Enamel demineralization is a very common occurrence around bonded brackets in an orthodontic practice. Fluoride (FLR) applications have been used to prevent decalcification and further progression of white spot lesions. The purpose of this systematic review and meta-analysis was to systematically appraise available literature on the effectiveness of fluoride mouthrinse in the prevention of demineralization around fixed orthodontic appliances. A search was conducted for randomized controlled clinical trials among four electronic databases (MEDLINE, Google Scholar, PubMed, and Cochrane Review) through MeSH terms and keywords. Studies were excluded if random allocation was not conducted, or if they were animal or in vitro studies. About 146 articles were screened and 5 studies were selected for the present review. Only two studies were selected for MA due to variations in the measurement of outcomes among studies. This review concluded that rinsing with FLR in the course of the fixed orthodontic treatment lessens demineralization around the bracket. Using FLR mouthrinse to inhibit the formation of white spot lesions or dental caries in patients with multiple cavities or restoration can be considered in clinical practice.
The discharge products of charge–discharge reactions of Na–O2 cells are extensively studied by various physicochemical techniques and verified experimentally.
MgCoSiO4is synthesized by using mixed solvothermal approach and studied for oxygen evolution (OER) and reduction (ORR) reactions. It is also studied for non-aqueous Li–O2cells.
A metal-air battery functions involving the principles of both batteries and fuel cells. The anode of a metal–air cell is stored inside the cell and O 2 for the air-electrode is supplied either from atmosphere or a tank. Zinc-air cells are commercially successful. In recent years, research activities on rechargeable Li-air cells have become intense due to their anticipated high energy density, which is close to specific energy of gasoline. Development of rechargeable Li-air cells involves several issues related to the negative Li electrode, the positive O 2 electrode as well as the electrolyte. Among these problems, studies on rechargeable O 2 electrode kinetics in non-aqueous electrolytes are important. Development of an appropriate catalyst, which allows both O 2 reduction and its evolution with fast kinetics and high efficiency, is a challenging problem. Reduced graphene oxide (RGO) and its composites have emerged as important materials for energy storage systems because of high electronic conductivity and high surface area of RGO. In the present study, graphite is converted to graphite oxide by Hummer’s method and converted to graphene oxide by ultra-sonication. Graphene oxide is chemically reduced to RGO by NaBH 4 . Au-RGO is also prepared by a similar route. RGO and Au-RGO are characterized by physicochemical studies. Au nanoparticles of average size of 5.2 nm are distributed uniformly over RGO sheets (Figure: 1). Further characterization studies of RGO and Au-RGO are carried out by powder XRD, UV-Visible, Raman spectroscopy and XPS. Li-O 2 (RGO) and Li-O 2 (Au-RGO) cells are assembled in Ar atmosphere using Li foil as the negative electrode, the catalyst coated carbon paper as the positive electrode and 1.0 M LiPF 6 dissolved in TEGDME as the electrolyte. A glass absorbing mat is used as the separator. Typical charge-discharge curves of Li-O 2 (RGO) and Li-O 2 (Au-RGO) are shown in Fig. 2. The discharge capacities obtained for the first discharge are 956 and 1738 mAh g -1 , respectively, for Li-O 2 (RGO) and Li-O 2 (Au-RGO) cells at a discharge current of 0.2 mA cm -2 . Li-O 2 (Au-RGO) cells are cycled at 0.6 mA cm -2 over about 120 charge-discharge cycles. Although about 1500 mAh g -1 discharge capacity is obtained for the cycle, there is a rapid decrease of capacity in the initial stages of cycling, and then there is a gradual decrease. Discharge capacity of about 500 mAh g -1 is obtained for the 120th cycle. The moderate stability of the Li-O 2 (Au-RGO) cells is attributed to nanoparticles of Au, which are uniformly distributed on RGO sheets. Powder XRD pattern of Au-RGO catalyst used for cycling of Li-O 2 (Au-RGO) cells indicate the presence of Li 2 O and Li 2 O 2 , which are the products of oxygen reduction in the non-aqueous electrolyte. Results of these investigations will be presented. Reference: 1. K. M. Abraham and Z. Jiang, J. Electrochem. Soc., 1996, 143 , 1-5. 2.Yi-Chun Lu, B. M. Gallant, D. G. Kwabi, J. R. Harding, R. R. Mitchell, M. S. Whittingham and Y. Shao-Horn, Energy Environ. Sci., 2013, 6 , 750-768. 3. S. Kumar, C. Selvaraj, N. Munichandraiah and L. G. Scanlon RSC Adv.,2013, 3 , 21706-21714.
Abstract Pd +2 ions are reduced on two‐dimensional reduced graphene oxide nanosheets in aqueous phase by NaBH 4 as reducing agent. Pd nanoparticles are uniformly grown on graphene sheets in 5–15 nm range, verified by TEM investigation. Oxygen reduction reaction (ORR) is carried in nonaqueous medium by using rotating disk electrode technique. For comparison, ORR activity of pure RGO is also studied; ORR follows one e− pathway (O 2 + e−=O2−) in non‐aqueous electrolyte. Pd‐RGO has ORR activity five times more as compared to pure RGO in 0.10 M TBAP‐DMSO solution. Pd‐RGO catalyst is used to assemble the non‐aqueous Li‐O 2 batteries and charge‐discharge cycling is carried out. At 0.20 mA cm−2 the discharge capacity of 8192 mAh g−1 is obtained. Overpotential for ORR (or discharge) step is 260 mV. This is first report on reaction chemistry in Li‐O 2 battery using Pd nanoparticles. Li 2 O 2 and Li 2 O are confirmed as discharged products by ex‐situ XRD studies.
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