Global changes in extreme events: regional and seasonal dimension

This study systematically analyzes the complete IPCC AR4 (CMIP3) ensemble of GCM simulations with respect to changes in extreme event characteristics at the end of the 21st century compared to present-day conditions. It complements previous studies by investigating a more comprehensive database and considering seasonal changes beside the annual time scale. Confirming previous studies, the agreement between the GCMs is generally high for temperature-related extremes, indicating increases of warm day occurrences and heatwave lengths, and decreases of cold extremes. However, we identify issues with the choice of indices used to quantify heatwave lengths, which do overall not affect the sign of the changes, but strongly impact the magnitude and patterns of projected changes in heatwave characteristics. Projected changes in precipitation and dryness extremes are more ambiguous than those in temperature extremes, despite some robust features, such as increasing dryness over the Mediterranean and increasing heavy precipitation over the Northern high latitudes. We also find that the assessment of projected changes in dryness depends on the index choice, and that models show less agreement regarding changes in soil moisture than in the commonly used ‘consecutive dry days' index, which is based on precipitation data only. Finally an analysis of the scaling of changes of extreme temperature quantiles with global, regional and seasonal warming shows that much of the extreme quantile changes are due to a seasonal scaling of the regional annual-mean warming. This emphasizes the importance of the seasonal time scale also for extremes. Changes in extreme quantiles of temperature on land scale with changes in global annual mean temperature by a factor of more than 2 in some regions and seasons, implying large changes in extremes in several countries, even for the commonly discussed global 2°C-warming targe

Quantification of the influence of concrete width per fiber strand on the splitting crack failure of textile reinforced concrete (TRC)

The composite material textile reinforced concrete (TRC) requires a high bond performance between the fiber strand and the concrete matrix. While the influence of the textile on bond behavior is well known, in this publication the influence of the concrete matrix is investigated by means of single-sided pull-out tests. The results of the presented study show dependence between the concrete strength and bond performance of the composite material. When a concrete of a higher-strength class is used, the bond-flow–pull-out distance curve shifts upward independent of the textile geometry and the yarn impregnation. A simplified model is presented to predict the occurrence of a crack along the fiber strand. This model serves as a basis to investigate the correlation between concrete width per fiber strand and resistance against a splitting crack. The effective concrete tensile strength decreases to about 35% when the concrete width is increased from 10 mm to 50 mm. To quantify the decrease, a mathematical relationship, which describes the test results independent of textile and concrete type, is proposed

About the effectiveness of a hydrophobic surface treatment of Baumberger Sandstones

The Baumberger Sandstone, a sandy limestone, is used since the Middle Ages as a building material not only in the surrounding Münster region of North Rhine-Westphalia (Germany), where it is quarried since to date. To prevent the ingress of water and reduce weathering processes conservation methods, mostly in form of organosilicon compounds, were used. This study deals with the performance of applied hydrophobing agents on Baumberger Sandstone samples and their influence on the weathering processes during long-term exposure. The samples were exposed at several locations in Germany to different climatic conditions for up to 24 years. Afterwards, investigations concerning the water absorption behaviour and the degree of superficial damages were carried out. With an evaluation method on basis of NMR measurements, a very low and uneven distributed effective hydrophobic zone could be detected. This caused an ingress of water in the uppermost part and a progressive weathering of investigated natural stones. Thus the hydrophobic surface treatment did not lead to a significant decrease of weathering or damaging processes. Based on these results a hydrophobic surface treatment of Baumberger Sandstone seems not to be suitable

The influence of 30 years outdoor weathering on the durability of hydrophobic agents applied on Obernkirchener Sandstones

The durability of eleven different water repellents applied on one sandstone type was studied after a long-term weathering at seven different locations in Germany. By measuring colour changes, it could be shown that the formation of black crusts, the deposition of particles and biogenic growth caused a gradual darkening as well as significant changes in total colour over time. Additionally, the water absorption behaviour was investigated with two different methods: applying a low pressure using the pipe method and capillary water absorption measurements from a wet underlay. Afterwards, the test results were analysed with four different evaluation methods: calculation of the protection degree from pipe method and capillary water absorption, determination of the velocity of water uptake during capillary water absorption and calculation of the damaged depth of the stone surface using single-sided NMR technique. The growing damaged depth leads to an increase of the water uptake velocity and to a decrease of the protection degree of the applied hydrophobing agents. Three protective agents based on isobutyltrimethoxysilane showed already after two years of outdoor weathering a clear loss of performance, which significantly increased after 30 years of exposure

Prestressing effect of shape memory alloy reinforcements under serviceability tensile loads

Repairing and strengthening of existing aged steel-reinforced concrete structures is a major challenge. Today, much of the repair work completed is insufficient and brittle. A promising new solution for repair and strengthening tasks is the use of iron-based shape memory alloy (Fe-SMA). The pre-strained Fe-SMA components enable the pre-stressing of existing building components due to the heat-triggered contraction of the steel. Thus, deflections can be reduced or even recovered. In addition, the cracking process can be adapted, and an improvement in the load, under which the first crack appears, is possible. In this paper, the effects of pre-stress generated by activated Fe-SMA rebars, which were centrally embedded inside of a concrete specimen, are shown. The objective of the study is to quantify the improvement in the loads of the first crack and show the influences of the pre-stressing on the load-bearing behavior and the cracking process. For this purpose, axial tensile tests were performed on concrete bars with height, width, and length of 50 mm, 70 mm, and 900 mm, respectively. These were compared to usual construction steel rebars, pre-strained but nonactivated Fe-SMA rebars, and activated Fe-SMA steel rebars. The evaluation of crack patterns and openings was done using digital image correlation (DIC). The pre-stressing of the concrete causes an increase in the first crack loads of more than 150%, which indicates a clear improvement in the state of serviceability limit

Analyzing surface near regions of hydrophobic and long-term weathered natural stones at microscopic scale

The visual appearance of building structures is an important attribute which reflects the character and identity of a region. Due to the influence of weathering, the surfaces of building stones alter, leading to aesthetic changes of the material surface such as discoloration or darkening. In this study, near-surface regions of weathered Baumberger (BST), Schleeriether (SST), and Obernkirchener Sandstones (OKS) have been analyzed at the microscopic scale in order to investigate the intensity and the extent of visual as well as structural changes and how both can be a ected due to the presence of surface treatments with hydrophobing agents. It could be detected that aesthetic changes appeared already after 2 years of outdoor exposure, with the slightest variations on BST surfaces, followed by SST and OKS. The use of hydrophobing agents leads to a reduction in surface darkening in the short term. After long-term weathering, no significant changes are visible, as similar values in total color di erence (DE*) were measured. Biogenic growth and the formation of black weathering crusts are the main reasons for color alterations in the case of the examined stones. The surface damages occur especially on calcareous (BST) followed by clayey (SST) and quartzitic (OKS) stone surfaces

Today's virtual water consumption and trade under future water scarcity

The populations of most nations consume products of both domestic and foreign origin, importing together with the products the water which is expended abroad for their production (termed 'virtual water'). Therefore, any investigation of the sustainability of present-day water consumption under future climate change needs to consider the effects of potentially reduced water availability both on domestic water resources and on the trades of virtual water. Here we use combinations of Global Climate and Global Impact Models from the ISI–MIP ensemble to derive patterns of future water availability under the RCP2.6 and RCP8.5 greenhouse gas (GHG) concentrations scenarios. We assess the effects of reduced water availability in these scenarios on national water consumptions and virtual water trades through a simple accounting scheme based on the water footprint concept. We thereby identify countries where the water footprint within the country area is reduced due to a reduced within-area water availability, most prominently in the Mediterranean and some African countries. National water consumption in countries such as Russia, which are non-water scarce by themselves, can be affected through reduced imports from water scarce countries. We find overall stronger effects of the higher GHG concentrations scenario, although the model range of climate projections for single GHG concentrations scenarios is in itself larger than the differences induced by the GHG concentrations scenarios. Our results highlight that, for both investigated GHG concentration scenarios, the current water consumption and virtual water trades cannot be sustained into the future due to the projected patterns of reduced water availability

Silvertone

These poems both celebrate and question the psychological existence we give to the objects that define our lives: the silver spoon from which the speaker sips, during each Epiphany, the sacred Borscht which she later catches her mother, after guests have left, pouring down the drain; the acoustic guitar on which the speaker’s father strums his minor-keyed songs from Ukraine; or the granite bust of a national poet that, in the hot sun, fails to inspire. With heart and humor the speaker examines what stays, goes, and how every object, once illuminated by the past, has the ability to take on new meaning. Or, as Miles Davis put it, “I’ll play it first then tell you what it is later.

Edge of House

Joseph Brodsky, in one of the essays in On Grief and Reason, writes that the twentieth century is the century of the displaced person. Writers in this century more than any other—from James Joyce and Ernest Hemingway to Paul Celan and Czeslaw Milosz to Seamus Heaney and Brodsky himself—have explored the ordeal of abandoning, voluntarily or involuntarily, a home that had become culturally or socially oppressive. Ukrainian-American poet Dzvinia Orlowsky, in Edge of House and Cuban-American poet Aleida Rodriguez, in Garden of Exile, while eschewing the political concerns of many of these writers, similarly draw on the impact of displacement and relocation in their lives to create an art deeply concerned with psychological and emotional boundaries and the sense of a divided self and world that they create. Though Orlowsky’s parents emigrated from Ukraine rather than herself, the legacy of displacement deeply informs Edge of House, her second collection. Orlowsky sees life as constituted by many kinds of boundaries and sees living as consisting in transgressing or respecting these boundaries. – Robert Levine, Poet Lor