Deqi Chen

Genetic diversity in wild Dipsacus chinensis populations from China based on ISSR markers.

Wild Dipsacus chinensis plants in China have become endangered owing to over-harvesting and habitat fragmentation. We examined the genetic diversity and genetic structure of 90 individuals from three populations using inter-simple sequence repeat markers and found that 106 of 173 bands amplified by 22 informative and reliable primers were polymorphic. These findings correspond to a medium level of genetic diversity. At the species level, the estimates of parameters of genetic diversity were as follows: polymorphic loci (61.27%); effective number of alleles (1.3873); Neis genetic diversity (0.2202); Shannons information index (0.3235). At the population level, the estimates were polymorphic loci (9.53%); effective number of alleles (1.0419); Neis genetic diversity (0.0258); Shannons information index (0.0402). Neis coefficient of genetic differentiation was 0.8829, which is consistent with Shannons coefficient of genetic differentiation (0.8757). Most of the genetic variation existed among populations, and some differentiation may have resulted from habitat fragmentation and barriers to gene flow (gene flow = 0.0663). Combining our results with those of on-site field investigation, we conclude that the present genetic diversity and genetic structure of natural populations of D. chinensis have been strongly affected by harvesting and habitat fragmentation. We also propose strategies for the conservation of this plant.

Genetic structure and genetic diversity of single-variety Lonicera macranthoides populations in China, as indicated by SCoT markers

Lonicera macranthoides is an important traditional Chinese herb. The lack of information regarding the genetic structure and genetic relationships among its cultivars has hindered the conservation and utilization of this resource. This study used start codon targeted markers to assess the genetic diversity and other genetic characteristics of five single-variety L. macranthoides populations in China. Using 22 primers produced a total of 266 bands, of which 227 were polymorphic, indicating a high level of polymorphism. At the species level, genetic diversity was high: percentage of polymorphic loci (PPB) = 85.34%, effective number of alleles (NE) = 1.3479, Neis gene diversity (H) = 0.2075, and Shannons information index (Hsp, species level) = 0.3198. However, at the varietal population level, genetic diversity was lower, with averages of: PPB = 19.74%, NE = 1.0946, H = 0.0561, Hpop = 0.0850 (population level). Neis genetic differentiation coefficient was 0.7319, which is consistent with Shannons population genetic differentiation coefficient (0.7324). This indicates that most of the genetic variation in this species exists among the varietal populations. The differentiation among varieties may have been caused by artificial selection, mode of reproduction, and barriers to gene flow (0.1831). The genetic similarity coefficient ranged from 0.7222 to 0.9419. Phylogenetic analysis showed the five varieties to form two major clades. Results suggest that cultivar breeders should strengthen the exchange of germplasm and increase the mutual penetration of useful genes, which would broaden the hereditary basis of L. macranthoides.

Numerical Investigation on Bubble Growth and Sliding Process of Subcooled Flow Boiling in Narrow Rectangular Channel

In order to investigate single bubble evolution, a boiling phase change model in subcooled flow boiling is proposed in this paper, and VOF model combined with phase change model is adopted to simulate the single bubble growth and movement. The effects of flow velocity, liquid subcooling, wall superheat, and vapor-liquid contact angle are considered in this model. The predicted bubble growth curve agrees well with the experimental result. Based on the analysis of bubble shape evolution and temperature field, it is found that the average bubble growth rate, flow velocity, and dynamic contact angle have significant effect on the bubble shape evolution during the bubble growth and movement while the temperature gradient in superheated liquid does not change with bubble growing. The character of dynamic contact angle during bubble growth and movement is also obtained in different working condition.

Genetic diversity and population structure of wild Dipsacus asperoides in China as indicated by ISSR markers.

In order to evaluate the genetic diversity and genetic structure of wild Dipsacus asperoides, we surveyed genetic polymorphisms in 288 individuals from 12 populations using ISSR. A total of 240 bands were amplified, among which 190 were polymorphic loci. At the species level, genetic diversity was found to be abundant: PPB = 79.17%, NE = 1.2152, H = 0.1361, and Hsp = 0.2213. At the population level, genetic diversity was lower: PPB = 30.76 %, NE = 1.0786, H = 0.0897, and Hpop = 0.1375. The calculated Nei genetic differentiation coefficient was 0.3406, which is consistent with the calculated Shannon population genetic differentiation coefficient of 0.3787. This is commonly taken to indicate that most of the genetic variation existed within the populations. Gene flow was calculated as Nm = 0.9679, suggesting that gene exchange only occurred at a low level. Based on the Nei genetic distance, the 12 populations were divided into 4 categories. Our results suggest that D. asperoides has abundant genetic diversity and provides a foundation for the protection and improvement of germplasm resources.

Bubble Sliding Process on Subcooling Flow Boiling in Vertical Rectangular Narrow Channel

In present work, a visualized investigation was conducted to understand the phenomenon of bubble sliding on vertical heating wall with upward subcooled flow boiling in narrow rectangle channel with gaps of 2.5 mm. Experimental results show that the characteristics of bubble slipping are significantly influenced by mainstream velocity and temperature. With increasing mainstream velocity, bubble sliding distance and speed are all increased. In present working conditions, the bubbles sliding distance is of 3–10 times of the bubble departure diameter. Based on the energy balance on bubble sliding process, the impact of bubble sliding on the characteristics of heat transfer was analyzed as well. Considering the different mechanisms effect on heat transfer, such as micro-layer evaporation, transient conduction and single-phase forced convection between fluid and wall, the ratio of every mechanism was calculated and compared. Analysis results show that the bubble with sliding movement have significant heat transfer enhancement than that of the stationary bubbles. With the proposed concept of disturbance intensity of sliding bubble, the heat flux expressions caused by disturbance of sliding bubble or stationary have been proposed.Copyright

Experimental Investigation of Pressure Drop of Flow Boiling at Vertical Narrow Rectangular Channel

Narrow channel heat transfer element has been extensive adopted in engineering applications, especially at electronics technology, this kind of elements often be used to construct compact heat exchanger. Pressure drop of flow boiling at vertical channel with gaps of 1.7, 2.2 and 3.6 mm was experimentally investigated in this paper. The variation of the two-phase frictional multiplier vs. heat flux at various operating conditions was gotten experimentally, possible mechanism of the two-phase frictional multiplier trends of narrow channel were analyzed. Experimental results revealed that the two-phase frictional multiplier increased at lower flow rate and heat flux, as well as higher vapor quality, and dropped at wider flow gap. The multiplier can not be estimated by commonly used method for ordinary gap, thus a modified model of pressure drop for narrow channel was proposed considering the size effects of channel. The error of the predicted two-phase frictional multiplier is within ±15.4% compared with experimental results.Copyright

Experimental Investigation of Saturated Flow Boiling Heat Transfer of Vertical Narrow Rectangular Channel

Narrow rectangular channel has been widely used at evaporator of cryogenic engineering and electronics cooling. At present paper, saturated flow boiling heat transfer at vertical narrow rectangular channel with gaps of 1.0, 1.5 and 2.5 was experimentally investigated, the heat transfer characteristics at various operating conditions were tested and discussed, and the correlation of saturated boiling heat transfer coefficient was regressed used Least Square Method according to experimental results. It shows that heat transfer coefficient decreases at wider gaps and higher inlet pressure, and it increases at higher flow rate, heat flux and increased vapor quality. Compared with traditional correlation for ordinary channel, the discrepancy is significant. Considering the size effects, a new correlation was proposed to estimate the heat transfer coefficient. The error of the regressed correlation is within ±12%.Copyright

Departure and Lift-Off Point of Bubbles at Heating Wall in Vertical Channel

This paper proposed a theoretical model involving in conditions of bubble departure point and lift-off point, the principle and estimating method of individual forces have been proposed as well. The forces acted on growing bubble are, namely, surface tension force Fs , growth force of bubbles Fdu , shear lift force FsL , drag force of flow Fqs , hydrodynamic pressure force Fh , contact pressure force Fcp , buoyancy force Fb and bubble acceleration inertia force d(mvc )/dt as well. Horizontal and vertical momentum equations are presented according to forces balance of bubble, meanwhile, the estimating method of lean angle of bubble before departure also has been discussed.Copyright