The selection of working fluid and working conditions of the Organic Rankine Cycle (ORC) has a great effect on the system operation, and its energy efficiency and impact on the environment. The main ...purpose of this study is to develop a procedure to compare capabilities of working fluids when they are employed in solar Rankine cycles with similar working conditions. The Refprop 8.0 database with 117 organic fluids has been considered as the reference in this study. A procedure to compare ORC working fluids based on their molecular components, temperature–entropy diagram and fluid effects on the thermal efficiency, net power generated, vapor expansion ratio, and exergy efficiency of the Rankine cycle has been proposed. Fluids with the best cycle performance have been recognized in two different temperature levels within two different categories of fluids: refrigerants and non-refrigerants. Based on categories of solar collectors, 11 fluids have been suggested to be employed in solar ORCs that use low or medium temperature solar collectors. Collector efficiency improvement and use of the regenerative ORC instead of the basic cycle reduce irreversibility of a solar ORC. Calculation results show that for selected fluids, the theoretical limits for irreversibility reduction and exergy efficiency enhancement through collector efficiency improvement are 35% and 5% respectively, when the collector efficiency increases from 70% to 100%. The effect of regeneration on the exergy efficiency of the cycle is fluid dependent while the effect of collector efficiency improvement on the exergy efficiency of the cycle is nearly independent of fluid type. At the two temperature levels studied, higher molecular complexity results in more effective regenerative cycles except for Cyclohydrocarbons.
A highly efficient thermal strategy to manage a high-powered Li-ion battery package within the required safe temperature range is of great demand for electric vehicles (EVs) applications. A ...sandwiched cooling structure using copper metal foam saturated with phase change materials was designed. The thermal efficiency of the system was experimentally evaluated and compared with two control cases: a cooling mode with pure phase change materials and an air-cooling mode. The results showed that the thermal management with air natural convection cannot fulfill the safety demand of the Li-ion battery. The use of pure PCM can dramatically reduce the surface temperature and maintain the temperature within an allowable range due to the latent heat absorption and the natural convection of the melted PCM during the melting process. The foam-paraffin composite further reduced the battery's surface temperature and improved the uniformity of the temperature distribution caused by the improvement of the effective thermal conductivity. Additionally, the battery surface temperature increased with an increase in the porosity and the pore density of the metal foam.
•Cooling structure for Li-ion battery using foam-paraffin composite was designed.•Thermal management by air natural convection cannot fulfill battery safety demand.•Employment of pure PCM dramatically reduced battery surface temperature.•Integration of copper foam and paraffin further reduced battery temperature.•Battery surface temperature increased with increase in porosity and pore density.
•Effects of metal foams parameters on PCM LHS were investigated by LBM.•Increasing PPI improves heat conduction, but weakens natural convection.•Decreasing porosity improves TES rate, but decreases ...TES density.•An optimum structure with porosity of 0.94 and PPI of 45 is recommended.•An enhancement method with nonuniform porosity was proposed.
Lattice Boltzmann method (LBM) was used to investigate the latent heat storage (LHS) performance of metal foams/paraffin composite phase change material (CPCM). The effects of metal foams PPI (number of pores per inch) and porosity on PCM melting rate, heat storage capacity and heat storage density were investigated. The results show that the CPCM heat transfer performance is determined by both heat conduction and natural convection. Increasing PPI can enhance heat conduction, but weaken natural convection. When the porosity is small, increasing PPI can enhance LHS performance. When the porosity is large, decreasing PPI can enhance the performance. With porosity decreasing, CPCM heat storage rate is improved and the maximum heat storage capacity almost keeps constant, but the heat storage density dramatically reduces. An optimum metal foams structure with porosity of 0.94 and PPI of 45 is recommended. Further, a performance enhancement scheme with nonuniform metal foams porosity was proposed and numerically validated. The results show that the proposed scheme can improve the uniformity of the heat transfer process and enhance the heat transfer performance.
► A more detailed three-dimensional model of PTC was proposed by combining FVM and MCRT method. ► Corresponding codes and solving methods were developed and applied to an LS2 PTC. ► Numerical results ...proved that the model and method is feasible and reliable. ► More details of the characteristics in the receiver were revealed and discussed. ► Typical HTF types and residual gas conditions were further studied.
In this paper, a more detailed three-dimensional computational model of the whole parabolic trough solar collector (PTC) system and corresponding numerical simulations by combining the Finite Volume Method (FVM) and the Monte Carlo Ray-Trace (MCRT) method were presented. Corresponding codes and solving methods were also developed and applied to simulate and analyze the total involuted photo-thermal conversion process of an experimental LS2 PTC system. The numerical results were compared with experimental data and good agreement was obtained, proving that the model and method used in the present study is feasible and reliable. More details of the characteristics of solar concentrating, solar collecting, fluid dynamics, coupled heat transfer and the whole flow and temperature fields in the receiver were also revealed and discussed. Then some typical heat transfer fluid (HTF) types and residual gas conditions were further studied. It was revealed that the properties of these HTFs/conditions and their varying relations of the fluid temperature affected the characteristics of fluid dynamics, coupled heat transfer and the whole temperature distributions in the receiver, thus affected the thermal loss and the collector efficiency synthetically.
Abstract Previous data demonstrate that traumatic brain injury (TBI) activates autophagy, and increases microtubule-associated protein 1 light chain 3 (LC3) immunostaining mainly in neurons. However, ...the role of autophagy in traumatic brain damage remains elusive. The aim of the present study was to investigate the autophagic mechanisms participating in traumatic brain injury. The autophagy inhibitors 3-methyladenine (3-MA) and bafliomycin A1 (BFA) were administered with a single i.c.v. injection before TBI. We first examined the protein levels of Beclin-1 and LC3 II, which have been found to promote autophagy previously. Immunoblotting analysis showed that 3-MA pretreatment reduced post-TBI Beclin-1 and LC3-II levels, and maintained p62/SQSTM1 (p62) levels. In addition, double immunolabeling showed that the increased punctate LC3-II dots colocalizing with Propidium Iodide (PI)-stained nuclei at 24 h after injury, were partially inhibited by 3-MA pretreatment. Furthermore, inhibition of autophagy could reduce TBI-induced cell injury assessed with i.p. injection of PI and lesion volume, and attenuate behavioral outcome evaluated by motor test and Morris water maze. The neuroprotective effects were associated with an inhibition on TBI-induced up-regulation of LC3, Beclin-1, cathepsin B, caspase-3 and the Beclin-1/Bcl-2 ratio. Taken together, these data imply that the autophagy pathway is involved in the pathophysiologic responses after TBI, and inhibition of this pathway may help attenuate traumatic damage and functional outcome deficits.
•Nanocomposite phase change materials were prepared and characterized.•Larger specific surface area is more efficient to enhance specific heat.•Columnar structure is more efficient to enhance thermal ...conductivity.•Thermal conductivity enhancement is the key.•Single walled carbon nanotube is the optimal nanomaterial additive.
To enhance the performance of high temperature salt phase change material, four kinds of carbon nanomaterials with different microstructures were mixed into binary carbonate eutectic salts to prepare carbonate salt/nanomaterial composite phase change material. The microstructures of the nanomaterial and composite phase change material were characterized by scanning electron microscope. The thermal properties such as melting point, melting enthalpy, specific heat, thermal conductivity and total thermal energy storage capacity were characterized. The results show that the nanomaterial microstructure has great effects on composite phase change material thermal properties. The sheet structure Graphene is the best additive to enhance specific heat, which could be enhanced up to 18.57%. The single walled carbon nanotube with columnar structure is the best additive to enhance thermal conductivity, which could be enhanced up to 56.98%. Melting point increases but melting enthalpy decreases with nanomaterial specific surface area increase. Although the additives decrease the melting enthalpy of composite phase change material, they also enhance the specific heat. As a combined result, the additives have little effects on thermal energy storage capacity. So, for phase change material performance enhancement, more emphasis should be placed on thermal conductivity enhancement and single walled carbon nanotube is the optimal nanomaterial additive.
Aims/hypothesis
Arctigenin is a natural compound that had never been previously demonstrated to have a glucose-lowering effect. Here it was found to activate AMP-activated protein kinase (AMPK), and ...the mechanism by which this occurred, as well as the effects on glucose and lipid metabolism were investigated.
Methods
2-Deoxyglucose uptake and AMPK phosphorylation were examined in L6 myotubes and isolated skeletal muscle. Gluconeogenesis and lipid synthesis were evaluated in rat primary hepatocytes. The acute and chronic effects of arctigenin on metabolic abnormalities were observed in C57BL/6J and
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mice. Changes in mitochondrial membrane potential were measured using the J-aggregate-forming dye, JC-1. Analysis of respiration of L6 myotubes or isolated mitochondria was conducted in a channel oxygen system.
Results
Arctigenin increased AMPK phosphorylation and stimulated glucose uptake in L6 myotubes and isolated skeletal muscles. In primary hepatocytes, it decreased gluconeogenesis and lipid synthesis. The enhancement of glucose uptake and suppression of hepatic gluconeogenesis and lipid synthesis by arctigenin were prevented by blockade of AMPK activation. The respiration of L6 myotubes or isolated mitochondria was inhibited by arctigenin with a specific effect on respiratory complex I. A single oral dose of arctigenin reduced gluconeogenesis in C57BL/6J mice. Chronic oral administration of arctigenin lowered blood glucose and improved lipid metabolism in
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mice.
Conclusions/interpretation
This study demonstrates a new role for arctigenin as a potent indirect activator of AMPK via inhibition of respiratory complex I, with beneficial effects on metabolic disorders in
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mice. This highlights the potential value of arctigenin as a possible treatment of type 2 diabetes.
Roxadustat (FG-4592) is an oral inhibitor of hypoxia-inducible factor (HIF) prolyl hydroxylase that stimulates erythropoiesis and regulates iron metabolism. In phase 2 studies involving patients with ...chronic kidney disease, roxadustat increased levels of endogenous erythropoietin to within or near the physiologic range, along with increasing hemoglobin levels and improving iron homeostasis. Additional data are needed regarding the efficacy and safety of roxadustat for the treatment of anemia in patients with chronic kidney disease who are not undergoing dialysis.
In this phase 3 trial conducted at 29 sites in China, we randomly assigned 154 patients with chronic kidney disease in a 2:1 ratio to receive roxadustat or placebo three times a week for 8 weeks in a double-blind manner. All the patients had a hemoglobin level of 7.0 to 10.0 g per deciliter at baseline. The randomized phase of the trial was followed by an 18-week open-label period in which all the patients received roxadustat; parenteral iron was withheld. The primary end point was the mean change from baseline in the hemoglobin level, averaged over weeks 7 through 9.
During the primary-analysis period, the mean (±SD) change from baseline in the hemoglobin level was an increase of 1.9±1.2 g per deciliter in the roxadustat group and a decrease of 0.4±0.8 g per deciliter in the placebo group (P<0.001). The mean reduction from baseline in the hepcidin level (associated with greater iron availability) was 56.14±63.40 ng per milliliter in the roxadustat group and 15.10±48.06 ng per milliliter in the placebo group. The reduction from baseline in the total cholesterol level was 40.6 mg per deciliter in the roxadustat group and 7.7 mg per deciliter in the placebo group. Hyperkalemia and metabolic acidosis occurred more frequently in the roxadustat group than in the placebo group. The efficacy of roxadustat in hemoglobin correction and maintenance was maintained during the 18-week open-label period.
In Chinese patients with chronic kidney disease who were not undergoing dialysis, those in the roxadustat group had a higher mean hemoglobin level than those in the placebo group after 8 weeks. During the 18-week open-label phase of the trial, roxadustat was associated with continued efficacy. (Funded by FibroGen and FibroGen China Medical Technology Development; ClinicalTrials.gov number, NCT02652819.).
This paper proposes a review focused on exotic chemotaxis and cross-diffusion models in complex environments. The term exotic is used to denote the dynamics of models interacting with a time-evolving ...external system and, specifically, models derived with the aim of describing the dynamics of living systems. The presentation first, considers the derivation of phenomenological models of chemotaxis and cross-diffusion models with particular attention on nonlinear characteristics. Then, a variety of exotic models is presented with some hints toward the derivation of new models, by accounting for a critical analysis looking ahead to perspectives. The second part of the paper is devoted to a survey of analytical problems concerning the application of models to the study of real world dynamics. Finally, the focus shifts to research perspectives within the framework of a multiscale vision, where different paths are examined to move from the dynamics at the microscopic scale to collective behaviors at the macroscopic scale.
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