彩色图像颜色再现研究现状     

崔元日 《测绘学院学报》1994,(3)

本文基于颜色再现理论，讨论彩色印刷、彩色照相、彩色电视颜色再现原理，提出当前颜色再现研究的中心课题。  相似文献   

印刷颜色再现中的一些物理问题     

杨力 《测绘学院学报》1994,(4)

印刷颜色再现涉及物理学、生理学和心理学等学科。本文主要讨论了其中涉及的部分物理问题。重点阐述了印刷网点与人眼最小分辨角；纸张及油墨的光渗透、光散射对印刷品呈色效果的影响及解决方法；灰元取代的色度学基础。  相似文献   

Spawning and egg development ofPerca fluviatilis in Lake Zürich     

Markus Zeh  Erich Ritter  Georg Ribi 《Aquatic Sciences - Research Across Boundaries》1989,51(2):100-107

Egg survival and development rate of perch eggs were investigated in Lake Zürich, Switzerland. A transplant experiment was carried out to examine whether individual females choose different depths for spawning because of an expected advantage for the development of their eggs. Egg masses which had been deposited on fir branches stuck into the ground of the lake were either left untouched or transplanted horizontally or vertically at depths of 3 and 6 m. Spawning occurred between 28 April and 9 June 1987. Egg survival to the eye pigment stage (EPS) was high in all treatments ( , minimum 92%). There was no significant difference in egg survival between treatments, suggesting that females do not choose the spawning site because of individual fitness differences related to the depth of spawning. Early egg masses which were exposed to lower temperatures developed more slowly (120–140 day degrees to the EPS) than late egg masses which were exposed to higher temperatures (80–100 day degrees). The observed differences are in agreement with the hypothesis of a constant sum of day degrees necessary for egg development using the corrected formula derived by Guma'a (1978) which deducts an estimated threshold temperature of 5°C below which development of perch eggs effectively stops, from the actual temperature.  相似文献   

Predicting the reproduction strategies of several microalgae through their genome sequences     

Guo  Li  Yang  Guanpin 《中国海洋大学学报(英文版)》2015,14(3):491-502

Documenting the sex and sexual reproduction of the microalgae is very difficult, as most of the results are based on the microscopic observation that can be heavily influenced by genetic, physiological and environmental conditions. Understanding the reproduction strategy of some microalgae is required to breed them in large scale culture industry. Instead of direct observation of sex and sexual reproduction under microscope, the whole set or the majority of core meiosis genes may evidence the sex and sexual reproduction in the unicellular algae, as the meiosis is necessary for maintaining the genomic stability and the advantages of genetic recombination. So far, the available genome sequences and bioinformatic tools(in this study, homolog searching and phylogenetic analysis) allow us to propose that at least 20 core meiosis genes(among them ≥6 must be meiosis specific) are enough for an alga to maintain its sexual reproduction. According to this assumption and the genome sequences, it is possible that sexual reproduction was carried out by Micromonas pusilla and Cyanidioschyzon merolae, while asexual reproduction was adopted by Bigelowiella natans, Guillardia theta, Nannochloropsis gaditana, N. oceanica, Chlorella variablis, Phaeodactylum tricornutum and Thalassiosira pseudonana. This understanding will facilitate the breeding trials of some economic microalgae(e.g., N. gaditana, N. oceanica, C. variablis and P. tricornutum). However, the reproduction strategies of these microalgae need to be proved by further biological experiments.  相似文献   

Reproductive and growth strategies of Idotea balthica basteri (Pallas, 1772) population in the Bizerte lagoon (Tunisia,Southern Mediterranean)          下载免费PDF全文

Wahiba Zaabar  Mohamed Sghaïer Achouri  Faouzia Charfi‐Cheikhrouha 《Marine Ecology》2015,36(3):585-594

We analysed several life history traits of the marine isopod Idotea balthica basteri (Pallas, 1772) from the Bizerte lagoon, Southern Mediterranean Sea. Growth was continuous throughout the life of the animal with a high growth rate in the first life phase, and the growth curve was described according to von Bertalanffy's model. The lowest growth rate (0.23 mm) was recorded in winter (December, January and February) and the maximum rate (2.31 mm) between April and June. The total number of hatched eggs or embryos was positively correlated with the body length of ovigerous females. This population of I. balthica basteri was iteroparous, showing distinct strategies of reproduction. Large ovigerous females with high fecundity were collected during the whole sampling period, while breeding in smaller females with low fecundity was restricted to the period from late spring to early autumn, Manca size increased significantly with increasing female body size and there was also a significant trade‐off between manca size and the number of eggs per brood. Reproductive allocation, ranging between 17.1 ± 1.2% in winter and 23.2 ± 1.8% in summer, was positively correlated with female weight. Accordingly, parental investment in producing a juvenile varied between 1.02% per manca in winter to 3.38% in spring. Evaluated traits show that late summer and autumn cohorts have a K‐strategy, whereas cohorts born in winter and spring, and which exhibit a shorter life time, exhibit faster development, earlier reproduction and a smaller parental investment tending towards an r‐selected strategy.  相似文献   

砂旋复花的防风固沙作用   总被引：4，自引：0，他引：4  

韩广 《中国沙漠》1995,15(3):273-277

砂旋复花是一种沙生先锋多年生草本植物,营养繁殖能力极强,能很好地适应恶劣的流沙环境。研究结果表明,砂旋复花群聚的防风固沙作用非常突出,作为一种优良固抄植物,值得在北方沙区大力推广。  相似文献   

Factors affecting PAH residues in the lugworm Arenicola marina, a sediment feeding polychaete     

N. H. B. M. Kaag  M. C. Th. Scholten  N. M. Van Straalen 《Journal of Sea Research》1998,40(3-4)

Being a sediment feeder, the lugworm Arenicola marina could be a suitable candidate organism for the biomonitoring of sediment-bound contaminants in intertidal areas. Since lugworms are only rarely used in environmental monitoring, little is known about the natural variation in their body residue levels. In this study, we assessed the importance of seasonal fluctuations, spatial variation and sexual development to polycyclic aromatic hydrocarbon (PAH) residues in lugworms. Over a period of 15 months, lugworms were sampled along a contamination gradient in the Western Scheldt estuary in the Netherlands. A clear seasonal pattern in the body residue levels of PAH was observed, with lowest levels in March and highest levels just prior to the spawning season in September. During the spawning season the body residue levels showed a marked decrease. Although this seasonal pattern is apparently related to the reproductive cycle of the lugworm, no clear differences in body residue levels were found between animals with or without developed gonads. The contamination gradient, present in the estuary, was clearly reflected in the body residue levels of PAH. The expected gradient of internal concentrations was, however, absent in October, when the spawning period was not yet finished. The variation in lugworm body residue levels was smaller than the fluctuations in sediment PAH levels. It can be concluded that the lugworm is a suitable organism for the biomonitoring of sediment-bound contaminants, provided that attention is paid to its reproductive cycle.  相似文献   

光因子对离心列海链藻生殖的影响   总被引：4，自引：0，他引：4  

林均民  黄云鹤 《台湾海峡》1997,16(3):255-259

从厦门沿岸分离的离心列海链藻培养体，在光条件下发生在性生殖。实验结果获得，在２０℃温度下诱导该藻雌雄配子形成的最适光强度分别在１１３和３６μＥｉｎ／（ｍ２．ｓ），最适光照时间分别为８和１０ｈ。有性生殖只在３７μｍ宽度以下的细胞中发生，且精囊和卵囊的宽度大小十分相似。  相似文献   

毛嵌线螺的研究Ⅰ.繁殖及幼虫发生特征     

周永灿  陈国华  潘金培 《海洋学报》2000,22(2)

毛嵌线螺（ Ｃｙｍａｔｉｕｍ ｐｉｌｅａｒｅ）的繁殖过程包括交配、产卵、孵育及幼虫从卵囊中游出等４个阶段．交配一般在产卵前１０～１５ｄ进行,产卵后母体并不离开卵群,而是持续静伏在卵群的开口上进行孵育,直至其中的幼虫离开卵囊．温度和盐度对毛嵌线螺受精卵的发育有重要影响,在２２～３０℃的适宜温度区域内,将受精卵孵育成能自由生活的晚期面盘幼虫需４３８日度左右的总积温．毛嵌线螺受精卵的发育与其他前鳃类腹足动物相似,包括卵裂、囊胚期、原肠期及面盘幼虫期４个阶段．  相似文献   

盐度对浒苔(Ulva prolifera)微观繁殖体萌发生长及藻体繁殖的影响     

马薇薇  王楠  孙妍  孙松 《海洋与湖沼》2023,54(6):1622-1633

黄海绿潮起源于苏北浅滩,每年夏天漂移到青岛沿岸泛滥成灾,对生态环境造成严重破坏。苏北浅滩受沿岸径流输入影响,盐度变化范围大,青岛海域盐度较稳定,稍高于苏北浅滩。盐度对浒苔微观繁殖体萌发、藻体生长及繁殖过程具有重要作用,通过室内连续受控实验,系统研究了固定盐度(5、10、15、20、25、30、33、35)和变化盐度(盐度逐渐降低)对浒苔微观繁殖体固着、萌发、藻体生长和繁殖不同阶段的影响,主要结论如下:固着阶段,盐度5不利于浒苔微观繁殖体的固着,盐度10～35对微观繁殖体固着的影响不显著,相同盐度下,孢子的固着量显著高于配子。萌发阶段,不同盐度(5～35)及不同盐度变化形式对微观繁殖体(孢子和配子)的萌发没有显著影响,孢子的萌发速度快于配子,最终均能完全萌发。生长阶段,低盐(5～15)不利于浒苔幼苗的生长。繁殖阶段,当盐度≤10时,浒苔不进行生殖活动;盐度15～35范围内,浒苔可以产生微观繁殖体,完成一个完整的生活史;在绿潮形成过程中,孢子的生殖策略为K对策,配子的生殖策略为R对策。上述结论表明,在苏北浅滩和青岛海域,盐度不是限制浒苔发生发展及繁殖过程的关键环境因子,明确了盐度在绿潮发生...  相似文献