Fakultet for naturvitenskap og teknologi: Recent submissions
Now showing items 1081-1100 of 5315
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Analyzing Mitochondrial Morphology Through Simulation Supervised Learning
(Journal article; Tidsskriftartikkel; Peer reviewed, 2023-03-03)The quantitative analysis of subcellular organelles such as mitochondria in cell fluorescence microscopy images is a demanding task because of the inherent challenges in the segmentation of these small and morphologically diverse structures. In this article, we demonstrate the use of a machine learning-aided segmentation and analysis pipeline for the quantification of mitochondrial morphology in ... -
Accurate Relativistic Real-Time Time-Dependent Density Functional Theory for Valence and Core Attosecond Transient Absorption Spectroscopy
(Journal article; Tidsskriftartikkel; Peer reviewed, 2023-02-09)First principles theoretical modeling of out-of-equilibrium processes observed in attosecond pump–probe transient absorption spectroscopy (TAS) triggering pure electron dynamics remains a challenging task, especially for heavy elements and/or core excitations containing fingerprints of scalar and spin–orbit relativistic effects. To address this, we formulate a methodology for simulating TAS within ... -
Stochastic modeling of blob-like plasma filaments in the scrape-off layer: Theoretical foundation
(Journal article; Tidsskriftartikkel; Peer reviewed, 2023-04-25)A stochastic model for a superposition of uncorrelated pulses with a random distribution of amplitudes, sizes, and velocities is presented. The pulses are assumed to move radially with fixed shape and amplitudes decaying exponentially in time due to linear damping. The pulse velocities are taken to be time-independent but randomly distributed. The implications of a distribution of pulse amplitudes, ... -
A quasi-objective single buoy approach for un- derstanding Lagrangian coherent structures and sea ice dynamics
(Journal article; Tidsskriftartikkel; Peer reviewed, 2023-04-11)Sea ice drift and deformation, namely sea ice dynamics, play a significant role in atmosphere–ice–ocean coupling. Deformation patterns in sea ice can be observed over a wide range of spatial and temporal scales, though high-resolution objective quantification of these features remains difficult. In an effort to better understand local deformation of sea ice, we adapt the trajectory-stretching exponents ... -
Transition-Metal Isocorroles as Singlet Oxygen Sensitizers
(Journal article; Tidsskriftartikkel; Peer reviewed, 2023-05-04)Building on a highly efficient synthesis of pyrrole-appended isocorroles, we have worked out conditions for manganese, palladium, and platinum insertion into free-base 5/10-(2-pyrrolyl)-5,10,15-tris(4-methylphenyl)isocorrole, H<sub>2</sub>[5/10-(2-py)- TpMePiC]. Platinum insertion proved exceedingly challenging but was finally accomplished with cis-Pt(PhCN)<sub>2</sub>Cl<sub>2</sub>. All the ... -
Combination of adsorption/desorption and photocatalytic reduction processes for PFOA removal from water by using an aminated biosorbent and a UV/sulfite system
(Journal article; Tidsskriftartikkel; Peer reviewed, 2023-04-17)Per- and polyfluoroalkyl substances (PFAS) are stable organic chemicals, which have been used globally since the 1940s and have caused PFAS contamination around the world. This study explores perfluorooctanoic acid (PFOA) enrichment and destruction by a combined method of sorption/desorption and photocatalytic reduction. A novel biosorbent (PG-PB) was developed from raw pine bark by grafting amine ... -
Framework of Transactive Energy Market Strategies for Lucrative Peer-to-Peer Energy Transactions
(Journal article; Tidsskriftartikkel; Peer reviewed, 2022-12-20)Leading to the enhancement of smart grid implementation, the peer-to-peer (P2P) energy transaction concept has grown dramatically in recent years allowing the end-users to successfully exchange their excess generation and demand in a more profitable way. This paper presents local energy market (LEM) architecture with various market strategies for P2P energy trading among a set of end-users ... -
Charting the solar cycle
(Journal article; Tidsskriftartikkel; Peer reviewed, 2023-02-09)Sunspot records reveal that whilst the Sun has an approximately 11 year cycle of activity, no two cycles are of the same duration. Since this activity is a direct driver of space weather at Earth, this presents an operational challenge to quantifying space weather risk. We recently showed that the Hilbert transform of the sunspot record can be used to map the variable cycle length onto a regular ... -
Global Dynamical Network of the Spatially Correlated Pc2 Wave Response for the 2015 St. Patrick's Day Storm
(Journal article; Tidsskriftartikkel; Peer reviewed, 2023-04-26)We show the global dynamics of spatial correlation of Pc2 wave activity can track the evolution of the 2015 St. Patrick's Day geomagnetic storm for an 8 hr time window around onset. The global spatially coherent response is tracked by forming a dynamical network from 1 s data using the full set of 100+ ground-based magnetometer stations collated by SuperMAG and Intermagnet. The pattern of spatial ... -
Method for Designing Semantic Annotation of Sepsis Signs in Clinical Text
(Chapter; Bokkapittel, 2023)Annotated clinical text corpora are essential for machine learning studies that model and predict care processes and disease progression. However, few studies describe the necessary experimental design of the annotation guideline and annotation phases. This makes replication, reuse, and adoption challenging. Using clinical questions about sepsis, we designed a semantic annotation guideline to ... -
A frame based approach to computing symmetries with non-trivial isotropy groups
(Journal article; Tidsskriftartikkel; Peer reviewed, 2023-03-24)A frame approach to determining the most general solution admitting a desired symmetry group has previously been examined in Riemannian and teleparallel geometries with some success. In teleparallel geometries, one must determine the general form of the frame and spin connection to generate a general solution admitting the desired symmetry group. Current approaches often rely on the use of the ... -
Laser-Generated Scholte Waves in Floating Microparticles
(Journal article; Tidsskriftartikkel; Peer reviewed, 2023-02-04)This study aims to demonstrate the generation and detection of Scholte waves inside polystyrene microparticles. This was proven using both experimental analysis and COMSOL simulation. Microspheres of different sizes were excited optically with a pulsed laser (532 nm), and the acoustic signals were detected using a transducer (40 MHz). On analyzing the laser-generated ultrasound signals, the results ... -
Paleobathymetric reconstructions of the SW Barents Seaway and their implications for Atlantic–Arctic ocean circulation
(Journal article; Tidsskriftartikkel; Peer reviewed, 2023-06-29)Unravelling past, large-scale ocean circulation patterns is crucial for deciphering the longterm global paleoclimate. Here we apply numerical modelling to reconstruct the detailed paleobathymetry-topography of the southwestern inlet of the Barents Seaway that presently connects the Atlantic and Arctic oceans. Subaerial topography was likely enough to block Atlantic Water from entering the Barents ... -
Different mechanisms of Arctic first-year sea-ice ridge consolidation observed during the MOSAiC expedition
(Journal article; Tidsskriftartikkel; Peer reviewed, 2023-06-22)Sea-ice ridges constitute a large fraction of the ice volume in the Arctic Ocean, yet we know little about the evolution of these ice masses. Here we examine the thermal and morphological evolution of an Arctic firstyear sea-ice ridge, from its formation to advanced melt. Initially the mean keel depth was 5.6 m and mean sail height was 0.7 m. The initial rubble macroporosity (fraction of seawater ... -
Non-trace full-F gyro-fluid interchange impurity advection
(Journal article; Tidsskriftartikkel; Peer reviewed, 2023-03-01)A full-F isothermal gyro-fluid model and code (which is based on the full distribution function F compared to only small fluctuations) is extended to handle self-consistent coupling of multiple quasi-neutral ion species via the polarisation equation in the long wavelength approximation. The numerical model is used to determine two-dimensional interchange driven ‘blob’ transport in a plasma with ... -
Improving Representation Learning for Deep Clustering and Few-shot Learning
(Doctoral thesis; Doktorgradsavhandling, 2023-08-23)<p>The amounts of data in the world have increased dramatically in recent years, and it is quickly becoming infeasible for humans to label all these data. It is therefore crucial that modern machine learning systems can operate with few or no labels. The introduction of deep learning and deep neural networks has led to impressive advancements in several areas of machine learning. These advancements ... -
Sea ice classification of TerraSAR-X ScanSAR images for the MOSAiC expedition incorporating per-class incidence angle dependency of image texture
(Journal article; Tidsskriftartikkel; Peer reviewed, 2023-03-16)We provide sea ice classification maps of a subweekly time series of single (horizontal–horizontal, HH) polarization X-band TerraSAR-X scanning synthetic aperture radar (TSX SC) images from November 2019 to March 2020, covering the Multidisciplinary drifting Observatory for the Study of Arctic Climate (MOSAiC) expedition. This classified time series benefits from the wide spatial coverage ... -
A steady-state model reconstruction of the patagonian ice sheet during the last glacial maximum
(Journal article; Tidsskriftartikkel; Peer reviewed, 2023-07-17)During the Last Glacial Maximum (LGM), the Patagonian Ice Sheet (PIS) was the largest Quaternary ice mass in the Southern Hemisphere outside of Antarctica. Although the margins of the LGM ice sheet are now well established through end-moraine mapping and dating, apart from a few modelling and empirical studies, there remains a lack of constraint on its thickness and three-dimensional configuration. ... -
Solved and unsolved riddles about low-latitude daytime valley region plasma waves and 150-km echoes
(Journal article; Tidsskriftartikkel; Peer reviewed, 2023-02-27)The Earth’s atmosphere near both the geographic and magnetic equators and at altitudes between 120 and 200 km is called the low-latitude valley region (LLVR) and is among the least understood regions of the ionosphere/thermosphere due to its complex interplay of neutral dynamics, electrodynamics, and photochemistry. Radar studies of the region have revealed puzzling daytime echoes scattered from ... -
Theoretical Photoelectron Spectroscopy of Low-Valent Carbon Species: A ∼6 eV Range of Ionization Potentials among Carbenes, Ylides, and Carbodiphosphoranes
(Journal article; Tidsskriftartikkel; Peer reviewed, 2023-12-02)High-quality density functional theory calculations underscore a nearly 6 eV range for the ionization potentials (IPs) of neutral, low-valent carbon compounds, including carbenes, ylides, and zero-valent carbon compounds (carbones) such as carbodiphosphoranes (CDPs) and carbodicarbenes. Thus, adiabatic IPs as low as 5.5 ± 0.1 eV are predicted for CDPs, which are about 0.7–1.2 eV lower than those of ...