The Effect of Vibrotactile Feedback on Healthy People and People with Vestibular Disorders during Dual-task Conditions

Vibrotactile feedback (VTF) has been shown to improve balance performance in healthy people and people with vestibular disorders in a single-task experimental condition. However, typical balance activities occur in a multi-task environment. Dual-task performance can degrade with age and in people with vestibular disorders. It is unclear if the ability to use VTF might be affected by dual-task conditions in different age groups and people with vestibular disorders. The purposes of this dissertation are to investigate in healthy young and older adults, and people with vestibular disorders: 1) balance performance in a dual-task paradigm under various sensory conditions while using VTF, 2) reaction time during dual-task performance under different sensory conditions while using VTF, and 3) the effect of testing duration and visit on VTF use. Three study visits were included in this dissertation study: one screening visit and two experimental visits. Twenty younger and twenty older subjects were recruited in the first study to determine if VTF was affected by age. Seven people with unilateral vestibular hypofunction (UVH) and seven age-matched controls were recruited in the second study to investigate the effect of vestibular dysfunction. The results showed that young and older adults use VTF differently, depending on the underlying sensory integration balance task. Older adults increased postural sway during fixed platform conditions, but both young and older adults decreased postural sway during sway-referenced platform conditions. Reaction times on the secondary cognitive tasks increased more while using the VTF in older adults compared with young adults. This finding suggested that using VTF requires greater attention in older adults. The trial duration and visit also affected postural sway performance while VTF was applied. Similar postural sway results were found when comparing people with UVH and age-matched controls. However, no group difference was found between people with UVH and age-matched controls in the magnitude of postural sway, which suggested that people with UVH were able to use VTF under dual-task conditions similar to normal adults. Our data also indicated that people with UVH require more attentional resources to perform secondary cognitive tasks while using VTF

Functional silica-encapsulated photoactive nanocrystals

Silica-based nanocomposites with core/shell configurations have diverse functionalities and applications. We present the preparation and characterization of Co3O4/porous-SiO2 nanocomposites with the examination of their catalytic activity in the dye sensitized water oxidation reaction; a generalized methodology to prepare metal chalcogenides/pnictides with one-pot and one-step manner; the synthesis of Au/Ag/SiO2 multishell nanorods and their application as imaging probes in single particle tracking experiments. Silica supported Co3O4 nanocomposites have recently drawn much attention due to their high catalytic ability in the water oxidation reaction. We have synthesized several Co3O4/porous silica nanocomposites to study the synergetic effects of the catalyst microstructure and local environment on water oxidation catalytic activity. The catalytic activity study of Co3O4/porous SiO2 core/shell nanoparticles on oxygen evolution reaction reveals that the catalyst with a 19.8 ± 1.4 nm shell has superior activity than other catalysts due to two possible factors: the increased local concentration of Ru(bpy)32+ near the active Co3O4 and/or the reduced reorganization energy due to the lower dielectric constant. However, further increasing shell thicknesses resulted in the deterioration of catalytic activity possibly due to slower diffusion of reactants. In the Co3O4/SBA-15 system, the unmodified sample is more active than the modified ones. This is could be due to local surface permittivities of surface-modified composites (e.g., −SiPh and −SiMe3) being lower than those of the unmodified composites. Additionally, the loss of possible Ru(bpy)32+ binding sites and pore blocking after surface modification may cause the loss of reactivity. Late transition metal chalcogenides and pnictides are popular materials for their unique physical properties and various applications, such as hydroprocessing and water electrolysis catalysts. We demonstrate a generalized route using trimethylsilyl reagents (TMSxE) to convert metal oxides into metal chalcogenides and pnictides through deoxysilylation reactions. The resulting nanocrystals are hollow (vesicle-like) and are surrounded by amorphous silica layer. The nonequivalent diffusion of ions induces the void formation inside the nanocrystals (nanoscale Kirkendall effect); simultaneous decomposition of the TMSxE produces silica layers that can serve as the protection layer preventing particle agglomeration and thus increasing both the robustness and thermal stability of the composites. Plasmonic metal nanocrystals are a type of label/probe in optical applications, such as bioimaging labels, biochemical sensors, photothermal therapy, surface enhanced Raman spectroscopy and surface plasmon enhanced solar cells. Single particle orientation and rotational tracking (SPORT) is one of the techniques that can explicit the biophysics in biological systems. We present the fabrication of Au/Ag/SiO2 nanorods with well-controlled size, composition and shape for SPORT experiments. With the enhancement of the longitudinal dipolar LSPR due to the secondary silver coating, these multishell nanorods are able to provide sufficient sensitivity for detection at temporal resolution in millisecond range on both synthetic lipid bilayers and live cell membranes

catena-Poly[[diaqua­magnesium(II)]-bis­(μ-5-ammonio­isophthalato-κ2 O 1:O 3)]

In the title compound, [Mg(C8H6NO4)2(H2O)2]n, the MgII ion lies on a twofold roatation axis and is coordinated in a slightly distorted octa­hedral environment. Pairs of bridging ammonium­isophthalate ligands connect symmetry-related MgII ions, forming chains along [010]. In the crystal, inter­molecular O—H⋯O and N—H⋯O hydrogen bonds link these chains into a three-dimensional network. The centroids of pairs of symmetry-related benzene rings within a chain are separated by 3.5707 (12) Å

Age Effects on Spatiotemporal Dynamics of Response Inhibition: An MEG Study

Inhibition, the ability to suppress irrelevant information, thoughts or movements, is crucial for humans to perform context-appropriate behaviors. It was suggested that declined cognitive performance in older adults might be attributed to inhibitory deficiencies. Although previous studies have shown an age-associated reduction in inhibitory ability, the understanding regarding its cortical spatiotemporal maps remained limited. Thus, we used a whole-head magnetoencephalography (MEG) to elucidate the age effects on response inhibition, and to explore the brain activation differences in high- and low-performing seniors. We recruited 22 younger and 22 older adults to participate in the visual Go/No-go task. Both behavioral performance and neuromagnetic responses to No-go stimuli were analyzed. The behavioral results showed that the older adults made more false alarm (FA) errors than the younger adults did. The MEG results showed that the seniors exhibited declined cortical activities in middle temporal gyrus (MTG) and delayed activation in MTG, prefrontal cortex (PFC) and pre-supplementary motor area (pre-SMA). Furthermore, among the older adults, more recruitment of the left PFC was found in the high-performers than in the lower-performers. In conclusion, age-related deficiencies in response inhibition were observed in both behavioral performance and neurophysiological measurement. Our results also suggested that frontal recruitment plays a compensatory role in successful inhibition