Identifying marginal suppliers of construction materials: consistent modeling and sensitivity analysis on a Belgian case

Purpose

The identification of marginal suppliers is a key element of consequential LCA. This study investigates how systematically the identification of marginal suppliers can be performed across different products, while maintaining consistent modeling choices. Some products relevant for the Belgian construction sector are taken as a case study.

Methods

To gain insight in the current practice of identifying marginal suppliers, 30 recent studies have been reviewed. Based on the findings of the review, a method was proposed to identify geographical market boundaries from trade data and sensitive suppliers from production data. Both retrospective and prospective approaches to anticipate the future effect of a change in demand were taken into account. The method was applied to compute both a retrospective and a prospective marginal supplier’s mix per product. Finally, the effect of the modeling choices on the size of geographical market boundaries and marginal mixes was estimated via regression analysis.

Results and discussion

The forecasts and marginal mixes obtained matched with those from the existing literature, although clear differences in results are observed between the retrospective and prospective approach. Deviations from default assumptions in LCA were observed as well, such as large regional geographical markets for cement and aggregates instead of local ones. The statistical sensitivity analysis showed that identifying geographical market boundaries has the largest effect on the final marginal mix and that these markets are relative stable over time.

Conclusions

The proposed method and corresponding sensitivity analysis is an attempt to gain insight into the effect of modeling choices in the context of the identification of marginal suppliers for consequential LCA. It can in principle be applied to any product for which trade and production data are available. The proposed method helps to identify marginal mixes on a consistent and transparent way, to improve the robustness of the results in future consequential LCAs.

     

Adenosine 5'-monophosphate challenge elicits a more peripheral airway response than methacholine challenge

Adenosine 5'-monophosphate (AMP) and methacholine are commonly used to assess airway hyperreactivity. However, it is not fully known whether the site of airway constriction primarily involved during challenges with either agent is similar. Using a ventilation distribution test, we investigated whether the constriction induced by each agent involves the lung periphery in a similar fashion. Ventilation distribution was evaluated by the phase III slope (S) of the single-breath washout, using gases with different diffusivities like helium (He) and hexafluorosulfur (SF(6)). A greater postchallenge increase in S(He) reflects alterations at the level of terminal and respiratory bronchioles, while a greater increase in S(SF6) reflects alterations in alveolar ducts, increases to an equal extent reflecting alterations in more proximal airways where gas transport is still convective for both gases. S(SF6) and S(He) were measured in 15 asthma patients before and after airway challenges (20% forced expired volume in 1-s fall) with AMP and methacholine. S(He) increased to a greater extent than S(SF6) after AMP challenge (5.7 vs. 3.7%/l; P = 0.002), with both slopes increasing to an equal extent after methacholine challenge (3.1%/l; P = 0.959). The larger increase in S(He) following AMP challenge suggests distal ventilation impairment up to the level of terminal and respiratory bronchioles. With methacholine, the similar increases in S(He) and S(SF6) suggest a less distal impairment. AMP, therefore, seems to affect more extensively the very peripheral airways, whereas methacholine seems to have an effect on less distal airways.     

Testing the relationship between intraspecific competition and individual specialization across both behavior and diet

Individual specialization within populations is increasingly recognized as important in both ecology and evolution, but researchers working on intraspecific variation in behavior and diet infrequently interact. This may be because individual specialization on diet and behavior was historically difficult to investigate simultaneously on the same individuals. However, approaches like stable isotope analysis that allow hindcasting past field diets for laboratory organisms may provide opportunities to unite these areas of inquiry. Here, we tested the role of intraspecific competition on individual specialization through analysis of both behavior and diet simultaneously. We focused on intraspecific competition as a mechanism that might drive individual specialization of both diet and behavior. We conducted this study in Vilas County, Wisconsin, United States (US), using rusty crayfish Faxonius rusticus from six lakes across a relative abundance gradient. We conducted six assays to measure individual specialization of behavior and used stable isotope analysis to measure individual specialization of diet. We then related both measures of individual specialization to relative abundance of F. rusticus using linear and quadratic models. We found a unimodal relationship between intraspecific competition and individual specialization of diet for F. rusticus, likely because some preferred resources are unavailable to specialize on at the highest densities of this well‐studied crayfish invader. Conversely, we found greater support for a linear relationship between individual specialization of behavior and intraspecific competition, perhaps because specialization by behavior is not inherently resource‐limited. Our results show that dietary and behavioral specialization may exhibit different responses to increased intraspecific competition, and demonstrate a potential technique that can be used to investigate individual specialization of diet and behavior simultaneously for the same individuals and populations.     

Complex fine‐scale phylogeographical patterns in a putative refugial region for Fagus sylvatica (Fagaceae)

Broad‐scale plastid (chloroplast) DNA studies of beech (Fagus sylvatica) populations suggest the existence of glacial refugia and introgression zones in south‐eastern Europe. We choose a possible refugium of beech in northern Greece, Mt. Paggeo, which hosts a private plastid haplotype for beech, to conduct a fine‐scale genetic study. We attempt to confirm or reject the hypothesis of the existence of a small‐scale refugium and to gain an understanding of the ecological and topographical factors affecting the spatial distribution of plastid haplotypes in the area. Our results reveal a high haplotype diversity on Mt. Paggeo, but the overall distribution of haplotypes shows no significant correlation with the ecological characteristics of the beech forests. However, the private haplotype is found at high frequencies in beech forests located in or near ravines, having a high spatial overlap with a relict vegetation type occurring in ecological conditions found mainly in ravines. This result emphasizes the importance of topography in the existence of glacial refugia in the wider area. Furthermore, haplotypes originating from two more widespread beech lineages in Greece are found on Mt. Paggeo, indicating a possible mixing of populations originating from a local refugium with populations from remote refugia that possibly migrated into the area after the last glaciation. © 2014 The Linnean Society of London, Botanical Journal of the Linnean Society, 2014, 174 , 516–528.     

Effects of caffeine,cyclic 3′, 5′ adenosine monophosphate and cyclic 3′, 5′ guanosine monophosphate in the development of the mycelial form of Sporothrix schenckii

The kinetics of the development of the mycelial form of Sporothrix schenckii from yeast cells and conidia in a minimal basal medium with glucose at pH 4.0 and 25 °C were established. Germ tube formation was used as the index of germination for both yeast cells and conidia. Yeast cells were first observed to develop germ tubes after 3 h of incubation, reaching 92±5%, after 12 h of incubation. Germ tubes were first detected in conidia after 9 h of incubation, and 12 h after inoculation 92±6% of the conidia had germ tubes. After 24 h of incubation, fully developed, sporulating mycelia were observed from both yeast cells and conidia. A delay in germ tube formation from yeast cells was observed when But₂cAMP(10 mM) and But₂cGMP (10 mM) were added to the medium. Also the addition of caffeine, a cyclic nucleotide phosphodiesterase inhibitor, inhibited the yeast to mycelial transition. Conidial germination into the mycelial form was also inhibited when cAMP, But₂cAMP and caffeine were added to the medium. These results suggest the possible involvement of cyclic nucleotides in the control of dimorphism in S. schenckii.     

Dominance and diet are unrelated within a population of invasive crayfish

Laboratory behavioral experiments are an important tool in ecology and evolution, but whether these behaviors reflect the field function of organisms is not always clear. Directly connecting laboratory behaviors to field interactions would increase understanding of a variety of organisms. A recent study proposed using stable isotopes to link laboratory behaviors to field function of individuals, but failed to find any such links within a population of the invasive rusty crayfish Faxonius rusticus (Girard, 1852). Here, we assessed whether methodological decisions around tissue analyzed for stable isotopes, laboratory acclimation time, and timing of primary consumer collection may have affected the result, hypothesizing that more dominant crayfish would have higher trophic positions and tissue with faster turnover rates may exhibit a stronger association between laboratory behavior and recent field function. We tested this relationship using F. rusticus individuals from a single population, and related laboratory dominance to stable isotope-derived trophic position using linear regression. We failed to find a relationship between dominance and trophic position, regardless of our different methodologies. Future studies should consider alternative behaviors that may better relate to function in the field and also investigate whether laboratory behavior and field function are related between, rather than within, populations or species.