Motor Adaptation and Automaticity in People with Parkinson’s Disease and Freezing of Gait

Parkinson’s disease (PD) is a progressive neurodegenerative disorder characterized by cell death in the substantia nigra pars compacta, resulting in motor symptoms of tremor, rigidity, bradykinesia and gait impairment. Freezing of gait (FOG) is one serious gait disturbance, characterized by a transient inability produce effective stepping during walking and turning, and affects roughly half of people with PD at some point during their disease. Despite the ongoing research on the behavioral, neurological, and cognitive characteristics of people with FOG (PD+FOG), the mechanisms underlying freezing are still poorly understood. The overall aim of this work was to further investigate motor behavior in PD+FOG to provide insight into its potential mechanisms. The first experiment investigated possible cerebellar dysfunction in PD+FOG by examining visuomotor adaptation, a well-known cerebellar-dependent process. We found that there were no differences in reaching or walking adaptation between freezers and non-freezers, however non-freezers exhibited smaller after-effects compared to freezers and healthy older adults. Furthermore, adults with PD, as well as older and younger adults adapt walking patterns slower than reaching patterns, indicating walking is a more complex task requiring greater sensorimotor processing to modify. Overall, this study showed that cerebellar function, in terms of its role in sensorimotor adaptation, is relatively preserved in PD and FOG. In the second experiment, we examined motor automaticity of saccadic eye movements and reaching. Reduced automaticity is a likely motor-cognitive mechanism that contributes to freezing behavior, however automaticity in other motor systems has yet to fully described. Using an anti-saccade task, we found that PD+FOG participants were slower to respond to both automatic and non-automatic eye movements, and had increased saccade velocity variability compared to PD-FOG and controls. These changes were not related to disease severity or general cognition. In contrast, both PD groups were slower to execute (greater latency) reaching movements during both pro- and anti-reaching, but no freezer non-freezer differences were noted. PD+FOG reached with lower peak velocity compared to older adults but were similar to PD-FOG during both automatic and non-automatic conditions. These data show that changes in automaticity and control exist outside locomotor centers, indicating freezing may be a global motor disturbance. Altogether, the work in this dissertation furthers our knowledge on motor control in PD+FOG and provides additional evidence that freezing affects non-gait motor function

Theory of rigid-plane phonon modes in layered crystals

The lattice dynamics of low-frequency rigid-plane modes in metallic (graphene multilayers, GML) and in insulating (hexagonal boron-nitride multilayers, BNML) layered crystals is investigated. The frequencies of shearing and compression (stretching) modes depend on the layer number {\EuScript N} and are presented in the form of fan diagrams. The results for GML and BNML are very similar. In both cases only the interactions (van der Waals and Coulomb) between nearest-neighbor planes are effective, while the interactions between more distant planes are screened. A comparison with recent Raman scattering results on low-frequency shear modes in GML [Tan {\it et al.}, arXiv:1106.1146v1 (2011)] is made. Relations with the low-lying rigid-plane phonon dispersions in the bulk materials are established. Master curves which connect the fan diagram frequencies for any given {\EuScript N} are derived. Static and dynamic thermal correlation functions for rigid-layer shear and compression modes are calculated. The results might be of use for the interpretation of friction force experiments on multilayer crystals

Piezoresponse force microscopy for polarity imaging of GaN

The polarity distribution of GaN based lateral polarity heterostructures is investigated by piezoresponse force microscopy (PFM). Simultaneous imaging of surface morphology, as well as the phase and magnitude of the piezoelectric response, is performed by PFM on a GaN film with patterned polarities on a c-Al2O3 substrate. We demonstrate that the polarity distribution of GaN based lateral polarity heterostructures can be deduced from the phase image of the piezoresponse with nanometer scale spatial resolution

Investigation of work function and chemical composition of thin films of borides and nitrides

Thin films of various borides, nitrides, and barium fluorides were tentatively deposited by pulsed laser deposition and by magnetron sputtering in order to develop the components of thermionic-photovoltaic devices for the high-temperature thermal to electrical conversion by solid state. To improve the device performance, the materials characterized by a low work function were selected. In the present work, the chemical composition and work function of obtained films were investigated by X-ray photoelectron spectroscopy and ultraviolet photoelectron spectroscopy techniques. The values of work function were determined from the cut-off in the He I valence band spectra. Different films were compared and estimated on the basis of X-ray photoelectron spectroscopy and ultraviolet photoelectron spectroscopy results

Sexual dimorphism in myocardial acylcarnitine and triglyceride metabolism

Figure S1. Concentrations of non-esterified fatty acid moieties in NOD and Wistar rats by sex. (PPTX 163 kb

A Multivariate Water Quality Index for Use in Management of a Wildland Watershed

Executive Summary: Summary: Multivariate statistical techniques were used to define a method for establishing a water quality index (WQI) for use in protecting the stream environment in a high mountain watershed. The purpose of the WQI was to aggregate water quality parameters in such a way that the effects of low level increments in mining, grazing, logging and other activities could be related to a change in the value of a single entity, aquatic environmental aquality, in a linear programming (LP) management model. Several data aggregation methods were explored, using water quality data collected over 5 years (1975-1979) by the USDA Forest Service in the upper Blackfoot River watershed in southeastern Idaho. The WQIs thus generated were compared with indices of benthic invertebrate community composition as determined from samples collected late in the summer of 1981. Community composition indices were based on emergent community properties (biomass and diversity) and on taxonomic composition as revealed by principal componenets analysis. Significant results of the study include the following: 1. Existing determinisitic general purpose WQIs (such as the National Sanitation Foundation Index) proved useless for guidance in protecting water quality in these high mountain watersheds, because stream water quality often remains excellent by drinking water standards, even though subtle changes in water quality parameters may significantly affect instream habitat. 2. An increasing scale, multivariate statistical WQI was created for the study area using 5-year May-October averages of ten water quality variables in eight streams. Removal of some streams from the data set, as well as aggregating or replacing some variables, did not significantly alter the rank order of the stream WQI values. 3. Changes in the calculation time step to 5-year bimonthly (May-June, July-August, September-October) or monthly averages, or to annual averages for four water years, provided little additional information, and resulting in decreasing sensitivity to changes in water quality variables because of larger standard deviations in the data sets. 4. The WQI was composed of four principal components that were easily interpretable as common factors (e.g., nutrient sources, suspended sediment sources, groundwater, and discharge) that affected groups of variables. These principal components, or subindices, were positively correlated with the presence of certain benthic invertebrate taxa or groups of taxa. 5. Cluster analysis was useful in reducing the dimensionality of water quality data and in revealing relationships among invertebrate communities (Q-type analysis). However, R-type cluster analysis of the study streams showed no similar groups of streams based on water quality variables. 6. The WQI was highly negatively correlated (r^2=0.93) with benthic invertebrate standing stock biomass, a relationship described by a decreasing power function. There was no apparent relationship between benthic invertebrate diversity and the WQI values. 7. The WQI-biomass relationship may be useful in setting a constraint value on the WQI in the LP model. Additional data and information from more sites should be collected and analyzed, however, to stengthen the confidence in the correlation, and to establish causality between the variables contributing strongly to the WQI and community biomass. 8. The multivariate WQI was found to be heavily influenced by the relative standard deviations of the variables used to form the index. Inclusion of only similar (pristine) streams in a baseline data set will result in a lower standard deviation for each variable. The result is higher sensitiviely to a given polluting factor than will be found in a mixed group of streams in which some are already impacted by anthropogenic activities. 9. High standard deviations for individual variables may mask relationships between environmentally significant parameters and biological communities. 10. Multivariate WQI indexing provides valuable insights into the relationship between water quality and biological community composition, even if appliaction of the WQIs in predictive settings is premature or ultimately proves to be unacceptable. Suggestions for Further Research: 1. Collect additional invertebrate data at other seasons and on Upper Angus and Mabie Creeks in order to reinforce or refine the relationships reported here. 2. Collect more detailed habitat data in order to elucidate the relative importance of water quality and physical habitat in controlling benthic community composition. Artificaial substrates may be useful in reducing physical habitat dissimilarity in order to focus on water quality effects. 3. Update the WQI using 1980-1982 data from the Forest Service and look for recent trends that would reinforce or alter the conclusions based on the older data. 4. Examine the use of standardized extreme values, rather than standardized means, to create a WQI. 5. Employ cannonical correlation as a means of further elucidating water quality-physical substrate-benthic community relationships. 6. Monitor changes in the WQI and benthic invertebrate community in one of the study streams in response to changing management practices (e.g., erosion control or additional phosphate mining). 7. Investigate the effects of a proposed change in management practice on a WQI using Monte-Carlo analysis to account for simultaneous changes in many variables. 8. Investigate the response of the invertebrates in principal components 1 and 4 to nutrients and suspended sediments in controlled (artificial) ecosystems to test their suitability as water quality indicators in the study area