3 research outputs found
Virtual reality-based monitoring test for MCI: A multicenter feasibility study
ObjectivesAs the significance of the early diagnosis of mild cognitive impairment (MCI) has emerged, it is necessary to develop corresponding screening tools with high ecological validity and feasible biomarkers. Virtual reality (VR)-based cognitive assessment program, which is close to the daily life of the older adults, can be suitable screening tools for MCI with ecological validity and accessibility. Meanwhile, dehydroepiandrosterone (DHEA) has been observed at a low concentration in the older adults with dementia or cognitive decline, indicating its potential as a biomarker of MCI. This study aimed to determine the efficacy and usability of a VR cognitive assessment program and salivary DHEA for screening MCI.MethodsThe VR cognitive assessment program and the traditional Montreal Cognitive Assessment (MOCA) test were performed on 12 patients with MCI and 108 healthy older adults. The VR program operates in a situation of caring for a grandchild, and evaluates the memory, attention, visuospatial, and executive functions. An analysis of covariance (ANCOVA), a partial correlation analysis, and receiving operating characteristic (ROC) curve analysis were conducted for statistical analysis.ResultsAccording to the ANCOVA, no significant difference in MOCA scores was found between the normal and MCI groups (F = 2.36, p = 0.127). However, the VR total score of the MCI group was significantly lower than that of the normal group (F = 8.674, p = 0.004). There was a significant correlation between the MOCA and VR scores in the total and matched subdomain scores. The ROC curve analysis also showed a larger area under the curve (AUC) for the VR test (0.765) than for the MOCA test (0.598), and the sensitivity and specificity of the VR program were 0.833 and 0.722, respectively. Salivary DHEA was correlated with VR total (R2 = 0.082, p = 0.01) and attention scores (R2 = 0.086, p = 0.009).ConclusionThe VR cognitive test was as effective as the traditional MOCA test in the MCI classification and safe enough for older adults to perform, indicating its potential as a diagnostic tool. It has also been shown that salivary DHEA can be used as a biomarker for MCI
Generating Large Thermally Stable Marangoni-Driven Topography in Polymer Films by Stabilizing the Surface Energy Gradient
Marangoni forces drive a fluid to
flow in response to positional
differences in surface energy. In thin polymer films, a difference
in surface energy between two coincident liquid polymers could offer
a useful route to manufacture topographically patterned surfaces via
the Marangoni effect. Previously, we have demonstrated a photochemical
method using the Marangoni effect for patterning thin polystyrene
films. To generalize the approach, a theoretical model that gives
the underlying physics of this process was also developed, which further
revealed that low viscosities, low diffusivities, and large surface
energy gradients favor rapid evolution of large film thickness variations.
However, as described by the StokesâEinstein equation or the
Rouse model, low viscosity is generally correlated with high diffusivity
in a single-component system. Herein, we report a strategy to decouple
film viscosity and diffusivity by co-casting a high molecular weight
surface energy gradient creating copolymer (low diffusivity) with
a low molecular weight majority homopolymer (high diffusivity and
low viscosity), which are miscible with each other. Patterned light
exposure through a photomask imposes a patterned surface energy gradient
between light-exposed and unexposed regions due to photochemical reactions
involving only the low diffusivity component. Upon heating the film
to the liquid state, the film materials (primarily the low viscosity
homopolymer component) flow from the low to high surface energy regions.
This strategy either eliminates or greatly slows dissipation of the
prepatterned surface energy gradient while maintaining rapid feature
formation, resulting in formation of ca. 500 nm high features within
only 30 min of thermal annealing. Furthermore, the formed features
are stable upon extended thermal annealing for up to one month. It
is found that a ratio of Marangoni forces to capillary forces can
provide a predictive metric that distinguishes which scenarios produce
features that dissipate or persist
Marangoni Instability Driven Surface Relief Grating in an Azobenzene-Containing Polymer Film
The Marangoni effect describes fluid
flow near an interface in
response to a surface tension gradient. Here, we demonstrate that
the Marangoni effect is the underlying mechanism for flow driven feature
formation in an azobenzene-containing polymer film; features formed
in azobenzene-containing polymers are often referred to as surface
relief gratings or SRGs. An amorphous polyÂ(4-(acryloylÂoxyhexylÂoxy)-4â˛-pentylÂazobenzene)
was synthesized and studied as a model polymer. To isolate the surface
tension driven flow from the surface tension pattern inscription step,
the surface tension gradient was preprogrammed via photoisomerization
of azobenzene in a glassy polymer film without forming topographical
features. Subsequently, the latent image was developed in the absence
of light by annealing above the glass transition temperature where
the polymer is a liquid. The polymer flow direction was controlled
with precision by inducing different surface tension changes in the
exposed regions, in accordance with expectation based on the Marangoni
effect. Finally, the height of the formed features decreased upon
extensive thermal annealing due to capillary leveling with two distinct
rates. A scaling analysis revealed that those rates originated from
dissimilar capillary velocities associated with different azobenzene
isomers