PurposeThe purpose of this study was to explore the effects of an innovative momentum-based dumbbell-training intervention on cognitive function in older adults with mild cognitive impairment (MCI).Subjects and methodsA total of 45 community-dwelling older adults with MCI were randomly assigned to either a dumbbell-training group (DTG; n=22) or a control group (CG; n=23). Participants in the DTG participated in exercise sessions three times weekly for 12 weeks. The primary outcome measures were cognitive function, including the Alzheimer’s Disease Assessment Scale (ADAS) – Cognitive subscale, Trail Making Test part B, Digit Span Test (DST) – forward, and DST – backward, with secondary outcome measures being Timed Up and Go, functional reach, and the Activities-Specific Balance Confidence Scale.ResultsIn an intent-to-treat analysis, participants in the DTG had significantly improved ADAS – Cognitive subscale scores compared to those in the CG (5.02 points, P=0.012). There was a significant within-group change (improvement) in Trail Making Test part B (33.32 seconds, P<0.001) and DST – backward (0.41 points, P=0.025) scores. No change was observed for the DST – forward measure. Participants in the DTG also improved their functional mobility compared to those in the CG (Timed Up and Go, 0.81 seconds; P=0.043).ConclusionThere is preliminary evidence showing the potential benefit of momentum-based dumbbell training for improving cognitive function in older adults with MCI.

An investigation was carried out by dielectric relaxation spectroscopy (DRS) and dynamic mechanical spectroscopy (DMS) on the dynamics of aqueous solutions of deoxyribonucleic acid (DNA). Novel information is generated and presented through our use of wide temperature and frequency range in DRS and DMS measurements. Two relaxation processes were detected at temperatures below 273 K. The higher frequency, Debye-like process has an activation energy of 27 kJ/mol and is assigned to the bound water around DNA molecules. The lower frequency process is of the Cole-Cole type and has an activation energy of 55 kJ/mol, the same as that of pure ice. In the higher temperature range, encompassing the physiological condition, conductivity dominates the dielectric response. A pronounced peak in the dielectric modulus spectrum is observed, and its molecular origin is found to lie in the migration of counterions along the DNA surface. Using Manning's model, it was calculated that the subunit length over which counterions fluctuate increases from 70 nm at a concentration of 2 mg/mL to 153 nm at a concentration of 0.125 mg/mL. The results of DMS measurements of aqueous solutions of calf thymus DNA reveal a G′/G′′ crossover point whose frequency (ωC) scales with concentration as ωC ∼ CDNA -2.4 . The implication is that the DNA molecules behave as semiflexible polymers in aqueous solution. The temperature dependence of ω C indicates that the breakup of the DNA base pairs and the chain melting begin at a temperature as low as 50 °C.

An investigation was carried out of the normal and segmental dynamics of poly(propylene oxide) (PPO) chains with (1) symmetrical dipole inversion and (2) three-arm star configuration. PPO chains exhibit, in addition to the transverse dipole moment component (µ ⊥ ) that gives rise to segmental (R) process, a persistent cumulative dipole moment along the chain contour (µ | ) that can be relaxed via the normal mode (RN) process. Data were generated by broad-band dielectric relaxation spectroscopy (DRS) and dynamic mechanical spectroscopy (DMS), and the findings were contrasted. In comparison with the previous studies of PPO dynamics, our DRS and DMS results were generated over a broader range of frequency and temperature and on samples of a wider range of molecular architecture (molecular weight, type, and functionality of end group). Segmental and normal mode spectra were thermodielectrically simple (with the KWW β parameter of ca. 0.51). The average relaxation times for the segmental mode (τ S) from DRS and DMS were in excellent agreement. A direct comparison of the normal mode relaxation times (τN) obtained from DRS and DMS data had to account for the longest viscoelastic relaxation time (τN1DMS) of the Rouse chain being one-half the longest dielectric relaxation time (τN1DRS) and twice the second dielectric normal mode relaxation time (τN2DRS), which is experimentally measured. We observed excellent agreement between (1) our DRS and DMS data, (2) our data and the results of other groups, and (3) our data and the prediction of the Rouse model for MW less than 12 000 g/mol. The molecular weight dependence of τN1DMS at 273 K is characterized by an exponent of 2, in perfect agreement with τN2DRS.

An investigation was carried out on the effect of molecular architecture on the dynamics of multigraft (MG) copolymers of polyisoprene (PI) and polystyrene (PS). MG copolymers with regularly spaced multiple grafts with trifunctional (combs), tetrafunctional (centipedes), and hexafunctional (barbwires) branch points were synthesized by anionic polymerization and studied by dielectric relaxation spectroscopy (DRS) and dynamic mechanical spectroscopy (DMS). The PI precursors were characterized by the presence of segmental and normal mode processes. The temperature dependence of the dielectric relaxation time for the segmental (τ S) and normal mode (τN) process was of the Vogel-Fulcher-Tammann (VFT) type. In the entangled regime τN scales with M 4.0 . The major findings for the MG copolymers are as follows: (1) all MG copolymers are characterized by the presence of segmental and normal mode relaxation; (2) τ S is independent of molecular weight and architecture; (3) τN is slower in a MG copolymer than in its PI precursor; (4) τN in a MG copolymer of a given architecture is not a function of the overall molecular weight or the number of branch points; (5) the difference between the normal mode relaxation time for a MG copolymer, τ N(PIPS), and its PI precursor, τN(PI), defined as ∆τN ) τN(PIPS) -τN(PI), depends strongly on the molecular weight of the PS graft (MPS). An explanation was offered for the reasons underlying the observed slowdown of the normal mode relaxation in MG copolymers vis-à -vis their PI precursors.

An investigation was conducted of segmental and normal mode dynamics during cross-linking of reactive systems where one of the components exhibits, in addition to the transverse dipole moment (μ⊥) component that gives rise to the segmental α process, a persistent cumulative dipole moment (μ∥) along the chain contour that can be relaxed via the normal mode process. The systems studied were composed of an amine-terminated linear or three-arm star poly(propylene oxide), which contains both μ⊥ and μ∥, and a bifunctional epoxy prepolymer. The kinetics of network formation were evaluated by Fourier transform near-infrared spectroscopy (NIR), and the dynamics were investigated by broad-band dielectric relaxation spectroscopy (DRS) and dynamic mechanical spectroscopy (DMS). The dynamics of networks containing linear and star chains were similar but not identical. The average relaxation time for segmental (τS) and normal mode (τN) increases in the course of network formation, but the distance between τS and τN varies little and the T g-scaled fragility remains unchanged. The spectra become thermodielectrically complex following the onset of reactions and broaden in the course of cure. Segmental and normal mode relaxations overlap increasingly during cure but, interestingly, retain their identities. There is a decrease in the dielectric relaxation strength for the segmental process (ΔεS) and a simultaneous (unexpected) increase in the dielectric relaxation strength for the normal mode process (ΔεN). Before gelation, the DMS response was characterized by segmental and terminal relaxation zone. The gel point was observed at a conversion above that predicted by the gelation theory, and an explanation was put forward.