Nordic Seas polynyas and their role in preconditioning marine productivity during the Last Glacial Maximum.

Arctic and Antarctic polynyas are crucial sites for deep-water formation, which helps sustain global ocean circulation. During glacial times, the occurrence of polynyas proximal to expansive ice sheets in both hemispheres has been proposed to explain limited ocean ventilation and a habitat requirement for marine and higher-trophic terrestrial fauna. Nonetheless, their existence remains equivocal, not least due to the hitherto paucity of sufficiently characteristic proxy data. Here we demonstrate polynya formation in front of the NW Eurasian ice sheets during the Last Glacial Maximum (LGM), which resulted from katabatic winds blowing seaward of the ice shelves and upwelling of warm, sub-surface Atlantic water. These polynyas sustained ice-sheet build-up, ocean ventilation, and marine productivity in an otherwise glacial Arctic desert. Following the catastrophic meltwater discharge from the collapsing ice sheets at ~17.5 ka BP, polynya formation ceased, marine productivity declined dramatically, and sea ice expanded rapidly to cover the entire Nordic Seas

Reactivity of coke in relation to sulfur level and microstructure

Shrinkage induced flow, thermo-solutal convection and equiaxed grain motion are the major transport mechanisms contributing to macrosegregation formation in aluminum alloys produced through Direct Chill casting. Experimental and numerical studies were conducted to provide insight on macrosegregation formation in AA5182 ingots. Previous numerical studies indicated that the weak thermo-solutal convection, both individually and in its interaction with grain motion, has an insignificant contribution to macrosegregation formation. These studies were, however, conducted using 2D simulations of sheet ingots. In this paper, we carry out 3D modelling of sheet ingots with the same alloy by employing a multiphase, multiscale solidification model based on volume averaging method accounting for thermo-solutal convection and globular grain motion. We show that the coupling between thermo-solutal convection and grain motion is important to provide a better description of macrosegregation formation during DC casting of AA5182 alloy. The numerical work is discussed considering experimental horizontal macrosegregation maps.acceptedVersio

A XANES Study of Sulfur Speciation and Reactivity in Cokes for Anodes Used in Aluminum Production

Availability of anode raw materials in the growing aluminum industry results in a wider range of petroleum cokes being used to produce carbon anodes. The boundary between anode grade cokes and what previously was considered non-anode grades are no longer as distinct as before, leading to introduction of cokes with higher sulfur and higher trace metal impurity content in anode manufacturing. In this work, the chemical nature of sulfur in five industrial cokes, ranging from 1.42 to 5.54 wt pct S, was investigated with K-edge XANES, while the reactivity of the cokes towards CO2 was measured by a standard mass loss test. XANES identified most of the sulfur as organic sulfur compounds. In addition, a significant amount is identified (16 to 53 pct) as S-S bound sulfur. A strong inverse correlation is observed between CO2-reactivity and S-S bound sulfur in the cokes, indicating that the reduction in reactivity is more dependent on the amount of this type of sulfur compound rather than the total amount of sulfur or the amount of organic sulfur

Reactivity of coke in relation to sulfur level and microstructure

Shrinkage induced flow, thermo-solutal convection and equiaxed grain motion are the major transport mechanisms contributing to macrosegregation formation in aluminum alloys produced through Direct Chill casting. Experimental and numerical studies were conducted to provide insight on macrosegregation formation in AA5182 ingots. Previous numerical studies indicated that the weak thermo-solutal convection, both individually and in its interaction with grain motion, has an insignificant contribution to macrosegregation formation. These studies were, however, conducted using 2D simulations of sheet ingots. In this paper, we carry out 3D modelling of sheet ingots with the same alloy by employing a multiphase, multiscale solidification model based on volume averaging method accounting for thermo-solutal convection and globular grain motion. We show that the coupling between thermo-solutal convection and grain motion is important to provide a better description of macrosegregation formation during DC casting of AA5182 alloy. The numerical work is discussed considering experimental horizontal macrosegregation maps

Tekstur og fett i laksefilet

Om høsten prioriterer laks å lagre fett heller enn å forbruke det til energi. Dersom fettlagrene er lave ved inngangen til høsten, vil fisken spise seg opp, vokse raskt og få økt risiko for å utvikle teksturproblemer. Problematisk gaping ble registrert hos 18 % av laksen som var mager i august (11 % fett) med rask høstvekst (TGC 4,3). Kun 3 % av laksen med mer filetfett (16 %) og jevn vekst (TGC 2,9) hadde problematisk gaping. Fettretensjonen i muskel var på 48 % i august–oktober mot 24 % i desember–mars. Det betyr at nesten halvparten av fôrfettet ble lagret i fileten om høsten, mot en fjerdepart om våren. Bærekraftig utnyttelse av kostbar marin fôrolje, vil derfor være å benytte høyere nivå av marint omega-3 om høsten, og heller ha lavt nivå om våren da fettet i større grad forbrennes. Våre resultater viste at EPA+DHA som ble deponert i høstfettet hadde en svært langsom «utvasking». Slik vil sesongfôring øke omega-3utbyttet fra fôret. Fettsyren DPA dannes fra EPA og har samme kjedelengde som DHA. Etter vår oppfatning bør nivå av DPA legges til summen av EPA+DHA for å få et riktigere totalbilde av deponering av marint omega-3 fra fôret (retensjonsberegninger). Det er viktig å fremskaffe mer kunnskap om optimale blandinger av planteoljer som fôrkilde til laks av ulik størrelse og i forhold til miljøforhold for å opprettholde en kostnadseffektiv produksjon av sunn kvalitetslaks. Trolig kan nivået av planteoljer være høyt og over 70 % dersom oljeblandingen er velbalansert. God helsestatus gjør fisken bedre rustet til å takle stress og bevare god filetkvalitet. Resultatene tydet på at det er mulig å stimulere til økt muskelbygging og mer robust muskel ved å gi laksen ekstra protein tidlig i livet, for deretter å gå over til et standard fôr. Dette er ny kunnskap! Optimalt tidsvindu for å stimulere til kraftigere muskelbygging (økt filetutbytte/fastere filet) bør defineres; for eksempel vurdere varighet og om tidsvinduet kan skyves over i ferskvannsfasen. Ekstra innblanding av proteiner (2,5 %) i standard kommersielt fôr forbedret fastheten, reduserte gaping, ga økt slakteutbytte (0,9 % høyere), økt filetutbytte (1,6 %) og bedre fiskehelse.Tekstur og fett i laksefiletpublishedVersio