IBM was among the first corporations to provide group life insurance (1934), survivor benefits (1935) and paid vacations (1937). In 1932 IBM created an Education Department to oversee training for employees, which oversaw the completion of the IBM Schoolhouse at Endicott in 1933. In 1935, the employee magazine Think was created. Also that year, IBM held its first training class for female systems service professionals. In 1942, IBM launched a program to train and employ disabled people in Topeka, Kansas. The next year classes began in New York City, and soon the company was asked to join the President's Committee for Employment of the Handicapped. In 1946, the company hired its first black salesman, 18 years before the Civil Rights Act of 1964. In 1947, IBM announced a Total and Permanent Disability Income Plan for employees. A vested rights pension was added to the IBM retirement plan. During IBM's management transformation in the 1990s revisions were made to these pension plans to reduce IBM's pension liabilities.
IBM employees created a magazine in 1935, what was its name?
Think

Hydrogen poses a number of hazards to human safety, from potential detonations and fires when mixed with air to being an asphyxiant in its pure, oxygen-free form. In addition, liquid hydrogen is a cryogen and presents dangers (such as frostbite) associated with very cold liquids. Hydrogen dissolves in many metals, and, in addition to leaking out, may have adverse effects on them, such as hydrogen embrittlement, leading to cracks and explosions. Hydrogen gas leaking into external air may spontaneously ignite. Moreover, hydrogen fire, while being extremely hot, is almost invisible, and thus can lead to accidental burns.
What can hydrogen embrittlement lead to?
cracks and explosions

Other sections of society included the nobility, clergy, and townsmen. Nobles, both the titled nobility and simple knights, exploited the manors and the peasants, although they did not own lands outright but were granted rights to the income from a manor or other lands by an overlord through the system of feudalism. During the 11th and 12th centuries, these lands, or fiefs, came to be considered hereditary, and in most areas they were no longer divisible between all the heirs as had been the case in the early medieval period. Instead, most fiefs and lands went to the eldest son.[R] The dominance of the nobility was built upon its control of the land, its military service as heavy cavalry, control of castles, and various immunities from taxes or other impositions.[S] Castles, initially in wood but later in stone, began to be constructed in the 9th and 10th centuries in response to the disorder of the time, and provided protection from invaders as well as allowing lords defence from rivals. Control of castles allowed the nobles to defy kings or other overlords. Nobles were stratified; kings and the highest-ranking nobility controlled large numbers of commoners and large tracts of land, as well as other nobles. Beneath them, lesser nobles had authority over smaller areas of land and fewer people. Knights were the lowest level of nobility; they controlled but did not own land, and had to serve other nobles.[T]
In what centuries did fiefs become hereditary?
11th and 12th