Double-Averaging Concept for Rough-Bed Open-Channel and Overland Flows: Applications

The paper briefly outlines the double-averaging methodology for studying environmental rough-bed flows. It focuses on the applications of this methodology in environmental hydraulics by providing several examples illustrating advantages of this methodology over conventional approaches. Examples include: (1) identification of specific flow layers and flow types; (2) vertical distribution of the double-averaged velocity between the roughness tops and troughs; (3) vertical distribution of momentum fluxes and sinks for typical roughness types due to turbulence, mean flow heterogeneity, secondary currents, form drag, and viscous drag; (4) estimates of form-induced (dispersive) stresses and evaluation of their structure using quadrant analysis; and (5) closure development for mass-transfer-uptake processes for stream periphyton. These examples illustrate the advantages of the double-averaging methodology over conventional approaches as well as highlight its potential for studying flows over very rough beds, highly mobile beds, permeable beds, and surface–subsurface exchanges of mass, heat, and momentum. This methodology may also significantly improve research tools for studying a wide range of flow–biota interaction phenomena such as those related to aquatic plants, mussel communities, biofilms, and many others.     

Selenium content in the pilchard of the Adriatic Sea

The selenium content was determined in the muscle tissue (M. longissimus dorsi) of the pilchard (Clupea pilchardus). The fishes originated from catches at two localities, the mid-and northern Adriatic Sea, during two seasons—spring and autumn. The selenium content was determined by the hydride procedure of atomic absorption spectrophotometry, with the results being expressed as wet weight (ww). Four groups of the analysed samples indicated differences in the selenium content, depending on the location and time (season) of the catch. The highest selenium content was found in the pilchard of the mid-Adriatic Sea in spring (712.7 ±23.7 ng/g wet weight) and the lowest in the pilchard of the northern Adriatic Sea caught in autumn (472.7± 34.7 ng/g ww.). Regardless of seasonal differences and/or geographical aspects, the pilchard of the Adriatic Sea contains on average 580 ng Se/g ww and may be considered a significant source of this essential micronutrient.     

Aqua regia extracted metals in sediments from the industrial area and surroundings of Pančevo, Serbia

Surface and buried sediments were analyzed for Ba, Ca, Cd, Co, Cr, Cu, Mn, Ni, Pb, Zn and V, as well as for total carbon and hydrogen to assess the distribution of sediment pollution due to the vicinity of the petrochemical complex. The samples, collected from 20 locations within the petrochemical complex and from 16 locations outside the complex, were aqua regia extracted and analyzed by ICP/OES. Metals were determined with an acceptable accuracy for certified metals of 82-113%. The precision for the aqua regia extraction was satisfactory, less than 20%, except for Cd where it was 28%. Comparison of the data from the petrochemical with those from the non-petrochemical areas showed different distributions of the metals. Metals that exceeded the baseline range; Ba, Cd, Cu, Zn and Pb, were detected in higher concentrations in sediments that were under the influence of the chlor-alkali plant within the petrochemical complex. Comparison with data from the petrochemical complex and its surroundings and their distribution demonstrated that the metal compositions of the sediments were modified by anthropogenic activities.     

Optimization of roasting conditions as an useful approach for increasing antioxidant activity of carob powder

Antioxidant activity, gastrointestinal solubility of polyphenols and formation of different classes of Maillard reaction products (MRPs) that occurs during thermal processing of carob powder was investigated in relation to different roasting time-roasting temperature combinations applied. Principal component analysis (PCA) was used to group carob powders with the aim of proposing optimal roasting conditions for obtaining the one with the highest biological activity that can be expected after undergoing the simulation of gastrointestinal digestion. Results showed that antioxidant activity of carob powder can be significantly increased by roasting due to improved polyphenol solubility and formation of the early-stage MRPs. Fluorescent MRPs, HMF and furfural, known for their toxic properties, were the most abundant in samples roasted under more severe time/temperature conditions. Carob powder roasted at 130 °C for 30 min yielded the highest antioxidant activity and the lowest toxic MRP formation.     

Combined effects of inulin,pectin and guar gum on the quality and stability of partially baked frozen bread

Many attempts have been made to increase the nutritional value of bread by adding dietary fibre. However, fibre enrichment is usually associated with various technological problems. The aim of this study was to optimise the composition of a blend of inulin, pectin and guar gum to enrich the fibre content of partially baked frozen bread without impairing its technological quality. We prepared 20 formulations following a central composite design, together with 4 control breads. Bread enriched with inulin had higher crumb hardness, lower specific volume, shape, moisture content, and crumb cohesiveness than control bread, but improved flavour. Pectin and guar improved moisture content and crumb cohesiveness. There was no interaction between inulin and pectin for any of the bread attributes investigated, while interactions between inulin and guar were small. In contrast, guar and pectin significantly interacted to decrease volume and increase crumb hardness and chewiness. A desirability function method identified the optimised blend as containing 3% inulin, 0.9–1% pectin and 0.3–0.4% guar. Bread enriched with such blend had the following characteristics: specific volume, 4.06 cm³/g; shape, 0.63; crumb hardness, 189 g; resilience, 0.36; cohesiveness, 0.84; chewiness, 169 g; and flavour score, 4.6. Experimental values were close to the predicted ones, with prediction errors below 10% for all attributes tested. The specific volume, crumb hardness and chewiness of the enriched bread were superior to those of unenriched bread. However, undesirable textural changes occurred in the enriched bread during 12 weeks of frozen storage, and these changes strongly depended on the fibre blend composition.     

Effect of thermal oxidative ageing on the morphology of natural rubber networks as viewed by ESR

The change of network morphology of unfilled sulfur crosslinked natural rubber exposed to thermal oxidative ageing has been studied. Three model networks with different sulfur contents (efficient network, semi‐efficient and conventional vulcanizate) have been analysed by applying spin probe ESR, equilibrium swelling measurements and mechanical measurements. By combining the density distribution deduced from the complex ESR spectra and the equilibrium swelling density, it is shown that the major network changes occur in the networks with predominantly polysulfidic bonds (conventional network) after 96 h of ageing at 373 K. The effect of ageing on the network with predominantly monosulfidic bonds is much less pronounced. Both effects (main chain scission and additional local crosslinking) have been analysed in the course of prolonged ageing up to 240 h. A correlation between network structure and its mechanical performance is established. © 2000 Society of Chemical Industry     

Influence of free fatty acids, sterols and phospholipids on volatile compounds in olive oil headspace determined by solid phase microextraction-gas chromatography

In order to study the influence of some polar compounds, naturally present in virgin olive oils (VOOs), on the volatiles release, the volatiles-free olive oil matrix was enriched with free fatty acids (FFA) (concentration range from 0.35 to 1.40 g/100 g), sterols (1.0–2.5 g/kg) and phospholipids (1.6–6.0 g/kg). Sixteen standards of VOO aroma compounds were dissolved in thus obtained olive oil matrices. Volatile compounds were analysed by headspace solid phase microextraction with DVB/CAR/PDMS fibre and gas chromatography with flame ionization detection. Evaluation of the data by statistical analysis revealed that FFA, sterols and phospholipids, in concentration ranges considered in this study, generally did not significantly influence the determination of VOO volatiles. The most important changes occurred in the release of the three alcohols (Z-2-penten-1-ol, 1-hexanol and E-3-hexen-1-ol) and 3-methylbutyl acetate which slightly decreased upon the increase of FFA concentration.     

Ethical norms and issues in crowdsourcing practices: A Habermasian analysis

Crowdsourcing practices have generated much discussion on their ethics and fairness, yet these topics have received little scholarly investigation. Some have criticized crowdsourcing for worker exploitation and for undermining workplace regulations. Others have lauded crowdsourcing for enabling workers' autonomy and allowing disadvantaged people to access previously unreachable job markets. In this paper, we examine the ethics in crowdsourcing practices by focusing on three questions: (a) What ethical issues exist in crowdsourcing practices? (b) are ethical norms emerging or are issues emerging that require ethical norms? and, more generally, (c) how can the ethics of crowdsourcing practices be established? We answer these questions by engaging with Jürgen Habermas' discourse ethics theory to interpret findings from a longitudinal field study (from 2013 to 2016) involving key crowdsourcing participants (workers, platform organizers, and requesters) of three crowdsourcing communities. Grounded in this empirical study, we identify ethical concerns and discuss the ones for which ethical norms have emerged as well as others which remain unresolved and problematic in crowdsourcing practices. Furthermore, we provide normative considerations of how ethical concerns can be identified, discussed, and resolved based on the principles of discourse ethics.     

Identity metamorphoses in digital disruption: a relational theory of identity

Digital technologies have disrupted a variety of organizations; however, Information Systems research has yet to explore in-depth why this may be occurring or the implications of this process for those involved. In this paper we present an exemplary case of digital technology disruption in a newspaper company – an organization in the midst of an identity crisis. On the basis of ethnographic data, we explore the changes that resulted from the introduction of the digital medium, and how this has led to the evolution of the newspaper, as well as the metamorphosis of identities of the company, the company’s practitioners, and the consumers of the company’s content. Our findings suggest that shifts in the evolutionary trajectory of an organization can be traced to the rate and nature of identity metamorphoses among its key actors. Hence, in order to navigate and adapt to digital disruptions, we argue that an ongoing strategic renegotiation of the identities of all the actors involved is not only possible, but is required for an organization’s survival. In doing so, we provide a relational theory of identity.     

The influence of variety and harvest time on the bitterness and phenolic compounds of olive oil

The influence of harvest time on the intensity of bitterness and the level of phenol compounds in olive oil from the region of western Istria, obtained from 2 local (Bianchera and Busa) and one introduced, Italian variety (Leccino) was studied. Olive fruits were harvested at 3 different harvesting periods, during 4 successive crops seasons. Immediately after harvesting, the fruits were processed under the same conditions in a pilot plant. Basic quality parameters, the content of total polyphenols, o‐diphenols and the intensity of bitterness were determined in oil samples. Samples of oil obtained from the Bianchera and Busa varieties were additionally tested for stability at elevated temperature (98 °C) and under the influence of UV‐light. The results elaborated statistically showed the level of phenol compounds and the intensity of bitterness to be significantly influenced by both the harvest time and olive variety, with the influence of harvest time being more pronounced. The applied tests for accelerated deterioration of oil indicated a more rapid increase in the peroxide value in oil samples of both varieties exposed to UV‐light than in those exposed to elevated temperature. Both tests showed better stability of the oil obtained from the Bianchera variety.