Cytogenetic and morphological characteristics of new types of diploids (2n=22, 24, 40) derived from consecutive selfing of aneuploids in brassica crops     

Kwan Ho Lee  Hyoji Namai 《Euphytica》1993,72(1-2):15-22

Summary New types of diploids in Brassica crops were synthesized after three consecutive selfing of aneuploids derived from backcrossing of sesquidiploids (2n=29, AAC) with B. campestris (2n=20, AA). The cytogenetic and morphological characteristics of plants with 2n=22, 24 and 40 in the S₃ generation were analyzed in order to establish the extent in which these addition and polyploid lines were stabilized. A high frequency of 11_II (79.7%), 12_II (84.6%) and 20_II (100%), were observed at metaphase _I of pollen mother cells in 2n=22, 24 and 40 plants, respectively. The chromosome configuration at methaphase _II also indicates that a certain level of stability has been attained cytogenetically. Although pollen stainability was relatively high, the seed set percentage was still low. Variation in morphological characteristics indicate the incorporation of one or more chromosome pairs from the C genome of B. oleracea. Other diagnostic characters such as the formation of determinate inflorescence, branching from the base of the stem, and the shift from self-incompatibility to self-compatibility must have resulted from the interaction between A and C genomes. Thus plants with 2n=22, 24 and 40 have been stabilized to some extent and can be developed into new breeding lines of Brassica. It is suggested that limited pollination could be effective in increasing the seed fertility of these plants.  相似文献   

Amphotericin B potentiation of rifampicin as an antifungal agent against the yeast phase of Histoplasma capsulatum   总被引：17，自引：0，他引：17  

G S Kobbayashi  G Medoff  D Schlessinger  C N Kwan  W E Musser 《Science (New York, N.Y.)》1972,177(50):709-710

Rifampicin, at high concentrations, inhibited growth and RNA synthesis in the yeast phase of Histoplasma capsulatum. These effects were potentiated by low concentrations of amphotericin B. The combination of the two agents was fungicidal, whereas each alone, at much higher concentrations, was only fungistatic.  相似文献   

Direct measurements of the convective recycling of the upper troposphere     

Bertram TH  Perring AE  Wooldridge PJ  Crounse JD  Kwan AJ  Wennberg PO  Scheuer E  Dibb J  Avery M  Sachse G  Vay SA  Crawford JH  McNaughton CS  Clarke A  Pickering KE  Fuelberg H  Huey G  Blake DR  Singh HB  Hall SR  Shetter RE  Fried A  Heikes BG  Cohen RC 《Science (New York, N.Y.)》2007,315(5813):816-820

We present a statistical representation of the aggregate effects of deep convection on the chemistry and dynamics of the upper troposphere (UT) based on direct aircraft observations of the chemical composition of the UT over the eastern United States and Canada during summer. These measurements provide unique observational constraints on the chemistry occurring downwind of convection and the rate at which air in the UT is recycled. These results provide quantitative measures that can be used to evaluate global climate and chemistry models.  相似文献   

Effects of blend ratio and heat treatment on the properties of the electrospun poly(ethylene terephthlate) nonwovens     

Kwan Woo Kim  Keun Hyung Lee  Bong Seok Lee  Yo Seung Ho  Seung Jin Oh  Hak Yong Kim 《Fibers and Polymers》2005,6(2):121-126

Semicrystalline poly(ethylene terephthalate) (cPET)/amorphous poly(ethylene terephthalate) with isophthalic acid (aPET) blends with 100/0, 75/25, 50/50, 25/75, and 0/100 by weight ratios were dissolved in a mixture of trifluoroacetic acid (TFA)/methylene chloride (MC) (50/50, v/v) and electrospun via the electrospinning technique. Solution properties such as solution viscosity, surface tension and electric conductivity were determined. The solution viscosity slightly decreased as aPET content increased, while there was no difference in surface tension with respect to aPET composition. The characteristics of the electrospun cPET/aPET blend nonwovens were investigated in terms of their morphology, pore size and gas permeability. All these measurements were carried out before and after heat treatment for various blend weight ratios. The average diameter of the fibers decreased with increasing aPET composition due to the decrease in viscosity. Also, the morphology of the electrospun cPET/aPET blend nonwovens was changed by heat treatment. The pore size and pore size distribution varied greatly from a few nanometers to a few microns. The gas permeability after heat treatment was lower than that before heat treatment because of the change of the morphology.  相似文献   

Effect of collector temperature and conductivity on the chain conformation of nylon 6 electrospun nanofibers     

Remant Bahadur K. C.  Kwan Woo Kim  Shanta Raj Bhattarai  Hak Yong Kim  Duck Rae Lee 《Fibers and Polymers》2007,8(2):186-191

Electrospinning is a versatile process used to prepare micro- and nano- sized fibers from various polymer solution. Here, we dealt with the variation in the morphology of nylon 6 electrospun nanofibers and their polymorphism depending on the type and physical state of the collectors. SEM study showed that the fiber diameter was increased from 80 to 103 nm while it was collected in water bath. Similarly the fiber diameter and bonding was increased 103 to 115 nm with the temperature whereas it was linearly decreased 103 to 90 nm with the conductivity of the water bath. Spectroscopic analysis (FT-Raman, FT-IR) showed that the polymorphism of nylon 6 depended on the types of collector (aluminum sheet and water bath). Nylon 6 electrospun nanofibers display theγ-phase while collected in aluminum sheet andα-phase while collection in water bath. The extent of transformation fromγ- toα-phase was linearly increased with temperature and conductivity of the water bath.  相似文献   

Nursery habitat for Asian horseshoe crabs along the northern Beibu Gulf,China: Implications for conservation management under baseline gaps     

Xiaoyong Xie  Zhou Wu  Chun‐Chieh Wang  Yijian Fu  Xueping Wang  Peng Xu  Xing Huang  Yongyan Liao  Shiang‐Lin Huang  Kit Yue Kwan 《水产资源保护:海洋与淡水生态系统》2020,30(2):260-272

1. Identification, protection and enhancement of essential habitats are priority issues for management and restoration of exploited species. The shores utilized by Asian horseshoe crabs as nurseries were surveyed and the coastal habitat characteristics were described in the northern Beibu Gulf of China. Regression models were applied to explore species‐habitat relationships.
2. Fourteen and ten nursery sites were identified for Tachypleus tridentatus and Carcinoscorpius rotundicauda populations, respectively. Xiacun and Jinhaiwan in the eastern region of the northern Beibu Gulf were the essential nurseries for T. tridentatus, whereas Shanxin and Jiaodong in the western part were the primary nursery shores for C. rotundicauda. These shores supported high densities (4–6 individuals/100 m²) of juvenile horseshoe crab populations.
3. Mangrove and seagrass coverage area, coupled with sediment physico‐chemical parameters, particularly grain size, and the environmental heterogeneity of nursery habitats explained the distribution pattern of juvenile populations. Most juvenile populations were found along the outer fringe of mangroves in the small shallow estuary, particularly near outflows of tidal creeks with generally higher chlorophyll a and organic carbon contents. The distribution of high‐density juvenile populations of both species also overlapped with areas of seagrass patches.
4. These findings highlight the importance of mangroves and seagrasses in the nursery habitat use of Asian horseshoe crabs. Preserving the estuarine habitats with these vegetation types and identifying the high‐use nursery sites should be prioritised in China and other Asian places to conserve the declining Asian horseshoe crab populations.

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