Video evidence : what gestures tell us about students' understanding of rate of change

This paper reports on insights into students’ understanding of the concept of rate of change, provided by examining the gestures made, by 25 Year 10 students, in videorecorded interviews. Detailed analysis, of both the sound and images, illuminates the meaning of rate-related gestures. Findings indicate that students often use the symbols and metaphors of gesture to complement, supplement, or even contradict verbal descriptions. Many students demonstrated, by the combination of their words and gestures, a sound qualitative understanding of constant rate, with a few attempting to quantify rate. The interpretation of gestures may provide teachers with a better understanding of the progress in their students’ thinking.

An 'emergent model' for rate of change

Does speed provide a ‘model for’ rate of change in other contexts? Does JavaMathWorlds (JMW), animated simulation software, assist in the development of the ‘model for’ rate of change? This project investigates the transference of understandings of rate gained in a motion context to a non-motion context. Students were 27 14–15 year old students at an Australian secondary school. The instructional sequence, utilising JMW, provided rich learning experiences of rate of change in the context of a moving elevator. This context connects to students’ prior knowledge. The data taken from pre- and post-tests and student interviews revealed a wide variation in students’ understanding of rate of change. The variation was mapped on a hypothetical learning trajectory and interpreted in the terms of the ‘emergent models’ theory (Gravemeijer, Math Think Learn 1(2):155–177, 1999) and illustrated by specific examples from the data. The results demonstrate that most students were able to use the ‘model of’ rate of change developed in a vertical motion context as a ‘model for’ rate of change in a horizontal motion context. A smaller majority of students were able to use their, often incomplete, ‘model of’ rate of change as a ‘model for’ reasoning about rate of change in a non-motion context.

A new approach to determining environmental flow requirements : sustaining the natural values of floodplains of the southern Murray-Darling Basin

Large overbank flood events play an important role in maintaining largescale ecological processes and connectivity along and across the floodplains and between the rivers and their floodplains in the southern Murray-Darling Basin. However, the regulation of rivers means that extensive overbank flooding can only occur in the rare circumstance of extreme flood events. Recent environmental water allocations have focussed on the largest floodplain blocks (‘icon’ sites) and a small set of specific values (e.g. colonial nesting waterbirds), as well as on trialling fine-scale manipulation of infrastructure (e.g. pumping) to water relatively small areas. There has been no comprehensive systematic assessment of the entire floodplain and its wider set of flood-dependent natural assets (such as ecosystems and species; herein referred to as ‘natural values’) to maximise the effectiveness of environmental water use and to catalogue values likely to be lost. This paper describes an assessment of some 220 000 ha found to support flood-dependent natural values in Victoria. We mapped the geographic distribution and estimated components of the flooding requirements (natural flooding frequency, and maximum period without flooding and minimum duration of each flooding event before significant deterioration) for each natural value. Using an example of one stretch of the River Murray, we show how the resultant spatial data can be used with floodplain inundation modelling to compare the outcomes of real or planned environmental watering events; potentially providing tools for management agencies to conserve a wider range of floodplain values than is currently the case. That is, water managers and the public can see what ecosystems and threatened species are intended to be maintained by environmental watering and what values are intended to be abandoned across the whole floodplain, rather than just seeing the small subset of values and ‘icon’ sites that are intended to be maintained. Examples are provided to illustrate how information about the location, water requirements and extent covered by potential floods for specific values can be used to build adaptive watering strategies for areas as large as the whole floodplain.

The impact of ionic liquids on amyloid fibrilization of AB16-22 : tuning the rate of fibrilization using a reverse Hofmeister strategy

We have shown that the amyloid fibrilization of Aß16-22 follows a reverse hofmeister trend in pILs. Fast fibrilization rates of seconds can be achieved.

Age- and gender-specific rate of fractures in Australia : a population-based study

There is little population-based data concerning fracture rates in Australia. We ascertained all fractures occurring during 2 years in adults aged 35 years and over residing within a defined region (population 218 000), representative of the Australian population. The major strength of this study is the comprehensive ascertainment of fractures, which was ensured by regular searches of the only two radiologic providers in the Geelong Osteoporosis Study region. Nevertheless, vertebral fractures are likely to be underestimated since our ascertainment relied on a clinical indication for a medical imaging procedure. Among those aged 35 – 55 years, the fracture rate (persons per 10 000/year) in men was about double the rate in women (65 vs 35). The fracture rate was almost 7 times higher in women over 60 years versus women less than 55 years of age. In contrast, the fracture rate in men over 60 years was only 50% higher than in men less than 55 years of age (72 vs 104). Fracture rates in women and men were highest at the hip (28 and 10 respectively), spine (21 and 7), distal forearm (Colles’) (18 and 4) and humerus (11 and 3), and were 3–4 times higher in women than men. These fractures accounted for 63% of all fractures in women and 32% in men. By contrast, the rate of lower leg and ankle fractures was less than 10 per 10 000 in both women and men and did not increase to the same extent with age. Hip fracture rates appear high, particularly among the older age strata, compared with retrospective ascertainment in other populations. In Australia, as in many other countries, there is an increasing longevity of the population. The number of women aged 90 years and over increased by 32% and the number of men of this age increased by 48% in the 5 years between the Australian national census of 1991 and 1996. Given stable fracture rates, the substantial health burden imposed by age-related fractures, particularly hip fractures, will continue to escalate in both women and men.

Does the rate of foraging attempts predict ingestion rate for young-of-the-year brook trout (Salvelinus fontinalis) in the field?

To assess the costs and benefits of young fish adopting different behavioural tactics, field studies of juvenile salmonines have assumed that (but did not test whether) the rate of foraging attempts predicts ingestion rate. We tested this assumption by quantifying capture, ingestion, and rejection rates of potential prey items for individual young-of-the-year brook trout (Salvelinus fontinalis) in a lake. Overall, capture rate (a conservative estimate of the rate of foraging attempts) was only a fair predictor of overall ingestion rate (Kendall's 1 = 0.54) and only 46% of captured items (number/minute) were ingested. Surface capture rate was a poor predictor of surface ingestion rate (T = 0.27) and only 1% of captured items were ingested. In contrast, subsurface capture rate was an excellent predictor of subsurface ingestion rate (T = 0.75) and 93% of captured items were ingested. No benthic prey captures were observed. Fish that ingested a low proportion of captured items spent a greater proportion of time moving, moved faster, and pursued prey further than fish that ingested a higher proportion of captured items. Rejection of captured items can represent a significant and little appreciated component of the foraging cycle for young salmonid fishes.

The natural history of self-harm from adolescence to young adulthood : a population-based cohort study

Background Knowledge about the natural history of self-harm is scarce, especially during the transition from adolescence to young adulthood, a period characterised by a sharp rise in self-inflicted deaths. From a repeated measures cohort of a representative sample, we describe the course of self-harm from middle adolescence to young adulthood.

Methods A stratified, random sample of 1943 adolescents was recruited from 44 schools across the state of Victoria, Australia, between August, 1992, and January, 2008. We obtained data pertaining to self-harm from questionnaires and telephone interviews at seven waves of follow-up, commencing at mean age 15·9 years (SD 0·49) and ending at mean age 29·0 years (SD 0·59). Summary adolescent measures (waves three to six) were obtained for cannabis use, cigarette smoking, high-risk alcohol use, depression and anxiety, antisocial behaviour and parental separation or divorce.

Findings 1802 participants responded in the adolescent phase, with 149 (8%) reporting self-harm, More girls (95/947 [10%]) than boys (54/855 [6%]) reported self-harm (risk ratio 1·6, 95% CI 1·2–2·2). We recorded a substantial reduction in the frequency of self-harm during late adolescence. 122 of 1652 (7%) participants who reported self-harm during adolescence reported no further self-harm in young adulthood, with a stronger continuity in girls (13/888) than boys (1/764). During adolescence, incident self-harm was independently associated with symptoms of depression and anxiety (HR 3·7, 95% CI 2·4–5·9), antisocial behaviour (1·9, 1·1–3·4), high-risk alcohol use (2·1, 1·2–3·7), cannabis use (2·4, 1·4–4·4), and cigarette smoking (1·8, 1·0–3·1). Adolescent symptoms of depression and anxiety were clearly associated with incident self-harm in young adulthood (5·9, 2·2–16).

Interpretation Most self-harming behaviour in adolescents resolves spontaneously. The early detection and treatment of common mental disorders during adolescence might constitute an important and hitherto unrecognised component of suicide prevention in young adults.

Funding National Health and Medical Research Council, Australia, and operational infrastructure support programme, Government of Victoria, Australia.

Basal metabolic rate of canidae from hot deserts to cold arctic climates

Canids form the most widely distributed family within the order Carnivora, with members present in a multitude of different environments from cold arctic to hot, dry deserts. We reviewed the literature and compared 24 data sets available on the basal metabolic rate (BMR) of 12 canid species, accounting for body mass and climate, to examine inter- and intraspecific variations in mass-adjusted BMR between 2 extreme climates (arctic and hot desert). Using both conventional and phylogenetically independent analysis of covariance, we found that canids from the arctic climate zone had significantly higher mass-adjusted BMR than species from hot deserts. Canids not associated with either arctic or desert climates had an intermediate and more variable mass-adjusted BMR. The climate effect also was significant at the intraspecific level in species for which we had data in 2 different climates. Arctic and desert climates represent contrasting combinations of ambient temperatures and water accessibility that require opposite physiological adaptations in terms of metabolism. The fact that BMR varies within species when individuals are subjected to different climate regimes further suggests that climate is an important determinant of BMR.

Effect of genotype and sex on fiber growth rate of alpacas for their first year of fleece production

The sale of alpaca fiber is the main income for thousands of families in the Central Andes of Peru. Little information exists on the fiber length growth rate of alpaca (FLG), especially throughout their first year of life when the fiber is most valuable. We aimed to determine the monthly FLG of 22 alpaca offspring of two genotypes (9 Suri, 13 Huacaya) and considering sex differences (10 females, 12 males) in the High Andes of Peru. FLG growth was determined using dye-bands. An additive lineal model with three factors (genotype, sex, month) was used for statistic analysis. To evaluate the effect of genotype and sex on the profile of the FLG throughout the year a two factor repeated-measures model was used. The results showed that FLG was affected by genotype and month but not sex. The Suri genotype had 20% higher FLG than Huacaya genotype alpacas (1.34 vs 1.10 cm/month, P < 0.001). FLG increased over each of the first three months (P < 0.05) and then maintained a near constant rate for the remainder of the first year. The resulting staple length indicates that shearing at ages from 8 to 12 months of age will provide fleeces of sufficient length for textile processing.