Influence of Ion Diffusion on the Lithium-Oxygen Electrochemical Process and Battery Application Using Carbon Nanotubes-Graphene Substrate

Lithium-oxygen (Li-O2) batteries are nowadays among the most appealing next-generation energy storage systems in view of a high theoretical capacity and the use of transition-metal-free cathodes. Nevertheless, the practical application of these batteries is still hindered by limited understanding of the relationships between cell components and performances. In this work, we investigate a Li-O2 battery by originally screening different gas diffusion layers (GDLs) characterized by low specific surface area (<40 m2 g-1) with relatively large pores (absence of micropores), graphitic character, and the presence of a fraction of the hydrophobic PTFE polymer on their surface (<20 wt %). The electrochemical characterization of Li-O2 cells using bare GDLs as the support indicates that the oxygen reduction reaction (ORR) occurs at potentials below 2.8 V vs Li+/Li, while the oxygen evolution reaction (OER) takes place at potentials higher than 3.6 V vs Li+/Li. Furthermore, the relatively high impedance of the Li-O2 cells at the pristine state remarkably decreases upon electrochemical activation achieved by voltammetry. The Li-O2 cells deliver high reversible capacities, ranging from ∼6 to ∼8 mA h cm-2 (referred to the geometric area of the GDLs). The Li-O2 battery performances are rationalized by the investigation of a practical Li+ diffusion coefficient (D) within the cell configuration adopted herein. The study reveals that D is higher during ORR than during OER, with values depending on the characteristics of the GDL and on the cell state of charge. Overall, D values range from ∼10-10 to ∼10-8 cm2 s-1 during the ORR and ∼10-17 to ∼10-11 cm2 s-1 during the OER. The most performing GDL is used as the support for the deposition of a substrate formed by few-layer graphene and multiwalled carbon nanotubes to improve the reaction in a Li-O2 cell operating with a maximum specific capacity of 1250 mA h g-1 (1 mA h cm-2) at a current density of 0.33 mA cm-2. XPS on the electrode tested in our Li-O2 cell setup suggests the formation of a stable solid electrolyte interphase at the surface which extends the cycle life.

X-ray Nano-computed Tomography of Electrochemical Conversion in Lithium-ion Battery

Herein, a nanometric CuO anode for lithium-ion batteries was investigated by combining electrochemical measurements and ex situ X-ray computed tomography (CT) at the nanoscale. The electrode reacted by conversion at about 1.2 and 2.4 V versus Li⁺ /Li during discharge and charge, respectively, to deliver a capacity ranging from 500 mAh g^-1 to over 600 mAh g^-1 . Three-dimensional nano-CT imaging revealed substantial reorganization of the CuO particles and precipitation of a Li⁺ -conducting film suitable for a possible application in the battery. A lithium-ion cell, exploiting the high capacity of the conversion process, was assembled by using a high-performance LiNi_0.33 Co_0.33 Mn_0.33 O₂ cathode reacting at 3.9 V versus Li⁺ /Li. The cell was proposed as an energy-storage system with an average working voltage of about 2.5 V, specific capacity of 170 mAh g_cathode ^-1 , and efficiency exceeding 99 % with a very stable cycling.

The effect of foliar fertilizing on ecological optimization of the application of fungicides on the productivity and phenolic complex composition of grapes

One of the ways to reduce the pesticidal burden in mature ampelocenoses is the use of foliar bio-preparations of multifunctional action. We studied the influence of growth bioregulators “Albit” and “Mival-Agro” at reduced by 25–50% fungicidal load on productivity and phenolic complex composition (using the HPLC method) of Vitis vinifera “Asma” (Crimean autochthonous table cultivar), “Cabernet Sauvignon” and table grapes of complex genetic structure “Moldova”, grown in the mountain-valley seaside region of Crimea. It was established that bio-regulators increase the harvest of grapes, especially in the first and third years of treatment, depending on the preparation and grape cultivar, by 27–64% and 24–29%, respectively, as compared to control; the bunch weight increased by 134 ± 41%. The first two years of treatment enhance sugar accumulation in berries by 0.7–2.6 Brix. “Albit” preparation proved to be more effective as compared to “Mival-Agro”. The use of “Albit” on “Moldova” and “Cabernet Sauvignon” grapes increased components content in the berries by 19%–88% relative to control, depending on the cultivar and year of treatment, of which: anthocyanins – by 23–83%, stilbenes – by 24–138%. Regardless of treatment, the anthocyanin complex consisted by 75–87% of malvidin monoglucosides in “Cabernet Sauvignon” and “Asma”; 22–56% of malvidin monoglucosides and 21–62% of malvidin diglucoside in “Moldova”. The studied preparations had no significant impact on the quality of wines from “Cabernet Sauvignon”, however, they improved the quality of table grapes and their preservation capacity during storage.

Facile Modification of Reverse Osmosis Membranes by Surfactant-Assisted Acrylate Grafting for Enhanced Selectivity

The top polyamide layer of composite reverse osmosis (RO) membranes has a fascinatingly complex structure, yet nanoscale nonuniformities inherently present in polyamide layer may reduce selectivity, e.g., for boron rejection. This study examines improving selectivity by in situ "caulking" such nonuniformities using concentration polarization-enhanced graft-polymerization with a surfactant added to the reactive solution. The surfactant appears to enhance both polarization (via monomer solubilization in surfactant micelles) and adherence of graft-polymer to the membrane surface, which facilitates grafting and reduces monomer consumption. The effect of surfactant was particularly notable for a hydrophobic monomer glycidyl methacrylate combined with a nonionic surfactant Triton X-100. With Triton added at an optimal level, close to critical micellization concentration (CMC), monomer gets solubilized and highly concentrated within micelles, which results in a significantly increased degree of grafting and uniformity of the coating compared to a procedure with no surfactant added. Notably, no improvement was obtained for an anionic surfactant SDS or the cationic surfactant DTAB, in which cases the high CMC of surfactant precludes high monomer concentration within micelles. The modification procedure was also up-scalable to membranes elements and resulted in elements with permeability comparable to commercial brackish water RO elements with superior boric acid rejection.

Factors associated with clear biopsy margins and clear reexcision margins in breast cancer specimens from candidates for breast conservation

BACKGROUND

The aim of this study was to identify variables associated with clear biopsy margins and clear reexcision margins of breast cancer specimens from patients who are candidates for breast conservation.

STUDY DESIGN

The records of breast cancer patients were reviewed to identify candidates considered for breast conservation after biopsy. Factors associated with obtaining histopathologically clear excisional biopsy margins and clear reexcision margins were studied in 674 excisional biopsy specimens and in 197 reexcision specimens.

RESULTS

Clear biopsy margins were associated with older patient age (p = 0.0446), family history of breast cancer (p = 0.0008), diagnosis by fine needle aspiration (p = 0.0000), small tumor size (p = 0.0010), absence of ductal carcinoma in situ (p = 0.0004), and absence of extensive intraductal carcinoma (p = 0.0117). In multivariate analysis, only diagnosis by fine needle aspiration and small tumor size were associated with clear biopsy margins. Clear margins in reexcision specimens were associated with small tumor size (p = 0.0086), close or unknown biopsy margins (p = 0.0003), and absence of nodal involvement (p = 0.0014). In multivariate analysis only biopsy margin status and node status were associated with clear reexcision margins.

CONCLUSIONS

These data indicate that obtaining clear biopsy margins is facilitated by small tumor size and by having a preoperative diagnosis by fine needle aspiration. The majority of patients undergoing reexcision will have clear margins although this is significantly less likely when the biopsy margins are involved or when nodal involvement is present.