Catalytic activity of Cu2O nanoparticles supported on cellulose beads prepared by emulsion-gelation using cellulose/LiBr solution and vegetable oil.

Nanocatalysts tend to aggregate and are difficult to recycle, limiting their practical applications. In this study, an environmentally friendly method was developed to produce cellulose beads for use as supporting materials for Cu-based nanocatalysts. Cellulose beads were synthesized from a water-in-oil emulsion using cellulose dissolved in an LiBr solution as the water phase and vegetable oil as the oil phase. Upon cooling, the gelation of the cellulose solution produced spherical cellulose beads, which were then oxidized to introduce surface carboxyl groups. These beads (diameter: 95-105 µm; specific surface area: 165-225 m2 g-1) have a three-dimensional network of nanofibers (width: 20-30 nm). Furthermore, the Cu2O nanoparticles were loaded onto oxidized cellulose beads before testing their catalytic activity in the reduction of 4-nitrophenol using NaBH4. The apparent reaction rate constant increased with increasing loading of Cu2O nanoparticles and the conversion efficiency was >90 %. The turnover frequency was 376.2 h-1 for the oxidized cellulose beads with the lowest Cu2O loading, indicating a higher catalytic activity compared to those of other Cu-based nanoparticle-loaded materials. In addition to their high catalytic activity, the cellulose beads are reusable and exhibit excellent stability.

Deposition of Lead Phosphate by Lead-Tolerant Bacteria Isolated from Fresh Water near an Abandoned Mine.

Specialist bacteria can synthesize nanoparticles from various metal ions in solution. Metal recovery with high efficiency can be achieved by metal-tolerant microorganisms that proliferate in a concentrated metal solution. In this study, we isolated bacteria (Pseudomonas sp. strain KKY-29) from a bacterial library collected from water near an abandoned mine in Komatsu City, Ishikawa Prefecture, Japan. KKY-29 was maintained in nutrient medium with lead acetate and synthesized hydrocerussite and pyromorphite nanoparticles inside the cell; KKY-29 also survived nanoparticle synthesis. Quantitative PCR analysis of genes related to phosphate metabolism showed that KKY-29 decomposed organic phosphorus to synthesize lead phosphate. KKY-29 also deposited various metal ions and synthesized metal nanoparticles when incubated in various metal salt solutions other than lead. The present study considers the development of biotechnology to recover lead as an economically valuable material.

Avoidable Serum Potassium Testing in the Cardiac ICU: Development and Testing of a Machine-Learning Model.

OBJECTIVES: To create a machine-learning model identifying potentially avoidable blood draws for serum potassium among pediatric patients following cardiac surgery. DESIGN: Retrospective cohort study. SETTING: Tertiary-care center. PATIENTS: All patients admitted to the cardiac ICU at Boston Children's Hospital between January 2010 and December 2018 with a length of stay greater than or equal to 4 days and greater than or equal to two recorded serum potassium measurements. INTERVENTIONS: None. MEASUREMENTS AND MAIN RESULTS: We collected variables related to potassium homeostasis, including serum chemistry, hourly potassium intake, diuretics, and urine output. Using established machine-learning techniques, including random forest classifiers, and hyperparameter tuning, we created models predicting whether a patient's potassium would be normal or abnormal based on the most recent potassium level, medications administered, urine output, and markers of renal function. We developed multiple models based on different age-categories and temporal proximity of the most recent potassium measurement. We assessed the predictive performance of the models using an independent test set. Of the 7,269 admissions (6,196 patients) included, serum potassium was measured on average of 1 (interquartile range, 0-1) time per day. Approximately 96% of patients received at least one dose of IV diuretic and 83% received a form of potassium supplementation. Our models predicted a normal potassium value with a median positive predictive value of 0.900. A median percentage of 2.1% measurements (mean 2.5%; interquartile range, 1.3-3.7%) was incorrectly predicted as normal when they were abnormal. A median percentage of 0.0% (interquartile range, 0.0-0.4%) critically low or high measurements was incorrectly predicted as normal. A median of 27.2% (interquartile range, 7.8-32.4%) of samples was correctly predicted to be normal and could have been potentially avoided. CONCLUSIONS: Machine-learning methods can be used to predict avoidable blood tests accurately for serum potassium in critically ill pediatric patients. A median of 27.2% of samples could have been saved, with decreased costs and risk of infection or anemia.

Reduction of Fe(III) oxides by phylogenetically and physiologically diverse thermophilic methanogens.

Three thermophilic methanogens (Methanothermobacter thermautotrophicus, Methanosaeta thermophila, and Methanosarcina thermophila) were investigated for their ability to reduce poorly crystalline Fe(III) oxides (ferrihydrite) and the inhibitory effects of ferrihydrite on their methanogenesis. This study demonstrated that Fe(II) generation from ferrihydrite occurs in the cultures of the three thermophilic methanogens only when H2 was supplied as the source of reducing equivalents, even in the cultures of Mst. thermophila that do not grow on and produce CH4 from H2/CO2. While supplementation of ferrihydrite resulted in complete inhibition or suppression of methanogenesis by the thermophilic methanogens, ferrihydrite reduction by the methanogens at least partially alleviates the inhibitory effects. Microscopic and crystallographic analyses on the ferrihydrite-reducing Msr. thermophila cultures exhibited generation of magnetite on its cell surfaces through partial reduction of ferrihydrite. These findings suggest that at least certain thermophilic methanogens have the ability to extracellularly transfer electrons to insoluble Fe(III) compounds, affecting their methanogenic activities, which would in turn have significant impacts on materials and energy cycles in thermophilic anoxic environments.

"All-in-One Assay", a direct phenotypic anti-human immunodeficiency virus type 1 drug resistance assay for three-drug combination therapies that takes into consideration in vivo drug concentrations.

A novel phenotypic anti-human immunodeficiency virus type 1 (HIV-1) drug resistance assay is described. Three drugs at concentrations equivalent to those determined in in vivo pharmacokinetics, were mixed in a well, serially diluted by 10-folds, and added to incubations of clinical HIV-1 isolates and CCR-5 expressing HeLa/CD4+ cells which was previously reported as the MAGIC-5 cells (Antimicrob. Agents Chemother. 45 (2001) 495) to determine the 95% inhibitory dilution (ID(95)) of the combination regimens. The ID(95) of efavirenz (EFV)-containing regimens was ten-times lower than that of nevirapine (NVP)-containing regimens against HIV-1 isolated from antiviral therapy naive patients. However, the difference was not apparent by the conventional fold resistance measurement based on the 50% inhibitory concentration. Furthermore, the synergistic effects of drug combinations against clinical HIV-1 isolates can be evaluated by our assay. The ID(95)s of EFV- and nelfinavir (NFV)- containing regimens against HIV-1 from naive patients were less than 0.01 whereas those against resistant viruses were over 0.05, although the clinical cut-off values are to be determined in larger clinical studies. Our assay, designated "All-in-One Assay", that can examine resistance to three drugs simultaneously under consideration of in vivo drug concentrations described above might be useful in practice.