Publikationer från Uppsala Universitet
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Prediction of decay heat using non-destructive assays
No full textThis research paper introduces a novel approach to predict the decay heat of spent nuclear fuel assemblies (SNFs) using data from non-destructive gamma and neutron measurements, addressing the challenge of ensuring safety in geological repositories. Because calorimetric measurements are time-consuming, it is envisioned that gamma and neutron measurements can be used for decay heat prediction before encapsulation. This paper analyses gamma and neutron data to extract key features, specifically the activities of Cs-137, Eu-154, and the total neutron count rate. A Gaussian process model is then employed to estimate SNF decay heat. The methodology involves training a prediction model on a calibrated simulated dataset designed to mimic real experimental conditions closely. The model is then successfully used to predict the decay heat for unseen experimental data. The results highlight the potential of using gamma and neutron measurements for reliable decay heat prediction. It is shown that the magnitude of the relative deviation obtained is 2–4 %. Furthermore, the study explores the impact of removing certain input features or adjusting their uncertainty levels on the decay heat prediction model precision, in particular for the Eu-154 activity and neutron count rate. This comprehensive methodology paves the way for applying these techniques to a larger experimental scale offering a significant advancement in the safety assessment of SNFs prior to encapsulation and long-term storage
A new system for sample synthesis, preparation and modification combined with in-situ depth profiling using medium energy ions
No full textWe present equipment for sample synthesis, preparation and modification enabling in-situ studies employing medium energy ion beams at the ion implanter facility of the Tandem Laboratory national research infrastructure at Uppsala University. The integral instrumentation enables controlled thin-film synthesis, modification and characterization applicable to study near-surface processes such as thin-film growth, phase transformation, oxidation, annealing, catalysis or ion implantation. We describe the available instrumentation with its specifications and present four demonstrative experiments with a particular focus on the acquired in-situ capabilities addressing 1) Evaporation and thermal alloying of thin films - nickel silicides 2) Reactive magnetron sputtering and controlled oxidization - photochromic YHO 3) Sputtering and low-energy implantation - hydrogen in tungsten and 4) Surface cleaning of sensitive systems - self-supporting silicon membranes
The impact of bisphenol AF on skeletal muscle function and differentiation in vitro
No full textVarious environmental chemicals have been identified as contributors to metabolic diseases. Bisphenol AF (BPAF), a substitute for bisphenol A, has been associated with changes in glucose metabolism and incidence of type 2 diabetes mellitus in humans. However, its mode of action remains unclear. Considering that skeletal muscle is the primary tissue for glucose utilization and the development of insulin resistance, yet largely neglected in toxicological assessments, we investigated the impact of BPAF on skeletal muscle function and differentiation. We examined the effects of BPAF (0.01–10 μM) on glucose uptake, response to insulin, production of reactive oxygen species (ROS), intracellular calcium, and myocyte differentiation, during hyperglycemia, insulin stimulation, and muscle contraction. We used the rat myoblast cell line L6 differentiated into myotubes, and murine primary isolated muscle fibers. In myotubes and contracting adult fibers, BPAF increased mitochondrial ROS. Basal glucose uptake was increased in myotubes while cells' ability to respond to insulin was decreased. Additionally, in developing myotubes, differentiation markers were downregulated with BPAF, along with impaired formation of tube structures. These effects were primarily observed at 10 μM concentration, which is markedly higher than reported human exposure concentrations. The results provide an insight into potential hazards associated with BPAF in terms of metabolic disruption in skeletal muscle. The developed in vitro methods show promise for future usage in assessments of new chemicals and their mixtures
Motor cortex excitability in schizophrenia or depression and its modulation with prefrontal intermittent theta-burst stimulation
No full textAltered cortical excitability is reported in schizophrenia and depression, but findings are inconsistent. Prefrontal repetitive transcranial magnetic stimulation (TMS) induces short-term motor cortex excitability changes in healthy individuals, but its effect in schizophrenia and depression remains unexplored. Prefrontal intermittent theta burst stimulation (iTBS) improves negative symptoms in depression. Cortical excitability is a suggested biomarker for prefrontal iTBS response. We investigated if prefrontal iTBS affects motor cortex excitability in schizophrenia or depression. Secondary aims were to examine motor cortex excitability as a predictor of iTBS effect on negative symptoms in depression and to compare excitability between groups with schizophrenia, depression and healthy controls. TMS indices of cortical excitability − resting motor threshold, short-interval intracortical inhibition, intracortical facilitation and long-interval intracortical inhibition (LICI) − were pooled from previous studies, including an RCT evaluating iTBS for negative symptoms. The dataset comprised 44 patients with schizophrenia, 52 with depression, and 62 healthy controls. Regression models indicated no effect of active versus sham iTBS on any TMS index (all p ≥ .61). No baseline TMS index predicted negative symptom changes after iTBS in depression (all p ≥ .44). Patients with schizophrenia exhibited more pronounced LICI inhibition than the other groups (Mann-Whitney U = 1670, p < .001). LICI correlated with antipsychotic dose (Spearman's ρ = −0.28, p = .04). Prefrontal iTBS does not modify cortical excitability in schizophrenia or depression, nor does cortical excitability predict prefrontal iTBS effects on negative symptoms. The more pronounced LICI inhibition in schizophrenia may be related to the illness or medication
Neuropilin-1 controls vascular permeability through juxtacrine regulation of endothelial adherens junctions
No full textNeuropilin-1 (NRP1) regulates endothelial cell (EC) biology through modulation of vascular endothelial growth factor receptor 2 (VEGFR2) signalling by presenting VEGFA to VEGFR2. How NRP1 impacts VEGFA-mediated vascular hyperpermeability has however remained unresolved, described as exerting either a positive or a passive function. Using EC-specific Nrp1 knock-out mice, we discover that EC-expressed NRP1 exerts an organotypic role. In the ear skin, VEGFA/VEGFR2-mediated vascular leakage was increased following loss of EC NRP1, implicating NRP1 in negative regulation of VEGFR2 signalling. In contrast, in the back skin and trachea, loss of EC NRP1 decreased vascular leakage. In accordance, phosphorylation of vascular endothelial (VE)-cadherin was increased in the ear skin but suppressed in the back skin of Nrp1 iECKO mice. NRP1 expressed on perivascular cells has been shown to impact VEGF-mediated VEGFR2 signalling. Importantly, expression of NRP1 on perivascular cells was more abundant in the ear skin than in the back skin. Global loss of NRP1 resulted in suppressed VEGFA-induced vascular leakage in the ear skin, implicating perivascular NRP1 as a juxtacrine co-receptor of VEGFA in this compartment. Altogether, we demonstrate that perivascular NRP1 is an active participant in EC VEGFA/VEGFR2 signalling and acts as an organotypic modifier of EC biology.Correction in: Angiogenesis, vol. 28, article no. 16DOI: 10.1007/s10456-024-09968-y</p
State-of-the-art electron beams for compact tools of ultrafast science
No full textWe review state-of-the-art electron beams for single-shot megaelectronvolt ultrafast electron diffraction (MeVUED) and compact light sources. Our primary focus is on sub-100 femtosecond electron bunches in the 2-30 MeV energy range. We demonstrate that our new and recent simulation results permit significantly improved bunch parameters for these applications
Numerical simulation of the generalized modified Benjamin-Bona-Mahony equation using SBP-SAT in time
No full textIn this paper we present high-order accurate finite difference approximations for solving the generalized modified Benjamin-Bona-Mahony (BBM) equation, a non-linear soliton model. The spatial discretization uses high-order accurate summation-by-parts (SBP) finite difference operators combined with both weak and strong enforcement of boundary conditions. For time integration we compare the explicit RK4 method against an implicit SBP time integrator. These time-marching methods are evaluated and compared in terms of accuracy and efficiency. It is shown that the implicit SBP time-integrator is more efficient than the explicit RK4 method for non-linear soliton models
Observation of bi-directional global Alfvén eigenmodes in the MAST-U tokamak
No full textThe first observations and classification of deuterium beam-driven sub-cyclotron frequency range Alfvén eigenmodes (AEs) are presented for the MAST-Upgrade tokamak. Sets of observed eigenmodes are separated in frequency by approximately 200 kHz. We observe a lower frequency separation of ∼10 kHz within each set, and the toroidal mode number n increases with frequency sequentially. The ∼200 kHz step between the sets coincides with the interval between successive curves of the Shear Alfvén continuum according to linear ideal MHD modeling. The sub-cyclotron frequency AEs can be identified as the global AEs (GAEs) localized at the continuum extrema regions. Each set contains the same range of n. These observations are consistent with our GAE modeling. In low plasma current (Ip) discharges, we observe only GAEs propagating counter to the plasma current and the beam direction. These GAEs are located near the magnetic axis. We observe counter and co-propagating GAEs simultaneously in higher Ip discharges. The co-propagating GAEs occur because of the formation of second continuum minima. Very flat safety factor profiles in higher Ip MAST-U discharges give rise to these minima. They are located at around half of the plasma radius. The GAEs have properties that are very different to those of compressional AEs previously reported for the MAST tokamak with low magnetic fields (Sharapov et al 2014 Phys. Plasmas 21 082501) before the upgrade
Solvability of the Lp Dirichlet problem for the heat equation is equivalent to parabolic uniform rectifiability in the case of a parabolic Lipschitz graph
No full textWe prove that if a parabolic Lipschitz (i.e., Lip(1,1/2)) graph domain has the property that its caloric measure is parabolic A∞ with respect to surface measure (which property is in turn equivalent to Lp solvability of the Dirichlet problem for some finite p), then the function defining the graph has a half-order time derivative in the space of (parabolic) bounded mean oscillation. Equivalently, we prove that the A∞ property of caloric measure implies, in this case, that the boundary is parabolic uniformly rectifiable. Consequently, by combining our result with the work of Lewis and Murray we resolve a long standing open problem in the field by characterizing those parabolic Lipschitz graph domains for which one has Lp solvability (for some p<∞) of the Dirichlet problem for the heat equation. The key idea of our proof is to view the level sets of the Green function as extensions of the original boundary graph for which we can prove (local) square function estimates of Littlewood-Paley type
Intravital Imaging of Disease Mechanisms in a Mouse Model of CCM Skin Lesions-Brief Report
No full textBACKGROUND: Cerebral cavernous malformation (CCM) is a disease characterized by vascular malformations that primarily develop in the brain. These malformations are prone to leak, and their rupture or thrombotic closure can cause life-threatening hemorrhages and strokes. Mouse models have been instrumental to study the disease, but most cause premature lethality, precluding the investigation of disease mechanisms through intravital microscopy. Current mouse models also do not recapitulate human CCM skin lesions. METHODS: Endothelial-specific deletion of Ccm3 via systemic tamoxifen application at postnatal day 4 or 5 prolongs survival and induces vascular malformations in the mouse brain and ear skin. CCM skin lesions can also be induced by topical tamoxifen administration directly to the ear. The thin, flat morphology of the ear skin is ideal for intravital microscopy. Dextran dyes and platelet markers allow to study blood flow and blood clot formation in living animals, in real time. RESULTS: We report that human CCM skin lesions can be recapitulated in a mouse model and that skin lesions share hallmarks of CCM brain lesions. Intravital imaging reveals that CCM skin lesions are slow-flow malformations prone to thrombus formation. CONCLUSIONS: Intravital imaging of CCM skin lesions expands the toolkit of CCM research and allows longitudinal studies of lesion growth