A refrigerator

A refrigerator (often called a "fridge" for short) is a cooling appliance for the storage and preservation of perishable food; food kept in a refrigerator lasts longer than that left at room temperature as the cold inhibits bacterial growth. A refrigerator maintains a cold temperature above the freezing point of water; commonly refrigerators are used in conjunction with freezers, which maintain temperatures below freezing, or a refrigerator may have an integrated freezer compartment. The refrigerator is a relatively modern invention amongst kitchen appliances. It replaced the common icebox which had been a household item for almost a century and a half prior, and is sometimes still called by the name "icebox".

Commercial units, which go by many other names, were in use for almost 40 years prior to the common home models. The fact that they operated with toxic ammonia gas systems made them unsafe for home use. Practical household refrigerators were introduced in the 1920s and gained wider acceptance in the 1930s as prices fell and non-toxic, nonflammable synthetic refrigerants, such as Freon or R-12 refrigerants were introduced.

A joke

A joke is a short story or series of words spoken or communicated, ideally with the intent of being laughed at or found humorous by the listener or reader. A practical joke differs in that the humor is not verbal, but mainly physical (e.g. throwing a custard pie in the direction of somebody's face). Some jokes are not funny.

Jokes are performed either in a staged situation, such as a comedy in front of an audience, or informally for the entertainment of participants and onlookers. The desired response is generally laughter, although loud groans are also a common response to some forms of jokes, such as puns and shaggy dog stories.

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Alcohol

In chemistry, an alcohol (Arabic: al kohol) is any organic compound in which a hydroxyl group (-OH) is bound to a carbon atom of an alkyl or substituted alkyl group. The general formula for a simple acyclic alcohol is C_nH_2n+1OH.

In general usage, the word alcohol, when used alone, usually refers to ethanol, also known as grain alcohol or (older) spirits of wine. Ethanol is a strongly-smelling, colorless, volatile liquid formed by the fermentation of sugars. It also often refers to any beverage that contains ethanol (see alcoholic beverage). This sense underlies the term alcoholism (addiction to alcohol).

Other forms of alcohol are usually described with a clarifying adjective, as in isopropyl alcohol (isopropanol) or wood alcohol ('methyl alcohol, or methanol). The suffix -ol, appears in the official chemical name of all alcohols.

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A Post-it note

A Post-it note (or simply Post-it), invented and manufactured by 3M, is a piece of stationery with a readherable strip of adhesive on the back, designed for temporarily attaching notes to documents, computer displays, and so forth. While now available in a wide range of colors, shapes, and sizes, the most common size of Post-it note is a 3-in (7.5-cm) square, trademark canary yellow in color. The notes use a unique low-tack adhesive that enables the Post-its to be easily attached and removed without leaving marks or residue. The names Post-it and Post-it note—as well as the canary yellow color—are trademarks of 3M, the company which invented and manufactures them. Accepted generic terms for competitors include sticky notes or repositionable or repositional notes; nonetheless, Post-it note is frequently used as a generic term for any such product. 3M manufactures other products towards the Post-it note concept, leveraging the success of the brand. As Post-it have been driven towards computerized versions like Stickies or PtiMemo, 3M markets its own software under the name of 'Post-it software note'. Wikipedia

A paper clip

A paper clip (spelled both as two separate words and as one compound word) is a device which holds several sheets of paper together by means of pressure: it leaves the paper intact and can be easily removed. Wikipedia

A hard disk

A hard disk (commonly known as a hard disk drive or hard drive and formerly known as a fixed disk) is a digitally encoded non-volatile storage device which stores data on rapidly rotating platters with magnetic surfaces. Strictly speaking, "drive" refers to an entire unit containing multiple platters, a read/write head assembly, driver electronics, and motor while "hard disk" (sometimes "platter") refers to the storage medium itself.^[1]

Hard disks were originally developed for use with computers. In the 21st century, applications for hard disks have expanded beyond computers to include digital video recorders, digital audio players, personal digital assistants, and digital cameras. In 2005 the first mobile phones to include hard disks were introduced by Samsung Group and Nokia. The need for large-scale, reliable storage, independent of a particular device, led to the introduction of configurations such as RAID, hardware such as network attached storage (NAS) devices, and systems such as storage area networks (SANs) for efficient access to large volumes of data.

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Sunscreen

Sunscreen (also known as sunblock, suntan lotion) is a lotion, spray or other topical product that helps protect the skin from the sun's ultraviolet (UV) radiation, and which reduces sunburn and other skin damage, ultimately leading to a lower risk of skin cancer. However, suntan lotion is an incorrect term for sunscreen as it is something entirely different. Suntan lotion is used to attract UV rays in order to better tan where sunblock is used to deflect UV radiation. These are commonly called indoor tanning lotions when designed for use with tanning beds or just suntan lotion if designed for outdoor use and may or may not have SPF protection in them.

The best sunscreens protect against both UVB (ultraviolet radiation with wavelength between 290 and 320 nanometres), which can cause sunburn, and UVA (between 320 and 400 nanometres), which damages the skin with more long-term effects, such as premature skin aging. Most sunscreens work by containing either an organic chemical compound that absorbs ultraviolet light (such as oxybenzone) or an opaque material that reflects light (such as titanium dioxide, zinc oxide), or a combination of both. Typically, absorptive materials are referred to as chemical blocks, whereas opaque materials are mineral or physical blocks.

Dosing for sunscreen can be calculated using the formula for body surface area and subsequently subtracting the area covered by clothing that provides effective UV protection. The dose used in FDA sunscreen testing is 2 mg/cm². From a sample calculation in a FDA monograph, if one assumes an "average" adult build of height 5 ft 4 in (163 cm) and weight 150 lb (68 kg) with a 32 in (82 cm) waist, that adult wearing a bathing suit covering the groin area should apply 29 g (approximately 1 oz) evenly to the uncovered body area.

Contrary to the common advice that sunscreen should be reapplied every 2–3 hours, research has shown that the best protection is achieved by application 15–30 minutes before exposure, followed by one reapplication 15–30 minutes after the sun exposure begins. Further reapplication is only necessary after activities such as swimming, sweating, and rubbing.^[1]

However, more recent research at the University of California indicates that sunscreen needs to be reapplied within 2 hours in order to remain effective. Not reapplying could even cause more cell damage than not using sunscreen at all, due to the release of extra free radicals from the absorbed chemical.^[2]

A significant reduction in sun exposure inhibits the production of vitamin D. However, excessive sun exposure has been conclusively linked to some forms of skin cancer and signs of premature aging. Season, geographic latitude, time of day, cloud cover, smog, skin type, and sunscreen all have an effect on vitamin D production in the skin, but fifteen minutes per day of direct exposure to the sun is a generally accepted guideline to follow for optimum vitamin D production. Experts generally recommend taking a fifteen minute walk in the morning or evening without wearing sunscreen to meet this requirement.

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