Dehydrogenation of goethite in Earth's deep lower mantle.

The cycling of hydrogen influences the structure, composition, and stratification of Earth's interior. Our recent discovery of pyrite-structured iron peroxide (designated as the P phase) and the formation of the P phase from dehydrogenation of goethite FeO2H implies the separation of the oxygen and hydrogen cycles in the deep lower mantle beneath 1,800 km. Here we further characterize the residual hydrogen, x, in the P-phase FeO2Hx Using a combination of theoretical simulations and high-pressure-temperature experiments, we calibrated the x dependence of molar volume of the P phase. Within the current range of experimental conditions, we observed a compositional range of P phase of 0.39 < x < 0.81, corresponding to 19-61% dehydrogenation. Increasing temperature and heating time will help release hydrogen and lower x, suggesting that dehydrogenation could be approaching completion at the high-temperature conditions of the lower mantle over extended geological time. Our observations indicate a fundamental change in the mode of hydrogen release from dehydration in the upper mantle to dehydrogenation in the deep lower mantle, thus differentiating the deep hydrogen and hydrous cycles.

Comparison of the FeO(2+) and FeS(2+) complexes in the cyanide and isocyanide ligand environment for methane hydroxylation.

A general comparison of fundamental distinctions between the FeO(2+) and FeS(2+) complexes in an identical cyanide or isocyanide ligand environment for methane hydroxylation has been probed computationally in this work in a series of hypothetical [Fe(IV)(X)(CN)5](3-), [Fe(IV)(X)(NC)5](3-), (X = O, S) complexes. We have detailed an analysis of the geometric and electronic structures using density functional theory calculations. In addition, their σ- and π-mechanisms in C-H bond activation process have been described with the aid of the schematic molecular orbital diagram. From our theoretical results, it is shown that (a) the iron(IV)-sulfido complex apparently is able to hydroxylate C-H bond of methane as good as the iron(IV)-oxo species, (b) the O-CN, S-CN complexes have an inherent preference for the low-spin state, while for the case of O-NC and S-NC in which S = 1 and S = 2 states are relatively close in energy, (c) each of the d block electron orbital plays an important role, which is not just spectator electron, and (d) in comparison to the cyanide and isocyanide ligand environment, we can see that the FeS(2+) species prefer the cyanide ligand environment, while the FeO(2+) species favor the isocyanide ligand environment. In addition, a remarkably good correlation of the σ-/π-mechanism for hydrogen abstraction from methane with the gap between the Fe-dz2 (α) and C-H (α) pair as well as the Fe-dxz/yz (ß) and C-H (ß) pair has been found.

Order effects of concurrent endurance and resistance training on post-exercise response of non-trained women.

Physical exercise is used for the promotion and maintenance of good health and for the improvement of physical fitness. Both endurance and resistance exercises are needed to carry out a complete training program. Because time may be a barrier to physical exercise practice, the aim of this study was to verify whether the order of execution of endurance and resistance exercises, in concurrent training, has different effects on the metabolic responses during recovery. Thirteen healthy women [24.40 (1.67) years, Mean (SD)] were investigated for energy expenditure (EE), oxygen consumption (VO2), ventilation (Ve), respiratory frequency (RF), proportion of oxygen in expired air (FeO2) and ratings of perceived exertion (RPE) both before and after three concurrent endurance and resistance trainings, carried out in different orders: endurance-resistance training (ERT), resistance-endurance training (RET) and alternating endurance-resistance training (AERT). AERT elicited a significantly greater increase of EE, VO2, and Ve and a greater decrease of FeO2. ERT elicited a lower increase of RPE. Acute post-exercise physiological responses to concurrent endurance and resistance physical exercise seem to depend on the order of execution of the two parts: among the selected protocols, AERT seems to elicit the best responses. Key pointsThe concurrent execution of both endurance and resistance exercise, in the same training session, could be a practical solution to conform to guidelines for health in the presence of lack of time.The order of concurrent execution of both endurance and resistance exercise, in the same training session, influences the amplitude of some post-exercise physiological responses.