Alkali–silica reactions (ASR): Literature review on parameters influencing laboratory performance testing

Utilisation of potentially alkali–silica reactive aggregates requires reliable performance tests to evaluate the alkali–silica reactivity of various aggregate combinations, including their alkali threshold dependence on binder type. Several such performance tests have been used worldwide for more than 15 years, but none of the methods have proven to be reliable for use with all aggregate types and all binders. One of the objectives of RILEM TC 219-ACS (2007–2012) is to develop and validate one or more of such performance tests.Several parameters may influence the results obtained in an accelerated performance test compared to the field behaviour. Based on a state of the art literature review, this paper discusses which parameters must be considered to be able to develop reliable ASR performance testing methods and provides some tentative recommendations. The internal humidity in the test specimens, the extent of alkali leaching and the storage temperature are of particular importance.     

Selective critique of risk assessments with recommendations for improving methodology and practise

Risk assessments are often criticised for defending activities that could harm the environment and human health. The risk assessments produce numbers which are used to prove that the risk associated with the activity is acceptable. In this way, risk assessments seem to be a tool generally serving business. Government agencies have based their regulations on the use of risk assessment and the prevailing practise is supported by the regulations. In this paper, we look more closely into this critique. Are risk assessments being misused or are risk assessments simply not a suitable tool for guiding decision-making in the face of risks and uncertainties? Is the use of risk assessments not servicing public interests? We argue that risk assessments may provide useful decision support but the quality of the risk assessments and the associated risk assessment processes need to be improved. In this paper, three main improvement areas (success factors) are identified and discussed: (1) the scientific basis of the risk assessments needs to be strengthened, (2) the risk assessments need to provide a much broader risk picture than what is typically the case today. Separate uncertainty analyses should be carried out, extending the traditional probabilistic-based analyses and (3) the cautionary and precautionary principles need to be seen as rational risk management approaches, and their application would, to a large extent, be based on risk and uncertainty assessments.     

The use of a basic safety investment model in a practical risk management context

We consider a basic model in economic safety analysis: a firm is willing to invest an amount x in safety measures to avoid an accident A, which in the case of occurrence, leads to a loss of size L. The probability of an accident is a function of x. The optimal value of x is determined by minimizing the expected costs. In the paper, we re-examine this model by adopting a practical risk/safety management perspective. We question how this model can be used for guiding the firm and regulators in determining the proper level of investment in safety. Attention is given to issues like how to determine the probability of an accident and how to take into account uncertainties that extend beyond the expected value. It is concluded that the model, with suitable extensions and if properly implemented, provides a valuable decision support tool. By focusing on investment levels and stimulating thereby the generation of alternative risk-reducing measures, the model is considered particularly useful in risk reduction (ALARP) processes.     

Influence of Ball-Milling,Nanostructuring, and Ag Inclusions on Thermoelectric Properties of ZnSb

In the last few years much attention has been given to the promising thermoelectric material Zn₄Sb₃. The related ZnSb phase features a high Seebeck coefficient at room temperature. Its thermoelectric conversion efficiency, however, is low due to its relatively high thermal conductivity. ZnSb has potential as a thermoelectric material if this can be reduced. Nanostructuring of bulk materials and introducing extrinsic particles have been shown to lower lattice thermal conductivity. In this study we created the microstructure by ball-milling of bulk ZnSb and added Ag particles which attain sizes in the micrometer range in this milling process. Hot-pressing was used to obtain dense samples. Several techniques were used for structural characterization. Here we report on scanning electron microscopy, transmission electron microscopy, and x-ray diffraction analysis. Thermoelectrical measurements were conducted around room temperature. Thermal conductivity was reduced by up to 40% by the reported nanostructuring. However, the electrical conductivity and the Seebeck coefficient were adversely affected, leading to no overall improvement in performance.     

Product architecture design of multi-modal products

Incorporating multiple modes enables a product to change between different configurations, such as hybrid electric vehicles and washing machines. This paper investigates how multiple modes are constructed in modular product architecture—especially, how multi-modal modules are designed and used to construct overall product modality. The authors argue that product modality becomes viable by undertaking two strategies: temporal clustering, which activates and organizes different groups of modules in different modes, and modality propagation, which relies on modality of the product’s subordinate modules. A solution that successfully incorporates modality enables the system to achieve functions with minimal system resources; however, it also introduces extra complexity to the design process. In the final section, the authors propose two techniques that promote multi-modal modules in design processes. This research work provokes the considerations of modality in product architecture. It claims modality is an important factor that leads to innovative design solutions. To emphasize the importance of modality, the authors present a case study of two pasta machines and compare the radical differences in their modular design solutions.     

Immunomodulatory activity of dietary fiber: arabinoxylan and mixed-linked Beta-glucan isolated from barley show modest activities in vitro

High intake of dietary fiber is claimed to protect against development of colorectal cancer. Barley is a rich source of dietary fiber, and possible immunomodulatory effects of barley polysaccharides might explain a potential protective effect. Dietary fiber was isolated by extraction and enzyme treatment. A mixed-linked β-glucan (WSM-TPX, 96.5% β-glucan, Mw 886 kDa), an arabinoxylan (WUM-BS-LA, 96.4% arabinoxylan, Mw 156 kDa), a mixed-linked β-glucan rich fraction containing 10% arabinoxylan (WSM-TP) and an arabinoxylan rich fraction containing 30% mixed-linked β-glucan (WUM-BS) showed no significant effect on IL-8 secretion and proliferation of two intestinal epithelial cell lines, Caco-2 and HT-29, and had no significant effect on the NF-κB activity in the monocytic cell line U937-3κB-LUC. Further enriched arabinoxylan fractions (WUM-BS-LA) from different barley varieties (Tyra, NK96300, SB94897 and CDCGainer) were less active than the mixed-linked β-glucan rich fractions (WSM-TP and WSM-TPX) in the complement-fixing test. The mixed-linked β-glucan rich fraction from NK96300 and CDCGainer showed similar activities as the positive control while mixed-linked β-glucan rich fractions from Tyra and SB94897 were less active. From these results it is concluded that the isolated high molecular weight mixed-linked β-glucans and arabinoxylans from barley show low immunological responses in selected in vitro test systems and thus possible anti-colon cancer effects of barley dietary fiber cannot be explained by our observations.     

Peptides inhibitory to endopeptidase and aminopeptidase fromLactococcus lactis ssp.lactis MG1363, released from bovineβ-casein by chymosin,trypsin or chymotrypsin

Peptides inhibitory to the 70-kDa endopeptidase (PepO) from the cytoplasm ofLactococcus lactis ssp.lactis MG1363 were isolated from the supernatant (pH 4.6) of chymosin, tryptic and α-chymotryptic hydrolysates ofβ-casein (β-CN) by reversed-phase HPLC and identified by sequencing and mass spectrometry. Chymosin releasedβ-CN f193–209, kinetic constant (K _i) of which for inhibition of PepO was 60 μM. This peptide also inhibited (K _i=1700 μM) the 95-kDa aminopeptidase (PepN) fromL. lactis ssp.lactis MG 1363. Trypsin released two PepO-inhibitory peptides: one,β-CN f69–97, was not degradable by PepO (K _i=4.7 μM), while the other,β-CN f141–163, was degradable by PepO but competitively inhibited hydrolysis of methionine enkephalin by PepO. A peptide,β-CN f69–84, which inhibited PepO with aK _i of 8.1 μM, was isolated from the α-chymotryptic hydrolysate. Peptides released fromβ-CN by trypsin or chymotrypsin had very little inhibitory activity against PepN. PepO degradedβ-CN f193–209 very slowly compared with the hydrolysis of methionine enkephalin. All four inhibitory peptides (β-CN f193–209, f69–97, f69–84, f141–163) were readily degraded by thermolysin.     

A useful framework for optimal replacement models

In this note we present a general framework for optimization of replacement times. It covers a number of models, including various age and block replacement models, and allows a uniform analysis for all these models. A relation to the marginal cost concept is described.     

Linear and nonlinear rheological responses in aqueous systems of hydrophobically modified chitosan and its unmodified analogue

Oscillatory shear and viscosity measurements have been carried out on semidilute acid aqueous systems of unmodified chitosan (UM-chitosan) and of hydrophobically modified chitosan (HM-chitosan) with three different degrees of C12-aldehyde substitution. These systems form physical gels at higher concentrations. The gel point, determined by the observation of a frequency independent loss tangent, was found to be shifted toward lower concentrations with increasing hydrophobicity. At the gel point, a power law frequency dependence of the dynamic moduli (G′∼G″∼ω ⁿ) was observed, with n values of 0.36 and 0.46 for the UM-chitosan and the hydrophobically modified chitosans, respectively. These values are interpreted in the framework of a fractal model. The gel strength parameter S increased with decreasing hydrophobicity. The UM-chitosan and HM-chitosan systems exhibited a non-Newtonian shear thinning behavior. This effect is promoted by increasing polymer concentration and hydrophobicity. Both the linear and nonlinear rheological properties elucidate the intricate interplay between hydrophobic associations and entanglement effects. Received: 13 October 1997/Accepted: 24 October 1997