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Objective This study aimed to examine the association between physical education classes and PA among adolescents from 50 low- and middle-income countries (LMICs). Methods A self-reported questionnaire from the Global School-based Student Survey (GSHS) was used to collect information on participation frequency of physical education classes and being physically active over the last week, as well as other control variables (e.g., sex, age, country, sedentary behavior). Multivariable logistic regression and a pooled meta-analysis were performed to explore the association and compared country-wise differences. Results Included adolescents aged from 13 to 17 years (n = 187,386, %boys = 51.7; mean age = 14.6 years), the prevalence of sufficient PA (meeting the PA guidelines) was 14.9%. The prevalence of 5 days or more to engage in physical education classes was 16.5%. Compared with adolescents who had 0 days for physical education classes, higher participation frequency was more likely related to sufficient PA (OR: 1 day = 1.34, 2 days = 1.66, 3 days = 1.67, 4 days = 1.79, 5 days or more = 2.46), these findings were also observed in both sexes. A moderate inconsistency on the association across the included countries was found (I2 = 53%, p Conclusions Participating in more physical education classes may be an effective approach to increase physical activity levels among adolescents in LMICs. However, promoting physical activity levels among adolescents in LMICs through physical education classes should consider more country-specific factors.

The aim of this study was to investigate the antitumor effects of two novel alkylated derivatives of quercetin, 7-O-butylquercetin (BQ) and 7-O-geranylquercetin (GQ), in MCF-7 human breast cancer cells and explore the possible cellular mechanism of the related apoptotic effects. Our data showed that BQ and GQ were more toxic to MCF-7 cells and had better accumulation ability in MCF-7 cells than quercetin. Morphological observations and DNA fragmentation pattern suggested that the derivatives could induce apoptosis in MCF-7 cells. Derivatives-induced apoptosis could not be reversed by Z-VAD-FMK and N-acetyl cysteine demonstrated that the apoptosis was independent on caspase and reactive oxygen species. Western blot assay showed that endonuclease G and apoptosis inducing factor might be relative to the apoptosis. Alkylation of quercetin at 7-O position can enhance the apoptosis inducing effect and cell accumulation ability relative to quercetin. This structural alteration brings changes on apoptosis pathway as well.

Rock weathering by carbonic acid has played a substantial role in both the global carbon cycle and related climate change. Carbonic acid as the major weathering agent has been accepted, whereas the importance of other acid (sulfuric, nitric or organic acids) as an agent is gradually recognized. Here, we examine sulfate dual-isotopic evidence ( δ 34 S SO 4 and δ 18 O SO 4 ) and water chemistry from the Jialing River (Sichuan Basin, Southwest China) to identify dissolved sulfate sources and the role of sulfuric acid in carbonate weathering. A survey was carried out at 29 sites where surface water was sampled during the rainy (July, 2008) and dry (February, 2009) seasons in the Jialing River. The chemical composition of river water was characterized by a dominance of Ca2+, Mg2+ and HCO 3 - , and SO 4 2 - , which accounted for more than 90% of the total ion concentrations. Water chemistry varied greatly in time and space, particularly for Na+, Cl−, and SO 4 2 - . This variation was a result of anthropogenic influences, such as acid deposition and domestic sewage inputs. Co-variation of the equivalent ratios of [Ca2+ + Mg2+] and [ SO 4 2 - + HCO 3 - ] indicate that it required significant additional SO 4 2 - to achieve ionic balance, which implied that sulfuric acid might play a relatively important role in carbonate weathering of this river basin. Water samples from the Jialing River were significantly rich in SO 4 2 - , and increased almost two times from 274 μM in the period of 1958–1990 to 499 μM in this study. The use of co-variations of δ 34 S SO 4 vs. δ 18 O SO 4 and of δ 18 O SO 4 vs. δ 18 O H 2 O allowed us to demonstrate that most of the sulfate in the waters of the Jialing River was derived from sulfide oxidation and atmospheric inputs by high sulfur-content coal combustion while the contribution of sulfate from domestic and industrial wastewater could be important in the dry season. Thus, the contribution of sulfuric acid, produced by such sulfide oxidation and the oxidation of atmospheric SO2 emitted from coal combustion, as a weathering agent is also confirmed.

An experimental investigation was carried out to study the heat transfer performance of a cylindrically micro-grooved heat pipe using aqueous nanofluids as the working fluids. The base liquid was distilled water, while, the five kinds of nanoparticles: Cu with two mean diameters of 40 nm and 20 nm, CuO with two mean diameters of 50 nm and 20 nm and SiO with a mean diameter of 30 nm were added respectively into the base liquid to compose different kinds of nanofluids. Experiments were performed under three steady operating pressures of 7.45 kPa, 12.38 kPa and 19.97 kPa, respectively. Effects of nanoparticle kind, nanoparticle size, nanoparticle mass concentration and operating pressure on the evaporation and condensation heat transfer coefficients, the maximum heat flux and the total heat resistance of the heat pipe were investigated, compared and discussed. Experimental results show that adding Cu and CuO nanoparticles into the base fluid can apparently improve the thermal performance of the heat pipe and there is an optimal nanoparticle mass concentration to achieve the maximum heat transfer enhancement. However, adding SiO nanoparticles into the base fluid will contrarily deteriorate the heat transfer performance. The main reason that causes these differences in the heat transfer performance results from the surface structure of the coating layer formed by sediment of nanoparticles on the heated surface.

An experimental study was performed to investigate the thermal performance of an inclined miniature grooved heat pipe using water-based CuO nanofluid as the working fluid. This study focused mainly on the effects of the inclination angle and the operating pressure on the heat transfer of the heat pipe using the nanofluid with the mass concentration of CuO nanoparticles of 1.0 wt%. The experiment was performed at three steady sub-atmospheric pressures. Experimental results show that the inclination angle has a strong effect on the heat transfer performance of heat pipes using both water and the nanofluid. The inclination angle of 45° corresponds to the best thermal performance for heat pipes using both water and the nanofluid. The present investigation indicates that the thermal performance of an inclined miniature grooved heat pipe can be strengthened by using CuO nanofluid.

Two-phase flow patterns of nitrogen gas and aqueous CuO nanofluids in a vertically capillary tube were investigated experimentally. The capillary tube had an inner diameter of 1.6 mm and a length of 500 mm. Water-based CuO nanofluid was a suspension consisted of water, CuO nanoparticles and sodium dodecyl benzol sulphate solution (SDBS). The mass concentration of CuO nanoparticles varied from 0.2 wt% to 2 wt%, while the volume concentration of SDBS varied from 0.5% to 2%. The gas superficial velocity varied from 0.1 m/s to 40 m/s, while the liquid superficial velocity varied from 0.04 m/s to 4 m/s. Experiments were carried out under atmospheric pressure and at a set temperature of 30 °C. Compared with conventional tubes, flow pattern transition lines occur at relatively lower water and gas flow velocities for gas–water flow in the capillary tube. While, flow pattern transition lines for gas–nanofluid flow occur at lower liquid and gas flow velocities than those for gas–water in the capillary tube. The effect of nanofluids on the two-phase flow patterns results mainly from the change of the gas–liquid surface tension. Concentrations of nanoparticles and SDBS have no effects on the flow patterns in the present concentration ranges.

An experimental study was performed to understand the nucleate boiling heat transfer of water–CuO nanoparticles suspension (nanofluids) at different operating pressures and different nanoparticle mass concentrations. The experimental apparatus is a miniature flat heat pipe (MFHP) with micro-grooved heat transfer surface of its evaporator. The experimental results indicate that the operating pressure has great influence on the nucleate boiling characteristics in the MFHP evaporator. The heat transfer coefficient and the critical heat flux (CHF) of nanofluids increase greatly with decreasing pressure as compared with those of water. The heat transfer coefficient and the CHF of nanofluids can increase about 25% and 50%, respectively, at atmospheric pressure whereas about 100% and 150%, respectively, at the pressure of 7.4 kPa. Nanoparticle mass concentration also has significant influence on the boiling heat transfer and the CHF of nanofluids. The heat transfer coefficient and the CHF increase slowly with the increase of the nanoparticle mass concentration at low concentration conditions. However, when the nanoparticle mass concentration is over 1.0 wt%, the CHF enhancement is close to a constant number and the heat transfer coefficient deteriorates. There exists an optimum mass concentration for nanofluids which corresponds to the maximum heat transfer enhancement and this optimum mass concentration is 1.0 wt% at all test pressures. The experiment confirmed that the boiling heat transfer characteristics of the MFHP evaporator can evidently be strengthened by using water/CuO nanofluids.