of Auger electrons through electronic relaxation during de-excitation of Tellurium (Te). Also it mentions synchronization between chemotherapy and radiotherapy.

Purpose: The β ¯ -emitting terbium-161 also emits conversion and Auger electrons, which are believed to be effective in killing single cancer cells. Terbium-161 was applied with somatostatin receptor (SSTR) agonists that localize in the cytoplasm (DOTATOC) and cellular nucleus (DOTATOC-NLS) or with a SSTR antagonist that localizes at the cell membrane (DOTA-LM3). The aim was to identify the most favorable peptide/terbium-161 combination for the treatment of neuroendocrine neoplasms (NENs)., Methods: The capability of the 161 Tb- and 177 Lu-labeled somatostatin (SST) analogues to reduce viability and survival of SSTR-positive AR42J tumor cells was investigated in vitro. The radiopeptides' tissue distribution profiles were assessed in tumor-bearing mice. The efficacy of terbium-161 compared to lutetium-177 was investigated in therapy studies in mice using DOTATOC or DOTA-LM3, respectively., Results: In vitro, [ 161 Tb]Tb-DOTA-LM3 was 102-fold more potent than [ 177 Lu]Lu-DOTA-LM3; however, 161 Tb-labeled DOTATOC and DOTATOC-NLS were only 4- to fivefold more effective inhibiting tumor cell viability than their 177 Lu-labeled counterparts. This result was confirmed in vivo and demonstrated that [ 161 Tb]Tb-DOTA-LM3 was significantly more effective in delaying tumor growth than [ 177 Lu]Lu-DOTA-LM3, thereby, prolonging survival of the mice. A therapeutic advantage of terbium-161 over lutetium-177 was also manifest when applied with DOTATOC. Since the nuclear localizing sequence (NLS) compromised the in vivo tissue distribution of DOTATOC-NLS, it was not used for therapy., Conclusion: The use of membrane-localizing DOTA-LM3 was beneficial and profited from the short-ranged electrons emitted by terbium-161. Based on these preclinical data, [ 161 Tb]Tb-DOTA-LM3 may outperform the clinically employed [ 177 Lu]Lu-DOTATOC for the treatment of patients with NENs., (© 2021. The Author(s).)