Silicon's sensitivity to corrosion has hindered its use in photoanode applications. We found that deposition of a ~2-nanometer nickel film on n-type silicon (n-Si) with its native oxide affords a high-performance metal-insulator-semiconductor photoanode for photoelectrochemical (PEC) water oxidation in both aqueous potassium hydroxide (KOH, pH = 14) and aqueous borate buffer (pH = 9.5) solutions. The Ni film acted as a surface protection layer against corrosion and as a nonprecious metal electrocatalyst for oxygen evolution. In 1 M aqueous KOH, the Ni/n-Si photoanodes exhibited high PEC activity with a low onset potential (~1.07 volts versus reversible hydrogen electrode), high photocurrent density, and durability. The electrode showed no sign of decay after ~80 hours of continuous PEC water oxidation in a mixed lithium borate-potassium borate electrolyte. The high photovoltage was attributed to a high built-in potential in a metal-insulator-semiconductor-like device with an ultrathin, incomplete screening Ni/NiO(x) layer from the electrolyte.

Electrolysis of water to generate hydrogen fuel is an attractive renewable energy storage technology. However, grid-scale freshwater electrolysis would put a heavy strain on vital water resources. Developing cheap electrocatalysts and electrodes that can sustain seawater splitting without chloride corrosion could address the water scarcity issue. Here we present a multilayer anode consisting of a nickel–iron hydroxide (NiFe) electrocatalyst layer uniformly coated on a nickel sulfide (NiSx) layer formed on porous Ni foam (NiFe/NiSx-Ni), affording superior catalytic activity and corrosion resistance in solar-driven alkaline seawater electrolysis operating at industrially required current densities (0.4 to 1 A/cm2) over 1,000 h. A continuous, highly oxygen evolution reaction-active NiFe electrocatalyst layer drawing anodic currents toward water oxidation and an in situ-generated polyatomic sulfate and carbonate-rich passivating layers formed in the anode are responsible for chloride repelling and superior corrosion resistance of the salty-water-splitting anode.

Recent investigations have demonstrated that there is a sustained reduction in arterial blood pressure after a single bout of exercise, ie, postexercise hypotension (PEH). The purpose of this discussion is to integrate the available information on this topic and to review studies using sustained stimulation of somatic afferents in experimental rats as a model to study the role of somatic afferents in PEH. PEH occurs in response to several types of large-muscle dynamic exercise (ie, walking, running, leg cycling, and swimming) at submaximal intensities greater than 40% of peak aerobic capacity and exercise durations generally between 20 and 60 minutes. PEH is observed in both normotensive and hypertensive humans and in spontaneously hypertensive rats but is generally greater in magnitude in hypertensive subjects. The maximal exercise-induced reductions in systolic and diastolic arterial blood pressures have been on average 18 to 20 and 7 to 9 mm Hg, respectively, in hypertensive humans and 8 to 10 and 3 to 5 mm Hg, respectively, in normotensive humans. PEH has been reported to persist for 2 to 4 hours under laboratory conditions. Whether PEH is sustained for a prolonged period of time under free-living conditions remains controversial, although the results of one study indicate that PEH can persist for up to 13 hours. Possible mechanisms involved in mediating postexercise and poststimulation reductions in arterial blood pressure include decreased stroke volume and cardiac output; reductions in limb vascular resistance, total peripheral resistance, and muscle sympathetic nerve discharge; group HI somatic afferent activation; altered baroreceptor reflex circulatory control; reduced vascular responsiveness to o-adrenergic receptormediated stimulation; and activation of endogenous opioid and serotonergic systems. It appears that the magnitude of PEH in hypertensive subjects is clinically significant; however, more investigation is required to determine if the duration is sufficient under real-life conditions to contribute to the reduction in blood pressure observed with chronic exercise conditioning.

The low magnetic saturation of iron oxide nanoparticles, developed primarily as contrast agents for magnetic resonance imaging, limits the sensitivity of their detection via magnetic particle imaging. Here, we show that FeCo nanoparticles 10 nm in core diameter bearing a graphitic carbon shell decorated with poly(ethylene glycol) provide a signal intensity for magnetic particle imaging that is about 6-fold and 15-fold higher than the signals from the superparamagnetic iron oxide tracers Vivotrax and Feraheme at the same molar concentration of iron. We also show that the nanoparticles have photothermal and magnetothermal properties and can thus be used for tumour ablation in mice, and that they have high optical absorbance in a broad near-infrared region spectral range (700–1200 nm in wavelength), which also makes them suitable as tracers for photoacoustic imaging. As sensitive multifunctional and multimodal imaging tracers, carbon-coated FeCo nanoparticles may confer advantages in cancer imaging and hyperthermia therapy.

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