что такое круговорот веществ и что такое биогеохимический цикл

индукция магнитного поля прямого тока?

упростите выражни: (а-9)^2-(81+2a)

The Working Conditions of Government Employees.

Every working person is concerned about opportunities for promotion, and civil service workers are no exception. They have the opportunity for promotion within each salary grade, their advancement depending upon whether their work is done at an acceptable level of competence. Furthermore, employees who show ability and efficiency can be promoted to a job in a higher grade. After a trial period of one year, most civil service workers have career jobs with a good measure of security. No government employee can be forced to join a labor union; nor can he be prevented from doing so. The choice is up to him. The membership of civil service employees in labor unions was long a matter of dispute. In 1889, however, postal workers took the first step and formed the National Association of Letter Carriers. At first, the activities of thi^ organization were sharply restricted. Then, in 1912, the Congress authorized the establishment of unions for federal employees, with the provision that no union would be permitted to strike against the government.

Упражнение 2. Выпишите из текста английские эквиваленты следующих слов и словосочетаний: условия труда, беспокоиться, возможность продвижения, государственные служащие, исключение, зависеть от, приемлемый уровень, способности и возможности, высший уровень (высшая ступень), испытательный срок, заставлять, членство, профсоюз, предмет спора, ограничивать, разрешать, забастовка против правительства

1)как называется раздел химии в котором изучают тепловые эффекты?