Structure and function of negative feedback loops at the interface of genetic and metabolic networks

The molecular network in an organism consists of transcription/translation regulation, protein-protein interactions/modifications and a metabolic network, together forming a system that allows the cell to respond sensibly to the multiple signal molecules that exist in its environment. A key part of this overall system of molecular regulation is therefore the interface between the genetic and the metabolic network. A motif that occurs very often at this interface is a negative feedback loop used to regulate the level of the signal molecules. In this work we use mathematical models to investigate the steady state and dynamical behaviour of different negative feedback loops. We show, in particular, that feedback loops where the signal molecule does not cause the dissociation of the transcription factor from the DNA respond faster than loops where the molecule acts by sequestering transcription factors off the DNA. We use three examples, the bet, mer and lac systems in E. coli, to illustrate the behaviour of such feedback loops.Comment: 8 pages, 4 figure

Constant mean curvature solutions of the Einstein-scalar field constraint equations on asymptotically hyperbolic manifolds

We follow the approach employed by Y. Choquet-Bruhat, J. Isenberg and D. Pollack in the case of closed manifolds and establish existence and non-existence results for the Einstein-scalar field constraint equations on asymptotically hyperbolic manifolds.Comment: 15 page

Penrose type inequalities for asymptotically hyperbolic graphs

In this paper we study asymptotically hyperbolic manifolds given as graphs of asymptotically constant functions over hyperbolic space \bH^n. The graphs are considered as subsets of \bH^{n+1} and carry the induced metric. For such manifolds the scalar curvature appears in the divergence of a 1-form involving the integrand for the asymptotically hyperbolic mass. Integrating this divergence we estimate the mass by an integral over an inner boundary. In case the inner boundary satisfies a convexity condition this can in turn be estimated in terms of the area of the inner boundary. The resulting estimates are similar to the conjectured Penrose inequality for asymptotically hyperbolic manifolds. The work presented here is inspired by Lam's article concerning the asymptotically Euclidean case.Comment: 29 pages, no figure, includes a proof of the equality cas

The Helsinki Convention's agricultural nutrient governance: how domestic institutions matter

National policy styles and path-dependencies are affecting the abilities of Baltic Sea countries to deliver on their commitments under the Helsinki Convention. This article synthesizes evidence and insights from studies relating to the provisions on agricultural nutrient management, a main source of marine pollution. We contend that governments that are strongly concentrated vertically, while fragmented horizontally, lack capacity including with respect to informal institutions that can leverage implementation. As a stocktaking of institutional impediments to sustainable development, our analysis has wider relevance for other international agreements with Baltic Sea countries involved

Roll-to-Roll Dyed Conducting Silk Yarns: A Versatile Material for E-Textile Devices

KGaA, Weinheim Textiles are a promising base material for flexible and wearable electronic applications such as sensors, actuators, and energy harvesters. An essential component in such electronic textiles (e-textiles) is electrically conducting yarns. Here, a continuous dyeing process is presented to convert an off-the-shelf silk sewing thread into a wash and wear resistant functional thread with a conductivity of about 70 S cm−1; a record high value for coated yarns. An aqueous ink based on the conducting polymer:polyelectrolyte complex poly(3,4-ethylenedioxythiophene):polystyrene sulfonate (PEDOT:PSS) is modified, to produce more than 100 m of dyed conducting threads, which are subsequently converted into e-textiles by both hand weaving and machine embroidery. The yarns are resistant to abrasion and wear, and can be machine washed at least 15 times with retained electronic properties. The woven fabric is used to design a capacitive touch sensor which functions as an e-textile keyboard

Implementing intermittent current interruption into Li-ion cell modelling for improved battery diagnostics

A novel electroanalytical method, the intermittent current interruption (ICI) technique, has recently been promoted as a versatile tool for battery analysis and diagnostics. The technique enables frequent and continuous measurement of battery resistance, which then undergoes statistical analysis. Here, this method is implemented for commercial Li-ion cylindrical cells, and combined with a physics-based finite element model (FEM) of the battery to better interpret the measured resistances. Ageing phenomena such as solid electrolyte interphase (SEI) formation and metallic Li plating on the surface of the negative graphite particles are considered in the model. After validation, a long-term cycling simulation is conducted to mimic the ageing scenario of commercial cylindrical 21700 cells. The large number of internal resistance measurements obtained are subsequently visualized by creating a ‘resistance map’ as a function of both capacity and cycle numbers, providing a straight-forward image of their continuous evolution. By correlating the observed ageing scenarios with specific physical processes, the origins of ageing are investigated. The result shows that a decrease of the electrolyte volume fraction contributes significantly to the increase of internal resistance and affect the electrolyte diffusivity properties. Additionally, effects of porosity and particle radius of the different electrodes are investigated, providing valuable suggestions for battery design

The impact of interfaces in laminated packaging on transport of carboxylic acids

The permeability of oleic and acetic acid through low density polyethylene (LDPE) and ethylene acrylic acid (EAA) have been measured using diffusion cells. In addition, the permeability through combinations of LDPE and EAA in the form of laminates with different numbers of layers has been determined. Oleic acid shows an almost 30 times higher permeability compared to acetic acid, which was partly explained by the adsorption of oleic acid to the film surface during the permeability experiment. In addition, the permeability is lower for both oleic and acetic acid in the laminates compared to the pure films. The decreased permeability can be explained by the presence of crystalline domains close to the interface. This is supported by SAXS data which suggests an ordering of polymer chains in the EAA film close to the interface. In summary, the results show that it is possible to create barrier materials with decreased permeability, which is interesting for example in the packaging industry. (C) 2016 Elsevier B.V. All rights reserved

Genomic relatedness and diversity of Swedish native cattle breeds

International audienceAbstractBackgroundNative cattle breeds are important genetic resources given their adaptation to the local environment in which they are bred. However, the widespread use of commercial cattle breeds has resulted in a marked reduction in population size of several native cattle breeds worldwide. Therefore, conservation management of native cattle breeds requires urgent attention to avoid their extinction. To this end, we genotyped nine Swedish native cattle breeds with genome-wide 150 K single nucleotide polymorphisms (SNPs) to investigate the level of genetic diversity and relatedness between these breeds.ResultsWe used various SNP-based approaches on this dataset to connect the demographic history with the genetic diversity and population structure of these Swedish cattle breeds. Our results suggest that the Väne and Ringamåla breeds originating from southern Sweden have experienced population isolation and have a low genetic diversity, whereas the Fjäll breed has a large founder population and a relatively high genetic diversity. Based on the shared ancestry and the constructed phylogenetic trees, we identified two major clusters in Swedish native cattle. In the first cluster, which includes Swedish mountain cattle breeds, there was little differentiation among the Fjäll, Fjällnära, Swedish Polled, and Bohus Polled breeds. The second cluster consists of breeds from southern Sweden: Väne, Ringamåla and Swedish Red. Interestingly, we also identified sub-structuring in the Fjällnära breed, which indicates different breeding practices on the farms that maintain this breed.ConclusionsThis study represents the first comprehensive genome-wide analysis of the genetic relatedness and diversity in Swedish native cattle breeds. Our results show that different demographic patterns such as genetic isolation and cross-breeding have shaped the genomic diversity of Swedish native cattle breeds and that the Swedish mountain breeds have retained their authentic distinct gene pool without significant contribution from any of the other European cattle breeds that were included in this study

Measuring the neutron star equation of state using X-ray timing

One of the primary science goals of the next generation of hard X-ray timing instruments is to determine the equation of state of the matter at supranuclear densities inside neutron stars, by measuring the radius of neutron stars with different masses to accuracies of a few percent. Three main techniques can be used to achieve this goal. The first involves waveform modelling. The flux we observe from a hotspot on the neutron star surface offset from the rotational pole will be modulated by the star's rotation, giving rise to a pulsation. Information about mass and radius is encoded into the pulse profile via relativistic effects, and tight constraints on mass and radius can be obtained. The second technique involves characterising the spin distribution of accreting neutron stars. The most rapidly rotating stars provide a very clean constraint, since the mass-shedding limit is a function of mass and radius. However the overall spin distribution also provides a guide to the torque mechanisms in operation and the moment of inertia, both of which can depend sensitively on dense matter physics. The third technique is to search for quasi-periodic oscillations in X-ray flux associated with global seismic vibrations of magnetars (the most highly magnetized neutron stars), triggered by magnetic explosions. The vibrational frequencies depend on stellar parameters including the dense matter equation of state. We illustrate how these complementary X-ray timing techniques can be used to constrain the dense matter equation of state, and discuss the results that might be expected from a 10m$^2$ instrument. We also discuss how the results from such a facility would compare to other astronomical investigations of neutron star properties. [Modified for arXiv]Comment: To appear in Reviews of Modern Physics as a Colloquium, 23 pages, 9 figure