Search

The massive worldwide use of antibiotics leads to water pollution and increasing microbial resistance. Hence, the removal of antibiotic residues is a key issue in water remediation. Here, we report the solar light-assisted oxidative degradation of ciprofloxacin (CPF), using H2O2 in aqueous solution, catalyzed by iron(III) chelated cross-linked chitosan (FeIII-CS-GLA) immobilized on a glass plate. The FeIII-CS-GLA catalyst was characterized by FTIR and 57Fe-Mössbauer spectroscopies as well as X-ray diffraction, revealing key structural motifs and a high-spin ferric character of the metal. Catalytic degradation of CPF was investigated as a function of solar light irradiation time, solution pH, concentration of H2O2 and CPF, as well as cross-linker dosage and iron(III) content in FeIII-CS-GLA. The system was found to serve as an efficient catalyst with maximum CPF degradation at pH 3. The specific ·OH scavenger mannitol significantly reduces the degradation rate, indicating that hydroxyl radicals play a key role. The mechanism of catalytic CPF degradation was evaluated in terms of pseudo-first-order and Langmuir-Hinshelwood kinetic models; adsorption of CPF onto the FeIII-CS-GLA surface was evidenced by field emission scanning electron microscopy coupled with energy dispersive X-ray spectroscopy. FeIII-CS-GLA can be reused multiple times with only minor loss of catalytic efficiency. Antimicrobial activity tests performed against both Gram-negative (Escherichia coli DH5α, Salmonella typhi AF4500) and Gram-positive bacteria (Bacillus subtilis RBW) before and after treatment confirmed complete degradation of CPF. These results establish the immobilized FeIII-CS-GLA as a rugged catalyst system for efficient photo-Fenton type degradation of antibiotics in aqueous solutions. [ABSTRACT FROM AUTHOR]

Textile and food industries produce a significant volume of effluents containing azo dyes and other pollutants. These effluents are serious environmental threats, and new methods for their treatment and for the degradation of azo dyes are thus attracting much attention. The current study deals with the oxidative degradation of azo dyes by meso‐tetrakis(1‐methylpyridinium‐4‐yl)prophyrinatoiron(III), [FeIII(tmpyp)], and meta‐chloroperoxy benzoic acid (m‐CPBA) in aqueous solution at room temperature. The catalytic degradation of azo dyes was investigated by using rapid‐scan stopped‐flow spectrophotometry as a function of solution pH, [catalyst], [m‐CPBA], [dye] and [surfactants]. To obtain mechanistic insight, the reaction between [FeIII(tmpyp)] and m‐CPBA was also studied in aqueous solution in absence of azo dyes. Spectral analyses and kinetic data show that [FeIII(tmpyp)] is transformed into the transient intermediate [FeIV(O)(tmpyp)].+ (a compound I analog) within 20–30 ms followed by the formation of relatively stable [FeIV(O)(tmpyp)] (a compound II analog). Batch experiments reveal that the dye degradation rate is influenced by the solution pH and the concentrations of [FeIII(tmpyp)], m‐CPBA, dye, and surfactants. On the basis of the kinetic and spectroscopic data, a mechanistic scheme for the dye degradation reaction and a steady‐state rate equation are proposed. The products resulting from oxidative degradation of the azo dye amaranth have been analyzed by HPLC‐UV‐HRMS. [ABSTRACT FROM AUTHOR]

Background: Dye-binding assays - bromocresol green (BCG) and bromocresol purple (BCP) -are widely used for serum albumin measurement. Differences between the results reported by these assays can have important clinical implications. There are limited studies elucidating the differences between the results of two assays in HIV patients. We aimed to determine whether the choice of assay affects serum albumin measurements in HIV patients. Materials and Methods: Hundred newly diagnosed HIV patients were included in the study. The subjects were followed up for 6-12 months after initiating ART. Hundred HIV-negative healthy controls matched for age and body mass index were taken as controls. Serum albumin and three acute phase proteins (APPs) (Alpha-1 acid glycoprotein, C-reactive protein, ceruloplasmin) were measured. Serum albumin measurement was done by both BCG and BCP dye binding methods. Paired t-test was used to compare the groups. Results: The concentration of APPs reduces with ART indicating reduced inflammation, and is lowest in the control group. The difference in serum albumin concentrations measured by the two dye binding methods reduces with reduction in APPs. The study further indicates that the BCG method gives higher values of serum albumin as compared to BCP method in the presence of other proteins in the sample. Conclusion: The choice of albumin assay affects the serum albumin assessment of HIV patients. We recommend that the BCP assay be used to measure serum albumin in HIV patients, particularly in patients not on ART. [ABSTRACT FROM AUTHOR]

• A semi-analytical approach is developed to obtain the BESS power reserve for FFR. • The local minimum power reserve is derived to avoid UFLS under a large contingency. • The proposed method bridges the gap of the trial-and-error approaches. • The effectiveness of the proposed method is validated with an actual network model. • The methodology will advance grid services estimation and battery management. The large-scale renewable energy integration faces a challenge of frequency stability due to low inertia in weak power grids. One solution to mitigate this issue is via the fast frequency response service provided by battery storage systems so that the overall grid response during a large power outage can be improved. The battery power reserve is crucial to ensure the frequency ancillary services provision. However, grid operators currently investigate the contingency reserve of batteries through inefficient processes, such as extensive simulations or trial-and-error methods. Therefore, this paper proposes a semi-analytical methodology to quantitively determine the minimum required battery power reserve for preventing under-frequency load shedding when a severe generation trip occurs. This minimum reserve is derived from the time-variant kinetic energy of a given dispatch case. Case study results of the Mexican network demonstrate that the calculated battery power reserve can provide a cost-effective fast frequency response for a real islanded network. The research outcomes offer valuable insights for battery management and grid ancillary services requirement estimation in the transition to power networks dominated by converter-interfaced renewable energy resources. [ABSTRACT FROM AUTHOR]

Partial discharge inception voltage (PDIV) at different frequencies is of great interest for PD tests conducted at nonpower frequency. However, in the existing literature, there is no agreement on PDIV characteristics with respect to frequency. There is a lack of comprehensive analysis of frequency-dependent PDIV characteristics either. In this article, the PDIV of a cylindrical void at different frequencies (from 0.5 to 300 Hz) is investigated from the perspective of the first PD time lag. First, an appropriate time interval between consecutive measurements is experimentally determined. Then, PDIV measurements at different frequencies are conducted by increasing voltage at a fixed ramp rate. Furthermore, the PDIVs defined by peak voltage and instantaneous voltage are compared. After that, a bipolar square wave is applied to measure the first PD time lag. Finally, based on the first PD time-lag distribution with respect to voltage at different frequencies, the cumulative probability of the first PD under sinusoidal voltage is computed and analyzed. The results suggest that the first PD time lag has a significant influence on the measured PDIV at frequencies above 10 Hz. This is because the mean time lag is nearly half the time period of half voltage cycle at low voltages. Thus, high voltages (HVs) are needed to obtain a high probability of the first PD, i.e., a large measured PDIV. [ABSTRACT FROM AUTHOR]

• A two-stage security-constrained economic dispatch model is proposed to exploit the inherent grid flexibility. • A joint chance constraints-based method is developed to efficiently utilize dynamic line rating while handling its uncertainty. • The post-outage setpoint adjustments of flexible ac transmission systems are extended from N-1 to N-K contingencies. • Computational tractability is attained by a nested column-and-constraint generation algorithm. Dynamic line rating (DLR) and flexible ac transmission system (FACTS) are two technologies to enhance the utilization of existing transmission lines and exploit the inherent transmission-side flexibility. This paper coordinates DLR and FACTS in a two-stage security-constrained economic dispatch (SCED) model to enhance the power system flexibility in N-K contingency management and reduce operational cost. To utilize DLR while handling its uncertainty, spatial–temporal joint chance constraints (JCCs) are used. A scalable reformulation method for these JCCs is developed, which enables considering the spatial–temporal correlations between DLRs and co-optimizing the DLR utilization with system dispatch. To leverage the flexibility of FACTS, the adjustments of FACTS set points before and after the occurrence of any N-K line outage are modelled. The proposed SCED model is reformulated as a triple-level robust model, which avoids enumerating all possible N-K outages in the SCED model and obtains a more reasonable model size. To handle the presence of binary variables in the lowest level of the robust model, a nested column-and-constraint generation solution structure is designed. Case studies on IEEE 14 and 118-bus systems are conducted to verify the effectiveness of the proposed SCED model. [ABSTRACT FROM AUTHOR]

This paper proposes a novel data driven framework for detecting topology transitions in a distribution network. The framework analyzes data from phasor measurement units (PMUs) and relies on the fact that changes in network topology results in changes in the structure and admittance of the network. Using voltage and current phasors recorded by PMUs, the proposed method approximates network parameters using an ensemble-based deep learning model and thus, it does not require any knowledge of network parameters and load models. Using the prediction error of the proposed model, a connectivity matrix which shows the status of switches is constructed. In contrast to other methods, this proposed framework does not require a library of voltage and current transients associated with possible network transitions. It can also detect simultaneous switching actions and is robust to noise and load variations. The model yields a lower error detection rate, and its performance is validated using a modified version of the IEEE 33 bus network and a real feeder located in Queensland, Australia, under full and partial observability conditions. The proposed model has also been compared with another data driven method in terms of inference time and error detection rates. [ABSTRACT FROM AUTHOR]

Rheumatoid arthritis (RA), a chronic inflammatory disease, and its exact aetiology is not defined clearly. The free radicals produced in large amount in RA are associated with alteration in molecular structure resulting in glycation of proteins. As a result of glycation, advanced glycation end products (AGEs) produced. In this study, collagen type II suspension was injected into Wistar rats to make RA model of rats. Simultaneously, hesperidin 50 mg kg−1 body weight was orally administrated to the rats for 21 days. X‐rays of the rat hind paws were analyzed and found to be significantly effective against bone loss after treatment with hesperindin. Nε‐(carboxymethyl)lysine (CML) and pentosidine (PTD) concentrations in collagen‐induced RA plasma were determined as 565.29 ± 30.15 and 37.23 ± 1.02 ng ml−1, respectively, while CML and PTD in IgG were 6.63 ± 0.44 ng mg−1 IgG and 425.33 ± 37.26 ng g−1 IgG, respectively. After treatment with hesperidin, the elevated levels of CML in plasma and in IgG were significantly (p < 0.001) lowered to 450.95 ± 15.05 mg ml−1 and 5.23 ± 0.27 ng mg−1 IgG, respectively. Similarly, concentrations of PTD in plasma and IgG of rats treated with hesperidin were 28.46 ± 1.20 ng ml−1 and 359.35 ± 31.11 ng g−1 IgG, respectively. Thus, after treatment with drug, plasma CML and IgG PTD levels were restored as 93% and 16%, respectively, through free radical scavenging activity of hesperidin resulting in alleviation of RA disease by decreasing the AGEs concentrations. Therefore, use of hesperidin may be useful to alleviate severity of RA disease. Significance statement: Collagen type II suspension was used to make a rheumatoid arthritis model of rat.Hesperidin treatment was effective against bone loss.Hesperidin effectively reduced the concentrations of advanced glycation end products like Nε‐(carboxymethyl)lysine and pentosidine.Treatment with hesperidin resulted in the alleviation of rheumatoid arthritis disease through free radical scavenging and antiglycation activities.Hesperidin may be useful to alleviate the severity of rheumatoid arthritis disease. [ABSTRACT FROM AUTHOR]

Silver sulphide corrosion is a recently identified failure mechanism of transformer onload tap changers (OLTC). The corrosive sulphur in transformer oil reacts with the silver coated components of OLTC tap selector and forms silver sulphide films. During OLTC operation, the silver sulphide flakes can be detached from the tap selector and mix with the transformer oil. The silver sulphide is a semi conductive material. As a result, the dielectric strength in the transformer oil around the OLTC silver coated contacts or elsewhere in the transformer, wherever the semi conductive particles travel, will be reduced. Eventually, due to either high electric field stress or aged oil with a low dielectric strength, oil breakdown can occur between adjacent contacts. This can cause a catastrophic failure of the OLTC and quite often the tapping winding as well. Since such failures affect the transformer reliability, utilities are interested in methods of detecting and mitigating silver sulphide corrosion on OLTCs. This paper presents a risk assessment criterion to identify the degree of significance of silver sulphide corrosion in transformers using existing diagnostic techniques. [ABSTRACT FROM AUTHOR]

An environment-friendly efficient adsorbent, hexadecyltrimethylammonium bromide-modified rice husk (CTAB-RH), was chosen to eliminate anionic azo dye amaranth from aqueous solution. The newly synthesized adsorbent CTAB-RH was characterized by the Fourier transform infrared spectroscopy. The point of zero charge (pHpzc) value of CTAB-RH was estimated to be 5.85. Amaranth adsorption onto CTAB-RH was proven by the observations of field emission scanning electron microscopy (FE-SEM) coupling with energy dispersive X-ray spectroscopy (EDX). Adsorption kinetic experiments were conducted at the various contact time, solution pH, dye concentrations in solution, ionic strengths, and temperatures, respectively. The maximum dye adsorption was observed at pH 2. Amaranth adsorption kinetic data pursued a pseudo-second-order kinetic model. Equilibrium adsorption data followed the Langmuir isotherm model with a maximum 125 µmol/g dye adsorption capacity of CTAB-RH at 45°C. The activation energy of the present dye adsorption process was determined to be 18.71 kJ/mol. Thermodynamic study indicates that the amaranth dye adsorption onto CTAB-RH is a spontaneous endothermic process. Desorption of amaranth from dye-loaded CTAB-RH was performed in NaOH solution (pH 13) and finally, the recycled CTAB-RH was used without significant loss of its adsorption capacity. [ABSTRACT FROM AUTHOR]

Inverter transformers are one of the key components in a PV plant and their operating patterns are considerably different from that of transformers in a substation. Moreover, these transformers experience higher level of harmonics generated by the inverters. Therefore, investigating the ageing profile of the inverter transformer is a timely requirement. In this paper, the ageing of inverter transformers in a medium-scale solar PV plant is studied by utilizing various real-time measurements including load current, top-oil temperature (TOT), ambient temperature, moisture in top oil, solar irradiance and individual current harmonics. An updated moisture-dependent thermal model (MDTMH), with consideration of current harmonics is developed to estimate the hot-spot temperature (HST). The influence of weather conditions, which directly determine the load current of inverter transformers on the loss of life (LOL) of an inverter transformer is also investigated. Furthermore, the effect of current harmonics levels on the inverter transformer's HST and LOL is explored. Finally, comparisons of HST and LOL of inverter transformers connected to PV arrays with three different tracking technologies, i.e., fixed-tilt, single-axis and Dual-axis PV arrays are performed. [ABSTRACT FROM AUTHOR]

Conjugation of insulin-mimetic [meso-tetrakis(4-sulfonatophenyl)porphyrinato]Zn(II), Zn(tpps), with chitosan was examined in aqueous solution at various contact time, Zn(tpps) concentrations and solution temperatures, respectively. The chitosan–Zn(tpps) conjugate was characterized by UV–Vis and Fourier transform infrared (FTIR) spectroscopic techniques. The electrostatic interaction between negatively charged sulfonate (SO 3 -) groups of Zn(tpps) and positively charged amino ( NH 3 + ) groups of chitosan is responsible for the formation of chitosan–Zn(tpps) conjugate. Chitosan efficiently inhibits the demetallization and aggregation of Zn(tpps) in acidic aqueous solution. The conjugation kinetic data taken from various batch studies were examined by the pseudo-first-order, pseudo-second-order, Elovich kinetic, film diffusion and intra-particle diffusion models. The equilibrium conjugation isotherms were analyzed by Freundlich, Temkin and Langmuir isotherm models, respectively. The batch conjugation kinetic data were obeyed by the pseudo-second-order kinetic model rather than the pseudo-first-order and Elovich kinetic models. Equilibrium conjugation isotherms were explained well by the Langmuir isotherm model, and the highest extent of Zn(tpps) bound to chitosan was obtained to be 151.52 µmol/g at 45 °C. The activation energy (Ea: 10.21 kJ/mol), changes in Gibb's free energy (∆G: –26.38 to –28.12 kJ/mol), enthalpy (∆H: 8.74 kJ/mol) and entropy (∆S: 115.94 J/mol K) suggest that the chitosan–Zn(tpps) conjugation is an endothermic spontaneous process. The in vitro release of Zn(tpps) from chitosan–Zn(tpps) conjugate was investigated in phosphate buffer solution (pH 7.4) at 37 °C. The kinetics of Zn(tpps) release followed the first-order kinetics with a rate constant 0.0025 h‒1. The chitosan–Zn(tpps) conjugate may be used as an oral therapeutics for diabetes mellitus. [ABSTRACT FROM AUTHOR]

Grid-edge distributed energy resources (DERs) present both operational challenges and opportunities to distribution system operators (DSO). This paper presents a day-ahead scheduling strategy for DER-rich active distribution networks to leverage operational flexibilities of various DERs for effective network management. The scheduling strategy is realized based on a DSO-centric day-ahead market model that incorporates a multi-period and two-stage optimal power flow (OPF) model to determine scheduling and pricing for network and non-network DERs. The uncertainties in day-ahead operation stemming from local generation, load consumption, and market prices are robustly considered for hedging the intermittency and forecasting uncertainties. A novel bid price function is proposed for local distributed solar PV generation aiming at maximizing participation in network service. A new reactive power management and pricing scheme is also presented for optimal scheduling of voltage support devices within distribution network. The proposed framework is implemented on IEEE-33 bus balanced test system and operational planning strategy is analyzed for overall cost-benefits of the system at various uncertainty levels. A 7-10 percent saving in cost of procurement for DSO can be accrued at various uncertainty levels, and a 10 percent increase in revenue for the PV generation can be observed. • An optimal and sustainable operational planning for the DSO is proposed. • The proposed framework uses day-ahead model for operational planning of DERs. • The uncertainties in market prices, load, and PV generation are considered. • A new reactive power management strategy for fair pricing is proposed. • The proposed framework incentivizes older PV technologies with higher marginal prices. [ABSTRACT FROM AUTHOR]