Radiation Effects

Radiation tests on CMOS analog switches were carried out in order to select the most tolerant device for future use in the cryogenic system of the CERN large hadron collider. After irradiation, the devices showed some interesting changes related to the power supplies: an increase in the lowest supply voltage capable of biasing correctly the devices; some devices cannot work with TTL logic levels. In addition, hysteresis phenomena appear.

We present a compendium of optocoupler radiation test data including data on neutron, proton and heavy ion displacement damage (DD), single event transients (SET) and degradation due to total ionizing dose (TID). Proton data includes ionizing and non-ionizing damage mechanisms.

Turkish coal is generally poor quality and the levels of chemical and radiological toxic trace elements in it are higher with respect to mean values of activity concentrations given in United Nations Scientific Committee on the Effects of Atomic Radiation (UNSCEAR) Report. The main pathways through which the population living around soal-fired power plant (CFPP) is exposed to natural radionuclides are external and internal (ingestion and inhalation) dose and fly ash particles are the major component of the risk. It is estimated that the people working or living near the CFPP in Turkey receive a dose in between 0.1 mSv to 1 mSv extra from CFPP because nearly all the region of Turkey uranium (U) and thorium (Th) content in the coal are higher than 5 ppm to 7 ppm and around 25 ppm to 40 ppm respectively. Continuous monitoring is essential to determine occupational exposure levels in all stages of the coal fuel-cycle and proper measures should be taken to prevent direct contact of the ash pile with the top soil and local drainage systems.

Proxima Centauri b provides an unprecedented opportunity to understand the evolution and nature of terrestrial planets orbiting M dwarfs. Although Proxima Cen b orbits within its star's habitable zone, multiple plausible evolutionary paths could have generated different environments that may or may not be habitable. Here, we use 1-D coupled climate-photochemical models to generate self-consistent atmospheres for several evolutionary scenarios, including high-O, high-CO, and more Earth-like atmospheres, with both oxic and anoxic compositions. We show that these modeled environments can be habitable or uninhabitable at Proxima Cen b's position in the habitable zone. We use radiative transfer models to generate synthetic spectra and thermal phase curves for these simulated environments, and use instrument models to explore our ability to discriminate between possible planetary states. These results are applicable not only to Proxima Cen b but to other terrestrial planets orbiti...

Peter Karamoskos is a Nuclear Radiologist; Treasurer of the Medical Association for the Prevention of War; Treasurer of the International Campaign for the Abolition of Nuclear Weapons; and public representative of the Radiation Health Committee, Australian Radiation Protection and Nuclear Safety Agency (for informational purposes and does not represent an endorsement by ARPANSA of this document). NUCLEAR POWER AND PUBLIC HEALTH BRIEFING PAPER 22

With the choice of an optimum thickness range, silicon nitride passivation (Si3N4) on
AlGaN\GaN heterojunction devices can not only improve device performance but also radiation
harden the device while preserving the reliability and performance. In this study, the effects of
passivation layer thickness were investigated by using various thicknesses (0, 20, 50 and 120
nanometers) on bare epilayer AlGaN\GaN structures which were then measured before and
immediately after 1.0 MeV electron irradiation at fluences from 5 x 1015 cm-2 to 1016 cm-2. The
irradiation was applied in order to increase the electron trapping at the interface, thus providing
an enhanced interface quality. It has been shown previously that this irradiation produces point
defects and creates acceptors [1,2]. Hall measurements were used pre- and post-irradiation to
observe changes in carrier concentration and mobility as a function of fluence, energy, and total
dose. Hall carrier density data indicates the surface states are donors. Most importantly, these
measurements indicate preservation of mobility and conductivity within the optimal range of
Si3N4 thickness. This optimal range was found to be 50 to 120 nm.

Silicon nitride passivation on AlGaN\GaN heterojunction devices can improve performance by reducing electron traps at the surface. In this study, the effects of passivation layer thickness was investigated at various thicknesses (0, 20, 50 and 120 nm) on bare epilayer AlGaN\GaN structures and then measured before and immediately after 1.0 MeV electron irradiation at fluences of 1016 cm-2 . The irradiation was applied in order to increase the electron trapping at the interface, thus providing an enhanced measurement of the interface quality .Additionally, pre- and post-irradiation photoluminescence spectroscopy was used to reveal near-band-edge shallow electron donors, neutral donor bound excitons (D0  XA ) as well as deep center yellow/blue bands as the interface . Hall system measurements were used pre- and post-irradiation to observe changes in carrier concentration and mobility as a function of fluence, energy, and total dose. These measurements indicated preservation of mobility as a function of Si3N4(SiN) thickness

ME1 C9, a cloned line of mouse embryo cells, transformed by SV40 in vitro, and its more malignant progeny, ME1 C9-V15, derived from a tumor of the 15th consecutive passage of ME1 C9 in vivo, were compared as regards immunogenicity and immunosensitivity in syngeneic CBA mice. A threshold zone of immunization with ME1 C9 and ME1 C9-V15 cells in the range of 103-105 irradiated cells was indicated, after which the immunized animals were 1,000 times more resistant. There was no significant difference in immunizing potential between ME1 C9 and ME1 C9-V15 cells at any dose level. A heterologous line of SV40-transformed rat cells was significantly less immunogenic than the syngeneic cells. The growth of ME1 C9-V15 cells could be enhanced after immunization with spontaneously transformed ME3 cells or with a small dose of ME1 C9 cells. The immunosensitivity of the ME1 C9 and ME1 C9-V15 cells was measured as a sensitivity index in uniformly immunized animals. Both lines appeared immunosensitive if the animals were sufficiently immunized. The less malignant cells, ME1 C9, appeared more immunosensitive than the more malignant ME1 C9-V15 cells in seven out of nine experiments, but only once was the difference between the lines significant. The interpretation of differences of sensitivity indices is discussed, and a possible role of blocking factors is considered.

Over the past 20 or so years experimental evidence, which questions the fundamentals of some 50 years standing, of both biology and radiobiology has accrued. In order to accommodate this new evidence within a framework that encompasses existing knowledge, attention has to be paid to the organisational or epigenetic, features of the cell. In recent years the high dimensional dynamic attractor has emerged as a potential organisational or regulatory agent that represents phenotype. It is argued here that its limited robustness provides a modus operandi to account for stress induced genomic instability.When radiation deposition events act to overcome the robustness of a normal or “home” attractor in the cell of an established species and cause a transition to a variant attractor or phenotype, the consequences are unrelated to any specific molecular damage to the genomic DNA. Rather they correspond to the loss of evolutionarily acquired stability (genotypic replicative integrity) and robustness. Such processes are termed type B events and give rise to a separate category of effects and risk to those associated with the conventional effects of radiation, type A effects. How type B risks might be assessed is discussed.

Latency is associated with the time lag it takes for the health effects resulting from exposure to ionising radiation to show up. However, the term latency can also be applied to the time it takes for a policy to be implemented. This length of time has been suggested as broadly 40-year process. Given that radioactivity was identified and named in 1896, three paradigms are identified and examined from 1896 to 2016 and the criteria for a 4th paradigm suggested for the period 2017-2056. The review examines the changes that have taken place in scientific understanding and in public trust, a few key developments and the associated establishment of the related organisational infrastructure designed to collate and assess the evidence.

Le sulfocyanate d'ammonium et l'aldéhyde formique, formés probablement au cours de l'évolution géochimique, fournissent les structures ressemblant à des cellules. La formation des ces structures, sous des conditions variables de concentration, est catalysée par les irradations UV. Ces formes protocellulaires expulsent leurs contenus vacuolaires et absorbent des matières colorantes. La transition de l'évolution géochimique aux protocellules semble être une étape admissible selon le résultat de nos expériences.

The major kinetoplast DNA complement of Leishmania tarentolae promastigotes has been isolated as a single sheet of interconnected molecules on the basis of its relative stability to shear forces and its high sedimentation coefficient. Two successive differential centrifugations were sufficient to recover 50 ± 10% of the total kinetoplast DNA free of nuclear DNA contamination. We use the term “network” to describe this unusual type of DNA configuration.Leishmania networks have a molecular weight of ∼1010 daltons and an S20,W in neutral sucrose gradients of 1729 7plusmn; 189 [n = 19] and exhibit an extremely low specific viscosity due to the compactness of packing of the DNA. The networks were visualized in the electron microscope, and in the light microscope either by fluorescence in solution after staining with acridine orange or in dried smears after staining with Giemsa.Purified networks from stationary phase cells banded in the position characteristic of closed monomeric minicircles in ethidum bromide-CsCl equilibrium gradients, and were stable in alkaline sucrose. Treatment of the closed networks with RNase and pronase had no effect on the ethidium bromide-CsCl banding pattern. However, treatment of closed networks with DNase I or II, X-irradiation or γ-irradiation changed the banding pattern by introducing single strand and double strand breaks, yielding an upper band and in some cases a intermediate band.