Superoxide and superoxide dismutase in red blood cells

In 1969 a previously obscure copper protein of red blood cells, erythrocuprein, was shown to catalyse the dismutation of superoxide radicals. Erythrocuprein thus became superoxide dismutase and the object of intensive study. Superoxide dismutase is typically an enzyme of aerobic organisms which utilize oxygen as the major electron acceptor. The presence of superoxide dismutase in microorganisms has been found to parallel their tolerance for oxygen. We recently described the isolation and properties of two forms of superoxide dismutase from human erythrocytes, SOD I and SOD II (Bannister et al., 1976). These can be obtained from a haemolysate of red blood cells after precipitation of the hemoglobin with a mixture of ethanol and chloroform.peer-reviewe

Problems related to the integration of fault tolerant aircraft electronic systems

Problems related to the design of the hardware for an integrated aircraft electronic system are considered. Taxonomies of concurrent systems are reviewed and a new taxonomy is proposed. An informal methodology intended to identify feasible regions of the taxonomic design space is described. Specific tools are recommended for use in the methodology. Based on the methodology, a preliminary strawman integrated fault tolerant aircraft electronic system is proposed. Next, problems related to the programming and control of inegrated aircraft electronic systems are discussed. Issues of system resource management, including the scheduling and allocation of real time periodic tasks in a multiprocessor environment, are treated in detail. The role of software design in integrated fault tolerant aircraft electronic systems is discussed. Conclusions and recommendations for further work are included

Children’s Digital Play during the COVID-19 Pandemic: insights from the Play Observatory

The COVID-19 pandemic has had an enormous impact on many aspects of children’s day-to-day lives, including their play. Measures such as lockdowns, school and playground closures, quarantine, isolation and social distancing introduced to curb transmission have resulted in major consequences for where, when, how and with whom children can play. This article reports on interim findings from ‘The Play Observatory’, a 15-month project researching children’s play experiences during the COVID-19 pandemic. Collecting data through an online survey and online case studies, the research offers insights into ways in which children’s play has endured, adapted and responded to restrictions brought about by the pandemic. This article focuses on children’s digital play throughout this period, including examples of digital gaming, online play, social media, playful creation of digital media texts and hybrid online-offline play. Drawing on theories relating to dynamic literacies, multimodal perspectives and the Reggio Emilia concept of the ‘hundred languages’, this article examines the role of the digital in children’s contemporary play practices and the specific affordances of digital play during times of stress, uncertainty and physical distancing. The findings highlight ways in which digital play continued, adapted, evolved and reflected children’s experiences and understandings of the pandemic. The study reveals the complexity of digital play and its place within contemporary digital childhoods, troubling simplistic notions of ‘screen time’ and highlighting the increasingly blurred boundaries around digital and non-digital practices, calling for educational approaches that value digital play as significant meaning-making

Beyond Outerplanarity

We study straight-line drawings of graphs where the vertices are placed in convex position in the plane, i.e., convex drawings. We consider two families of graph classes with nice convex drawings: outer $k$-planar graphs, where each edge is crossed by at most $k$ other edges; and, outer $k$-quasi-planar graphs where no $k$ edges can mutually cross. We show that the outer $k$-planar graphs are $(\lfloor\sqrt{4k+1}\rfloor+1)$-degenerate, and consequently that every outer $k$-planar graph can be $(\lfloor\sqrt{4k+1}\rfloor+2)$-colored, and this bound is tight. We further show that every outer $k$-planar graph has a balanced separator of size $O(k)$. This implies that every outer $k$-planar graph has treewidth $O(k)$. For fixed $k$, these small balanced separators allow us to obtain a simple quasi-polynomial time algorithm to test whether a given graph is outer $k$-planar, i.e., none of these recognition problems are NP-complete unless ETH fails. For the outer $k$-quasi-planar graphs we prove that, unlike other beyond-planar graph classes, every edge-maximal $n$-vertex outer $k$-quasi planar graph has the same number of edges, namely $2(k-1)n - \binom{2k-1}{2}$. We also construct planar 3-trees that are not outer $3$-quasi-planar. Finally, we restrict outer $k$-planar and outer $k$-quasi-planar drawings to \emph{closed} drawings, where the vertex sequence on the boundary is a cycle in the graph. For each $k$, we express closed outer $k$-planarity and \emph{closed outer $k$-quasi-planarity} in extended monadic second-order logic. Thus, closed outer $k$-planarity is linear-time testable by Courcelle's Theorem.Comment: Appears in the Proceedings of the 25th International Symposium on Graph Drawing and Network Visualization (GD 2017

Optical study of PKS B1322-110, the intra-hour variable radio source

Observations with the Australia Telescope Compact Array revealed intra-hour variations in the radio source PKS B1322-110 (Bignall et al. 2019). As part of an optical follow-up, we obtained Gemini Halpha and Halpha continuum (HalphaC) images of the PKS B1322-110 field. A robust 19-sigma detection of PKS B1322-110 in the Halpha-HalphaC image prompted us to obtain the first optical spectrum of PKS B1322-110. With the Gemini spectrum we determine that PKS B1322-110 is a flat-spectrum radio quasar at a redshift of z=3.007 +/- 0.002. The apparent flux detected in the Halpha filter is likely to originate from HeII emission redshifted precisely on the Galactic Halpha narrow-band filter. We set upper limits on the emission measure of the Galactic plasma, for various possible cloud geometries

Optical study of PKS B1322-110, the intra-hour variable radio source

Observations with the Australia Telescope Compact Array revealed intra-hour variations in the radio source PKS B1322-110 (Bignall et al. 2019). As part of an optical follow-up, we obtained Gemini Hα and Hα continuum (HαC) images of the PKS B1322-110 field. A robust 19 σ detection of PKS B1322- 110 in the Hα−HαC image prompted us to obtain the first optical spectrum of PKS B1322-110. With the Gemini spectrum we determine that PKS B1322-110 is a flat-spectrum radio quasar at a redshift of z = 3.007 ± 0.002. The apparent flux detected in the Hα filter is likely to originate from He ii emission redshifted precisely on the Galactic Hα narrow-band filter. We set upper limits on the emission measure of the Galactic plasma, for various possible cloud geometries