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- Bergqvist, Lars, 1976-, et al.
(författare)
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Magnetic and electronic structure of (Ga1-xMnx)As
- 2003
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Ingår i: Physical Review B. Condensed Matter and Materials Physics. - 1098-0121 .- 1550-235X. ; 67:20, s. 205201-
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Tidskriftsartikel (refereegranskat)abstract
- We present theoretical calculations of the magnetic and electronic structure of Mn-doped GaAs (in the zinc-blende structure). The magnetic properties are shown to be very sensitive to structural defects, in particular, As antisite defects and Mn at interstitial positions. Only when considering such defects can the experimental magnetic moments be reproduced by first-principles theory. We present a simple model for understanding the connection between the magnetic ordering and the As antisites, and the way in which the defects help to stabilize a partial disordered local-moment state. The connection between the energetics of the Mn substitution and the As antisite concentration is also analyzed. In addition, we compare the calculated magnetic properties and electronic structures of Mn situated on substitutional sites (Mn replacing a Ga atom) and on interstitial sites, where in agreement with observations the interstitial site is found to be less favorable. Finally, combining our first-principles calculations of the spin-wave excitation energies with a classical Heisenberg Hamiltonian we have calculated interatomic exchange interactions, and using Monte Carlo simulations we present theoretical values of the critical temperature as a function of Mn concentration.
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| 3. |
- Eriksson, Jessica, 1972-
(författare)
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Branschinteraktion och institutionell förändring : Omvandling i två livsmedelsbranscher
- 2004
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Studien tar sin utgångspunkt i de senaste decenniernas trend mot avreglering, marknadsintegration och andra politiska åtgärder som syftar till att skapa bättre förutsättningar för konkurrens. Konkurrens antas skapa dynamik och ge olika positiva effekter såsom innovationer, förnyelse och mångfald. Denna studie belyser hur försöken att skapa mer konkurrens inte bara handlar om att ändra formella regelsystem, eftersom även institutionaliserade normer, olika föreställningar om hur man bör interagera, samt beroenden av olika slag, också påverkar interaktionen. Detta betyder att den institutionella förändringen i branscher, utöver formella regler, är av betydelse för att förstå branschomvandling. Analysen baseras på förändringar i två svenska livsmedelsbranscher. Teoretiskt utgår studien från sociologisk institutionell teori. Studien belyser vad branschinteraktionen betyder för institutionell förändring i branscher genom att lyfta fram fyra förändringsprocesser, institutionalisering, anpassning, experimentering och politisering. Särskilt fokus läggs på hur förändringstryck i form av politiska åtgärder leder till dessa processer. Med hjälp av de fyra processerna kan branschomvandling såväl som institutionell förändring beskrivas. Resonemangen leder vidare fram till en dynamisk paradox. Paradoxen utgår ifrån det välkända behovet av både stabilitet och förändring som grunden för dynamik. Politiska åtgärder handlar ofta om en strävan efter förnyelse och mångfald. Detta leder dock till en situation där olika nya produkter, processer med mera konkurrerar om legitimitet. Denna konkurrens leder till försök att skapa legitimitet för det nya, och därmed reducera osäkerheten, både för de konkurrerande företagen och för konsumenter och andra aktörer, vilket ofta understöds av nya politiska åtgärder. Detta begränsar i sin tur fortsatta utrymmet för experimentering. Det kan därför sägas vara svårt att vidmakthålla en kontinuerlig förnyelse och mångfald i branscher till följd av politiska åtgärder. En annan slutsats som dras är att det är kombinationen av konkurrens och samarbete som är av intresse för att skapa ”önskvärd” dynamik, snarare än konkurrens eller samarbete i sig.
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| 7. |
- Eriksson, Susanne P., 1964
(författare)
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Temporal variations of manganese in the haemolymph and tissues of the Norway lobster, Nephrops norvegicus (L.)
- 2000
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Ingår i: Aquatic Toxicology. - 0166-445X. ; 48:2-3, s. 297-307
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Tidskriftsartikel (refereegranskat)abstract
- The Norway lobster, Nephrops norvegicus, lives on sediments rich in manganese (Mn) and any dissolved Mn2+ can readily be taken up by the animal. To investigate temporal fluctuations of bioavailable Mn, a N. norvegicus fishing ground on the Swedish west coast was repeatedly sampled every 2 months from September 1992 to November 1994. The lobsters collected contained on average 91.7 mu g Mn g(-1) dry wt. (S.E. 4.2, n = 156). The oxygen saturation of the bottom water proved to be negatively correlated with both the temperature of the water and the Mn (concentration and total content) of the animal's haemolymph. The temporal fluctuations in animal Mn load were however, small compared to spatial differences found in an earlier study. There was an increase in the Mn concentration of the lobster exoskeleton (from 56 to 340 mu g Mn g(-1) dry wt, exoskeleton) and gills (from 34 to 160 mu g Mn g(-1) dry wt. gill) in postmoult animals compared to premoult. The Mn concentrations of the lobsters' hepatopancreas and muscle tissue remained relatively constant throughout the moult cycle and appear to be more conservative in their Mn concentration and less affected by exposure to Mn. (C) 2000 Elsevier Science B.V. All rights reserved.
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| 8. |
- Eriksson, Susanne P., 1964
(författare)
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Variations of manganese in the eggs of the Norway lobster, Nephrops norvegicus (L.)
- 2000
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Ingår i: Aquatic Toxicology. - 0166-445X. ; 48:2-3, s. 291-295
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Tidskriftsartikel (refereegranskat)abstract
- The Norway lobster, Nephrops norvegicus, lives on sediments rich in manganese (Mn). Temporal fluctuations of Mn in the eggs of N. norvegicus was investigated, both in the field and in laboratory experiments. Female gonads and external eggs of different developmental stages were measured for Mn. The Mn concentration during oocyte maturation and throughout most of the embryogenesis (after fertilisation) remained stable around 5 mu g Mn g(-1) dry wt. egg. At the end of the embryonic development (about 6 months after fertilisation) the Mn concentration of the egg started to increase and had at the time of hatching reached concentrations of 120 mu g Mn g(-1) dry wt. egg. The egg shell was at this stage highly permeable and Mn was taken up by the embryo and egg shell in equal amounts. (C) 2000 Elsevier Science B.V. All rights reserved.
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| 9. |
- Holmin, Susanne, et al.
(författare)
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Investigation of Electrode Materials as Sensors in a Voltammetric Electronic Tongue
- 2002
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Ingår i: Electroanalysis. - Weinheim, Germany : Wiley-VCH Verlagsgesellschaft. - 1040-0397 .- 1521-4109. ; 14:12, s. 839-847
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Tidskriftsartikel (refereegranskat)abstract
- In this work different electrode materials were investigated as sensors in a voltammetric electronic tongue. Basically, the electronic tongue is based on the combination of nonspecific sensors (electrodes) and pattern recognition tools, for example principal component analysis (PCA). Copper. glassy carbon, nickel, palladium, silver, tin, titanium and zirconium together with more traditional electrode materials such as gold, iridium, and platinum were studied. Cyclic voitammetry was applied to study typical model reactions in solutions containing different electroactive compounds, like ascorbic acid, glucose, histidine and potassium hexacyanoferrate(II). Different sensitivity and selectivity were obtained with the electrodes. Large responses were for example found for the amino acid and the carbohydrate using the copper, nickel and silver electrode. Some of the electrodes were employed in multicomponent solutions, i.e., liquid washing detergents from different suppliers together with differential pulse voltammetry. Responses from the electrodes in combination with PCA showed that they separated the detergents to different extents. This was further used when information from the sensors was merged together for successful discrimination of the detergents. It was found that two detergents close to each other in the score plot were from the same supplier. Furthermore. scanning electron microscopy (SEM) was used to monitor surface changes at the nonnoble electrodes (copper, nickel, and silver).
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| 10. |
- Ledin Eriksson, Susanne
(författare)
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Central-block techniques for reliet of labour pain
- 2004
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Access to effective pain relief is today a natural part of modem obstetrics. When epidurals for relief of labour pain were introduced during the 1970s, local anaesthetics in high concentrations were used. This caused extensive motor block, affecting propulsive ability during second stage, with increased risk of caesarean and instrumental delivery. There has since been substantial improvement in the technique, with reduced doses and the addition of fat-soluble opioids. The present project sought to investigate and improve techniques concerning central blocks for of labourpain relief. Dose study: The side-effects of sufentanil are mainly pruritis and sedation. In high doses it has negative effects on the new-born, and it was important to find the lowest effective dose. In a prospective doubleblind study 243 patients were randomised to sufentanil 0.5, 0.75 and 1 µg/mI respectively, in combination with bupivacaine. The analgesic effect was similar in the three groups. While no lowest possible dose was found, the study showed no reason to exceed 0.5 µg/ml in this setting. PCEA study: Patient controlled epidural analgesia, PCEA, is an attractive method in obstetrics, where individual drug requirement varies widely. Some studies show lower drug-consumption when using PCEA than compared to continuous epidural infusion, CEI. We investigated whether this was true for an ultra-low-dose regimen. In a prospective randomised study 80 parturients used ropivacaine 1 mg/ml with sufentanil 0,5 µg/ml, in PCEA, 4 mI bolus dose and 20 minutes lockout, or CEI, 6 ml/hour. Extra dosing was permitted to the same possible maximum dose, 12 ml/hour. The PCEA group used 33 % less drug totally and 25% less drug per hour than the CEI group. Both groups had equally satisfactory analgesia and there was no difference in side-effects. Spinal study: Epidural analgesia is less effective during second stage and has a rather slow onset. Therefore - and also because of the higher risk for accidental dural puncture in this situation - clinicians may hesitate to perform an epidural if the parturient is entering second stage. Spinal analgesia has a quick onset and a profound analgesic effect when used in combination with epidural. Our descriptive study investigated whether singleshot spinal analgesia is a possible alternative when an epidural is less suitable. Forty multiparae with a rapid labour course, who in late labour requested effective analgesia, received spinal analgesia with sufentanil 7.5 µg and bupivacaine 2 mg. Analgesia was rapid and effective. Seventy-seven percent of the parturients rated the method as excellent. Side effects such as hypotension and pruritis were more pronounced than with low dose epidurals, but easily managed. Active obstetric management is necessary since the duration of block is limited. The obstetrician has to be aware of the risk of a non-reassuring foetal heart rate episode following spinal block. Population study: There is disagreement whether epidural analgesia affects obstetric outcome. Early studies showed an increase in caesarean and instrumental deliveries when using epidurals. The issue is complex and clinical studies have had problems with selection bias, cross-over and study size. Large studies have shown that low-dose epidurals have less impact on obstetric outcome than traditional epidurals do. We used the Swedish Medical Birth Register in a population-based study of 94,217 nulliparae who gave birth 1998-2000. The frequencies of epidural block in this population were estimated for each delivery unit. The outcomes studied were non-elective caesarean section and instrumental delivery. Delivery units with the lowest (20-29%) and the highest (60-64%) relative frequencies of epidural block had the lowest proportion of caesarean section (9. 1 %). For the other groups the proportion varied between 10.3 % and 10.6%. Instrumental deliveries were most common, 18.8%, in delivery units with 50-59% frequency of epidural block use. The lowest incidence (14.1%) was seen in units using epidurals in 30-39%. In the other groups (20-29%, 4049% and 60-64%) the proportion varied between 15.3 and 15.7 %. There is no association between epidural use and caesarean section and no clear tendency relating epidural use to instrumental delivery. It is not reasonable to abstain from epidural analgesia in pain relief during childbirth with the intention of reducing caesarean section rate.
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| 13. |
- Spicer, J. I., et al.
(författare)
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Does the development of respiratory regulation always accompany the transition from pelagic larvae to benthic fossorial postlarvae in the Norway lobster Nephrops norvegicus (L.)?
- 2003
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Ingår i: Journal of Experimental Marine Biology and Ecology. - 0022-0981. ; 295:2, s. 219-243
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Tidskriftsartikel (refereegranskat)abstract
- The ability to regulate O-2 uptake during exposure to acutely declining PO2S co-occurred with metamorphosis from a planktonic to a benthic existence in the Norway lobster Nephrops norvegicus when cultured under normoxic conditions in the laboratory. The onset of this regulation appears to be related to the presence of a hypoxia-related hyperventilation of extrabranchial exchange surfaces (telson/uropods) by the pleopods and a shift from a low to a high He O-2 affinity. This co-occured with a dramatic calcification of the exoskeleton at metamorphosis, which will restrict gas exchange over the general body surface. Evidence marshalled here points to a shift from a pleopod-based, hypoxia-related, hyperventilation of the uropods/telson as gas exchange surfaces to, in later postlarval stages, a scaphognathitc-based response, where the gills are the main areas for gas exchange. This is the first time that experimental evidence has been put forward for the use of uropods/telson by larval lobsters as extrabranchial gas exchange surfaces. Pre-exposure of larval and postlarval N. norvegicus to reduced P-O2, both in the laboratory and in the field, resulted in the "adult" pattern of M-O2, regulation present during exposure to declining P-O2 being established before metamorphosis. Bringing the ontogeny of this regulation forward in the development itinerary was to some extent a result of a shift from a low to a high He O-2 affinity well before metamorphosis and an increase in the magnitude of the hypoxia-related hyperventilatory response in the planktonic larval stages. Thus, the development of respiratory regulation does not always accompany the transition from pelagic larvae to benthic fossorial larvae in N. norvegicus as its onset can be influenced prevailing O-2 conditions, both in the laboratory and the field. (C) 2003 Elsevier B.V. All rights reserved.
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