Institutt for fysikk og teknologi: Nye registreringer
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Demonstrating low Raman background in UV-written SiO2 waveguides
(Journal article; Tidsskriftartikkel; Peer reviewed, 2023-09-06)Raman spectroscopy can give a chemical ’fingerprint’ from both inorganic and organic samples, and has become a viable method of measuring the chemical composition of single biological particles. In parallel, integration of waveguides and microfluidics allows for the creation of miniaturized optical sensors in lab-on-a-chip devices. The prospect of combining integrated optics and Raman spectroscopy ... -
Barents-2.5km v2.0: an operational data-assimilative coupled ocean and sea ice ensemble prediction model for the Barents Sea and Svalbard
(Journal article; Tidsskriftartikkel; Peer reviewed, 2023-09-22)An operational ocean and sea ice forecast model, Barents-2.5, is implemented for short-term forecasting at the coast off northern Norway, the Barents Sea, and the waters around Svalbard. Primary forecast parameters are sea ice concentration (SIC), sea surface temperature (SST), and ocean currents. The model also provides input data for drift modeling of pollutants, icebergs, and search-and-rescue ... -
Change in Climate Sensitivity and Its Dependence on the Lapse-Rate Feedback in 4 x CO2 Climate Model Experiments
(Journal article; Tidsskriftartikkel, 2022-04-19)Robust estimates of climate sensitivity are important for decision-making on mitigation of climate change. However, climate sensitivity and its governing processes are still subject to large uncertainty. Recently it has been established that climate sensitivity changes over time in numerical climate model experiments with abrupt quadrupling of the CO<sub>2</sub> concentration. Here we conduct an ... -
Selective Imputation for Multivariate Time Series Datasets with Missing Values
(Journal article; Tidsskriftartikkel, 2023-01-31)Multivariate time series often contain missing values for reasons such as failures in data collection mechanisms. Since these missing values can complicate the analysis of time series data, imputation techniques are typically used to deal with this issue. However, the quality of the imputation directly affects the performance of downstream tasks. In this paper, we propose a selective imputation ... -
Assimilation of high-resolution ice charts in a coupled ocean-sea-ice model
(Journal article; Tidsskriftartikkel, 2019)In this study, we show assimilation results from a coupled ocean sea-ice model. The model has a horizontal resolution of 2.5 km. In the assimilation system, we assimilate high-resolution ice charts, structured on a 1 km grid. We compare the assimilation of passive microwave observations with the assimilation of ice charts. It is shown that the ice charts have a larger impact on the assimilation ... -
Image analysis and segmentation of polar mesospheric summer echoes
(Conference object; Konferansebidrag, 2022-07) -
Structured Illumination Microscopy of Biological Structures
(Conference object; Konferansebidrag, 2018)<p>Resolution in optical microscopy has long been limited to the Abbe diffraction limit, i.e. about 250 nm laterally for visible wavelengths on a very good microscope. In the last two decades several techniques have been devised to circumvent this limit: an achievement which was recognized with the 2014 Nobel Prize in Chemistry. Structured Illumination Microscopy (SIM) was the first of these techniques ... -
Observing Oil Releases from Platforms Using Synthetic Aperture Radar
(Conference object; Konferansebidrag, 2018)Synthetic aperture radar (SAR) is used for operational surveillance of ocean areas and oil spill detection. Oil spills are frequently detected around oil platforms due to the releases of so-called produced water (PW), which is water containing low concentrations of oil that can form surface slicks similar to other oil spills. PW releases are legal within given limits. Understanding the signatures ... -
Selecting principal attributes in multimodal remote sensing for sea ice characterization
(Chapter; Bokkapittel, 2021)Automatic ice charting cannot be achieved using only SAR modalities. It is fundamental to combine information from other remote sensors with different characteristics for more reliable sea ice characterization. In this paper, we employ principal feature analysis (PFA) to select significant information from multimodal remote sensing data. PFA is a simple yet very effective approach that can be applied ... -
Detecting the linear and non-linear causal links for disturbances in the power grid
(Chapter; Bokkapittel, 2021)Unscheduled power disturbances cause severe consequences for customers and grid operators. To avoid suchevents, it is important to identify the causes and localize the sources of the disturbances in the power distribution network. In this work, we focus on a specific power grid in the Arctic region of Northern Norway that experiences an increased frequency of failures of unspecified origin. -
Learning nanoscale motion patterns of vesicles in living cells
(Chapter; Bokkapittel, 2020)Detecting and analyzing nanoscale motion patterns of vesicles, smaller than the microscope resolution (~250 nm), inside living biological cells is a challenging problem. State-of-the-art CV approaches based on detection, tracking, optical flow or deep learning perform poorly for this problem. We propose an integrative approach, built upon physics based simulations, nanoscopy algorithms, and shallow ... -
A Kernel to Exploit Informative Missingness in Multivariate Time Series from EHRs
(Chapter; Bokkapittel, 2020)A large fraction of the electronic health records (EHRs) consists of clinical measurements collected over time, such as lab tests and vital signs, which provide important information about a patient’s health status. These sequences of clinical measurements are naturally represented as time series, characterized by multiple variables and large amounts of missing data, which complicate the analysis. ... -
A Protocol for Single-Molecule Translation Imaging in Xenopus Retinal Ganglion Cells
(Chapter; Bokkapittel, 2020-04-29)Single-molecule translation imaging (SMTI) is a straightforward technique for the direct quantification of local protein synthesis. The protein of interest is fused to a fast-folding and fast-bleaching fluorescent protein, allowing one to monitor the appearance of individual fluorescence events after photobleaching of pre-existing proteins in the cell under investigation. The translation of individual ... -
Unsupervised Band Selection for Hyperspectral Datasets by Double Graph Laplacian Diagonalization
(Journal article; Tidsskriftartikkel, 2021)The vast amount of spectral information provided by hyperspectral images can be useful for different applications. However, the presence of redundant bands will negatively affect application performance. Therefore, it is crucial to select a relevant subset that preserves the information of the original set. In this paper, we present an automatic and accurate band selection method based on Graph ... -
Explaining doping in material research (Hf substitution in ZnO films) by directly quantifying the van der Waals force
(Journal article; Tidsskriftartikkel; Peer reviewed, 2020-02-04)Non-monotonic behavior has been observed in the optoelectronic properties of ZnO thin films as doped with Hf (HZO). Here we propose that two competing mechanisms are responsible for such behaviour. Specifically, we propose that provided two crystal orientations dominate film growth, only one of them might be responsible for direct Hf substitution. Nonmonotonic behaviour is expected at once by ... -
Structured illumination microscopy using a photonic chip
(Journal article; Tidsskriftartikkel; Peer reviewed, 2020-04-11)Structured illumination microscopy (SIM) enables live-cell super-resolution imaging of subcellular structures at high speeds. At present, linear SIM uses free-space optics to illuminate the sample with the desired light patterns; however, such arrangements are prone to misalignment and add cost and complexity to the microscope. Here, we present an alternative photonic chip-based two-dimensional SIM ... -
Alignment of Multifrequency SAR Images Acquired over Sea Ice Using Drift Compensation
(Journal article; Tidsskriftartikkel; Peer reviewed, 2023-08-07)In this article, we investigate the feasibility to align synthetic aperture radar (SAR) imagery based on a compensation for sea ice drift occurring between temporally shifted image acquisitions. The image alignment is a requirement for improving sea ice classification by combining multifrequency SAR images acquired at different times. Images obtained at different radar frequencies provide ... -
Effect of caffeine and other xanthines on liver sinusoidal endothelial cell ultrastructure
(Journal article; Tidsskriftartikkel; Peer reviewed, 2023-08-17)Xanthines such as caffeine and theobromine are among the most consumed psychoactive stimulants in the world, either as natural components of cofee, tea and chocolate, or as added ingredients. The present study assessed if xanthines affect liver sinusoidal endothelial cells (LSEC). Cultured primary rat LSEC were challenged with xanthines at concentrations typically obtained from normal consumption of ... -
Impacts of offshore oil spill accidents on island bird communities: A test run study around Orkney and Svalbard archipelagos
(Journal article; Tidsskriftartikkel; Peer reviewed, 2023-07-15)The sea area around the Orkney archipelago, Scotland is subjected to substantial maritime shipping activities. By contract, the Svalbard archipelago, Norway currently has a rather low marine traffic profile. Future projections, however, indicate that the Trans-Arctic route might change the whole transportation picture and Svalbard may be at the centre of maritime activities. Both archipelagos ... -
Outlier classification using Autoencoders: applications for fluctuation driven flows in fusion plasmas
(Conference object; Konferansebidrag, 2018)