Outlier analysis for a silicon nanoparticle population balance model

© 2016 The Combustion Institute We assess the impact of individual experimental observations on a multivariate population balance model for the formation of silicon nanoparticles from the thermal decomposition of silane by means of basic regression influence diagnostics. The nanoparticle model is closely related to one which has been used to simulate soot formation in flames and includes morphological and compositional details which allow re presentation of primary particles within aggregates, and of coagulation, surface growth, and sintering processes. Predicted particle size distributions are optimised against 19 experiments across ranges of initial temperature, pressure, residence time, and initial silane mass fraction. The influence of each experimental observation on the model parameter estimates is then quantified using the Cook distance and DFBETA measures. Seven model parameters are included in the analysis, with five Arrhenius pre-exponential factors in the gas-phase kinetic rate expressions, and two kinetic rate constants in the population balance model. The analysis highlights certain experimental conditions and kinetic parameters which warrant closer inspection due to large influence, thus providing clues as to which aspects of the model require improvement. We find the insights provided can be useful for future model development and planning of experiments.This work was partly funded by the Cambridge Australia Trust, by the National Research Foundation (NRF), Prime Minister’s Office, Singapore under its Campus for Research Excellence and Technological Enterprise (CREATE) programme, and by the European Union Horizon 2020 Research and Innovation Programme under Grant agreement 646121

Immediate and short-term effects of short- and long-duration isometric contractions in patellar tendinopathy

Objectives: Isometric muscle contractions are used in the management of patellar tendinopathy to manage pain and improve function. Little is known about whether long- or short-duration contractions are optimal to improve pain. This study examined the immediate and short-term (4 weeks) effects of long- and short-duration isometric contraction on patellar tendon pain, and tendon adaptation. Design: Repeated measures within groups. Setting: Clinical primary care. Patients: Participants (n = 16, males) with patellar tendinopathy. Intervention: Short-duration (24 sets of 10 seconds) or long-duration (6 sets of 40 seconds) isometric knee extension loading (85% maximal voluntary contraction), for 4 weeks. Main Outcome Measure: Immediate change in pain with single-leg decline squat (SLDS) and hop, as well as change in pain and tendon adaptation [within-session anterior–posterior (AP) strain] were assessed over 4 weeks. Results: Pain was significantly reduced after isometric loading on both SLDS (P < 0.01) and hop tests (P < 0.01). Pain and quadriceps function improved over the 4 weeks (P < 0.05). There was significant AP strain at each measurement occasion (P < 0.01). Although transverse strain increased across the training period from ∼14% to 22%, this was not significant (P = 0.08). Conclusions: This is the first study to show that short-duration isometric contractions are as effective as longer duration contractions for relieving patellar tendon pain when total time under tension is equalized. This finding provides clinicians with greater options in prescription of isometric loading and may be particularly useful among patients who do not tolerate longer duration contractions. The trend for tendon adaptation over the short 4-week study period warrants further investigation

Are foot and ankle characteristics associated with falls in people with rheumatoid arthritis? A prospective study.

OBJECTIVE: To determine whether foot and ankle characteristics are associated with falls in people with rheumatoid arthritis (RA). METHODS: Two hundred and one adults with RA were recruited from rheumatology outpatient clinics in Auckland, New Zealand. Clinical characteristics, common fall risk factors, and foot and ankle variables were measured. Participants were prospectively studied for 12 months, to record the occurrence of falls using falls diaries. Logistic regression analysis identified baseline variables which were independent predictors of falls over the 12 months. RESULTS: Eighty-four (42%) participants fell at least once and 39 (19%) experienced multiple (>1) falls over the 12-month follow-up period. In logistic regression analysis, including age and significant baseline variables in bivariate analysis but not baseline fall history, presence of foot or ankle tender joints (odds ratio (OR) 1.95, P=0.034) and psychotropic medication (OR 2.35, P=0.025) were independent predictors of prospective falls. However, when baseline fall history was included in the analysis, psychotropic medication (OR 2.34, P=0.025) and baseline fall history (over the preceding 12 months) (OR 2.27, P=0.008) were independent predictors of prospective falls. CONCLUSION: Foot and ankle characteristics are not associated with falls in people with RA, independent of prior falls. Enquiry about prior falls and psychotropic medications may assist in identifying patients with RA who are at high risk of future falls. This article is protected by copyright. All rights reserved

Nonlinear Relaxation Dynamics in Elastic Networks and Design Principles of Molecular Machines

Analyzing nonlinear conformational relaxation dynamics in elastic networks corresponding to two classical motor proteins, we find that they respond by well-defined internal mechanical motions to various initial deformations and that these motions are robust against external perturbations. We show that this behavior is not characteristic for random elastic networks. However, special network architectures with such properties can be designed by evolutionary optimization methods. Using them, an example of an artificial elastic network, operating as a cyclic machine powered by ligand binding, is constructed.Comment: 12 pages, 9 figure

Age-related differences in foot mobility in individuals with patellofemoral pain

Background Age-related changes in midfoot mobility have the potential to influence success with foot orthoses intervention in people with patellofemoral pain (PFP). The aim of this study was to determine whether older people with PFP demonstrate less foot mobility than younger adults with PFP. Methods One hundred ninety four participants (113 (58%) women, age 32 ± 7 years, BMI 25 ± 4.9 kg/m2) with PFP (≥ 6 weeks duration) were included, with foot mobility quantified using reliable and valid methods. K-means cluster analysis classified participants into three homogenous groups based on age. After cluster formation, univariate analyses of co-variance (covariates: sex, weight) were used to compare midfoot height mobility, midfoot width mobility, and foot mobility magnitude between age groups (significance level 0.05). Results Cluster analysis revealed three distinct age groups: 18–29 years (n = 70); 30–39 years (n = 101); and 40–50 years (n = 23). There was a significant main effect for age for midfoot height mobility (p  0.05). Conclusion Individuals with PFP aged 40–50 years have less foot mobility than younger adults with PFP. These findings may have implications for evaluation and treatment of older individuals with PFP

Age and gender differences in disabling foot pain using different definitions of the manchester foot pain and disability index

Extent: 9p.Background: The Manchester Foot Pain and Disability Index (MFPDI) has been used to determine the prevalence of disabling foot pain in several studies, however there is some debate as to which case definition is most appropriate. The objective of this study was to explore age and gender differences in the proportion of people with disabling foot pain using three different case definitions of the MFPDI and for each individual MFPDI item. Methods: A random sample of 223 participants aged 27 to 90 years (88 males and 135 females) from the North West Adelaide Health Study, who reported having pain, aching or stiffness in either of their feet on most days in the last month, completed the MFPDI by telephone interview. The proportion of people with disabling foot pain was determined using three definitions: (i) Definition A-at least one of the 17 items documented on at least some days in the last month; (ii) Definition B-at least one of the 17 items documented on most/every day(s) in the last month, and; (iii) Definition C-at least one of the ten functional limitation items documented on most/every day(s) in the last month. Cross-tabulations and chi-squared statistics were used to explore differences in responses to the MFPDI items according to age and gender. Results: The proportion of people with disabling foot pain according to each definition was as follows: Definition A (100%), Definition B (95.1%) and Definition C (77.6%). Definition C was most sensitive to age and gender differences. Exploration of individual MFPDI items indicated that age significantly affected both the pain intensity and functional limitation items, with younger people more likely to report their foot pain being worse in the morning, and older people more likely to report functional limitations. Although gender did not influence responses to the personal appearance items, women were more likely report functional limitations than men. Conclusions: Definition C of the MFPDI is more sensitive to age and gender differences in the proportion of people with disabling foot pain, and would therefore seem to be the most appropriate case definition to use in epidemiological studies involving a broad age range of participants.Hylton B Menz, Tiffany K Gill, Anne W Taylor and Catherine L Hil

Validity of self-assessment of hallux valgus using the Manchester scale

<p>Abstract</p> <p>Background</p> <p>Hallux valgus (HV) is a common condition involving the progressive subluxation of the first metatarsophalangeal joint due to lateral deviation of the hallux and medial deviation of the first metatarsal. The objective of this study was to evaluate the re-test reliability and validity of self-assessment of HV using a simple clinical screening tool involving four standardised photographs (the Manchester scale), in order to determine whether this tool could be used for postal surveys of the condition.</p> <p>Methods</p> <p>HV was assessed with the Manchester scale in 138 people aged 65 to 93 years of age (102 women and 36 men) as part of a larger randomised controlled trial. At the six month follow-up assessment, HV was reassessed to determine re-test reliability, and participants were asked to self-assess their degree of HV independent of the examiners. Associations between (i) baseline and follow-up assessments of the examiners and (ii) participant and examiner assessments were performed using weighted kappa statistics. Analyses were then repeated after HV was dichotomised as present or absent using unweighted kappa, and sensitivity and specificity of self-assessment of HV was determined.</p> <p>Results</p> <p>Re-test reliability of the examiners was substantial to almost perfect (weighted kappa = 0.78 to 0.90), and there was a substantial level of agreement between observations of the participants and the examiners (weighted kappa = 0.71 to 0.80). Overall, there was a slight tendency for participants to rate their HV as less severe than the examiners. When the Manchester scale scores were dichotomised, agreement was substantial to almost perfect for both re-test comparisons (kappa = 0.80 to 0.89) and substantial for comparisons between participants and examiners (kappa = 0.64 to 0.76). The sensitivity and specificity of self-assessment of HV using the dichotomous scale were 85 and 88%, respectively.</p> <p>Conclusions</p> <p>The Manchester scale demonstrates high re-test reliability, and self-assessment scores obtained by participants are strongly associated with scores obtained by examiners. These findings indicate that the tool can be used with confidence in postal surveys to document the presence and severity of HV.</p> <p>Trial registration</p> <p>ACTRN12608000065392</p

Reliability of the TekScan MatScan® system for the measurement of plantar forces and pressures during barefoot level walking in healthy adults

<p>Abstract</p> <p>Background</p> <p>Plantar pressure systems are increasingly being used to evaluate foot function in both research settings and in clinical practice. The purpose of this study was to investigate the reliability of the TekScan MatScan^®system in assessing plantar forces and pressures during barefoot level walking.</p> <p>Methods</p> <p>Thirty participants were assessed for the reliability of measurements taken one week apart for the variables maximum force, peak pressure and average pressure. The following seven regions of the foot were investigated; heel, midfoot, 3^rd-5^thmetatarsophalangeal joint, 2^ndmetatarsophalangeal joint, 1^stmetatarsophalangeal joint, hallux and the lesser toes.</p> <p>Results</p> <p>Reliability was assessed using both the mean and the median values of three repeated trials. The system displayed moderate to good reliability of mean and median calculations for the three analysed variables across all seven regions, as indicated by intra-class correlation coefficients ranging from 0.44 to 0.95 for the mean and 0.54 to 0.97 for the median, and coefficients of variation ranging from 5 to 20% for the mean and 3 to 23% for the median. Selecting the median value of three repeated trials yielded slightly more reliable results than the mean.</p> <p>Conclusions</p> <p>These findings indicate that the TekScan MatScan^®system demonstrates generally moderate to good reliability.</p