Carbide precipitation in a low alloyed steel during aging studied by atom probe tomography and thermodynamic modeling

Carbide precipitation in martensitic low alloyed steels contributes to the mechanical properties through precipitation hardening. A high number density of carbides is desired to maximize the hardening effect, which is achieved through the precipitation of carbides on the dislocations in the martensitic structure. In this study, the nucleation, growth, and coarsening of vanadium and molybdenum carbides during aging at 600◦C for periods up to four weeks were investigated. The work covers characterization with atom probe tomography, which showed that the nucleation of V and Mo rich MC/M2C carbides takes place on dislocations. The growth of these carbides proceeds by the diffusion of elements to the dislocations, which has been modeled using Dictra software, confirming the rate of the reaction as well as the depletion of carbide formers in the matrix. For longer aging times, particle coarsening will decrease the number density of particles with a transition from dislocation-based carbides to separate rounded carbides

Svenska europaparlamentariker vänder hemåt - En teoriprövande studie om svenska europaparlamentarikers nationella partilojalitet

Vi har valt att ägna vår uppsats åt de svenska europaparlamentarikerna. Utgångspunkten för vårt arbete är en B-uppsats från 2001 som handlar de svenska EU-parlamentarikernas inställning till transnationellt partisamarbete. Vi gör en teoriprövande studie av deras uppsats. Vi har med hjälp av litteratur på området lättare kunnat förstå de redan existerande teorier om transnationellt partisamarbete och europaparlamentet samt dess parlamentariker. Vår uppsats kärna är den enkät vi låtit våra svenska parlamentariker från den nuvarande samt den förra mandatperioden svara på. Det vi kommit fram till i denna uppsats är att den nationella partipiskan biter minst lika hårt vare sig man som europaparlamentariker är kritisk eller positiv till EU. Utifrån våra resultat ser vi inte att EU-positiva parlamentariker är mer benägna att bryta mot sin nationella partilinje än EU-kritiska. Detta strider mot den teori vi prövar. Utöver detta har vi även valt att lyfta fram ett par områden där vår enkätundersökning resulterade i intressanta svar

Evolution of iron carbides during tempering of low-alloy tool steel studied with polarized small angle neutron scattering, electron microscopy and atom probe

The magnetic scattering of iron carbides in low-alloy tool steel was investigated ex-situ by polarized small angle neutron scattering measurements after tempering the steel at 550 \ub0C and 600 \ub0C. Magnetic features could be detected in the as-quenched sample resulting in a negative interference term, believed to be either θ-Fe3C, η-Fe2C, or ε-Fe2-3C. During tempering the evolution of cementite could be studied by the variation of the interference term and in γ-ratio, which is the ratio of the magnetic to nuclear scattering length density contrast. From scanning transmission electron microscopy (STEM) and atom probe tomography, it is evident that cementite (θ-Fe3C) is present directly when reaching the tempering temperature of either 550 \ub0C or 600 \ub0C. At longer tempering times, cementite gets enriched with substitutional elements like chromium and manganese, forming an enriched shell on the cementite particles. STEM and energy dispersive x-ray spectrometry show that the chemical composition of small cementite particles approaches that of Cr-rich M7C3 carbides after 24 h at 600 \ub0C. It is also seen that small non-magnetic particles precipitate during tempering and these correspond well with molybdenum and vanadium-rich carbides

Tracheo-carinal reconstructions using extrathoracic muscle flaps

Objectives: Prospective evaluation of tracheo-carinal airway reconstructions using pedicled extrathoracic muscle flaps for closing airway defects after non-circumferential resections and after carinal resections as part of the reconstruction for alleviation of anastomotic tension. Methods: From January 1996 to June 2006, 41 patients underwent tracheo-carinal airway reconstructions using 45 extrathoracic muscle flaps (latissimus dorsi, n=25; serratus anterior, n=18; pectoralis major, n=2) for closing airway defects resulting from (a) bronchopleural fistulas (BPF) with short desmoplastic bronchial stumps after right upper lobectomy (n=1) and right-sided (pleuro) pneumonectomy (n=13); (b) right (n=9) and left (n=3) associated with partial carinal resections for pre-treated centrally localised tumours; (c) partial non-circumferential tracheal resections for pre-treated tracheal tumours, tracheo-oesophageal fistulas (TEF) and chronic tracheal injury with tracheomalacia (n=11); (d) carinal resections with the integration of a muscle patch in specific parts of the anastomotic reconstruction for alleviation of anastomotic tension (n=4). The airway defects ranged from 2×1cm to 8×4cm and involved up to 50% of the airway circumference. The patients were followed by clinical examination, repeated bronchoscopy, pulmonary function testing and CT scans. The minimum follow-up time was 6 months. Results: Ninety-day mortality was 7.3% (3/41 patients). Four patients (9.7%) sustained muscle flap necrosis requiring re-operation and flap replacement without subsequent mortality, airway dehiscence or stenosis. Airway dehiscence was observed in 1/41 patients (2.4%) and airway stenosis in 1/38 surviving patients (2.6%) responding well to topical mitomycin application. Follow-up on clinical grounds, by CT scans and repeated bronchoscopy, revealed airtight, stable and epithelialised airways and no recurrence of BPF or TEF in all surviving patients. Conclusions: Tracheo-carinal airway defects can be closed by use of pedicled extrathoracic muscle flaps after non-circumferential resections and after carinal resections with the muscle patch as part of the reconstruction for alleviation of anastomotic tensio

Survey of the pine wood nematode (PWN) Bursaphelenchus xylophilus in Norway 2003

In this survey of 2003, 600 samples were collected from 96 forest blocks in the counties of Aust-Agder and Vest-Agder in southern Norway. The sampling activity involved 19 municipalities situated mainly within the two zone sites D and E close to Kristiansand and Arendal. Samples from Scots pine (Pinus sylvestris) formed 92%, while samples of Norway spruce (Picea abies) made up 8% of the total sample volume. Timber and forest debris was the most common objects sampled. Ninety-eight percent of the samples, regardless of tree species, showed signs of Monochamus activity. Nematodes were common and occurred in 90% of the samples analysed. Eight samples of pinewood were positive for the genus Bursaphelenchus. This genus did not occur in spruce. Bursaphelenchus mucronatus was detected in 6 samples of forest debris of pine attacked by Monochamus and collected in the county of Aust-Agder. In the municipality of Evje and Hornes B. mucronatus was detected at Skjerkelia and Sutestad. In the municipality of Froland the nematode was found in two samples from Budalsfjellet, and in one sample from Mjålandsvatn. In the municipality of Birkenes one sample from Vågsdalen contained B. mucronatus. This is the fourth report on the occurrence of B. mucronatus in Norway. The pine wood nematode Bursaphelenchus xylophilus was not detected.Survey of the pine wood nematode (PWN) Bursaphelenchus xylophilus in Norway 2003publishedVersio

Carbide Precipitation during Processing of Two Low-Alloyed Martensitic Tool Steels with 0.11 and 0.17 V/Mo Ratios Studied by Neutron Scattering, Electron Microscopy and Atom Probe

Two industrially processed low-alloyed martensitic tool steel alloys with compositions Fe-0.3C-1.1Si-0.81Mn-1.5Cr-1.4Ni-1.1Mo-0.13V and Fe-0.3C-1.1Si-0.81Mn-1.4Cr-0.7Ni-0.8Mo-0.14V (wt.%) were characterized using small-angle neutron scattering (SANS), scanning electron microscopy (SEM), Scanning transmission electron microscopy (STEM), and atom probe tomography (APT). The combination of methods enables an understanding of the complex precipitation sequences that occur in these materials during the processing. Nb-rich primary carbides form at hot working, while Fe-rich auto-tempering carbides precipitate upon quenching, and cementite carbides grow during tempering when Mo-rich secondary carbides also nucleate and grow. The number density of Mo-rich carbides increases with tempering time, and after 24 h, it is two to three orders of magnitude higher than the Fe-rich carbides. A high number density of Mo-rich carbides is important to strengthen these low-alloyed tool steels through precipitation hardening. The results indicate that the Mo-rich secondary carbide precipitates are initially of MC character, whilst later they start to appear as M2C. This change of the secondary carbides is diffusion driven and is therefore mainly seen for longer tempering times at the higher tempering temperature of 600◦C

Survey of the pine wood nematode (PWN) Bursaphelenchus xylophilus in Norway 2002

In this survey of 2002, 600 samples were collected from 83 forest blocks in the counties Akershus, Buskerud, Oppland and Østfold. The sampling activity involved 16 municipallities situated mainly within the three zone sites A, B, and C. Samples from Scots pine (Pinus sylvestris) formed 89%, while samples of Norway spruce (Picea abies) made up 10% of the total sample volume. Timber and forest debris were the most common objects sampled. Sixty-five percent of the pine samples and 81% of the spruce samples showed signs of Monochamus activity. Nematodes were common and occurred in 94% of the samples analysed. Thirteen samples of pinewood were positive for the genus Bursaphelenchus. Bursaphelenchus mucronatus was recorded for the third time in Norway, and was detected in forest debris attacked by Monochamus at Bjørdalen in the municipality of Eidsberg in the county of Østfold. The pine wood nematode Bursaphelenchus xylophilus was not detected in this survey.Survey of the pine wood nematode (PWN) Bursaphelenchus xylophilus in Norway 2002publishedVersio

Generation of a tumor- and tissue-specific episomal non-viral vector system

Background: A key issue for safe and reproducible gene therapy approaches is the autologous and tissue-specific expression of transgenes. Tissue-specific expression in vivo is either achieved by transfer vectors that deliver the gene of interest into a distinct cell type or by use of tissue-specific expression cassettes. Here we present the generation of non-viral, episomally replicating vectors that are able to replicate in a tissue specific manner thus allowing tissue specific transgene expression in combination with episomal replication. The episomal replication of the prototype vector pEPI-1 and its derivatives depends exclusively on a transcription unit starting from a constitutively active promoter extending into the scaffold/matrix attachment region (S/MAR). Results: Here, we exchanged the constitutive promoter in the pEPI derivative pEPito by the tumor specific alpha fetoprotein (AFP) or the muscle specific smooth muscle 22 (SM22) promoter leading to specific transgene expression in AFP positive human hepatocellular carcinoma (HUH7) and in a SM22 positive cell line, respectively. The incorporation of the hCMV enhancer element into the expression cassette further boosted the expression levels with both promoters. Tissue specific-replication could be exemplary proven for the smooth muscle protein 22 (SM22) promoter in vitro. With the AFP promoter-driven pEPito vector hepatocellular carcinoma-specific expression could be achieved in vivo after systemic vector application together with polyethylenimine as transfection enhancer. Conclusions: In this study we present an episomal plasmid system designed for tissue specific transgene expression and replication. The human AFP-promoter in combination with the hCMV enhancer element was demonstrated to be a valuable tissue-specific promoter for targeting hepatocellular carcinomas with non-viral gene delivery system, and tissue specific replication could be shown in vitro with the muscle specific SM22 promoter. In combination with appropriate delivery systems, the tissue specific pEPito vector system will allow higher tissue-specificity with less undesired side effects and is suitable for long term transgene expression in vivo within gene therapeutical approaches