Association between sleep duration and high blood pressure in adolescents: a systematic review and meta-analysis

Context: Sleep has been assessed as a risk factor for health consequences. Among adults, excessively longer and shorter sleep durations are associated with high blood pressure (BP), but knowledge of the association between sleep duration and high BP among adolescents is limited. Objectives: To estimate the associations between sleep duration and high BP in adolescents. Methods: PubMed, Web of Science, and Cochrane databases were searched for eligible publications up until 20 November 2017. This study reviewed the reference lists from retrieved articles to search for relevant studies. Pooled odds ratios (ORs) were calculated using a random-effects meta-analysis. Sub-group and sensitivity analyses were conducted to identify heterogeneity. Publication bias was evaluated using Egger’s test. Results: Seven studies involving 21,150 participants were included, with ages ranging from 10–18 years. For primary analysis, compared with the reference sleep duration, the pooled OR for high BP was 1.51 (95% confidence interval [CI] = 1.04–2.19) for the short sleep duration overall. For long sleep duration, the pooled OR was 1.04 (95% CI = 0.78–1.38). Further sub-group analysis showed that short sleep duration had a higher risk of incident high BP in males (OR = 1.55, 95% CI = 1.24–1.93) than in females (OR = 1.23, 95% CI = 0.47–3.22). Conclusions: Among adolescents, and particularly male adolescents, short sleep duration may be a risk factor for high BP. More attention should be given to this lifestyle factor

A novel method for improving interfacial joining strength of vacuum brazed TiAl/GH3536 thin-walled structure by Au coating

Lightweight components and materials based on the joining of dissimilar materials have attracted wide attention in aerospace field. To obtain the optimized micromorphology and interfacial microstructure of the brazed joints, a new method of Au layer deposition on TiAl base metal was proposed to assist the brazing of TiAl plate to GH3536 thin-walled structure. Significantly, the design of Au layer affected the brazing fillet, dissolution of GH3536 core and the evolution of interface, and then the maximum force under tensile loading of the hetero-thin-walled structure. The effect of Au layer thickness on the interfacial microstructure and mechanical properties was discussed in detail. Upon the deposition of an Au layer with a concentration of 0.2 wt% onto the TiAl plate, the load-bearing capacity of the brazed thin-walled structure was observed to undergo a significant enhancement. Specifically, the maximum force sustained under tensile loading was measured to be 391 N, thereby exhibiting a remarkable increase of 117 % relative to that of the Au-free system.The authors gratefully acknowledge the financial support from the National Natural Science Foundation of China (Grant Nos. 52175307 and 51905125) and the Taishan Scholars Foundation of Shandong Province, China (No. tsqn201812128)

Diffusion Bonding of Ti₂AlNb Alloy and High-Nb-Containing TiAl Alloy: Interfacial Microstructure and Mechanical Properties

In this study, reliable Ti2AlNb/high-Nb-containing TiAl alloy (TAN) joints were achieved by diffusion bonding. The effects of bonding temperature and holding time on the interfacial microstructure and mechanical properties were fully investigated. The interfacial structure of joints bonded at various temperatures and holding times was characterized by scanning electron microscopy (SEM), energy dispersive spectrometer (EDS) and X-ray diffraction (XRD). The results show that the typical microstructure of the Ti2AlNb substrate/O phase/Al(Nb,Ti)2 + Ti3Al/Ti3Al/TAN substrate was obtained at 970 °C for 60 min under a pressure of 5 MPa. The formation of the O phase was earlier than the Al(Nb,Ti)2 phase when bonding temperature was relatively low. When bonding temperature was high enough, the Al(Nb,Ti)2 phase appeared earlier than the O phase. With the increase of bonding temperature and holding time, the Al(Nb,Ti)2 phase decomposed gradually. As the same time, continuous O phase layers became discontinuous and the Ti3Al phase coarsened. The maximum bonding strength of 66.1 MPa was achieved at 970 °C for 120 min

Microstructural Evolution and Mechanical Properties of Ti₂AlNb/GH99 Superalloy Brazed Joints Using TiZrCuNi Amorphous Filler Alloy

Dissimilar materials brazing of Ti2AlNb alloy to GH99 superalloy is of great pragmatic importance in the aerospace field, especially the lightweight space aircraft components manufacturing. In this work, TiZrCuNi amorphous filler alloy was used as brazing filler, and experiments were carried out at different brazing temperatures and times to investigate the changes in interfacial structures and properties of the joints. The typical interfacial microstructure was Ti2AlNb alloy/B2/β/Ti2Ni (Al, Nb) + B2/β + (Ti, Zr)2(Ni, Cu) + (Ti, Zr)(Ni, Cu)/(Cr, Ni, Ti) solid solution + (Ni, Cr) solid solution/GH99 superalloy when being brazed at 1000 °C for 8 min. The interfacial microstructure of the joints was influenced by diffusion and reaction between the filler alloy and the parent metal. The prolongation of brazing process parameters accelerated the diffusion and reaction of the liquid brazing alloy into both parent metals, which eventually led to the aggregation of (Ti, Zr)2(Ni, Cu) brittle phase and increased thickness of Ti2Ni (Al, Nb) layer. According to fracture analyses, cracks began in the Ti2Ni (Al, Nb) phase and spread with it as well as the (Ti, Zr)2(Ni, Cu) phase. The joints that were brazed at 1000 °C for 8 min had a maximum shear strength of ~216.2 MPa. Furthermore, increasing the brazing temperature or extending the holding time decreased the shear strength due to the coarse Ti2Ni (Al, Nb) phase and the continuous (Ti, Zr)2(Ni, Cu) phase

Effect of Different Mulch Types on Soil Environment, Water and Fertilizer Use Efficiency, and Yield of Cabbage

This study aimed to address the crop growth and development issues caused by environmental factors in the area of the Liupan Mountains in Ningxia. In this area, there is a large temperature difference between day and night due to drought and low rainfall from spring to summer. The effects of farmland mulching for cabbage on soil environment, water and fertilizer use efficiency, and on cabbage were studied by comparing white common mulch (WCM), black common mulch (BCM), white and black biodegradable mulch (WBM and BBM), black permeable mulch (BPM), and black-and-white composite mulch (BWCM). The types of mulch suitable for application in the region were selected after a comprehensive comparative analysis. The results suggested that soil temperature and water content decreased in the mulch of the two biodegradable mulches and the permeable mulch compared with the control (WCM). Meanwhile, soil water content significantly increased into the rainy season in the mulch of BPM. The overall index of soil enzyme activity was 11.8% and 5.2% higher in WBCM and BBM than that in WCM. The soil overall fertility index of WCM exceeded the other treatments by 16.3%, 33.0%, 25.6%, 36.6%, and 25.4%. The water use efficiency and fertilizer bias productivity of BBM and BPM mulch treatments were the highest among all treatments. The economic yield and economic efficiency of cabbage in BBM, BPM, and WBCM mulch treatments were among the best. A comprehensive analysis of the indicators by completing principal components and affiliation functions revealed that WBCM, BBM, and BPM ranked in the top three in comprehensive scores. In conclusion, black biodegradable mulch, permeable mulch, and black-and-white composite mulch can be applied to replace the white common mulch, with black biodegradable mulch treatment performing the best

Wettability and Spreading Behavior of Sn–Ti Alloys on Si₃N₄

The purpose of this study was to investigate the wetting behavior and interfacial reactions of Sn-Ti alloys, which has been widely applied to join ceramics with metals, on Si3N4 substrates. The isothermal wetting process of Sn-xTi alloys (x = 0.5, 1.0, 1.5, 2.0 and 2.5 wt.%) on Si3N4 was systematically studied from 1223 K to 1273 K through sessile drop methods. The microstructures of the interface were characterized by X-ray diffraction (XRD) and microscope (SEM). The active Ti element remarkably enhanced the wettability of Sn-xTi melts on Si3N4 substrates because of the formation of metallic reaction layers (Ti5Si3 and TiN). With the Ti content rising, thicker Ti5Si3 layer formed on the TiN phase inducing a lower equilibrium contact angle. The value of the lowest contact angle was 6°, which was obtained in the Sn-2.0Ti/Si3N4 system at 1273 K. Larger Ti5Si3 grains were found in Sn-2.5Ti melt and a higher final contact angle was obtained. Lower temperature increased the final contact angle and slowed down the spreading rate. The formation of reaction products was calculated thematically, and the spreading kinetics was calculated according to the reaction-driven theory. The spreading behavior of Sn-Ti alloy on Si3N4 ceramic was composed of rapid-spreading stage and sluggish-spreading stage. The calculated activity energy of spreading was 395 kJ/mol. Eventually, the wetting process of Sn-2.0Ti/Si3N4 system was successfully elucidated. These results provide significant guidance information for the brazing between metals and Si3N4 ceramic