Increased Sensitivity to Physical Activity in Healthy Older Adults Predicts Worse Pain and Functional Outcomes

poster abstractPrior research indicates older adults with knee osteoarthritis (OA) have increased sensitivity to physical activity (SPA) and respond to physical activities of stable intensity with increases in pain. SPA predicted self-reported pain and function in older adults with knee OA. It is unknown whether SPA is present in healthy older adults without chronic pain and predicts functional outcomes. The purpose of this study was to determine if SPA in response to a standardized 6-minute Walk Test cross-sectionally predicted selfreported pain, physical function, and physical activity behaviors in healthy older adults. Forty-two older adults (age=67.5±5 years) completed the Pain subscale of the Quality of Well Being scale (QWB–measures the frequency and severity of pain during common daily activities), the Short Form Health Survey (SF-36–measure of physical function), the 6-Minute Walk Test (6MWT), and wore an accelerometer on the hip for 7 days. Subjects rated overall bodily discomfort (0-100 scale) prior to and during each minute of the 6MWT. RPE was recorded at the end of the walk. An SPA index was created by subtracting the initial bodily discomfort ratings from the peak ratings. Average moderate to vigorous physical activity/day (MVPA) and steps/day were recorded from the accelerometer. Dependent variables were analyzed with hierarchical linear regressions with SPA as the final predictor. Sixty percent of older adults experienced SPA (SPA=9.5±15.6). After accounting for age, sex, BMI, and meters walked on the 6MWT, SPA significantly predicted steps and MVPA per day, RPE on the 6MWT, and severity and frequency of activity related pain on the QWB scale. These results revealed that increased SPA in healthy older adults was associated with fewer steps and MVPA per day, greater exertion on 6MWT, and greater self-reported activity-related pain. This study was funded by the IUPUI School of PETM Faculty Research Opportunity Grant

Torque magnetometry studies of new low temperature metamagnetic states in ErNi_{2}B_{2}C

The metamagnetic transitions in single-crystal ErNi$_2$B$_2$C have been studied at 1.9 K with a Quantum Design torque magnetometer. The critical fields of the transitions depend crucially on the angle between applied field and the easy axis [100]. Torque measurements have been made while changing angular direction of the magnetic field (parallel to basal tetragonal $ab$-planes) in a wide angular range (more than two quadrants). Sequences of metamagnetic transitions with increasing field are found to be different for the magnetic field along (or close enough to) the easy [100] axis from that near the hard [110] axis. The study have revealed new metamagnetic states in ErNi$_{2}$B$_2$C which were not apparent in previous longitudinal-magnetization and neutron studies.Comment: 3 pages (4 figs. incl.) reported at 52th Magnetism and Magnetic Materials Conference, Tampa, Florida, USA, November 200

Influence of high-energy electron irradiation on the transport properties of La_{1-x}Ca_{x}MnO_{3} films (x \approx 1/3)

The effect of crystal lattice disorder on the conductivity and colossal magnetoresistance in La_{1-x}Ca_{x}MnO_{3} (x \approx 0.33) films has been examined. The lattice defects are introduced by irradiating the film with high-energy (\simeq 6 MeV) electrons with a maximal fluence of about 2\times 10^{17} cm^{-2}. This comparatively low dose of irradiation produces rather small radiation damage in the films. The number of displacements per atom (dpa) in the irradiated sample is about 10^{-5}. Nethertheless, this results in an appreciable increase in the film resistivity. The percentage of resistivity increase in the ferromagnetic metallic state (below the Curie tempetature T_{c}) was much greater than that observed in the insulating state (above T_{c}). At the same time irradiation has much less effect on T_{c} or on the magnitude of the colossal magnetoresistance. A possible explanation of such behavior is proposed.Comment: RevTex, 22 pages, 3 Postscript figures, submitted to Eur. Phys. J.

Torque magnetometry study of metamagnetic transitions in single-crystal HoNi2B2C at T\approx 1.9 K

Metamagnetic transitions in single-crystal rare-earth nickel borocarbide HoNi$_2$B$_2$C have been studied at T\approx 1.9 K with a Quantum Design torque magnetometer. This compound is highly anisotropic with a variety of metamagnetic states at low temperature which includes antiferromagnetic, ferrimagnetic, non-collinear and ferromagnetic-like (saturated paramagnet) states. The critical fields of the transitions depend crucially on the angle $\theta$ between applied field and the easy axis [110]. Measurements of torque along the c-axis have been made while changing the angular direction of the magnetic field (parallel to basal tetragonal $ab$-planes) and with changing field at fixed angle over a wide angular range. Two new phase boundaries in the region of the non-collinear phase have been observed, and the direction of the magnetization in this phase has been precisely determined. At low field the antiferromagnetic phase is observed to be multidomain. In the angular range very close to the hard axis [100] ($-6^{\circ} \lesssim\phi \lesssim 6^{\circ}$, where $\phi$ is the angle between field and the hard axis) the magnetic behavior is found to be ``frustrated'' with a mixture of phases with different directions of the magnetization.Comment: submitted to Phys. Rev. B, 12 pages, 12 figure

Investigation of the superconducting energy gap in the compound LuNi2_{2}B2_{2}C by the method of point contact spectroscopy: two-gap approximation

It is shown that the two-gap approximation is applicable for describing the $dV/dI(V)$ spectra of LuNi$_{2}$B$_{2}$C-Ag point contacts in a wide interval of temperatures. The values and the temperature dependences of the large and the small gaps in the $ab$ plane and in the $c$ direction were estimated using the generalized BTK model and the equations of Beloborodko. In the BCS extrapolation the critical temperature of the small gap is 10 $K$ in the $ab$ plane and 14.5 $K$ in the $c$ direction. The absolute values of the gaps are $\Delta_0^{ab}=2.16$ $meV$ and $\Delta_0^c=1.94$ $meV$. For the large gaps the critical temperature coincides with the bulk $T_c$, $T_c^{bulk}=16.8$ $K$, and their absolute values are very close, being about 3 $meV$ in both orientations. In the $c$ direction the contributions to the conductivity from the small and the large gaps remain practically identical up to $10 \div 11$ $K$. In the $ab$ plane the contribution from the small gap is much smaller and decreases rapidly as a temperature rises.Comment: 10 pages, 10 figures, submitted to Fiz. Nizk. Temp. (Low Temp. Phys.

Transport, thermal and magnetic properties of RuSr_2(Gd_{1.5}Ce_{0.5})Cu_2O_{10-\delta}, a magnetic superconductor

Resistivity, thermoelectric power, heat capacity and magnetization for samples of RuSr_2(Gd_{1.5}Ce_{0.5})Cu_{2}O_{10-\delta} were investigated in the temperature range 1.8-300 K with a magnetic field up to 8 T. The resistive transitions to the superconducting state are found to be determined by the inhomogeneous (granular) structure, characterized by the intragranular, T_{c0}, and intergranular, T_{cg}, transition temperatures. Heat capacity, C(T), shows a jump at the superconducting transition temperature T_{c0}\approx 37.5 K. A Schottky-like anomaly is found in C(T) below 20 K. This low temperature anomaly can be attributed to splitting of the ground term $^{8}S_{7/2}$ of paramagnetic Gd^{3+} ions by internal and external magnetic fields.Comment: 3 pages (4 figs. incl.), reported at 50th Magnetism and Magnetic Materials Conference, San Jose, CA, USA, 200

Torque magnetometry studies of metamagnetic transitions in single-crystal HoNi_{2}B_{2}C and ErNi_{2}B_{2}C at T\approx 1.9 K

The metamagnetic transitions in single-crystal rare-earth nickel borocarbide HoNi_{2}B_{2}C and ErNi_{2}B_{2}C have been studied at 1.9 K with a Quantum Design torque magnetometer. The critical fields of the transitions depend crucially on the angle between applied field and the easy axis [110] for HoNi_2B_2C and [100] for ErNi_2B_2C. Torque measurements have been made while changing angular direction of the magnetic field (parallel to basal tetragonal ab-planes) in a wide angular range (more than two quadrants). The results are used not only to check and refine the angular diagram for metamagnetic transitions in these compounnds, but also to find new features of the metamagnetic states. Among new results for the Ho borocarbide are the influence of a multidomain antiferromagnetic state, and ``frustrated'' behavior of the magnetic system for field directions close to the hard axis [100]. Torque measurements of the Er borocarbide clearly show that the sequence of metamagnetic transitions with increasing field (and the corresponding number of metamagnetic states) depends on the angular direction of the magnetic field relative to the easy axis.Comment: 3pages (4 figs. incl.) reported at 50th Magnetism and Magnetic Materials Conference, San Jose, CA, USA, 200

Low-temperature metamagnetic states in single crystal TbNi2B2C studied by torque magnetometry

Metamagnetic transitions in single crystalTbNi2B2C have been studied at 1.9 K with a Quantum Design torque magnetometer. The critical fields for the transitions depend strongly on the angle between the applied field and the easy axis [100]. Torque measurements have been made while changing the angular direction of the magnetic field (parallel to basal tetragonal ab-planes) at fixed field magnitude and while changing the field magnitude at fixed angular direction over a wide angular range (more than two quadrants). Torque magnetometry (sensitive only to the component of magnetization perpendicular to the field) indicates not only a different sequence of metamagnetic phases for fields near the easy axis from those near the hard axis, but also the different natures of a principal metamagnetic phase near the hard axis. Comparison of the results with longitudinal magnetization measurements is presented