An experimental investigation of the hypergolic ignition of some polymeric fuels with oxygen

Hypergolic ignition of polymeric fuels with oxyge

Markov chain estimation of avian seasonal fecundity

Avian seasonal fecundity is of interest from evolutionary, ecological, and conservation perspectives. However, direct estimation of seasonal fecundity is difficult, especially with multi-brooded birds, and models representing the renesting and quitting processes are usually required. To explore the consequences of modeling decisions on inference about avian seasonal fecundity, we generalize previous Markov chain (MC) models of avian nest success to formulate two different MC models of avian seasonal fecundity that represent two different ways to model renesting decisions and breeding cessation. We parameterize both Markov chains (regular and absorbing) for two species (Eastern Meadowlark, Sturnella magna, and Dickcissel, Spiza americana) and compare the results using mean-square error of the estimated number of successful broods per breeding female. We also provide formulae for estimating the expected variation in female breeding success. The absorbing MC performed better for both species, although the regular MC performed almost as well when the duration of the breeding season was estimated by taking the 95th percentile of a negative binomial distribution fit to the observed durations among all females. In their simplest form the models contain very few parameters (four or five) and should also prove useful as a foundation for more complex models of avian seasonal fecundity and demography

Supporting practitioner-led inquiry into classroom dialogue with a research-informed professional learning resource: A design-based approach

Funder: Economic and Social Research Council; Id: http://dx.doi.org/10.13039/501100000269Research indicating the educational value of classroom dialogue, in which participants engage critically and constructively with other perspectives, is long established but classroom practice evolves slowly. Outcomes of practitioner professional development in this area are inconsistent and often dependent on costly, external input. Our study aimed to understand whether and how practitioner‐led inquiry may offer an alternative, sustainable and scalable way of developing dialogic practices, characterising effective organisational models. The Teacher Scheme for Educational Dialogue Analysis (T‐SEDA) resource pack was designed to support iterative cycles of practitioner inquiry based on systematic analysis of classroom dialogue and reflecting critically with peers, using customisable coding tools and templates. This open resource embeds research findings about dialogue forms that are productive for student learning. We report our design‐based research comprising nested inquiry cycles involving 74 practitioners from early years to tertiary levels. Data were derived from surveys, inquiry reports and interviews. Participants successfully used and adapted the resources for their own goals, needs and diverse contexts across seven countries. The largely autonomous process was typically supported by local facilitators working with groups of practitioners; data analysis focused on illuminating models of institutional organisation of inquiry, uses of T‐SEDA resources, participant perceptions and factors underlying (dis)engagement. The findings offer insights into knowledge mobilisation and educational change processes. They yield design principles for scalability and sustainability based on a non‐prescriptive model of local ownership and facilitation of self‐directed practitioner inquiry and purpose‐driven adaptation in complex educational circumstances

Developing a coding scheme for analysing classroom dialogue across d educational contexts.

The research reported sought to develop a framework for systematically analysing classroom dialogue for application across a range of educational settings. The paper outlines the development and refinement of a coding scheme that attempts to represent and operationalise commonalities amongst some key theorists in the field concerning productive forms of educational dialogue. The team has tested it using video recordings from classroom settings in the UK and Mexico, across age phases, subject areas, and different interactional contexts including whole class, group and paired work. Our Scheme for Educational Dialogue Analysis (SEDA) is situated within a sociocultural paradigm, and draws on Hymes' Ethnography of Communication to highlight the importance of context. We examined how such a tool could be used in practice. We found that concentrating on the ‘communicative act’ to explore dialogue between participants was an appropriate level of granularity, while clustering the 33 resulting codes according to function of the acts helped to highlight dialogic sequences within lessons. We report on the application of the scheme in two different learning contexts and reflect on its fitness for purpose, including perceived limitations. Development of specialised sub-schemes and a version for teachers is underway.This collaborative work was carried out for a project entitled “A Tool for Analysing Dialogic Interactions in Classrooms” (http://tinyurl.com/BAdialogue) funded through the British Academy International Partnership and Mobility Scheme (ref. RG66509), between January 2013 - December 2015. We are most grateful to colleagues on the project teams who made significant contributions and helpful input during development and testing of the scheme and preparation of the manuscript, including Farah Ahmed, Riikka Hofmann, Christine Howe, Ruth Kershner, Fiona Jackson, Karen Littleton, Neil Mercer, Paul Warwick (UK team); Mariana Alarcón, Nube Estrada, Erika Gil, Kissy Guzmán, Flora Hernández, José Hernández, Haydeé Pedraza, Ana Luisa Rubio, Brenda Itzel Sánchez, Ana Laura Trigo, Maricela Velez (Mexico team). We also thank all of the teachers (especially Lloyd and Tania) and students who participated in our previous research from which examples were taken. We appreciate the support of the Economic and Social Research Council, sponsor of most of the UK team’s work in this area over the years

Translation and manipulation of silicon nanomembranes using holographic optical tweezers

We demonstrate the use of holographic optical tweezers for trapping and manipulating silicon nanomembranes. These macroscopic free-standing sheets of single-crystalline silicon are attractive for use in next-generation flexible electronics. We achieve three-dimensional control by attaching a functionalized silica bead to the silicon surface, enabling non-contact trapping and manipulation of planar structures with high aspect ratios (high lateral size to thickness). Using as few as one trap and trapping powers as low as several hundred milliwatts, silicon nanomembranes can be rotated and translated in a solution over large distances

Generalized Interpolation Material Point Approach to High Melting Explosive with Cavities Under Shock

Criterion for contacting is critically important for the Generalized Interpolation Material Point(GIMP) method. We present an improved criterion by adding a switching function. With the method dynamical response of high melting explosive(HMX) with cavities under shock is investigated. The physical model used in the present work is an elastic-to-plastic and thermal-dynamical model with Mie-Gr\"uneissen equation of state. We mainly concern the influence of various parameters, including the impacting velocity $v$, cavity size $R$, etc, to the dynamical and thermodynamical behaviors of the material. For the colliding of two bodies with a cavity in each, a secondary impacting is observed. Correspondingly, the separation distance $D$ of the two bodies has a maximum value $D_{\max}$ in between the initial and second impacts. When the initial impacting velocity $v$ is not large enough, the cavity collapses in a nearly symmetric fashion, the maximum separation distance $D_{\max}$ increases with $v$. When the initial shock wave is strong enough to collapse the cavity asymmetrically along the shock direction, the variation of $D_{\max}$ with $v$ does not show monotonic behavior. Our numerical results show clear indication that the existence of cavities in explosive helps the creation of ``hot spots''.Comment: Figs.2,4,7,11 in JPG format; Accepted for publication in J. Phys. D: Applied Physic

Horticultural Availability and Homeowner Preferences Drive Plant Diversity and Composition in Urban Yards

Understanding the factors that influence biodiversity in urban areas is important for informing management efforts aimed at enhancing the ecosystem services in urban settings and curbing the spread of invasive introduced species. We determined the ecological and socioeconomic factors that influence patterns of plant richness, phylogenetic diversity, and composition in 133 private household yards in the Minneapolis‐Saint Paul Metropolitan area, Minnesota, USA. We compared the composition of spontaneously occurring plant species and those planted by homeowners with composition in natural areas (at the Cedar Creek Ecosystem Science Reserve) and in the horticulture pool of species available from commercial growers. Yard area and fertilizer frequency influenced species richness of the spontaneous species but expressed homeowner values did not. In contrast, the criteria that homeowners articulated as important in their management decisions, including aesthetics, wildlife, neatness and food provision, significantly predicted cultivated species richness. Strikingly, the composition of plant species that people cultivated in their yards resembled the taxonomic and phylogenetic composition of species available commercially. In contrast, the taxonomic and phylogenetic composition of spontaneous species showed high similarity to natural areas. The large fraction of introduced species that homeowners planted was a likely consequence of what was available for them to purchase. The study links the composition and diversity of yard flora to their natural and anthropogenic sources and sheds light on the human factors and values that influence the plant diversity in residential areas of a major urban system. Enhanced understanding of the influences of the sources of plants, both native and introduced, that enter urban systems and the human factors and values that influence their diversity is critical to identifying the levers to manage urban biodiversity and ecosystem services

Three serendipitous pathways in E. coli can bypass a block in pyridoxal-5′-phosphate synthesis

Overexpression of seven different genes restores growth of a ΔpdxB strain of E. coli, which cannot make pyridoxal phosphate (PLP), on M9/glucose.None of the enzymes encoded by these genes has a promiscuous 4-phosphoerythronate dehydrogenase activity that can replace the activity of PdxB.Overexpression of these genes restores PLP synthesis by three different serendipitous pathways that feed into the normal PLP synthesis pathway downstream of the blocked step.Reactions in one of these pathways are catalyzed by low-level activities of enzymes of unknown function and a promiscuous activity of an enzyme that normally has a role in another pathway; one reaction appears to be non-enzymatic

The Non-Uniform Distribution of Galaxies from Data of the SDSS DR7 Survey

We have analyzed the spatial distribution of galaxies from the release of the Sloan Digital Sky Survey of galactic redshifts (SDSS DR7), applying the complete correlation function (conditional density), two-point conditional density (cylinder), and radial density methods. Our analysis demonstrates that the conditional density has a power-law form for scales lengths 0.5-30 Mpc/h, with the power-law corresponding to the fractal dimension D = 2.2+-0.2; for scale lengths in excess of 30 Mpc/h, it enters an essentially flat regime, as is expected for a uniform distribution of galaxies. However, in the analysis applying the cylinder method, the power-law character with D = 2.0+-0.3 persists to scale lengths of 70 Mpc/h. The radial density method reveals inhomogeneities in the spatial distribution of galaxies on scales of 200 Mpc/h with a density contrast of two, confirming that translation invariance is violated in the distribution of galaxies to 300 Mpc/h, with the sampling depth of the SDSS galaxies being 600 Mpc/h.Comment: 22 page

Cross-site comparison of ribosomal depletion kits for Illumina RNAseq library construction

Background Ribosomal RNA (rRNA) comprises at least 90% of total RNA extracted from mammalian tissue or cell line samples. Informative transcriptional profiling using massively parallel sequencing technologies requires either enrichment of mature poly-adenylated transcripts or targeted depletion of the rRNA fraction. The latter method is of particular interest because it is compatible with degraded samples such as those extracted from FFPE and also captures transcripts that are not poly-adenylated such as some non-coding RNAs. Here we provide a cross-site study that evaluates the performance of ribosomal RNA removal kits from Illumina, Takara/Clontech, Kapa Biosystems, Lexogen, New England Biolabs and Qiagen on intact and degraded RNA samples. Results We find that all of the kits are capable of performing significant ribosomal depletion, though there are differences in their ease of use. All kits were able to remove ribosomal RNA to below 20% with intact RNA and identify ~ 14,000 protein coding genes from the Universal Human Reference RNA sample at >1FPKM. Analysis of differentially detected genes between kits suggests that transcript length may be a key factor in library production efficiency. Conclusions These results provide a roadmap for labs on the strengths of each of these methods and how best to utilize them. Keywords: RNAseqr; RNA depletion; Illumina; NGS; ABRF; TranscriptomicsNational Cancer Institute (U.S.) (Grant P30-CA14051)National Institute of Environmental Health Sciences (Grant P30-ES002109