Sound is Produced by Vibrations in Matter (Air, Liquids, Solids)
Pitch is Determined by the Frequency of Vibration
A Snellen chart is an eye chart used by eye care professionals and others to measure visual acuity. Snellen charts are named after the Dutch ophthalmologist Herman Snellen who developed the chart in 1862
The traditional Snellen chart is printed with eleven lines of block letters. The first line consists of one very large letter, which may be one of several letters, for example E, H, N, or A. Subsequent rows have increasing numbers of letters that decrease in size. A patient taking the test covers one eye, and reads aloud the letters of each row, beginning at the top. The smallest row that can be read accurately indicates the patient’s visual acuity in that eye.
Despite recent controversies regarding its safety and efficacy, pulmonary artery catheterization
(PAC) remains a widely used tool for the management of patients with cardiovascular instability. In addition to providing measurements of cardiac out-put (CO), several other potentially useful pieces of data can be obtained, including estimates of preload,afterload, and oxygen utilization. However, many practitioners feel that CO is the most useful parameter obtained with PAC.The desire to measure CO without the risks of PAC has driven the search for other, less invasive measurement methods, such as esophageal Doppler measurements, lithium dilution, and carbon dioxide based techniques.
Factors Influencing Cardiac Output
A refractometer measures the extent to which light is bent (i.e. refracted) when it moves from air into a sample and is typically used to determine the index of refraction (aka refractive index or n) of a liquid sample.
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The phototherapy light shines light onto the baby’s skin. The light must be the correct wavelength (colour) and the correct intensity (brightness). It is used for treating a condition called Jaundice or Hyperbilirubinemia.
Jaundice or Hyperbilirubinemia
A hearing aid is a device used to help hard-of-hearing people hear sounds better. In the past, a funnel-like amplification cone, called an “ear trumpet” or “ear horn” was used. Also sometimes used was a desk with a built-in amplifier into which a microphone and earphones could be plugged; these worked better than passive ear trumpets but were not portable.
