Numerical analysis of the interaction of 3D compressible bubble clusters

Based on the bubble dynamic theory and the compressible two-phase flow solver of the open source software OpenFOAM, a numerical simulation study is carried out on the interactions of bubble clusters in a closed volume. The bubble dynamics and interactions of a single bubble, two bubbles, and four bubbles are investigated under the working conditions without and with the presence of a free surface. Through a parametric study, the qualitative patterns of the variations of the bubble collapse period, the volume compressibility, the bubble pressure peak value, and the breakdown, fusion, and separation phenomena with the parameters such as the bubble pressure, the radius size, the bubble spacing, and the distance from the free surface are obtained. The main factors affecting the bubble morphology and the dynamic characteristics are summarized from numerous parameter experiments. It is shown that, in the absence of a free surface, the main factors are the relative size of the bubbles, the pressure of the liquid, and the pressure differences among the bubbles, while in the presence of a free surface, the main factor is the pressure of the liquid between the upper surface of the bubble and the free surface.

Influences of various grazing systems on community biomass of a desert grassland in Inner Mongolia,China

This study investigated the effects of various grazing systems, including continuous grazing, rotational grazing, and no-grazing systems, on the community biomass in the Stipa breviflora Griseb desert grassland during the grazing seasons in 2005, 2006, and 2007, based on study sites established in 1999. We found that the seasonal dynamics of the aboveground biomass were quite similar among the three treatments, which reached peak values in period from August to September during each study year. The continuous grazing system reduced the aboveground biomass from 2005 to 2007 under drought conditions, and the rotational grazing and no-grazing systems maintained more aboveground biomass than the continuous grazing system did. The belowground biomass declined with the increase of soil depth among the three treatments, and in the surface 20-cm soil layer it accounted for more than 60% of the total biomass. The belowground biomass was found to be highly correlated with soil depth under rotational grazing. The total belowground biomass within the 0--100-cm soil layer for rotational grazing was sig- nificantly higher than for continuous grazing and no-grazing, and had 15,775 kg/ha more biomass. Our results demonstrate that conservative rotational grazing can alleviate grassland deterioration by reserving more aboveground and belowground biomass than the continuous grazing system does.

Effects of the grazing systems on germinable soil seed bank of desert steppe

We studied a soil seed bank in the Stipa breviflora desert steppe under three grassland management systems, namely continuous grazing, rotational grazing, and no grazing, from 1999 until 2007. The germinable seed bank species in rotational, continuous and no gazing were 11, 9 and 8 species, respectively. Rotational grazing increased the number of seed bank plant species and perenni- al grasses. The density of germinal soil seed bank was significantly higher in the enclosed area （19,533.33 seeds/m2） than those in rotational （3,233.33 seeds/mz） and continuous grazing areas （2,553.60 seeds/m2）. The vertical distribution of the soil seed bank had a similar trend： 75.06%-83.19% of the seeds are distributed in the top 0-5 cm soil layer, 14.16%-21.68% in the 5-10 cm lay- er, and 2.65%-4.95% in the 10-15 cm layer, which varied between the grazing treatments. Density of the soil seed bank was sig- nificantly higher in the enclosed area, and there was no significant difference between rotational and continuous grazing. The Margalef and Shannon-Wiener indices for the soil seed bank were higher for rotational grazing treatment than for continuous grazing. The Sorensen＇s similarity index for the soil seed bank between the enclosed and rotational grazing areas reached 0.857.

Food emulsifier glycerin monostearate aggravates phthalates'testicular toxicity by disrupting tight junctions'barrier function in rats

Objectives:This study aimed to investigate the effect of the widely used food emulsifier glycerin monostearate(GM)on testicular toxicity caused by the mixture of three commonly used phthalate esters(MPEs)in rats,and further to explore the underlying mechanism.Materials and Methods:Thirty male Sprague-Dawley rats were randomly divided into three groups.Rats were orally treated with 160 mg/kg/d MPEs in the MPEs group;coinstantaneously treated with 160 mg/kg/d MPEs and 200 mg/kg/d GM in the MPEs+GM group;and treated with the excipient in the control group.The intervention lasted for 5 weeks.Testis weight,epididymis weight,testicular histopathology,and serum testosterone were detected for testicular toxicity evaluation.The testicular ultrastructure,the tight junction proteins zonula occluden(ZO)-1,and claudin were measured for the mechanism exploration.Results:The body weight,epididymis,serum testosterone level,and anogenital distance in the MPEs+GM group were significantly decreased compared with control group(P<0.05);Testicular histopathological observation showed that shed spermatids were observed in the MPEs+GM group.Ultrastructural observation of testicular cells showed that the cristae number was decreased in some mitochondria in the MPEs group,whereas the cristae were fused and disappeared in most mitochondria in the MPEs+GM group.The tight junctions were broken in the MPEs+GM group;meanwhile,the expression of ZO-1 and claudin were altered in the MPEs+GM group(P<0.01).Conclusions:The results from this study indicated that GM aggravated MPEs'testicular toxicity,which might relate to the injured mitochondria and damaged tight junctions in testicular tissue.

Numerical analysis of deflection control of a gas plasma jet based on magnetohydrodynamic staggered electrode configuration

To control the deflection of the gas plasma jet, a new analytical method is proposed based on the Magnetohydrodynamic(MHD) technique. Based on the typical MHD power generation model, the applied voltage is applied to the staggered electrodes, that is, a pair of electrodes on the same side wall are connected to generate an axial current in the channel. Under the action of the magnetic field perpendicular to the direction of the flow, the plasma is subjected to electromagnetic forces perpendicular to these two directions, and the jet is deflected. The computational model including the Navier-Stokes equations coupled with electromagnetic source terms, the electric potential equation and Ohm’s law is solved. The deflection of the gas jet under the action of an electromagnetic field is observed, and the maximum deflection angle is about 14.8°. The influences of the electric field, magnetic field, and conductivity on the jet deflection are studied. Results show that although the influences of these three factors on the deflection are similar, and the effect of increasing the electric field strength is slightly greater, priority should be given to increasing the magnetic field strength from the perspective of reducing energy consumption. The Stuart number is introduced to assess the ability of electromagnetic force to control jet deflection. When the electromagnetic parameters are constant, this solution provides better control of low-density and low-speed fluid flows. The calculation results show that using the staggered electrode method configuration is feasible in terms of controlling the deflection of a plasma jet deflection.

Biochar amendment alters the partitioning of nitrate reduction by significantly enhancing DNRA in a paddy field

Using 15N tracer technique,we investigated the potential rates of denitrification,anaerobic ammonium oxidation,dis-similatory nitrate reduction to ammonium(DNRA),and their partitioning among nitrate reduction,as well as the N_(2)O emission rates in a paddy soil receiving various biochar(0%,0.03%,0.1%,0.5%,and 1.0%;w/w)and straw(0.1%)over six consecutive years.Results showed that except for the 1.0%amendment treatment,biochar significantly(P<0.05)increased denitrification rates by 10.19‒75.96%compared with non-biochar amended treatment,and that biochar significantly(P<0.05)increased DNRA rates by 1.63‒6.84 folds relative to non-biochar amended treatment.Conse-quently,biochar shifted more NO3-partitioning toward DNRA process,as suggested by the increased DNRA/(denitri-fication+DNRA)ratios from 1.60 to 13.18%.On the other hand,biochar significantly(P<0.05)reduced N_(2)O emission rates by 61.86-97.65%accompanied by a significant decrease in N_(2)O/(N_(2)O+N_(2))ratios(65.29-98.39%),indicating bio-char amendment facilitated the reduction of N_(2)O to N_(2).The promoting effects of biochar on DNRA rates and DNRA/(denitrification+DNRA)ratios were attributed to the increased carbon availability and the altered nitrate reducer communities.Collectively,our study suggests that biochar amendment in the paddy soil is helpful for N conservation by favoring nitrate partitioning toward DNRA process,which deepens our understanding of how biochar mediates N cycling in the paddy field.