RESUMEN
PURPOSE: Presenteeism is defined as the loss of work productivity due to health issues in workers, which can be measured subjectively. This study aimed to compare the effectiveness of supervised exercise therapy and unsupervised self-care in reducing presenteeism in workers with musculoskeletal disorders. METHODS: PubMed, Embase, and Cochrane Library were searched for various keywords from their inception to January 2023. Two examiners independently assessed the eligibility of studies: (1) studies involving workers suffering from musculoskeletal pain, (2) those involving supervised exercise therapy intervention with interactive communication, and (3) those in which the comparison group was subjected to interventions other than supervised exercise therapy, and (4) those including patient-reported outcome measures of presenteeism or work productivity or ability. Standardized mean differences (SMD) were calculated using a random effects model, with higher scores indicating reduced presenteeism in the intervention group compared with that in the comparison group. The GRADE assesses the overall certainty of the evidence. RESULTS: Only the short-term effects of interventions on presenteeism could be obtained using four studies. The intervention group showed statistically significant short-term effects on presenteeism compared with the comparison group (p < 0.001; SMD, 0.52; 95% confidence interval, 0.27-0.77). The GRADE score was downgraded by two levels from high to low due to concerns for indirectness. CONCLUSIONS: Although the certainty of the evidence was low, it was assumed that supervised exercise therapy was more effective than unsupervised self-care in reducing presenteeism in workers with musculoskeletal disorders.
RESUMEN
The relative abundance of light elements in the Earth's core has long been controversial. Recently, the presence of carbon in the core has been emphasized, because the density and sound velocities of the inner core may be consistent with solid Fe7C3. Here we report the longitudinal wave velocity of liquid Fe84C16 up to 70 GPa based on inelastic X-ray scattering measurements. We find the velocity to be substantially slower than that of solid iron and Fe3C and to be faster than that of liquid iron. The thermodynamic equation of state for liquid Fe84C16 is also obtained from the velocity data combined with previous density measurements at 1 bar. The longitudinal velocity of the outer core, about 4% faster than that of liquid iron, is consistent with the presence of 4-5 at.% carbon. However, that amount of carbon is too small to account for the outer core density deficit, suggesting that carbon cannot be a predominant light element in the core.
RESUMEN
Light elements such as oxygen in Earth's core influence the physical properties of the iron alloys that exist in this region. Describing the high-pressure behavior of these materials at core conditions constrains models of core structure and dynamics. From x-ray diffraction measurements of iron monoxide (FeO) at high pressure and temperature, we show that sodium chloride (NaCl)-type (B1) FeO transforms to a cesium chloride (CsCl)-type (B2) phase above 240 gigapascals at 4000 kelvin with 2% density increase. The oxygen-bearing liquid in the middle of the outer core therefore has a modified Fe-O bonding environment that, according to our numerical simulations, suppresses convection. The phase-induced stratification is seismologically invisible but strongly affects the geodynamo.
RESUMEN
A melt has greater volume than a silicate solid of the same composition. But this difference diminishes at high pressure, and the possibility that a melt sufficiently enriched in the heavy element iron might then become more dense than solids at the pressures in the interior of the Earth (and other terrestrial bodies) has long been a source of considerable speculation. The occurrence of such dense silicate melts in the Earth's lowermost mantle would carry important consequences for its physical and chemical evolution and could provide a unifying model for explaining a variety of observed features in the core-mantle boundary region. Recent theoretical calculations combined with estimates of iron partitioning between (Mg,Fe)SiO(3) perovskite and melt at shallower mantle conditions suggest that melt is more dense than solids at pressures in the Earth's deepest mantle, consistent with analysis of shockwave experiments. Here we extend measurements of iron partitioning over the entire mantle pressure range, and find a precipitous change at pressures greater than â¼76 GPa, resulting in strong iron enrichment in melts. Additional X-ray emission spectroscopy measurements on (Mg(0.95)Fe(0.05))SiO(3) glass indicate a spin collapse around 70 GPa, suggesting that the observed change in iron partitioning could be explained by a spin crossover of iron (from high-spin to low-spin) in silicate melt. These results imply that (Mg,Fe)SiO(3) liquid becomes more dense than coexisting solid at â¼1,800 km depth in the lower mantle. Soon after the Earth's formation, the heat dissipated by accretion and internal differentiation could have produced a dense melt layer up to â¼1,000 km in thickness underneath the solid mantle. We also infer that (Mg,Fe)SiO(3) perovskite is on the liquidus at deep mantle conditions, and predict that fractional crystallization of dense magma would have evolved towards an iron-rich and silicon-poor composition, consistent with seismic inferences of structures in the core-mantle boundary region.
