Enhanced natural degradation of cyanide tailings: Integrated application of solar drying system and UV irradiation

Cyanide tailings are the bulk solid waste generated by the production processes of gold mines. Since the highly toxicity of cyanide affects its disposal and comprehensive utilization, a decyanation treatment is needed. However, wide-ranging industrial uses of the current decyanation methods are restricted due to the treatment effects and costs. Based on the natural degradation method, the cyanide treatment effect was enhanced by raising the treatment temperature, increasing the ultraviolet (UV) irradiation and turning the pile periodically. Using the Arrhenius equation, the activation energies of the cyanide hydrolysis reactions were calculated as 52.22 kJ/mol and 34.59 kJ/mol for heating alone and for heating combined with UV irradiation, respectively. At 60 ℃, the cyanide tailings reached the discharge standard (leachate, total cyanide (CNt)< 5 mg/L) after 8 h of treatment. Moreover, after adding UV irradiation (with an intensity of 120 μW/cm²) and a hydrogen peroxide spray (spraying intensity, 2 mL/kg) to the above conditions and shortening the treatment time to 7 h, the cyanide tailings reached the standard for use in building materials (leachate, CN_t <0.5 mg/L). Based on these results, UV irradiation, ventilation, spraying and pile-turning were integrated into the solar drying room to form an enhanced natural degradation system, which was applied in the semi-industrial scale treatment of the cyanide tailings. The results showed that the cyanide tailings consistently met the standards for discharge and use in building materials, successfully verified the conditions and effects of the laboratory treatment, and reduced the treatment cost by more than 50 %.

Electrochemical study of the effect of radiofrequency on glutamate oxidase activity using a glutamate oxidase-based biosensor

A biosensor based on glutamate oxidase (GluOx) was developed to measure glutamate concentration. The main function of this type of biosensor is related to the structure and catalytic activity of GluOx. Since radiofrequency, as the widest spectrum of electromagnetic fields, can affect the catalytic activity and structure of GluOx, in this study, the effect of these fields on the analytical parameters of the fabricated biosensor was investigated. To build the biosensor a sol-gel solution of chitosan and native GluOx were prepared and then immobilized on the surface of the platinum electrode. Similarly, to investigate the effect of radiofrequency fields on the analytical parameters of the biosensor, instead of the native GluOx, irradiated GluOx was used to build the biosensor. To evaluate the biosensor responses, cyclic voltammetry experiments were performed and voltammograms were considered as biosensor responses. To determine the analytical parameters including detection limit, linear range, and saturation region of the responses, calibration curves were drawn for each of the biosensors. Also the long-term stability and selectivity of the fabricated biosensor were evaluated. Thereafter, the optimum pH and temperature for each of these two biosensors were examined. The results showed that radiofrequency waves harmed the detection and response of biosensors in the saturation region, while they had little effect on the linear region. Such results could be due to the effect of radiofrequency waves on the structure and function of glutamate oxidase. In general, the results indicate that when a glutamate oxidase-based biosensor is used to measure glutamate in radiofrequency fields, corrective coefficients for this type of biosensor should be considered to accurately measure glutamate concentration.

Anti-apoptotic effect of silymarin-loaded chitosan nanoparticles on hippocampal caspase-3 and Bcl-2 expression following cerebral ischemia/reperfusion injury

BACKGROUND

Cerebral ischemia/reperfusion (I/R) causes memory and learning impairments and apoptosis in the hippocampus. The aim of present study aimed to investigate the anti-apoptotic effects of silymarin-loaded chitosan nanoparticles (SM-CS-NPs) on the expression of Bcl-2 and Caspase-3 genes in hippocampal neurons after I/R injury.

MATERIAL AND METHODS

SM and SM-CS-NPs were orally administered (15 mg/kg) for 14 days, and then cerebral I/R injury was induced by the bilateral common carotid artery occlusion (BCCAO). One day after I/R induction, memory and learning impairments and various biochemical estimations were assessed.

RESULTS

Our results indicated that SM-CS-NPs improved I/R-induced memory and learning impairments and oxidative damage in the hippocampal region. The qRT-PCR analysis indicated that SM-CS-NPs pretreatment inhibited I/R-induced neuronal apoptosis by increasing the expression of Bcl-2 and decreasing the expression of Caspase-3 in the hippocampus.

CONCLUSION

These findings suggest that SM-CS-NPs exert neuroprotective effects, and the neuroprotection is likely to be associated with the regulation of Bcl-2 and Caspase-3, leading to inhibition of apoptotic cell death in hippocampal neurons.

Oscillatory dynamics mechanism induced by protein synthesis time delay in quorum-sensing system

Recent experimental evidence reports that the oscillatory behavior of quorum sensing plays an extremely important role in the process of bacterial synthesis and release drug to fight cancer. As we know, the six substances AiiA, LuxI, internal AHL, external AHL, AHL substrate, and H_{2}O_{2} are the core parts of the quorum-sensing system. Here, the effects of several important factors, including time delay, variable H_{2}O_{2}, AHL synthesis rate induced by LuxI, and AHL degradation rate induced by AiiA on the oscillatory behavior of the quorum-sensing system are studied theoretically based on a part of mathematical model describing the interaction of the above six substances proposed by Prindle et al. [Nature 508, 387 (2014)10.1038/nature13238]. The results show that the time delay is a prerequisite for inducing oscillation of the quorum-sensing system. Furthermore, the length of time delay can determine the amplitude and period of oscillation. As a further matter, the change of H_{2}O_{2} concentration can induce the oscillatory behavior of the quorum-sensing system. In addition, under the regulation of H_{2}O_{2}, the period robustness of the quorum-sensing system is increased. Similarly, the quorum-sensing system exhibits periodic oscillation when AHL synthesis rate induced by LuxI less than a certain critical value, unless it displays a steady state. Additionally, a too-high or too-low level of AHL degradation rate induced by AiiA will fail to generate oscillation of the quorum-sensing system, only the intermediate level will cause oscillation. Finally, the two and three parameter regions in which the quorum-sensing system exhibits oscillation behavior are generated.

Probing the effect(s) of the microwaves' electromagnetic fields in enzymatic reactions

This paper examines the effects that electromagnetic fields from microwave radiation have in enzymatic reactions. Hydrolysis of proteins in beef (in vivo case) and casein (in vitro case) by the papain enzyme, a major industrial enzyme, is used herein as a model reaction to assess, under highly controlled conditions, the various parameters of microwave radiation (electric field, magnetic field, pulsed microwave irradiation, continuous microwave irradiation) as they might influence these in vivo and in vitro enzymatic reactions. The effect(s) of the microwaves’ electromagnetic fields was clearly evidenced in the in vivo case, contrary to the in vitro case where no such effect was observed, likely due to the nature of the hydrolysis reaction and to the autolysis (self-digestion) of the papain enzyme. Additionally, the effect of pulsed versus continuous microwave irradiation was further assessed by examining the catalase-assisted decomposition of hydrogen peroxide.

Intravenous laser wavelength radiation effect on LCAT, PON1, catalase, and FRAP in diabetic rats

The main purpose of this study is to evaluate the effect of intravenous irradiation of different low-level laser wavelengths on the activity of lecithin-cholesterol acyltransferase (LCAT), paraoxonase (PON1), catalase, and ferric reducing ability of plasma (FRAP) in diabetic rats. First, diabetes was induced in rats using streptozotocin (STZ). Enzymes' activity was measured in the blood samples and compared before and after intravenous laser blood irradiation. We used four continuous-wave lasers-IR (λ = 808 nm), Red (λ = 638 nm), Green (λ = 532 nm), and Blue (λ = 450 nm)-to compare the wavelength's effect on different enzymes' activity. Laser power was fixed at 0.01 mW and laser energy was changed by 2-, 4-, 6-, and 8-min time of radiations.The enzymes' activity of blood samples was measured 2, 6, and 24 h after radiation. The results show an increase in the activity of different enzymes when compare with diabetic non-radiated samples. More importantly, with a constant laser energy, the enzymes' activity increased with decreasing laser wavelength. It is important to note that with a constant laser energy, as the wavelength decreases, the photon energy increases and the number of photons decrease, while the enzyme's activity elevation increases. As a result, we can conclude that in intravenous low-level laser therapy, photon energy is more important than the number of photons even if their product, energy, is kept constant.

Effect of Low-Level Laser Irradiation on the Function of Glycated Catalase

Introduction: The aim of this work is to evaluate the effect of low-level laser irradiation (LLLI), by lasers with different wavelengths, on glycated catalase enzyme in vitro experimentally. Methods: This is done by measuring the activity and structure properties of glycated catalase enzyme. The structure properties were evaluated with circular dichroism (CD) and fluoroscopy methods. Three continuous wave (CW) lasers in the visible spectrum (λ =450, 530, 638 nm) and a 100-ns pulsed laser in the infrared spectrum (λ =905 nm) were chosen for comparison. For the infrared laser, same effects have been investigated for different energy doses. The effect of photon energy (hυ) at different wavelengths was measured on activity, CD, and fluoroscopy properties of catalase, and compared with the control group (samples without irradiation). The energy intensity of laser should not exceed 0.1 J/cm² . Experiments were performed on glycated catalase between 2 to 16 weeks after glycation of catalase. The LLLI effect was also investigated on the samples, by comparing the catalase activity, CD and fluoroscopy for different wavelengths. Results: Our results indicated, the decrease in catalase activity as a function of glycation time (weeks) for all samples, and a slight increase on its activity by different laser wavelengths irradiation for any fixed period of glycation time. Finally, the catalase activity has been increased as the laser's photon energy (hυ) intensified. More specifically, the blue laser (λ =450 nm) had the most and the red laser (λ =638 nm) had the least effect, and the green laser (λ =530 nm) had the medium effect on catalase activity as well. Furthermore, pulsed laser had an additional effect by increasing energy dosage. Conclusion: As we expected in all experiments, an increase in the catalase activity was coincident with a decrease in the catalase fluoroscopy and CD parameters.

Investigation of Nonlinear Output-Input Microwave Power of DMSO-Ethanol Mixture by Molecular Dynamics Simulation

The nonlinear response of output-input microwave power for DMSO-ethanol mixture, which was exhibited as the direct evidence of non-thermal effect in experiment, was investigated by molecular dynamics simulation. Effects of microwave field on the mixture were evaluated from the alteration in structure, transport, hydrogen bonding dynamics and intermolecular interaction energy. Increasing the strength of the microwave field did not lead to any markedly conformational change, but decrease the diffusion coefficient. Prolonged hydrogen bonding lifetimes, which caused by the redistribution of microwave energy, was also detected. Distinct threshold effect was observed, which was consistent with the behavior in the experiment.