1,282 research outputs found
The investigation of time dependent flame structure by ionization probes
Ionization probes were used to measure mean ionization current and frequency spectra, auto-correlations and cross-correlations in jet flames with variation in the initial Reynolds numbers and equivalence ratios. Special attention was paid to the transitional region between the burner exit plane and the plane of onset of turbulence
On modeling player fitness in training for team sports with application to professional rugby
It is increasingly important for professional sports teams to monitor player fitness in order to optimize performance. Models have been put forward linking fitness in training to performance in competition but rely on regular measurements of player fitness. As formal tests for measuring player fitness are typically time-consuming and inconvenient, measurements are taken infrequently. As such, it may be challenging to accurately predict performance in competition as player fitness is unknown.Alternatively, other data, such as how the players are feeling, may be measured more regularly. This data, however, may be biased as players may answer the questions differently and these differences may dominate the data. Linear Mixed Methods and Support Vector Machines were used to estimate player fitness from available covariates at times when explicit measures of fitness are unavailable. Using data provided by Glasgow Warriors Rugby Club, a case study was used to illustrate the application and value of these models. Both models performed well with R2 values ranging from 60% to 85%, demonstrating that the models largely captured the biases introduced by individual players
In situ tropical peatland ire emission factors and their variability, as determined by field measurements in peninsula Malaysia
Fires in tropical peatlands account for >25% of estimated total greenhouse gas emissions from deforestation and degradation. Despite significant global and regional impacts, our understanding of specific gaseous fire emission factors (EFs) from tropical peat burning is limited to a handful of studies. Furthermore, there is substantial variability in EFs between sampled fires and/or studies. For example, methane EFs vary by 91% between studies. Here we present new fire EFs for the tropical peatland ecosystem; the first EFs measured for Malaysian peatlands, and only the second comprehensive study of EFs in this crucial environment. During August 2015 (under El Niño conditions) and July 2016, we embarked on field campaigns to measure gaseous emissions at multiple peatland fires burning on deforested land in Southeast Pahang (2015) and oil palm plantations in North Selangor (2016), Peninsula Malaysia. Gaseous emissions were measured using open-path Fourier transform infrared spectroscopy. The IR spectra were used to retrieve mole fractions of 12 different gases present within the smoke (including carbon dioxide and methane), and these measurements used to calculate EFs. Peat samples were taken at each burn site for physicochemical analysis and to explore possible relationships between specific physicochemical properties and fire EFs. Here we present the first evidence to indicate that substrate bulk density affects methane fire EFs reported here. This novel explanation of interplume, within-biome variability, should be considered by those undertaking greenhouse gas accounting and haze forecasting in this region and is of importance to peatland management, particularly with respect to artificial compaction
Comparison of the paper-based and electronic versions of the Dermatology Life Quality Index (DLQI): evidence of equivalence
BACKGROUND:
The use of patient-reported outcome measures in electronic format has been increasing. However, these formats are usually not validated or compared to the original paper-based formats, so there is no evidence that they are completed in the same way.
OBJECTIVES:
The aim of this study was to compare the conventional paper version and a web-based application version (iPad® ) of the DLQI to assess equivalence of scores.
METHODS:
The study employed a randomized cross-over design using a within-subjects comparison of the two formats of the questionnaire. International Society for Pharmacoeconomics and Outcomes Research (ISPOR) guidelines were followed. Subjects aged over 18 years with any confirmed skin condition were recruited from a teaching hospital dermatology outpatient clinic. Expected Intra-class correlation coefficient (ICC) was 0.9 (α = 0.05) RESULTS: A total of 104 patients were recruited, median age=53.5 years (IQR=37.3-67.8, 43% male). The Intraclass correlation coefficient (ICC) showed high concordance between the total DLQI scores from paper and iPad® versions (ICC = 0.98; 95% CI 0.97-0.99). Patients took a median of 78 seconds to complete the electronic version and 73 seconds for paper (p=0.008): 76% preferred the electronic version and perceived completion to take a shorter time.
CONCLUSIONS:
There is high concordance, and thus equivalence, between the iPad and paper versions of the DLQI, with an ICC of 0.98, and a clear patient preference for the iPad version
Parent and child agreement for acute stress disorder, post-traumatic stress disorder and other psychopathology in a prospective study of children and adolescents exposed to single-event trauma
Examining parent-child agreement for Acute Stress Disorder (ASD) and Post-Traumatic Stress Disorder (PTSD) in children and adolescents is essential for informing the assessment of trauma-exposed children, yet no studies have examined this relationship using appropriate statistical techniques. Parent-child agreement for these disorders was examined by structured interview in a prospective study of assault and motor vehicle accident (MVA) child survivors, assessed at 2-4 weeks and 6 months post-trauma. Children were significantly more likely to meet criteria for ASD, as well as other ASD and PTSD symptom clusters, based on their own report than on their parent's report. Parent-child agreement for ASD was poor (Cohen's κ = -.04), but fair for PTSD (Cohen's κ = .21). Agreement ranged widely for other emotional disorders (Cohen's κ = -.07-.64), with generalised anxiety disorder found to have superior parent-child agreement (when assessed by phi coefficients) relative to ASD and PTSD. The findings support the need to directly interview children and adolescents, particularly for the early screening of posttraumatic stress, and suggest that other anxiety disorders may have a clearer presentation post-trauma
The Size Variance Relationship of Business Firm Growth Rates
The relationship between the size and the variance of firm growth rates is
known to follow an approximate power-law behavior where is the firm size and is an
exponent weakly dependent on . Here we show how a model of proportional
growth which treats firms as classes composed of various number of units of
variable size, can explain this size-variance dependence. In general, the model
predicts that must exhibit a crossover from to
. For a realistic set of parameters, is
approximately constant and can vary in the range from 0.14 to 0.2 depending on
the average number of units in the firm. We test the model with a unique
industry specific database in which firm sales are given in terms of the sum of
the sales of all their products. We find that the model is consistent with the
empirically observed size-variance relationship
Rank Statistics in Biological Evolution
We present a statistical analysis of biological evolution processes.
Specifically, we study the stochastic replication-mutation-death model where
the population of a species may grow or shrink by birth or death, respectively,
and additionally, mutations lead to the creation of new species. We rank the
various species by the chronological order by which they originate. The average
population N_k of the kth species decays algebraically with rank, N_k ~ M^{mu}
k^{-mu}, where M is the average total population. The characteristic exponent
mu=(alpha-gamma)/(alpha+beta-gamma)$ depends on alpha, beta, and gamma, the
replication, mutation, and death rates. Furthermore, the average population P_k
of all descendants of the kth species has a universal algebraic behavior, P_k ~
M/k.Comment: 4 pages, 3 figure
Dynamics on expanding spaces: modeling the emergence of novelties
Novelties are part of our daily lives. We constantly adopt new technologies,
conceive new ideas, meet new people, experiment with new situations.
Occasionally, we as individuals, in a complicated cognitive and sometimes
fortuitous process, come up with something that is not only new to us, but to
our entire society so that what is a personal novelty can turn into an
innovation at a global level. Innovations occur throughout social, biological
and technological systems and, though we perceive them as a very natural
ingredient of our human experience, little is known about the processes
determining their emergence. Still the statistical occurrence of innovations
shows striking regularities that represent a starting point to get a deeper
insight in the whole phenomenology. This paper represents a small step in that
direction, focusing on reviewing the scientific attempts to effectively model
the emergence of the new and its regularities, with an emphasis on more recent
contributions: from the plain Simon's model tracing back to the 1950s, to the
newest model of Polya's urn with triggering of one novelty by another. What
seems to be key in the successful modelling schemes proposed so far is the idea
of looking at evolution as a path in a complex space, physical, conceptual,
biological, technological, whose structure and topology get continuously
reshaped and expanded by the occurrence of the new. Mathematically it is very
interesting to look at the consequences of the interplay between the "actual"
and the "possible" and this is the aim of this short review.Comment: 25 pages, 10 figure
Critical and Near-Critical Branching Processes
Scale-free dynamics in physical and biological systems can arise from a
variety of causes. Here, we explore a branching process which leads to such
dynamics. We find conditions for the appearance of power laws and study
quantitatively what happens to these power laws when such conditions are
violated. From a branching process model, we predict the behavior of two
systems which seem to exhibit near scale-free behavior--rank-frequency
distributions of number of subtaxa in biology, and abundance distributions of
genotypes in an artificial life system. In the light of these, we discuss
distributions of avalanche sizes in the Bak-Tang-Wiesenfeld sandpile model.Comment: 9 pages LaTex with 10 PS figures. v.1 of this paper contains results
from non-critical sandpile simulations that were excised from the published
versio
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