3714 research outputs found
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Design of highly conductive iongel soft solid electrolytes for Li-O2 batteries
No full textLi-O2 batteries show high energy storage potential, but there remain many material challenges that must be solved to fully develop them into a robust technology. The reactivity of the electrolyte against lithium metal as the anode or with oxygen superoxide radicals in the cathode is the main problem that may be alleviated by the use of ionic liquids and solid electrolytes. In this work, iongel solid flexible electrolytes with facile preparation are designed based on five variations of the successful N,N-diethyl-N-methyl-N-(2-methoxyethyl)ammonium bis(trifluoromethanesulfonyl)imide ionic liquid. These iongels show an outstanding ionic conductivity of 7.8 × 10-3 S·cm-1 at 25 °C, excellent performance against lithium metal and reduced dendritic growth, even at a high current density rate of 2 mA·cm-2. Tests on Li-O2 cells show a 100% capacity retention for 25 cycles with limited capacity. Hence, this work provides a plausible pathway to tackle the design of effective lithium protection methods and efficient solid electrolytes for Li-O2 batteries
An update on clinical trials for chemoprevention of human skin cancer
No full textThe pathophysiology of skin cancer is complex, with multiple factors contributing to its development. The proactive treatment of skin cancer has been investigated in the form of chemoprevention of cutaneous malignancies in clinical trials. Chemoprevention is the use of natural or pharmacologic agents that prevent or reverse skin cancer development. Multiple trials have arisen over the past decades to explore the efficacy of specific agents to halt the progression of UV radiation damage. This comprehensive review article aims to assess clinical trials performed with chemopreventive agents for melanoma and nonmelanoma skin cancers. The following compounds were most often used in these trials: nicotinamide, retinoids, polyphenolic antioxidants, COX-2 selective inhibitors, non-steroidal anti-inflammatory drugs, difluoromethylornithine, and 5-fluorouracil. Many agents show promise in their ability to prevent nonmelanoma skin cancer formation, with few melanoma trials demonstrating efficacy. The chemoprevention efforts aimed at skin cancer are complex; current and future trials will be instrumental in identifying therapeutic agents that pose efficacy in halting cancer development and assessing whether long-term administration is tolerable
Use of mHealth for management of hypertension in low and middle-income countries: opportunities and challenges
No full textDespite being the leading cause of global mortality, the hypertension control rate is astonishingly low, particularly in low- and middle-income countries. There is evidence that the mHealth approach is a potential platform for delivering interventions for hypertension management. Our recent study from Nepal also provided strong evidence for reducing blood pressure, improving control rate, and medication adherence. The objective of this paper is to document the real-world experience of designing and implementing a mHealth project in Nepal and relates them with the evidence from other similar Low- and Middle-Income Country (LMIC) settings. We learned that mHealth provides a unique opportunity to bridge the gap between providers and patients, send health education and reminder messages, secure patients' privacy, and make data management easier. We also encountered technological and financial barriers, unclear mHealth policy and guidelines, and low literacy levels, including digital literacy. As many of them are addressable, integrating mHealth provides a promising approach to hypertension management
Enhanced all-climate sodium-ion batteries performance in a low-defect and Na-enriched Prussian blue analogue cathode by nickel substitution
No full textCobalt hexacyanoferrate (CoHCF) is one of the most promising cathode materials for all-climate sodium-ion batteries (SIBs) due to its open three-dimensional (3D) framework structures, high theoretical specific capacity, good voltage platform and almost no Jahn-Teller effects. However, CoHCF still suffers from poor cycling stability and bad rate capability, which is closely related to the huge distortion of frame structure and poor conductivity. In this study, by choosing nickel (Ni) to partially replace cobalt (Co) in the CoHCF lattice, we successfully prepared low-defect and Na-enriched Na2Co0.7Ni0.3[Fe(CN)6] (Co0.7Ni0.3HCF) in chelate and sodium salt-assisted coprecipitation method. Both experiments and first-principles calculations demonstrate that Ni substitution can effectively suppress the lattice distortion during the charging and discharging process of CoHCF. Furthermore, the introduction of Ni increases ion mobility by reducing the ion migration barrier (0.31 eV versus 0.17 eV) and improves the electronic conductivity by reducing the bandgap. It is found that Co0.7Ni0.3HCF exhibits superior electrochemical performance compared with that of CoHCF in a wide temperature range (-30 to 60 °C). At 25 °C, Co0.7Ni0.3HCF delivers a high specific capacity of 142.2 mAh g-1 at 0.2 C, an ultrahigh rate capability with 126.2 mAh g-1 at 5 C and excellent cycling stability with 80.9% capacity retention after 500 cycles at 5 C. Even at -30 °C,Co0.7Ni0.3HCF can provide a high capacity of 109 mAh g-1 without an activation process. This work reveals the great application prospect of PBAs for all-climate SIBs, especially at low temperatures
Use of emerging technologies to help measure fjordic biodiversity and blue carbon: mini-manned submarines and autonomous underwater vehicle swarms
No full textMeaningful protection of global oceans lags far behind that of land and has taken little consideration of climate mitigation potential to date (such as through assessment of blue carbon stocks and change). With the new emphasis on synergistic approaches to the identification and conservation of both carbon- and species- rich habitats, we need much better knowledge of the geography and status of blue carbon habitats beyond coastal wetlands. In subpolar and polar regions, some blue carbon habitats are still emerging and work as negative (mitigating) feedback on climate change, yet remain unprotected despite strong evidence of threat overlap. Scientific research expeditions are gradually increasing our understanding, but appropriate vessels are a limiting factor due to high costs and carbon footprints. Even when available such vessels cannot access all areas (e.g., remote fjords with sills) and may struggle to measure certain aspects of habitats (e.g., steep or vertical surfaces). New technologies and opportunities have advanced to aid some of these problems, and here, two of them are considered, mini-manned submersibles and autonomous underwater vehicles. These two platforms have both become much more available and affordable (through novel partnerships) while also being much more scientifically capable. This technology has the potential to reduce the carbon footprint of science and particularly aid in assessing biology and environment status and change on steep sides, such as fjord walls
Carbon-based materials: adsorptive removal of antibiotics from water
No full textThe contamination generated by multiple antibiotics represents a general concern given its impact at the environmental level, mainly affecting the planet’s soil and water and impacting the development of numerous species. Additionally, a new problem has been triggered in terms of the development of antibiotic-resistance genes in various pathogenic microorganisms generating concern for the health sector in terms of the efficiency of antibiotics in the future. These actual problems and concerns demand efforts and actions to remove or eliminate these contaminants. Multiple alternatives to reduce the impact of antibiotics in water have been carried out, such as advanced oxidation, reverse osmosis, and membrane filtration. However, adsorption techniques have presented more favorable and viable results in which carbon-based materials are an efficient tool to remediate the environment that can take advantage of other alternatives due to their characteristics. This review presents different carbon-based absorptive materials such as biochar, carbon nanotubes, activated carbon, and graphene to remove these contaminants, given their characteristics and favorable results. However, process integration, production, and modification continue to be challenging and require more research and experimentation
P-glycoprotein (ABCB1) - weak dipolar interactions provide the key to understanding allocrite recognition, binding, and transport
No full textP-glycoprotein (ABCB1) is the first discovered mammalian member of the large family of ATP binding cassette (ABC) transporters. It facilitates the movement of compounds (called allocrites) across membranes, using the energy of ATP binding and hydrolysis. Here, we review the thermodynamics of allocrite binding and the kinetics of ATP hydrolysis by ABCB1. In combination with our previous molecular dynamics simulations, these data lead to a new model for allocrite transport by ABCB1. In contrast to previous models, we take into account that the transporter was evolutionarily optimized to operate within a membrane, which dictates the nature of interactions. Hydrophobic interactions drive lipid-water partitioning of allocrites, the transport process’s first step. Weak dipolar interactions (including hydrogen bonding, π-π stacking, and π-cation interactions) drive allocrite recognition, binding, and transport by ABCB1 within the membrane. Increasing the lateral membrane packing density reduces allocrite partitioning but enhances dipolar interactions between allocrites and ABCB1. Allocrite flopping (or reorientation of the polar part towards the extracellular aqueous phase) occurs after hydrolysis of one ATP molecule and opening of ABCB1 at the extracellular side. Rebinding of ATP re-closes the transporter at the extracellular side and expels the potentially remaining allocrite into the membrane. The high sensitivity of the steady-state ATP hydrolysis rate to the nature and number of dipolar interactions, as well as to the dielectric constant of the membrane, points to a flopping process, which occurs to a large extent at the membrane-transporter interface. The proposed unidirectional ABCB1 transport cycle, driven by weak dipolar interactions, is consistent with membrane biophysics
Trapezohedral platinum nanocrystals with high-index facets for high-performance hydrazine electrooxidation
No full textDirect hydrazine fuel cell is a promising portable energy conversion device due to its high energy density and free of carbon emissions. To realize the practical applications, the design of highly efficient electrocatalysts for hydrazine oxidation reaction (HzOR) is crucial. Metal nanocrystals with high-index facets have abundant step sites with reactivity. In this study, we prepared trapezohedral Pt nanocrystals (TPH Pt NCs) enclosed by {311} high-index facets and investigated the catalytic performance for hydrazine oxidation. TPH Pt NCs possess a specific activity of 39.1 mA·cm-2 at 0.20 V, much higher than {111}-faceted octahedral (13.9 mA·cm-2) and {100}-faceted cubic Pt NCs (9.11 mA·cm-2). Meanwhile, TPH Pt NCs also show superior stability. Density functional theory (DFT) calculation indicates that Pt(311) facilitates the deprotonation of N2H4* to N2H3* (the rate-determining step) and improves the HzOR activity. This study is helpful for the design of advanced electrocatalysts for HzOR, especially high-index faceted Pt nanocatalysts
Lithium metal stabilization for next-generation lithium-based batteries: from fundamental chemistry to advanced characterization and effective protection
No full textLithium (Li) metal-based rechargeable batteries hold significant promise to meet the ever-increasing demands for portable electronic devices, electric vehicles and grid-scale energy storage, making them the optimal alternatives for next-generation secondary batteries. Nevertheless, Li metal anodes currently suffer from major drawbacks, including safety concerns, capacity decay and lifespan degradation, which arise from uncontrollable dendrite growth, notorious side reactions and infinite volume variation, thereby limiting their current practical application. Numerous critical endeavors from different perspectives have been dedicated to developing highly stable Li metal anodes. Herein, a comprehensive overview of Li metal anodes regarding fundamental mechanisms, scientific challenges, characterization techniques, theoretical investigations and advanced strategies is systematically presented. First, the basic working principles of Li metal-based batteries are introduced. Specific attention is then paid to the fundamental understanding of and challenges facing Li metal anodes. Accordingly, advanced characterization approaches and theoretical computations are introduced to understand the fundamental mechanisms of dendrite growth and parasitic reactions. Recent key progress in Li anode protection is then comprehensively summarized and categorized to generate an overview of the respective superiorities and limitations of the various strategies. Furthermore, this review concludes the remaining obstacles and potential research directions for inspiring the innovation of Li metal anodes and endeavors to accomplish the practical application of next-generation Li-based batteries
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