Conley: Computing connection matrices in Maple

In this work we announce the Maple package conley to compute connection and C-connection matrices. conley is based on our abstract homological algebra package homalg. We emphasize that the notion of braids is irrelevant for the definition and for the computation of such matrices. We introduce the notion of triangles that suffices to state the definition of (C)-connection matrices. The notion of octahedra, which is equivalent to that of braids is also introduced.Comment: conley is based on the package homalg: math.AC/0701146, corrected the false "counter example

Differences in silica content between marine and freshwater diatoms

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/109821/1/lno19893410205.pd

Effectual Urban Governance: The Effectuation of Cities for Systems Change Under Uncertainty

Three key drivers create the imperative for a new approach to urban governance. Firstly, scientists around the world agree that global ecological systems are at risk of collapse if current development trajectories continue. Secondly, decision-makers are facing a heightened level of uncertainty, due to factors including climate risk, ecosystem changes and geopolitical tensions – and since 2020, the COVID-19 global pandemic. And thirdly, given these complexities, current models of forecasting and prediction for strategic decision-making are increasingly constrained and unreliable, particularly for informing urban infrastructure governance decisions with multi-decade legacies. While urban infrastructure decision-makers find uncertainty challenging, for entrepreneurs uncertainty is the basis for opportunity. Entrepreneurs are agents of systems change, especially under conditions of heightened uncertainty. As a result, this thesis turns to the entrepreneurship domain to inform a new approach to urban governance, specifically the entrepreneurial decision-making logic of ‘effectuation’ developed by Saras Sarasvathy through her study of expert entrepreneurs’ approaches to new venture creation. Effectual urban governance includes establishing design principles, beginning with available means, establishing partnerships, and taking effectual action to iteratively increasing the structuration of innovations. In Part 1 - the thesis develops this model by reviewing and synthesizing the literature on sustainability transitions, urban governance, and entrepreneurship, with a historical analysis illustrating the role of entrepreneurship in industrial systems change. Building on a novel taxonomy of urban governance along the axes of uncertainty and systems change, the dynamic model of effectual urban governance combines entrepreneurship theory with sustainability transitions theory and is demonstrated through an illustrative civil infrastructure case study of the Willunga Basin Water Company informed by semi-structured research interviews. Part 2 of the thesis justifies the applicability of this model through focus on four key elements of effectual urban governance with application to urban transport, elaborating the theoretical rationale for each element and providing insights from effectuation literature and supporting complementary academic theories and research conducted during this thesis. In doing so, the thesis makes theoretical and practical contributions to urban governance and the development of civil infrastructure in the 21st century. At a time of heightened uncertainty, when global industrial and economic transformation to avert ecological collapse is imperative, this thesis begins a new conversation by demonstrating how adopting an entrepreneurial approach to civil infrastructure development can help government and civil actors proactively address the world’s shared and complex challenges. Effectual urban governance is this approach.Thesis (Ph.D.) -- University of Adelaide, School of Architecture and Civil Engineering, 202

Vesivirus 2117 capsids more closely resemble sapovirus and lagovirus particles than other known vesivirus structures

Vesivirus 2117 is an adventitious agent that in 2009, was identified as a contaminant of CHO cells propagated in bioreactors at a pharmaceutical manufacturing plant belonging to Genzyme. The consequent interruption in supply of Fabrazyme and Cerezyme (drugs used to treat Fabry and Gaucher disease respectively), caused significant economic losses. Vesivirus 2117 is a member of the Caliciviridae; a family of small icosahedral viruses encoding a positive sense RNA genome. We have used cryo-electron microscopy and three dimensional image reconstruction to calculate a structure of vesivirus 2117 virus like particles as well as feline calicivirus and a chimeric sapovirus. We present a structural comparison of several members of the Caliciviridae, showing that the distal P domain of vesivirus 2117 is morphologically distinct from that seen in other known vesivirus structures. Furthermore, at intermediate resolutions we found a high level of structural similarity between vesivirus 2117 and Caliciviridae from other genera, such as sapovirus and rabbit haemorrhagic disease virus. Phylogenetic analysis confirms vesivirus 2117 as a vesivirus closely related to canine vesiviruses. We postulate that morphological differences in virion structure seen between vesivirus clades may reflect differences in receptor usage

Measuring Ejecta Velocity Improves Type Ia Supernova Distances

We use a sample of 121 spectroscopically normal Type Ia supernovae (SNe Ia) to show that their intrinsic color is correlated with their ejecta velocity, as measured from the blueshift of the Si II 6355 feature near maximum brightness, v_Si. The SN Ia sample was originally used by Wang et al. (2009) to show that the relationship between color excess and peak magnitude, which in the absence of intrinsic color differences describes a reddening law, was different for two subsamples split by v_Si (defined as "Normal" and "High-Velocity"). We verify this result, but find that the two subsamples have the same reddening law when extremely reddened events (E(B-V) > 0.35 mag) are excluded. We also show that (1) the High-Velocity subsample is offset by ~0.06 mag to the red from the Normal subsample in the (B_max - V_max) - M_V plane, (2) the B_max - V_max cumulative distribution functions of the two subsamples have nearly identical shapes, but the High-Velocity subsample is offset by ~0.07 mag to the red in B_max - V_max, and (3) the bluest High-Velocity SNe Ia are ~0.10 mag redder than the bluest Normal SNe Ia. Together, this evidence indicates a difference in intrinsic color for the subsamples. Accounting for this intrinsic color difference reduces the scatter in Hubble residuals from 0.190 mag to 0.130 mag for SNe Ia with A_V < 0.7 mag. The scatter can be further reduced to 0.109 mag by exclusively using SNe Ia from the Normal subsample. Additionally, this result can at least partially explain the anomalously low values of R_V found in large SN Ia samples. We explain the correlation between ejecta velocity and color as increased line blanketing in the High-Velocity SNe Ia, causing them to become redder. We discuss some implications of this result, and stress the importance of spectroscopy for future SN Ia cosmology surveys, with particular focus on the design of WFIRST.Comment: 9 pages, 8 figures, submitted to Ap