Circular economy: A new research field?

Action to pursue the circular economy (CE) transition is burgeoning in the government and the private sector. Does this action signal that CE is a distinct field of research with a unique disciplinary identity? This article argues that CE has reached field status, through its own epistemic communities characterized by increasingly shared methodological perspectives and normative ideals, and through institutionalized knowledge development through research journals and authority structures. The recent growth of CE research points toward more contextualized and nuanced operationalizations of the concept, evidence that the field is approaching a threshold state of maturity. Drawing on observations from academic literature and discussions with researchers and experts, we trace the process by which CE has arrived at the status of a field. The article concludes with reflections on research directions.     

Endogenous butyrylcholinesterase in SV40 transformed cell lines: COS-1, COS-7, MRC-5 SV40, and WI-38 VA13

Summary Comparison of proteins expressed by SV40 transformed cell lines and untransformed cell lines is of interest because SV40 transformed cells are immortal, whereas untransformed cells senesce after about 50 doublings. In MRC-5 SV40 cells, only seven proteins have previously been reported to shift from undetectable to detectable after transformation by SV40 virus. We report that butyrylcholinesterase is an 8th protein in this category. Butyrylcholinesterase activity in transformed MRC-5 SV40 cells increased at least 150-fold over its undetectable level in MRC-5 parental cells. Other SV40 transformed cell lines, including COS-1, COS-7, and WI-38 VA13, also expressed endogenous butyrylcholinesterase, whereas the parental, untransformed cell lines, CV-1 and WI-38, had no detectable butyrylcholinesterase activity or mRNA. Infection of CV-1 cells by SV40 virus did not result in expression of butyrylcholinesterase, showing that the butyrylcholinesterase promoter was not activated by the large T antigen of SV40. We conclude that butyrylcholinesterase expression resulted from events related to cell immortalization and did not result from activation by the large T antigen.     

Solubilization of the receptor for the neuropeptide gastrin-releasing peptide (bombesin) with functional ligand binding properties

The receptor for the neuropeptide gastrin-releasing peptide, the mammalian homologue of bombesin, was solubilized from rat brain and Swiss 3T3 cells by using the zwitterionic detergent 3-[(3-cholamidopropyl)dimethylammonio]-1-propanesulfonic acid (CHAPS) and the cholesteryl hemisuccinate ester (CHS). Only the combination of the detergent CHAPS and the cholesteryl ester CHS in a glycerol-containing buffer satisfactorily preserved the binding activity upon solubilization. Specific binding activity was only solubilized from cell lines and tissue preparations known to express the GRP receptor. The dissociation constant (Kd) for the receptor solubilized from rat brain and Swiss 3T3 cells was 0.6 nM, similar to the value of 0.8 nM calculated for the membrane-bound receptor. Binding was saturable and reached equilibrium after approximately 2 h at 4 degrees C. The identity of the solubilized receptor with the membrane-bound one was further confirmed by the concordance of the relative binding affinities of various established bombesin analogues.     

Patterns of population genetic diversity in riparian and aquatic plant species along rivers

Aim The downstream hydrochoric spread of seeds of aquatic and riparian plant species, without upstream compensation, can be expected to result in downstream accumulation of population genetic diversity. This idea has been termed the ‘unidirectional dispersal hypothesis’ and is the genetic equivalent of the more generally known ‘drift paradox’. Our aim was to test this unidirectional diversity hypothesis, and to present a general synthesis of the patterns of population genetic variation across different riparian and aquatic plant species along rivers. Location The Meuse River (Belgium) and rivers world‐wide. Methods First, we used amplified fragment length polymorphism markers to compare patterns of within‐ and between‐population genetic diversity among three riparian plant species (Sisymbrium austriacum, Erysimum cheiranthoides and Rorippa sylvestris), typically occurring in different habitats along a gradient perpendicular to the Meuse River. Second, we performed a meta‐analysis on studies reporting on the population genetic structure of riparian and aquatic plant species along rivers. Results Along the Meuse River, we found significant genetic differentiation among populations of all three riparian species, and significant isolation by distance for one of them (R. sylvestris). There was no clear association between the typical habitat of a species and its population genetic structure. None of the three species provided evidence for the unidirectional dispersal hypothesis. The meta‐analysis, based on 21 data records, did not support the unidirectional dispersal hypothesis either. Average weighted population genetic differentiation across species was significant. Main conclusions Important mechanisms of upstream seed dispersal, probably through zoochory, together with higher seed recruitment opportunities in upstream habitats due to density dependence of recruitment, may explain the absence of downstream accumulation of genetic diversity. Also, it seems difficult to find consistent patterns in genetic variation in species from aquatic and riparian habitats. We argue that this is due to the recurrent extinctions and colonizations characteristic of these habitats, resulting in complex genetic patterns. Our results strongly support previous suggestions that stream ecology should consistently embrace metapopulation theory to be able to understand patterns of genetic diversity, as well as species diversity.     

Woodland regeneration on grazed former arable land: A question of tolerance,defence or protection?

Ecological restoration of native woodlands and wooded pastures on former agricultural land is an important topic in modern conservation practice. The introduction of large herbivores is increasingly used to achieve these aims. We investigated how grazing, resistance traits of plants (concerning herbivory) and associational resistance interact and affect the establishment pattern of woody species on abandoned arable land (N-Belgium, W-Europe). In these early successional tree assemblages, we tested whether grazing increased or decreased spatial heterogeneity, which is supposed to be a crucial factor for biodiversity.With repeated measurements, 2-3 and 5-7 years after the cessation of agricultural use, we sampled 87 grazed and 56 ungrazed plots (314 m²) in 14 sampling areas (former arable land) on nutrient rich, (sandy) loam soils. We recorded established tree frequencies, related to grazing, time, resistance traits and unpalatable/spiny vegetation cover in the herb and low shrub layer. We investigated horizontal and vertical heterogeneity using variances in establishment frequencies and variances in frequencies of trees that were able to grow beyond the browse line, respectively.We found massive colonisation of grazing tolerant and resistant woody species in early successional stages. Grazing decreased frequencies and height of the most abundant tolerant species (mainly Salix caprea L.). After 5-7 years, frequencies of defensive and tolerant species were equal, but the former (mainly Betula pendula Roth) were able to grow beyond the browse line. When the cover of unpalatable/spiny vegetation was high enough (>60% of plot size), it also provided suitable nurse sites for tolerant species to grow out. In early assemblages, grazing increased horizontal and vertical heterogeneity, resulting in intermediate successional stages. In the long-term, the mechanism of associational resistance will also allow non-resistant and tolerant species to grow beyond the browse line and promote forest succession and the order of species establishment and replacement.     

Limnological and ecological sensitivity of Rwenzori mountain lakes to climate warming

An increasing number of studies forecast that anthropogenic climate change poses serious consequences for the biodiversity and ecosystem functioning of high-elevation mountain lakes, through a series of both direct and indirect effects. The impacts of future climate warming on alpine ecosystems are of particular concern, given that warming is expected to be most pronounced at high elevations around the globe. Here, we evaluate the limnological and ecological sensitivity of high-elevation lakes in the Rwenzori Mountains (Uganda-D. R. Congo) to climate change. This is done by comparing the species assemblages of larval chironomid remains deposited recently in lake sediments with those deposited at the base of short cores (dated to within or shortly after the Little Ice Age) in 16 lakes. Chironomid-based reconstructions of mean annual air temperature (MATemp) are made using a variety of inference models (with transfer functions based on weighted averaging, weighted-averaging partial least squares, and a weighted modern analogue technique), and two different calibration data sets, one covering the full regional temperature gradient and one comprising only high-elevation Rwenzori lakes and ponds. The reconstructed historical temperature change ranges between a cooling of −2.03°C and a warming of +3.22°C (with n = 16 lakes × 3 models × 2 calibration data sets). However, excluding the atypical mid-elevation lake Mahoma (2,990 m altitude), we find a three-to-one ratio of cases of inferred warming against inferred cooling, and of the 24 Δ MATemp values exceeding 0.60°C, 23 are positive and only one is negative. Chironomid-inferred temperature changes mostly fall within the error range of the regional temperature inference models. A generalized linear mixed model analysis of the combined result from all lakes (except Mahoma) nevertheless indicates significantly warmer MATemp (on average +0.38 ± 0.11°C) at present compared to between ~85 and ~645 years ago. Inferred temperature changes are independent of whether lakes are located in glaciated or non-glaciated catchments, and of the age of the core base, suggesting that at least part of the signal is due to relatively recent, anthropogenic warming. The direction of faunal change at the lakes in relation to established species–environment relationships suggests that part of the observed shifts in species composition reflect lake-specific evolution in habitat features other than temperature, such as nutrients, pH or oxygen regime, which in our present calibration data set co-vary with temperature to a greater or lesser extent. The fairly uniform and marked historical warming trend in Rwenzori lakes documented by this study highlights their ecological vulnerability and their value as early warning systems for detecting the limnological and ecological effects of global warming.     

Peptizer, a tool for assessing false positive peptide identifications and manually validating selected results

False positive peptide identifications are a major concern in the field of peptidecentric, mass spectrometry-driven gel-free proteomics. They occur in regions where the score distributions of true positives and true negatives overlap. Removal of these false positive identifications necessarily involves a trade-off between sensitivity and specificity. Existing postprocessing tools typically rely on a fixed or semifixed set of assumptions in their attempts to optimize both the sensitivity and the specificity of peptide and protein identification using MS/MS spectra. Because of the expanding diversity in available proteomics technologies, however, these postprocessing tools often struggle to adapt to emerging technology-specific peculiarity. Here we present a novel tool named Peptizer that solves this adaptability issue by making use of pluggable assumptions. This research-oriented postprocessing tool also includes a graphical user interface to perform efficient manual validation of suspect identifications for optimal sensitivity recovery. Peptizer is open source software under the Apache2 license and is written in Java.     

Gene expression-based survival prediction in lung adenocarcinoma: a multi-site, blinded validation study

Although prognostic gene expression signatures for survival in early-stage lung cancer have been proposed, for clinical application, it is critical to establish their performance across different subject populations and in different laboratories. Here we report a large, training-testing, multi-site, blinded validation study to characterize the performance of several prognostic models based on gene expression for 442 lung adenocarcinomas. The hypotheses proposed examined whether microarray measurements of gene expression either alone or combined with basic clinical covariates (stage, age, sex) could be used to predict overall survival in lung cancer subjects. Several models examined produced risk scores that substantially correlated with actual subject outcome. Most methods performed better with clinical data, supporting the combined use of clinical and molecular information when building prognostic models for early-stage lung cancer. This study also provides the largest available set of microarray data with extensive pathological and clinical annotation for lung adenocarcinomas.     

Effects of landscape structure on the invasive spread of black cherry Prunus serotina in an agricultural landscape in Flanders, Belgium

Analysing invasive spread from a landscape ecological perspective forms an important challenge in plant invasion ecology. The present study examines the effects of landscape structure on the spatial and temporal dynamics of an expanding black cherry Prunus serotina population within a rural landscape in Flanders, Belgium, carrying a dense network of interconnected hedgerows. The study area, 251 ha in size, harboured a total of 2962 P. serotina individuals. The population was characterised by a negative exponential age distribution, a high growth rate and an early and continuous reproduction throughout the species' life cycle. The historical rate of spread of the species through the hedgerow network progressively increased with time, especially during the last decade. Spatial point pattern analysis revealed that the individuals had a significantly clustered distribution pattern and were spatially aggregated around seed sources, hedgerow intersections and roosting trees. Logistic regression analysis confirmed the effect of landscape structure on P. serotina occurrence, suggesting directional long distance dispersal by avian dispersal vectors, resulting in a differential seed pressure throughout the hedgerow network due to the preference of dispersing birds for roosting in structurally rich hedgerow with large trees near hedgerow intersections. Hence, the distribution of P. serotina in agricultural landscapes was strongly mediated by dispersal processes. Furthermore, decreasing spatial aggregation along the species life cycle, with especially seedlings and saplings being significantly aggregated while adult individuals were mostly distributed at random, and a relative outward shift of seedling recruitment curves with time indicate density dependent mortality, probably caused by intraspecific competition.