9,474 research outputs found
Assessing schematic knowledge of introductory probability theory
[Abstract]: The ability to identify schematic knowledge is an important goal for both assessment
and instruction. In the current paper, schematic knowledge of statistical probability theory is
explored from the declarative-procedural framework using multiple methods of assessment.
A sample of 90 undergraduate introductory statistics students was required to classify 10
pairs of probability problems as similar or different; to identify whether 15 problems
contained sufficient, irrelevant, or missing information (text-edit); and to solve 10 additional
problems. The complexity of the schema on which the problems were based was also
manipulated. Detailed analyses compared text-editing and solution accuracy as a function of
text-editing category and schema complexity. Results showed that text-editing tends to be
easier than solution and differentially sensitive to schema complexity. While text-editing and
classification were correlated with solution, only text-editing problems with missing
information uniquely predicted success. In light of previous research these results suggest
that text-editing is suitable for supplementing the assessment of schematic knowledge in
development
Evidence for bimodal orbital separations of white dwarf-red dwarf binary stars
We present the results of a radial velocity survey of 20 white dwarf plus M
dwarf binaries selected as a follow up to a \textit{Hubble Space Telescope}
study that aimed to spatially resolve suspected binaries. Our candidates are
taken from the list of targets that were spatially unresolved with
\textit{Hubble}. We have determined the orbital periods for 16 of these compact
binary candidates. The period distribution ranges from 0.14 to 9.16\,d and
peaks near 0.6\,d. The original sample therefore contains two sets of binaries,
wide orbits (\,au) and close orbits (\,au), with
no systems found in the \,au range. This observational evidence
confirms the bimodal distribution predicted by population models and is also
similar to results obtained in previous studies. We find no binary periods in
the months to years range, supporting the post common envelope evolution
scenario. One of our targets, WD\,1504+546, was discovered to be an eclipsing
binary with a period of 0.93\,d
Escape path complexity and its context dependency in Pacific blue-eyes (Pseudomugil signifer)
The escape trajectories animals take following a predatory attack appear to
show high degrees of apparent 'randomness' - a property that has been described
as 'protean behaviour'. Here we present a method of quantifying the escape
trajectories of individual animals using a path complexity approach. When fish
(Pseudomugil signifer) were attacked either on their own or in groups, we find
that an individual's path rapidly increases in entropy (our measure of
complexity) following the attack. For individuals on their own, this entropy
remains elevated (indicating a more random path) for a sustained period (10
seconds) after the attack, whilst it falls more quickly for individuals in
groups. The entropy of the path is context dependent. When attacks towards
single fish come from greater distances, a fish's path shows less complexity
compared to attacks that come from short range. This context dependency effect
did not exist, however, when individuals were in groups. Nor did the path
complexity of individuals in groups depend on a fish's local density of
neighbours. We separate out the components of speed and direction changes to
determine which of these components contributes to the overall increase in path
complexity following an attack. We found that both speed and direction measures
contribute similarly to an individual's path's complexity in absolute terms.
Our work highlights the adaptive behavioural tactics that animals use to avoid
predators and also provides a novel method for quantifying the escape
trajectories of animals.Comment: 9 page
Nonlinear energy-loss straggling of protons and antiprotons in an electron gas
The electronic energy-loss straggling of protons and antiprotons moving at
arbitrary nonrelativistic velocities in a homogeneous electron gas are
evaluated within a quadratic response theory and the random-phase approximation
(RPA). These results show that at low and intermediate velocities quadratic
corrections reduce significantly the energy-loss straggling of antiprotons,
these corrections being, at low-velocities, more important than in the
evaluation of the stopping power.Comment: 4 pages, 3 figures, to appear in Phys. Rev.
Detection and mapping of hydrothermally altered rocks in the vicinity of the comstock lode, Virginia Range, Nevada, using enhanced LANDSAT images
The author has identified the following significant results. LANDSAT images enhanced by the band-ratioing method can be used for reconnaissance alteration mapping in moderately heavily vegetated semiarid terrain as well as in sparsely vegetated to semiarid terrain where the technique was originally developed. Significant vegetation cover in a scene, however, requires the use of MSS ratios 4/5, 4/6, and 6/7 rather than 4/5, 5/6, and 6/7, and requires careful interpretation of the results. Supplemental information suitable to vegetation identification and cover estimates, such as standard LANDSAT false-color composites and low altitude aerial photographs of selected areas is desirable
Developing the role of the sports dentist
Sports dentistry has traditionally focused on orofacial trauma. There is now increasing evidence that participation in sport, particularly at elite level, may significantly increase the risks to oral health. The negative impact of poor oral health on athlete-reported wellbeing and performance is clear. The risks to athlete oral health can and should be mitigated and the role of the sports dentist is evolving to meet these new challenges. Custom-made mouthguards provide protection against orofacial trauma and potentially, concussion. Oral health screening should be included in athlete pre-season preparation. As integrated members of the athlete support team, dentists and dental care professionals can provide sport-specific oral health advice, encouraging athletes to take ownership of their oral health. The potential for translational health and wellbeing benefits to the wider population is also substantial, particularly with youth groups and recreational athletes. Sports dentistry requires distinctive skills. A UK-wide network of dentists and other oral health professionals with an interest in sport is important, to ensure that both appropriate advice and treatment is evidence-based and to further develop the research and clinical foundations
Apparent Seasonal Cycle in Isotopic Discrimination of Carbon in the Atmosphere and Biosphere Due to Vapor Pressure Deficit
We explore seasonal variability in isotopic fractionation by analyzing observational data from the atmosphere and the biosphere, as well as simulated data from a global model. Using simulated values of atmospheric CO2 and its carbon isotopic composition, we evaluated different methods for specifying background concentrations when calculating the isotopic signature of source CO2 (δs) to the atmosphere. Based on this evaluation, we determined that free troposphere measurements should be used when available as a background reference when calculating δs from boundary layer observations. We then estimate the seasonal distribution of δs from monthly climatologies derived from several atmospheric sampling sites. This approach yields significant seasonal variations in δs with more enriched values during the summer months that exceed the uncertainty of δs estimated for any given month. Intra-annual measurements of δ13C in the cellulose of Pinus taeda growing in the southeastern U.S. also reveal seasonal isotopic variations that are consistent in phase but not necessarily amplitude with atmospherically derived estimates of δs. Coherent seasonal patterns in δs inferred from the atmosphere and observed in the biosphere were not consistent with the seasonal isotopic discrimination simulated by a commonly used biosphere model. However, δs seasonality consistent with observations from the atmosphere and biosphere was retrieved with a revised biosphere model when stomatal conductance, and thus isotopic discrimination, was allowed to vary in response to vapor pressure deficit rather than relative humidity. Therefore, in regions where vapor pressure deficit and relative humidity are positively covariant over the growth season, such as the sub-tropics, different stomatal conductance models may yield very different estimates of CO2 and H2O exchange between the biosphere and atmosphere
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