Molecular vanadium oxides, or polyoxovanadates (POVs), have recently emerged as a new class of molecular energy conversion/storage materials, which combine diverse, chemically tunable redox behavior ...and reversible multielectron storage capabilities. This Review explores current challenges, major breakthroughs, and future opportunities in the use of POVs for energy conversion and storage. The reactivity, advantages, and limitations of POVs are explored, with a focus on their use in lithium and post‐lithium‐ion batteries, redox‐flow batteries, and light‐driven energy conversion. Finally, emerging themes and new research directions are critically assessed to provide inspiration for how this promising materials class can advance research in sustainable energy technologies.
This Review critically discusses recent breakthroughs and future challenges in research on polyoxovanadate energy materials. The use of polyoxovanadates in batteries, redox‐flow batteries, light‐driven catalysis, and electrocatalysis is described together with an outlook on emerging themes and areas of future application.
Increased summer energy use and increased summer heat related mortality are the two most cited detrimental impacts of the urban heat island (UHI). An assessment of these impacts was made that ...considered the annual impact of the UHI, not just the summer impact. It was found that in north of the US there was a net decrease in energy use from the UHI, as heating energy reductions were larger than the increase in cooling energy. In the south there was a net energy increase from the UHI. The impact of the UHI on heat related deaths was an estimated increase of 1.1 deaths per million people. The impact of the UHI on cold related deaths was an estimated decrease of 4.0 deaths per million people. These estimates are caveated by the acknowledgement that compounding factors influence mortality. Hypothermia related death rates were three times higher in rural areas than urban areas. This is surprising as the homeless population is usually considered the most at risk, yet they mostly live in urban areas.
•The urban heat island (UHI) may actually be beneficial in colder cities in the US in terms of energy use•The UHI may cause an increase in heat related mortality of ~1 deaths per million•In winter the UHI may decrease cold related mortality by ~4 deaths per million•Cold related death rates were 3 times higher in rural areas although the homeless population live mainly in urban areas
The assessment of the impacts of climate change at different levels of global warming helps inform national and international policy discussion around mitigation targets. This paper provides ...consistent estimates of global and regional impacts and risks at increases in global mean temperature up to 5 °C above pre-industrial levels, for over 30 indicators representing temperature extremes and heatwaves, hydrological change, floods and droughts and proxies for impacts on crop yields. At the global scale, all the impacts that could plausibly be either adverse or beneficial are adverse, and impacts and risks increase with temperature change. For example, the global average chance of a major heatwave increases from 5% in 1981–2010 to 28% at 1.5 °C and 92% at 4 °C, of an agricultural drought increases from 9 to 24% at 1.5 °C and 61% at 4 °C, and of the 50-year return period river flood increases from 2 to 2.4% at 1.5 °C and 5.4% at 4 °C. The chance of a damaging hot spell for maize increases from 5 to 50% at 4 °C, whilst the chance for rice rises from 27 to 46%. There is considerable uncertainty around these central estimates, and impacts and risks vary between regions. Some impacts—for example heatwaves—increase rapidly as temperature increases, whilst others show more linear responses. The paper presents estimates of the risk of impacts exceeding specific targets and demonstrates that these estimates are sensitive to the thresholds used.
Aim
To systematically review the association between breastfeeding and childhood allergic disease.
Methods
Predetermined inclusion/exclusion criteria identified 89 articles from PubMed, CINAHL and ...EMBASE databases. Meta‐analyses performed for categories of breastfeeding and allergic outcomes. Meta‐regression explored heterogeneity.
Results
More vs. less breastfeeding (duration) was associated with reduced risk of asthma for children (5–18 years), particularly in medium‐/low‐income countries and with reduced risk of allergic rhinitis ≤5 years, but this estimate had high heterogeneity and low quality. Exclusive breastfeeding for 3–4 months was associated with reduced risk of eczema ≤2 years (estimate principally from cross‐sectional studies of low methodological quality). No association found between breastfeeding and food allergy (estimate had high heterogeneity and low quality). Meta‐regression found differences between study outcomes may be attributable to length of breastfeeding recall, study design, country income and date of study inception. Some of the protective effect of breastfeeding for asthma may be related to recall bias in studies of lesser methodological quality.
Conclusion
There is some evidence that breastfeeding is protective for asthma (5–18 years). There is weaker evidence for a protective effect for eczema ≤2 years and allergic rhinitis ≤5 years of age, with greater protection for asthma and eczema in low‐income countries.
A sulfur/carbon composite has been prepared to serve as a cathode for lithium/sulfur batteries. The effects of seven different liquid electrolytes on the electrochemical performance were investigated ...using galvanostatic discharge–charge tests on coin cells. The electrolytes included ether, sulfone, and carbonate solvents with common lithium salts. It was found that the solvent plays a key role on the electrochemical performance of the lithium/sulfur battery cathode while the lithium salt has no significant effects. Additional characterization, using in situ sulfur K-edge X-ray absorption spectroscopy (XAS), provided insights into the soluble sulfur species in the discharged and charged batteries. We find that the use of low-viscosity ethereal solvents results in a more complete reduction of soluble polysulfides, while soluble polysulfides remained more oxidized in viscous ethereal solvents. Moreover, XAS revealed that reduced sulfur species chemically react with carbonate-based solvents, making this class of solvents inappropriate for elemental sulfur cathodes of lithium batteries.
Pseudocapacitance is commonly associated with surface or near-surface reversible redox reactions, as observed with RuO2·xH2O in an acidic electrolyte. However, we recently demonstrated that a ...pseudocapacitive mechanism occurs when lithium ions are inserted into mesoporous and nanocrystal films of orthorhombic Nb2O5 (T-Nb2O5; refs 1,2). Here, we quantify the kinetics of charge storage in T-Nb2O5: currents that vary inversely with time, charge-storage capacity that is mostly independent of rate, and redox peaks that exhibit small voltage offsets even at high rates. We also define the structural characteristics necessary for this process, termed intercalation pseudocapacitance, which are a crystalline network that offers two-dimensional transport pathways and little structural change on intercalation. The principal benefit realized from intercalation pseudocapacitance is that high levels of charge storage are achieved within short periods of time because there are no limitations from solid-state diffusion. Thick electrodes (up to 40 μm thick) prepared with T-Nb2O5 offer the promise of exploiting intercalation pseudocapacitance to obtain high-rate charge-storage devices.
A
bstract
The extended BMS algebra contains a conformal subgroup that acts on the celestial sphere as SO(1, 3). It is of interest to perform mode expansions of free fields in Minkowski spacetime that ...realize this symmetry in a simple way. In the present work we perform such a mode expansion for massive scalar fields using the unitary principal series representations of SO(1, 3) with a view to developing a holographic approach to gravity in asymptotically flat spacetime. These mode expansions are also of use in studying holography in three-dimensional de Sitter spacetime.
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