Validity and Reliability of a 2-Min Walk Test to Assess the Exercise Capacity in Vertebral Compression Fracture Patients: A Pilot Study.

BACKGROUND: The 2-min walk test (2MWT) may be a simple and easy measurement of exercise tolerance for vertebral compression fracture (VCF) patients. But, the validity and reliability of the 2MWT in patients with VCFs have not been verified. The aim of this pilot study was to investigate the validity and reliability of the 2MWT in VCF patients. METHODS: Ten patients with VCFs were selected from the inpatient convalescence rehabilitation ward. These patients were required to walk for a minimum of 6 minutes. The study was conducted over three test days. On the first and second test days, the participants completed one trial of the 2MWT each day. These data were used in the analyses for an intra-class correlation coefficient (ICC [1,1]). On the third test day, participants completed the 6-min walk test (6MWT). These data assessed the construct validity of the 2MWT. Participants completed testing on 3 days within a 5-day period. RESULTS: A significant correlation was found between the 2MWT and the 6MWT (r=0.945; p<0.05), which suggested a high construct validity of the 2MWT. The intraclass correlation coefficient of the repeated 2MWTs was high (ICC=0.98; p<0.05), intimating that it had a high test-retest reliability. CONCLUSION: The 2MWT is a valid test for the assessment of exercise capacity in patients with VCFs. It is practical, simple, and well tolerated by patients with VCFs.

Surface modification of mica due to titanium sputtering as studied by positron annihilation.

Study was conducted of surface structural modification of layered sheets of mica that had been subjected to titanium (Ti) sputter coating, use being made of a variable but mono energetic slow positron beam. Comparison has been drawn with the structure of pure muscovite mica sheet. Doppler broadening (DB) of the energy of annihilation radiation has been used as a parameter to assay changes in the surface characteristics within a depth profile of 500 angstroms. In support of these investigations, X-ray reflectivity data was used to assay titanium film thickness and the electron density profile of the film on mica. Finally, changes involving the surface micro-morphology of the system have been corroborated by scanning electron microscopy.

Positron annihilation spectroscopic evidence to demonstrate the flux-enhancement mechanism in morphology-controlled thin-film-composite (TFC) membrane.

In this study, positron annihilation lifetime spectroscopy (PALS) is applied to explain the flux-enhancement mechanism in thin-film-composite (TFC) membranes prepared by using dimethyl sulfoxide (DMSO) as an additive in the interfacial polymerization. The TFC membranes show a large increase in water flux, up to 5-fold, compared to nonadditive membrane. Atomic force microscopy (AFM) shows that surface roughness and surface area increase when DMSO in the aqueous phase solution phase works to increase miscibility of the aqueous and the organic phase by reducing the solubility difference of two immiscible solutions. X-ray photoelectron spectroscopy (XPS) reveals the variation of the chemical compositions to the extent that there is a considerable increase in the cross-linked amide linkages of the flux-enhanced TFC membranes. The effects of these structural changes on the molecular-size free volume properties are evaluated by PALS studies. The PALS results are the first to experimentally show that the thin films of cross-linked aromatic polyamide RO membranes are composed of two types of pores having radii of about 2.1-2.4 A from tau3, network pore, and 3.5-4.5 A from tau4, aggregate pore. The increase in the size and number of network pores by means of DMSO addition during interfacial polymerization enhances the water flux notably. The size of aggregate pores also increases and may contribute to enhance water flux, although their number inevitably decreases as the number of network pores becomes increased. Details on the correlations between RO performances and o-Ps lifetime parameters are clearly described based on the pore-flow model of reverse osmosis developed by Sourirajan et al.

Mechanism of enhanced positronium formation in low-temperature polymers.

An enhanced positronium (Ps) formation in low-temperature polymers has been widely observed. The additional positronium formation is due to shallow trapped electrons in them. Positron annihilation lifetime spectroscopy was applied to investigate the Ps formation in a series of polymers, such as low-density polyethylene, ethylene-methyl methacrylate copolymers with various methyl methacrylate contents, and pure poly(methyl methacrylate) at low temperature. An analysis of the experimental data based on simple kinetic equations enables one to understand the Ps formation mechanism in polymers during low-temperature positron annihilation experiments as functions of the temperature and elapsed time. Good fittings of the experimental data were obtained. The fitting parameters seemed to show clear physical meanings.