Maladaptation and the paradox of robustness in evolution

Background. Organisms use a variety of mechanisms to protect themselves against perturbations. For example, repair mechanisms fix damage, feedback loops keep homeostatic systems at their setpoints, and biochemical filters distinguish signal from noise. Such buffering mechanisms are often discussed in terms of robustness, which may be measured by reduced sensitivity of performance to perturbations. Methodology/Principal Findings. I use a mathematical model to analyze the evolutionary dynamics of robustness in order to understand aspects of organismal design by natural selection. I focus on two characters: one character performs an adaptive task; the other character buffers the performance of the first character against perturbations. Increased perturbations favor enhanced buffering and robustness, which in turn decreases sensitivity and reduces the intensity of natural selection on the adaptive character. Reduced selective pressure on the adaptive character often leads to a less costly, lower performance trait. Conclusions/Significance. The paradox of robustness arises from evolutionary dynamics: enhanced robustness causes an evolutionary reduction in the adaptive performance of the target character, leading to a degree of maladaptation compared to what could be achieved by natural selection in the absence of robustness mechanisms. Over evolutionary time, buffering traits may become layered on top of each other, while the underlying adaptive traits become replaced by cheaper, lower performance components. The paradox of robustness has widespread implications for understanding organismal design

Pancreatitis following liver transplantation

Since 1981, when the liver transplantation program was initiated at the University of Pittsburgh, we have been impressed with the prevalence of pancreatitis occurring following liver transplantation in patients transplanted for hepatitis B—related liver disease. To either confirm this clinical impression or refute it, the records of the 27 HbsAg+ patients and those of an additional 24 HbsAg“but HbcAb and/or HbsAb+ patients who underwent orthotopic liver transplantation were reviewed to determine the prevalence of clinical pancreatitis and hyperamylasemia (biochemical pancreatitis) following liver transplantation (OLTx). Post-OLTx hyperamylasemia occurred significantly more frequently in HbsAg+ patients (6/27) than it did in the HbsAg- patients (0/24) (P<0.05). More importantly, clinical pancreatitis occurred in 14% (4/27) of the HbsAg+ patients and 0% (0/24) of the HbsAg- patients. Interestingly, in each case, the pancreatitis was associated with the occurrence of acute hepatitis B infection of the allograft. Based upon these data, we conclude that pancreatitis occurring after liver transplantation is more common in patients transplanted for active viral liver disease caused by hepatitis B than in those with inactive viral liver disease. These observations suggest that pancreatitis occurring in, at least some cases following liver transplantation for viral liver disease, may result from hepatitis B virus infection of the pancreas. © 1988 by The Williams and Wilkins Co

Efficient Mixing at low Reynolds numbers using polymer additives

Mixing in fluids is a rapidly developing field of fluid mechanics \cite{Sreen,Shr,War}, being an important industrial and environmental problem. The mixing of liquids at low Reynolds numbers is usually quite weak in simple flows, and it requires special devices to be efficient. Recently, the problem of mixing was solved analytically for a simple case of random flow, known as the Batchelor regime \cite{Bat,Kraich,Fal,Sig,Fouxon}. Here we demonstrate experimentally that very viscous liquids at low Reynolds number, $Re$. Here we show that very viscous liquids containing a small amount of high molecular weight polymers can be mixed quite efficiently at very low Reynolds numbers, for a simple flow in a curved channel. A polymer concentration of only 0.001% suffices. The presence of the polymers leads to an elastic instability \cite{LMS} and to irregular flow \cite{Ours}, with velocity spectra corresponding to the Batchelor regime \cite{Bat,Kraich,Fal,Sig,Fouxon}. Our detailed observations of the mixing in this regime enable us to confirm sevearl important theoretical predictions: the probability distributions of the concentration exhibit exponential tails \cite{Fal,Fouxon}, moments of the distribution decay exponentially along the flow \cite{Fouxon}, and the spatial correlation function of concentration decays logarithmically.Comment: 11 pages, 5 figure

High-resolution monochromated electron energy-loss spectroscopy of organic photovoltaic materials

Advances in electron monochromator technology are providing opportunities for high energy resolution (10 – 200 meV) electron energy-loss spectroscopy (EELS) to be performed in the scanning transmission electron microscope (STEM). The energy-loss near-edge structure in core-loss spectroscopy is often limited by core-hole lifetimes rather than the energy spread of the incident illumination. However, in the valence-loss region, the reduced width of the zero loss peak makes it possible to resolve clearly and unambiguously spectral features at very low energy-losses (<3 eV). In this contribution, high-resolution EELS was used to investigate four materials commonly used in organic photovoltaics (OPVs): poly(3-hexlythiophene) (P3HT), [6,6] phenyl-C61 butyric acid methyl ester (PCBM), copper phthalocyanine (CuPc), and fullerene (C60). Data was collected on two different monochromated instruments – a Nion UltraSTEM 100 MC ‘HERMES’ and a FEI Titan3 60–300 Image-Corrected S/TEM – using energy resolutions (as defined by the zero loss peak full-width at half-maximum) of 35 meV and 175 meV, respectively. The data was acquired to allow deconvolution of plural scattering, and Kramers–Kronig analysis was utilized to extract the complex dielectric functions. The real and imaginary parts of the complex dielectric functions obtained from the two instruments were compared to evaluate if the enhanced resolution in the Nion provides new opto-electronic information for these organic materials. The differences between the spectra are discussed, and the implications for STEM-EELS studies of advanced materials are considered

Development of a road map for Lean Six Sigma implementation and sustainability in a Scottish packaging company

Purpose: Lean Six Sigma (LSS) is a continuous improvement (CI) methodology that has been adopted by several companies as a strategy to increase their competitive advantage. However due to the misuse of LSS theory in practice, a high rate of implementation failure occurs in many organisations today. There is a need for a structured and standardized framework to describe how the LSS initiative should be implemented and sustained over time. As a result, this study aims to develop a practical, user-friendly and accurate LSS roadmap for a Scottish manufacturing Small and Medium Enterprise (SME). Design/ methodology/ approach: This approach was to analyse existing literature on Lean and Six Sigma that included roadmaps and critical success factors (CSFs). An incompany survey instrument was designed to collect quantitative data. The aim of the survey was to evaluate employees’ perceptions on the importance of LSS CSFs for the successful implementation and sustainability of a CI initiative. Based on the literature and the results from the data collected, a LSS reference guide - in the form of a roadmap - was designed to support LSS implementation and sustainability. Findings: A customised LSS reference guide in a roadmap format for the Scottish SME was proposed. This roadmap was developed by adopting existing successful roadmaps from the literature into consideration and then adapting them to fulfil the company’s particular perspective on CI. This study complements current literature on LSS roadmaps and corroborates LSS CSFs as crucial for successful LSS implementation and sustainability, regardless of the type of company and/or culture. However, a degree of importance is ascribed to the organisational culture. Research limitations: Whilst a survey was used as the data collection instrument, future interviews with employees may enhance the understanding of the organisational culture and further improved the roadmap. Originality/ Value: The authors developed a practical and strategic roadmap for a Scottish packaging Small and Medium Sized Enterprise (SME) which can be used by other similar SMEs. The proposed LSS roadmap can be replicated and/or adapted for companies in their application of LSS. The methodology by which this study’s roadmap was designed can be used as a guide in the development of further CI roadmaps

A combinatorial nanoprecursor route for direct solid state chemistry: Discovery and electronic properties of new iron-doped lanthanum nickelates up to La4Ni2FeO10-delta

We describe a simple nanoprecursor route for direct solid-state combinatorial synthesis and discovery of heterometallic materials compositions which are normally difficult to make in a single step. Using a combinatorial robot (incorporating a continuous hydrothermal reactor), co-precipitated nanoprecursors containing different amounts of La, Ni and Fe oxides were made. These samples were divided into two identical cloned libraries, which were heat-treated to bring about solid-state transformations at either 1348 K or 1573 K for 12 h. In each case, experimental conditions were designed to form the corresponding La4Ni3 − xFexO10 phases (x = 0.0–3.0) directly without comminution. Such materials are difficult to make without multiple heating and grinding steps. The heat-treated samples from each library were embedded into a wellplate and analysed by powder X-ray diffraction methods in order to elucidate trends in phase behaviour. Several hitherto unknown phase-pure Ruddlesden Popper type La4Ni3 − xFexO10 compositions were identified and their DC electrical conductivities measured

Algorithmic Pirogov-Sinai theory

We develop an efficient algorithmic approach for approximate counting and sampling in the low-temperature regime of a broad class of statistical physics models on finite subsets of the lattice $\mathbb Z^d$ and on the torus $(\mathbb Z/n \mathbb Z)^d$. Our approach is based on combining contour representations from Pirogov-Sinai theory with Barvinok's approach to approximate counting using truncated Taylor series. Some consequences of our main results include an FPTAS for approximating the partition function of the hard-core model at sufficiently high fugacity on subsets of $\mathbb Z^d$ with appropriate boundary conditions and an efficient sampling algorithm for the ferromagnetic Potts model on the discrete torus $(\mathbb Z/n \mathbb Z)^d$ at sufficiently low temperature

Carbohydrate-active enzymes exemplify entropic principles in metabolism

Statistical thermodynamics and in vitro experimentation demonstrate that metabolic enzymes can be driven by an increase in the entropy of a reaction system, and point to a role for entropy gradients in the emergence of robust metabolic functions in vivo

Traditional, virtual, and digital intermediaries in university-industry collaboration: exploring institutional logics and bounded rationality

This is the final version. Available on open access from Elsevier via the DOI in this recordUniversity-industry collaboration now extends beyond traditional intermediary structures and logics, enabled by more contemporary virtual networks and digital formats. This however poses new strategic and operational challenges for effective and responsive knowledge transfer. The purpose of this paper is to compare traditional models of knowledge transfer intermediaries in university-industry collaboration with emerging, virtual (network-based) and digital intermediaries by exploring their structures (thus institutional logics) and their services (their agency). We synthesise literature to form a comprehensive analytical framework to assess the structure and agency of twenty international knowledge transfer intermediaries from around the world. Further running a cluster analysis using multiple correspondence analysis method and following its results we propose a unique combination of institutional logic and bounded rationality lenses, which allowed us to identify four types of knowledge transfer intermediaries: rigid, rigid-unbounded, agent-bounded and agile. Our unique framework contributes to existing knowledge focused on traditional forms of knowledge transfer intermediaries, by identifying and positing institutional logics for emerging contemporary virtual and digital intermediaries in university-industry collaboration.Finnish Foundation for Economic Education (Liikesivistysrahasto)Scandinavian Consortium for Organizational Research (SCANCOR