Development of social sustainability assessment method and a comparative case study on assessing recycled construction materials

Purpose

Sustainability analysis should include the assessment of the environmental, social, and economic impacts throughout the life cycle of a product. However, the social sustainability performance assessment is seldom carried out during materials selection due to its complex nature and the lack of a social life cycle assessment tool. This study presents a single score-based social life cycle assessment methodology, namely social sustainability grading model, for assessing and comparing the social sustainability performance of construction materials using a case study on recycled and natural construction materials.

Methods

The proposed method is developed based on the methodological framework provided by the United Nations Environment Programme/Society of Environmental Toxicology and Chemistry guidelines published in 2009 and the methodological sheets published in 2013, the indicators and sustainability reporting guidelines provided by the Global Reporting Initiatives and ISO 26000 for social responsibility of products, and the indicators provided by the Hong Kong Business Environment Council Limited for construction sustainability. A twofold research approach is proposed in this model: the first one is the qualitative research based on expert interviews to identify, select, and prioritize the relevant subcategories and indicators, and the second one is the operational research based on the case-specific survey to collect the required data. A social sustainability index was proposed for the interpretation of the results effectively. A case study on construction materials was conducted to illustrate the implementation of the method using case-specific first-hand data.

Results and discussion

The major outcome of this study is the systematic development of a social sustainability assessment tool based on the established standards and guidelines. The case study showed that four subcategories are crucial social concerns for construction materials (i.e., health and safety issues of the materials, health and safety of workers, company’s commitment to sustainability, and company’s policies on energy and water consumption). Based on the sustainability index proposed, using recycled aggregates from locally generated waste materials scored higher (about 31–34%) social sustainability than using imported natural aggregates. In addition, recycled aggregates and natural aggregates achieved “sustainable” and “neutral” rating sustainability levels, respectively. However, several subcategories (e.g., health and safety, working hour, forced work, training and social benefits of workers, and quality of the materials and information disclosing to public) are still needed to improve the social sustainability performance of recycled aggregates.

Conclusions

An integrated social life cycle assessment method is presented in this study for assessing the social sustainability of construction materials. In addition, the reported case study in this paper is one of the first attempts for social sustainability assessment of recycled construction materials, and the method can be applied to other recycled materials/products for comparative analysis. However, several critical factors, such as integration in other life cycle methods and software, sensitivity analysis, and more case studies, are still needed for further improvement of the developed method.

     

Resting‐state functional connectivity measured by diffuse correlation spectroscopy

Near‐infrared diffuse correlation spectroscopy (DCS) is used to record spontaneous cerebral blood flow fluctuations in the frontal cortex. Nine adult subjects participated in the experiments, in which 8‐minute spontaneous fluctuations were simultaneously recorded from the left and right dorsolateral and inferior frontal regions. Resting‐state functional connectivity (RSFC) was measured by the temporal correlation of the low frequency fluctuations. Our data shows the RSFC within the dorsolateral region is significantly stronger than that between the inferior and dorsolateral regions, in line with previous observations with functional near‐infrared spectroscopy. This indicates that DCS is capable of investigating brain functional connectivity in terms of cerebral blood flow.      

Effects of molecular crowding on the interaction between DNA and the Escherichia coli regulatory protein TyrR

Fluorescence quenching has been used to measure quantitatively the effects of sucrose and triethylene glycol on the interaction between the Escherichia coli regulatory protein TyrR and a 30-basepair oligonucleotide containing the strong TyrR box of the TyrR operon. It was observed that the apparent binding constant increased in the presence of co-solutes, the dependence of the logarithm of the apparent binding constant on molar concentration being indistinguishable and essentially linear for both co-solutes. This activation of the TyrR-oligonucleotide interaction is attributed to thermodynamic nonideality arising from molecular crowding, an interpretation which is supported by the reasonable agreement observed between the experimental extent of reaction enhancement and that predicted on the statistical-mechanical basis of excluded volume.     

THE FORMATION OF CHOLINE AND OF ACETYLCHOLTNE BY BRAIN IN VITRO

Abstract— Free choline and acetylcholine (ACh) in mouse or rat brain were assayed biologically. The subcellular distribution of ACh in brain slices that had been incubated in the presence of eserine was compared to that in control brain; during incubation, the ACh outside nerve endings increased four-fold, the ACh released from synaptosomes by osmotic shock doubled but the ACh bound firmly within nerve endings did not increase. The two nerve ending stores of ACh were labelled to similar specific radioactivities when slices were incubated with [³H]choline, but the specific radioactivity of the ACh formed was much lower than that of the added choline. Tissue incubated in the presence of eserine released choline and ACh into the medium and the tissue levels of both substances increased. Brain tissue exposed to Na⁺-free medium lost 84 per cent of its ACh and 66 per cent of its free choline; the amounts of both substances returned towards control values during subsequent incubation in a normal-Na⁺ medium (choline-free). Both the ACh outside nerve endings and the ACh associated with synaptosomes were depleted when tissue was incubated in Na⁺-free medium.     

NMR spectroscopic characterization of a beta-(1,4)-glycosidase along its reaction pathway: stabilization upon formation of the glycosyl-enzyme intermediate

NMR spectroscopy was used to search for mechanistically significant differences between the thermodynamic and dynamic properties of the 34 kDa (alpha/beta)8-barrel catalytic domain of beta-(1,4)-glycosidase Cex (or CfXyn10A) in its free (apo-CexCD) and trapped glycosyl-enzyme intermediate (2FCb-CexCD) states. The main chain chemical shift perturbations due to the covalent modification of CexCD with the mechanism-based inhibitor 2,4-dinitrophenyl 2-deoxy-2-fluoro-beta-cellobioside are limited to residues within its active site. Thus, consistent with previous crystallographic studies, formation of the glycosyl-enzyme intermediate leads to only localized structural changes. Furthermore, 15N relaxation methods demonstrated that the backbone amide and tryptophan side chains of apo-CexCD are very well ordered on both the nanosecond to picosecond and millisecond to microsecond time scales and that these dynamic features also do not change significantly upon formation of the trapped intermediate. However, covalent modification of CexCD led to the increased protection of many amides and indoles, clustered around the active site of the enzyme, against fluctuations leading to hydrogen exchange. Similarly, thermal denaturation studies demonstrated that 2FCb-CexCD has a significantly higher midpoint unfolding temperature than apo-CexCD. The covalently modified protein also exhibited markedly increased resistance to proteolytic degradation by thermolysin relative to apo-CexCD. Thus, the local and global stability of CexCD increase along its reaction pathway upon formation of the glycosyl-enzyme intermediate, while its structure and fast time scale dynamics remain relatively unperturbed. This may reflect thermodynamically favorable interactions with the relatively rigid active site of Cex necessary to bind, distort, and subsequently hydrolyze glycoside substrates.