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Turned A (capital: Ɐ, lowercase: ɐ, math symbol ∀) is a letter and symbol based upon the letter A.
Lowercase ɐ (in two story form) is used in the International Phonetic Alphabet to identify the near-open central vowel. This is not to be confused with the turned alpha or turned script a, ɒ, which is used in the IPA for the open back rounded vowel.
It was used in the 18th century by Edward Lhuyd and William Pryce as a phonetic character for the Cornish language. In their books, both Ɐ and ɐ have been used. It was used in the 19th century by Charles Sanders Peirce as a logical symbol for 'un-American' ("unamerican").The logical symbol ∀, has the same shape as a sans-serif capital turned A. It is used to represent universal quantification in predicate logic, where it is typically read as "for all". It was first used in this way by Gerhard Gentzen in 1935, by analogy with Giuseppe Peano's turned E notation for existential quantification and the later use of Peano's notation by Bertrand Russell. In traffic engineering it is used to represent flow, the number of units (vehicles) passing a point in a unit of time. It may also be used in unit rates.
According to the principle of acrophony, the letter A originated from the Proto-Sinatic alphabet as a symbol representing the head of an ox or cow, its orientation and original meaning having been lost over time. The turned A symbol restores the letter to a more easily recognizable logographic representation of an ox's head.U+1D44 ᵄ MODIFIER LETTER SMALL TURNED A is used in the Uralic Phonetic Alphabet.

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  1. W

    Help! Leak from under concrete floors behind bath. Stops when boiler turned on!

    I have a leak coming from under the bath and is coming through concrete floor/wall egde. When the boiler/heating is turned on it temporarily stops. The heaters are now slowly stopping to heat up. When the water mains is turned off, it stops but this is not practical as it turned off the upstairs...
  2. R

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  3. S

    Tap dribbles after being turned off.

    Hi again. I have just bought a new mixer tap and I have an issue turning it off. Every time I turn it off, I either get a dribble of water until the tap tube is empty, or it stops as it should but then any knock or movement of the tap then means that remaining water in the tap dribbles out. It...
  4. B

    3port valve problem after fitting new timer?

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  5. B

    Heat turned off but pump in the airing cupboard keeps running

    I turned the heating off at about 10. But the pump in the airing cupboard was still making a noise like it was on. There's a wall switch which allows it to be switched off in there. So it's off and quiet. But the manual switch had always been left on before and it was totally quiet unless...
  6. D

    Hot water help needed

    Hi all! Just wanting some help with a hot water problem i have. I would normally just wait and call a plumber out but its Sunday and i really cant wait till tomorrow as i have the first day of my new job tomorrow and really need hot water for shower! Anyway back to the problem. I have a...
  7. C

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  8. T

    central heating pump

    Hi. Can anybody please help. We have a old central heating system that up to now has been ok. We normally hear the pump kick in when we turn it on, but now it's not the same. We are getting a humming sound throughout the house but it appears to be coming from the pump and only stops when we...
  9. J

    CH off but rads are heating when hot water tap turned on

    My CH is off. Rads are stone cold then I turn on hot water tap and the rads start heating The water takes ages to heat through the tap yet the boiler is just the other side of the wall 40" further along This is a new boiler just installed this week Ideal Logic + 30w Also 3 rads at other end...
  10. T

    Heating turned off but radiators getting hot

    Hi Ever since I had a shower pump fitted the radiators have been getting hot even with the central heating turned off. The guy who fitted the shower pump says it is nothing to worry about but on warm days it is unpleasant. He says it is capilliary creep. That heating is creeping along the...
  11. J

    When is a turned off tap not turned off?

    My son recently moved into a new house. He got home from a weekend away to find water all over the floor of his cloakroom but could see no obvious source of the water. After making 3 holes in the wall the plumber came to the conclusion that even though the sink tap had not been left on, so no...
  12. P

    Pipes rattle / vibrate when hot water is turned on

    Hello, Since a few weeks the hot water pipes make an awful rattling noise when we turn them on. This could be any from hot water tap in the house. Especially when they are half opened. This does not happen with the cold water. The noise seems to come from the pipes underneath the shower room...
  13. B

    heating comes with water even with heating turned off

    So I have have not had any heating or hot water turned on for at lest 2 months, but yesterday I required some hot water. about half an hour after turning the hot water on, my radiators were boiling hot also. The controls indicated that the heating was turned off, and the heating control was not...
  14. C

    IDEAL ICOS HE24 - losing pressure after heating is turned off

    Hello, I am new to the forum so hello to you all and here's hoping someone can help pin point what our issue is? I have some knowledge of our system from researching the internet. We have a three storey house. On the first floor is an Ideal Icos HE24 boiler. On the third floor is a Megaflow...
  15. R

    Cold water tap won't drain after mains turned off..???

    Hi all, Just moved into a new house with a leaky tap, and want to change the washer over. Easy, right? Turned the mains off, but the cold (leaky) tap in downstairs loo won't stop running. All other taps (kitchen, bathroom etc. hold AND cold) went off. I left it running for maybe 15 minutes...
  16. L

    Aqualisa Digital shower air lock?

    Hi, I m a new member and a householder with moderate DIY experience. Our now retired plumber (hopefully not retired due to this job!) fitted a new bathroom for us last November (2015.) This included an Aqualisa quartz digital shower. Gravity fed. No remote control. A couple of months after...
  17. S

    Hudson Reed shower system help

    We just finished our master bath remodel. We installed a Hudson Reed Tec Thermostatic shower system with 12" round ceiling mount and handheld. When we first turned on the water it was ice cold and no matter which way we turned temp control knob it stayed ice cold. We left it on for a while...
  18. P

    Sink mixer taps

    I've just installed a mixer tap that the customer purchased on eBay and, as can be seen from the photo, the cold is off when the lever is in the vertical position and not when horizontal as it should be. Does anyone know if this easy to fix or is a replacement part needed?
  19. A

    when basin taps turned on upstairs, water comes out of kit mixer below. banging.

    As above title. Customer runs taps upstairs, water starts to come out of kitchen mixer, pipe under sink vibrating. What could cause this?
  20. D

    Non plumber bamboozlement - part two - developments!

    Morning! Woke up to the same problem of mains water coming out of all the mixer taps when they were turned to hot as well as when they were turned to cold. Got up and decided to do battle with the shower unit mystery. Saw that the hot/cold control on both showers was set to the hottish...
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