BIOCHEMICAL CHANGES DURING DEVELOPMENT OF EGGS AND YOLK-SAC LARVAE OF HERRING AND PLAICE

Changes in quantities of water, sodium, potassium, lipid and protein were compared in developing eggs and yolk-sac larvae of herring dupes harengus L., a species with demersal eggs, and plaice Pleuroncctcs platessa L., a species with pelagic eggs. The principal difference between the two species was the occurrence in herring, but not in plaice of considerable increases in water content and in one or both of the above ions at three distinct stages: at fertilization,during the middle stage of egg development, and in the days immediately after hatching. Newly hatched larvae of the two species differed greatly in water content because of the difference in mass and water content of the yolk, not in the water content of the rest of the body. In herring, there were increases in sodium and potassium which coincided broadly with the increase in water content. These differences are related to the gradual acquisition of buoyancy by herring during this period, comparable with the buoyancy conferred on plaice eggs a     

旅游区域研究方法

一.平均中心 1.概述平均中心可由一组特定的数据确定,也可由几组不同的数据来确定,然后进行比较。例如,确定某一景点在有代表意义的某一天每一小时的游客分布平均中心,可能揭示出这些游客行为的有价值的信息。平均中心也可以通过比较不同的旅游设施——饭店、汽车旅馆、餐厅、旅行社等——的相对位置而在图上求出。这样,通过这些综合信息,就可以更好地理解影响各类旅游业务的区位与经营状态的作用力。     

函数模型误差对随机模型设计的影响

本文以变形监测网的二类设计为背景，从精度和可靠性目标函数出发，分析了函数模型误差对随机模型设计的影响，得出了一些有益的结论。     

台风的一个简单模型

使用基础力学理论的推导方法，建立了一个简单的台风模型。该模型可预测台风的最大风速和总动能。并通过两个实列的测算与比较，说明所建立的模型有一定的预言价值。     

二氧化碳倍增对草被冠层的光合与蒸散的影响

二氧化碳倍增对草被冠层的光合与蒸散的影响Ｄ．Ｎｉｅ等（美国乔治亚大学农学系）１引言地球大气中ＣＯ２含量在迅速上升（Ｍｉｔｃｈｅｌｌ，１９８９），它对多种农林作物的影响已作了很好的研究，而对北美大陆中部温带草原区的植物研究较少，这个地区包括了美国从墨西...     

元素迁移的分维结构,级序路径及共轭地球化学异常存在的理论依据

微量元素在矿源岩中迁移遵循严格的级序路径，并且存在两种迁移倾向。迁移的结果图象是一分维结构，两种共轭地球化学异常出现的有利环境是温度高度反差地区和大断裂系及其其附近。