Fakultet for naturvitenskap og teknologi: Nye registreringer
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Science goals for a high-frequency radar and radio imaging array
(Journal article; Tidsskriftartikkel; Peer reviewed, 2023-08-01)A medium and high-frequency antenna array for radar and radio imaging of the ionosphere is planned for installation in Aguadilla, Puerto Rico. Science goals include the study of space weather, radio propagation, meteors, lightning, and plasma physics. Radio imaging is ideal for the study of stimulated ionospheric radio emissions, such as those induced by the Arecibo Observatory high-power HF radio ... -
A finite volume flux coordinate independent approach
(Journal article; Tidsskriftartikkel; Peer reviewed, 2023-07-03)We present a novel family of schemes as the merging between a one-dimensional advection scheme with the flux coordinate independent approach. The scheme can be used to discretize the field-aligned NavierStokes equations in three dimensions. Our approach consists of three major steps: (i) the formulation of the one-dimensional scheme in a locally field-aligned coordinate system, (ii) a numerical ... -
Coordinate Conversion and Switching Correction to Reduce Vessel Heading-Related Errors in High-Latitude Navigation
(Journal article; Tidsskriftartikkel; Peer reviewed, 2023-11-22)Considering the distortion errors of projected coordinates and the switching property of vessel heading, coordinate conversion and switching correction methods are proposed to modify a kinematic motion model and the Unscented Kalman Filter (UKF). The coordinate conversion method utilizes the grid convergence from a Universal Transverse Mercator (UTM) projection to correct the vessel heading. The ... -
Tanning Wastewater Sterilization in the Dark and Sunlight Using Psidium guajava Leaf-Derived Copper Oxide Nanoparticles and Their Characteristics
(Journal article; Tidsskriftartikkel; Peer reviewed, 2023-10-09)Employing Psidium guajava (P. guajava) extract from leaves, copper oxide nanoparticles (CuO NPs), likewise referred to as cupric oxide and renowned for their sustainable and harmless biogenesis, have the possibility of being useful for the purification of pollutants as well as for medicinal purposes. The current study examined the generated CuO NPs and their physical qualities by using ultraviolet−visible ... -
The transition from normal marine to evaporitic conditions recorded in a cold seep environment: The Messinian succession of Northern Italy
(Journal article; Tidsskriftartikkel; Peer reviewed, 2023-11-26)Messinian pre-evaporitic seep carbonates outcropping in the Tuscan-Romagna area share a common upward stratigraphic trend: massive seep carbonates rich in large lucinids, modiolids and planktonic foraminifera pass upward to horizontally laminated carbonates free of macrofauna and foraminifera. A transitional macrofauna-free facies marks the passage in some sections, sometimes with faint lamination. ... -
The Stepwise Reduction of Multiyear Sea Ice Area in the Arctic Ocean Since 1980
(Journal article; Tidsskriftartikkel; Peer reviewed, 2023-09-28)The loss of multiyear sea ice (MYI) in the Arctic Ocean is a significant change that affects all facets of the Arctic environment. Using a Lagrangian ice age product, we examine MYI loss and quantify the annual MYI area budget from 1980 to 2021 as the balance of export, melt, and replenishment. Overall, MYI area declined at 72,500 km<sup>2</sup> /yr; however, a majority of the loss occurred ... -
Retrieval of Snow Depth on Arctic Sea Ice From Surface-Based, Polarimetric, Dual-Frequency Radar Altimetry
(Journal article; Tidsskriftartikkel; Peer reviewed, 2023-10-18)Snow depth on sea ice is an Essential Climate Variable and a major source of uncertainty in satellite altimetry-derived sea ice thickness. During winter of the MOSAiC Expedition, the “KuKa” dual-frequency, fully polarized Ku- and Ka-band radar was deployed in “stare” nadir-looking mode to investigate the possibility of combining these two frequencies to retrieve snow depth. Three approaches ... -
Evaluating Deep Q-Learning Algorithms for Controlling Blood Glucose in In Silico Type 1 Diabetes
(Journal article; Tidsskriftartikkel; Peer reviewed, 2023-10-07)Patients with type 1 diabetes must continually decide how much insulin to inject before each meal to maintain blood glucose levels within a healthy range. Recent research has worked on a solution for this burden, showing the potential of reinforcement learning as an emerging approach for the task of controlling blood glucose levels. In this paper, we test and evaluate several deep Q-learning algorithms ... -
Statistical experiment analysis of wear and mechanical behaviour of abaca/sisal fiber-based hybrid composites under liquid nitrogen environment
(Journal article; Tidsskriftartikkel; Peer reviewed, 2023-08-04)Ice accretion on various onshore and offshore infrastructures imparts hazardous effects sometimes beyond repair, which may be life-threatening. Therefore, it has become necessary to look for ways to detect and mitigate ice. Some ice mitigation techniques have been tested or in use in aviation and railway sectors, however, their applicability to other sectors/systems is still in the research phase. ... -
Bulky, electron-rich, renewable: analogues of Beller's phosphine for cross-couplings
(Journal article; Tidsskriftartikkel; Peer reviewed, 2023-10-30)In recent years, considerable progress has been made in the conversion of biomass into renewable chemicals, yet the range of value-added products that can be formed from biomass remains relatively small. Herein, we demonstrate that molecules available from biomass serve as viable starting materials for the synthesis of phosphine ligands, which can be used in homogeneous catalysis. Specifically, ... -
Multiple Signal Classification Algorithm: A computational microscopy tool for fluorescence microscopy
(Doctoral thesis; Doktorgradsavhandling, 2023-12-11)Fluorescence Microscopy is still the most preferred tool for studying the cell's inner structures. One of the reasons for this preference is its great selectivity, which allows it to label specific types of structures and visualize them with high contrast. However, its resolution is conventionally limited due to the diffraction of light, which makes the study of cells at scales below 200 nm challenging. ... -
A long-term proxy for sea ice thickness in the Canadian Arctic: 1996-2020
(Journal article; Tidsskriftartikkel; Peer reviewed, 2023-08-15). This study presents a long-term winter sea ice thickness proxy product for the Canadian Arctic based on a random forest regression model – applied to ice charts and scatterometer data, trained on CryoSat-2 observations, and applying an ice type–sea ice thickness correction using the Pan-Arctic Ice Ocean Modeling and Assimilation System (PIOMAS) – that provides 25 years of sea ice thickness ... -
Influence of Fluorinated Substituents on the Near-Infrared Phosphorescence of 5d Metallocorroles
(Journal article; Tidsskriftartikkel; Peer reviewed, 2023-07-12)The influence of fluorinated substituents on the luminescent properties of rhenium-oxo, osmium-nitrido, and gold triarylcorroles was studied via a comparison of four ligands: triphenylcorrole (TPC), tris(ptrifluoromethylphenyl)corrole (TpCF<sub>3</sub>PC), tris{3,5-bis(trifluoromethyl)- phenyl}corrole (T3,5-CF<sub>3</sub>PC), and tris(pentafluorophenyl)corrole (TPFPC). For each metal series ... -
Comparing elevation and backscatter retrievals from CryoSat-2 and ICESat-2 over Arctic summer sea ice
(Journal article; Tidsskriftartikkel; Peer reviewed, 2023-09-27)The CryoSat-2 radar altimeter and ICESat-2 laser altimeter can provide complementary measurements of the freeboard and thickness of Arctic sea ice. However, both sensors face significant challenges for accurately measuring the ice freeboard when the sea ice is melting in summer months. Here, we used crossover points between CryoSat2 and ICESat-2 to compare elevation retrievals over summer sea ... -
Raman-spectroscopy of extracellular vesicles and self-supervised deep learning
(Doctoral thesis; Doktorgradsavhandling, 2023-12-07)This thesis explores the prospect of a waveguide device for optical trapping and Raman spectroscopy of single biological nanoparticles. The aim of the work is to develop a Raman-on-chip device capable of training and measuring single particles in individual trapping sites, such that the throughput of the device can be increased through parallelization. The challenge posed by the induced Raman ... -
Improving spam email classification accuracy using ensemble techniques: a stacking approach
(Journal article; Tidsskriftartikkel; Peer reviewed, 2023-09-20)Spam emails pose a substantial cybersecurity danger, necessitating accurate classification to reduce unwanted messages and mitigate risks. This study focuses on enhancing spam email classification accuracy using stacking ensemble machine learning techniques.We trained and tested five classifiers: logistic regression, decision tree, K-nearest neighbors (KNN), Gaussian naive Bayes and AdaBoost. To ... -
Initial characterization of an iron superoxide dismutase from Thermobifida fusca
(Journal article; Tidsskriftartikkel; Peer reviewed, 2023-09-19)Superoxide dismutases (SODs) are enzymes that catalyze the dismutation of the superoxide radical anion into O<sup>2</sup> and H<sup>2</sup>O<sup>2</sup> in a two-step reaction. They are ubiquitous to all forms of life and four different types of metal centers are detected, dividing this class of enzymes into Cu-/Zn-, Ni-, Mn-, and Fe-SODs. In this study, a superoxide dismutase from the ... -
Super-resolution histology
(Doctoral thesis; Doktorgradsavhandling, 2023-12-05)<p>Super-resolution optical microscopy (SRM) holds great promise for the advancement of life sciences, unlocking the secrets of the minute machinery composing living organisms. While broadly accepted in cell biology, the existing SRM methods haven’t effectively breached relevant fields such as histological practice, mainly due to the complexity, elevated costs, limited throughput, and incompatibility ... -
Deep Learning for Enhanced Fault Diagnosis of Monoblock Centrifugal Pumps: Spectrogram-Based Analysis
(Journal article; Tidsskriftartikkel; Peer reviewed, 2023-08-31)Abstract The reliable operation of monoblock centrifugal pumps (MCP) is crucial in various industrial applications. Achieving optimal performance and minimizing costly downtime requires effectively detecting and diagnosing faults in critical pump components. This study proposes an innovative approach that leverages deep transfer learning techniques. An accelerometer was adopted to capture vibration ... -
The weakening AMOC under extreme climate change
(Journal article; Tidsskriftartikkel; Peer reviewed, 2023-10-06)Changes in the Atlantic Meridional Overturning Circulation (AMOC) in the quadrupled CO<sub>2</sub> experiments conducted under the sixth Coupled Model Intercomparison Project (CMIP6) are examined. Increased CO<sub>2</sub> triggers extensive Arctic warming, causing widespread melting of sea ice. The resulting freshwater spreads southward, frst from the Labrador Sea and then the Nordic Seas, and ...