118 research outputs found
Method for decomposition of the metallorganic matter of graptolite-argillite by microbial consortium
Microscopic theory of network glasses
A molecular theory of the glass transition of network forming liquids is
developed using a combination of self-consistent phonon and liquid state
approaches. Both the dynamical transition and the entropy crisis characteristic
of random first order transitions are mapped out as a function of the degree of
bonding and the density. Using a scaling relation for a soft-core model to
crudely translate the densities into temperatures, the theory predicts that the
ratio of the dynamical transition temperature to the laboratory transition
temperature rises as the degree of bonding increases, while the Kauzmann
temperature falls relative to the laboratory transition. These results indicate
why highly coordinated liquids should be "strong" while van der Waals liquids
without coordination are "fragile".Comment: slightly revised version that has been accepted for publication in
Phys. Rev. Let
Measuring fluorescence decay times by phase-shift and modulation techniques using the high harmonic content of pulsed light sources
Neural Predictors of Gait Stability When Walking Freely in the Real-World.
Background: Gait impairments during real-world locomotion are common in neurological diseases. However, very little is currently known about the neural correlates of walking in the real world and on which regions of the brain are involved in regulating gait stability and performance. As a first step to understanding how neural control of gait may be impaired in neurological conditions such as Parkinson’s disease, we investigated how regional brain activation might predict walking performance in the urban environment and whilst engaging with secondary tasks in healthy subjects.
Methods: We recorded gait characteristics including trunk acceleration and brain activation in fourteen healthy young subjects whilst they walked around the university campus freely (single task), while conversing with the experimenter and while texting with their smartphone. Neural spectral power density (PSD) was evaluated in three brain regions of interest, namely the pre-frontal cortex (PFC) and bilateral posterior parietal cortex (right/left PPC). We hypothesized that specific regional neural activation would predict trunk acceleration data obtained during the different walking conditions.
Results: Vertical trunk acceleration was predicted by gait velocity and left PPC theta (4-7 Hz) band PSD in single-task walking (R-squared = 0.725, p = 0.001) and by gait velocity and left PPC alpha (8-12 Hz) band PSD in walking while conversing (R-squared = 0.727, p = 0.001). Medio-lateral trunk acceleration was predicted by left PPC beta (15-25 Hz) band PSD when walking while texting (R-squared = 0.434, p = 0.010).
Conclusions: We suggest that the left PPC may be involved in the processes of sensorimotor integration and gait control during walking in real-world conditions. Frequency-specific coding was operative in different dual tasks and may be developed as biomarkers of gait deficits in neurological conditions during performance of these types of, now commonly undertaken, dual tasks
Reduced order models for closed loop control: comparison between POD, BPOD, and global modes
Linear Quadratic Gaussian (LQG) control is a promising tool to control flows. Initially developed for systems of moderate size, it is not directly applicable to fluid mechanics problems, requiring a reduced model. Three popular ways of reducing the system will be presented and their ability to control the global instability of an incompressible cavity flow will be studied. A comparison between reduced models based on global modes, Proper Orthogonal Decomposition (POD) modes and Balanced POD (BPOD) modes permits to discuss the relevant quantities to be captured by the reduced model to insure a successful control
Closed-loop control using reduced-order models based on global modes : Reynolds number effects
International audienc
Reduced-order models for control design using system identification
International audienc
- …