盐化草地景观中的斑块形状指数及其生态学意义   总被引：23，自引：0，他引：23  

刘学录 《草业科学》2000,17(2):50-52

利用ＧＩＳ技术研究了盐化草地景观中的斑块形状指数及其生态学意义。研究结果表明,斑块形状指数在描述斑块和斑块的空间格局方面,与斑块的分维数一样具有明确的生态学意义,可以作为反映一定尺度上斑块和景观复杂程度的定量指标,斑块形状指数越小、斑块的形状越规则,简单,斑块形状指数越在,斑块的形状越复杂,斑块形状指数的变化范围比分维数要大,可以大于分维数的上限２。  相似文献   

果形素对新红星苹果坐果及果形指数的影响   总被引：1，自引：0，他引：1  

郭宝林  杨俊霞 《河北农业大学学报》1999,22(2):44-46

以盛果期新红星苹果树为试材,于盛花期喷施果形素１号,２号,３号,均可显著提高花序坐果率,果形指数。高桩果率和果实单果重,但对果实硬度,可溶性固形物,果实着色度均无显著作用。这３种果表素均能达到普洛马林的应用效果。  相似文献   

Digital image analysis of cross-sectional tracheid shapes in Japanese softwoods using the circularity index and aspect ratio     

Xiu-Ming Diao  Takeshi Furuno  Minoru Fujita 《Journal of Wood Science》1999,45(2):98-105

Image analysis was used in this study to develop a faster, more objective method for quantitatively measuring tracheid shapes on cross section. The morphological features were measured automatically using the circularity index and aspect ratio based on the skeletonized images. The rectangular and hexagonal similarities were introduced to evaluate the tracheid shapes. The results for 18 species of Japanese softwoods showed that the difference in tracheid shapes among the species could be successfully estimated using the quantitative method. In addition, the boundary of latewood might be evaluated based on the change in circularity indexes.The abstract of this study was presented at the 48th annual meeting of the Japan Wood Research Society, Shizuoka, April 1998  相似文献   

Study on the Lime Shape in the Essential System of Activated FA with Water Reducer     

Wang Zhi Lu Hao Qian Jueshi Meng Zhiliang 《保鲜与加工》1999,(1):38-41

This paper studies the lime shape in the essential system of activated FA with water reducer.It shows that the water reducer has passive influence on activation of FA when lime is unslaked,and it will have positive influence when lime is slaked.A primary analysis has been done.  相似文献   

在石棉气缸垫有限元分析中钢丝形状的选择     

卢本友  姜树李  杨少楠  郭晨海 《拖拉机与农用运输车》2009,36(4):85-87

利用ABAQUS软件,对石棉气缸垫缸口处不同形状钢丝进行静力分析,从各种方案中选择与实际模型相近的最佳方案,从而为解决在发动机机体组合件有限元分析中接触模型由于线-面接触而导致不能收敛、或很难收敛的问题,并提供理想的气缸垫钢丝替代模型。计算结果表明:截面水平宽度与实际模型截面圆直径相同时的方案最为理想。将该方案用在发动机机体组合件有限元接触模型中可以较快收敛和得到较高的计算精度。  相似文献   

Evaluation of commercial live bakers’ yeast, Saccharomyces cerevisiae as a growth and immunity promoter for Fry Nile tilapia, Oreochromis niloticus (L.) challenged in situ with Aeromonas hydrophila     

Mohsen Abdel-Tawwab  Azza M. Abdel-Rahman  Nahla E.M. Ismael 《Aquaculture (Amsterdam, Netherlands)》2008,280(1-4):185-189

This study was carried out to evaluate the use of commercial live bakers’ yeast, Saccharomyces cerevisiae as a growth and immunity promoter for Nile tilapia, Oreochromis niloticus (L.). Fish (0.33 g) were randomly distributed at 25 fish per 140-L aquarium and fed a diet containing 0.0, 0.25, 0.50, 1.0, 2.0, or 5.0 g yeast/kg diet for 12 weeks. After the 12-week experimental period, fish of each treatment were challenged by pathogenic Aeromonas hydrophila, which was given by interperitoneal (IP) injection and kept under observation for 10 days to record clinical signs and the daily mortality rate. The growth-promoting influences of bakers’ yeast were observed with fish and the optimum growth, feed utilization, and protein turn-over were obtained with 1.0–5.0 g yeast/kg diet. Also, yeast supplementation increased protein deposition in fish body. Biochemical parameters were improved in fish fed yeast up to 1.0 g/kg diet. Total fish mortality 10-days after IP injection with A. hydrophila and its count after incubation with fish serum decreased with the increase of yeast level in fish diets. However, the lowest fish mortality and bacterial counts were obtained in fish fed 5.0 g yeast/kg. These results indicate that bakers’ yeast supplement is promising as an alternative method to antibiotics for disease prevention in tilapia aquaculture, and the optimum level of live bakers’ yeast is about 1.0 g per kg diet.  相似文献   

C,N and P regeneration by a detritivorous fish, <Emphasis Type="Italic">Liza haematocheila</Emphasis> T. &; S.: effects of temperature,diet and body size     

Bin?KangEmail author  Weiwei?Xian 《Aquaculture International》2008,16(4):319-331

Detritus, as a nutrients reservoir, affects the trophic structure and dynamics of communities and supports a greater diversity of species and longer food chains. Detritivorous fish is an important organism to regenerate the nutrients from sediments. Despite the numerous studies on the nutrients cycle in fish, only a few attempts have been made to quantify the regenerating ability. In the present study, we chose the common detritivorous fish redeye mullet as the research object. Redeye mullet is also a common poly-culture fish in China. Diet, including a commercial diet mostly used in aquaculture and a home-made diet with contents close to detritus, was used and considered as a fixed factor. Temperature was also considered as a fixed factor as much research has shown that temperature has significant effects on fish metabolism. Moreover, body size was regarded as a covariate under analysis of covariance. Three key nutrients, namely carbon, nitrogen and phosphorus, were used to measure the nutrient-regenerating ability of redeye mullet under laboratory conditions. The results showed that the nutrient regeneration in percent of the consumption decreased with increasing temperature. Carbon and nitrogen regeneration of redeye mullet fed on commercial diet was lower than those of the home-made diet group, while the opposite was found for phosphorus. In each group, the amount of regenerated nutrients increased linearly with body size. Fed on the home-made diet, 5-g fish at 25°C can regenerate 210.822 mg C, 37.533 mg N and 0.727 mg P per day.  相似文献   

不同产地及不同世代龙须菜可溶性总蛋白的差异表达初探     

蔡文龙  孟春晓 《水产科学》2008,27(9)

以采自广东、福建和青岛海域的龙须菜雌配子体、栽培和野生龙须菜为试验材料,比较了它们的形态和适应性差别,并研究了各样品可溶性总蛋白的表达情况.结果表明,这些样品之间不仅在形态和适应性方面有较大差异,而且至少有16种可溶性蛋白在它们之间差异表达,这为龙须菜遗传育种提供了更可信的分子标识.该方法有望成为比传统的形态鉴定和分子标记更简便、有效的含胶藻鉴定手段.  相似文献   

Usefulness of flat bottom tanks on the settlement of spider crab (Maja squinado, Herbst) larvae     

Jorge Palma  Miguel Correia  & José P Andrade 《Aquaculture Research》2008,39(9):1005-1008

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Effects of electrical stimulation of ventral septal area on discharge of pyrogen-treated thermosensitive neurons in preoptic anterior hypothalamus region of rabbits     

DONG Jun  LI Chu-jie  LU Da-xiang  FU Yong-mei  YAN Liang 《园艺学报》2000,16(4):301-303

AIM and METHODS: To investigate the effect of electrical stimulation of ventral septal area (VSA) on discharge of pyrogen-treated thermosensitive neurons in preoptic anterior hypothalamus (POAH) region, the discharging rate of thermosensitive neurons in the POAH region of 32 New Zealand white rabbits were recorded by using extracellular microelectrode techinque. RESULTS: (1) Intraceretroventricularly (i c v) injection of interleukin-1_β(IL-1_β) caused decrease of discharging rate of warm-sensitive neurons and increased in discharging rate of cold-sensitive neurons in POAH regions. (2) These effects could be reversed by electrical stimulation of VSA. CONCLUSION: VSA may play a central role of negative regulation in thermoregulation of pyrogen-treated animal.  相似文献