Enzymatic Preparation of Quinoa Protein Peptides and Its Lipid-lowering and Uric Acid-Lowering Activity in Vitro

To study the optimal enzymatic hydrolysis conditions and uric acid-lowering activity of lipid-lowering peptides from quinoa protein, this study used quinoa as raw material to extract protein, and used pancreatic lipase inhibition rate as the activity index. The enzymatic hydrolysis process of lipid-lowering peptides was optimized by single factor experiment and response surface analysis. The pancreatic lipase inhibitory activity, sodium taurocholate binding activity, cholesterol esterase inhibitory activity, xanthine oxidase inhibitory activity and amino acid composition of quinoa protein peptides were analyzed and characterized. The results showed that the optimal enzymatic hydrolysis conditions of lipid-lowering peptides from quinoa were as follows: pH1.6, enzymatic hydrolysis temperature 42.9 ℃, substrate concentration 3.03%, enzymatic hydrolysis time 1 h and enzyme to substrate ratio 0.2%. The theoretical value of inhibition rate of pancreatic lipase was 90.43%, and the actual value was 90.93%±0.10%. The optimal enzymatic hydrolysates showed excellent effect of lowering lipid in vitro. The IC50 of pancreatic lipase inhibition rate and cholesterol esterase inhibition rate were 7.49 μg/mL and 4.73 mg/mL, respectively. Meanwhile, the EC50 of taurocholic sodium binding rate was 0.53 mg/mL. In addition, the optimal enzymatic hydrolysates showed good xanthine oxidase inhibition effect (IC50=5.97 mg/mL), indicating that it had the uric acid-lowering effect in vitro. Amino acid analysis showed that quinoa protein peptides were rich in essential amino acids (34.23%), and the percentage of hydrophobic amino acid and acidic amino acid were 34.11% and 31.66%, respectively. The quinoa protein peptides had high lipid-lowering and uric acid-lowering activities in vitro, which provided a theoretical basis for the high-value application of quinoa protein peptides

Effect of non-condensable gas on the startup of a loop heat pipe

It is essential to address the startup issues prior to the wide application of loop heat pipes (LHPs) in both space and terrestrial surroundings. As non-condensable gas (NCG) is an important factor affecting the startup behavior, its effects on the startup performance of an ammonia-stainless steel LHP with and without preconditioning were experimentally investigated in this work. Nitrogen with controlled amounts was used to simulate the NCG, and the temperature overshoot, liquid superheat and startup time were employed as the evaluation criteria. Four situations relating to initial liquid/vapor distribution in the evaporator were examined: (1) both evaporator core and vapor grooves are filled with liquid, (2) vapor exists in vapor grooves and the evaporator core is filled by liquid, (3) vapor grooves are filled by liquid and vapor exists in the evaporator core, and (4) vapor exists in both evaporator core and vapor grooves. Experimental results showed that with NCG presence in the LHP, the startup could only proceed in situation 1 with preconditioning, while it could proceed in situations 1, 3 or 4 without preconditioning. For the startup in situation 1, a larger NCG inventory led to much degraded startup performance, and a higher startup heat load could benefit the startup. For the startup in situation 3, the most difficult startup situation, NCG resulted in a very high temperature overshoot, which may even exceed the maximum allowable value. For the startup in situation 4, the existence of NCG in the vapor grooves could facilitate the evaporation there, leading to a very desirable startup

Flow Distribution Characteristics in Microchannel Heat Sinks in Pumping Liquid Cooling System

With the continuous improvement of pump-driven liquid cooling requirements for electronic devices, the cooling requirements for multiple dispersed units are inevitable, resulting in higher requirements of equal cooling capacity for parallel microchannel evaporators. Because of the existence of negative slope region in the characteristic curve of two phase flow in microchannel sink, the flow excursion will occur. The flow distribution in the parallel microchannel evaporator is simulated with ammonia as the working medium, and the effects of inlet subcooling degree, heat flux and length of connecting pipe on flow characteristic curve in a microchannel evaporator are studied. Besides, the influence of flow excursion on the overall temperature distribution of evaporator, and the influence of heat flux, inlet subcooling degree, and length of connecting pipe on the flow distribution of two parallel evaporators are investigated. The results show that the flow excursion between evaporators does not necessarily deteriorate the heat transfer capacity of the system, and the arrangement of heating flux, inlet and outlet connecting pipes has a great influence on the stability of the parallel evaporator system

Experimental Investigation on the Heat Transfer Characteristics of Multi-Point Heating Microchannels for Simulating Solar Cell Cooling

Concentrating photovoltaic power generation technology is a highly efficient way of utilizing solar energy resources with the efficiency limited by cell cooling conditions. For the heat dissipation problem from multi-point solar cell cooling, a microchannel heat sink is used to resolve the issue. Ammonia is chosen as the working fluid and two diamond microchannel heat sinks in series for the 16 simulated solar cells cooling with typical size. The heat sink consists of 31 triangular microchannels, each with a hydraulic diameter of 237 μm and a flow path length of 40 mm. It is experimentally verified that the diamond microchannel heat sink has excellent multi-point heat source heat dissipation capability. The surface temperature of the heat source can be controlled below 65.9 °C under the heat flux of 351.5 W/cm2, and the maximum temperature difference between the multi-point heat sources is only 1.4 °C. The effects of heat flux, mass flux and inlet state on the flow boiling heat transfer capacity within the series heat sinks were investigated and the ranges of the operating conditions are as follows: heat flux 90.8–351.5 W/cm2, mass flux 108–611 kg/(m2s), saturation temperature 15–23 °C and inlet temperature 15–21 °C. The results show that within the range of experimental conditions, the flow boiling heat transfer capacity of the series heat sink increases with the increase of heat flux and is less influenced by the mass flux, showing the typical two-phase heat transfer characteristics dominated by the nucleation boiling mechanism. Between the upstream and downstream heat sinks, the thermal resistance of the upstream heat sink is larger and the temperature uniformity of the downstream heat sink is poor because of the difference of the inlet state

Application of high-thermal-conductivity diamond for space phased array antenna

Active phased array antenna typically featured high performance, high device integration, and high heat flux, making it difficult to dissipate heat. Diamond, the substance with the closest arrangement of atoms in nature, has the advantages of a high thermal conductivity and strong adaptability to the space environment. The batch applications of high-thermal-conductivity diamonds for the thermal management of the phased array antennas of the inter-satellite links were introduced in this paper. The diamond was developed by the direct-current arc-plasma chemical vapor deposition method. The product size, thermal conductivity, precision, and application scale all met the engineering requirements. The high-precision assembly of the diamond and the structural frame enabled the efficient heat collection and transfer from the distributed point heat sources of multiple transmit/receive (T/R) modules. Verified on the ground, the thermal matching design between the diamond and the metal frame exhibited an outstanding heat dissipation performance. After four satellites using the diamonds were launched, the flight data showed good antenna thermal control, with temperature gradients of the T/R modules less than 2.2 °C, further verifying the rationality and effectiveness of using high-thermal-conductivity diamonds in the thermal design and implementation of antennas

Novel Antioxidant Peptides from Pearl Shell Meat Hydrolysate and Their Antioxidant Activity Mechanism

Free radicals are associated with aging and many diseases. Antioxidant peptides with good antioxidant activity and absorbability are one of the hotspots in antioxidant researches. In our study, pearl shell (Pinctada martensii) meat hydrolysate was purified, and after identification by proteomics, six novel antioxidant peptides SPSSS, SGTAV, TGVAS, GGSIT, NSVAA, and GGSLT were screened by bioinformatics analysis. The antioxidant peptides exhibited good cellular antioxidant activity (CAA) and the CAA of SGTAV (EC50: 0.009 mg/mL) and SPSSS (EC50: 0.027 mg/mL) were better than that of positive control GSH (EC50: 0.030 mg/mL). In the AAPH-induced oxidative damage models, the antioxidant peptides significantly increased the viability of HepG2 cells, and the cell viability of SGTAV, SPSSS, and NAVAA were significantly restored from 79.41% to 107.43% and from 101.09% and 100.09%, respectively. In terms of antioxidant mechanism by molecular docking, SGTAV, SPSSS, and NAVAA could tightly bind to free radicals (DPPH and ABTS), antioxidant enzymes (CAT and SOD), and antioxidant channel protein (Keap1), suggesting that the antioxidant peptides had multiple antioxidant activities and had structure–activity linkages. This study suggests that the antioxidant peptides above are expected to become new natural materials for functional food industries, which contribute to the high-value applications of pearl shell meat

High-Performance Thermal Interface Materials with Magnetic Aligned Carbon Fibers

Thermal interface materials with high thermal conductivity and low hardness are crucial to the heat dissipation of high-power electronics. In this study, a high magnetic field was used to align the milled carbon fibers (CFs, 150 μm) in silicone rubber matrix to fabricate thermal interface materials with an ordered and discontinuous structure. The relationship among the magnetic field density, the alignment degree of CFs, and the properties of the resulting composites was explored by experimental study and theoretical analysis. The results showed higher alignment degree and enhanced thermal conductivity of composites under increased magnetic flux density within a certain curing time. When the magnetic flux density increased to 9 T, the CFs showed perfect alignment and the composite showed a high thermal conductivity of 11.76 W/(m·K) with only 20 vol% CF loading, owing to the ordered structure. Meanwhile, due to the low filler loading and discontinuous structure, a low hardness of 60~70 (shore 00) was also realized. Their thermal management performance was further confirmed in a test system, revealing promising applications for magnetic aligned CF–rubber composites in thermal interface materials

Antioxidant Activity and Mechanism of Resveratrol and Polydatin Isolated from Mulberry (Morus alba L.)

Natural stilbenes have unique physiological effects, such as anti-senile dementia, anti-cancer, anti-bacterial, lowering blood lipid, and other important biological functions, which have attracted great attention from scholars in recent years. In this study, two stilbene compounds, resveratrol (RES) and polydatin (PD), were isolated from Mulberry (Morus alba L.), and their antioxidant activity and mechanism were investigated. The results showed that the contents of RES and PD in mulberry roots were 32.45 and 3.15 μg/g, respectively, significantly higher than those in mulberry fruits (0.48 and 0.0020 μg/g) and mulberry branches (5.70 and 0.33 μg/g). Both RES and PD showed high antioxidant potential by DPPH, ABTS free-scavenging methods, and ORAC assay, and provided protection against oxidative damage in HepG2 cells by increased catalase (CAT) activity, superoxide dismutase (SOD) activity, and Glutathione (GSH) content, and decreasing generation of reactive oxygen species (ROS), lactate dehydrogenase (LDH) level, and malondialdehyde (MDA) content. Therefore, RES and PD treatment could be effective for attenuating AAPH-induced oxidative stress in HepG2 cells. This study will promote the development and application of stilbene compounds. Furthermore, the RES and PD could be used as antioxidant supplements in functional foods, cosmetics, or pharmaceuticals, contributing to health improvement