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Electrochemical ammonia removal and disinfection of aquaculture wastewater using batch and flow reactors incorporating PtRu/graphite anode and graphite cathode

Ammonia removal and disinfection are two major problems in aquaculture systems, which require clean and reliable water to support long-term growth and health of target animals. In this study, we report electrochemical ammonia removal and disinfection of wastewater from an aquaculture farm (Mari’s Gardens) in Hawaii. First, we attempted to reproduce the work of Zollig and co-authors, who reported that direct ammonia oxidation can occur between 1 V and 1.6 V vs SHE on a graphite electrode in a solution (pH = 9.0) containing 1 M NaClO4, 0.25 M NH4ClO4, and 0.085 M NaCl. Our results, however, show that direct ammonia oxidation is unlikely to occur, at least at significant rates, on a graphite electrode in aqueous solutions (pH = 9.0) containing 0.7 M Na2SO4, 0.1 M (NH4)2SO4, and 0.02 M NaCl. We tentatively attribute this discrepancy to the different physico-chemical characteristics of graphite electrodes made by different manufacturers. Second, PtRu/graphite electrodes were prepared using a pulsed electrodeposition method, and electrode activity towards ammonia removal and disinfection was examined in both synthetic and real aquaculture wastewater using batch and flow reactors. The PtRu catalyst was partially oxidized at the beginning of electrolysis, and a significant increase in the electrode activity towards indirect ammonia oxidation was observed. Ammonia removal was slow when NaCl concentration was 0.66 mM, but the addition of NaCl (up to 20 mM) led to a drastic increase in the ammonia removal rate, indicating that ammonia removal proceeds via indirect oxidation. The ammonia removal rate depends primarily on NaCl concentration and current density and is independent of the initial ammonia concentration and solution pH. The ammonia removal rates can be modeled by pseudo zero-order kinetics, and a linear correlation can be drawn between the ammonia removal rate (k, mg L−1 min−1) and the product of NaCl concentration ([Cl-], mM) and current density (j, mA/cm2): k = 0.0047 [Cl-] j (R2 = 0.99). Free chlorine (Cl2, HOCl, and OCl-) was not detected in the solution until the complete removal of ammonia. Combined chlorine (NH2Cl, NHCl2, and NCl3) was measured at concentrations of 2–15 mg/L (as Cl2) during the ammonia removal process but was eliminated as soon as ammonia was depleted and an excess of free chlorine was available. Our detailed findings on the formation of both free chlorine and combined chlorine are significant to the mechanistic study of indirect ammonia oxidation. Ammonia removal experiments in synthetic and real aquaculture wastewater showed similar results. However, ammonia removal in the flow reactor took about three times longer than that in the batch reactor under similar conditions, likely due to hydrodynamic mixing differences. In addition, it was found that E. coli bacteria can be completely inactivated (5-log reduction) within a short time (e.g., 5 min).

Aquacultural Engineering EI,SCI,SCIE | 2021 | 93

Laser performance of diode-pumped continuous-wave Nd:CaLaGa3O7 laser with a 22-nm wavelength tunability

We report on the laser performance of diode-pumped continuous-wave Nd:CaLaGa3O7 laser after registering the polarized absorption and emission spectra, for the first time to our knowledge. A maximum output power of 1.45 W is reached at 1061.7 nm and 1067.8 nm with a slope efficiency of about 27.7% with respect to the absorbed power. Wavelength tuning is also realized with a range of about 22 nm using an intracavity un-doped YAG etalon. The broadband Nd3+-doped crystal could be very promising for ultrashort pulse laser generation in femtosecond time duration through mode locking technology.

Optical Materials EI,SCI,SCIE | 2021 | 115

Tube-load model: A clinically applicable pulse contour analysis method for estimation of cardiac stroke volume

Background and Objectives: Accurate, reproducible, and reliable real-time clinical measurement of stroke volume (SV) is challenging. To accurately estimate arterial mechanics and SV by pulse contour analysis, accounting for wave reflection, such as by a tube-load model, is potentially important. This study tests for the first time whether a dynamically identified tube-load model, given a single peripheral arterial input signal and pulse transit time (PTT), provides accurate SV estimates during hemodynamic instability.Methods: The model is tested for 5 pigs during hemodynamic interventions, using either an aortic flow probe or admittance catheter for a validation SV measure. Performance is assessed using Bland-Altman and polar plot analysis for a series of long-term state-change and short-term dynamic events.Results:The overall median bias and limits of agreement (2.5th, 97.5th percentile) from Bland-Altman analysis were -10% [-49, 36], and -1% [-28,20] for state-change and dynamic events, respectively. The angular limit of agreement (maximum of 2.5th, 97.5th percentile) from polar-plot analysis for state-change and dynamic interventions was 35.6∘, and 35.2∘, respectively.Conclusion: SV estimation agreement and trending performance was reasonable given the severity of the interventions. This simple yet robust method has potential to track SV within acceptable limits during hemodynamic instability in critically ill patients, provided a sufficiently accurate PTT measure.

Comput Methods Programs Biomed EI,SCI,SCIE | 2021 | 204

Molecular dynamics simulations of choline chloride and phenyl propionic acid deep eutectic solvents: Investigation of structural and dynamics properties

The prediction of deep eutectic composition is hard and so far, has been distinguished by trial and error. Therefore, in this work, molecular dynamics simulations were performed for specifying the composition of the eutectic point of phenyl propionic acid (Phpr) and choline chloride (ChCl) mixtures. The distinctive properties of the Phpr and ChCl eutectic mixture at the composition of the eutectic point were investigated and were compared to other eutectic mixtures with the different mole fractions of Phpr and ChCl. Structural properties such as radial distribution function (RDF), coordination number, hydrogen-bond number, interaction energies, and dipole moment of species, as well as dynamical properties such as mean square displacement (MSD), viscosity, and self-diffusion coefficient were analyzed. The obtained results of structural properties indicated that each chloride anion is surrounded by two Phpr molecules for deep eutectic point states that is in good agreement with available experimental reports. Moreover, the viscosity of studied mixtures evaluated by the Green-Kubo method was found to be consistent with the reported experimental data. Besides, the stress-autocorrelation function (SACF) and convergency of viscosity with time were calculated. Finally, the eutectic point could be detected by the changes in the trends of total van der Waals interaction energies and the viscosity.

Journal of Molecular Graphics and Modelling EI,SCI,SCIE | 2021 | 106

Variants in HSD11B1 gene modulate susceptibility to diabetes kidney disease and to insulin resistance in type 1 diabetes

Background and aim 11β‐Hydroxysteroid dehydrogenase 1 has been implicated in insulin resistance (IR) in the setting of metabolic disorders, and single nucleotide polymorphisms (SNPs) in its encoding gene (HSD11B1) have been associated with type 2 diabetes and metabolic syndrome. In type 1 diabetes (T1D), IR has been related to the development of chronic complications. We investigated the association of HSD11B1 SNPs with microvascular complications and with IR in a Brazilian cohort of T1D individuals. Materials and methods Five SNPs were genotyped in 466 T1D individuals (57% women; median of 37 years old, diabetes duration of 25 years and HbA1c of 8.4%). Results The minor allele T of rs11799643 was nominally associated with diabetic retinopathy (OR = 0.52; confidence interval [CI] 95% = 0.28‐0.96; P = .036). The minor allele C of rs17389016 was nominally associated with overt diabetic kidney disease (DKD) (OR = 1.90; CI 95% = 1.07‐3.37; P = .028). A follow‐up study revealed that 29% of the individuals lost ≥5 mL min−1 × 1.73 m2 per year of the estimated glomerular filtration rate (eGFR). In these individuals (eGFR decliners), C allele of rs17389016 was more frequent than in non‐decliners (OR = 2.10; CI 95% = 1.14‐3.89; P = .018). Finally, minor allele T of rs846906 associated with higher prevalence of arterial hypertension, higher body mass index and waist circumference, thus conferring risk to a lower estimated glucose disposal rate, a surrogate marker of insulin sensitivity (OR = 1.23; CI 95% = 1.06‐1.42; P = .004). Conclusion SNPs in the HSD11B1 gene may confer susceptibility to DKD and to IR in T1D individuals.

DIABETES/METABOLISM RESEARCH AND REVIEWS SCI,SCIE | 2021 | 37 (1)