Multiphase modelling of the effect of fluid shear stress on cell yield and distribution in a hollow fibre membrane bioreactor

We present a simplified two-dimensional model of fluid flow, nutrient transport and cell distribution in a hollow fibre membrane bioreactor, with the aim of exploring how fluid flow can be used to control the distribution and yield of a cell population which is sensitive to both fluid shear stress and nutrient concentration. The cells are seeded in a scaffold in a layer on top of the hollow fibre, only partially occupying the extracapillary space. Above this layer is a region of free-flowing fluid which we refer to as the upper fluid layer. The flow in the lumen and upper fluid layer is described by the Stokes equations, whilst the flow in the porous fibre membrane is assumed to follow Darcy’s law. Porous mixture theory is used to model the dynamics of and interactions between the cells, scaffold and fluid in the cell–scaffold construct. The concentration of a limiting nutrient (e.g. oxygen) is governed by an advection–reaction–diffusion equation in each region. Through exploitation of the small aspect ratio of each region and asymptotic analysis, we derive a coupled system of partial differential equations for the cell volume fraction and nutrient concentration. We use this model to investigate the effect of mechanotransduction on the distribution and yield of the cell population, by considering cases in which cell proliferation is either enhanced or limited by fluid shear stress and by varying experimentally controllable parameters such as flow rate and cell–scaffold construct thickness

Technical note: A simple theoretical model framework to describe plant stomatal "sluggishness" in response to elevated ozone concentrations

This is the final version. Available from European Geosciences Union (EGU) via the DOI in this record.Elevated levels of tropospheric ozone, O3, cause damage to terrestrial vegetation, affecting leaf stomatal functioning and reducing photosynthesis. Climatic impacts under future raised atmospheric greenhouse gas (GHG) concentrations will also impact on the net primary productivity (NPP) of vegetation, which might for instance alter viability of some crops. Together, ozone damage and climate change may adjust the current ability of terrestrial vegetation to offset a significant fraction of carbon dioxide (CO2) emissions. Climate impacts on the land surface are well studied, but arguably large-scale modelling of raised surface level O3effects is less advanced. To date most models representing ozone damage use either O3concentration or, more recently, flux-uptake-related reduction of stomatal opening, estimating suppressed land-atmosphere water and CO2fluxes. However there is evidence that, for some species, O3damage can also cause an inertial sluggishness of stomatal response to changing surface meteorological conditions. In some circumstances (e.g. droughts), this loss of stomata control can cause them to be more open than without ozone interference. To both aid model development and provide empiricists with a system on to which measurements can be mapped, we present a parameter-sparse framework specifically designed to capture sluggishness. This contains a single time-delay parameter τO3, characterizing the timescale for stomata to catch up with the level of opening they would have without damage. The larger the value of this parameter, the more sluggish the modelled stomatal response. Through variation of τO3, we find it is possible to have qualitatively similar responses to factorial experiments with and without raised O3, when comparing to reported measurement time series presented in the literature. This low-parameter approach lends itself to the inclusion of ozone-induced inertial effects being incorporated in the terrestrial vegetation component of Earth system models (ESMs).NERC-CEH National Capability FundNatural Environment Research Counci

Legume based plant mixtures for delivery of multiple ecosystem services: An overview of benefits

As costs for mineral fertilizers rise, legume-based leys are recognised as a potential alternative nitrogen source for crops. Here we demonstrate that including species-rich legume-based leys in the rotation helps to maximize synergies between agricultural productivity and other ecosystem services. By using functionally diverse plant species mixtures these services can be optimised and fine-tuned to regional and farm-specific needs. Field experiments run over three years at multiple locations showed that the stability of ley performance was greater in multi-species mixtures than in legume monocultures. In addition, mixing different legume species in the ley helps to suppress both early and late weeds. Further, combining complementary phenologies of different legume species extended forage availability for key pollinator species. Finally, widening the range of legume species increases opportunities to build short term leys into rotations on conventional farms via cover cropping or undersowing

Microbial micropatches within microbial hotspots

© 2018 Dann et al. This is an open access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited. The spatial distributions of organism abundance and diversity are often heterogeneous. This includes the sub-centimetre distributions of microbes, which have ‘hotspots’ of high abundance, and ‘coldspots’ of low abundance. Previously we showed that 300 μl abundance hotspots, coldspots and background regions were distinct at all taxonomic levels. Here we build on these results by showing taxonomic micropatches within these 300 μl microscale hotspots, coldspots and background regions at the 1 μl scale. This heterogeneity among 1 μl subsamples was driven by heightened abundance of specific genera. The micropatches were most pronounced within hotspots. Micropatches were dominated by Pseudomonas, Bacteroides, Parasporobacterium and Lachnospiraceae incertae sedis, with Pseudomonas and Bacteroides being responsible for a shift in the most dominant genera in individual hotspot subsamples, representing up to 80.6% and 47.3% average abundance, respectively. The presence of these micropatches implies the ability these groups have to create, establish themselves in, or exploit heterogeneous microenvironments. These genera are often particle-associated, from which we infer that these micropatches are evidence for sub-millimetre aggregates and the aquatic polymer matrix. These findings support the emerging paradigm that the microscale distributions of planktonic microbes are numerically and taxonomically heterogeneous at scales of millimetres and less. We show that microscale microbial hotspots have internal structure within which specific local nutrient exchanges and cellular interactions might occur

Parent perceived barriers and facilitators of children's adventurous play in Britain: a framework analysis

This is the final version. Available on open access from BMC via the DOI in this recordAvailability of data and materials: The data obtained and analysed in the current study are available via the following link: https://doi.org/10.5255/UKDA-SN-8793-1.BACKGROUND: From a public health perspective there is growing interest in children's play, including play involving risk and adventure, in relation to children's physical and mental health. Regarding mental health, it is theorised that adventurous play, where children experience thrilling, exciting emotions, offers important learning opportunities that prepare children for dealing with uncertainty and help prevent anxiety. Despite these benefits, adventurous play has decreased substantially within a generation. Parents have a key role in facilitating or limiting children's opportunities for adventurous play, but research identifying the barriers and facilitators parents perceive in relation to adventurous play is scarce. The present study therefore examined the barriers to and facilitators of adventurous play as perceived by parents of school-aged children in Britain. METHODS: This study analysed data from a subsample of parents in Britain (n = 377) who participated in the nationally representative British Children's Play Survey. Parents responded to two open-ended questions pertaining to the barriers to and facilitators of children's adventurous play. Responses were analysed using a qualitative Framework Analysis, an approach suitable for managing large datasets with specific research questions. RESULTS: Four framework categories were identified: Social Environment; Physical Environment; Risk of Injury; Child Factors. Social Environment included barriers and facilitators related to parents, family and peers, as well as community and society. Dominant themes within the Social Environment related to perceptions about the certainty of child safety, such as supervision and the safety of society. Beliefs about the benefits of adventurous play for development and well-being were also important in the Social Environment. Physical Environment factors focused on safety and practical issues. Risk of Injury captured concerns about children being injured during play. Child Factors included child attributes, such as play preference, developmental ability and trait-like characteristics. CONCLUSIONS: Improved understanding of what influences parent perceptions of adventurous play can inform public health interventions designed to improve children's opportunities for and engagement in adventurous play, with a view to promote children's physical and mental health.Economic and Social Research Council (ESRC)UKR

Classifying the unclassifiable – A Delphi study to reach consensus on the fibrotic nature of diseases

Background Traditionally, clinical research has focused on individual fibrotic diseases or fibrosis in a particular organ. However, it is possible for people to have multiple fibrotic diseases. While multi-organ fibrosis may suggest shared pathogenic mechanisms, yet there is no consensus on what constitutes a fibrotic disease and therefore fibrotic multimorbidity. Aim A Delphi study was performed to reach consensus on which diseases may be described as fibrotic. Methods Participants were asked to rate a list of diseases, sub-grouped according to eight body regions, as ‘fibrotic manifestation always present’, ‘can develop fibrotic manifestations’, ‘associated with fibrotic manifestations’ or ‘not fibrotic nor associated’. Classifications of ‘fibrotic manifestation always present’ and ‘can develop fibrotic manifestations’ were merged and termed ‘fibrotic’. Clinical consensus was defined according to the interquartile range, having met a minimum number of responses. Clinical agreement was used for classification where diseases did not meet the minimum number of responses (required for consensus measure), were only classified if there was 100% consensus on disease classification. Results After consulting experts, searching the literature and coding dictionaries, a total of 323 non-overlapping diseases which might be considered fibrotic were identified; 92 clinical specialists responded to the first round of the survey. Over three survey rounds, 240 diseases were categorized as fibrotic via clinical consensus and 25 additional diseases through clinical agreement. Conclusion Using a robust methodology, an extensive list of diseases was classified. The findings lay the foundations for studies estimating the burden of fibrotic multimorbidity, as well as investigating shared mechanisms and therapies

Trypanosoma brucei gambiense group 1 is distinguished by a unique amino acid substitution in the HpHb receptor implicated in human serum resistance

Trypanosoma brucei rhodesiense (Tbr) and T. b. gambiense (Tbg), causative agents of Human African Trypanosomiasis (sleeping sickness) in Africa, have evolved alternative mechanisms of resisting the activity of trypanosome lytic factors (TLFs), components of innate immunity in human serum that protect against infection by other African trypanosomes. In Tbr, lytic activity is suppressed by the Tbr-specific serum-resistance associated (SRA) protein. The mechanism in Tbg is less well understood but has been hypothesized to involve altered activity and expression of haptoglobin haemoglobin receptor (HpHbR). HpHbR has been shown to facilitate internalization of TLF-1 in T.b. brucei (Tbb), a member of the T. brucei species complex that is susceptible to human serum. By evaluating the genetic variability of HpHbR in a comprehensive geographical and taxonomic context, we show that a single substitution that replaces leucine with serine at position 210 is conserved in the most widespread form of Tbg (Tbg group 1) and not found in related taxa, which are either human serum susceptible (Tbb) or known to resist lysis via an alternative mechanism (Tbr and Tbg group 2). We hypothesize that this single substitution contributes to reduced uptake of TLF and thus may play a key role in conferring serum resistance to Tbg group 1. In contrast, similarity in HpHbR sequence among isolates of Tbg group 2 and Tbb/Tbr provides further evidence that human serum resistance in Tbg group 2 is likely independent of HpHbR functio

Anion exchange dynamics in the capture of perchlorate by a cationic Ag-based MOF

The perchlorate capture process by a cationic Ag-based MOF was carefully studied using a combination of powder X-ray diffraction (PXRD), multinuclear 13C, 15N and 109Ag solid state NMR and SEM.</p