Ground state structure, domain walls, and external field response in random magnets

The ground state structure and domain walls in Ising-like magnets with quenched randomness are studied at zero temperature. The methods employed are exact ground state calculations using graph-theoretical optimization and extreme statistics arguments. The elastic manifolds, i.e., domain walls, with random-bond disorder are investigated with two different types of periodicity. The first type of periodicity is when the randomness is periodically repeated. It is shown to lead after a cross-over to the periodic elastic media universality class, whenever the period lambda is finite. The second periodicity is due to an additional modulating potential. There are two types of intermittence seen before the asymptotic random-bond roughness behavior is reached. The first type is when the manifolds jump between the minima of the periodic potential and the second type is when the interfaces roughen over pinning energy barriers. An external field is applied to the random manifolds. An energy minimization argument based on the glassy energy landscape indicates that in an equilibrium system the manifolds move by sharp jumps between nearly degenerate energy minima in analogy to a first-order transition. A mean field argument for the finite-size scaling of the first jump field is derived and numerically confirmed. Using extreme statistics and probabilistic arguments, the probability distribution of the first jump field and its finite size scaling are calculated. Based on these the susceptibility of the manifolds is derived. Random field magnets are studied in two dimensions. The break-up of long-range order is shown to have a first-order character. The domain wall behavior is studied, leading to an interface scaling with a roughness exponent greater than unity below the break-up length scale. The domain wall energy is demonstrated to vanish logarithmically confirming the destruction of the long-range order. The magnetization and susceptibility versus the external field are investigated, and they show continuous behaviors and are independent of the break-up length scale. However, another long-range order, percolation, is found in two-dimensional random field magnets. The percolation transition with respect to the external field belongs to the standard short-range correlated two-dimensional percolation universality class. The whole phase diagram for percolation as a function of the random field strength and the external field is predicted.reviewe

Weed seed predation by carabids and rodents in arable land in Europe

Ogräs orsakar idag stora skördeförluster och ogräs har utvecklat resistens mot 23 av 26 kända verkningsplatser för herbicider. Ogräspredatorer så som jordlöpare och gnagare bidrar med en viktig ekosystemtjänst genom att konsumera ogräsfrön efter att de släppts från växten, och de kan därmed reducera fröbanken och reglera ogräspopulationerna. Ogräspredation har potential att bli en viktig del i bekämpningen av ogräs i åkermarker, men ogräspredationen kan variera mycket. Den här litteraturstudien diskuterar därför effekten av jordlöpares och gnagares ogräspredation i Europa och faktorer som påverkar ogräspredationen. Vissa arter av jordlöpare och gnagare har större betydelse för ogräspredationen. Ogräspredationen skiljer sig även åt mellan olika ogräsarter där faktorer så som storlek och energiinnehåll kan påverka ogräspredatorers preferens av frön. Jordbruksåtgärder så som jordbearbetning och besprutning med kemiska bekämpningsmedel kan ha en negativ påverkan på ogräspredationen, medan god planering av åtgärder och tillgång på skyddande vegetation gynnar ogräspredatorer. Vissa främjande åtgärder kan vara svåra att kombinera, men om man som lantbrukare redan följer riktlinjerna för IPM bör främjandet av ogräspredation passa in i den befintliga verksamheten.Weeds is a major cause for crop yield losses and have developed resistance to 23 of 26 known herbicide sites of action. Weed seed predators such as carabids and rodents provide an important ecosystem service by consuming weed seeds after the seeds have been dispersed, and they can thus reduce the seed banks and regulate weed populations. Weed seed predation has the potential to become an essential part of weed control. However, weed seed predation can vary substantially. This review therefore discusses the impact of carabids and rodents on weed seed predation in Europe and factors that determines the predation levels. Some species of carabids and rodents play a bigger part in weed seed predation than others. The weed seed predation also differs between weed species and factors such as seed size and energy content influence predator’s preference for different seeds. Agricultural management practices such as tillage and pesticide applications have a negative effect on weed seed predation, whereas proper planning of management practices and access to vegetation cover have a positive effect. Practices that have a positive effect on weed seed predation can sometimes be hard to combine, facilitating weed seed predation should however fit in with existing practices for farmers who follow IPM guidelines

Effects of diversified cropping on arthropod communities

Även intensiva moderna jordbruk är beroende av ekosystemtjänster som organismer bidrar med såsom biologisk bekämpning av skadedjur. Effekten av biodiversitet på ekosystemprocesser förklaras inte i tillräcklig grad av taxonomisk mångfald, utan beror snarare på mångfalden av funktionella egenskaper bland arterna. I den här studien undersöks effekten av diversifierad odling i form av tillförsel av organiskt gödselmedel och införandet av vall i växtföljden, samt olika tidpunkter för provtagning under säsongen, på proportionerna av jordlöpare (Carabidae) och spindlars (Araneae) funktionella egenskaper på fältnivå. Jordlöpare och spindlar samlades in från tre behandlingar, mineralgödsel med en annuell växtföljd, organisk gödsel med en annuell växtföljd och organisk gödsel med vall i växtföljden, över 19 fält i Halland samt tre tidpunkter för provtagning, maj, juni och juli. De funktionella egenskaper hos jordlöpare som undersöktes var jordlöpares diet, uppdelat i köttätare, allätare och växtätare (i huvudsak fröätare), vingmorfologi, uppdelat i vingade och dimorfa, d.v.s. kan både ha vingar och vara vinglösa, samt community weighted mean (CWM) kroppsstorlek. De funktionella egenskaper hos spindlar som undersöktes var jaktmetod, uppdelat i aktivt jagande och mattvävsspindlar, samt CWM kroppsstorlek. Proportionerna av köttätande och dimorfa jordlöpare ökade i behandlingen med vall i växtföljden, medan växtätande och vingade jordlöpare minskade i behandlingen med vall i växtföljden. Proportionerna av spindlars jaktmetoder samt CWM kroppsstorlek av spindlar och jordlöpare påverkades inte av behandlingarna. Proportionen av växtätare och CWM kroppsstorleken av jordlöpare ökade över säsongen. Proportionen av köttätande och dimorfa jordlöpare samt mattvävsspindlar var lägre under juni jämfört med maj och juli, medan proportionerna av allätande och vingade jordlöpare samt aktivt jagande spindlar samt spindlars CWM kroppsstorlek minskade under juni. En högre proportion av köttätare till följd av införandet av vall i växtföljden och organisk gödsel, kan leda till starkare biologisk bekämpning av skadeinsekter. En hög proportion av köttätare samt en högre CWM kroppsstorlek kan dock även innebära en ökad risk för predation av jordlöpare på spindlar. Vad som avgör sammansättningen av egenskaper samt hur dessa påverkar ekosystemtjänster är komplext och mer forskning i ämnet behövs.Highly intensified modern agriculture remains dependent on species-mediated ecosystem services such as pest control. Taxonomic diversity does not sufficiently explain biodiversity effects on ecosystem processes but rather depend on the diversity of functional traits among species. In this study the effect of cropping diversification, such as added organic amendments in the form of manure and incorporation of ley in the crop rotation, as well as the effect of time of sampling during the season on the proportions of carabid (Carabidae) and spider (Araneae) functional traits was investigated. Carabids and spiders were sampled across 19 fields in Halland county, Sweden, with three different diversification treatments, mineral fertilizer with an annual crop rotation, manure with an annual crop rotation, and manure with ley incorporated in the crop rotation, as well as three sampling sessions, early, mid, and late cropping season. The carabid functional traits diet, divided into carnivores, omnivores and phytophagous (mainly seed eaters) carabids, wing morphology divided into macropterous and dimorphic, and community weighted mean (CWM) body size were studied. The spider functional traits studied were hunting mode divided into ground runners and sheet-web weavers, and CWM body size. The proportion of carnivorous and dimorphic carabids increased with ley in the crop rotation whereas phytophagous and macropterous carabids decreased. No treatment effect was found on spiders hunting mode or on CWM body size of carabids or spiders. Phytophagous and CWM body size of carabids increased during the season. Carnivores and dimorphic carabids, as well as sheet-web weaving spiders were lower in June compared with May and July. In contrast, the proportion of omnivorous carabids, macropterous carabids, ground runners and spiders CWM body size was higher in June compared with May and July. Adding organic amendments such as manure and ley in the crop rotation, and thereby increasing the proportion of carnivores could lead to a stronger biological pest control. A higher proportion of predators and a higher CWM body size of carabids could however also increase the risk of intraguild predation. What determines the composition of traits and how that in turn affects ecosystem services is complex and more research is needed

Feeding routines and prevalence of overweight horses in Norway

Background: Over the latest years feeding recommendations for horses have changed continuously. The minimum recommendations for forage intake have increased, and ad libitum feeding is encouraged to ensure welfare and health of horses. However, a higher forage intake might result in higher energy intake for the horse. When body condition scoring horses, the prevalence of obesity ranges from 21 to 62% in Scandinavia, Great Britain and the USA. Obesity in horses may lead to health problems and supress animal welfare. Little is known about the body condition score (BCS) of horses in Norway, feeding routines and the percentage of imported horse feeds in Norway. Aim: The aim of this study was to investigate feeding routines and the prevalence of overweight horses (BCS>6) in Norway. Materials and methods: In this thesis, a cross-sectional study of 424 horses was conducted. The horses were body condition scored (Kohnke, 1992) and body weight was measured on a weight scale (n=398/424). The horses (n=424) consisted of 144 horses studied at the Equine Hospital at NMBU and 280 horses at private stables in the field. Information about the horses’ gender, age, breed, use, and health status was collected. The total number of horses studied consisted of 219 geldings, 158 mares and 37 stallions, with ages ranging from 6 months to 29 years. In addition, 266 out of the 424 horses’ and 18 owners of horses who was not body condition scored answered a questionnaire about feeding routines of their horses. Results: Ninety percent of the horses in the present study were fed Norwegian produced forage. Horses fed imported forage had a lower BCS than horses fed self-produced forage, and 90% of horses fed imported forage were competition trotters. In addition to forage, 68% of the horses were fed concentrate from Norwegian manufacturers only. The origin of concentrate did not affect the BCS, neither the type of forage fed. The prevalence of overweight horses in Norway, with a BCS over 6, was 47%. There were no underweight horses (BCS under 4) in the present study. Gender, age, breed, activity, health, and use affected the horses BCS. Horses with teeth or jaw injuries had the biggest effect on BCS, followed by the horses’ breed. Conclusion: In conclusion, most of the horse feed in Norway is Norwegian produced or from Norwegian manufacturers, and the prevalence of overweight horses investigated in the present study was 47%

Two Problems on Divisor Functions

Abstract Not Provided

The study of two genes involved in the maintenance of intracellular redox potentials in Thiobacillus ferrooxidans

Bibliography: p. 128-155.The thioredoxin and ϒ-glutamylcysteine synthetase genes of Thiobacillus ferrooxidans were isolated by complementation of an Escherichia coli trxA gshA double mutant for growth on minimal medium lacking glutathione. Transduction of a T. ferrooxidans genome cos mid library into the E. coli mutant resulted in the identification of two groups of complementing cosmids. One of these groups was able to complement the TrxA⁺ requirement of an E. coli trxA met mutant for conversion of methionine sulfoxide to methionine. The nucleotide sequence of a 1.1 kbp Hindiii-Psti T.ferrooxidans chromosomal DNA fragment containing the cloned trxA gene, was determined. An open reading frame (ORF) corresponding to the thioredoxin gene and part of an ORF corresponding to the N-terminal region of the rho gene were identified. A 14 kDa protein corresponding to the T. ferrooxidan thioredoxin was synthesised in an E. coli-derived in vitro transcription/translation system. The predicted amino acid sequence of the T.ferrooxidans trxA gene showed 70.6% identity to that of E. coli. The cloned T. ferrooxidans trxA gene was able to support T7 phage replication in an E. coli trxA mutant to almost the same level as a TrxA⁺ wild type strain. However, it was not able to satisfy the thioredoxin requirement of M13 phage. Crude extracts of the E. coli trxA gshA mutant containing the cloned T. ferrooxidans trxA gene were able to reduce insulin far more rapidly those that did not contain the cloned gene, indicating that the T.ferrooxidans thioredoxin has disulfide reductase activity. DNA:RNA hybridisation analysis was carried out on transcripts prepared from the E. coli trxA gshA double mutant, the mutant containing the cloned trxA gene and T. ferrooxidans cells. A single transcript of about 0.5 kbp was obtained for RNA from T. ferrooxidans cells. Several transcripts were produced from the cloned T. ferrooxidans trxA gene in E. coli. One of these transcripts corresponded in size to the 0.5 kbp transcript produced by T. ferrooxidans cells, whereas the other transcripts were larger (1.35, 1.40, 1.60 and 1.80 kbp) and presumably represented transcription products originating from the lac promoter of the vector. Primer extension analysis of the thioredoxin gene with RNA prepared from T. ferrooxidans gave three transcription start sites. RNA derived from the cloned trxA gene in E. coli only gave two transcription start sites, which were identical to two of the three found with T. ferrooxidans RNA. The second group of cosmids which was able to complement the gshA trxA double mutant for growth on minimal media but which did not allow growth of the E. coli trxA met mutant on minimal media plus methionine sulfoxide was also examined. The nucleotide sequence of a 2.3 kbp Clai-BamHI T. ferrooxidans chromosomal DNA fragment containing the complementing DNA, was determined. Two ORFs, separated by 9 bp, corresponding to a citrate synthase gene and a ϒ-glutamylcysteine synthetase gene were identified. The predicted amino acid sequence of the T. ferrooxidans gltA gene showed 37% identity to that of E. coli, whereas the predicted amino acid sequence of the T. ferrooxidans gshA gene only showed 18% identity to that of E. coli. The low homology of the gshA gene products is not abnormal, as the ϒ-glutamylcysteine synthetases studied to date differ widely in amino acid sequence and structure. Partial sequencing of the cloned T. ferrooxidans chromosomal DNA upstream of the gltA gene indicated regions of homology to the genes of the pyruvate dehydrogenase complex. Synthesis of proteins corresponding to the T. ferrooxidans citrate synthase (43 kDa) and ϒ-glutamylcysteine synthetase (49 kDa) enzymes were confirmed using an E. coli-derived in vitro transcription/translation system. The identity of the proposed citrate synthase gene was confirmed by complementation of an E. coli gltA mutant. Similarly, the DNA upstream of the gltA gene, was found to complement an E. coli mutant for the pyruvate dehydrogenase complex, confirming that this region contained the T. ferrooxidans pyruvate dehydrogenase complex, as predicted from the partial sequence analysis. The identity of the T. ferrooxidans ϒ-glutamylcysteine synthetase gene was confirmed by determining the levels of glutathione in crude extracts of the E. coli gshA trxA double mutant, the mutant containing the cloned T. ferrooxidans gshA gene, and an E. coli parental strain. Crude extracts prepared from E. coli double mutant contained much lower levels of glutathione than crude extracts prepared from the E.coli mutant containing the cloned gshA gene, indicating that the gene from T. ferrooxidans encoded a protein with ϒ-glutamylcysteine synthetase activity. RNA:DNA hybridisation analysis was carried out using probes specific to the gshA gene, the gltA gene and the aceF gene (pyruvate dehydrogenase transacetylase gene). All three probes gave transcripts of 9 kbp and a number of smaller transcripts with RNA derived from T. ferrooxidans cells. The 9 kbp transcripts indicated transcriptional linkage of the y- glutamylcysteine synthetase gene, the citrate synthase gene and the genes of the pyruvate dehydrogenase complex in T.ferrooxidans

De enkelte lands reindrift - Norge

The reindeer husbandry in Norway from the view of the chairman of NRL

Molecular biology of the Oleosin gene family of Brassica napus

Oilseed rape (Brassica napus) is a valuable oil producing crop plant. Oil is produced by developing seeds and constitutes 45% of the dry seed weight. Storage oil is deposited as triacylglycerol in spherical structures called oil bodies. These are coated by a phospholipid monolayer interspersed with proteins called oleosins, which serve as emulsifiers, retaining the integrity of individual oil bodies. In this project the oleosin gene family of B. napus was studied. Sequence information was obtained on two oleosin cDNA clones and a genomic clone was also isolated. The sequences for oleosins from B. napus were compared with those isolated from other plant species. Preliminary expression studies were carried out, relating the timing of oleosin mRNA and protein production to the stages of embryo development. These results give an indication of the importance of transcriptional and post-transcriptional processes in the control of oleosin expression