RESUMEN
Isotope compositions of basalts provide information about the chemical reservoirs in Earth's interior and play a critical role in defining models of Earth's structure. However, the helium isotope signature of the mantle below depths of a few hundred kilometers has been difficult to measure directly. This information is a vital baseline for understanding helium isotopes in erupted basalts. We measured He-Sr-Pb isotope ratios in superdeep diamond fluid inclusions from the transition zone (depth of 410 to 660 kilometers) unaffected by degassing and shallow crustal contamination. We found extreme He-C-Pb-Sr isotope variability, with high 3He/4He ratios related to higher helium concentrations. This indicates that a less degassed, high-3He/4He deep mantle source infiltrates the transition zone, where it interacts with recycled material, creating the diverse compositions recorded in ocean island basalts.
RESUMEN
OBJECTIVE: To determine whether anterior knee pain (AKP), during running, acutely affects lower-extremity electromyography (EMG) and articular cartilage metabolism. METHODS: A within-subjects design was used. Each of 12 able-bodied subjects ran on a treadmill for 30 min for three different sessions: control (no infusion), sham (0.9% NaCl infusion into the involved-leg infrapatellar fat pad), and pain (5.0% NaCl infusion into the involved-leg infrapatellar fat pad). Bilateral surface EMG was monitored for the vastus medialis (VM), vastus lateralis (VL), and gastrocnemius (GA). Serum cartilage oligomeric matrix protein (COMP) concentration was determined before, after, and 60 min after the run. A functional analysis approach was used to compare EMG amplitude, across the entire stance phase, between sessions and legs. Mixed-model analysis of covariance was used to compare serum COMP concentration between sessions, across time. RESULTS: Relative to the uninvolved leg, greater involved-leg VL and GA EMG amplitude existed during midstance for the sham and control sessions (P < 0.01). During the painful session, however, involved-leg VM, VL, and GA EMG amplitude was 5-10% less than for the uninvolved leg. COMP concentration immediately post-run was 14% and 21% greater than pre-run (P = 0.01) and 60 min post-run concentrations (P < 0.01), respectively. Session, however, did not significantly influence COMP. CONCLUSION: During a 30-min run, AKP acutely alters midstance VM, VL, and GA EMG amplitude. AKP during a 30-min run does not, however, acutely influence articular cartilage metabolism.
