Two complementary topics are discussed: (i) the continuous production of silver nanoparticles (AgNPs) and (ii) the measurement of reaction yield by X-ray absorption near-edge spectroscopy (XANES). ...The continuous polyol synthesis of AgNPs in grams amount and in the size range of 7–104 nm was carried out in the segmented flow tubular reactor (SFTR). Particle size was tailored by controlling the synthesis parameters such as temperature, reactant concentrations, and polyvinylpyrrolidone (PVP) molecular weight. The continuous production was tested for 4 h, and the product has shown constant particle size distribution over the whole production time. Reliable continuous production of 2.3 g h–1 of ∼100 nm AgNPs can be achieved with a lab-scale SFTR. The produced particles were fully characterized with respect to size, size distribution, and chemical purity. To better understand the growth mechanism, synchrotron-radiation high-resolution X-ray diffraction, and X-ray absorption spectroscopy data were collected directly on the AgNPs suspension. In particular, from XANES experiments, the conversion yield of Ag+ to Ag0 was measured. The results are consistent with a two-step process where PVP controls the particle nucleation while growth is ensured by thermally induced ethylene glycol oxidation.
Biological Soil Crusts (BSCs) are organosedimentary assemblages comprised of microbes and minerals in topsoil of terrestrial environments. BSCs strongly impact soil quality in dryland ecosystems ...(e.g., soil structure and nutrient yields) due to pioneer species such as Microcoleus vaginatus; phototrophs that produce filaments that bind the soil together, and support an array of heterotrophic microorganisms. These microorganisms in turn contribute to soil stability and biogeochemistry of BSCs. Non-cyanobacterial populations of BSCs are less well known than cyanobacterial populations. Therefore, we attempted to isolate a broad range of numerically significant and phylogenetically representative BSC aerobic heterotrophs. Combining simple pre-treatments (hydration of BSCs under dark and light) and isolation strategies (media with varying nutrient availability and protection from oxidative stress) we recovered 402 bacterial and one fungal isolate in axenic culture, which comprised 116 phylotypes (at 97% 16S rRNA gene sequence homology), 115 bacterial and one fungal. Each medium enriched a mostly distinct subset of phylotypes, and cultivated phylotypes varied due to the BSC pre-treatment. The fraction of the total phylotype diversity isolated, weighted by relative abundance in the community, was determined by the overlap between isolate sequences and OTUs reconstructed from metagenome or metatranscriptome reads. Together, more than 8% of relative abundance of OTUs in the metagenome was represented by our isolates, a cultivation efficiency much larger than typically expected from most soils. We conclude that simple cultivation procedures combined with specific pre-treatment of samples afford a significant reduction in the culturability gap, enabling physiological and metabolic assays that rely on ecologically relevant axenic cultures.
The dispersion of nanosized gamma aluminas with high specific surfaces areas (100 m
2/g) and primary particle sizes around 20 nm, using polyacrylic acid, has been investigated. The effect of pH and ...polymer concentration showed that the highest density green bodies were produced using high polymer concentrations (6 wt.%) and pH of 6. Interparticle potential calculations have been made and help explain the underlying dispersion mechanism at least on a qualitative level. The dispersions were then used to slip cast green bodies followed by drying and sintering. The types of gamma alumina powder have been investigated, the pure gamma alumina, doped with MgO and also with the addition of alpha alumina seeds. The high degree of agglomeration of the gamma alumina powders led to very low densities (60%) even the alpha seeded alumina reached only 85% theoretical density. Attrition milling with zirconia media improves both green density and sintered densities significantly with all powders showing sintered densities >
97%. Microstructural analysis on polished and etched surfaces show, however, that the grain sizes are well above 1 μm over 50 times greater than the initial gamma alumina primary particles. A two-step sintering cycle was investigated with the Mg doped powder and average grain sizes around 580 nm were achieved.
Advancing key outcomes of sustainability building assessment Kaatz, Ewelina; Root, David S.; Bowen, Paul A. ...
Building research and information : the international journal of research, development and demonstration,
20/7/1/, Letnik:
34, Številka:
4
Journal Article
Recenzirano
Sustainability assessment methods for building projects have a major role to play in introducing sustainability values and principles into mainstream construction practice. The paper reflects on ...potential measures that should advance building assessment practice in fostering sustainable construction and it advocates a redefinition of the objectives of building assessment methods. Arguably, the current emphasis in the building process and building assessment on a physical design and functional properties of buildings needs to be complemented with a concern for the quality of social and technical processes. To increase the effectiveness of any building assessment method, it is necessary to define clearly its desired outputs and outcomes. The paper suggests three significant outcomes of building sustainability assessment: integration; transparency and accessibility; and collaborative learning. These outcomes have emerged from a critical appraisal of the theory of Environmental Assessment and the Process Protocol. Environmental Assessment was examined as it provides valuable insights in terms of addressing sustainability at a project level. Lessons from the Process Protocol allow for the potential optimization of building projects using a building sustainability assessment method. Addressing these outcomes provides the means for proactive project enhancement, in terms of its sustainability and quality, by using a building sustainability assessment method.
Les méthodes d'évaluation de la durabilité appliquées aux projets de construction ont un rôle majeur à jouer en ce qui concerne l'introduction de valeurs et de principes de durabilité dans les principales pratiques de la construction. Cet article expose les mesures potentielles qui devraient faire progresser les pratiques d'évaluation des bâtiments en favorisant la construction durable. Il défend également une nouvelle définition des objectifs des méthodes d'évaluation des bâtiments. Il est permis de croire que l'accent mis actuellement, dans le cadre des procédés de construction et de l'évaluation des bâtiments, sur les propriétés théoriques physiques et fonctionnelles des bâtiments doit être complété en se préoccupant de la qualité des procédés sociaux et techniques. Pour améliore l'efficacité de toute méthode d'évaluation des bâtiments, il est impératif de définir clairement les résultats recherchés. Cet article suggère trois résultats significatifs de l'évaluation de la durabilité des bâtiments: l'intégration, la transparence et l'accès et, enfin, l'apprentissage en collaboration. Ces résultats ressortent d'une appréciation critique de la théorie de l'évaluation environnementale et des protocoles de procédés. L'évaluation environnementale a été examinée car elle fournit des informations précieuses en termes de durabilité concernant un niveau de projet. L'enseignement tiré des protocoles de procédés permet une optimisation potentielle de projets de construction en utilisant une méthode d'évaluation de la durabilité des bâtiments. L'étude de ces résultats débouche sur des moyens propres à améliorer des projets proactifs, en termes de leur durabilité et de leur qualité, en utilisant une méthode d'évaluation de la durabilité des bâtiments.
Mots-clés: évaluation de la durabilité des bâtiments, évaluation environnementale, intégration, protocoles de procédés, participation des intervenants, développement durable
The evolution of the concept of sustainable development is used as a basis for advancing understanding of sustainable construction. Principles of sustainable construction are developed and divided ...into four 'pillars' - social, economic, biophysical and technical - with a set of over-arching, process-oriented principles, to be used as a checklist in practice. A multi-stage framework is proposed which requires the application of Environmental Assessment and Environmental Management Systems for construction projects.
Recent research on unbalanced bidding models has identified both the benefits and the risks generated from different prices applied to the component items of a construction project. It has also been ...proposed that modern portfolio theory (MPT) be used as the technique by which to trade-off the conflicting objectives of maximizing the expected profit and, at the same time, minimizing the risk. The MPT methodology has previously been found to provide contractors with a technique by which they can identify and sift out all of the efficient item-price combinations, such that they need not suffer the consequences of deciding upon any substandard inefficient pricing combination. The use of MPT still leaves contractors with a wide range of choices. This paper introduces and applies microeconomic techniques namely cumulative prospect theory (CPT) to narrow these choices down to only one optimal choice. CPT serves to equate different return-risk alternatives to find the one set of item prices that will provide the optimal outcome in light of the contractor’s risk profile. The paper concludes by applying and evaluating this technique, on a small hypothetical project. Results show that a contractor with such a profile is able to identify prices that will generate an expected mean profit of 150%, more than they could accomplish by way of balanced pricing.
A research model was proposed investigating the relationships between work demand, role blurring, work-to-family conflict, and health and wellbeing consequences, and the model was tested on ...registered South African construction professionals. Structural equation modelling (SEM) was used to analyze the data collected from an online survey. The research results show that work pressure is a salient antecedent to all role blurring activities, i.e. after-hours work contact, pre-occupation with work, and multi-tasking between job tasks and family tasks whilst at home. Work hours directly predict work contact but indirectly affect pre-occupation and multi-tasking via the mediating role of work contact. All role blurring activities are positively associated with construction professionals' experience of work-to-family conflict, which subsequently leads to depression and sleep problems. The results also show that depression affects the quality of sleep and construction professionals are likely to use alcohol consumption to cope with sleep problems. However, depression was found to be negatively associated with alcohol consumption, which calls for a more fine-grained analysis of the relationship. The study highlights the importance of appropriate work design with manageable workloads and reasonable work hours, and the promotion of boundary tactics for reducing work-family role blurring and conflict experienced by construction professionals.
Atomistic representation of a system containing an inorganic surface (grey), an organic molecule (purple), ions (green) and water.
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•There is a vast number of computational work ...regarding titanium oxide surfaces.•Surface properties control its interactions with ions and organic molecules.•Water can delay or prevent adsorption of species on the surface.
The surface of a biomaterial can play a major role in its biological fate since the surface is the primary pathway for its interaction with the body. As the natural response of the body to a foreign material is to encapsulate it with a fibrous material, the interactions between the body and the biomaterial are mediated by this fibrous layer. Initial interactions occur between the biomaterial surface, water, ionic species and organic molecules, which then mediate further interactions with body tissues. Surface engineering can influence these interactions and hence, improve the biocompatibility of the biomaterial. Therefore, both experimental and computational studies have been interested in phenomena happening at the solid-solution interface as their mechanisms and driving forces can point to new directions for biomaterial design and evaluation. In this review, we summarize the computational work on the interaction of titanium oxide surfaces (mainly rutile) with solvated ions and organic molecules by means of molecular dynamics, with a certain relevance to bioactivity testing protocols. The primary goal of this review is to present the current state of the art and draw attention to points where further investigations are required.
The HIV/AIDS pandemic poses a substantial long-term threat to economic development in South Africa. A questionnaire survey explored the perceptions of a sample of construction firms in the Western ...Cape regarding HIV/AIDS policy and treatment programmes. The findings show that there is no universal view about the long-term threat of HIV/AIDS. Most organizations have awareness policies in place but prevention and treatment policies are less common. Treatment programmes are the least implemented of all intervention services due to insufficient resource capacity, the potential stigmatization of infected persons, and low take-up rates. Despite an acknowledgement of the benefits flowing from mounting treatment programmes, doubt exists as to their financial viability.
Deciphering the calcium silicate hydrate (C-S-H) surface is crucial for unraveling the mechanisms of cement hydration and property development. Experimental observations of C-S-H in cement systems ...suggest a surface termination which is fundamentally different from the silicate-terminated surface assumed in many atomistic level studies. Here, a new multiparameter approach to describing the (001) basal C-S-H surface is developed, which considers how the surface termination affects the overall properties (Ca/Si ratio, mean chain length, relative concentration of silanol and hydroxide groups). Contrary to current beliefs, it is concluded that the (001) C-S-H surface is dominantly calcium terminated. Finally, an adsorption mechanism for calcium and hydroxide ions is proposed, which is in agreement with the surface charge densities observed in previous studies.
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