Enhancement of low-energy electron emission in 2D radioactive films

High-energy radiation has been used for decades; however, the role of low-energy electrons created during irradiation has only recently begun to be appreciated. Low-energy electrons are the most important component of radiation damage in biological environments because they have subcellular ranges, interact destructively with chemical bonds, and are the most abundant product of ionizing particles in tissue. However, methods for generating them locally without external stimulation do not exist. Here, we synthesize one-atom-thick films of the radioactive isotope (125)I on gold that are stable under ambient conditions. Scanning tunnelling microscopy, supported by electronic structure simulations, allows us to directly observe nuclear transmutation of individual (125)I atoms into (125)Te, and explain the surprising stability of the 2D film as it underwent radioactive decay. The metal interface geometry induces a 600% amplification of low-energy electron emission (<10 eV; ref. ) compared with atomic (125)I. This enhancement of biologically active low-energy electrons might offer a new direction for highly targeted nanoparticle therapies

Atomic-Scale Picture of the Composition, Decay, and Oxidation of Two-Dimensional Radioactive Films

Two-dimensional radioactive (125)I monolayers are a recent development that combines the fields of radiochemistry and nanoscience. These Au-supported monolayers show great promise for understanding the local interaction of radiation with 2D molecular layers, offer different directions for surface patterning, and enhance the emission of chemically and biologically relevant low-energy electrons. However, the elemental composition of these monolayers is in constant flux due to the nuclear transmutation of (125)I to (125)Te, and their precise composition and stability under ambient conditions has yet to be elucidated. Unlike I, which is stable and unreactive when bound to Au, the newly formed Te atoms would be expected to be more reactive. We have used electron emission and X-ray photoelectron spectroscopy (XPS) to quantify the emitted electron energies and to track the film composition in vacuum and the effect of exposure to ambient conditions. Our results reveal that the Auger electrons emitted during the ultrafast radioactive decay process have a kinetic energy corresponding to neutral Te. By combining XPS and scanning tunneling microscopy experiments with density functional theory, we are able to identify the reaction of newly formed Te to TeO2 and its subsequent dimerization. The fact that the Te2O4 units stay intact during major lateral rearrangement of the monolayer illustrates their stability. These results provide an atomic-scale picture of the composition and mobility of surface species in a radioactive monolayer as well as an understanding of the stability of the films under ambient conditions, which is a critical aspect in their future applications

Bead-like structures and self-assembled monolayers from 2,6-dipyrazolylpyridines and their iron(II) complexes

Drop-casting acetone solutions of [Fe(bpp)2][BF4]2 (bpp = 2,6-di[pyrazol-1-yl]pyridine) onto a HOPG surface affords unusual chain-of-beads nanostructures. The beads in each chain are similar in size, with diameters in the range of 2–6 nm and heights of up to 10 Å, which is consistent with them containing between 10–50 molecules of the compound. The beads can be classified into two types, which exhibit different conduction regimes by current-imaging tunnelling spectroscopy (CITS) which appear to correlate with their positions in the chains, and may correspond to molecules containing high-spin and low-spin iron centres. Similarly drop-cast films of the complex on a gold surface contain the intact [Fe(bpp)2][BF4]2 compound by XPS. 4-Mercapto-2,6-di[pyrazol-1-yl]pyridine undergoes substantial decomposition when deposited on gold, forming elemental sulfur, but 4-(N-thiomorpholinyl)-2,6-di[pyrazol-1-yl]pyridine successfully forms SAMs on a gold surface by XPS and ellipsometry

Sport and social media research: A review

The emergence of social media has profoundly impacted the delivery and consumption of sport. In the current review we analysed the existing body of knowledge of social media in the field of sport management from a service-dominant logic perspective, with an emphasis on relationship marketing. We reviewed 70 journal articles published in English-language sport management journals, which investigated new media technologies facilitating interactivity and co-creation that allow for the development and sharing of user-generated content among and between brands and individuals (i.e., social media). Three categories of social media research were identified: strategic, operational, and user-focussed. The findings of the review demonstrate that social media research in sport management aligns with service-dominant logic and illustrates the role of social media in cultivating relationships among and between brands and individuals. Interaction and engagement play a crucial role in cultivating these relationships. Discussion of each category, opportunities for future research as well as suggestions for theoretical approaches, research design and context are advanced

An analysis of competencies taught in the Chippewa Valley Technical College Dental Assisting Degree Program

Includes bibliographical references

Physiological Characterization of a Novel Photoferrotroph Utilizing Alternative Electron Donors

Photoferrotrophs are photosynthetic bacteria that gain energy from light and utilize Fe(II) as an electron donor, without oxygen, to synthesize organic carbon (i.e. primary productivity). Photoferrotrophs are thought to evolutionarily predate oxygen-producing cyanobacteria and therefore have been important primary producers in Archean oceans. Additionally, ferric iron minerals deposited by photoferrotrophs may have contributed to large iron ore deposits found around the world which are known as Banded Iron Formations (BIF). A bacterium capable of anoxygenic photosynthesis using Fe(II) metabolism was isolated from iron-rich Brownie Lake in Minneapolis, Minnesota. Although photoferrotrophs are capable of utilizing Fe(II), it is not necessarily the only electron donor that they are able to utilize. To better understand the physiological capabilities of the Brownie Lake isolate, growth experiments were conducted with Fe(II) and alternative electron donors including acetate, sulfide, thiosulfate, manganese, and hydrogen gas. In addition to growth measured when utilizing Fe(II), growth was observed when using all alternative electron donors except manganese. The average Fe(II) oxidation rate was 403 μmol L-1 day-1. This rate is commensurate with oxidation rates recorded in studies of other photoferrotrophs and speculated oxidation rates of photoferrotrophs in Archean oceans; this supports the claim that photoferrotrophs contributed to BIF deposition.</p

Physiological Characterization of a Novel Photoferrotroph Utilizing Alternative Electron Donors

Photoferrotrophs are photosynthetic bacteria that gain energy from light and utilize Fe(II) as an electron donor, without oxygen, to synthesize organic carbon (i.e. primary productivity). Photoferrotrophs are thought to evolutionarily predate oxygen-producing cyanobacteria and therefore have been important primary producers in Archean oceans. Additionally, ferric iron minerals deposited by photoferrotrophs may have contributed to large iron ore deposits found around the world which are known as Banded Iron Formations (BIF). A bacterium capable of anoxygenic photosynthesis using Fe(II) metabolism was isolated from iron-rich Brownie Lake in Minneapolis, Minnesota. Although photoferrotrophs are capable of utilizing Fe(II), it is not necessarily the only electron donor that they are able to utilize. To better understand the physiological capabilities of the Brownie Lake isolate, growth experiments were conducted with Fe(II) and alternative electron donors including acetate, sulfide, thiosulfate, manganese, and hydrogen gas. In addition to growth measured when utilizing Fe(II), growth was observed when using all alternative electron donors except manganese. The average Fe(II) oxidation rate was 403 μmol L-1 day-1. This rate is commensurate with oxidation rates recorded in studies of other photoferrotrophs and speculated oxidation rates of photoferrotrophs in Archean oceans; this supports the claim that photoferrotrophs contributed to BIF deposition