Effect of rearing temperature on flesh quality in Arctic charr (Salvelinus alpinus)

Currently, no information is available on the effect of progressively decreasing temperatures on the sensory quality of Arctic charr. The objective of this study was to investigate if and how different and progressively changing rearing temperatures affect the sensory quality of cooked and raw fillets of Arctic charr. The effects of rearing temperature on the sensory quality of Arctic charr (weight range 622–888 g) were investigated. Rearing temperature was changed during the experimental period as the fish were reared at constant or decreased temperature during October to April and subsequently reared at two constant temperatures from April to August establishing six different rearing temperature combinations. Significant differences were seen in all four main sensory attributes groups, that is odour, appearance, flavour and texture. Freshness characteristics such as sweet odour and flavour, and metallic odour and flavour increased with decreasing rearing temperature, whereas musty odour and flavour decreased. Rearing temperature had a clear effect on the colour of the fillets. Lower rearing temperature increased colour intensity substantially. Softness, juiciness and tenderness increased with decreased rearing temperature. A trend was seen towards more effect from final rearing temperature than initial temperature on the sensory attributes studied. Spoilage characteristics, that is, sour and rancid odour and flavour, and off-odour and flavour were either very weak or not noticeable in all sample groups.acceptedVersio

Environmental manipulation of land-based farmed Arctic charr; effects on growth, feeding and maturation

Farming of Arctic charr takes mainly place in land-based farms applying intensive rearing methods with relatively high production costs. Depending on local conditions at each site, it is possible to regulate important environmental factors to improve productivity and well-being of the fish. Knowledge about how these different environmental factors affect various farming traits are therefore important to reduce production costs. The aim to this thesis was to investigate how rearing temperature, photoperiod, salinity and feeding rations can be used to enhance the production of land-based Arctic charr. Rearing temperature is a highly effective tool to improve growth rate of Arctic charr. (Paper I). Juvenile Arctic charr reared at a constant temperature of 15 °C had mean weights that were 44 % and 78 % higher than fish reared at constant temperatures of 12 and 9 C, respectively. Attempts to transfer the Arctic charr down in rearing temperature as an effort to follow the drop in temperature optima for growth resulted in a consistently negative effects on the growth rate. High growth rates as observed at the higher temperature groups (Paper I) with subsequent high condition factor lead to higher incidence of maturation. Rearing of Arctic charr at periodic restricted feed rations (50 %) in Paper II led to full growth compensation (CG) of the farmed Arctic charr. Restricted feed groups had both higher feed intake and feed conversion efficiency during the re-feeding periods compared to the full ration group. Periodical feed restriction regimes had lower maturation level compared to full ration groups. The application of a six week short photoperiod within other ways continuous photoperiod improved long term growth rate of Arctic charr reared in freshwater (Paper III). Short day groups weighed 10.7–13.9 % more than the group reared on continuous light. Feed intake and feeding conversion efficiency increased following transfer to continuous light after a period of short day (Paper III) explaining the growth enhancement effect. Rearing salinity affected growth rate of Arctic charr and was higher for the lower salinity groups and maturation was lower and delayed (Paper IV) in these same groups. Final weights of female Arctic charr reared at 17 ‰ were 19 % and 27 % higher than for the females in the 17-27 ‰ and 27 ‰ groups, respectively. Effort to induce the smoltification by application of a six week short day signal during early winter followed by transfer to continuous light (Paper IV) failed as no differences in neither gill NKA nor plasma Na+ levels were detected compared with a control group kept at continuous light. Higher long term growth in the group receiving short day treatment in early winter is therefore likely linked to higher feed intake and or improved feeding efficiency following return to continuous light like demonstrated in Paper III rather than improved seawater tolerance for that group. Overall there appear to be an interactive effect on maturation from applying short-day photoperiod and subsequent rearing at higher salinity as GSI was higher in the short day groups reared at higher salinities. In the thesis it has been demonstrated how rearing temperature, photoperiod, salinity and feeding ratio can affect farming traits like growth rate, maturation and feed conversion efficiency. High growth rate during juvenile phase as observed in the higher temperature groups (Paper I) can result in higher incidence of maturation during on growing period. Photoperiod manipulation and feed ration can be used as tools to improve growth and reduce maturation. Salinity has negative effect on growth rate but farmers with rich access to brackish water may get acceptable growth rates during on growing period. Future studies should focus on better preserving the potential high growth rate of Arctic charr during juvenile phase into the on growing period and establish protocols to improve the seawater tolerance of Arctic charr

Neytendahegðun á íslenskum tölvuleikjamarkaði. Kortlagning tölvuleikjamarkaðarins.

Markmið rannsóknarinnar er að kortleggja og skilja neytendahegðun á íslenskum tölvuleikjamarkaði hvað varðar spilamennsku, þætti sem skipta hvað mestu fyrir neytendur og hvar neytendur eru að spila sína leiki, það er að segja PC, Playstation, Nintendo, Xbox eða síma. Til þess að komast að þessu verður notast við megindlega rannsóknaraðferð þar sem búinn verður til spurningalisti sem verður sendur út til almennings sem spilar tölvuleiki. Spurt var um hvar neytendur spila leiki sína, hvernig leiki þeir spila, hversu oft spila þeir leiki, mikilvægi þess að spila með vinum, hvort verslað er í gegnum netverslanir eða hefðbundnar verslanir, áhrifavaldar og hvort þeir spili fría leiki. Tölvuleikjamarkaðurinn er fljótur að breytast og þróast og þess vegna er skilningur á hvernig markaðurinn hegðar sér lykilþáttur í því að ná árangri á þessum mikla samkeppnismarkaði. Niðurstöðurnar benda til þess að neytendur spili það sem vinir þeirra spili, og er val á tölvu tengt því. Neytendur eru helst að kaupa leiki í gegnum netverslanir í stað hefðbundna verslana. Tölvurnar sem eru vinsælastar eru Playstation, PC og símar. Leikjategundirnar sem eru vinsælastar eru skotleikir, íþróttaleikir, þrautaleikir, hlutverkaleikir, hasarleikir og sandkassaleikir. Konur eru meira að spila þrautaleiki á símum á meðan karlar eru frekar að spila hinar tegundirnar á Playstation eða PC tölvum

Operational availability of alternate airports in Iceland :analysis of availability and forecasting

For the aviation industry, safety is of utmost importance. To ensure safety the selection of suitable alternate airport is crucial with regards to their location and existing infrastructure. This is crucial for airlines, particularly in Iceland, where rapidly changing weather can significantly impact air transport operations, leading to inconvenience for passengers and increased costs for airlines. This research project marks the initial steps toward addressing the main question which is to predict the unavailability of alternate airport in Iceland within a 48-hour timeframe, specifically with regards to adverse weather conditions. However, due to the unavailability of a dataset with a 48-hour weather forecast, the study is based on the currently available 24-hour weather forecast data. It is imperative to find ways to develop a 48-hour meteorological forecast that incorporate weather phenomena affecting flights, such as cloud ceiling, visibility and wind. The availability ratio was found to be lowest at Akureyri Airport while Reykjavik Airport and Egilsstaðir exhibit availability ratio between 94-100%. Additionally, the analysis reveals that the duration of unavailability at Akureyri Airport is longer compared to other airports in the project. The occurrence of total closure of the four alternate airports in Iceland due to weather is found to be minimal, accounting for only 0,1% of cases. Moreover, three alternate airports remain open 87% of the time in the period studied here and importantly, during the critical arrival hours at Keflavik International Airport between 05:00Z-08:00Z respectively, the availability is around 83%. Interestingly, the findings obtained using a logistic regression model reinforce the conclusion derived from the historical data demonstrating that such model may be used for estimation in future work. They reveal that the highest likelihood lies in accurately predicting the unavailability at Akureyri Airport when the weather conditions outlined in the project (cloud ceiling, visibility and wind) dip below the airport operating minima (AOM). Moreover, it is shown that if unavailability is predicted by the 24-hour weather forecast data, it is most likely to occur precisely 24-hours later with a 1 to 3-hour buffer. Finally, future perspective and recommendations will be presented to guide future projects in addressing the primary research question.Icelandai

The Too-Big-To-Fail Problem: The Case of the Post-Crisis Banking System in Iceland

This thesis aims to assess the issue of too-big-to-fail (TBTF) banks in the Icelandic banking system from 2008 and to the present. It attempts to gauge the extent to which the issue is relevant to the current banking system. TBTF has become a shorthand for, among other things, banks that uninsured creditors expect the government to protect in the case of failure in light of their systemic importance and interconnectedness, as well as the high cost associated with their exit from the market. Such expectations, as well as alternatively the invalidation or vindication of those expectations, have far-reaching implications for financial stability, the broader economy and societal welfare. The implications constitute the TBTF problem. Following an overview of the theoretical framework surrounding the essential features of the TBTF issue, the TBTF problem in the post-crisis banking system in Iceland is assessed both quantitatively and qualitatively. Several sources of moral hazard are identified, including an unbinding blanket guarantee of domestic deposits still outstanding, the existence of an explicit lender of last resort within capital controls, and pre-crisis plans to nationalize and support a significant part of the banking system. An analysis of the banks’ financial statements between 2008 and 2015 reveals several trends that support and contradict the TBTF problem, suggesting that the largest banks are not maximizing the value of their implicit safety net. Trends and approximations consistent with the TBTF hypothesis include increased systemic importance of the three largest banks operating in the banking sector, deposit-funding advantages for the largest banks and greater risk-taking in non-core activities. Contradictory trends include less risk-taking in the banks’ loan portfolios as well as less interconnectedness in the interbank market. An attempt will also be made to harmonize the contradictory quantitative trends with exogenous factors that constrain the banks form maximizing the value of their implicit safety net. The overall result is that the TBTF problem has grown in severity in the post-crisis banking system, despite a steady downsizing of the banking system since the bursting of the banking bubble in October 2008

Hefur bindiskylda Seðlabanka Íslands áhrif á skulda- og hlutabréfamarkaðinn á Íslandi?

Frá árdögum efnahagskreppunnar sem skall á í október 2008 hefur Ísland náð gríðarlegum efnahagsbata. Í kjölfar góðs bata fylgja oft erfiðar og krefjandi ákvarðanir sem þarf að glíma við. Viðtæk fjármagnshöft voru innleidd í nóvember 2008. Vegna mikils vaxtamunar Íslands við önnur ríki myndaðist tækifæri til vaxtamunarviðskipta. Vaxtamunarviðskipti ýta undir óhóflegt fjármagnsinnstreymi sem leiddi af sér þjóðhagslegan og fjármálalegan óstöðugleika. Til þess að stöðva óhóflegt fjármagnsinnstreymi getur Seðlabanki Íslands takmarkað það með beitingu stjórntækja. Umræða um stjórntæki og þjóðhagsvarúð hafa farið vaxandi frá efnahagskreppunni. Í júní 2016 tók Seðlabanki Íslands upp bindiskyldu á fjármagnsinnflæði sem var 40%, síðar 0% í mars 2019. Bindiskyldan leiðir af sér umfangsmikil áhrif á gengi krónunnar og grunnvexti. Tilgangur rannsóknarinnar er að athuga hvort bindiskylda Seðlabanka Íslands hefur áhrif á skulda- og hlutabréfamarkaðinn á Íslandi. Rannsóknin var í formi eigindlegrar rannsóknaraðferðar þar sem tekin voru djúpviðtöl við reynslumikla aðila úr efnahagslífinu. Niðurstöður viðtalana leiddu í ljós ástæður bindiskyldunnar og áhrif hennar á fjármálamarkaði. Bindiskyldan hafði aðallega áhrif á skuldabréfamarkaðinn með lækkandi erlendu innstreymi og ófyrirsjáanleg áhrif á hlutabréfamarkaðinn

Two Phase Flow in Porous Media and the Concept of Relative Permeabilities

New equations for the two phase flow of water and steam are presented. The new equations coincide with those already in use for the case of horizontal flow but are different from those for vertical flow. It is shown that the usual equations can only be valid when the two phases are flowing in separate channels, where the channel dimensions are large compared with the grain size of the porous media, and in such a case the relative permeabilities should vary only slightly with the saturation ratio. It is shown that the actual variation of relative permeabilities with saturation ratio suggests a flow model where the flow channel dimensions are of the same order of magnitude as the grain size. On this basis a new set of equations is proposed, which with the associated flow model explain relative permeabilities qualitatively. In addition they show that water can flow upwards in two phase flow where the pressure gradient is less than hydrostatic. In a simple two phase flow test it is demonstrated that this happens as predicted by the new equation set

The influence of anaerobic muscle activity, maturation and season on the flesh quality of farmed turbot

In order to test seasonal, rearing, maturing and anaerobic muscle activity effect on the flesh quality of turbot (Scophthalmus maximus) a total of 80 farmed turbot from three different strains from reared under natural or continuous light were killed by a percussive blow to the head in November (winter, Icelandic strain), March (spring, Portuguese strain) and June (summer, domesticated strain (France turbot)). To test the effect of anaerobic muscle activity, 10 fish were on each occasion pre rigor filleted, where one fillet was used as a control, while the other fillet was electrically stimulated using a squared 5 Hz, 10 V pulsed DC for 3 min. All pre rigor fillets were measured for pH, weighed, wrapped in aluminum foil and stored in polystyrene boxes with ice. After 7 days of storage the fillets were measured instrumentally for pH, drip loss, colour (CIE L* a* b*) and texture properties such as hardness and shear force, while fillet shrinkage and colour (RBG) were evaluated with computer imaging on photographs from a standard lightbox. Results showed that softness of the flesh was mainly influenced by factors associated with growth, such as season, photoperiod and maturation. Anaerobic muscle activity simulated with electrical stimulation caused an increase in drip loss (\1%) and loss of shear forc

Effect of rearing temperature on flesh quality in Arctic charr (Salvelinus alpinus)

Currently, no information is available on the effect of progressively decreasing temperatures on the sensory quality of Arctic charr. The objective of this study was to investigate if and how different and progressively changing rearing temperatures affect the sensory quality of cooked and raw fillets of Arctic charr. The effects of rearing temperature on the sensory quality of Arctic charr (weight range 622–888 g) were investigated. Rearing temperature was changed during the experimental period as the fish were reared at constant or decreased temperature during October to April and subsequently reared at two constant temperatures from April to August establishing six different rearing temperature combinations. Significant differences were seen in all four main sensory attributes groups, that is odour, appearance, flavour and texture. Freshness characteristics such as sweet odour and flavour, and metallic odour and flavour increased with decreasing rearing temperature, whereas musty odour and flavour decreased. Rearing temperature had a clear effect on the colour of the fillets. Lower rearing temperature increased colour intensity substantially. Softness, juiciness and tenderness increased with decreased rearing temperature. A trend was seen towards more effect from final rearing temperature than initial temperature on the sensory attributes studied. Spoilage characteristics, that is, sour and rancid odour and flavour, and off-odour and flavour were either very weak or not noticeable in all sample groups