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Search Results: 1 - 10 of 410702 matches for " Stephen M Cain "
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Locomotor adaptation to a powered ankle-foot orthosis depends on control method
Stephen M Cain, Keith E Gordon, Daniel P Ferris
Journal of NeuroEngineering and Rehabilitation , 2007, DOI: 10.1186/1743-0003-4-48
Abstract: Subjects walked on a treadmill for two thirty-minute sessions spaced three days apart under either footswitch control (n = 6) or myoelectric control (n = 6). We recorded lower limb electromyography (EMG), joint kinematics, and orthosis kinetics. We compared stance phase EMG amplitudes, correlation of joint angle patterns, and mechanical work performed by the powered orthosis between the two controllers over time.During steady state at the end of the second session, subjects using proportional myoelectric control had much lower soleus and gastrocnemius activation than the subjects using footswitch control. The substantial decrease in triceps surae recruitment allowed the proportional myoelectric control subjects to walk with ankle kinematics close to normal and reduce negative work performed by the orthosis. The footswitch control subjects walked with substantially perturbed ankle kinematics and performed more negative work with the orthosis.These results provide evidence that the choice of orthosis control method can greatly alter how humans adapt to powered orthosis assistance during walking. Specifically, proportional myoelectric control results in larger reductions in muscle activation and gait kinematics more similar to normal compared to footswitch control.Advancements in robotic technology have enabled several research groups around the world to build working robotic exoskeletons for assisting human locomotion [1-8]. The exoskeletons have a range of intended uses including enhancing human performance in healthy individuals, replacing motor capabilities in disabled individuals, and aiding in neurological rehabilitation. In each case, improvements in computer processing, energy efficiency, and sensors and actuators are allowing devices to far surpass previous expectations.In order for robotic exoskeletons to better assist humans, it is imperative to determine how humans respond to mechanical assistance given by exoskeletons. Most of the published research has fo
Development of a Standardized Screening Rule for Tuberculosis in People Living with HIV in Resource-Constrained Settings: Individual Participant Data Meta-analysis of Observational Studies
Haileyesus Getahun ,Wanitchaya Kittikraisak,Charles M. Heilig,Elizabeth L. Corbett,Helen Ayles,Kevin P. Cain,Alison D. Grant,Gavin J. Churchyard,Michael Kimerling,Sarita Shah,Stephen D. Lawn,Robin Wood,Gary Maartens,Reuben Granich,Anand A. Date,Jay K. Varma
PLOS Medicine , 2011, DOI: 10.1371/journal.pmed.1000391
Abstract: Background The World Health Organization recommends the screening of all people living with HIV for tuberculosis (TB) disease, followed by TB treatment, or isoniazid preventive therapy (IPT) when TB is excluded. However, the difficulty of reliably excluding TB disease has severely limited TB screening and IPT uptake in resource-limited settings. We conducted an individual participant data meta-analysis of primary studies, aiming to identify a sensitive TB screening rule. Methods and Findings We identified 12 studies that had systematically collected sputum specimens regardless of signs or symptoms, at least one mycobacterial culture, clinical symptoms, and HIV and TB disease status. Bivariate random-effects meta-analysis and the hierarchical summary relative operating characteristic curves were used to evaluate the screening performance of all combinations of variables of interest. TB disease was diagnosed in 557 (5.8%) of 9,626 people living with HIV. The primary analysis included 8,148 people living with HIV who could be evaluated on five symptoms from nine of the 12 studies. The median age was 34 years. The best performing rule was the presence of any one of: current cough (any duration), fever, night sweats, or weight loss. The overall sensitivity of this rule was 78.9% (95% confidence interval [CI] 58.3%–90.9%) and specificity was 49.6% (95% CI 29.2%–70.1%). Its sensitivity increased to 90.1% (95% CI 76.3%–96.2%) among participants selected from clinical settings and to 88.0% (95% CI 76.1%–94.4%) among those who were not previously screened for TB. Negative predictive value was 97.7% (95% CI 97.4%–98.0%) and 90.0% (95% CI 88.6%–91.3%) at 5% and 20% prevalence of TB among people living with HIV, respectively. Abnormal chest radiographic findings increased the sensitivity of the rule by 11.7% (90.6% versus 78.9%) with a reduction of specificity by 10.7% (49.6% versus 38.9%). Conclusions Absence of all of current cough, fever, night sweats, and weight loss can identify a subset of people living with HIV who have a very low probability of having TB disease. A simplified screening rule using any one of these symptoms can be used in resource-constrained settings to identify people living with HIV in need of further diagnostic assessment for TB. Use of this algorithm should result in earlier TB diagnosis and treatment, and should allow for substantial scale-up of IPT. Please see later in the article for the Editors' Summary
Inferring Latent Structure From Mixed Real and Categorical Relational Data
Esther Salazar,Matthew Cain,Elise Darling,Stephen Mitroff,Lawrence Carin
Computer Science , 2012,
Abstract: We consider analysis of relational data (a matrix), in which the rows correspond to subjects (e.g., people) and the columns correspond to attributes. The elements of the matrix may be a mix of real and categorical. Each subject and attribute is characterized by a latent binary feature vector, and an inferred matrix maps each row-column pair of binary feature vectors to an observed matrix element. The latent binary features of the rows are modeled via a multivariate Gaussian distribution with low-rank covariance matrix, and the Gaussian random variables are mapped to latent binary features via a probit link. The same type construction is applied jointly to the columns. The model infers latent, low-dimensional binary features associated with each row and each column, as well correlation structure between all rows and between all columns.
Magnetic perturbations seen by CHAMP and evaluated using the TIE-GCM
D. T. Mozzoni, M. Mandea,J. Cain
Annales Geophysicae (ANGEO) , 2007,
Abstract: The Thermosphere-Ionosphere Electrodynamics General Circulation Model (TIE-GCM) is a self-consistent, global, atmospheric model that can be used to estimate magnetic perturbations at satellite altitude. These computed perturbations can then be compared with the magnetic vector data provided by low-earth orbiting satellites. In this initial study, the quietest day of each month from 2001–2005 was selected for comparison. CHAMP magnetic vector residuals were computed for these intervals using the CHAOS model to remove core and crustal geomagnetic contributions. Under various input parameters, the TIE-GCM predictions were compared with the CHAMP residuals on an orbit by orbit basis. Initial results demonstrate a reasonable agreement between the TIE-GCM estimates and the CHAMP residuals in non-polar, dayside regions (±50° magnetic latitude) where both are able to resolve the Equatorial Electro-Jet (EEJ) and solar quiet (Sq) current systems. Although no clear component or temporal correlation was discerned, evidence showing the decrease in residual comparisons presents the possibility of using the TIE-GCM to pre-process geomagnetic data for main field modeling purposes.
Quantification of chemical and physical processes influencing ozone during long-range transport using a trajectory ensemble
M. Cain, J. Methven,E. J. Highwood
Atmospheric Chemistry and Physics (ACP) & Discussions (ACPD) , 2012,
Abstract: During long-range transport, many distinct processes – including photochemistry, deposition, emissions and mixing – contribute to the transformation of air mass composition. Partitioning the effects of different processes can be useful when considering the sensitivity of chemical transformation to, for example, a changing environment or anthropogenic influence. However, transformation is not observed directly, since mixing ratios are measured, and models must be used to relate changes to processes. Here, four cases from the ITCT-Lagrangian 2004 experiment are studied. In each case, aircraft intercepted a distinct air mass several times during transport over the North Atlantic, providing a unique dataset and quantifying the net changes in composition from all processes. A new framework is presented to deconstruct the change in O3 mixing ratio (Δ O3) into its component processes, which were not measured directly, taking into account the uncertainty in measurements, initial air mass variability and its time evolution. The results show that the net chemical processing (Δ O3chem) over the whole simulation is greater than net physical processing (Δ O3phys) in all cases. This is in part explained by cancellation effects associated with mixing. In contrast, each case is in a regime of either net photochemical destruction (lower tropospheric transport) or production (an upper tropospheric biomass burning case). However, physical processes influence O3 indirectly through addition or removal of precursor gases, so that changes to physical parameters in a model can have a larger effect on Δ O3chem than Δ O3phys. Despite its smaller magnitude, the physical processing distinguishes the lower tropospheric export cases, since the net photochemical O3 change is 5 ppbv per day in all three cases. Processing is quantified using a Lagrangian photochemical model with a novel method for simulating mixing through an ensemble of trajectories and a background profile that evolves with them. The model is able to simulate the magnitude and variability of the observations (of O3, CO, NOy and some hydrocarbons) and is consistent with the time-average OH following air-masses inferred from hydrocarbon measurements alone (by Arnold et al., 2007). Therefore, it is a useful new method to simulate air mass evolution and variability, and its sensitivity to process parameters.
A Study of School Size among Alabama’s Public High Schools
Ronald A. Lindahl,Patrick M. Cain, Sr.
International Journal of Education Policy and Leadership , 2012,
Abstract: The purpose of this study was to examine the relationship between the size of Alabama’s public high schools, selected school quality and financial indicators, and their students’ performance on standardized exams. When the socioeconomic level of the student bodies is held constant, the size of high schools in Alabama has relatively little relationship with 11th grade student (both regular and special education) performance on the reading and math portions of the Alabama High School Graduation Exam (AHSGE). High schools’ average daily attendance rates and pupil-to-computer (and computer with Internet connections) ratios do not vary in accordance with school size. Higher percentages of highly qualified teachers are found in Alabama’s largest high schools. There was very little difference in the percentage of teachers with a master’s degree or above across school size categories. Very little difference exists across size categories in regard to mean expenditures per pupil (range = $7,322 to $7,829). However, districts of the large high schools exert over twice the effort of those with small high schools (3.2 mills to 1.5 mills) and approximately 50 percent greater local effort than the districts of the medium-size high schools.
Phase diagram of the three-dimensional Anderson model of localization with random hopping
P. Cain,R. A. Roemer,M. Schreiber
Physics , 1999,
Abstract: We examine the localization properties of the three-dimensional (3D) Anderson Hamiltonian with off-diagonal disorder using the transfer-matrix method (TMM) and finite-size scaling (FSS). The nearest-neighbor hopping elements are chosen randomly according to $t_{ij} \in [c-1/2, c + 1/2]$. We find that the off-diagonal disorder is not strong enough to localize all states in the spectrum in contradistinction to the usual case of diagonal disorder. Thus for any off-diagonal disorder, there exist extended states and, consequently, the TMM converges very slowly. From the TMM results we compute critical exponents of the metal-insulator transitions (MIT), the mobility edge $E_c$, and study the energy-disorder phase diagram.
A Lagrangian model of air-mass photochemistry and mixing using a trajectory ensemble: the Cambridge Tropospheric Trajectory model of Chemistry And Transport (CiTTyCAT) version 4.2
T. A. M. Pugh,M. Cain,J. Methven,O. Wild
Geoscientific Model Development Discussions , 2011, DOI: 10.5194/gmdd-4-2469-2011
Abstract: A Lagrangian model of photochemistry and mixing is described (CiTTyCAT, stemming from the Cambridge Tropospheric Trajectory model of Chemistry And Transport), which is suitable for transport and chemistry studies throughout the troposphere. Over the last five years, the model has been developed in parallel at several different institutions and here those developments have been incorporated into one "community" model and documented for the first time. The key photochemical developments include a new scheme for biogenic volatile organic compounds and updated emissions schemes. The key physical development is to evolve composition following an ensemble of trajectories within neighbouring air-masses, including a simple scheme for mixing between them via an evolving "background profile", both within the boundary layer and free troposphere. The model runs along trajectories pre-calculated using winds and temperature from meteorological analyses. In addition, boundary layer height and precipitation rates, output from the analysis model, are interpolated to trajectory points and used as inputs to the mixing and wet deposition schemes. The model is most suitable in regimes when the effects of small-scale turbulent mixing are slow relative to advection by the resolved winds so that coherent air-masses form with distinct composition and strong gradients between them. Such air-masses can persist for many days while stretching, folding and thinning. Lagrangian models offer a useful framework for picking apart the processes of air-mass evolution over inter-continental distances, without being hindered by the numerical diffusion inherent to global Eulerian models. The model, including different box and trajectory modes, is described and some output for each of the modes is presented for evaluation. The model is available for download from a Subversion-controlled repository by contacting the corresponding authors.
Integer quantum Hall transition in the presence of a long-range-correlated quenched disorder
P. Cain,M. E. Raikh,R. A. Roemer,M. Schreiber
Physics , 2001, DOI: 10.1103/PhysRevB.64.235326
Abstract: We theoretically study the effect of long-ranged inhomogeneities on the critical properties of the integer quantum Hall transition. For this purpose we employ the real-space renormalization-group (RG) approach to the network model of the transition. We start by testing the accuracy of the RG approach in the absence of inhomogeneities, and infer the correlation length exponent nu=2.39 from a broad conductance distribution. We then incorporate macroscopic inhomogeneities into the RG procedure. Inhomogeneities are modeled by a smooth random potential with a correlator which falls off with distance as a power law, r^{-alpha}. Similar to the classical percolation, we observe an enhancement of nu with decreasing alpha. Although the attainable system sizes are large, they do not allow one to unambiguously identify a cusp in the nu(alpha) dependence at alpha_c=2/nu, as might be expected from the extended Harris criterion. We argue that the fundamental obstacle for the numerical detection of a cusp in the quantum percolation is the implicit randomness in the Aharonov-Bohm phases of the wave functions. This randomness emulates the presence of a short-range disorder alongside the smooth potential.
Personality Fit and Positive Interventions: Extraverted and Introverted Individuals Benefit from Different Happiness Increasing Strategies  [PDF]
Stephen M. Schueller
Psychology (PSYCH) , 2012, DOI: 10.4236/psych.2012.312A172

The current investigation examined if introverts and extraverts benefit differentially from specific positive psychology interventions. Across two studies participants completed various interventions: three good things, gratitude visit, savoring, signature strength, and active-constructive responding. In study 1, each participant (N = 150) completed 1 of the 5 interventions over a one-week period. All 5 interventions led to increases in happiness, t(144) = 3.80, p < .001, and reductions in depressive symptoms t(144) = 5.20, p <.001. Neither exercise was more beneficial overall. The results of an ANCOVA (with baseline levels as a covariate) found that the interaction term for extraversion and condition was at a trend level F(4, 139) = 2.36, p = .056 and planned contrast analyses supported a pattern of person-activity fit. Extraverts benefited more from the gratitude visit and savoring exercises, whereas introverts benefited more from the active-constructive responding, signature strength, and three good things exercises. In study 2, participants (N = 85) were assigned to one of three groups: the gratitude visit performed either in-person, over the phone, or via mail. Participants completed each exercise over a one-week period. No differential efficacy was found for the 3 interventions, F(1,

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