Adaptation to the Edge of Chaos in the Self-Adjusting Logistic Map

Self-adjusting, or adaptive systems have gathered much recent interest. We present a model for self-adjusting systems which treats the control parameters of the system as slowly varying, rather than constant. The dynamics of these parameters is governed by a low-pass filtered feedback from the dynamical variables of the system. We apply this model to the logistic map and examine the behavior of the control parameter. We find that the parameter leaves the chaotic regime. We observe a high probability of finding the parameter at the boundary between periodicity and chaos. We therefore find that this system exhibits adaptation to the edge of chaos.Comment: 3 figure

Xrp1 and Irbp18 trigger a feed-forward loop of proteotoxic stress to induce the loser status

Cell competition induces the elimination of less-fit “loser” cells by fitter “winner” cells. In Drosophila, cells heterozygous mutant in ribosome genes, Rp/+, known as Minutes, are outcompeted by wild-type cells. Rp/+ cells display proteotoxic stress and the oxidative stress response, which drive the loser status. Minute cell competition also requires the transcription factors Irbp18 and Xrp1, but how these contribute to the loser status is partially understood. Here we provide evidence that initial proteotoxic stress in RpS3/+ cells is Xrp1-independent. However, Xrp1 is sufficient to induce proteotoxic stress in otherwise wild-type cells and is necessary for the high levels of proteotoxic stress found in RpS3/+ cells. Surprisingly, Xrp1 is also induced downstream of proteotoxic stress, and is required for the competitive elimination of cells suffering from proteotoxic stress or overexpressing Nrf2. Our data suggests that a feed-forward loop between Xrp1, proteotoxic stress, and Nrf2 drives Minute cells to become losers

Method for volumetric assessment of edge-wear in ceramic-on-ceramic acetabular liners

This paper details a novel method to characterize and quantify edge wear patterns in ceramic-on-ceramic acetabular liners using a roundness measurement machine to measure the post-wear surface. A 3D surface map is produced which encompasses the measured surface covering the wear patch, the uncontrolled edge geometry and form of the bearing surface. The data is analysed to quantify linear penetration and volume. The developed method was applied in a blind study to a set of six 36 mm ceramic- on-ceramic acetabular cup liners that were measured and analysed to characterise the edge wear. The in-vitro linear wear penetration ranged from 10 μm to 30 μm. The computed volumetric wear results obtained from the blind roundness measurement study were compared against the measured gravimetric results indicating a strong correlation between the results (0.9846). This study has also highlighted that measured liners exhibited an area of localised edge wear locates above the bearing surface as well as a smearing effect on the bearing surface caused by debris from edge wear. A study was carried out to test the repeatability of the measurement method and the inter-operator variability of the analysis. The results of the study show a standard deviation for the entire measurement and analysis process of 0.009 mm3 for first user and 0.003 mm3 for second user over twenty datasets. Hence the method displays high repeatability of the measurement and analysis process between users. This method allows for the delineation of form and wear through the determination of local geometry changes on what is essentially a freeform surface. The edge geometry is only partially controlled from a GD&T perspective and its geometry relative to the bearing surface varies from part-to-part. This method whilst being subjective allows for the determination of wear in this area with a high level of repeatability. However the limitation of this method is that it can only measure 5mm wide band of the liner due to the limited gauge travel range of 2mm

Proteotoxic stress is a driver of the loser status and of cell competition

Cell competition allows “winner” cells to eliminate less fit “loser” cells in tissues. In Minute cell competition, cells heterozygous mutant in ribosome genes, such as RpS3 (+/-) cells, are eliminated by wild-type cells. How cells are primed as losers is partially understood and it has been proposed that reduced translation underpins the loser status of ribosome mutant, or Minute, cells. Here, using Drosophila, we show that reduced translation does not cause cell competition. Instead, we identify proteotoxic stress as the underlying cause of the loser status for Minute competition and competition induced by mahjong, an unrelated loser gene. RpS3 (+/-) cells exhibit reduced autophagic and proteasomal flux, accumulate protein aggregates, and can be rescued from competition by improving their proteostasis. Conversely, inducing proteotoxic stress is sufficient to turn otherwise wild-type cells into losers. Thus, we propose that tissues may preserve their health through a proteostasis-based mechanism of cell competition and cell selection

The potential of coffee stems gasification to provide bioenergy for coffee farms:a case study in the Colombian coffee sector

The coffee industry constitutes an important part of the global economy. Developing countries produce over 90% of world coffee production, generating incomes for around 25 million smallholder farmers. The scale of this industry poses a challenge with the generation of residues along with the coffee cultivation and processing chain. Coffee stems, obtained after pruning of coffee trees, are one of those abundant and untapped resources in the coffee supply chain. Their high lignocellulosic content, the low calorific value ranging between 17.5 and 18 MJ kg−1 and the low ash content make them a suitable solid fuel for thermochemical conversion, such as gasification. This research evaluates the feasibility of using these residues in small-scale downdraft gasifiers coupled to internal combustion engines for power and low-grade heat generation, using process modelling and the Colombian coffee sector as a case study. The producer gas properties (5.6 MJ Nm−3) and the gasifier’s performance characteristics suggest that this gas could be utilized for power generation. A cogeneration system efficiency of 45.6% could be attainable when the system’s low-grade heat is recovered for external applications, like in the coffee drying stage. An analysis of the energy demand and coffee stems availability within the Colombian coffee sector shows that the biomass production level in medium- to large-scale coffee farms is well matched to their energy demands, offering particularly attractive opportunities to deploy this bioenergy system. This work assesses the feasibility of providing coffee stem–sourced low-carbon energy for global coffee production at relevant operating scales in rural areas

Proteotoxic stress is a driver of the loser status and cell competition.

Cell competition allows winner cells to eliminate less fit loser cells in tissues. In Minute cell competition, cells with a heterozygous mutation in ribosome genes, such as RpS3+/- cells, are eliminated by wild-type cells. How cells are primed as losers is partially understood and it has been proposed that reduced translation underpins the loser status of ribosome mutant, or Minute, cells. Here, using Drosophila, we show that reduced translation does not cause cell competition. Instead, we identify proteotoxic stress as the underlying cause of the loser status for Minute competition and competition induced by mahjong, an unrelated loser gene. RpS3+/- cells exhibit reduced autophagic and proteasomal flux, accumulate protein aggregates and can be rescued from competition by improving their proteostasis. Conversely, inducing proteotoxic stress is sufficient to turn otherwise wild-type cells into losers. Thus, we propose that tissues may preserve their health through a proteostasis-based mechanism of cell competition and cell selection

Absence of effects of widespread badger culling on tuberculosis in cattle

Government policy in England aims for the elimination of bovine tuberculosis (bTB). This policy includes culling of European badger (Meles meles) to reduce cattle TB incidence. The rationale is based on a field trial, the Randomised Badger Culling Trial (RBCT) 1998–2005, which reported a substantial decrease in bTB herd incidence where badger culling had been implemented, in comparison to untreated control areas. The RBCT was undertaken because previous studies of reductions in badgers by culling, reported a possible association between bTB in badger and cattle, but none could directly show causation. The effect of intensive widespread (proactive) culling in the RBCT was reported in 2006 in the journal Nature. Analysis of an extensive badger removal programme in England since 2013 has raised concerns that culling has not reduced bTB herd incidence. The present study re-examined RBCT data using a range of statistical models. Most analytical options showed no evidence to support an effect of badger culling on bTB herd incidence ‘confirmed’ by visible lesions and/or bacterial culture post mortem following a comparative intradermal skin test (SICCT). However, the statistical model chosen by the RBCT study was one of the few models that showed an effect. Various criteria suggest that this was not an optimal model, compared to other analytical options available. The most likely explanation is that the RBCT proactive cull analysis over-fitted the data with a non-standard method to control for exposure giving it a poor predictive value. Fresh appraisal shows that there was insufficient evidence to conclude RBCT proactive badger culling affected bTB breakdown incidence. The RBCT found no evidence of an effect of culling on ‘total’ herd incidence rates. Total herd incidences include those confirmed as bTB at necropsy and those herds where there was at least one animal animal positive to the comparative intradermal skin test, the standard diagnostic test used for routine surveillance, but not confirmed at necropsy. This was also the case using the more suitable statistical models. Use only of ‘confirmed’ herd incidence data, together with a more recent (2013) published perception that RBCT data presented ‘a strong evidence base….with appropriate detailed statistical or other quantitative analysis’ should be reconsidered. The results of the present report are consistent with other analyses that were unable to detect any disease control benefits from badger culling in England (2013–2019). This study demonstrates one form of potential driver to the reproducibility crisis, in this case with disease control management in an increasingly intensified livestock industry

Governance and Susceptibility in Conflict Resolution: Possibilities Beyond Control

Governmentality analysis offers a nuanced critique of informal Western conflict resolution by arguing that recently emerged alternatives to adversarial court processes both govern subjects and help to constitute rather than challenge formal regulation. However, this analysis neglects possibilities for transforming governance from within conflict resolution that are suggested by Foucault's contention that there are no relations of power without resistances. To explore this lacuna, I theorise and explore the affective and interpersonal nature of governance in mediation through autoethnographic reflection upon mediation practice, and Levina's insights about the relatedness of selves. The paper argues that two qualitatively different mediator capacities - technical ability and susceptibility - operate in concert to effect liberal governance. Occasionally though, difficulties and failures in mediation practice bring these capacities into tension and reveal the limits of governance. By considering these limits in mediation with Aboriginal Australian people, I argue that the susceptibility of mediator selves contains prospects for mitigating and transforming the very operations of power occurring through conflict resolution. This suggests options for expanded critical thinking about power relations operating through informal processes, and for cultivating a susceptible sensibility to mitigate liberal governance and more ethically respond to difference through conflict resolution

Randomised Badger Culling Trial—no effects of widespread badger culling on tuberculosis in cattle: comment on Mills, Woodroffe and Donnelly (2024a, 2024b)

Substantial problems remain with the Mills et al. (Mills CL, Woodroffe R, Donnelly CA. 2024 R. Soc. Open Sci. 11, 240385. (doi:10.1098/rsos.240385) and Mills CL, Woodroffe R, Donnelly CA. 2024 R. Soc. Open Sci. 11, 240386. (doi:10.1098/rsos.240386)) re-evaluations of the Randomised Badger Culling Trial (RBCT) data. These include: (i) analysis of counts rather than rates; (ii) overfitting; (iii) modelling of ‘confirmed’ herd breakdowns rather than total herd breakdowns; and (iv) errors in the Bayesian analysis of the data. More plausible approaches to RBCT data analysis, including analysis of total breakdown incidence, strongly suggest that there is no effect of proactive badger culling on the herd incidence of bovine tuberculosis, either within cull areas or in neighbouring areas