Optical Diagnostics of Iron Oxide Nanoparticle Synthesis in Microwave Oxygen Plasma

Iron oxide nanoparticle synthesis in microwave plasma is studied by optical diagnostics. The arrangement of the plasma reactor results in well-defined reactant mixing, which makes different parts of the reaction zone clearly observable. Besides the reaction zone, digital imaging also reveals the presence of heated nanoparticles. The optical emission spectroscopy is used to determine important plasma parameters

Temporal Evolution of Heavy-Ion Spectra in Solar Energetic Particle Events

Solar energetic particles (SEPs) are released into the heliosphere by solar flares and coronal mass ejections (CMEs). They are mostly protons, with smaller amounts of heavy ions from helium to iron, and lesser amounts of species heavier than iron. The spectra of heavy ions have been previously studied mostly by using the fluence of the particles in an event-integrated spectrum in a small number of spectral snapshots. In this article, we ana- lyze the temporal evolution of the heavy-ion spectra using two large SEP events (27 January 2012 and 7 January 2014) from the Solar TErrestrial Relations Observatory (STEREO) era using Advanced Composition Explorer (ACE) Solar Isotope Spectrometer (SIS) and Ultra Low Energy Isotope Spectrometer (ULEIS), Energetic Particles: Acceleration, Composition and Transport (EPACT) onboard Wind, and the STEREO-A (Ahead) and -B (Behind) Low- Energy Telescope (LET) and Suprathermal Ion Telescope (SIT) instruments, taking a large number of snapshots covering the temporal evolution of the event. We find large differences in the spectra of the ions after the main flux enhancement in terms of the grouping of similar species, but also in terms of the location of the instruments. Although it is somewhat less no- ticeable than in the case of the temporal evolution of protons (Doran and Dalla, Solar Phys. 291, 2071, 2016), we observe a wave-like pattern travelling through the heavy ion spectra from the highest energies to the lowest, creating an “arch” structure that later straightens into a power law after 18 to 24 hours

Multi-instrument studies of heavy ion solar energetic particle transport

In this thesis, an analysis of solar energetic particle (SEP) data from multiple instruments onboard the ACE, SOHO and STEREO spacecraft is presented. The temporal variation and the dependence of heavy ion abundances on solar longitude were studied and quantitatively characterised during SEP events between 2006 and 2016. Ionic abundances vary over the duration of SEP events, e.g. Fe/O often shows a decrease over time. This behaviour was identified as a common characteristic within the data. The time variation of 36 different ionic pairs was studied for a number of SEP events. The fit constant describing time evolution was found to show ordering by the value of S, given e.g. for Fe/O by SFe/O = (M/Q)Fe/(M/Q)O, where M is the mass number and Q the charge number. The ionic ratios with S>1 decreased over time and those with S<1 showed increases, while ratios with a large S decayed at a higher rate. Anomalous behaviour of ratios involving protons was identified in several events. The longitudinal dependence of Fe/O simultaneously observed by multiple spacecraft at 1 AU was studied in 12 SEP events. The event-averaged Fe/O values observed by spacecraft at different longitudes varied within a single event, but this variation was less significant than the event-to-event variation. Although the longitudinal dependence was a complicated one, in some events the Fe/O values were higher at a remote observer. The temporal evolution of heavy ion ratios, which was studied quantitatively for a number of ionic pairs, is consistent with an MQ-dependent interplanetary transport mechanism. The observed longitudinal dependence of event-averaged Fe/O, where higher Fe/O values are observed at a spacecraft that is not well magnetically connected to the source region, cannot be fully explained by the two-class paradigm for classification of SEP events

Time Evolution of Elemental Ratios in Solar Energetic Particle events

Heavy ion ratio abundances in Solar Energetic Particle (SEP) events, e.g. Fe/O, often exhibit decreases over time. Using particle instruments on the ACE, SOHO and STEREO spacecraft, we analysed heavy ion data from 4 SEP events taking place between December 2006 and December 2014. We constructed 36 different ionic pairs and studied their time evolution in each event. We quantified the temporal behaviour of abundant SEP ratios by fitting the data to derive a decay time constant B. We also considered the ratio of ionic mass–to–charge for each pair, the S value given e.g. for Fe/O by SFe/O = (M/Q)Fe/(M/Q)O. We found that the temporal behaviour of SEP ratios is ordered by the value of S: ratios with S > 1 showed decreases over time (i.e. B 0). We plotted B as a function of S and observed a clear monotonic dependence: ratios with a large S decayed at a higher rate. A prominent discontinuity at S = 2.0 (corresponding to He/H) was found in 3 of the 4 events, suggesting anomalous behaviour of protons. The X/H ratios often show an initial increase followed by a decrease, and decay at a slower rate. We discuss possible causes of the observed B versus S trends within current understanding of SEP propagation

UNC13A in amyotrophic lateral sclerosis: from genetic association to therapeutic target

Amyotrophic lateral sclerosis (ALS) is a fatal neurodegenerative disease with limited treatment options and an incompletely understood pathophysiology. Although genomewide association studies (GWAS) have advanced our understanding of the disease, the precise manner in which risk polymorphisms contribute to disease pathogenesis remains unclear. Of relevance, GWAS have shown that a polymorphism (rs12608932) in the UNC13A gene is associated with risk for both ALS and frontotemporal dementia (FTD). Homozygosity for the C-allele at rs12608932 modifies the ALS phenotype, as these patients are more likely to have bulbar-onset disease, cognitive impairment and FTD at baseline as well as shorter survival. UNC13A is expressed in neuronal tissue and is involved in maintaining synaptic active zones, by enabling the priming and docking of synaptic vesicles. In the absence of functional TDP-43, risk variants in UNC13A lead to the inclusion of a cryptic exon in UNC13A messenger RNA, subsequently leading to nonsense mediated decay, with loss of functional protein. Depletion of UNC13A leads to impaired neurotransmission. Recent discoveries have identified UNC13A as a potential target for therapy development in ALS, with a confirmatory trial with lithium carbonate in UNC13A cases now underway and future approaches with antisense oligonucleotides currently under consideration. Considering UNC13A is a potent phenotypic modifier, it may also impact clinical trial outcomes. This present review describes the path from the initial discovery of UNC13A as a risk gene in ALS to the current therapeutic options being explored and how knowledge of its distinct phenotype needs to be taken into account in future trials

UNC13A in amyotrophic lateral sclerosis: From genetic association to therapeutic target

Amyotrophic lateral sclerosis (ALS) is a fatal neurodegenerative disease with limited treatment options and an incompletely understood pathophysiology. Although genomewide association studies (GWAS) have advanced our understanding of the disease, the precise manner in which risk polymorphisms contribute to disease pathogenesis remains unclear. Of relevance, GWAS have shown that a polymorphism (rs12608932) in the UNC13A gene is associated with risk for both ALS and frontotemporal dementia (FTD). Homozygosity for the C-allele at rs12608932 modifies the ALS phenotype, as these patients are more likely to have bulbar-onset disease, cognitive impairment and FTD at baseline as well as shorter survival. UNC13A is expressed in neuronal tissue and is involved in maintaining synaptic active zones, by enabling the priming and docking of synaptic vesicles. In the absence of functional TDP-43, risk variants in UNC13A lead to the inclusion of a cryptic exon in UNC13A messenger RNA, subsequently leading to nonsense mediated decay, with loss of functional protein. Depletion of UNC13A leads to impaired neurotransmission. Recent discoveries have identified UNC13A as a potential target for therapy development in ALS, with a confirmatory trial with lithium carbonate in UNC13A cases now underway and future approaches with antisense oligonucleotides currently under consideration. Considering UNC13A is a potent phenotypic modifier, it may also impact clinical trial outcomes. This present review describes the path from the initial discovery of UNC13A as a risk gene in ALS to the current therapeutic options being explored and how knowledge of its distinct phenotype needs to be taken into account in future trials

Observational evidence for two-component distributions describing solar magnetic bright points

Context. High-resolution observations of the solar photosphere reveal the presence of fine structures, in particular the so-called Magnetic Bright Points (MBPs), which are small-scale features associated with strong magnetic field regions of the order of kilogauss (kG). It is especially relevant to study these magnetic elements, which are extensively detected in all moments during the solar cycle, in order to establish their contribution to the behavior of the solar atmosphere, and ultimately a plausible role within the coronal heating problem. Aims. Characterisation of size and velocity distributions of MBPs in the solar photosphere in two different datasets of quiet Sun images acquired with high-resolution solar instruments i.e. Solar Optical Telescope SOT/Hinode and the High-resolution Fast Imager HiFI/GREGOR, in the G-band (4308 Å). Methods. In order to detect the MBPs, an automatic segmentation and identification algorithm is used. Next, the identified features were tracked to measure their proper motions. Finally, a statistical analysis of hundreds of MBPs is carried out, generating histograms for areas, diameters and horizontal velocities. Results. This work establishes that areas and diameters of MBPs display log-normal distributions that are well-fitted by two different components, whereas the velocity vector components follow Gaussians and the vector magnitude a Rayleigh distribution revealing again for all vector elements a two component composition. Conclusions. The results can be interpreted as due to the presence of two different populations of MBPs in the solar photosphere one likely related to stronger network magnetic flux elements and the other one to weaker intranetwork flux elemens. In particular this work concludes on the effect of the different spatial resolution of GREGOR and Hinode telescopes, affecting detections and average values. © ESO 2022.Part of this work was supported by Austrian FWF – Der Wissenschaftsfonds project number P27800 as well as the German Deutsche Forschungsgemeinschaft, DFG project number Ts 17/2–1. SVD acknowledges support by the Beyond Research Program between University of Graz and Universidad Nacional de Colombia. SJGM acknowledges the support of grants PGC2018-095832-B-I00 (MCIU) and ERC-2017-CoG771310-PI2FA (European Research Council). PG acknowledges the support of the project VEGA 2/0048/20. P.Z. acknowledges support from the Stefan Schwarz fund for postdoctoral researchers awarded by the Slovak Academy of Sciences. This research data leading to the results obtained has been supported by SOLARNET project that has received funding from the European Union’s Horizon 2020 research and innovation programme under grant agreement no 824135. The 1.5-meter GREGOR solar telescope was built by a German consortium under the leadership of the Kiepenheuer Institute for Solar Physics in Freiburg with the Leibniz Institute for Astrophysics Potsdam, the Institute for Astrophysics Göttingen, and the Max Planck Institute for Solar System Research in Göttingen as partners, and with contributions by the Instituto de Astrofísica de Canarias and the Astronomical Institute of the Academy of Sciences of the Czech Republic. The authors are grateful for the possibility to use Hinode data. Hinode is a Japanese mission developed and launched by ISAS/JAXA, collaborating with NAOJ as a domestic partner, NASA and UKSA as international partners. Scientific operation of the Hinode mission is conducted by the Hinode science team organized at ISAS/JAXA. This team mainly consists of scientists from institutes in the partner countries. Support for the post-launch operation is provided by JAXA and NAOJ (Japan), UKSA (UK), NASA, ESA, and NSC (Norway). We would like to express our gratitude to the anonymous referee for all the valuable comments that helped us you improve the presentation of the results and ideas highlighted in this work.With funding from the Spanish government through the Severo Ochoa Centre of Excellence accreditation SEV-2017-0709.Peer reviewe