Identifying the active sites and intermediates on copper surfaces for electrochemical nitrate reduction to ammonia.

Copper (Cu) is a widely used catalyst for the nitrate reduction reaction (NO3RR), but its susceptibility to surface oxidation and complex electrochemical conditions hinders the identification of active sites. Here, we employed electropolished metallic Cu with a predominant (100) surface and compared it to native oxide-covered Cu. The electropolished Cu surface rapidly oxidized after exposure to either air or electrolyte solutions. However, this oxide was reduced below 0.1 V vs. RHE, thus returning to the metallic Cu before NO3RR. It was distinguished from the native oxide on Cu, which remained during NO3RR. Fast NO3- and NO reduction on the metallic Cu delivered 91.5 ± 3.7% faradaic efficiency for NH3 at -0.4 V vs. RHE. In contrast, the native oxide on Cu formed undesired products and low NH3 yield. Operando shell-isolated nanoparticle-enhanced Raman spectroscopy (SHINERS) analysis revealed the adsorbed NO3-, NO2, and NO species on the electropolished Cu as the intermediates of NH3. Low overpotential NO3- and NO adsorptions and favorable NO reduction are key to increased NH3 productivity over Cu samples, which was consistent with the DFT calculation on Cu(100).

Annual performance evaluation of thermoelectric generator-assisted building-integrated photovoltaic system with phase change material.

Owing to the economic recession due to the Coronavirus disease (COVID-19) pandemic, energy-efficient building retrofitting has been considered as an integrated solution to recover the economy and maintain global greenhouse gas reduction. As part of retrofitting existing building-integrated photovoltaic systems during building renovations, this study evaluated the energy generation potential of a thermoelectric generator-assisted building-integrated photovoltaic system with a phase change material. The combination of a thermoelectric generator and phase change material with photovoltaic systems results in solar cell temperature reduction and additional electricity output owing to the Seebeck effect, increasing the total generated energy from the system. Simulations of the proposed system were performed using MATLAB R2020a, based on transient energy balance equations. The appropriate melting temperature and thickness of the phase change material were derived to maximize the annual electricity generation of the proposed system from simulations of 12 design days in each month. The proposed system with the selected phase change material conditions exhibited a 1.09% annual increase in generation output and 0.91%, -1.32%, 2.25%, and 3.16% generation improvements from spring to winter, compared with the building-integrated photovoltaic system alone. Theoretically, the proposed system is expected to generate 4.47% more energy by minimizing the thermal resistance of the system and improving thermoelectric generator performance.

A new injectable liquid crystal system for one month delivery of leuprolide.

An injectable liquid crystal-forming system (LCFS) was prepared by using sorbitan monooleate (SMO) as a new liquid crystal-forming material for injections, and its potential use of clinically available sustained-release formulation was evaluated. LCFS was prepared using SMO mixed with phosphatidyl choline and tocopherol acetate, and contained 3.75 mg of leuprolide acetate as a monthly dose in 90 µl in liquid form. The semi-solid mesophase was formed from the liquid LCFS when it contacted water. The mesophase showed typical characteristics of the liquid crystalline phase, which was classified as the hexagonal phase. The safety of the LCFS was studied by an in vitro extraction colony assay and by examining the injection site in rats and white rabbits after an autopsy. Both in vitro release test and in vivo pharmacokinetic and pharmacodynamic studies showed a sustained release of leuprolide. When compared with a commercial depot formulation of leuprolide, the LCFS showed a similar AUClast value and significantly reduced initial burst with sufficient suppression of testosterone after subcutaneous injections in rats and dogs. The LCFS can serve as a new type of sustained-release injection formulation for its safety, ease of preparation, and sustained release properties.

Microbial examination of nonheated foods served in feeding programs of elementary schools, Iksan City, Jeonbuk Province, Korea.

More than 90% of elementary school students in Korea have lunch provided by a school feeding program. This study examined nonheated foods, foods in which final ingredients were added after cooking ("heated/nonheated foods"), and desserts for microbial contamination levels and the presence of foodborne pathogens. We obtained a total of 77 food samples belonging to the above three groups from four elementary schools located in Iksan, Jeonbuk, Korea, from June to July 2010. Among the samples, 15% of nonheated foods and 9% of heated/nonheated foods contained > 6 log CFU of aerobic bacteria per g. Unacceptable coliform counts according to Korean national standards (3 log CFU/g) were also observed in 30, 4.5, and 26% of nonheated foods, heated/nonheated foods, and desserts, respectively. The foodborne pathogens Escherichia coli O157:H7, Bacillus cereus, and Cronobacter sakazakii were found in two, one, and two of the total samples, respectively. Detection of E. coli O157:H7 indicates a low level of safety in the school lunches served in Korean elementary schools. To improve food safety, hazard analysis critical control point guidelines should be applied to school food service establishments to lower the microbial risks in foods served to children.

Tumoral acidic extracellular pH targeting of pH-responsive MPEG-poly(beta-amino ester) block copolymer micelles for cancer therapy.

The main objective of this study was to develop and characterize a pH-responsive and biodegradable polymeric micelle as a tumor-targeting drug delivery system. The pH-responsive block copolymer was synthesized by a Michael-type step polymerization of hydrophilic methyl ether poly(ethylene glycol) (MPEG) and pH-responsive and biodegradable poly(beta-amino ester), resulting in an amphiphilic MPEG-poly(beta-amino ester) block copolymer. This copolymer, which formed nano-sized self-assembled micelles under aqueous conditions, could be efficiently (74.5%) loaded with doxorubicin (DOX) using a solvent evaporation method. In an in vitro drug release study, these DOX-loaded polymeric micelles showed noticeable pH-dependent micellization-demicellization behavior, with rapid release of DOX from the micelles in weakly acidic environments (pH 6.4) but very slow release under physiological conditions (pH 7.4). Moreover, due to demicellization, the tumor cell uptake of DOX released from polymeric micelles was much higher at pH 6.4 than at pH 7.4. When in vivo anti-tumor activity of pH-responsive polymeric micelles was evaluated by injecting the DOX-loaded polymeric micelles into B16F10 tumor-bearing mice, these micelles notably suppressed tumor growth and also prolonged survival of the tumor-bearing mice, compared with mice treated with free DOX.