Thermal energy storage offers enormous potential for a wide range of energy technologies. Phase-change materials offer state-of-the-art thermal storage due to high latent heat. However, spontaneous ...heat loss from thermally charged phase-change materials to cooler surroundings occurs due to the absence of a significant energy barrier for the liquid-solid transition. This prevents control over the thermal storage, and developing effective methods to address this problem has remained an elusive goal. Herein, we report a combination of photo-switching dopants and organic phase-change materials as a way to introduce an activation energy barrier for phase-change materials solidification and to conserve thermal energy in the materials, allowing them to be triggered optically to release their stored latent heat. This approach enables the retention of thermal energy (about 200 J g
) in the materials for at least 10 h at temperatures lower than the original crystallization point, unlocking opportunities for portable thermal energy storage systems.
Arylazopyrazole derivatives based on four core structures (4pzMe, 3pzH, 4pzH, and 4pzH-F2) and functionalized with a dodecanoate group were demonstrated to store thermal energy in their metastable Z ...isomer liquid phase and release the energy by optically triggered crystallization at −30 °C for the first time. Three heat storage–release schemes were discovered involving different activation methods (optical, thermal, or combined) for generating liquid-state Z isomers capable of storing thermal energy. Visible light irradiation induced the selective crystallization of the liquid phase via Z-to-E isomerization, and the latent heat stored in the liquid Z isomers was preserved for longer than 2 weeks unless optically triggered. Up to 92 kJ/mol of thermal energy was stored in the compounds, demonstrating remarkable thermal stability of Z isomers at high temperatures and liquid-phase stability at temperatures below 0 °C.
Consumption of dietary fat is one of the key factors leading to obesity. High-fat diet (HFD)-induced obesity is characterized by induction of inflammation in the hypothalamus; however, the temporal ...regulation of proinflammatory markers and their impact on hypothalamic appetite-regulating neuropeptide Y/agouti-related peptide (NPY/AgRP) neurons remains undefined.
Mice were injected with an acute lipid infusion for 24 h or fed a HFD over 8-20 weeks. Characterized mouse NPY/AgRP hypothalamic cell lines were used for in vitro experimentation. Immunohistochemistry in brain slices or quantitative real-time PCR in cell lines, was performed to determine changes in the expression of key inflammatory markers and neuropeptides.
Hypothalamic inflammation, indicated by tumor necrosis factor (TNF)-α expression and astrocytosis in the arcuate nucleus, was evident following acute lipid infusion. HFD for 8 weeks suppressed TNF-α, while significantly increasing heat-shock protein 70 and ciliary neurotrophic factor, both neuroprotective components. HFD for 20 weeks induced TNF-α expression in NPY/AgRP neurons, suggesting a detrimental temporal regulatory mechanism. Using NPY/AgRP hypothalamic cell lines, we found that palmitate provoked a mixed inflammatory response on a panel of inflammatory and endoplasmic reticulum (ER) stress genes, whereas TNF-α significantly upregulated IκBα, nuclear factor (NF)-κB and interleukin-6 mRNA levels. Palmitate and TNF-α exposure predominantly induced NPY mRNA levels. Utilizing an I kappa B kinase β (IKKβ) inhibitor, we demonstrated that these effects potentially occur via the inflammatory IKKβ/NF-κB pathway.
These findings indicate that acute lipid and chronic HFD feeding in vivo, as well as acute palmitate and TNF-α exposure in vitro, induce markers of inflammation or ER stress in the hypothalamic appetite-stimulating NPY/AgRP neurons over time, which may contribute to a dramatic alteration in NPY/AgRP content or expression. Acute and chronic HFD feeding in vivo temporally regulates arcuate TNF-α expression with reactive astrocytosis, which suggests a time-dependent neurotrophic or neurotoxic role of lipids.
Development of microbiota-directed foods (MDFs) that selectively increase the abundance of beneficial human gut microbes, and their expressed functions, requires knowledge of both the bioactive ...components of MDFs and the mechanisms underlying microbe-microbe interactions. Here, gnotobiotic mice were colonized with a defined consortium of human-gut-derived bacterial strains and fed different combinations of 34 food-grade fibers added to a representative low-fiber diet consumed in the United States. Bioactive carbohydrates in fiber preparations targeting particular Bacteroides species were identified using community-wide quantitative proteomic analyses of bacterial gene expression coupled with forward genetic screens. Deliberate manipulation of community membership combined with administration of retrievable artificial food particles, consisting of paramagnetic microscopic beads coated with dietary polysaccharides, disclosed the contributions of targeted species to fiber degradation. Our approach, including the use of bead-based biosensors, defines nutrient-harvesting strategies that underlie, as well as alleviate, competition between Bacteroides and control the selectivity of MDF components.
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•In vivo screen for fibers targeting specific human gut taxa in a defined community•Proteomics and forward genetics identify bioactive nutrients and their utilization•Interspecies competition controls the outcome of fiber-based microbiota manipulation•Artificial food particles as biosensors of community-wide glycan degradation
An in vivo approach that includes administration of artificial food particles explains mechanisms by which different human gut microbes utilize bioactive components of dietary fibers and paves a path towards the development of microbiota-directed foods that provide metabolic benefits to the host.
Observational properties of throat aurora are investigated in detail by using 7 year continuous auroral observations obtained at Yellow River Station (magnetic latitude 76.24°N). From our inspection, ...throat aurora is often observed under the condition of stripy diffuse aurora contacting with the persistent discrete auroral oval, and the long‐period throat aurora observations generally consist of intermittent subsequences of throat aurora brightening followed by poleward moving auroral form and throat aurora dimming. We also noticed that the orientation of throat aurora is aligned along the ionospheric convection flow, and its local time distribution shows clear dependence on the interplanetary magnetic field (IMF) By component. These observational results indicate that factors inside the magnetosphere may play important role on occurrence of throat aurora. We thus suggest that throat aurora may present the ionospheric signature of redistribution of reconnection rate on the magnetopause by cold magnetospheric plasma flowing into the reconnection site. In addition, we also found that the occurrence rate of throat aurora clearly decreases with increase of the IMF cone angle (arccos(|Bx|/B)), which is very similar with the occurrence rate of high‐speed jet (HSJ) observed in magnetosheath depending on the IMF cone angle. This is suggested as that the HSJs occurred outside the magnetosphere may also play important role for generation of throat aurora by triggering magnetopause reconnection or by direct impacting. Although further studies are needed to clarify how the throat auroras are generated in detail, the relevant observations about throat aurora have presented important implications on a variety open questions, such as distribution and generation of cold plasma structures in the outer magnetosphere, magnetopause deformation, and possible relation between HSJ and reconnection.
Key Points
Throat aurora always observed together with diffuse aurora indicate that the occurrence is affected by factors inside the magnetosphere
Occurrence rate of throat aurora decreasing with increase of the IMF cone angle implies that the occurrence is affected by outside factors
Occurrence of throat aurora is related with factors both inside and outside the magnetosphere
In this paper, a mechanical compression heat pump was coupled into the water-heated humidification dehumidification (HDH) desalination system, in which the condenser is applied to heat the seawater ...while the evaporator is considered to recover the carried heat from the discharged brine. In view of the integration mechanisms between the desalination unit and heat pump, mathematical models based on mass and energy equilibrium are built. Performance of the combined system, including the water production and gained-output-ratio (GOR), at the design conditions are first obtained. Moreover, the relevant influences from the prescribed critical parameters on the performance of the desalination system are simulated and analyzed. The simulation results show that the best performance of the coupled HDH desalination system, appearing as 82.12 kgh−1 for the water production and 5.14 for the GOR, is acquired at the balance condition of the dehumidifier. Two fully coupled cases, in which the heater or cooler is no longer required, when the air mass flow rate is located at 0.17 kgs−1 and 0.35 kgs−1, are found. During the influence analysis, a best value of pressure ratio, PR = 4, is found due to a highest value of GOR as 5.14 although the relevant value of water production is attained as 106.53 kgh−1 when the pressure ratio is fixed at 5. Furthermore, it is also observed that a lower value of the pinch temperature difference for the condenser, higher values of effectiveness both for the humidification and dehumidification, are effective to elevate the water production and the corresponding thermal efficiency.
•Coupled HDH desalination system is proposed.•Energy analysis of the coupled HDH desalination system is achieved.•Fully coupled conditions of the HDH desalination system are found.•Influences from the pressure ratio and effectiveness on the system performance are investigated.
Defects in materials give rise to fluctuations in electrostatic fields that reflect the local charge density, but imaging this with single atom sensitivity is challenging. However, if possible, this ...provides information about the energetics of adatom binding, localized conduction channels, molecular functionality and their relationship to individual bonds. Here, ultrastable electron-optics are combined with a high-speed 2D electron detector to map electrostatic fields around individual atoms in 2D monolayers using 4D scanning transmission electron microscopy. Simultaneous imaging of the electric field, phase, annular dark field and the total charge in 2D MoS
and WS
is demonstrated for pristine areas and regions with 1D wires. The in-gap states in sulphur line vacancies cause 1D electron-rich channels that are mapped experimentally and confirmed using density functional theory calculations. We show how electrostatic fields are sensitive in defective areas to changes of atomic bonding and structural determination beyond conventional imaging.
Azo-based photoswitches have shown promise as molecular solar–thermal (MOST) materials due to their ability to store energy in their metastable Z isomeric form. The energy is then released, in the ...form of heat, upon photoisomerization to the thermodynamically stable E form. However, obtaining a high energy density and recovering the stored energy with high efficiency requires the materials to be employed in the condensed phase and display a high degree of Z to E switching, both of which are challenging to engineer. Here, we show that arylazopyrazole motifs undergo efficient redox-induced Z to E switching in both the solution and the condensed phase to a higher completeness of switching than achieved photochemically. This redox-initiated pathway lowers the barrier of Z to E isomerization by 27 kJ/mol, while in the condensed phase, the efficiency of electrochemical switching is improved by over an order of magnitude relative to that in the solution state. The influence of the photoswitch’s phase, electrical conductivity, and viscosity on the electrochemical switching in the condensed phase is reported, culminating in a set of design rules to facilitate further investigations. We anticipate the use of an alternative stimulus to light will facilitate the application of MOST materials in situations where phototriggered heat release is unachievable or inefficient, e.g., indoor or at night. Furthermore, exploiting the electrocatalytic mechanism, whereby a catalytic amount of charge triggers Z to E switching via a redox process, bypasses the need for fine tuning of the photoswitching chromophore to achieve complete Z to E switching, thus providing an alternative approach to photoswitch molecular design.
The generally small Gibbs free energy difference between the Z and E isomers of hydrazone photoswitches has so far precluded their use in photon energy storing applications. Here, we report on a ...series of cyclic and acyclic hydrazones, which possess varied degrees of ring strain and, hence, stability of E isomers. The photoinduced isomerization and concurrent phase transition of the cyclic hydrazones from a crystalline to a liquid phase result in the storage of a large quantity of energy, comparable to that of azobenzene derivatives. We demonstrate that the macrocyclic photochrome design in combination with phase transition is a promising strategy for molecular solar thermal energy storage applications.
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