Techniques for measuring weight bearing during standing and walking

OBJECTIVE: To classify and assess techniques for measuring the amount of weight bearing during standing and walking.BACKGROUND: A large variety of weight bearing measuring techniques exists. This review describes their advantages and limitations to assist clinicians and researchers in selecting a technique for their specific application in measuring weight bearing.METHODS: A literature search was performed in Pubmed-Medline, CINAHL, and EMBASE. Measurement techniques were classified in 'clinical examination', 'scales', 'biofeedback systems', 'ambulatory devices' and 'platforms', and assessed on aspects of methodological quality, application, and feasibility.RESULTS: A total of 68 related articles was evaluated. The clinical examination technique is a crude method to estimate the amount of weight bearing. Scales are useful for static measurements to evaluate symmetry in weight bearing. Biofeedback systems give more reliable, accurate and objective data on weight bearing compared to clinical examination and scales, but the high costs could limit their use in physical therapy departments. The ambulatory devices can measure weight bearing with good accuracy and reliability in the hospital and at home. Platforms have the best methodological quality, but are mostly restricted to a gait laboratory, need trained personnel, and are expensive.CONCLUSIONS: The choice of a technique largely depends upon the criteria discussed in this review; however the clinical utilisation, the research question posed, and the available budget also play a role. The new developments seen in the field of 'ambulatory devices' are aimed at extending measuring time, and improved practicality in data collection and data analysis. For these latter devices, however, mainly preliminary studies have been published about devices that are not (yet) commercially available.</p

Effects of summary knowledge of results in motor skills acquisition

The effects of Summary Knowledge of Results (KR) were tested, using 30 volunteers and a positioning task in which a tennis ball had to be transported in 30 trials, following a specific sequence and with a target time of 3000 msec. Ten minutes after the acquisition phase, the transfer test was performed with 10 trials of different sequences and target times. The retention test took place 24 hours later with 10 trials of the same sequence and target time as the acquisition phase. In the transfer and retention tests, KR was not provided. The volunteers were randomly divided into three groups: G5 (KR every five trials); G3 (KR every three trials) and G100 (KR every trial). The results showed that G3 had a smaller absolute error than G100. However, G3 and G5 had a smaller constant error than G100. In general, the effects of G3 and G5 on motor skill acquisition could be caused by the lower KR frequency, which was 33% and 20% respectively.El efecto del conocimiento de los resultados (KR) resumen ha sido probado por 30 voluntarios en tarea de posicionamiento que requiere el transporte de una pelota de tenis en una secuencia específica con el tiempo objetivo de 3000 ms. en 30 ensayos. Diez minutos después de la fase de adquisición se jugó el test de transferencia con 10 ensayos con diferente secuencia y tempo objetivo. La retención se realizó la prueba 24 horas más tarde con la misma secuencia y tiempo objetivo fase de adquisición. En los testes de transferencia y retención de la CR no fue suministrado. Los voluntarios fueron divididos aleatoriamente en tres grupos: G5 (CR después de 5 ensayos); G3 (CR después de 3 ensayos) y G100 (CR en todos los ensayos). El resultado mostró que G3 tuvieron menor error absoluto que G100. Sin embargo, G3 y G5 se han registrado menor error constante que G100. En general, los efectos de G3 y G5 en la adquisición de las habilidades motoras pueden ser causados por la disminución de frecuencias CR, que fueron 33% y 20 %, respectivamente.O efeito do conhecimento de resultados (CR) sumário foi testado por 30 voluntários em uma tarefa de posicionamento a qual exigia o transporte de uma bola de tênis em uma sequência específica com tempo alvo de 3000 mseg. durante 30 tentativas. Dez minutos após a fase de aquisição foi desempenhado o teste de transferência com 10 tentativas com sequência e tempo alvo diferente. O teste de retenção foi realizado 24 horas mais tarde com a mesma sequência e tempo alvo da fase de aquisição. Nos testes de transferência e retenção o CR não foi fornecido. Os voluntários foram aleatoriamente divididos em três grupos: G5 (CR depois de 5 tentativas); G3 (CR depois de 3 tentativas) e G100 (CR em todas tentativas). O resultado mostrou que G3 apresentou menor erro absoluto que G100. Entretanto, G3 e G5 registraram menor erro constante que G100. Em geral, os efeitos de G3 e G5 sobre a aquisição de habilidades motoras podem ser causados pelas frequências reduzidas de CR, que foram de 33% e 20%, respectivamente

The Subak in Diaspora: Balinese Farmers and the Subak in South Sulawesi

The subak has a long history as an irrigators’ institution on Bali. It has also spread across Indonesia along with Balinese farmers who were resettled by colonial and post-colonial governments or who have migrated spontaneously since colonial times. While subaks have been much researched in Bali itself, little is known about subaks outside Bali. Luwu District in South Sulawesi is one of the areas where thousands of Balinese families settled in the last four decades. Based on research in this transmigration area, this paper analyzes the emergence and development of the subak in relation to the development of irrigation infrastructure of a state-built irrigation system. A comparison between two Balinese settlements in the same system shows that differences in infrastructural and managerial conditions and arrangements between parts of the irrigation system were major determinants of the institutional space allowed for the subak and ways in which the subaks developed

How Noisy Adaptation of Neurons Shapes Interspike Interval Histograms and Correlations

Channel noise is the dominant intrinsic noise source of neurons causing variability in the timing of action potentials and interspike intervals (ISI). Slow adaptation currents are observed in many cells and strongly shape response properties of neurons. These currents are mediated by finite populations of ionic channels and may thus carry a substantial noise component. Here we study the effect of such adaptation noise on the ISI statistics of an integrate-and-fire model neuron by means of analytical techniques and extensive numerical simulations. We contrast this stochastic adaptation with the commonly studied case of a fast fluctuating current noise and a deterministic adaptation current (corresponding to an infinite population of adaptation channels). We derive analytical approximations for the ISI density and ISI serial correlation coefficient for both cases. For fast fluctuations and deterministic adaptation, the ISI density is well approximated by an inverse Gaussian (IG) and the ISI correlations are negative. In marked contrast, for stochastic adaptation, the density is more peaked and has a heavier tail than an IG density and the serial correlations are positive. A numerical study of the mixed case where both fast fluctuations and adaptation channel noise are present reveals a smooth transition between the analytically tractable limiting cases. Our conclusions are furthermore supported by numerical simulations of a biophysically more realistic Hodgkin-Huxley type model. Our results could be used to infer the dominant source of noise in neurons from their ISI statistics

Bedbugs evolved before their bat hosts and did not co-speciate with ancient humans

All 100+ bedbug species (Cimicidae) are obligate blood-sucking parasites [1, 2]. In general, blood sucking (hematophagy) is thought to have evolved in generalist feeders adventitiously taking blood meals [3, 4], but those cimicid taxa currently considered ancestral are putative host specialists [1, 5]. Bats are believed to be the ancestral hosts of cimicids [1], but a cimicid fossil [6] predates the oldest known bat fossil [7] by >30 million years (Ma). The bedbugs that parasitize humans [1, 8] are host generalists, so their evolution from specialist ancestors is incompatible with the "resource efficiency" hypothesis and only partially consistent with the "oscillation" hypothesis [9-16]. Because quantifying host shift frequencies of hematophagous specialists and generalists may help to predict host associations when vertebrate ranges expand by climate change [17], livestock, and pet trade in general and because of the previously proposed role of human pre-history in parasite speciation [18-20], we constructed a fossil-dated, molecular phylogeny of the Cimicidae. This phylogeny places ancestral Cimicidae to 115 mya as hematophagous specialists with lineages that later frequently populated bat and bird lineages. We also found that the clades, including the two major current urban pests, Cimex lectularius and C. hemipterus, separated 47 mya, rejecting the notion that the evolutionary trajectories of Homo caused their divergence [18-21]

Advanced Methods for Dose and Regimen Finding During Drug Development: Summary of the EMA/EFPIA Workshop on Dose Finding (London 4-5 December 2014)

Inadequate dose selection for confirmatory trials is currently still one of the most challenging issues in drug development, as illustrated by high rates of late-stage attritions in clinical development and postmarketing commitments required by regulatory institutions. In an effort to shift the current paradigm in dose and regimen selection and highlight the availability and usefulness of well-established and regulatory-acceptable methods, the European Medicines Agency (EMA) in collaboration with the European Federation of Pharmaceutical Industries Association (EFPIA) hosted a multistakeholder workshop on dose finding (London 4-5 December 2014). Some methodologies that could constitute a toolkit for drug developers and regulators were presented. These methods are described in the present report: they include five advanced methods for data analysis (empirical regression models, pharmacometrics models, quantitative systems pharmacology models, MCP-Mod, and model averaging) and three methods for study design optimization (Fisher information matrix (FIM)-based methods, clinical trial simulations, and adaptive studies). Pairwise comparisons were also discussed during the workshop; however, mostly for historical reasons. This paper discusses the added value and limitations of these methods as well as challenges for their implementation. Some applications in different therapeutic areas are also summarized, in line with the discussions at the workshop. There was agreement at the workshop on the fact that selection of dose for phase III is an estimation problem and should not be addressed via hypothesis testing. Dose selection for phase III trials should be informed by well-designed dose-finding studies; however, the specific choice of method(s) will depend on several aspects and it is not possible to recommend a generalized decision tree. There are many valuable methods available, the methods are not mutually exclusive, and they should be used in conjunction to ensure a scientifically rigorous understanding of the dosing rationale

Fossil Groups Origins: I. RX J105453.3+552102 a very massive and relaxed system at z~0.5

The most accepted scenario for the origin of fossil groups (FGs) is that they are galaxy associations in which the merging rate was fast and efficient. These systems have assembled half of their mass at early epoch of the Universe, subsequently growing by minor mergers. They could contain a fossil record of the galaxy structure formation. We have started a project in order to characterize a large sample of FGs. In this paper we present the analysis of the fossil system RX J105453.3+552102. Optical deep images were used for studying the properties of the brightest group galaxy and for computing the photometric luminosity function of the group. We have also performed a detail dynamical analysis of the system based on redshift data for 116 galaxies. This galaxy system is located at z=0.47, and shows a quite large line-of-sight velocity dispersion \sigma_{v}~1000 km/s. Assuming the dynamical equilibrium, we estimated a virial mass of M ~ 10^{15} h_{70} M_{\odot}. No evidence of substructure was found within 1.4 Mpc radius. We found a statistically significant departure from Gaussianity of the group members velocities in the most external regions of the group. This could indicate the presence of galaxies in radial orbits in the external region of the group. We also found that the photometrical luminosity function is bimodal, showing a lack of M_{r} ~ -19.5 galaxies. The brightest group galaxy shows low Sersic parameter (n~2) and a small peculiar velocity. Indeed, our accurate photometry shows that the difference between the brightest and the second brightest galaxies is 1.9 mag in the r-band, while the classical definition of FGs is based on a magnitude gap of 2. We conclude that this fossil system does not follow the empirical definition of FGs. Nevertheless, it is a massive, old and undisturbed galaxy system with little infall of L^{*} galaxies since its initial collapse.Comment: 17 pages, 14 figures, accepted for publication at A&

Intrinsic gain modulation and adaptive neural coding

In many cases, the computation of a neural system can be reduced to a receptive field, or a set of linear filters, and a thresholding function, or gain curve, which determines the firing probability; this is known as a linear/nonlinear model. In some forms of sensory adaptation, these linear filters and gain curve adjust very rapidly to changes in the variance of a randomly varying driving input. An apparently similar but previously unrelated issue is the observation of gain control by background noise in cortical neurons: the slope of the firing rate vs current (f-I) curve changes with the variance of background random input. Here, we show a direct correspondence between these two observations by relating variance-dependent changes in the gain of f-I curves to characteristics of the changing empirical linear/nonlinear model obtained by sampling. In the case that the underlying system is fixed, we derive relationships relating the change of the gain with respect to both mean and variance with the receptive fields derived from reverse correlation on a white noise stimulus. Using two conductance-based model neurons that display distinct gain modulation properties through a simple change in parameters, we show that coding properties of both these models quantitatively satisfy the predicted relationships. Our results describe how both variance-dependent gain modulation and adaptive neural computation result from intrinsic nonlinearity.Comment: 24 pages, 4 figures, 1 supporting informatio