1,599 research outputs found
The Saskatchewan integrated noxious weeds management program
Non-Peer ReviewedThe distribution of scentless chamomile was mapped for highways and municipal roads throughout the province. The weed grows on 867 miles of provincial highway and 2814 miles of municipal roads. In Saskatchewan, 98 rural municipalities do not have the weed. Scentless chamomile was reported in 199 rural municipalities. The weed should be controlled to prevent further spread throughout the province. The scentless chamomile seed weevil (Omphalapion hookeri) and gall midge (Rhopalomyia tripleurospermi) have successfully established in the province. Their populations are increasing
Diagnostics from polarization of scattered optical light from Galactic infrared cirrus
We propose polarization of scattered optical light from intermediate Galactic
latitude infrared cirrus as a new diagnostic to constrain models of
interstellar dust and the anisotropic interstellar radiation field (aISRF). For
single scattering by a sphere, with Mie scattering phase functions for
intensity and polarized intensity for a dust model at a given wavelength (Sloan
and bands), and with models of anisotropic illumination from the entire
sky (represented in HEALPix), we develop the formalism for calculating useful
summary parameters for an integrated flux nebula (IFN): average of the phase
function weighted by the illumination, polarization angle (), and
polarization fraction (). To demonstrate the diagnostic discrimination of
polarization from scattered light, we report on the effects of different
anisotropic illumination models and different dust models on the summary
parameters for the Spider IFN. The summary parameters are also sensitive to the
IFN location, as we illustrate using FRaNKIE illumination models. For assessing
the viability of dust and aISRF models, we find that observations of and
of scattered light are indeed powerful new diagnostics to complement joint
modeling of the intensity of scattered light (related to the average phase
function) and the intensity of thermal dust emission. However, optically thin
IFNs that can be modelled using single scattering are faint and is not
large, as it could be with Rayleigh scattering, and so these observations need
to be carried out with care and precision. Results for the Draco nebula
compared to the Spider illustrate the challenge.Comment: 14 pages, 8 figures; Accepted for publication in Ap
Learning About Development at A-Level
Young peopleās interest in development issues has been the focus of numerous
studies but there has been little research that looks at the impact of learning of
a specific educational course. This research paper looks at the impact of studying
A-level World Development on young people in England and Wales. It summarises
the outcomes of research by Bowes in 2011 and a further survey in 2012 with
students who have completed the course.
This study looks specifically at the relevance, effectiveness and impact of the
course on students. The evidence suggests that the A-level is popular and seen
as relevant to young peopleās lives and views about the world. Both teachers and
students state that the themes discussed are up-to-date and accessible to study.
In terms of effectiveness of the course overall, there is evidence of understanding
of the key issues in development, although the priorities given to particular themes
varied from school and college.
Programmes and projects on learning about development have often been
promoted because there is an assumption that mere engagement with these
themes has an impact on young peopleās learning in terms of changing their
behaviour and attitudes towards taking action to reduce global poverty. The
evidence from this research shows a complex picture of impact with the emphasis
appearing to be more on the social and moral aspects of development than the
political. The research indicates positive changes in perceptions of global poverty
and inequality in the world, but less so on the more social and political aspects.
There is evidence that studying the A-level has had an impact upon the studentsā
future learning in higher education with Geography and Development Studies
becoming more popular.
The first full World Development A-level began in 2008 so the examination is still
relatively new. The sample taken for this study and the research by Bowes covered
a relatively small number of students. However, what is clear from this research
is that an A-level of this type can play an important contribution in deepening a
young personās learning and understanding about development and that it is a
subject that is seen as popular and relevant to their lives
Letters and accounts from George Bowes to GF Story, 8 Sept 1829 and May 14 1838
Two letters with accounts sent to GF Story in Tasmania, from George Bowes, London, 8 September 1829 and 14 May 1838. The first letter is concerned with Story's house in Critchell Place, London, which was leased to Mrs Townsend at 45 pounds per annum. Accounts concerning the lease are included, while the second letter (1838) speculates as to the value of the house. From Cotton Family Papers C7/160, 16
Flight Envelope Assessment of SmallSat Aerocapture Trajectories at Venus and Mars
Aerocapture is an increasingly studied orbit insertion concept for small satellite (SmallSat) missions beyond low Earth orbit (LEO). Compared to fully propulsive methods, aerocapture reduces the orbit-insertion propellant mass by approaching on a hyperbolic path and using the planetary atmosphere to reduce the vehicleās velocity such that the final target orbit is achieved. This allows for an increase in payload mass delivered to orbit and a reduction in launch-to -orbit time. To analyze the feasibility at Venus and Mars, aerocapture flight envelope analysis is conducted by assessing the guidable trajectory space during atmospheric flight given entry conditions, vehicle properties, target parameters, and planet-dependent trajectory dispersions. The Program to Optimize Simulated Trajectories II (POST2) is used to simulate both ballistic and lifting aerocapture trajectories with SmallSat-compatible aeroshell designs. The entry flight path angle is optimized to achieve a final target orbit for lift up/down and max/min control configurations. When plotted, the resulting area between the steep and shallow trajectories forms a flight envelope with planet-dependent Ā±3Ļ atmospheric, aerodynamic, and delivery state dispersion profiles applied. The results presented in this paper show that SmallSat aerocapture is feasible for lifting aeroshell designs at Mars and Venus as well as ballistic vehicle designs at Mars
Small Satellite-Sized Hypersonic Inflatable Aerodynamic Decelerators for Interplanetary Science Missions
To make the most of ridesharing opportunities, small satellite (SmallSat) mission designers endeavor to pack as much payload into a SmallSat-class form factor as possible. The mass and volume constraints of this smaller vehicle class present a challenge for interplanetary mission sets that require a means of achieving orbit insertion at their destination of interest. For a fully propulsive orbit insertion design, this may translate to the propellant mass being a significant fraction of the overall vehicle mass and prolonged insertion time. Aerocapture is a single quick maneuver that can significantly reduce the required propellant mass for orbit insertion. Because aerocapture uses a planetās atmosphere to achieve the necessary change in velocity, a protective aeroshell is needed. The constraints imposed on secondary payloads render traditional rigid aeroshells mass and space prohibitive for the SmallSat class of vehicles; thus, warranting consideration of deployable designs that can be stowed compactly until needed for atmospheric entry. The Hypersonic Inflatable Aerodynamic Decelerator (HIAD) is a deployable aeroshell that leverages inflatable toroids to achieve the large drag area needed for aerodynamic deceleration. While the technology is currently being analyzed for Mars human-scale missions, it has the potential applicability for interplanetary SmallSat-scale missions as well.
This paper highlights a study conducted during an internship at NASA Langley Research Center to investigate the feasibility of using a scaled-down HIAD design in SmallSat aerocapture missions. Several scaling methodologies are investigated including use of parametric models and direct computer-aided design (CAD) model scaling. Candidate HIAD configurations that conform to secondary payload adapter requirements are identified. The Program to Optimize Simulated Trajectories II (POST2) is utilized to conduct orbit insertion performance and trajectory sensitivity studies using the candidate configurations at Earth, Venus, and Mars. The results of the study indicate that multiple SmallSat-sized HIAD designs, targeting a range of SmallSat payload classes, are feasible for planetary aerocapture missions to Mars and Venus as well as Earth-based aerocapture missions
Impact of Oxidation State on Reactivity and Selectivity Differences between Nickel(III) and Nickel(IV) Alkyl Complexes
Described is a systematic comparison of factors impacting the relative rates and selectivities of C(sp3)āC and C(sp3)āO bondāforming reactions at highāvalent Ni as a function of oxidation state. Two Ni complexes are compared: a cationic octahedral NiIV complex ligated by tris(pyrazolyl)borate and a cationic octahedral NiIII complex ligated by tris(pyrazolyl)methane. Key features of reactivity/selectivity are revealed: 1)ā
C(sp3)āC(sp2) bondāforming reductive elimination occurs from both centers, but the NiIII complex reacts up to 300āfold faster than the NiIV, depending on the reaction conditions. The relative reactivity is proposed to derive from ligand dissociation kinetics, which vary as a function of oxidation state and the presence/absence of visible light. 2)ā
Upon the addition of acetate (AcOā), the NiIV complex exclusively undergoes C(sp3)āOAc bond formation, while the NiIII analogue forms the C(sp3)āC(sp2) coupled product selectively. This difference is rationalized based on the electrophilicity of the respective MāC(sp3) bonds, and thus their relative reactivity towards outerāsphere SN2ātype bondāforming reactions.The high point: This report describes a systematic comparison of factors impacting the relative rates and selectivities of C(sp3)āC and C(sp3)āO bondāforming reactions at highāvalent Ni centers as a function of oxidation state (NiIII versus NiIV). Two Ni complexes are compared: a cationic octahedral NiIV complex ligated by tris(pyrazolyl)borate and a cationic octahedral NiIII complex ligated by tris(pyrazolyl)methane.Peer Reviewedhttps://deepblue.lib.umich.edu/bitstream/2027.42/150547/1/anie201903638.pdfhttps://deepblue.lib.umich.edu/bitstream/2027.42/150547/2/anie201903638-sup-0001-misc_information.pdfhttps://deepblue.lib.umich.edu/bitstream/2027.42/150547/3/anie201903638_am.pd
Intense summer floods may induce prolonged increases in benthic respiration rates of more than one year leading to low river dissolved oxygen
The supply of readily-degradable organic matter to river systems can cause stress to dissolved oxygen (DO) in slow-flowing waterbodies. To explore this threat, a multi-disciplinary study of the River Thames (UK) was undertaken over a six-year period (2009ā14). Using a combination of observations at various time resolutions (monthly to hourly), physics-based river network water quality modelling (QUESTOR) and an analytical tool to estimate metabolic regime (Delta method), a decrease in 10th percentile DO concentration (10-DO, indicative of summer low levels) was identified during the study period. The assessment tools suggested this decrease in 10-DO was due to an increase in benthic heterotrophic respiration. Hydrological and dissolved organic carbon (DOC) data showed that the shift in 10-DO could be attributed to summer flooding in 2012 and consequent connection of pathways flushing degradable organic matter into the river. Comparing 2009ā10 and 2013ā14 periods, 10-DO decreased by 7.0% at the basin outlet (Windsor) whilst median DOC concentrations in a survey of upstream waterbodies increased by 5.5ā48.1%. In this context, an anomalous opposing trend in 10-DO at one site on the river was also identified and discussed. Currently, a lack of process understanding of spatio-temporal variability in benthic respiration rates is hampering model predictions of river DO. The results presented here show how climatic-driven variation and urbanisation induce persistent medium-term changes in the vulnerability of water quality to multiple stressors across complex catchment systems
- ā¦