Effect of Localized Vibration Using Massage Gun at 40hz and 50hz on Blood Flow

Data has shown that whole body vibration can positively affect blood flow, however, there are very few studies on the effect of localized therapeutic vibration on arterial blood flow. Occupational studies looking at localized vibration effects on skin blood flow normally include high frequency settings. In the last few years, massage guns have become popular, but they operate at lower frequencies. Currently, there is no data on the effects of localized vibration from massage guns on arterial blood flow. PURPOSE: To compare the effects of two different frequencies of localized vibration on blood flow in the popliteal artery. METHODS: 12 subjects participated in this study (8 males and 4 females). Mean age was 22.7±1.6 years; mean height was 181.1±11.8 cm; mean weight was 78.2±16.2 kg. Participants wore shorts to give access to the popliteal artery. Participants were hooked to ECG leads to control measurement of artery diameter and then laid on a treatment table in a prone position with a foam roller under their ankles. Once at resting heart rate, baseline blood flow readings were taken using ultrasound, which measured TA Mean and Volume Flow. The participants were then randomly given a 5-minute treatment of control with no vibration or vibration at 40hz or 50hz. Blood flow readings were taken immediately post-treatment and then every minute for 5 minutes after. RESULTS: A two-factor repeated measures analysis was performed. Each subject was measured under all levels of condition (Control 5 min, 40hz 5 min, and 50hz 5 min) and time (baseline, post, post1-5). TA Mean and Volume Flow for both 40hz and 50hz were significantly greater than control (p=0.0020 and p=0.0110 respectively). The effect of time was significant (

Misfit Layer Compounds and Ferecrystals: Model Systems for Thermoelectric Nanocomposites

A basic summary of thermoelectric principles is presented in a historical context, following the evolution of the field from initial discovery to modern day high-zT materials. A specific focus is placed on nanocomposite materials as a means to solve the challenges presented by the contradictory material requirements necessary for efficient thermal energy harvest. Misfit layer compounds are highlighted as an example of a highly ordered anisotropic nanocomposite system. Their layered structure provides the opportunity to use multiple constituents for improved thermoelectric performance, through both enhanced phonon scattering at interfaces and through electronic interactions between the constituents. Recently, a class of metastable, turbostratically-disordered misfit layer compounds has been synthesized using a kinetically controlled approach with low reaction temperatures. The kinetically stabilized structures can be prepared with a variety of constituent ratios and layering schemes, providing an avenue to systematically understand structure-function relationships not possible in the thermodynamic compounds. We summarize the work that has been done to date on these materials. The observed turbostratic disorder has been shown to result in extremely low cross plane thermal conductivity and in plane thermal conductivities that are also very small, suggesting the structural motif could be attractive as thermoelectric materials if the power factor could be improved. The first 10 compounds in the [(PbSe)1+δ]m(TiSe2)n family (m, n ≤ 3) are reported as a case study. As n increases, the magnitude of the Seebeck coefficient is significantly increased without a simultaneous decrease in the in-plane electrical conductivity, resulting in an improved thermoelectric power factor

Tuning Electrical Properties through Control of TiSe₂ Thickness in (BiSe)_1+δ(TiSe₂)_<i>n</i> Compounds

A series of (BiSe)_1+δ(TiSe₂)_<i>n</i> compounds where <i>n</i> was varied from two to four were synthesized and electrically characterized to explore the extent of charge transfer from the BiSe layer to the TiSe₂ layers. These kinetically stable heterostructures were prepared using the modulated elemental reactants (MER) method, in which thin amorphous elemental layers are deposited in an order that mimics the nanostructure of the desired product. X-ray diffraction (XRD), X-ray area diffraction, and scanning transmission electron microscopy (STEM) data show that the precursors formed the desired products. Specular diffraction scans contain only 00<i>l</i> reflections, indicating that the compounds are crystallographically aligned with the <i>c</i>-axis perpendicular to the substrate. The <i>c</i>-axis lattice parameter increases by 0.604(3) nm with each additional TiSe₂ layer. In-plane diffraction scans contain reflections that can be indexed as the (<i>hk</i>0) of the BiSe and TiSe₂ constituents. Area diffraction scans are also consistent with the samples containing only BiSe and TiSe₂ constituents. Rietveld refinement of the 00<i>l</i> XRD data was used to determine the positions of atomic planes along the <i>c</i>-axis. STEM data supports the structures suggested by the diffraction data and associated refinements but also shows that antiphase boundaries occur approximately 1/3 of the time in the BiSe layers. All samples showed metallic behavior for the temperature-dependent electrical resistivity between 20 K and room temperature. Electrical measurements indicated that charge is transferred from the BiSe layer to the TiSe₂ layer. The measured Hall coefficients were all negative indicating that electrons are the majority carrier and are systematically decreased as <i>n</i> was increased. Assuming a single parabolic band model, carrier concentration decreased when the number of TiSe₂ layers is increased, suggesting that the amount of charge donated by the BiSe layer to the TiSe₂ layers is constant. Seebeck coefficients were negative for all of the (BiSe)_1+δ(TiSe₂)_<i>n</i> compounds studied, indicating that electrons are the majority carrier, and decreased as <i>n</i> increased. The effective mass of the carriers was calculated to be 5–6 m_e for the series of compounds

Structural Changes as a Function of Thickness in [(SnSe)_1+δ]_<i>m</i>TiSe₂ Heterostructures

Single- and few-layer metal chalcogenide compounds are of significant interest due to structural changes and emergent electronic properties on reducing dimensionality from three to two dimensions. To explore dimensionality effects in SnSe, a series of [(SnSe)_1+δ]_<i>m</i>TiSe₂ intergrowth structures with increasing SnSe layer thickness (<i>m</i> = 1–4) were prepared from designed thin-film precursors. In-plane diffraction patterns indicated that significant structural changes occurred in the basal plane of the SnSe constituent as <i>m</i> is increased. Scanning transmission electron microscopy cross-sectional images of the <i>m</i> = 1 compound indicate long-range coherence between layers, whereas the <i>m</i> ≥ 2 compounds show extensive rotational disorder between the constituent layers. For <i>m</i> ≥ 2, the images of the SnSe constituent contain a variety of stacking sequences of SnSe bilayers. Density functional theory calculations suggest that the formation energy is similar for several different SnSe stacking sequences. The compounds show unexpected transport properties as <i>m</i> is increased, including the first p-type behavior observed in (MSe)_<i>m</i>(TiSe₂)_<i>n</i> compounds. The resistivity of the <i>m</i> ≥ 2 compounds is larger than for <i>m</i> = 1, with <i>m</i> = 2 being the largest. At room temperature, the Hall coefficient is positive for <i>m</i> = 1 and negative for <i>m</i> = 2–4. The Hall coefficient of the <i>m</i> = 2 compound changes sign as temperature is decreased. The room-temperature Seebeck coefficient, however, switches from negative to positive at <i>m</i> = 3. These properties are incompatible with single band transport indicating that the compounds are not simple composites