Boréa (Sweden)

Abstract Boreal forest landscapes are rapidly transformed through expanding clearcutting forestry, leading to a decline in forests with long tree continuity and an increase in even‐aged production stands. The role of remnant forests in supporting biodiversity within production forest landscapes remains poorly understood. Northern Europe provides an ideal setting for studying mosaics of clearcut and remnant continuity forests, given its long history of clearcutting and the prevalence of even‐aged forest stands. New remote‐sensing techniques have enabled the identification of forests in boreal Sweden that have maintained permanent tree cover at least since the 1950s (‘continuity forest’), meaning that they have likely never been clearcut, with removal of all trees. Using these data (including production forest as well as protected forest), we randomly selected 16 areas, each 225 km2 in size, with the proportion of continuity forest ranging from 2% to 25%. In each study area, we selected four even‐aged production forest stands aged 0–80 years and one selectively harvested (never‐clearcut) production stand aged 81–120 years. As model organisms for assessing biodiversity, we used epiphytic lichens on randomly selected Norway spruce Picea abies trees. We recorded 164 epiphytic lichen taxa on 926 trees. Species richness (including species of conservation concern) in the even‐aged forests <80 years old increased with the proportion continuity forest in the surrounding landscape. In contrast, there was no relationship between the richness of lichens and the proportion continuity forest for the older, selectively harvested production forests. Our results suggest that continuity forests are an important dispersal source for even‐aged production forests since almost all of the epiphytic lichen occurrences represent new colonization. Our results also show that continuity production forests >80 years old are important to epiphytic biodiversity since they host many species of conservation concern. Synthesis and applications. Our study has relevance for forestry and conservation across the boreal biome where a continued rapid expansion of clearcutting into primary forest landscapes is likely. Preserving continuity forests for the future would enrich the epiphytic biodiversity of younger, even‐aged production forests due to their function as dispersal nuclei. The remnant continuity forests are also conservation targets in their own right due to their rich lichen diversity.

Nanocomposite systems comprised of a poly(ethylene vinyl acetate) (EVA) matrix and carbon black (CB) or graphene nanoplatelets (GNPs) were used to investigate conductivity and crystallisation dynamics using a commercially relevant melt-state mixing process. Crystallisation kinetics and morphology, as investigated by DSC and SEM, turn out to depend on the interplay of (i) the interphase interactions between matrix and filler, and (ii) the degree of filler agglomeration. For the GNP-based systems, an almost constant conductivity value was observed for all compositions upon cooling, something not observed for the CB-based compositions. These conductivity changes reflect structural and morphological changes that can be associated with positive and negative thermal expansion coefficients. GNP-based systems were observed to exhibit a percolation threshold of approximately 2.2 vol%, lower than the 4.4 vol% observed for the CB-based systems.

Le nouveau livre de Dany Laferrière est un dialogue avec le poète japonais du XVIIe siècle, Basho. Ce dialogue avec le mort se tisse avec des phrases syncopées inspirées par des haïkus minimalistes sans vouloir en être. C’est une autre façon de respirer et d’écrire note Laferrière avec une rythmique singulière. Ainsi sur chaque page se précipite dessins au feutres et mots manuscrits qui ensemble déploient une réflexion. Chaque page est une fin en soi qui ouvre sur un infini. La phrase jette sa coupe d’autant plus rapidement qu’elle résonne avec le dessin qui chez Laferrière resserre l’esprit de la réflexion posée. On n’est pas dans un rapport traditionnel du dessin et de l’écrit, Laferrière reste avant tout haïtien dans l’abondance de l’expression graphique qui noie le mot ou le déchire. Chaque page dévoile ainsi un cœur secret de chair et de sang qui oscille entre le dessin et le mot. Il ne s’agit pas simplement d’illustration qui donne à voir ce qui bat entre les mots, mais le dessin rend le mot visible telle une larme ou un sanglot qui coule sur un visage et dans lesquels s’étranglent les mots. On ne se risque pas sur la route avec Bashô impunément, sans prendre avec soi ce peu de souffle auquel ce qui reste à vivre est suspendu.

Germany, France, Italy: the attribution of the first woodcut images has long been debated between several countries, to gain the technological primacy of the invention of reproductive printmaking, before Gutenberg’s movable type printing. Today we know how difficult it is, if not impossible, to establish a place and a date of origin of image printing in Europe. Impossible and probably unimportant. Printing was a European phenomenon in the 15th century, and we may ask ourselves whether a northern woodcut beyond the Italian borders was intended as something different than an Italian one. The contrast between northern and southern prints, which has been claimed by art historians from Vasari until the half of the 20th century, seems to be denied by early modern Italian sources. For example, a German woodcut from the first decades of the 15th century and a Florentine painting from the end of the 14th century can coexist as models for the illumination of the same manuscript. This unpublished case study of two Florentine 15th-century illuminations shows how a European cultural horizon was more common than we think today, and how much woodcut has been a fundamental tool for this broadening of horizons, since its very beginning.

Among the various requirements that high voltage direct current (HVDC) insulation materials need to satisfy, sufficiently low electrical conductivity is one of the most important. The leading commercial HVDC insulation material is currently an exceptionally clean cross-linked low-density polyethylene (XLPE). Previous studies have reported that the DC-conductivity of low-density polyethylene (LDPE) can be markedly reduced either by including a fraction of high-density polyethylene (HDPE) or by adding a small amount of a well dispersed, semiconducting nanofiller such as Al2O3 coated with a silane. This study demonstrates that by combining these two strategies a synergistic effect can be achieved, resulting in an insulation material with an ultra-low electrical conductivity. The addition of both HDPE and C8–Al2O3 nanoparticles to LDPE resulted in ultra-insulating nanocomposites with a conductivity around 500 times lower than of the neat LDPE at an electric field of 32 kV/mm and 60–90 °C. The new nanocomposite is thus a promising material regarding the electrical conductivity and it can be further optimized since the polyethylene blend and the nanoparticles can be improved independently.

The ability of electrical insulating materials within a module to act as insulators is a key safety requirement for PV technology. Direct current breakdown voltage is therefore now specified for relied-upon insulator materials in the IEC 61730–1 safety standard. To fulfill that requirement, a new test method has been developed within the IEC TS 62788–2 backsheet standard for the measurement of breakdown voltage. The development of the test will be described, including the verification of the most critical parameters relative to factors such as defect population(s), dielectric medium, electrode size, electrode surface roughness, maximum current limit, moisture conditioning, number of replicate specimens, rate of voltage rise, specimen thickness, test polarity, and test temperature. Many of these parameters were specifically explored in discovery experiments as the test method was developed. An interlaboratory round-robin (R-R) experiment was conducted to further validate the test method by quantifying its repeatability and reproducibility. The materials examined in the R-R include the backsheet materials: polyethylene terephthalate (PET, two thicknesses), polyvinyl fluoride (PVF), and laminated PVF/PET/PVF (“TPT”) as well as the encapsulants poly(ethylene-co-vinyl acetate) (EVA), and polyvinyl butyral (PVB). The precision of the test method as well as key factors contributing to the measurement will be described.

ABSTRACTLow‐density polyethylene (LDPE) is the preferred type of polyolefin for many medical and electrical applications because of its superior purity and cleanliness. However, the inferior thermo‐mechanical properties as compared to, for example, high‐density polyethylene (HDPE), which arise because of the lower melting temperature of LDPE, constitute a significant drawback. Here, we demonstrate that the addition of minute amounts of HDPE to a LDPE resin considerably improves the mechanical integrity above the melting temperature of LDPE. A combination of dynamic mechanical analysis and creep experiments reveals that the addition of as little as 1 to 2 wt% HDPE leads to complete form stability above the melting temperature of LDPE. The investigated LDPE/HDPE blend is found to be miscible in the melt, which facilitates the formation of a solid‐state microstructure that features a fine distribution of HDPE‐rich lamellae. The absence of creep above the melting temperature of LDPE is rationalized with the presence of tie chains and trapped entanglements that connect the few remaining crystallites. © 2016 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2017, 55, 146–156

© BME-PT. The effect of adding carbon black on the electrical and rheological properties of graphite nanoplatelets/poly(ethylene- butyl acrylate) copolymer composites produced via melt or solution mixing was studied. By adding a small amount of low- or high-structured carbon black to the nanocomposite, the electrical percolation threshold decreased and the final conductivity (at higher filler contents) increased. The effect on the percolation threshold was significantly stronger in case of the high-structured carbon black where replacing 10 wt% of the total filler content with carbon black instead of graphite nanoplatelets reduced the electrical percolation threshold from 6.9 to 4.6 vol%. Finally, the solution mixing process was found to be more efficient leading to a lower percolation threshold. For the composites containing high-structured carbon black, graphite nanoplatelets and their hybrids there was a quite reasonable correlation between the electrical and rheological percolation thresholds.