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Open access

H. Ozawa, J. Watanabe, H. Chen, K. Isoda and A. Watanabe

Abstract

To clarify the relationship between the impact of phenological and/or artificial factors on seed quality, we measured the numbers of strobili on nematode-resistant Pinus densiflora clones grown in an immature and relatively small scale (700 m2) seed orchard. In addition, we established the clonal identities of all ramets, identified the paternal parent of the seeds, and assessed the resistance of seedlings to nematode infection. We also clarified the quantitative differences of strobili among clones; one clone produced 86.4% and 70.8% of all male strobili and female strobili, respectively. However, given that the total contamination ratio of the orchard was 82.0%, immigrant pollen had a larger impact on the success of actual crossing than phenology. Seedlings with a resistant maternal parent were resistant, even when their paternal parent was from outside the orchard. Two unselected clones were also planted in the seed orchard, one of which was not resistant and was associated with a maternal contribution of 34.7% of all seed stock. These findings suggest that, despite having a large impact on the crossing, immigrant pollen has a minor impact on seed resistance. Conversely, unselected and nonresistant clones have a marked impact on seed resistance. We concluded that artificial factors have larger impact on the seed quality than phenological factors in this orchard and the seeds will be of sufficient quality for supplying the market once nonresistant clones have been removed from the orchard.

Open access

Y. H. Li, X. Y. Kang, S. D. Wang, Z. H. Zhang and H. W. Chen

Abstract

Efficient methods for obtaining unreduced female gametes are needed for triploid induction in Populus alba x P. glandulosa. A cytological study of MMCs and PMCs meiosis and staminate floral elongation revealed that there was a close association between MMCs meiotic stage and male bud phenology during development under the same environment conditions. Female buds of Populus alba x P. glandulosa were treated with 0.5% colchicine solution at the selected meiotic stages based on male bud phenology. The treated buds were pollinated with pollen of P. tomentosa. A high rate of unreduced female gametes occurred in late leptotene and pachytene stages of MMC, as evidenced by a relatively higher percentage of triploids in the progeny, when compared to progeny from colchincine application at other meiotic stages. The present results demonstrated that male bud phenology can be used to guide colchicine applications to female buds and cause a more efficient production of triploids.

Open access

Li Chen, Long Xiang, Michael H. Young, Jun Yin, Zhongbo Yu and Martinus Th. van Genuchten

Abstract

The Green-Ampt (GA) model is widely used in hydrologic studies as a simple, physically-based method to estimate infiltration processes. The accuracy of the model for applications under rainfall conditions (as opposed to initially ponded situations) has not been studied extensively. We compared calculated rainfall infiltration results for various soils obtained using existing GA parameterizations with those obtained by solving the Richards equation for variably saturated flow. Results provided an overview of GA model performance evaluated by means of a root-meansquare- error-based objective function across a large region in GA parameter space as compared to the Richards equation, which showed a need for seeking optimal GA parameters. Subsequent analysis enabled the identification of optimal GA parameters that provided a close fit with the Richards equation. The optimal parameters were found to substantially outperform the standard theoretical parameters, thus improving the utility and accuracy of the GA model for infiltration simulations under rainfall conditions. A sensitivity analyses indicated that the optimal parameters may change for some rainfall scenarios, but are relatively stable for high-intensity rainfall events.

Open access

Y. H. Peng, Z. X. Lu, K. Chen, O. Luukkanen, H. Korpelainen and Chun Yang Li

Abstract

In this study, the genetic diversity of Populus cathayana Rehd was investigated using microsatellite markers. In a total of 150 individuals collected from six natural populations in the southeastern part of the Qinghai-Tibetan Plateau in China, a high level of microsatellite polymorphism was detected. At the seven investigated microsatellite loci, the number of alleles per locus ranged from 5 to 16, with a mean of 11.3, the observed heterozygosities across populations ranged from 0.408 to 0.986, with a mean of 0.792, and the expected heterozygosities across populations ranged from 0.511 to 0.891, with a mean of 0.802. The proportion of genetic differentiation among populations accounted for 37.3% of the whole genetic diversity. The presence of such a high level of genetic diversity could be attributed to the features of the species and the habitats where the sampled populations occur: The southeastern part of the Qinghai-Tibetan Plateau is regarded as the natural distribution and variation center of the genus Populus in China. Variation in environmental conditions and selection pressures in different populations, and topographic dispersal barriers could be factors associated with the high level of genetic differentiation found among populations. The populations possessed significant heterozygosity excesses, which may be due to extensive population mixing at the local scale. The cluster analysis showed that the populations are not strictly grouped according to their geographic distances but the habitat characteristics also influence the divergence pattern. In addition, we suggest that population SHY should be regarded as an ecologically divergent species of P. cathayana.

Open access

U. Kaka, Y.M. Goh, L.W. Chean and H.C. Chen

Abstract

Electroencephalography (EEG) has been reported as an objective, non-invasive and stress free technique for nociceptive studies. Electrical stimuli can be used to evaluate the efficacy of centrally acting agents. Peripheral nerve stimulator can be a good and cheap source of electric stimulus for studies of nociception, and studies evaluating analgesic effect of drugs under EEG. In this study suitability of peripheral nerve stimulator, and milliamperage for nociceptive studies under electroencephalography were evaluated. Six dogs were subjected to electric stimulus of 20, 40, 60 and 80 milliamperes (mAs) before and after tramadol administration at 4 mg/kg IV. Electroencephalograph was recorded during electric stimulus prior tramadol (pre-tramadol) and during electric stimulus after tramadol (post-tramadol) under minimal anaesthesia. Anaesthesia was induced with propofol and maintained with halothane at a stable concentration between 0.85 and 0.95%. Pre-tramadol median frequency (MF) increased significantly (p<0.05) at 40, 60 and 80 mAs post-electric stimulus compared to baseline MF. No difference in pre-tramadol MF was observed between 60 and 80 mAs. Tramadol produced significant effect by depression of MF at all intensities. The effect was less evident at 80 mAs. The results revealed that tramadol produced evident effect between 20 and 60 mAs. Thus, it is concluded that nerve stimulator can be used with the current between 20 and 60 mAs for nociceptive studies.

Open access

G. Chen, Y. Wang, C. Zhao, H. Korpelainen and C. Li

Abstract

Hippophae rhamnoides L., a dioecious and deciduous shrub species, occupies a wide range of habitats in the Wolong Nature Reserve, Southwest China. Our present study investigated the pattern of genetic variation and differentiation among five natural populations of H. rhamnoides, occurring along an altitudinal gradient that varied from 1,800 to 3,400 m above sea level in the Wolong Natural Reserve, by using ISSR markers. Based on fingerprinting patterns generated by fifteen primers, high levels of genetic variation were present within populations and subpopulations. Substantial genetic divergence was observed among populations, and also among female and male subpopulations, the GST values equaling 0.182, 0.222, and 0.238, respectively. Such considerable divergence present among populations and subpopulations may be caused by complex topography which effectively restricts gene flow, and by variable climatic conditions at different altitudes which may cause varying selective pressures. A significantly positive correlation between genetic and altitudinal distances was detected for the five populations and female subpopulations of H. rhamnoides. The cluster analysis including all populations or male subpopulations resulted in three altitude groups. Our results suggest that altitudinal gradients may be the prime cause affecting the genetic variation pattern of different populations and subpopulations in H. rhamnoides in the Wolong Nature Reserve, Southwest China.

Open access

W. Li, J. Chen, H. Liang and C. Li

Abstract

The effect of porosity on high temperature compression and creep behavior of porous Cu alloy for the new molten carbonate fuel cell anodes was examined. Optical microscopy and scanning electron microscopy were used to investigate and analyze the details of the microstructure and surface deformation. Compression creep tests were utilized to evaluate the mechanical properties of the alloy at 650 °C. The compression strength, elastic modulus, and yield stress all increased with the decrease in porosity. Under the same creep stress, the materials with higher porosity exhibited inferior creep resistance and higher steadystate creep rate. The creep behavior has been classified in terms of two stages. The first stage relates to grain rearrangement which results from the destruction of large pores by the applied load. In the second stage, small pores are collapsed by a subsequent sintering process under the load. The main deformation mechanism consists in that several deformation bands generate sequentially under the perpendicular loading, and in these deformation bands the pores are deformed by flattering and collapsing sequentially. On the other hand, the shape of a pore has a severe influence on the creep resistance of the material, i.e. every increase of pore size corresponds to a decrease in creep resistance.

Open access

Y Li, K-W Choy, H-N Xie, M Chen, W-Y He, Y-F Gong, H-Y Liu, Y-Q Song, Y-X Xian, X-F Sun and Xin-Jie Chen

Abstract

This study was conducted to describe a prenatal case of congenital hydrocephalus and hemivertebrae with a 6q terminal deletion and to investigate the possible correlation between the genotype and phenotype of the proband. We performed an array-based comparative genomic hybridization (aCGH) analysis on a fetus diagnosed with congenital hydrocephalus and hemivertebrae. The deletion, spanning 10.06 Mb from 6q25.3 to 6qter, was detected in this fetus. The results of aCGH, karyotype and fluorescent in situ hybridization (FISH) analyses in the healthy parents were normal, which confirmed that the proband’s copy- number variant (CNV) was de novo. This deleted region encompassed 97 genes, including 28 OMIM genes. We discussed four genes (TBP, PSMB1, QKI and Pacrg) that may be responsible for hydrocephalus while the T gene may have a role in hemivertebra. We speculate that five genes in the 6q terminal deletion region were potentially associated with hemivertebrae and hydrocephalus in the proband.

Open access

R. Li, L. J. Chen, M. Su, Q. Zeng, H. Li and Y. Liu

Abstract

The friction and wear properties of 201HT aluminum alloys and the corresponding competitive coupons were tested on an electrohydraulic servo face friction and wear testing machine (MM-U10G). The microstructures of the competitive coupons were investigated by scanning electron microscopy (SEM) and consequently the corresponding friction and wear mechanisms were studied. The results demonstrated that: (1) the best competitive material of friction and wear performance of the 201HT was the 201HTC. (2) the 201HTC modified by carbon following the initial mill for oil storage of the micro-groove to be produced, increased the corresponding lubrication performance reduced the friction coefficient and wear rate effectively. (3) the 201HT-201HTC could obtain both better friction and wear mainly due to the initial process of grinding following the 201HT plastic deformation occurred in the surface and the formation of a series of re-melting welding points, whereas the 201HT material hardness would be similar to the 201HTC material hardness, which led into the competitive material friction and wear performance improvement.

Open access

J. Wang, X. Y. Kang, D. L. Li, H. W. Chen and P. D. Zhang

Abstract

Diploid (2n) eggs were induced by treating developing embryo sacs of Populus with colchicine solution, in order to produce triploid plants. The optimal pollinated time of female catkins was confirmed as timing point for each treatment. When female catkins of P. pseudo-simonii x P. nigra ‘Zheyin3#’ had become 5.62 ± 0.13 cm long 84 h after they emerged from their bract scales and all stigmas were exposed, pistils all over the entire catkin had optimal stigma receptivity. Observation of paraffin sections showed that embryo sac development of ‘Zheyin3#’, which initiated 12 h before pollination and finished 132 h after pollination, was a successive and asynchronous process. Generative cell division of pollen of the male parent P. x beijingensis took place 3-16 h after pollination. Catkins of 18-96 h after pollination of ‘Zheyin3#’ were treated with colchicine solution. In the progeny, twenty three triploids were detected by chromosome counting and the highest rate of triploids was 66.7% in one treatment. The rate of triploid yield was positively correlated with the frequency of four-nucleate embryo sacs (r = 0.6721, p = 0.0981) and was not significantly correlated with the percentages of uni-, twoand eight-nucleate embryo sac (r = -0.1667, p = 0.7210, r = -0.3069, p = 0.5031 and r = 0.0189, p = 0.9679, respectively), suggesting that the third mitotic division of embryo sac may be the effective stage to induce 2n eggs. Through this approach, completely homozygous 2n eggs can be produced. Its significance for plant breeding is discussed.