Scalp sensitivity has several origins. It could be caused by an imbalance in the sebum secretion process, which leads to irritation. Pollution and stress can also irritate the scalp. In fact, pollution coats the hair in harmful elements that create a dull film over the hair and, like stress, generate free radicals.
Hard drive sizes. Hard drives come in two basic physical sizes: 2.5-inch and 3.5-inch. These sizes refer to the size of the data platters, not the size of the hard drive mechanism. Traditionally, 2.5-inch drives are used for laptops while 3.5-inch drives are used for desktop computers. Some compact desktops also use the smaller drives to enable a smaller form factor for the computer.
The capacity of hard drives has grown exponentially over time. When hard drives became available for personal computers, they offered 5-megabyte capacity. During the mid-1990s the typical hard disk drive for a PC had a capacity of about 1 gigabyte. As of December 2014, desktop hard disk drives typically had a capacity of 500 to 4000 gigabytes, while the largest-capacity drives were 8 terabytes.