Electrocardiography

Electrocardiography (ECG or EKG from German: Elektrokardiogramm) is a transthoracic (across the thorax or chest) interpretation of the electrical activity of the heart over a period of time, as detected by electrodes attached to the surface of the skin and recorded by a device external to the body. The recording produced by this noninvasive procedure is termed an electrocardiogram (also ECG or EKG).
An ECG is used to measure the rate and regularity of heartbeats, as well as the size and position of the chambers, the presence of any damage to the heart, and the effects of drugs or devices used to regulate the heart, such as a pacemaker.
Most ECGs are performed for diagnostic or research purposes on human hearts, but may also be performed on animals, usually for diagnosis of heart abnormalities or research.

^{A 3 channel china ECG machine}

An ECG is the best way to measure and diagnose abnormal rhythms of the heart, particularly abnormal rhythms caused by damage to the conductive tissue that carries electrical signals, or abnormal rhythms caused by electrolyte imbalances. In a myocardial infarction (MI), the ECG can identify if the heart muscle has been damaged in specific areas, though not all areas of the heart are covered. The ECG cannot reliably measure the pumping ability of the heart, for which ultrasound-based (echocardiography) or nuclear medicine tests are used. It is possible for a human or other animal to be in cardiac arrest, but still have a normal ECG signal (a condition known as pulseless electrical activity).
The ECG device detects and amplifies the tiny electrical changes on the skin that are caused when the heart muscle depolarizes during each heartbeat. At rest, each heart muscle cell has a negative charge, called the membrane potential, across its cell membrane. Decreasing this negative charge towards zero, via the influx of the positive cations, Na⁺ and Ca⁺⁺, is called depolarization, which activates the mechanisms in the cell that cause it to contract. During each heartbeat, a healthy heart will have an orderly progression of a wave of depolarisation that is triggered by the cells in the sinoatrial node, spreads out through the atrium, passes through the atrioventricular node and then spreads all over the ventricles. This is detected as tiny rises and falls in the voltage between two electrodes placed either side of the heart which is displayed as a wavy line either on a screen or on paper. This display indicates the overall rhythm of the heart and weaknesses in different parts of the heart muscle.
Usually, more than two electrodes are used, and they can be combined into a number of pairs (For example: left arm (LA), right arm (RA) and left leg (LL) electrodes form the three pairs LA+RA, LA+LL, and RA+LL). The output from each pair is known as a lead. Each lead looks at the heart from a different angle. Different types of ECGs can be referred to by the number of leads that are recorded, for example 3-lead, 5-lead or 12-lead ECGs (sometimes simply "a 12-lead"). A 12-lead ECG is one in which 12 different electrical signals are recorded at approximately the same time and will often be used as a one-off recording of an ECG, traditionally printed out as a paper copy. Three- and 5-lead ECGs tend to be monitored continuously and viewed only on the screen of an appropriate monitoring device, for example during an operation or whilst being transported in an ambulance. There may or may not be any permanent record of a 3- or 5-lead ECG, depending on the equipment used.

^{ECG graph paper}

The output of an ECG recorder is a graph (or sometimes several graphs, representing each of the leads) with time represented on the x-axis and voltage represented on the y-axis. A dedicated ECG machine would usually print onto graph paper which has a background pattern of 1mm squares (often in red or green), with bold divisions every 5 mm in both vertical and horizontal directions.

Example of modern PC-based ECG: Data are stored in digital format and can be emailed.

It is possible to change the output of most ECG devices but it is standard to represent each mV on the y axis as 1 cm and each second as 25 mm on the x-axis (that is a paper speed of 25 mm/s). Faster paper speeds can be used, for example, to resolve finer detail in the ECG. At a paper speed of 25 mm/s, one small block of ECG paper translates into 40 ms. Five small blocks make up one large block, which translates into 200 ms. Hence, there are five large blocks per second. A calibration signal may be included with a record. A standard signal of 1 mV must move the stylus vertically 1 cm, that is, two large squares on ECG paper.

Snickometre

A Snickometer, commonly known as Snicko, is used in televising cricket to graphically analyse sound and video, and show whether a fine noise, or snick, occurs as ball passes bat. It was invented by English computer scientist Allan Plaskett in the mid-1990s.

 The Snickometer is often used in a slow motion television replay by the third umpire to determine if the cricket ball touched the cricket bat on the way through to the wicketkeeper. The commentators will listen and view the shape of the recorded soundwave. If there is a sound of leather on willow, which is usually a short sharp sound in synchrony with the ball passing the bat, then the ball has touched the bat. Other sounds such as the ball hitting the batsman's pads, or the bat hitting the pitch, and so on, tend to have a fatter shape on the sound waveform.
If, in the umpire's opinion, this is the case, and the ball was a legal delivery that was caught before touching the ground, then the batsman is given out by the umpire. The umpire does not have the benefit of the Snickometer, and must instead rely on his senses of sight and hearing, as well as his judgement. When the Umpire DRS (Decision Review System) was introduced to Test Cricket, Snicko was not considered accurate enough, and so another edge detecting tool Hot Spot was used.
Channel 4 in the UK and Channel Nine of Australia, amongst others, have used it to help determine if the batsman was out or not.

Gorilla glass

Gorilla Glass...

Gorilla Glass is the trademark for an alkali-aluminosilicate sheet glass manufactured by U.S. glassmaker Corning. Engineered for a combination of thinness, lightness, and damage-resistance, it is used primarily as the cover glass for portable electronic devices including mobile phones, portable media players, laptop computer displays, and some television screens.

The manufacturer says the material's primary properties are its strength (allowing thin glass without fragility), its high scratch resistance (for protective coating), and its hardness (with a Vickers hardness test rating of 622 to 701) — and that the material can be recycled.

Gorilla Glass by 2010 had been used in approximately 20 percent of mobile handsets worldwide, about 200 million units. The second generation, called "Gorilla Glass 2", was introduced in 2012. On October 24, 2012, Corning announced that over one billion mobile devices used Gorilla Glass.

Telephone

A telephone, or phone, is a telecommunications device that converts sound into electronic signals suitable for transmission via cables or other transmission media over long distances. First patented in 1876 by Alexander Graham Bell and further developed by many others, the telephone was the first device in human history that enabled people to talk directly with each other across large distances. It rapidly became indispensable to businesses, government, and households, and it is now among the most widely used appliances in the developed world. The word telephone has been adapted into the vocabulary of many languages. It is derived from the Greek: τῆλε, tēle, far and φωνή, phōnē, voice, together meaning distant voice.