Cancer stem cells (CSCs) are inherently resistant to chemotherapy, and CSCs in chemotherapy-failed recurrent tumors are enriched; however, the cellular origin of chemotherapy-induced CSC enrichment ...remains unclear. Communication with stromal fibroblasts may induce cancer cell dedifferentiation into CSCs through secreted factors. We recently demonstrated that fibroblast-derived exosomes promote chemoresistance in colorectal cancer (CRC). Here, we report that fibroblasts confer CRC chemoresistance via exosome-induced reprogramming (dedifferentiation) of bulk CRC cells to phenotypic and functional CSCs. At the molecular level, we provided evidence that the major reprogramming regulators in fibroblast-exosomes are Wnts. Exosomal Wnts were found to increase Wnt activity and drug resistance in differentiated CRC cells, and inhibiting Wnt release diminished this effect in vitro and in vivo. Together, our results indicate that exosomal Wnts derived from fibroblasts could induce the dedifferentiation of cancer cells to promote chemoresistance in CRC, and suggest that interfering with exosomal Wnt signaling may help to improve chemosensitivity and the therapeutic window.
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.
The past three decades have borne witness to many advances in the understanding of the molecular biology and treatment of nasopharyngeal carcinoma (NPC), an Epstein-Barr virus (EBV)-associated cancer ...endemic to southern China, southeast Asia and north Africa. In this Review, we provide a comprehensive, interdisciplinary overview of key research findings regarding NPC pathogenesis, treatment, screening and biomarker development. We describe how technological advances have led to the advent of proton therapy and other contemporary radiotherapy approaches, and emphasize the relentless efforts to identify the optimal sequencing of chemotherapy with radiotherapy through decades of clinical trials. Basic research into the pathogenic role of EBV and the genomic, epigenomic and immune landscape of NPC has laid the foundations of translational research. The latter, in turn, has led to the development of new biomarkers and therapeutic targets and of improved approaches for individualizing immunotherapy and targeted therapies for patients with NPC. We provide historical context to illustrate the effect of these advances on treatment outcomes at present. We describe current preclinical and clinical challenges and controversies in the hope of providing insights for future investigation.
•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.
► Increasing HTF inlet parameters can improve PCTES performance. ► The inlet parameters restrict each other for the rated solar collector. ► The PCTES performance can be effectively enhanced by ...enhanced tubes. ► The pressure drops caused by the enhanced tubes could almost be neglected.
Based on enthalpy method, numerical studies were performed for high temperature molten salt phase change thermal energy storage (PCTES) unit used in a dish solar thermal power generation system. Firstly, the effects of the heat transfer fluid (HTF) inlet temperature and velocity on the PCTES performance were examined. The results show that although increasing the HTF inlet velocity or temperature can enhance the melting rate of the phase change material (PCM) and improve the performance of the PCTES unit, the two parameters will restrict each other for the fixed solar collector heat output. Then three enhanced tubes were adopted to improve the PCTES performance, which are dimpled tube, cone-finned tube and helically-finned tube respectively. The effects of the enhanced tubes on the PCM melting rate, solid–liquid interface, TES capacity, TES efficiency and HTF outlet temperature were discussed. The results show that compared with the smooth tube, all of the three enhanced tubes could improve the PCM melting rate. At the same working conditions, the melting time is 437.92min for the smooth tube, 350.75min for dimpled tube which is reduced about 19.9% and 320.25min for cone-finned tube which is reduced about 26.9% and 302.75min for helically-finned tube reduced about 30.7%. As a conclusion, the thermal performance of PCTES unit can be effectively enhanced by using enhanced tube instead of smooth tube. Although, the HTF pressure drops for the enhanced tubes are also larger than that of the smooth tube, the largest pressure drop (1476.2Pa) is still very lower compared with the working pressure (MPa magnitude) of the dish solar generation system. So, the pressure drops caused by the enhanced tubes could almost be neglected.
The present work investigates the effects of charged nanoparticles on thermal properties of phase change material (PCM). Nanoparticles (CuO) with different electrical charges were dispersed into ...paraffin (octadecane) to prepare nanocomposite phase change material (NPCM). Molecular dynamics method was used to study the thermal conductivity of NPCM and reveal the effect of the charged nanoparticle. The results show that the thermal conductivity of NPCM is promoted with increasing nanoparticle charges. Coulomb energy is nonlinearly increased with the increasing charge. Furthermore, the local density of atoms is also affected by the charged nanoparticle. The peak value of local density increases with increasing nanoparticle charges. Phonon density of state (PDOS) is calculated to study the phonon transport in NPCM. Phonon scattering is weakened around the nanoparticle due to the existence of nanolayer. Moreover, the thickness of nanolayer is increased with the increasing charge, resulting in weaker phonon scattering and contributing to more thermal conductivity enhancement of NPCM. It can be a good way to control the thermal properties of NPCM by adjusting the nanoparticle charge.
•Charged nanoparticles enhance the thermal conductivity of NPCM.•Local density of atoms shows peaks and indicates nanolayer.•Coulomb energy is nonlinearly increased with increasing nanoparticle charges.•The thickness of nanolayer increases with increasing nanoparticle charges.
•Significant melting enthalpy reduction was found in NPCMs.•Interaction between nanoparticles and PCM contributes to the reduction.•A parameter was defined to evaluate the effect of the ...interaction.•Dense phase is the internal reason for NPCM melting enthalpy reduction.
In order to enhance the thermal conductivity of phase change material (PCM), many studies on preparation of composite PCM with nanoparticles (NPCM) have been performed. However, most of the studies only focused on PCM thermal conductivity enhancement, and ignored the melting enthalpy reduction caused by nanoparticles. In present paper, molecular dynamics (MD) method was adopted to study the effect of nanoparticles (CuO) on PCM (paraffin) melting enthalpy and to reveal the mechanism of PCM melting enthalpy reduction. The results showed that the melting enthalpy quickly decreased with the increase of nanoparticle mass fractions. For the NPCM with 19.72 wt.% nanoparticles, the melting enthalpy decreased by about 51.5%. The interactions between nanoparticles and PCM also contribute to melting enthalpy reduction except the nanoparticle mass fraction. Then, a parameter (Fc) was defined to reveal the effect of the interactions on NPCM melting enthalpy. With the nanoparticle mass fraction increasing, the interaction was strengthened and the value of Fc was quickly decreased, especially when the nanoparticle mass fraction was lower than 10 wt.%. The dense phase of paraffin was found around nanoparticles. The existence of dense phase caused by the interaction between nanoparticles and PCM is the internal reason for NPCM melting enthalpy reduction.
In order to enhance the performance of the latent heat storage (LHS) process and provide the criterion for the selection and match of the multistage PCMs, the effects of PCMs melting temperatures on ...the heat storage rate, entransy dissipation rate and heat storage quality were numerically analyzed based on the entransy theory. For the single stage LHS unit, although decreasing the PCM melting temperature can augment the heat storage rate, the lower melting temperature causes larger entransy dissipation and reduces the heat storage quality. The larger heat storage rate results in the larger entransy dissipation rate, which is accordant with the entransy dissipation extremum theory. For the two-stage LHS unit with reasonably matching the PCMs melting temperature, the heat storage rate can be augmented and the entransy dissipation rate can be reduced. Then the optimization for the match of the two-stage PCMs melting temperatures was performed based on the entransy theory. The results show that there is an optimal match of the two-stage PCMs melting temperatures to achieve the maximum heat transfer rate or the minimum entransy dissipation rate. And the formulas for the optimum two-stage PCMs temperatures were presented, which can provide the criterions for the selection and match of the PCMs.
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