The Siege of Baghdad was a siege that took place in Baghdad in 1258 and lasted 13 days from January 29, 1258 to February 10, 1258.
The siege, carried out by Mongolian Ilkhanate forces and allied troops, involved the investment, capture and sack of Baghdad, then the capital of the Abbasid Caliphate.
Mach number is a measure of the speed of an airplane. When we say an aircraft is flying at Mach 1, it means that the speed of the vehicle is 343 m/s. Mach number is the ratio between the true airspeed of the aircraft and the local speed of sound.
Fluorescent lamps consist of glass tubes filled with a mixture of argon and mercury vapor. The metal electrodes on both ends are coated with an alkaline earth oxide that easily donates electrons.
There are two ways to freeze and store sperm: dry ice and alcohol (100 degrees Fahrenheit) and liquid nitrogen (320 degrees Fahrenheit). Liquid nitrogen is preferred because there is no evidence that fertility declines with age. Sperm stored in dry ice alcohol will gradually reduce their chances of giving birth.
The functional or behavioral response of an organism to changes in the duration of a daily, seasonal, or annual cycle of photoperiodism, light, and darkness. Photoperiodic responses are reasonably predictable, but temperature, diet, and other environmental factors also alter the organism's response.
