Stochastic modelling of 3D fiber structures imaged with X-ray microtomography

Many products incorporate into their design fibrous material with particular levels of permeability as a way to control the retention and flow of liquid. The production and experimental testing of these materials can be expensive and time consuming, particularly if it needs to be optimised to a desired level of absorbency. We consider a parametric virtual fiber model as a replacement for the real material to facilitate studying the relationship between structure and properties in a cheaper and more convenient manner. 3D image data sets of a sample fibrous material are obtained using X-ray microtomography and the individual fibers isolated. The segmented fibers are used to estimate the parameters of a 3D stochastic model for generating softcore virtual fiber structures. We use several spatial measures to show the consistency between the real and virtual structures, and demonstrate with lattice Boltzmann simulations that our virtual structure has good agreement with respect to the permeability of the physical material

Radiographic progression in PsA Personal non-commercial use only

ABSTRACT. Objective. To describe early radiographic findings in patients from the Swedish psoriatic arthritis (SwePsA) registry, progression of destruction, correlations with clinical disease variables, and predictors of destruction. Methods. Hand and foot radiographs were available for 72 of 197 SwePsA patients followed for 5 years. Clinical data were collected according to the SwePsA protocol. Results. Disease characteristics and clinical improvement were similar in men and women. Radiographic abnormalities were more pronounced in men. Total Wassenberg radiographic score at baseline was 0 in 45% of men and 51% of women. One man and one woman had a score > 10. At 5 years, total score was 0 in 14% of men and 40% of women (p = 0.018); 17% of men and 7% of women had scores > 10. Mean total scores for men and women had increased. Baseline erythrocyte sedimentation rate was associated with baseline total radiographic score. In men, swollen joint count was positively, and in women tender joint count negatively, correlated to total radiographic score. After 5 years, only male scores, mainly hand scores, significantly correlated with 28-joint Disease Activity Score and Disease Activity Index for Psoriatic Arthritis scores, swollen joint count, and dactylitis. Achieving remission or minimal disease activity after 5 years protected against structural damage, mainly in men. Conclusion. Radiographic progression in early PsA was generally slow but substantial. Male sex appears to be a risk factor for early radiographic damage while the presence of baseline radiographic damage and dactylitis developing during followup seem to predict further destruction. Hand and foot radiograph scoring cannot be substituted with clinical signs. (J Rheumatol First Release October 15 2015; doi:10.3899/jrheum.150165

PoGOLite - A High Sensitivity Balloon-Borne Soft Gamma-ray Polarimeter

We describe a new balloon-borne instrument (PoGOLite) capable of detecting 10% polarisation from 200mCrab point-like sources between 25 and 80keV in one 6 hour flight. Polarisation measurements in the soft gamma-ray band are expected to provide a powerful probe into high-energy emission mechanisms as well as the distribution of magnetic fields, radiation fields and interstellar matter. At present, only exploratory polarisation measurements have been carried out in the soft gamma-ray band. Reduction of the large background produced by cosmic-ray particles has been the biggest challenge. PoGOLite uses Compton scattering and photo-absorption in an array of 217 well-type phoswich detector cells made of plastic and BGO scintillators surrounded by a BGO anticoincidence shield and a thick polyethylene neutron shield. The narrow FOV (1.25msr) obtained with well-type phoswich detector technology and the use of thick background shields enhance the detected S/N ratio. Event selections based on recorded phototube waveforms and Compton kinematics reduce the background to that expected for a 40-100mCrab source between 25 and 50keV. A 6 hour observation on the Crab will differentiate between the Polar Cap/Slot Gap, Outer Gap, and Caustic models with greater than 5 sigma; and also cleanly identify the Compton reflection component in the Cygnus X-1 hard state. The first flight is planned for 2010 and long-duration flights from Sweden to Northern Canada are foreseen thereafter.Comment: 11 pages, 11 figures, 2 table

Genetic risk and a primary role for cell-mediated immune mechanisms in multiple sclerosis.

Multiple sclerosis is a common disease of the central nervous system in which the interplay between inflammatory and neurodegenerative processes typically results in intermittent neurological disturbance followed by progressive accumulation of disability. Epidemiological studies have shown that genetic factors are primarily responsible for the substantially increased frequency of the disease seen in the relatives of affected individuals, and systematic attempts to identify linkage in multiplex families have confirmed that variation within the major histocompatibility complex (MHC) exerts the greatest individual effect on risk. Modestly powered genome-wide association studies (GWAS) have enabled more than 20 additional risk loci to be identified and have shown that multiple variants exerting modest individual effects have a key role in disease susceptibility. Most of the genetic architecture underlying susceptibility to the disease remains to be defined and is anticipated to require the analysis of sample sizes that are beyond the numbers currently available to individual research groups. In a collaborative GWAS involving 9,772 cases of European descent collected by 23 research groups working in 15 different countries, we have replicated almost all of the previously suggested associations and identified at least a further 29 novel susceptibility loci. Within the MHC we have refined the identity of the HLA-DRB1 risk alleles and confirmed that variation in the HLA-A gene underlies the independent protective effect attributable to the class I region. Immunologically relevant genes are significantly overrepresented among those mapping close to the identified loci and particularly implicate T-helper-cell differentiation in the pathogenesis of multiple sclerosis

Controller design for linear systems subject to actuator saturation.

A new controller design methodology for single input linear systems subject to input constraints is presented. The design procedure results in high performance in terms of settling time, while being easy to design and implement. To achieve this high performance the actuator constraints are incorporated directly into the design and Lyapunov stability theory is used to guarantee stability in the presence of saturation. Model uncertainties such as parameter uncertainty, unmodeled dynamics and measurement noise can be incorporated into the design to make the design robust. The method is based on two key concepts. First a method of scaling the settling time for the linear closed loop response using Linear Quadratic Regulator design is developed. The developed method uses the control weight, R, as a scalar design parameter, while the weight on the states Q, are adjusted as a function of R to maintain the shape (e.g., overshoot) of the response. The second concept is the use of a guaranteed domain of attraction (GDA), that is obtained using Lyapunov stability theory. The GDA can be made robust to disturbances and parameter uncertainties, and it allows for saturation so that the controller can take advantage of the available control authority. The performance can then be maximized (i.e., settling time minimized) using the method of scaling subject to the constraint imposed by the condition that all initial conditions should be contained inside the GDA. In addition to the constraint imposed by saturation there will be additional constraints imposed on the scaling parameter by unmodeled dynamics and measurement noise. The design method has been successfully applied to the position control of a single degree of freedom robot arm in a laboratory experiment. It has also been applied to a number of other examples where the performance has been evaluated using simulations rather than real experiments. The stability results assume full state feedback, however both simulation results and experimental results indicate that it can be successfully used for output feedback of single input single output systems by designing a state observer.Ph.D.Applied SciencesMechanical engineeringUniversity of Michigan, Horace H. Rackham School of Graduate Studieshttp://deepblue.lib.umich.edu/bitstream/2027.42/132185/2/9959806.pd