Fakultet for naturvitenskap og teknologi: Nye registreringer
Viser treff 3821-3840 av 5434
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Optimization of Pure-Component LNG Cascade Processes with Heat Integration
(Journal article; Tidsskriftartikkel, 2018-01-15)Liquefaction of natural gas is an energy-intensive process in which the energy efficiency depends on the number of compressors stages and the heat integration scheme. The aim of the study is to systematically evaluate process performance of pure component cascade processes, present optimized designs for all relevant numbers of compression stages and compare energy consumption between processes with ... -
Ice intelligence retrieval by remote sensing - Possibilities and challenges in an operational setting
(Peer reviewed; Chapter; Bokkapittel, 2017)Detecting ice drift velocity when operating offshore in ice-covered waters is crucial during marine operations, as ice actions affect station keeping and ice management. Furthermore, other ice data/intelligence such as ice concentration and thickness are important parameters to determine ice resistance, evaluate performance of icebreakers and predict ice actions on structures. Different sensors are ... -
Probability distribution functions for intermittent scrape-off layer plasma fluctuations
(Journal article; Peer reviewed; Tidsskriftartikkel, 2018-01-24)A stochastic model for intermittent fluctuations in the scrape-off layer of magnetically confined plasmas has been constructed based on a super-position of uncorrelated pulses arriving according to a Poisson process. In the most common applications of the model, the pulse amplitudes are assumed exponentially distributed, supported by conditional averaging of large-amplitude fluctuations in experimental ... -
Cascading lake drainage on the Greenland Ice Sheet triggered by tensile shock and fracture
(Journal article; Tidsskriftartikkel; Peer reviewed, 2018-03-14)Supraglacial lakes on the Greenland Ice Sheet are expanding inland, but the impact on ice flow is equivocal because interior surface conditions may preclude the transfer of surface water to the bed. Here we use a well-constrained 3D model to demonstrate that supraglacial lakes in Greenland drain when tensile-stress perturbations propagate fractures in areas where fractures are normally absent or ... -
Glacigenic sedimentation pulses triggered postglacial gas hydrate dissociation
(Journal article; Tidsskriftartikkel; Peer reviewed, 2018-02-12)Large amounts of methane are stored in continental margins as gas hydrates. They are stable under high pressure and low, but react sensitively to environmental changes. Bottom water temperature and sea level changes were considered as main contributors to gas hydrate dynamics after the last glaciation. However, here we show with numerical simulations that pulses of increased sedimentation dominantly ... -
Magnetotelluric signatures of the complex tertiary fold–thrust belt and extensional fault architecture beneath Brøggerhalvøya, Svalbard
(Journal article; Tidsskriftartikkel; Peer reviewed, 2017-12-18)Magnetotelluric (MT) data were recently collected on Brøggerhalvøya, Svalbard, in a 0.003–1000 s period range along a curved WNW–ESE profile. The collected data manifested strong three-dimensional (3D) effects. We modelled the full impedance tensor with tipper and bathymetry included in 3D, and benchmarked the result with determinant data two-dimensional (2D) inversion. The final inversion results ... -
EURODELTA-Trends, a multi-model experiment of air quality hindcast in Europe over 1990-2010
(Journal article; Tidsskriftartikkel; Peer reviewed, 2017-09-05)The EURODELTA-Trends multi-model chemistry-transport experiment has been designed to facilitate a better understanding of the evolution of air pollution and its drivers for the period 1990–2010 in Europe. The main objective of the experiment is to assess the efficiency of air pollutant emissions mitigation measures in improving regional-scale air quality. <br>The present paper formulates the ... -
Evaluation of a method to derive ionospheric conductivities using two auroral emissions (428 and 630 nm) measured with a photometer at Tromsø (69.6°N)
(Journal article; Tidsskriftartikkel; Peer reviewed, 2017-07-03)This paper mainly aims at evaluating capabilities of derivation of ionospheric conductivities using two principal auroral emissions (427.8 and 630 nm). We have evaluated a photometric method of derivation of ionospheric conductivities based on simultaneous observations of a photometer (feld of view = ~1.2°), a digital camera, and the EISCAT UHF radar (feld of view = ~0.7°) operated at Tromsø, ... -
Prospecting biotechnologically-relevant monooxygenases from cold sediment metagenomes: An in silico approach
(Journal article; Tidsskriftartikkel; Peer reviewed, 2017-04-09)The goal of this work was to identify sequences encoding monooxygenase biocatalysts with novel features by in silico mining an assembled metagenomic dataset of polar and subpolar marine sediments. The targeted enzyme sequences were Baeyer–Villiger and bacterial cytochrome P450 monooxygenases (CYP153). These enzymes have wide-ranging applications, from the synthesis of steroids, antibiotics, mycotoxins ... -
Labilibaculum manganireducens gen. nov., sp. nov. and Labilibaculum filiforme sp. nov., Novel Bacteroidetes Isolated from Subsurface Sediments of the Baltic Sea
(Journal article; Tidsskriftartikkel; Peer reviewed, 2018-01-05)Microbial communities in deep subsurface sediments are challenged by the decrease in amount and quality of organic substrates with depth. In sediments of the Baltic Sea, they might additionally have to cope with an increase in salinity from ions that have diffused downward from the overlying water during the last 9000 years. Here, we report the isolation and characterization of four novel bacteria ... -
Classification of low backscatter ocean regions using log-cumulants
(Conference object; Konferansebidrag, 2015-01)In a synthetic aperture radar image, low backscatter regions of various origin can be observed in ocean areas. Operational oil spill detection services work to discriminate anthropogenic oil spills from natural phenomena such as seeps, low wind fields, thin ice and biogenic slicks. In this paper, we investigate the potential of using matrix log-cumulants for this purpose. -
Stochastic modeling of scrape-off layer fluctuations
(Conference object; Konferansebidrag, 2017-08-24)1. Stochastic model of data time series <br> 2. Comparison to experimental measurements -
Metallo-β-lactamase inhibitors by bioisosteric replacement: preparation, activity and binding
(Journal article; Tidsskriftartikkel; Peer reviewed, 2017-04-14)Bacterial resistance is compromising the use of β-lactam antibiotics including carbapenems. The main resistance mechanism against β-lactams is hydrolysis of the β-lactam ring mediated by serine- or metallo-β-lactamases (MBLs). Although several inhibitors of MBLs have been reported, none has been developed into a clinically useful inhibitor. Mercaptocarboxylic acids are among the most prominent ... -
Dark zone of the Greenland Ice Sheet controlled by distributed biologically-active impurities
(Journal article; Tidsskriftartikkel; Peer reviewed, 2018-03-14)Albedo—a primary control on surface melt—varies considerably across the Greenland Ice Sheet yet the specific surface types that comprise its dark zone remain unquantified. Here we use UAV imagery to attribute seven distinct surface types to observed albedo along a 25 km transect dissecting the western, ablating sector of the ice sheet. Our results demonstrate that distributed surface impurities—an ... -
Temperature and thermal emission of cosmic dust in the vicinity of the Sun, Vega and Fomalhaut.
(Conference object; Konferansebidrag, 2018) -
Dynamics of Dust Particles near Sun, Vega and Fomalhaut
(Conference object; Konferansebidrag, 2018) -
Effects of low oxygen concentrations on aerobic methane oxidation in seasonally hypoxic coastal waters
(Journal article; Tidsskriftartikkel; Peer reviewed, 2017-03-29)Coastal seas may account for more than 75 % of global oceanic methane emissions. There, methane is mainly produced microbially in anoxic sediments from which it can escape to the overlying water column. Aerobic methane oxidation (MOx) in the water column acts as a biological filter, reducing the amount of methane that eventually evades to the atmosphere. The efficiency of the MOx filter is potentially ... -
Pulsating aurora and cosmic noise absorption associated with growth-phase arcs
(Journal article; Tidsskriftartikkel; Peer reviewed, 2018-01-18)The initial stage of a magnetospheric substorm is the growth phase, which typically lasts 1–2 h. During the growth phase, an equatorward moving, east–west extended, optical auroral arc is observed. This is called a growth-phase arc. This work aims to characterize the optical emission and riometer absorption signatures associated with growth-phase arcs of isolated substorms. This is done using ... -
Non-triggered auroral substorms and long-period (1–4 mHz) geomagnetic and auroral luminosity pulsations in the polar cap
(Journal article; Tidsskriftartikkel; Peer reviewed, 2017-03-08)A study is undertaken into parameters of the polar auroral and geomagnetic pulsations in the frequency range 1– 4 mHz (Pc5/Pi3) during quiet geomagnetic intervals preceding auroral substorms and non-substorm background variations. Special attention is paid to substorms that occur under parameters of the interplanetary magnetic field (IMF) conditions typical for undisturbed days (“non-triggered ... -
The red-sky enigma over Svalbard in December 2002
(Journal article; Tidsskriftartikkel; Peer reviewed, 2005-07-27)On 6 December 2002, during winter darkness, an extraordinary event occurred in the sky, as viewed from Longyearbyen (78° N, 15° E), Svalbard, Norway. At 07:30 UT the southeast sky was surprisingly lit up in a deep red colour. The light increased in intensity and spread out across the sky, and at 10:00 UT the illumination was observed to reach the zenith. The event died out at about 12:30 UT. Spectral ...