Annealing of swift heavy ion tracks in amorphous silicon dioxide

The annealing kinetics of the high energy ion damage in amorphous silicon dioxide (a-SiO2) are still not well understood, despite the material's widespread application in material science, physics, geology, and biology. This study investigates how annealing temperature, duration, and ambient environment affect the recovery of irradiation damage produced along the trajectory of swift heavy ions in a-SiO2. The track-annealing kinetics and the changing ion track morphology were investigated using synchrotron-based small-angle X-ray scattering (SAXS) and etching methods. We found that track annealing proceeds quicker near the sample surface demonstrated by a changing track etch rate as a function of depth. Measurements of ion tracks using SAXS show only small changes in the radial density distribution profile of the ion tracks. Activation energy of the annealing process at different sample depths was determined and the effect of the capping layer during the annealing process was also studied. Combination of oxygen diffusion and stress relaxation may contribute to the observed behaviour of preferential and anisotropic healing of the ion track. The results add to the fundamental understanding of ion track damage recovery and may have direct implications for materials for radioactive waste storage and solid state nanopores

Tracking gypsophily across the phylogeny: 3 study cases

To gain an evolutionary understanding of plant gypsophily, is essential to incorporate phylogeny in the analyses. Here we present an overview of three different approaches that we are currently undertaking to tackle this issue. (I) we have selected 5 Iberian genera with gysophite or gypsovag species in which a fairly complete and reliable phylogeny is published (Ononis, Helianthemum, Chaenorrhinum, Reseda and Teucrium). In each of these 5 lineages we plan to explore the events of gypsophily and to evaluate the existence of preadaptations along the clades in terms of ionome. (II) Within the Ononis tridentata-fruticosa-rotundifolia clade, we intend to carry out Hyb-Seq taking the leaf and soil chemical composition into account. Among other biogegraphic and phylogenetic inferences, we are particularly interested on the comparison of the ionome of O. fruticosa populations growing in and out gypsum. (III)We plan to reconstruct the phylogeny of the genus Frankenia based on HybSeq, which comprises a relevant amount of halophyte, gypso-halophyte and gypsum species, particularly in Australia. This worldwide distributed genus is crucial for the understanding of chemical adaptations of gypso-halophytes, a poorly described functional group, but requires a taxonomic and phylogenetic clarification before further analysis. Approaches II and III will use the Angiosperms-353 kit (myBaits), which will allow integrating the results in further studies beyond our current particular purposes

Unravelling the secrets of the resistance of GaN to strongly ionising radiation

GaN is the most promising upgrade to the traditional Si-based radiation-hard technologies. However, the underlying mechanisms driving its resistance are unclear, especially for strongly ionising radiation. Here, we use swift heavy ions to show that a strong recrystallisation effect induced by the ions is the key mechanism behind the observed resistance. We use atomistic simulations to examine and predict the damage evolution. These show that the recrystallisation lowers the expected damage levels significantly and has strong implications when studying high fluences for which numerous overlaps occur. Moreover, the simulations reveal structures such as point and extended defects, density gradients and voids with excellent agreement between simulation and experiment. We expect that the developed modelling scheme will contribute to improving the design and test of future radiation-resistant GaN-based devices. Gallium nitride is a wide bandgap semiconductor which is generally expected to replace some silicon-based technologies, despite some of its properties still requiring further investigation. Here, using a two-temperature model coupled to molecular dynamics simulations, the authors investigate and predict the effects of strongly ionising radiation in gallium nitride, revealing the mechanism behind its unusual resistance to radiation.Peer reviewe

Morphology of ion irradiation induced nano-porous structures in Ge and Si1-xGex alloys

Crystalline Ge and Si1−xGex alloys (x = 0.83, 0.77) of (100) orientation were implanted with 140 keV Ge− ions at fluences between 5 × 1015 to 3 × 1017 ions/cm2, and at temperatures between 23 °C and 200 °C. The energy deposition of the ions leads to the formation of porous structures consisting of columnar pores separated by narrow sidewalls. Their sizes were characterized with transmission electron microscopy, scanning electron microscopy, and small angle x-ray scattering. We show that the pore radius does not depend significantly on the ion fluence above 5 × 1015 ions/cm2, i.e., when the pores have already developed, yet the pore depth increases from 31 to 516 nm with increasing fluence. The sidewall thickness increases slightly with increasing Si content, while both the pore radius and the sidewall thickness increase at elevated implantation temperaturesWe acknowledge access to NCRIS facilities (ANFF and the Heavy Ion Accelerator Capability) and the Center for Advanced Microscopy, both at the Australian National University. P.K. and M.C.R. thank the Australian Research Council, and Imam Abdulrahman Bin Faisal University for financial support. This research was undertaken on the SAXS/WAXS beamline at the Australian Synchrotron

Unravelling the secrets of the resistance of GaN to strongly ionising radiation

info:eu-repo/semantics/publishedVersio

Effect of annealing high-dose heavy-ion irradiated high-temperature superconductor wires

Heavy-ion irradiation of high-temperature superconducting thin films has long been known to generate damage tracks of amorphized material that are of close-to-ideal dimension to effectively contribute to pinning of magnetic flux lines and thereby enhance the in-field critical current. At the same time, though, the presence of these tracks reduces the superconducting volume fraction available to transport current while the irradiation process itself generates oxygen depletion and disorder in the remaining superconducting material. We have irradiated commercially available superconducting coated conductors consisting of a thick film of (Y,Dy)Ba2Cu3O7 deposited on a buffered metal tape substrate in a continuous reel-to-reel process. Irradiation was by 185 MeV 197Au ions. A high fluence of 3 × 1011 ions/cm2 was chosen to emphasize the detrimental effects. The critical current was reduced following this irradiation, but annealing at relatively low temperatures of 200 °C and 400 °C substantially restore the critical current of the irradiated material. At high fields and high temperatures there is a net benefit of critical current compared to the untreated materialThe authors wish to thank M. Rupich of American Superconductor for supplying the coated conductor material for our irradiation trials and for useful discussions. PK and MCR thank the Australian Research Council for financial support

Orientation dependence of swift heavy ion track formation in potassium titanyl phosphate

Potassium titanyl phosphate crystals in both x-cut and z-cut were irradiated with 185 MeV Au ions. The morphology of the resulting ion tracks was investigated using small angle x-ray scattering (SAXS), transmission electron microscopy (TEM), and atomic force microscopy (AFM). SAXS measurements indicate the presence of cylindrical ion tracks with abrupt boundaries and a density contrast of 1 ± 0.5% compared to the surrounding matrix, consistent with amorphous tracks. The track radius depends on the crystalline orientation, with 6.0 ± 0.1 nm measured for ion tracks along the x-axis and 6.3 ± 0.1 nm for those along the z-axis. TEM images in both cross-section and plan-view show amorphous ion tracks with radii comparable to those determined from SAXS analysis. The protruding hillocks covering the sample surface detected by AFM are consistent with a lower density of the amorphous material within the ion tracks compared to the surrounding matrix. Simulations using an inelastic thermal-spike model indicate that differences in the thermal conductivity along the z- and x-axis can partially explain the different track radii along these directions.The authors acknowledge the National Nature Science Foundation of China (Grant No. 51272135) and the Australian Research Council for financial support and thank the staff of the ANU Heavy Ion Accelerator Facility for technical support. Part of this research was undertaken on the SAXS/WAXS beamline at the Australian Synchrotron, Victoria, Australia

Nuevas terapias dirigidas para el tratamiento del cáncer

El cáncer es el término que se utiliza para englobar un conjunto de enfermedades que se caracterizan por el crecimiento descontrolado de células alteradas molecularmente por mutaciones o modificaciones epigenéticas.En la presente revisión describimos algunas terapias dirigidas que se están utilizando actualmente en clínic

Viruses and Mycoplasma pneumoniae are the main etiological agents of community-acquired pneumonia in hospitalized pediatric patients in Spain

[Objectives]: To describe the etiology of community-acquired pneumonia (CAP) in hospitalized children in Spain and analyze the predictors of the etiology.[Hypothesis]: The different etiological groups of pediatric CAP are associated with different clinical, radiographic, and analytical data.[Design]: Observational, multicenter, and prospective study.[Patient selection]: This study included children aged 1 month to 17 years with CAP, who were hospitalized between April 2012 and May 2019.[Methods]: An extensive microbiological workup was performed. The clinical, radiographic, and analytical parameters were analyzed for three etiological groups.[Results]: Among the 495 children included, at least one causative pathogen was identified in 262 (52.9%): pathogenic viruses in 155/262 (59.2%); atypical bacteria (AB), mainly Mycoplasma pneumonia, in 84/262 (32.1%); and typical bacteria (TyB) in 40/262 (15.3%). Consolidation was observed in 89/138 (64.5%) patients with viral CAP, 74/84 (88.1%) with CAP caused by AB, and 40/40 (100%) with CAP caused by TyB. Para-pneumonic pleural effusion (PPE) was observed in 112/495 (22.6%) patients, of which 61/112 (54.5%) presented a likely causative pathogen: viruses in 12/61 (19.7%); AB in 23/61 (37.7%); and TyB in 26/61 (42.6%). Viral etiology was significantly frequent in young patients and in those with low oxygen saturation, wheezing, no consolidation, and high lymphocyte counts. CAP patients with AB as the etiological agent had a significantly longer and less serious course as compared to those with other causative pathogens.[Conclusions]: Viruses and M. pneumoniae are the main causes of pediatric CAP in Spain. Wheezing, young age, and no consolidation on radiographs are indicative of viral etiology. Viruses and AB can also cause PPE. Since only a few cases can be directly attributed to TyB, the indications for antibiotics must be carefully considered in each patient.Instituto de Investigación Hospital 12 de Octubre (i+12), Grant/Award Number: AY191212‐1; Instituto de Salud Carlos III (Ministry of Economy, Industry and Competitiveness) and co‐funded by the European Regional Development Funds, Grant/Award Number: Project PI17/01458; Instituto Ramón y Cajal de Investigación Sanitaria (IRYCIS), Grant/Award Number: PCAPE 2011_0025 Register 320/11; Research Project of Universidad Europea de Madrid, Grant/Award Number: 2017/UEM03Peer reviewe