Seismic strengthening of existing RC buildings with external cross-laminated timber (CLT) walls hosting an integrated energetic and architectural renovation

Bulletin of Earthquake Engineering - In this study a timber-based integrated solution is presented to solve at once common issues affecting typical reinforced concrete (RC) existing buildings, such...     

Groundwater flow modeling of periods with periglacial and glacial climate conditions for the safety assessment of the proposed high-level nuclear waste repository site at Forsmark,Sweden

The impact of periglacial and glacial climate conditions on groundwater flow in fractured crystalline rock is studied by means of groundwater flow modeling of the Forsmark site, which was recently proposed as a repository site for the disposal of spent high-level nuclear fuel in Sweden. The employed model uses a thermal-hydraulically coupled approach for permafrost modeling and discusses changes in groundwater flow implied by the climate conditions found over northern Europe at different times during the last glacial cycle (Weichselian glaciation). It is concluded that discharge of particles released at repository depth occurs very close to the ice-sheet margin in the absence of permafrost. If permafrost is included, the greater part discharges into taliks in the periglacial area. During a glacial cycle, hydraulic gradients at repository depth reach their maximum values when the ice-sheet margin passes over the site; at this time, also, the interface between fresh and saline waters is distorted the most. The combined effect of advances and retreats during several glaciations has not been studied in the present work; however, the results indicate that hydrochemical conditions at depth in the groundwater flow model are almost restored after a single event of ice-sheet advance and retreat.     

Ordovician and Cretaceous tectonothermal history of the Southern Gemericum Unit from microprobe monazite geochronology (Western Carpathians,Slovakia)

The Southern Gemericum basement in the Inner Western Carpathians experienced a polyphase regional deformation. Differences in the pre-Alpine and Alpine events have been constantly discussed. To address this, monazites from metapelites and acid metavolcanic rocks were dated using the Th–U–Pb electron microprobe method. Three monazite generations, such as Precambrian, Early Paleozoic, and Alpine, have been recognized in the greenschist facies pelites and acid metavolcanic rocks of the Southern Gemericum basement. Both inherited magmatic monazite grains in metavolcanites and rare relics of detrital monazites within the polyphase monazite grains in metapelites yielded the Precambrian age in the time span of 550–660 Ma. They prove the provenance and derivation from deeper crustal Cadomian fragments. High-Y magmatic monazites of Early Paleozoic age (444 ± 13 and 477 ± 7 Ma) have been recorded in the acid metavolcanites and their metavolcaniclastics. These ages roughly fit within the previously published magmatic zircon age determinations (at 494 ± 1.7 and 464 ± 1.7 Ma) that clearly indicate two-phase volcanic activity in the Early Paleozoic Southern Gemericum basin. The Early Paleozoic magmatic monazites were partly overprinted by the low-Y Alpine monazites (133 ± 5 and 184 ± 16 Ma) at their rims. In Al-rich metapelites, the newly formed low-Y monazites of Alpine age commonly occur, reflecting the polystage compression geodynamic evolution with three distinct peaks at 100 ± 8, 133 ± 5, and 190 ± 16 Ma, respectively. No data as the evidence of the pre-Alpine metamorphic events were observed in metapelites. Only some monazites yield the age indications for the Permian extensional thermal re-heating (260–290 Ma). The monazite age data from the Southern Gemericum basement indicate the strong overprinting due to the polyphase Alpine deformation at least in the greenschist facies conditions.     

Geochemistry,mineralogy, and zircon U–Pb–Hf isotopes in peraluminous A-type granite xenoliths in Pliocene–Pleistocene basalts of northern Pannonian Basin (Slovakia)

Anorogenic granite xenoliths occur in alkali basalts coeval with the Pliocene–Pleistocene continental rifting of the Pannonian Basin. Observed granite varieties include peraluminous, calcic to peralkalic, magnesian to ferroan types. Quartz and feldspars are dominant rock-forming minerals, accompanied by minor early ilmenite and late magnetite–ulvöspinel. Zircon and Nb–U–REE minerals (oxycalciopyrochlore, fergusonite, columbite) are locally abundant accessory phases in calc-alkalic types. Absence of OH-bearing Fe, Mg-silicates and presence of single homogeneous feldspars (plagioclase in calcic types, anorthoclase in calc-alkalic types, ferrian Na-sanidine to anorthoclase in alkalic types) indicate water-deficient, hypersolvus crystallization conditions. Variable volumes of interstitial glass, absence of exsolutions, and lacking deuteric hydrothermal alteration and/or metamorphic/metasomatic overprint are diagnostic of rapid quenching from hypersolidus temperatures. U–Pb zircon ages determined in calcic and calc-alkalic granite xenoliths correspond to a time interval between 5.7 and 5.2 Ma. Positive εHf values (14.2 ± 3.9) in zircons from a 5.2-Ma-old calc-alkalic granite xenolith indicate mantle-derived magmas largely unaffected by the assimilation of crustal material. This is in accordance with abundances of diagnostic trace elements (Rb, Y, Nb, Ta), indicating A₁-type, OIB-like source magmas. Increased accumulations of Nb–U–REE minerals in these granites indicate higher degree of the magmatic differentiation reflected in Rb-enrichment, contrasting with Ba-enrichment in barren xenoliths. Incipient charnockitization, i.e. orthopyroxene and ilmenite crystallization from interstitial silicate melt, was observed in many granite xenoliths. Thermodynamic modeling using pseudosections showed that the orthopyroxene growth may have been triggered by water exsolution from the melt during ascent of xenoliths in basaltic magma. Euhedral-to-skeletal orthopyroxene growth probably reflects contrasting ascent rates of basaltic magma with xenoliths, intermitted by the stagnation in various crustal levels at a <3 kbar pressure. The Tertiary suite of intra-plate, mantle-derived A₁-type granites and syenites is geochemically distinct from pre-Tertiary, post-orogenic A₂-type granites of the Carpatho–Pannonian region, which exhibit geochemical features diagnostic of crustal melting along continental margins.     

The use of natural analogues to assess radionuclide transport

Predicting the long-term safety and performance of a repository for intermediate- to high-level radioactive wastes requires the evaluation of various scenarios which may influence the integrity of the repository system. One such scenario, radionuclide transport, is described, and some of the geochemical processes which serve to enhance or retard transport are illustrated with examples selected from natural analogue or natural system studies. These studies, as distinct from laboratory simulations, help considerably in understanding how near- and far-field radionuclide transport mechanisms work over geological timescales (thousands to hundreds of thousands of years), more in line with the anticipated lifespan of a repository.

Processes addressed include: stability of the spent fuel UO₂ matrix; bentonite backfill as a barrier to radionuclide diffusion; retention of radionuclides by absorption on fracture minerals; transport and diffusion of radionuclides controlled by interconnected bedrock porosity; geochemical influence and behaviour of repository construction materials on radionuclide transport.     

Arctic climate change in 21st century CMIP5 simulations with EC-Earth

The Arctic climate change is analyzed in an ensemble of future projection simulations performed with the global coupled climate model EC-Earth2.3. EC-Earth simulates the twentieth century Arctic climate relatively well but the Arctic is about 2 K too cold and the sea ice thickness and extent are overestimated. In the twenty-first century, the results show a continuation and strengthening of the Arctic trends observed over the recent decades, which leads to a dramatically changed Arctic climate, especially in the high emission scenario RCP8.5. The annually averaged Arctic mean near-surface temperature increases by 12 K in RCP8.5, with largest warming in the Barents Sea region. The warming is most pronounced in winter and autumn and in the lower atmosphere. The Arctic winter temperature inversion is reduced in all scenarios and disappears in RCP8.5. The Arctic becomes ice free in September in all RCP8.5 simulations after a rapid reduction event without recovery around year 2060. Taking into account the overestimation of ice in the twentieth century, our model results indicate a likely ice-free Arctic in September around 2040. Sea ice reductions are most pronounced in the Barents Sea in all RCPs, which lead to the most dramatic changes in this region. Here, surface heat fluxes are strongly enhanced and the cloudiness is substantially decreased. The meridional heat flux into the Arctic is reduced in the atmosphere but increases in the ocean. This oceanic increase is dominated by an enhanced heat flux into the Barents Sea, which strongly contributes to the large sea ice reduction and surface-air warming in this region. Increased precipitation and river runoff lead to more freshwater input into the Arctic Ocean. However, most of the additional freshwater is stored in the Arctic Ocean while the total Arctic freshwater export only slightly increases.     

Surface associations of enzymes and of organic matter: Consequences for hydrolytic activity and organic matter remineralization in marine systems

The extent to which marine organic matter is associated with surfaces and the consequences of such associations for organic matter remineralization are the focus of considerable attention. Since extracellular enzymes operating outside microbial cells are required to hydrolyze organic macromolecules to sizes sufficiently small for substrate uptake, the effects of surface interactions–on enzymes as well as on substrates–for hydrolytic activity also require investigation. We used a simplified laboratory system consisting of a free (dissolved) polysaccharide (pullulan) and the same polysaccharide tethered to agarose beads to restrict mobility, plus the corresponding free enzyme (pullulanase) and the same enzyme sorbed to montmorillonite (Mte), to investigate systematically the consequences of surface associations of enzymes and of substrates on hydrolytic activity. Changes in substrate molecular weight were monitored with time to measure the course of enzymatic hydrolysis. Although hydrolysis of free substrate was nearly complete after 2 min incubation with the free enzymes, the sorbed enzymes also effectively hydrolyzed free substrate, and the data suggest that they retained activity longer in solution compared to the free enzymes. Sorbed enzymes progressively hydrolyzed the free substrate from > 50 kD to lower molecular weights during a 24 h incubation, with a final product distribution on average showing only 1.4% and 10.3% of substrate still in the > 50 kD and 10 kD size classes, while 46.6%, 29.3%, and 12.5% of substrate was in the 4 kD, monomer, and free tag size classes, respectively. This product distribution was very similar to that of the free substrate/free enzyme experiment. Tethering the substrate to agarose beads led to lower substrate release (2–3% of total substrate after 98 h incubation) into solution compared to the free substrate case. For tethered substrates, the state of the enzyme (free or sorbed) measurably affected the molecular weight distribution of the hydrolysis products, with free enzymes producing a higher fraction of high molecular weight hydrolysis products (28.7 ± 5.4% of substrate > 50 kD at the end of the incubation) compared to sorbed enzymes (11.6 ± 2.8% of substrate > 50 kD at the end of the incubation.) Tethered substrates were also hydrolyzed in a sediment slurry from surface sediments from Cape Lookout Bight, North Carolina; 0.1% of total substrate was released by enzymes naturally present in 1 cm³ of sediment after 144 h incubation, demonstrating that the enzymes naturally present in marine sediments are also capable of accessing tethered substrates. These investigations suggest that surface associations of enzymes in marine systems may extend the active lifetime of such enzymes, providing an opportunity for hydrolysis over longer periods of time and producing a different size spectrum of hydrolysis products relative to free enzymes. Furthermore, in well-mixed systems, surface-associated enzymes can hydrolyze substrates whose mobility is restricted, highlighting the importance of processes such as resuspension and bioturbation on organic matter remineralization.     

Winter colonisation and succession of filamentous macroalgae on artificial substrates and possible relationships to Fucus vesiculosus settlement in early summer

During the reproduction period of Fucus vesiculosus, which occurs only once a year (in May–June) along the Finnish coast of the northern Baltic Sea, a thick carpet of filamentous algae often covers hard substrates suitable for zygote settlement. By placing out artificial substrates into the field, monthly over a period of eight months prior to F. vesiculosus settlement (October 2001–June 2002), we investigated the autumn/winter/spring colonisation and succession of filamentous algae and their possible relationships with the settlement success of F. vesiculosus under naturally variable field conditions. The substrates exposed in October 2001 became covered by filamentous brown algal Pilayella littoralis mats, which persisted over the settlement period of F. vesiculosus, but now also were accompanied by large amounts of the filamentous green alga Cladophora glomerata. The substrates exposed from November 2001 onwards hosted smaller amounts of P. littoralis during the winter and different filamentous algal communities at the time of F. vesiculosus settlement, i.e. less P. littoralis and C. glomerata, but Dictyosiphon foeniculaceus, Ceramium tenuicorne and Ulva intestinalis instead. We observed recruits of F. vesiculosus on all substrates, except on the ones placed out in October 2001. Significantly more P. littoralis and C. glomerata on the October substrates may explain the failed F. vesiculosus recruitment, although we could not establish direct causal or correlational relationships between filamentous algae and F. vesiculosus settlement. We compared the results with a previous un-replicated pilot study in the same area demonstrating similar response patterns.