CASE STUDIES
about transmission vectors and could not enforce draconian measures such as quarantine or precautionary slaughter just on the off chance they might be effective. Using GenStat to analyse data on time, location, severity and duration of outbreaks, however, he was able to identify patterns. There was a progressive model of spread, with incidence having started close to the road leading to the regional administrative centre and tending, on the whole, to move from one community to the next nearest. Jumps from one focus to another rarely crossed water; the exceptions being where there was frequent traffic between them. After a week or so, those animals which had not died ceased to display symptoms, although there was limited recurrence. Working from these findings, he encouraged villagers to keep goats and cattle inside areas surrounded by irrigation ditches where possible. Those tending the herds he advised to sleep on the other side of a channel from their charges where feasible, and not to make unnecessary visits to neighbouring communities. Within a month, new symptomatic outbreaks had become rare. Six months later, though the problem had yet to be identified, it seemed to have disappeared completely.
EAR WE GO
Sensory organs are extraordinary instruments in many ways, not least the range of input magnitudes with which they can cope without damage or loss of perceptual resolution. In that latter respect – the ability to discriminate between signal and noise at very low amplitudes – the ear is particularly noteworthy. At its lower limit of perception, human eardrum displacement of less than the diameter of a hydrogen atom can be interpreted as useful information. Tis performance is achieved despite levels of thermal noise 10 times greater than this threshold signal. Researchers at Rockefeller University
in New York addressed this puzzle using a statistical approach based on fractional Brownian motion modelling. Teir description of their work is an intriguing detective story of exploratory hypotheses guided by experimental results, with analysis and modelling conducted in MatLab. Te physical mechanism involved uses a
system of hair bundles in a fluid medium, and using microrheological methods the researchers examined the statistics of their thermal fluctuations. What they found was that the motion
of a hair bundle didn’t match what might be expected; autocorrelation showing a power-law relationship and an unexpected frequency slope. From this, they deduced that the thermal motion of the bundle is probably due to subdiffusion, a hypothesis they proceeded to cross test. Having established by further data
analysis that observed fluctuations were not
The effect of viscoelasticity on mechanotransduction: frequency resonance. (From Koslov et al.)
influenced by instrumental factors, they further hypothesised that the observed phenomena could be explained by coupling of an elastic element with anomalous fractional Brownian motion. Tey therefore needed to identify a feasible physical structure and suitable viscoelastic model which would support this hypothesis. Tis was achieved by comparing power spectra statistics from physical experiments with theoretical predictions through maximum likelihood fitting. Te result is a picture of a frequency-
specific differentiated transduction process, which passes signal preferentially compared to bands in which noise predominates.
Further information: A. S. Kozlov, D. Andor- Ardo, and A. J. Hudspeth, ‘Anomalous Brownian motion discloses viscoelasticity in the ear’s mechanoelectrical-transduction apparatus’. PNAS, 2012. 109(8): p.2896-2901.
STRIKING ATTITUDES
Academic studies oſten arise from an original intuition or observation. Tey also, very oſten, have practical implications. Phuoc is a young researcher, at the very beginning of a career in academic social science and embarking on her first self- directed research study. She proposed an investigation into individual responses to sexual orientation and their implications for social policy in changing societies, referenced against the
work of Gregory M. Herek in US American contexts. Her data is obtained using
survey methods based around four-way triangulated multiple design questionnaires, designed to synchronise with Herek’s but with added dimensions. She starts by sorting and filtering data in Excel, extracting particular subsets which exhibit patterns of interest before subjecting those to more searching analytic methods. Principal component and discriminant function analysis then siſt out both the predictors of particular responses and the triggers most likely to produce those responses.
22 BEYOND THE NUMBERS A STATISTICS SPECIAL
Her first data collection and
analysis cycle, focusing on respondents in their late teens, shows the same predictors of negative or hostile attitudes as in Herek’s US American studies. Most prominent are place of birth, socioeconomic background, religion and whether or not the respondent personally knows someone with a different sexual orientation to themselves. Tose responses are, however, consistently expressed at considerably lower intensity and frequency than Herek found. More interesting is the
distribution of triggers, as revealed
by varied question structures. Even in highly liberal response sets, where a majority of responses are positive, any residual hostility is concentrated in the same small number of trigger areas. Conversely, even in predominantly negative response sets there are surprising, and surprisingly consistent, positive exceptions in very specific areas. Tese sharply defined areas of cognitive dissonance are closely replicated across multiple cross-sectional samples, and now form the target for the next round of data analytic attention using an expanded and targeted sampling regime.
SCIENTIFIC COMPUTING WORLD
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