Linear α,ω-vinyl-terminated poly(diethylsiloxane) (PDES) chains were synthesized and
fractionated to obtain melts of low polydispersity. The fractionated samples were characterized using gel
permeation chromatography and dilute solution viscometry. PDES elastomers were also prepared from
the melts using hydrosilylation end-linking. The effects of chain stiffness on solution viscometric properties
and on network swelling in toluene were compared to previously obtained results with poly(dimethylsiloxane) (PDMS). The mechanical behavior of the PDES elastomers in uniaxial extension was studied
with a Perkin-Elmer dynamic mechanical analyzer. The dry networks exhibit a stress-induced amorphous-to-mesophase transition, which results in a discontinuous stress−strain relationship. The effects of
molecular-level structure on network mechanical properties were deduced by studying PDES elastomers
with well-defined molecular weight between chemical cross-links.
Prolonged immobilization from a critical illness can result in significant muscle atrophy. Whole-body vibration (WBV) could potentially attenuate the issue of muscle atrophy; however, there exists no device that could potentially provide WBV in supine position that is suitable for critically ill patients. Hence, the purpose of this study was to develop a new wearable suit, called therapeutic vibration device (TVD), that can provide WBV in supine position and test its effects on physiologic markers of physical activity including muscle activation, oxygen consumption (VO
2
), and regional hemoglobin oxygen saturation (rSO
2
). The prototype TVD delivered multi-frequency WBV axially to 19 healthy participants in supine position for 10 minutes simultaneously at 25 Hz/4.2 g
rms
on the feet and 15 Hz/0.7 g
rms
on the shoulders. Muscle activation was recorded by electromyography (EMG), VO
2
was measured by indirect calorimetry and rSO
2
was recorded by near-infrared spectroscopy. Recordings were collected from each participant from multiple body locations, on three separate days, at baseline and during the intervention. Acceleration was also recorded to gain insight into transmissibility and coherence. Repeated-measures ANOVA using Bonferroni correction revealed that the muscle activity significantly increased by 4% - 62% (
p
< 0.05), VO
2
improved by 22.3% (
p
< 0.05) and rSO
2
increased by 1.4% - 4.5% (
p
< 0.05) compared to baseline. WBV provided by the TVD is capable of producing physiologic responses consistent with mild physical activity. Such effects could potentially be valuable as an adjunct to physical therapy for early mobilization to prevent atrophy occurring from prolonged immobilization.
A simple and useful empirical relationship showing the volume dependence of short-range force constant is investigated. The relation is found to hold well for the variation from one crystal to the other as well as for a given crystal under changing volume. The usefulness of the relationship is demonstrated by calculating thc volume derivatives of dielectric constant, and optic mode longitudinal and transverse Gruneisen parameters. The special feature of these calculations is that they do not require the detailed knowledge of the interionic potentials. The results obtained are found in good agreement with experimental data.Eine einfache und nutzliche Beziehung fur die Volumenabhangigkeit der kurzreichweitigen Kraftkonstante wird untersncht. Es zeigt sich, da8 diese Beziehung gut zutrifft fur die Anderung von Kristall zu Kristall wie fur einen Kristall unter Volumenanderung. Die Brauchbarkeit der Beziehung wird anhand der Berechnung der Volumenabhangigkeit der Dielektrizit5tskonstante und optisch-longitudinaler wie -transversaler Gruneisen-Konstanten gezeigt. Diese Rechnung erfordert keine detaillierte Keniitnis der Ionenpotentisle. Die Ergebnisse stimmen gut mit experimentellen Daten iiberein.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.