Touch-sensitive surfaces

Jumping ahead to the present day, typewriters are mostly to be found in museums. Instead we rely on computers or tablets of various types. On a computer with a keyboard, it is still possible to imagine some kind of neat mechanical process. But on tablets where the input, in this case the letter t, is either spoken or drawn on a touch sensitive surface, the one-to-one correspondence has disappeared. Indeed, the outcome may be a t, a d, or any other letter that bears some resemblance (as a homonym or an isomorph of the letter t ). 

Children expecting a touch-sensitive surface. Some children assumed that they could interact with the iGameFloor using their feet as point and click/drag and drop. iGameFloor has some similarities with well-known interfaces from the familiar PC,... 

A typical sample would have a surface area of the order 10 x 20 mm. The preparation of the surface for examination is the subject of an ASTM standard (ASTM E1078-97), and the objective is to ensure that the surface to be analysed has not been contaminated or altered prior to analysis. The techniques of surface analysis are sensitive to surface layers only a few atoms thick, so the degree of cleanliness required will be much greater than for other forms of analysis. Nothing must be allowed to touch the surface to be analysed. 

It is impossible to complete a discussion of the measurement of surface tension without saying something about the need for extreme cleanliness in any determination of 7. Any precision chemical measurement requires attention to this consideration, but surfaces are exceptionally sensitive to impurities. It is often noted that touching the surface of 100 cm2 of water with a fingertip deposits enough contamination on the water to introduce a 10% error in the value of 7. Not only must all pieces of equipment be clean, but also the experiments must be performed within enclosures or in very clean environments to prevent outside contamination. In addition, both surface tension and contact angle should be measured under constant temperature conditions. 

The usual input device is a keyboard which may contain 90 or more keys. For the novice computer user, simply finding the correct key can be a daunting task, so alternative input devices have been developed. These include touch-sensitive screens, tracker balls, light pens and so on. Perhaps the most common alternative to the keyboard is the mouse. This is simply a small box with one or more buttons on the top and a tracker ball on its underside. The mouse is connected to the computer via a single cable. As the mouse is moved over a flat surface, sensors detect the movement of the ball and the computer can calculate the position of the mouse. An arrow or similar symbol is usually displayed on the screen and this symbol moves in synchrony with the mouse. The mouse can be used to move the symbol to indicate choices on the screen and these can then be selected by pressing one of the buttons on the mouse. While experienced computer-users sometimes complain that mouse-based... 

Once pressed, the resultant pellet is placed carefully into a holder, which in turn may be placed in the instrument. Care must be taken not to touch the surface of the freshly pressed pellet. Be aware that the fresh pellet surfaces are very sensitive to moisture. 

At one end of the scale are those individuals who lack all sensitivity to the usual pain stimulibums, cuts, bruises, etc. Such a person was a boy at Johns Hopkins who could have pins thrust into him his skin could be pinched until it became bloodshot his Achilles tendon could be squeezed with full force without any indication of discomfort. He did have a normal sense of touch and was sensible to cold and heat throughout his body surface, but nowhere was there a response to pain. 

Bowden Yoffe have suggested (Ref 12, pp 127-128 Ref 14) that the abnormal sensitivity of NI3 or NI3 NH3 is due to its being inherently unstable, and that the very slight external stimuli (slight touch, warm air, irradiation etc) primarily act to remove adsorbed NH3 from the iodide surface. Apparently this adsorbed NH3 stabilizes the iodide and its removal causes the iodide to decompose spontaneously... 

Drop Test. See Impact Sensitivity Test Effect of Pressure on Performance in Detonators. See Pressure Effect, etc Explosion(or Ignition) Temperature. When O.02g charges of pentryi were dropped on molten Wood s metal preheated to various temps, no expin or ignition took place at 233°(5 trials), but at 235° the sample ignited in 3 secs after it touched the hot surface. The same time interval was observed at 240°, while at 250° it was 2 secs, at 260° 1.5 to 2 secs and at 270—280° 1.5 secs (Ref 4,p 1389)... 

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