Aquarium guide
Aquarium guide     

  
 
INTRODUCTION
 

INTRODUCTION

There was a time when the keeping and study of exotic fish was the preserve of serious researchers closeted in their laboratories; today, it is an established and popular hobby. Dealerships and specialized sales areas in large stores are springing up everywhere, paralleling an explosion in the number of public aquariums and books or magazines devoted to the subject. More and more people of all ages are falling under the spell, enjoying permanent access to a part of the natural world that was formerly beyond their reach. There are almost as many kinds of hobbyists as there are types of fish: the semiprofessional, the "small" and the "modest" collector, the specialist. There are the fanatics, who spend every minute of their time and energy on their aquariums, while for others fishkeeping is just a passing fad. Enthusiasts include the young - and the not so young; those with scientific knowledge or mere novices; those actively working and the retired. Such an immensely varied following guarantees that the world of the aquarist is full of interest and color.


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НИОБИЙ (лат . Niobium), Nb, химический элемент V группы периодической системы, атомный номер 41, атомная масса 92,9064. Назван от имени Ниобы - дочери мифологического Тантала (близость свойств Nb и Ta). Светло-серый тугоплавкий металл, плотность 8,57 г/см3, tпл 2477 °С, температура перехода в сверхпроводящее состояние 9,28 К. Химически очень стоек. Минералы: пирохлор, колумбит, лопарит и др. Компонент химически стойких и жаростойких сталей, из которых изготовляют детали ракет, реактивных двигателей, химическую и нефтеперегонную аппаратуру. Ниобием и его сплавами покрывают тепловыделяющие элементы (ТВЭЛы) ядерных реакторов. Станнид Nb3Sn, германид Nb3Ge, сплавы Ниобия с Sn, Ti и Zr используют