Revealing Molecular-Scale Structural Changes in Polymer Nanocomposites during Thermo-Oxidative Degradation Using Evolved Gas Analysis with High-Resolution Time-of-Flight Mass Spectrometry Combined with Principal Component Analysis and Kendrick Mass Defect Analysis.

This study introduces a novel method that utilizes evolved gas analysis with time-of-flight mass spectrometry (EGA-TOFMS) coupled with principal component analysis (PCA) and Kendrick mass defect (KMD) analysis, called EGA-PCA-KMD, to analyze complex structural changes in polymer materials during thermo-oxidative degradation. While EGA-TOFMS captures exact mass data related to the degradation components in the temperature-dependent mass spectra of the evolved products, numerous high-resolution mass spectra with large amounts of ion signals and varying intensities provide challenges for interpretation. To address this, we employed mathematical decomposition through PCA to selectively extract information about the ion series specific to the products that evolved from the degradation components. Additionally, KMD analysis was applied to the attribution of the exact mass signals extracted from the PCA, which categorizes and visualizes depending on the molecular compositions in a two-dimensional plot. The complex structural changes of the triblock copolymer thermoplastic elastomer and its nanocomposites containing nanodiamonds during thermo-oxidative degradation were elucidated using EGA-PCA-KMD to demonstrate the effectiveness of this characterization technique for polymer degradation. Furthermore, it is revealed that the formation of rigid matrix-filler interfacial interaction via the π-π stacking and chemical bonds in the nanocomposites contributes to improvement in the stability toward thermo-oxidative degradation. Our results highlight the benefits of EGA-PCA-KMD and provide valuable insights into polymer degradation.

Sensitivity to change and responsiveness of the Balance Evaluation Systems Test (BESTest), Mini-BESTest, and Brief-BESTest in patients with subacute cerebral infarction.

[Purpose] To compare the sensitivity to change and responsiveness of the Balance Evaluation Systems Test, Mini-Balance Evaluation Systems Test, and Brief-Balance Evaluation Systems Test in patients with subacute cerebral infarction. [Participants and Methods] Thirty patients with subacute cerebral infarction participated in this study. The Balance Evaluation Systems Test, Mini-Balance Evaluation Systems Test, Brief-Balance Evaluation Systems Test, Berg Balance Scale, and ambulatory ability were assessed on admission and discharge. Sensitivity to change was calculated using the effect size, standardized response mean, and relative efficiency. Responsiveness was analyzed by comparing the ability of the difference between the scores of the balance assessments at admission and discharge in classifying the participants' ambulatory independence. [Results] All assessments showed significant improvement from admission to discharge. The effect size of the three versions of the Balance Evaluation Systems Test ranged from 0.41 to 0.69. The standardized response mean ranged from 0.75 to 1.28. The cutoff score was 16.7% for the Balance Evaluation Systems Test, 5.5 points for the Mini-Balance Evaluation Systems Test, 1.5 points for the Brief-Balance Evaluation Systems Test, and 3.5 points for the Berg Balance Scale. [Conclusion] The sensitivity to change of the three versions of the Balance Evaluation Systems Test was high or moderate. However, the Mini-Balance Evaluation Systems Test had the highest responsiveness, as determined with the extent of ambulatory independence.