UVC

“UVC is really nasty stuff – you shouldn't be exposed to it,” says Arnold. “It can take hours to get sunburn from UVB, but with UVC it takes seconds. If your eyes are exposed… you know that gritty feeling you get if you look at the sun? It’s like that times 10, just after a few seconds.”


Sunlight contains three types of UV. First there is UVA, which makes up the vast majority of the ultraviolet radiation reaching the Earth’s surface. It’s capable of penetrating deep into the skin and is thought to be responsible for up to 80% of skin ageing, from wrinkles to age spots.

Next there’s UVB, which can damage the DNA in our skin, leading to sunburn and eventually skin cancer (recently scientists have discovered that UVA can also do this). Both are reasonably well known, and can be blocked out by most good sun creams.

Both UVA and UVB damage the skin — but nothing is as damaging as UVC (Credit: Getty Images)

There is also a third type: UVC. This relatively obscure part of the spectrum consists of a shorter, more energetic wavelength of light. It is particularly good at destroying genetic material – whether in humans or viral particles. Luckily, most of us are unlikely to have ever encountered any. That’s because it’s filtered out by ozone in the atmosphere long before it reaches our fragile skin.

Or that was the case, at least, until scientists discovered that they could harness UVC to kill microorganisms. Since the finding in 1878, artificially produced UVC has become a staple method of sterilisation – one used in hospitals, airplanes, offices, and factories every day. Crucially, it’s also fundamental to the process of sanitising drinking water; some parasites are resistant to chemical disinfectants such as chlorine, so it provides a failsafe.


Semordnilap

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Semordnilap (palindromes spelled backward) is a name coined for words that spell a different word in reverse. The word was coined by Martin Gardner in his notes to C.C. Bombaugh's book Oddities and Curiosities of Words and Literature in 1961.

An example of this is the word stressed, which is desserts spelled backward.

Some semordnilaps are deliberate creations. An example in electronics (although rarely used now) is the mho, a unit of electrical conductance, which is ohm spelled backwards, the unit of electrical resistance and the reciprocal of conductance. Similarly, the daraf, a unit of elastance, is farad spelled backwards, the unit of capacitance and the reciprocal of elastance. In fiction, many characters have names deliberately made to be semordnilaps of other names or words, such as Alucard (a semordnilap of "Dracula").

Semordnilaps are also known as emordnilaps, word reversals, reversible anagrams, heteropalindromes, semi-palindromes, half-palindromes, reversgrams, mynoretehs, volvograms, or anadromes. They have also sometimes been called antigrams, though this term usually refers to anagrams which have opposite meanings. As of October 2018, none of these terms have been accepted as official entries in the Oxford English Dictionary.

VPN

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virtual private network (VPN) extends a private network across a public network and enables users to send and receive data across shared or public networks as if their computing devices were directly connected to the private network. Applications running on an end system (PC, smartphone etc.) across a VPN may therefore benefit from the functionality, security, and management of the private network. Encryption is a common, though not an inherent, part of a VPN connection.

VPNs can be characterized as host-to-network or remote access by connecting a single computer to a network or as site-to-site for connecting two networks.

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menu bar

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What’s in the menu bar on Mac?

The menu bar runs along the top of the screen on your Mac. Use the menus and icons in the menu bar to choose commands, perform tasks, and check status.

You can set an option in General preferences to automatically hide the menu bar; then it’s shown only when you move the pointer to the top of the screen.

Apple menu

The Apple menu , located in the top-left corner of the screen, contains commands for things you do frequently, such as update apps, open System Preferences, lock your screen, or shut down your Mac. See What’s in the Apple menu?

App menus

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App menus are located next to the Apple menu. The name of the app you’re using appears in bold, followed by other menus, often with standard names such as File, Edit, Format, or Window. Each app has a Help menu to make it easy to get information about using an app. See Use the built-in help.

Each menu contains commands, many of which are available in most apps. For example, the Open command is often in the File menu. For information about the symbols in the menu commands, see What are those symbols shown in menus?

Status menus

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Toward the right end of the menu bar are status menus, typically represented by icons. Use these menus to check the status of your Mac or quickly access features—for example, quickly turn Wi-Fi on or off or check your computer’s battery charge.

You can add status menus, such as the emoji viewer or a Volume control icon. You can also add status menus for some apps when you install them.

To rearrange the status menu icons, press and hold the Command key while dragging the items. To remove an icon, press and hold the Command key and drag the icon out of the menu bar.

Spotlight

Click the Spotlight icon , located after the status menus, to use Spotlight to search for items on your Mac and more.

Siri

Following Spotlight is the Siri icon —click it to ask Siri to do things like open files or apps, or to find things on your Mac or on the internet. You can easily keep Siri results handy on your desktop or in Notification Center.

Notification Center

At the right end of the menu bar, click the Notification Center icon  to use Notification Center to view details about your day and catch up on notifications you missed.

Triage

Triage

Triage (/ˈtriːɑːʒ, triˈɑːʒ/) is the process of determining the priority of patients' treatments based on the severity of their condition. This rations patient treatment efficiently when resources are insufficient for all to be treated immediately; influencing the order and priority of emergency treatment, emergency transport, or transport destination for the patient.

MBA

The MacBook Air (MBA) is a line of laptop computers developed and manufactured by Apple Inc. It consists of a full-size keyboard, a machinedaluminum case, and a thin light structure. The Air was originally positioned as a premium ultraportable positioned above the previous MacBook line.[2] Since then, the Air has become Apple's entry-level laptop due to the original MacBook's discontinuation in 2011, as well as lowered prices on subsequent iterations. In the current product line, the MacBook Air sits below the performance range MacBook Pro.