An Experimental study of the initial volumetric strain rate effect on the creep behaviour of reconstituted clays

Clayey soils tend to undergo continuous compression with time, even after excess pore pressures have substantially dissipated. The effect of time on deformation and mechanical response of these soft soils has been the subject of numerous studies. Based on these studies, the observed time-dependent behaviour of clays is mainly related to the evolution of soil volume and strength characteristics with time, which are classified as creep and/or relaxation properties of the soil. Apart from many empirical relationships that have been proposed in the literature to capture the rheological behaviour of clays, a number of viscid constitutive relationships have also been developed which have more attractive theoretical attributes. A particular feature of these viscid models is that their creep parameters often have clear physical meaning (e.g. coefficient of secondary compression, Cα). Sometimes with these models, a parameter referred to as initial/reference volumetric strain rate, has also been alluded as a model parameter. However, unlike Cα, the determination of and its variations with stress level is not properly documented in the literature. In an attempt to better understand , this paper presents an experimental investigation of the reference volumetric strain rate in reconstituted clay specimens. A long-term triaxial creep test, at different shear stress levels and different strain rates, was performed on clay specimen whereby the volumetric strain rate was measured. The obtained results indicated the stress-level dependency and non-linear variation of with time

Effective Stress Concept in Unsaturated Soils: Clarification and Validation of an Unified Framework

The effective stress principle, conventionally applied in saturated soils, is reviewed for constitutive modelling purposes. The assumptions for the applicability of Terzaghi’s single effective stress are recalled and its advantages are inventoried. The possible stress frameworks applicable to unsaturated soil modelling are reassessed in a comparative manner, specifically the Bishop’s single effective stress, the independent stress variables approach and the generalized stress framework. The latter considerations lead to the definition of a unified stress context, suitable for modelling soils under different saturation states. In order to qualify the implications brought by the proposed stress framework, several experimental data sets are re-examined in the light of the generalized effective stress. The critical state lines (CSLs) at different saturation states tend to converge remarkably towards a unique saturated line in the deviatoric stress versus mean effective stress plane. The effective stress interpretation is also applied to isotropic paths and compared with conventional net stress conception. The accent is finally laid on a second key feature for constitutive frameworks based on a unified stress, namely the sufficiency of a unique mechanical yield surface besides the unique CSL

Solar ultraviolet radiation and ozone depletion-driven climate change: Effects on terrestrial ecosystems

In this assessment we summarise advances in our knowledge of how UV-B radiation (280-315 nm), together with other climate change factors, influence terrestrial organisms and ecosystems. We identify key uncertainties and knowledge gaps that limit our ability to fully evaluate the interactive effects of ozone depletion and climate change on these systems. We also evaluate the biological consequences of the way in which stratospheric ozone depletion has contributed to climate change in the Southern Hemisphere. Since the last assessment, several new findings or insights have emerged or been strengthened. These include: (1) the increasing recognition that UV-B radiation has specific regulatory roles in plant growth and development that in turn can have beneficial consequences for plant productivity via effects on plant hardiness, enhanced plant resistance to herbivores and pathogens, and improved quality of agricultural products with subsequent implications for food security; (2) UV-B radiation together with UV-A (315-400 nm) and visible (400-700 nm) radiation are significant drivers of decomposition of plant litter in globally important arid and semi-arid ecosystems, such as grasslands and deserts. This occurs through the process of photodegradation, which has implications for nutrient cycling and carbon storage, although considerable uncertainty exists in quantifying its regional and global biogeochemical significance; (3) UV radiation can contribute to climate change via its stimulation of volatile organic compounds from plants, plant litter and soils, although the magnitude, rates and spatial patterns of these emissions remain highly uncertain at present. UV-induced release of carbon from plant litter and soils may also contribute to global warming; and (4) depletion of ozone in the Southern Hemisphere modifies climate directly via effects on seasonal weather patterns (precipitation and wind) and these in turn have been linked to changes in the growth of plants across the Southern Hemisphere. Such research has broadened our understanding of the linkages that exist between the effects of ozone depletion, UV-B radiation and climate change on terrestrial ecosystems

Comprehensive two-dimensional gas chromatography coupled with Tof-MS, a very useful tool for analysis of wines

Comprehensive two-dimensional gas chromatography (GCxGC) has emerged as a powerful analytical technique for unraveling the volatile composition of complex matrices. This work will present three applications of GCxGC Tof-MS to the oenological field, aimed to identify novel biomarkers to be used in the quality control process of the wine industry. Comprehensive mapping of volatile compounds was conducted in a large sample of 70 sparkling wines, produced by 48 different wineries across 6 vintages and representative of the two main production areas for premium Italian sparkling wines (Franciacorta (FC) and Trentodoc (TN)), using HS-SPME followed by GCxGC-Tof-MS and multivariate analysis. Selection and identification of 196 putative biomarkers allowed clear separation of sparkling wines from FC and TN. A spatial investigation of Shiraz wines fermented in triplicates from grapes collected from climatically diverse (warm/hot versus cold/temperate) regions of Australia (New South Wales) was made using HS-SPME followed by GCxGC-Tof-MS. Wine volatile profiles from warm/hot and cool/temperate climate could be distinguished according to the first two principal components. Wines from cool/temperate climate were characterised by higher levels of several terpenes such as alpha terpineol, linalool oxide, citronellol acetate, 1-p-menthen-9-al, cis-rose oxide, ho-trienol) and sesquiterpenes, whereas trend for norispoprenoids was less consistent. Higher TDN levels in wines from warm/hot climate were observed. Volatile composition of wines from four grape cultivars was investigated with GCxGC Tof-MS in association with multivariate analyses. Eighteen samples of Müller Thurgau, 48 samples of Pinot Gris, 36 samples of Chardonnay and 18 samples of Gewürztraminer were analyzed. A clear varietal differentiation according to the wine volatiles was affirmed by PCA and potential cultivar-specific biomarkers were identified

Programming and Activating Cyberparks: An Introduction and Overview

Programming and Activating Cyberparks deals with the variety of ways in which urban public spaces can be reinvigorated through the use of digital media technologies. As is outlined in the introduction to this volume, digital media technologies profoundly shape the use and perception of urban public spaces. Critical observers have noted that digital media may threaten the public nature of our cities and civic spaces. For instance, elsewhere we have described these threats in terms of three Cs: commercialisation, control, and capsularisation (de Lange and de Waal 2013). First, the combination of digital media technologies and consumer culture overlays everyday urban life with a market logic of pervasive customer tracing, quantification, and a vying for attention. Datafication and personalized recommendation services capitalise on our habitual everyday movements in the city, turning them into an ever-expanding string of (potential) customer ‘touchpoints’. This affects the spatial, social and cultural dimensions of almost every realm of urban life, from work to meeting to leisure to travel to home. Visible illustrations include the rapidly changing appearance of high streets in most cities, or the nature and quality of inner-city neighbourhoods coinciding with the popularity of platforms like Airbnb (for more on platforms, see van Dijck et al. 2018). As a result, our polyvocal and frictional public open spaces are being transformed into silent and seamless marketplaces, where public interactions are reduced to commercial transactions

Allotment gardens as a challenge for an urban designer

Irrespective of their specific form or of the way they are managed, urban allotment gardens and other urban gardens are important types of urban green spaces, able to influence, to contribute overall quality of cities. Particularly if part of broader green infrastructures, UAG may integrate positively within the complex inner metabolism of metropolitan areas. In particular the 10th chapter of the book, in which the author contributed actively, focus on the challenges and characteristics of urban agriculture practices in the city and the role of urban design and planning disciplines in order to ensure a better socio-spatial development

Two dimensional gas chromatography: a powerful tool to unravel wine volatiles

A temporal and spatial investigation of Shiraz wine volatile composition from four vineyards located in warm to hot climates in New South Wales Australia was conducted. Shiraz wines were made from grapes harvested at two different berry maturity levels based upon a sugar accumulation model. Grape harvests were conducted between 10 to 12 days apart (H1 and H2, respectively) and wines made in triplicate using controlled fermentations. Wine volatile compounds were analysed by head space-solid phase micro extraction coupled to comprehensive two dimensional gas chromatography quadrupole time of flight mass spectrometry (HS-SPME-GCxGC-TOFMS). Acquired data were deconvoluted and aligned with LECO ChromaTOF Version 4.22 software at a signal to noise ratio 100. A total of 1240 putative compounds were detected, of which 240 were significantly different in at least one of the harvest dates among four vineyards. Compound identity was confirmed by authentic standards, Kovats retention index and or by comparing spectra of compounds to the NIST 2.0, Wiley 8 and the FFNSC 2 (Chromaleont, Messina, Italy) mass spectral libraries. A clear separation of samples based on the harvest date is evident in Principal Component 1 which accounted for 40% of data variation. Derivates of lipoxygenase pathway, i.e. C5, C6 and C9 compounds were typically found in higher levels in wines from the first harvest (H1) compared to wines from the second harvest (H2), irrespective of vineyard site. However, this trend was less pronounced for C6 esters such as E-hexenyl acetate and Z-3-hexenyl acetate. Several monoterpenes, norisoprenoids and sesquiterpenes were also identified in wines, however no clear trend according to harvest date is evident for these compounds. Preliminary results indicate significant and coherent modulations of wine volatiles in relation to harvest date, irrespective of vineyard location with similar climatic parameters. HS-SPME GCxGC-TOFMS was proven to be fast, reliable and a powerful technique to unravel wine volatile composition