Stability of hexagonal solidification patterns

We investigate the dynamics of cellular solidification patterns using three-dimensional phase-field simulations. The cells can organize into stable hexagonal patterns or exhibit unsteady evolutions. We identify the relevant secondary instabilities of regular hexagonal arrays and find that the stability boundaries depend significantly on the strength of crystalline anisotropy. We also find multiplet states that can be reached by applying well-defined perturbations to a pre-existing hexagonal array.Comment: Minor changes, mainly in introduction and conclusion, one reference adde

Lanthanide(III) complexes of rhodamine-DO3A conjugates as agents for dual-modal imaging

Two novel dual-modal MRI/optical probes based on a rhodamine-DO3A conjugate have been prepared. The bis aqua-Gd(III) complex Gd.L1 and mono aqua-Gd(III) complex Gd.L2 behave as dual-modal imaging probes (r1 = 8.5 and 3.8 mM-1s-1 for Gd.L1 and Gd.L2 respectively; λex = 560 nm and λem = 580 nm for both complexes). The rhodamine fragment is pH sensitive and upon lowering of pH an increase in fluorescence intensity is observed as the spirolactam ring opens to give the highly fluorescent form of the molecule. The ligands are bimodal when coordinated to Tb(III) ions, inducing fluorescence from both the lanthanide center and the rhodamine fluorophore, on two independent time-frames. Confocal imaging experiments were carried out to establish the localization of Gd.L2 in HEK cells. Co-localisation with MitoTracker® Green confirmed that Gd.L2 compartmentalizes in the mitochondria. Gd.L2 was also evaluated as an MRI probe for imaging tumors in BALB/c nude mice bearing M21 xenografts. A 36.5% decrease in T1 within the tumor was observed 30 minutes post injection showing that Gd.L2 is preferentially up taken in the tumor. Gd.L2 is the first small molecule MR/fluorescent dual-modal imaging agent to display an off-on pH switch upon its preferential uptake within the more acidic micro-environment of tumor cells

Knowledge transfer and exchange: a look at the literature in relation to research and policy

Within the field of health policy, there have been widespread calls for the increased or improved use of evidence within policy making. This reflects an ambition to deliver better policy in terms of outcomes, resource efficiency and effectiveness, and a belief that this can be achieved through utilising the available evidence to inform and guide decision making. For those tasked with improving the uptake of a piece or body of evidence, for policy makers aiming to improve their evidence use, or for researches investigating this question, a number of conceptual questions remain on how to actually achieve this, such as: What should count as evidence for policy making? Who should govern (or steer) the use of research evidence for policy? What is ‘good evidence’ for decision making? What is the ‘good use’ of evidence from a governance perspective? How is research knowledge typically translated into policy? How can one ‘improve’ the use or uptake of evidence in policy making? The GRIP-Health Project is a 5 year, European Research Council supported programme of work that aims to improve the use of research evidence in health policy through undertaking research on the political aspects of health policy making and evidence use. The project has developed a number of working papers that engage with some of these topics.1 This current paper is concerned with the last two of the questions listed above, specifically reviewing key aspects of Knowledge Transfer and Exchange (KTE) related to getting research into policy and practice. While the health sector is increasingly motivated by a desire to get research evidence into policy, outside the field of health there is a much broader body of work that is specifically concerned with how evidence and knowledge are transferred, translated, or taken up by different policy actors. Various theories attempt to establish how KTE works, the contextual factors that influence the process, and how to achieve maximum impact for relevant bodies of evidence. Acronyms and terminology used in this field vary accordingly, and can include knowledge transfer, knowledge translation, knowledge management, and knowledge brokering. These various terms have been grouped together under the rubric ‘K*’ by some authors to reflect the multiple overlapping terms 2 Prior working papers in this series deal with aspects of: Stewardship of health evidence; hierarches and appropriateness of evidence; and institutional approaches to evidence uptake research. Working papers and other outputs of the programme are available at the GRIP-Health website http://www.lshtm.ac.uk/groups/griphealth/resources/index.html 3 (c.f. Shaxson et al., 2012). However, in this paper, we use the term KTE to refer to the general body of literature focused on issues of knowledge production, dissemination, uptake and use in policymaking. As the body of work on KTE is extensive, it was decided not to attempt a complete or systematic review of the literature. There are, however, several papers which attempt to synthesise the existing literature or systematically review elements of the KTE field. These reviews provide a starting point for mapping the field to help inform efforts to improve the use of research evidence in policy. The current paper therefore has two objectives. First, it summarises and synthesises a set of identified KTE review papers in order to undertake a comparison of their similarities and their differences on the main areas they cover, to provide a basic mapping of key KTE concepts. After this, it then explores some key themes that emerge from the KTE literature which are of particular relevance to the GRIP-Health programme and other researchers or stakeholders who are tasked with improving evidence uptake

Rfx6 Maintains the Functional Identity of Adult Pancreatic β Cells.

SummaryIncreasing evidence suggests that loss of β cell characteristics may cause insulin secretory deficiency in diabetes, but the underlying mechanisms remain unclear. Here, we show that Rfx6, whose mutation leads to neonatal diabetes in humans, is essential to maintain key features of functionally mature β cells in mice. Rfx6 loss in adult β cells leads to glucose intolerance, impaired β cell glucose sensing, and defective insulin secretion. This is associated with reduced expression of core components of the insulin secretion pathway, including glucokinase, the Abcc8/SUR1 subunit of KATP channels and voltage-gated Ca2+ channels, which are direct targets of Rfx6. Moreover, Rfx6 contributes to the silencing of the vast majority of “disallowed” genes, a group usually specifically repressed in adult β cells, and thus to the maintenance of β cell maturity. These findings raise the possibility that changes in Rfx6 expression or activity may contribute to β cell failure in humans

On narrowing coated conductor film: emergence of granularity-induced field hysteresis of transport critical current

Critical current density Jc in polycrystalline or granular superconducting material is known to be hysteretic with applied field H due to the focusing of field within the boundary between adjacent grains. This is of concern in the so-called coated conductors wherein superconducting film is grown on a granular, but textured surface of a metal substrate. While previous work has mainly been on Jc determined using induced or magnetization currents, the present work utilizes transport current via an applied potential in strip geometry. It is observed that the effect is not as pronounced using transport current, probably due to a large difference in criterion voltage between the two types of measurements. However, when the films are narrowed by patterning into 200-, 100-, or 80-micron, the hysteresis is clearly seen, because of the forcing of percolation across higher-angle grain boundaries. This effect is compared for films grown on ion-beam-assisted-deposited (IBAD) YSZ substrate and those grown on rolling-assisted-biaxially-textures substrates (RABiTS) which have grains that are about ten times larger. The hysteresis is more pronounced for the latter, which is more likely to have a weak grain boundary spanning the width of the microbridge. This is also of concern to applications in which coated conductors will be striated in order to reduce of AC losses.Comment: text-only: 10 pages, plus 5 figures on 5 page

Coloring Mixed and Directional Interval Graphs

A mixed graph has a set of vertices, a set of undirected egdes, and a set ofdirected arcs. A proper coloring of a mixed graph $G$ is a function $c$ thatassigns to each vertex in $G$ a positive integer such that, for each edge $uv$in $G$, $c(u) \ne c(v)$ and, for each arc $uv$ in $G$, $c(u) mixed graph$G$, the chromatic number$\chi(G)$is the smallest number ofcolors in any proper coloring of$G$. A directional interval graph is a mixedgraph whose vertices correspond to intervals on the real line. Such a graph hasan edge between every two intervals where one is contained in the other and anarc between every two overlapping intervals, directed towards the interval thatstarts and ends to the right. Coloring such graphs has applications in routing edges in layered orthogonalgraph drawing according to the Sugiyama framework; the colors correspond to thetracks for routing the edges. We show how to recognize directional intervalgraphs, and how to compute their chromatic number efficiently. On the otherhand, for mixed interval graphs, i.e., graphs where two intersecting intervalscan be connected by an edge or by an arc in either direction arbitrarily, weprove that computing the chromatic number is NP-hard.<br