Restricted ambient temperature and slow heat replenishment in the phase transition of water molecules severely limit the performance of the evaporation-induced hydrovoltaic generators. Here we ...demonstrate a heat conduction effect enhanced hydrovoltaic power generator by integrating a flexible ionic thermoelectric gelatin material with a porous dual-size Al
O
hydrovoltaic generator. In the hybrid heat conduction effect enhanced hydrovoltaic power generator, the ionic thermoelectric gelatin material can effectively improve the heat conduction between hydrovoltaic generator and near environment, thus increasing the water evaporation rate to improve the output voltage. Synergistically, hydrovoltaic generator part with continuous water evaporation can induce a constant temperature difference for the thermoelectric generator. Moreover, the system can efficiently achieve solar-to-thermal conversion to raise the temperature difference, accompanied by a stable open circuit voltage of 6.4 V for the hydrovoltaic generator module, the highest value yet.
The utilization of green and sustainable solar energy
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photocatalysis is regarded as a promising strategy to tackle the ever-increasing energy shortage and environmental deterioration. In addition ...to traditional semiconductor-based photocatalysts, metal-organic frameworks (MOFs), a class of crystalline micro-mesoporous hybrid materials constructed from metal or metal nodes interconnected with multi-dentate organic linkers, are emerging as a new type of photocatalytic material. Post-synthetic modifications (PSM) on MOFs, in which chemical transformations or exchanges are made on pre-synthesized MOF materials, are found to be a powerful strategy for fabricating photoactive MOFs based on already existing MOFs. In this frontier article, different PSM strategies for the development of photoactive MOFs, including coordination on unsaturated metal sites, metalation on open coordinated sites, covalent modifications on ligands, ligand exchange, metal exchange and cavity encapsulation, have been summarized. Our views on the challenges and the direction in developing photocatalytic MOFs by PSM are also addressed. We hope that this frontier article can provide some guidance for rational designing of highly efficient MOF-based photocatalysts
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PSM strategies and to stimulate more research interest to be devoted to this promising yet largely unexplored field.
In this frontier article, we have summarized different PSM strategies for the development of photoactive MOFs for a variety of photocatalytic applications.
Al, CaO and salt powder mixtures are used as the starting materials to prepare the Al-based materials by the mechanical ball-milling method for hydrogen generation. The effects of preparation and ...reaction parameters on the hydrogen generation are investigated in this paper. With increasing ball milling time, the Al crystallite size is reduced and the reaction activity of Al is improved. But the overlong ball milling time easily causes the oxidation of Al and decreases its hydrogen yield. CaO can provide OH− for the hydrogen generation reaction by hydrolysis. Increasing the NaCl addition can accelerate the activation of Al and promote its hydrogen generation. In the water containing chloride ions and sulfate ions, the hydrogen generation rate is obviously improved. But Mg2+ ions will reduce the hydrogen yield due to its strong affinity to OH−. The maximum hydrogen yield is gained in the water at 30 °C There are some CaO on the surface of Al particle in the Al-based materials, which can improve the air oxidation resistance in air. Storing the Al-based materials in air with relative humidity of 50% at 30 °C for 40 h, the hydrogen yield is still kept at 89%.
► The inert alumina film is prevented from forming on the Al surface by adding CaO. ► The Al-based materials can rapidly react with water to produce hydrogen. ► The Al-based materials are very cheap and are easily prepared by ball milling.
A new hydrogen generation material, Al–Ca alloy, is prepared by ball milling method. Results show the prepared Al–Ca alloy can react with to produce hydrogen, but its hydrogen yield is lower. NaCl ...addition can further greatly improve hydrogen generation of Al–Ca alloys. The amount of NaCl addition and ball milling time depends on the Ca contents of alloys. As the Ca contents of alloy increase, the amount of NaCl addition or ball milling time may be reduced accordingly. Increasing Ca contents, NaCl addition or ball milling time is beneficial to improve the hydrogen generation rate. Al–Ca alloys can react with water to produce hydrogen at the temperature ranging from 10
°C to 80
°C, and simultaneously a great amount of heat is released. With the increase of air exposure time, the dense Al
2O
3 and CaO layer formed on the surface of alloy particles will reduce the oxidation reaction rate. Chloride ions and sulfate ions can greatly decrease the induction period of hydrogen generation reaction and obviously improve hydrogen generation rate. Ca
2+ ions and Mg
2+ ions can affect the production of hydrogen due to their strong affinity to OH
−, especially Mg
2+ ions which greatly decrease the hydrogen yield to 20%.
► The inert oxide film of Al surface is disrupted by adding Ca into Al to form Al–Ca alloy. ► The prepared Al–Ca alloy can rapidly react with water to produce hydrogen. ► NaCl is added as the activator by ball milling to further improve the hydrogen yield of Al–Ca alloy. ► The prepared Al–Ca alloy can react with water at different temperature.
Type 2 diabetes is often accompanied by abnormal blood lipid and lipoprotein levels, but most studies on the link between hyperlipidemia and diabetes have focused on free fatty acids (FFAs). In this ...study, we examined the relationship between cholesterol and insulin secretion from pancreatic beta-cells that is independent of the effects of FFAs.
Several methods were used to modulate cholesterol levels in intact islets and cultured beta-cells, including a recently developed mouse model that exhibits elevated cholesterol but normal FFA levels. Acute and metabolic alteration of cholesterol was done using pharmacological reagents.
We found a direct link between elevated serum cholesterol and reduced insulin secretion, with normal secretion restored by cholesterol depletion. We further demonstrate that excess cholesterol inhibits secretion by downregulation of metabolism through increased neuronal nitric oxide synthase dimerization.
This direct effect of cholesterol on beta-cell metabolism opens a novel set of mechanisms that may contribute to beta-cell dysfunction and the onset of diabetes in obese patients.
The addition of Li can prevent an inert alumina film from forming on the surface of Al alloy particles, allowing the rapid hydrogen generation of Al alloys to be achieved. However, because the Li ...content is less than 10%, the hydrogen generation rate and hydrogen yield of Al–Li alloys are significantly decreased. In this work, NaCl is introduced to prepare Al–Li alloys with low Li contents by ball milling. The research results show that by increasing the amount of NaCl added, the ball milling time and Li content can effectively improve the hydrogen generation of the alloys. Under optimal preparation conditions, the ultimate hydrogen yield of Al–Li alloys can reach 100%. The initial water temperature has almost no effect on the generation of hydrogen, even at 0 °C. Ca2+ and Mg2+ can combine with OH− to form the insoluble compounds Ca(OH)2 and Mg(OH)2, which can prevent hydrogen generation. NO3− reacts with Al to form ammonia and reduce the hydrogen yield of the alloys. Therefore, Al–Li alloys should be prevented from reacting with water containing Ca2+, Mg2+ and NO3−. Al–Li alloys must be stored in isolation from air to maintain good hydrogen-generation performances.
•The hydrogen generation rate of Al–Li alloys (Li < 10%) is enhanced significantly.•The hydrogen yields of Al–Li alloys (Li < 10%) can reach 100%.•Al–Li alloys (Li < 10%) can react with water at different temperature to produce H2.•The cost of hydrogen generation for Al–Li alloys is reduced.
The formation of mature secretory granules is essential for proper storage and regulated release of hormones and neuropeptides. In pancreatic β cells, cholesterol accumulation causes defects in ...insulin secretion and may participate in the pathogenesis of type 2 diabetes. Using a novel cholesterol analog, we show for the first time that insulin granules are the major sites of intracellular cholesterol accumulation in live β cells. This is distinct from other, non‐secretory cell types, in which cholesterol is concentrated in the recycling endosomes and the trans‐Golgi network. Excess cholesterol was delivered specifically to insulin granules, which caused granule enlargement and retention of syntaxin 6 and VAMP4 in granule membranes, with concurrent depletion of these proteins from the trans‐Golgi network. Clathrin also accumulated in the granules of cholesterol‐overloaded cells, consistent with a possible defect in the last stage of granule maturation, during which clathrin‐coated vesicles bud from the immature granules. Excess cholesterol also reduced the docking and fusion of insulin granules at the plasma membrane. Together, the data support a model in which cholesterol accumulation in insulin secretory granules impairs the ability of these vesicles to respond to stimuli, and thus reduces insulin secretion.
Imitation of the perception system of living creatures is of great importance for the construction of artificial nerves and intelligent human-machine interfaces. However, a prominent challenge is to ...emulate the functions of the biological synapse, which is the basic building block of the neural system. Here, inspired by the pain perception mechanism of the living creatures, a flexible double-layer memristor was constructed, with 90% semiconducting single-wall carbon nanotubes (s-SWCNTs) covered by LiClO4 doped polyoxyethylene oxide (PEO: LiClO4) as the channel materials. The carriers (protons and Li+) from PEO: LiClO4 imitated the functions of Na+ and K+ in biological systems. A potentiation of the post-synaptic signal was observed with mild stimuli, while the post-synaptic signal was inhibited with severe stimuli with a pulse voltage larger than 1.4 V in this research. These behaviors resemble the sensation of pain, neuroprotection, and possible injuries to the neural system. To explore the underlying mechanism of the phenomenon, the fourier-transform infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS), Raman spectrum, and current (IV) sweep were carried out. It was inferred that the observed results are attributable to the interaction between carriers in PEO: LiClO4 and functional groups and defects in the s-SWCNTs. The enhanced channel current results from the fulfillment of the traps by the carriers, and the suppression of the current is due to the intercalation of Li+ in the s-SWCNTs. This flexible artificial synapse opens a new avenue for the construction of biocompatible electronic devices towards artificial intelligence systems.
The neural signals produced by varying electrical stimulation parameters lead to characteristic neural circuit responses. However, the characteristics of neural circuits reconstructed by electrical ...signals remain poorly understood, which greatly limits the application of such electrical neuromodulation techniques for the treatment of spinal cord injury. Here, we develop a dual electrical stimulation system that combines epidural electrical and muscle stimulation to mimic feedforward and feedback electrical signals in spinal sensorimotor circuits. We demonstrate that a stimulus frequency of 10-20 Hz under dual stimulation conditions is required for structural and functional reconstruction of spinal sensorimotor circuits, which not only activates genes associated with axonal regeneration of motoneurons, but also improves the excitability of spinal neurons. Overall, the results provide insights into neural signal decoding during spinal sensorimotor circuit reconstruction, suggesting that the combination of epidural electrical and muscle stimulation is a promising method for the treatment of spinal cord injury.
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