Femtosecond optical reflectivity measurements of lattice-mediated spin repulsions in photoexcited LaCoO3 thin films

We present results on the temperature dependence of ultrafast electron and lattice dynamics, measured with pump-probe transient reflectivity experiments, of an epitaxially grown LaCoO3 thin film under tensile strain. Probing spin-polarized transitions into the antibonding e(g) band provides a measure of the low-spin fraction, both as a function of temperature and time after photoexcitation. It is observed that femtosecond laser pulses destabilize the constant low-spin fraction (similar to 63%-64%) in equilibrium into a thermally activated state, driven by a subpicosecond change in spin gap Delta. From the time evolution of the low-spin fraction, it is possible to disentangle the thermal and lattice contributions to the spin state. A lattice mediated spin repulsion, identified as the governing factor determining the equilibrium spin state in thin-film LaCoO3, is observed. These results suggests that time-resolved spectroscopy is a sensitive probe of the spin state in LaCoO3 thin films, with the potential to bring forward quantitative insight into the complicated interplay between structure and spin state in LaCoO3

Forskningsprogram för ett kulturarvsvetenskapligt institut

Varje förslag till forskningsprogram innebär någon form av inriktning. I denna text ligger fokus på kulturarvets plats i samhället i vid mening. Det handlar om hur företeelser, berättelser, föremål och platser produ¬ceras och används som kulturarv men också vilka kontaktytor som finns till andra politiska och sociala verksamhetsfält. Forskningsprogrammet har en betoning på möten mellan kulturarv och välfärdsfrågor i vår tid samt vilka former och uttryck detta tar. De centrala frågorna berör möten mellan det officiella kulturarvsfältet och medborgare, som enskilda eller som grupperingar, samt de inrikt¬nings- och legitimi¬tets¬processer som då aktualiseras. Forsknings¬programmet lägger också stor vikt vid mediala och utominstitutionella kulturarviseringsprocesser. Vi pläderar här genomgående för forskning med avstamp i vår samtid, med starka inslag av historiska och internationella komparationer

Enzymatic lignocellulose hydrolysis: Improved cellulase productivity by insoluble solids recycling.

BACKGROUND: It is necessary to develop efficient methods to produce renewable fuels from lignocellulosic biomass. One of the main challenges to the industrialization of lignocellulose conversion processes is the large amount of cellulase enzymes used for the hydrolysis of cellulose. One method for decreasing the amount of enzyme used is to recycle the enzymes. In this study, the recycle of enzymes associated with the insoluble solid fraction after the enzymatic hydrolysis of cellulose was investigated for pretreated corn stover under a variety of recycling conditions. RESULTS: It was found that a significant amount of cellulase activity could be recovered by recycling the insoluble biomass fraction, and the enzyme dosage could be decreased by 30% to achieve the same glucose yields under the most favorable conditions. Enzyme productivity (g glucose produced/g enzyme applied) increased between 30 and 50% by the recycling, depending on the reaction conditions. While increasing the amount of solids recycled increased process performance, the methods applicability was limited by its positive correlation with increasing total solids concentrations, reaction volumes, and lignin content of the insoluble residue. However, increasing amounts of lignin rich residue during the recycle did not negatively impact glucose yields. CONCLUSIONS: To take advantage of this effect, the amount of solids recycled should be maximized, based on a given processes ability to deal with higher solids concentrations and volumes. Recycling of enzymes by recycling the insoluble solids fraction was thus shown to be an effective method to decrease enzyme usage, and research should be continued for its industrial application

Differences in substrate use efficiency: impacts of microbial community composition, land use management, and substrate complexity

Microbial substrate use efficiency is an important property in process-based soil organic matter models, but is often assumed to be constant in mechanistic models. However, previous studies question if a constant efficiency is appropriate, in particular when evaluating carbon (C) cycling across temperatures and various substrates. In the present study, we evaluated the relation between substrate use efficiency, microbial community composition and substrate complexity in contrasting long-term management regimes (47-49 years of either arable, ley farming, grassland, or forest systems). Microbial community composition was assessed by phospholipid fatty acid analysis and three indices of substrate use efficiencies were considered: (i) thermodynamic efficiency, (ii) calorespirometric ratio, and (iii) metabolic quotient. Three substrates, d-glucose, l-alanine, or glycogen, varying in complexity, were added separately to soils, and heat production as well as C mineralization was determined over a 32-h incubation period at 12.5 A degrees C. Microbial communities from forest systems were most efficient in utilizing substrates, supporting our hypothesis that maturing ecosystems become more efficient. These changes in efficiency were linked to microbial community composition with fungi and Gram-negative bacteria being important biomarkers. Despite our initial hypothesis, complex substrate such as glycogen was utilized most efficiently. Our findings emphasize that differences in land use management systems as well as the composition of soil organic matter need to be considered when modelling C dynamics in soils. Further research is required to establish and evaluate appropriate proxies for substrate use efficiencies in various ecosystems

Structural and magnetic properties of isovalently substituted multiferroic BiFeO3: Insights from Raman spectroscopy

Raman spectra, supplemented by powder x-ray diffraction and magnetization data of isovalently A- and B-site substituted BiFeO3 in the Bi1−xLaxFeO3 (0≤x≤1), Bi1−xTbxFeO3 (0≤x≤0.2), and Bi0.9Sm0.1Fe1−xMnxO3 (0≤x≤0.3) series, are presented. A good agreement between the structural transitions observed by x-ray diffraction and the vibrational modes observed in the Raman spectra is found over the whole substitutional ranges, and in particular we find spectroscopic signatures of a PbZrO3-type structure for Bi0.8La0.2FeO3. Mode assignments in the substituted materials are made based on Raman spectra of the end-members BiFeO3 and LaFeO3. Moreover, by comparing spectra from all samples with R3c structure, the phonon assignment in BiFeO3 is revisited. A close connection between the degree of octahedral tilt and the Raman shift of the A1 oxygen a−a−a− tilt mode is established. An explanation for the strong second-order scattering observed in Bi1−xLaxFeO3 and Bi1−xTbxFeO3 is suggested, including the assignment of the previously mysterious BiFeO3 mode at 620 cm−1. Finally, the magnetization data indicates a transition from a cycloidal modulated state towards a canted antiferromagnet with increasing A-site substitution, while Bi0.9Sm0.1Fe1−xMnxO3 with x=0 and 0.15 exhibit an anomalous closing of the hysteresis loop at low temperatures. For low A-site substitution levels (x≤0.1) the decreasing Raman intensity of the Fe derived modes correlates with the partial destruction of the spin cycloid as the substitution level increases

Nodule detection in digital chest radiography: part of image background acting as pure noise

There are several factors that influence the radiologist's ability to detect a specific structure/lesion in a radiograph. Three factors that are commonly known to be of major importance are the signal itself, the system noise and the projected anatomy. The aim of this study was to determine to what extent the image background acts as pure noise for the detection of subtle lung nodules in five different regions of the chest. A receiver operating characteristic (ROC) study with five observers was conducted on two different sets of images, clinical chest X-ray images and images with a similar power spectrum as the clinical images but with a random phase spectrum, resulting in an image background containing pure noise. Simulated designer nodules with a full-width-at-fifth-maximum of 10 mm but with varying contrasts were added to the images. As a measure of the part of the image background that acts as pure noise, the ratio between the contrast needed to obtain an area under the ROC curve of 0.80 in the clinical images to that in the random-phase images was used. The ratio ranged from 0.40 (in the lateral pulmonary regions) to 0.83 (in the hilar regions) indicating that there was a large difference between different regions regarding to what extent the image background acted as pure noise; and that in the hilar regions the image background almost completely acted as pure noise for the detection of 10 mm nodule

Crystal structure and proton conductivity of BaZr0.9Sc0

Solid-state sintering has been used to prepare the perovskite BaZr0.9Sc0.1O3-delta. Analysis of X-ray powder diffraction data shows that an increase of the unit cell parameter, a, was observed after deuteration. Rietveld analysis of room-temperature neutron powder diffraction data confirmed cubic symmetry (space group Pm-3m). Dynamic thermogravimetric analysis indicates that the hydration process occurs below 335 degrees C and approximately 58% of the theoretical number of protonic defects can be filled. The presence of protons/deutrons is seen from the strong O-H/O-D stretch band in the infrared spectrum of the hydrated/deuterated samples. The proton conductivity of a prehydrated sample was investigated under dry and wet Ar atmosphere

Hållbara drivmedel - finns de?

Vårt syfte med denna rapport är att diskutera drivmedel från ett brett perspektiv ur hållbarhetssynpunkt. Biodrivmedel och el analyseras och jämförs med fossila drivmedel. Vår målsättning är att försöka peka ut under vilka förutsättningar som drivmedel kan anses försvarbara ur hållbarhetssynpunkt och vilka system som vi bör utveckla respektive vilka system som vi bör undvika. En övergripande slutsats i studien är att man inte kan fastställa hur hållbara biodrivmedel blir i framtiden utan att samtidigt beakta skala och tillväxttakt. Dagens biodrivmedel i Sverige är hållbara utifrån den aktuella produktionsvolymen och gynnar utvecklingen av nya drivmedelssystem, men man bör ställa hårda krav på energi- och klimateffektivitet i hela bränslekedjan (från odling till tank) vid ökade produktionsvolymer. Det är av hög prioritet att utveckla bränslesnåla bilar och här kommer elhybridteknologin och elbilar att bli allt viktigare. En långsiktig strategi för biodrivmedel bör innehålla satsningar på teknologi både för termisk förgasning och biologiska omvandlingsmetoder för lignocellulosa eftersom detta är kompletterande lika mycket som konkurrerande teknologier samt ger större flexibilitet och mindre risk för konflikter. Biogas från restprodukter har stora miljöfördelar och kan expandera med liten risk för konflikter. Certifiering (rätt utformat) är ett viktigt och nödvändigt verktyg på vägen mot mer hållbara drivmedel och vid ökade produktionsvolymer, men dessa system ska inte överskattas då de aldrig kan innefatta alla hållbarhetskriterier. Socio-ekonomiska aspekter som arbetsförhållanden, lokal landsbygdsutveckling osv samt effekter av ökad markkonkurrens måste i första hand lösas med generella åtgärder som nationell lagstiftning, fördelningspolitik, program och planer som i sin tur bör stödjas av internationella avtal och utvecklingssamarbete på olika nivåer. Oavsett utvecklingen i Sverige eller EU så kommer biodrivmedelsproduktionen globalt att öka, framför allt i utvecklingsländerna. Det är därför viktigt att ta vara på den möjlighet vi har idag att medverka i utvecklingen och införandet av hållbarhetskriterier. Förnybara drivmedel kan, med rätt utformning och styrmedel för lämplig tillväxttakt och produktionsvolym, leda till en positiv och hållbar utveckling i både industri- och utvecklingsländer