G-quadruplex–hemin DNAzyme molecular beacon probe for the detection of methamphetamine

In this work, a simple, cost-effective, and label-free biosensor was constructed for methamphetamine (METH) detection. The biosensor consists of a G-quadruplex–hemin DNAzyme molecular beacon (DNAzyme MB), a METH aptamer, and a colorimetric substrate. The DNAzyme MB loses peroxidase activity when it hybridizes with the METH aptamer. In the presence of METH, DNAzyme MB dissociates from the inactive hybrid due to preferable hybridization of METH with the aptamer. This process recovers the activity of DNAzyme MB, which catalyzes a reaction with the colorimetric substrate to yield measurable signals. Under optimized conditions, a detection limit as low as 0.5 nM (74.6 ng L−1) was achieved. Common illicit drugs were found to have little interference on detection of METH. Recoveries of METH spiked in urines of addicts were greater than 85%. Good agreement was observed between METH concentrations in urines determined by the sensor and by liquid chromatography-tandem mass spectrometer. These results indicate that the G-quadruplex–hemin DNAzyme MB probe holds promise to detect METH not only in biological samples, but also in environmental matrices

Revealing the link between evolution of electron transfer capacity of humic acid and key enzyme activities during anaerobic digestion

Humic acid (HA) is an important active compound formed during anaerobic digestion process, with a complex structure and dynamic electron transfer capacity (ETC). However, the mechanisms by which these macromolecular organic compounds dynamically interact with the microbial anaerobic digestion process at different operating temperatures are still unclear. In this study, the link between the evolution of the ETC of HAs and the microbial community under mesophilic and thermophilic conditions was investigated. The results showed an increasing trend in the ETC of HAs in both mesophilic (671–1479 μmol gHA−1) and thermophilic (774–1506 μmol gHA−1) anaerobic digestion (AD) until day 25. The ETC was positively correlated with the bacterial community of hydrolytic and acidogenic phases, but negatively correlated with the archaeal community of the methanogenic phase. Furthermore, the relationship between ETC and key enzyme activity was explored using a co-occurrence network analysis. HAs revealed a high potential to promote key enzyme activities during hydrolysis (amylase and protease) and acidification (acetate kinase, butyrate kinase, and phosphotransacetylase) while inhibiting the key enzyme activity in the methanogenic phase during the anaerobic digestion process. Moreover, HAs formed under thermophilic conditions had a greater influence on key enzyme activities than those formed under mesophilic conditions. This study advances our understanding of the mechanisms underlying the influence of HAs on anaerobic digestion performance

Dynamic evolution of humic acids during anaerobic digestion: exploring an effective auxiliary agent for heavy metal remediation

Information on the dynamic evolution of humic acid (HA) from anaerobic digestate and the potential of HA serving as an effective agent for remedying heavy metals is rather scarce. This study monitored the evolution of the structure and functional groups and metal-binding abilities of HA during chicken manure and corn stover anaerobic digestion (AD) processes. Higher increases in aromatic (41-66%) and oxygen-containing functional groups (37-45%) were observed in HA from the AD of corn stover, resulting in higher metal-binding abilities for Cu(II), Co(II), and Ni(II) than those of chicken manure AD. Moreover, HA extracted from fast (before day 12 for chicken manure and day 16 for corn stover), and slow (day 40) methane production stages performed different complexation capacities for the heavy metals. These results reveal the mechanisms of HA and heavy metal interactions, and confirm the potential of HA extracted from AD process for the remediation of heavy metals

Microbial behavior and influencing factors in the anaerobic digestion of distiller: a comprehensive review

Anaerobic digestion technology is regarded as the most ideal technology for the treatment of a distiller in terms of environmental protection, resource utilization, and cost. However, there are some limitations to this process, the most prominent of which is microbial activity. The purpose of this paper is to provide a critical review of the microorganisms involved in the anaerobic digestion process of a distiller, with emphasis on the archaea community. The effects of operating parameters on microbial activity and process, such as pH, temperature, TAN, etc., are discussed. By understanding the activity of microorganisms, the anaerobic treatment technology of a distiller can be more mature. Aiming at the problem that anaerobic treatment of a distiller alone is not effective, the synergistic effect of different substrates is briefly discussed. In addition, the recent literature on the use of microorganisms to purify a distiller was collected in order to better purify the distiller and reduce harm. In the future, more studies are needed to elucidate the interactions between microorganisms and establish the mechanisms of microbial interactions in different environments

Mechanisms of genuine humic acid evolution and its dynamic interaction with methane production in anaerobic digestion processes

Humic acid (HA), a byproduct formed during the biological conversion of organic matter into biogas in the anaerobic digestion (AD) process, contains complex structures and redox functions. However, the evolution mechanism of HA and its interaction with CH4 production during the AD process have not been fully explored, particularly with respect to various substrates and temperature conditions. In this study, we investigated the evolutionary dynamics of the structure and function of genuine HA that naturally formed in the AD processes of chicken manure and corn stover under mesophilic (37 °C) and thermophilic (55 °C) conditions. The results demonstrated that the HA evolution mechanisms in AD of chicken manure and corn stover have different pathways. The AD of core stover showed higher degree of aromaticity (41.2–66.7% and 45.3–68.4% for mesophilic and thermophilic respectively) and humification index (1.5–4.2 and 2.8–4.5 for mesophilic and thermophilic respectively) than those (28.3–45.3% and 30.2–54.5% of aromaticity and 0.6–1.2 and 1.3–3.7 of humification index) in AD of chicken manure. The results from HSQC NMR spectroscopy and 2D-COS-FTIR spectroscopy demonstrated an accelerating effect of the higher temperature on the evolution of HA through humification. Moreover, the concurrent decomposition and re-polymerization of HA during both AD processes, resulting in positive and negative effects on CH4 production in the fast and slow CH4 production stages, respectively. The dynamic interaction was due to variations in the electron transferring ability and structure of the formed HA. The results could not only advance our understanding of the mechanisms of HA evolution and its interaction with the performance of AD process, but also support further research toward improving AD performance by regulating HA formation and transformation

Nanomaterial-based aptamer sensors for arsenic detection

Arsenic (As) is a highly toxic contaminant in the environment and a serious carcinogen for the human being. The toxicity of arsenic significantly threatens environmental and human health. The effective removing technology for arsenic remains challenging, and one of the reasons is due to the lack of powerful detection method in the complex environmental matrix. There is thus an urgent need to develop novel analytical methods for arsenic, preferably with the potential for the field-testing. To combat arsenic pollution and maintain a healthy environment and eco-system, many advanced analytical methods have been developed for arsenic detection in various samples. Among these strategies, biosensors hold great promise for rapid detection of arsenic, in particular, nanomaterials-based aptamer sensors have attracted significant attention due to their simplicity, high sensitivity and rapidness. In this paper, we reviewed the recent development and promising applications of aptamer sensors (aptasensors) based-on nanomaterial for arsenic detection, in particular with emphasis on the works using optical and electrochemical technologies. We also discussed the recent novel technology in aptasensors development for arsenic detection, including nucleic acid amplification for signal enhancement and device integration for the portability of arsenic sensors. We are hoping this review could inspire further researches in developing novel nanotechnologies based aptasensors for possible on-site detection of arsenic

Breaking K+ Concentration Limit on Cu Nanoneedles for Acidic Electrocatalytic CO2 Reduction to Multi‐Carbon Products

Electrocatalytic CO2 reduction reaction (CO2RR) to multi-carbon products (C2+) in acidic electrolyte is one of the most advanced routes for tackling our current climate and energy crisis. However, the competing hydrogen evolution reaction (HER) and the poor selectivity towards the valuable C2+ products are the major obstacles for the upscaling of these technologies. High local potassium ions (K+) concentration at the cathode's surface can inhibit proton-diffusion and accelerate the desirable carbon-carbon (C−C) coupling process. However, the solubility limit of potassium salts in bulk solution constrains the maximum achievable K+ concentration at the reaction sites and thus the overall acidic CO2RR performance of most electrocatalysts. In this work, we demonstrate that Cu nanoneedles induce ultrahigh local K+ concentrations (4.22 M) – thus breaking the K+ solubility limit (3.5 M) – which enables a highly efficient CO2RR in 3 M KCl at pH=1. As a result, a Faradaic efficiency of 90.69±2.15 % for C2+ (FEC2+) can be achieved at 1400 mA.cm−2, simultaneous with a single pass carbon efficiency (SPCE) of 25.49±0.82 % at a CO2 flow rate of 7 sccm

Enhanced biofuel production by co-pyrolysis of distiller's grains and waste plastics: a quantitative appraisal of kinetic behaviors and product characteristics

Pyrolysis of biomass feedstocks can produce valuable biofuel, however, the final products may present excessive corrosion and poor stability due to the lack of hydrogen content. Co-pyrolysis with hydrogen-rich substances such as waste plastics may compensate for these shortcomings. In this study, the co-pyrolysis of a common biomass, i.e. distiller's grains (DG), and waste polypropylene plastic (PP) were investigated towards increasing the quantity and quality of the production of biofuel. Results from the thermogravimetric analyses showed that the reaction interval of individual pyrolysis of DG and PP was 124–471 °C and 260–461 °C, respectively. Conversely, an interaction effect between DG and PP was observed during co-pyrolysis, resulting in a slower rate of weight loss, a longer temperature range for the pyrolysis reaction, and an increase in the temperature difference between the evolution of products. Likewise, the Coats-Redfern model showed that the activation energies of DG, PP and an equal mixture of both were 42.90, 130.27 and 47.74 kJ mol−1, respectively. It thus follows that co-pyrolysis of DG and PP can effectively reduce the activation energy of the reaction system and promote the degree of pyrolysis. Synergistic effects essentially promoted the free radical reaction of the PP during co-pyrolysis, thereby reducing the activation energy of the process. Moreover, due to this synergistic effect in the co-pyrolysis of DG and PP, the ratio of elements was effectively optimized, especially the content of oxygen-containing species was reduced, and the hydrocarbon content of products was increased. These results will not only advance our understanding of the characteristics of co-pyrolysis of DG and PP, but will also support further research toward improving an efficient co-pyrolysis reactor system and the pyrolysis process itself

Hypoxic acclimatization training improves the resistance to motion sickness

ObjectiveVestibular provocation is one of the main causes of flight illusions, and its occurrence is closely related to the susceptibility of motion sickness (MS). However, existing training programs have limited effect in improving the resistance to motion sickness. In this study, we investigated the effects of hypoxia acclimatization training (HAT) on the resistance to motion sickness.MethodsHealthy military college students were identified as subjects according to the criteria. MS model was induced by a rotary chair. Experimental groups included control, HAT, 3D roller training (3DRT), and combined training.ResultsThe Graybiel scores were decreased in the HAT group and the 3DRT group and further decreased in the combined training group in MS induced by the rotary chair. Participants had a significant increase in blood pressure after the rotary chair test and a significant increase in the heart rate during the rotary chair test, but these changes disappeared in all three training groups. Additionally, LFn was increased, HFn was decreased, and LF/HF was increased accordingly during the rotary chair test in the control group, but the changes of these three parameters were completely opposite in the three training groups during the rotary chair test. Compared with the control group, the decreasing changes in pupillary contraction velocity (PCV) and pupillary minimum diameter (PMD) of the three training groups were smaller. In particular, the binocular PCV changes were further attenuated in the combined training group.ConclusionOur research provides a possible candidate solution for training military pilots in the resistance to motion sickness

Three-dimensional frameworks of gallium selenide supertetrahedral clusters

通讯作者地址: Feng, PY (通讯作者), Univ Calif Riverside, Dept Chem, Riverside, CA 92521 USA 地址: 1. Univ Calif Riverside, Dept Chem, Riverside, CA 92521 USA 2. Calif State Univ Long Beach, Dept Chem & Biochem, Long Beach, CA 90840 USA 电子邮件地址: [email protected]