Cyclopentane hydrate-based processes for treating heavy metal containing wastewater

The scarcity of water and increasing water pollution are the pressing challenge human being facing. Recovering water and valuable heavy metals is highly desired for treating heavy metal containing wastewater. We proposed a novel hydrate-based process to treat Ni2+ containing wastewater. The water recovery, Ni2+ enrichment factor, desalination efficiency were studied using this cyclopentane hydrate-based method. A water recovery of 43% can be obtained with a desalination efficiency of round 88% and an enrichment factor of 1.6. The desalination efficiency and the quality of the as-made water via the hydrate-based process can be further improved to above 99% via three-stage hydrate reaction. The proposed hydrate-based water treatment process may find wide applications in waste water treatment and heavy metal recycling

Recent progress in transition-metal-oxide-based electrocatalysts for the oxygen evolution reaction in natural seawater splitting: A critical review

Direct electrolytic splitting of seawater for the production of H2 using ocean energy is a promising technology that can help achieve carbon neutrality. However, owing to the high concentrations of chlorine ions in seawater, the chlorine evolution reaction always competes with the oxygen evolution reaction (OER) at the anode, and chloride corrosion occurs on both the anode and cathode. Thus, effective electrocatalysts with high selectivity toward the OER and excellent resistance to chloride corrosion should be developed. In this critical review, we focus on the prospects of state-of-the-art metal-oxide electrocatalysts, including noble metal oxides, non-noble metal oxides and their compounds, and spinel- and perovskite-type oxides, for seawater splitting. We elucidate their chemical properties, excellent OER selectivity, outstanding anti-chlorine-corrosion performance, and reaction mechanisms. In particular, we review metal oxides that operate at high current densities, near industrial application levels, based on special catalyst design strategies

Ultra-Precision Machining of a Compound Sinusoidal Grid Surface Based on Slow Tool Servo

Compound sinusoidal grid surface with nanometric finish plays a significant role in modern systems and precision calibrator, which can make the systems smaller, the system structure more simple, reduce the cost, and promote the performance of the systems, but it is difficult to design and fabricate by traditional methods. In this paper, a compound freeform surface constructed by a paraboloidal base surface and sinusoidal grid feature surface is designed and machined by slow tool servo (STS) assisted with single point diamond turning (SPDT). A novel combination of the constant angle and constant arc-length method is presented to optimize the cutting tool path. The machining error prediction model is analyzed for fabricating the compound sinusoidal grid surface. A compound sinusoidal grid surface with 0.03 mm amplitude and period of 4 is designed and cutting process is simulated by use of MATLAB software, machining experiment is done on ultra-precision machine tool, the surface profile and topography are measured by Taylor Hobson and Keyence VR-3200, respectively. After dealing with the measurement data of compound freeform surface, form accuracy 4.25 μm in Peak Village value (PV), and surface roughness 89 nm in Ra are obtained for the machined surface. From the theoretical analysis and experimental results, it can be seen that the proposed method is a reasonable choice for fabricating the compound sinusoidal grid surface

The Second Class of Tetrahydrofolate (THF-II) Riboswitches Recognizes the Tetrahydrofolic Acid Ligand via Local Conformation Changes

Riboswitches are regulatory noncoding RNAs found in bacteria, fungi and plants, that modulate gene expressions through structural changes in response to ligand binding. Understanding how ligands interact with riboswitches in solution can shed light on the molecular mechanisms of this ancient regulators. Previous studies showed that riboswitches undergo global conformation changes in response to ligand binding to relay information. Here, we report conformation switching models of the recently discovered tetrahydrofolic acid-responsive second class of tetrahydrofolate (THF-II) riboswitches in response to ligand binding. Using a combination of selective 2′-hydroxyl acylation, analyzed by primer extension (SHAPE) assay, 3D modeling and small-angle X-ray scattering (SAXS), we found that the ligand specifically recognizes and reshapes the THF-II riboswitch loop regions, but does not affect the stability of the P3 helix. Our results show that the THF-II riboswitch undergoes only local conformation changes in response to ligand binding, rearranging the Loop1-P3-Loop2 region and rotating Loop1 from a ~120° angle to a ~75° angle. This distinct conformation changes suggest a unique regulatory mechanism of the THF-II riboswitch, previously unseen in other riboswitches. Our findings may contribute to the fields of RNA sensors and drug design

A solution for reallocating public bike among bike stations

International audiencePublic bike system for proximity travel is widely used in urban cities all over the world. Main reasons for launching public bike program is to reduce carbon footprint so as to prevent greenhouse effect and to solve Last-Mile problem in order to make convenient for citizens. However, we may encounter awkward cases in peak hours (from 7:00 to 9:00 and 17:00 to 19:00) that no bike is available at some stations or no vacant place is left to put bikes. The actual solution in most cities is in a traditional way based on call centers. A personnel taking charge of bikes in a certain zone reallocates bikes among bike stations based on notification of bike users by telephone call when bike stations are full or empty. This inefficient solution will reduce bike utilization and even annoy bike users. In this paper, we propose a system & methodology to intelligently guide personnel to reallocate bikes among stations, aiming at overcoming the above awkward cases and maximizing bike utilization

Mechanism and Characteristics of Humidity Sensing with Polyvinyl Alcohol-Coated Fiber Surface Plasmon Resonance Sensor

A surface plasmon resonance (SPR) sensor based on a side-polished single mode fiber coated with polyvinyl alcohol (PVA) is demonstrated for relative humidity (RH) sensing. The SPR sensor exhibits a resonant dip in the transmission spectrum in ambient air after PVA film coating, and the resonant wavelength shifts to longer wavelengths as the thickness of the PVA film increases. When RH changes, the resonant dip of the sensor with different film-thicknesses exhibits interesting characteristics for optical spectrum evolution. For sensors with initial wavelengths between 550 nm and 750 nm, the resonant dip shifts to longer wavelengths with increasing RH. The averaged sensitivity increases firstly and then drops, and shows a maximal sensitivity of 1.01 nm/RH%. Once the initial wavelength of the SPR sensor exceeds 850 nm, an inflection point of the resonant wavelength shift can be observed with RH increasing, and the resonant dip shifts to shorter wavelengths for RH values exceeding this point, and sensitivity as high as −4.97 nm/RH% can be obtained in the experiment. The sensor is expected to have potential applications in highly sensitive and cost effective humidity sensing

Helicity Enhanced Torsion Sensor Based on Liquid Filled Twisted Photonic Crystal Fibers

A highly sensitive torsion sensor can be constructed by combining a twisted photonic crystal fiber with a liquid-filled waveguide in its air-hole cladding. The torsion sensitivity of this type of sensor is determined directly by the phase-matching conditions between the fiber core mode and the liquid waveguide mode, which can be improved by tuning the helicity (denoted by the initial twist rate, α0) of the twisted photonic crystal fiber. The enhancement mechanism of α0 on the sensitivity of the proposed torsion sensor is investigated theoretically, followed by experimental verifications, and a torsion sensitivity as high as 446 nm∙mm∙rad−1 can be obtained by tailoring these parameters. Experimental results show that the torsion sensitivity increases with α0 decreasing from 3.142 to 3.925 rad/mm, which are in consistence with that of the numerical predictions. The demonstrated torsion sensor is expected to contribute to the development of highly sensitive torsion-related photonic crystal fiber devices