(a) Echo times are measured by diagnostic ultrasound scanners to determine distances to re?ecting surfaces in a patient. What is the difference in echo times for tissues that are 3.50 and 3.60 cm beneath the surface? (This difference is the minimum resolving time for the scanner to see details as small as 0.100 cm, or 1.00 mm. Discrimination of smaller time differences is needed to see smaller details.) (b) Discuss whether the period T at this ultrasound must be smaller than the minimum time resolution. If so, what is the minimum frequency of the ultrasound and is that out of the normal range for diagnostic ultrasound?
(a) Echo times are measured by diagnostic ultrasound scanners to determine distances to re?ecting surfaces in a patient. What is the difference in echo times for tissues that are 3.50 and 3.60 cm beneath the surface? (This difference is the minimum resolving time for the scanner to see details as small as 0.100 cm, or 1.00 mm. Discrimination of smaller time differences is needed to see smaller details.) (b) Discuss whether the period T at this ultrasound must be smaller than the minimum time resolution. If so, what is the minimum frequency of the ultrasound and is that out of the normal range for diagnostic ultrasound?
(a) Echo times are measured by diagnostic ultrasound scanners to determine distances to re?ecting surfaces in a patient. What is the difference in echo times for tissues that are 3.50 and 3.60 cm beneath the surface? (This difference is the minimum resolving time for the scanner to see details as small as 0.100 cm, or 1.00 mm. Discrimination of smaller time differences is needed to see smaller details.) (b) Discuss whether the period T at this ultrasound must be smaller than the minimum time resolution. If so, what is the minimum frequency of the ultrasound and is that out of the normal range for diagnostic ultrasound?
Helicobacter pylori (H. pylori) is a helically-shaped bacterium that is usually found in the stomach. It burrows through the gastric mucous
lining to establish an infection in the stomach's epithelial cells (see photo). Approximately 90% of the people infected with H. pylori will
never experience symptoms. Others may develop peptic ulcers and show symptoms of chronic gastritis. The method of motility of H.
pylori is a prokaryotic flagellum attached to the back of the bacterium that rigidly rotates like a propeller on a ship. The flagellum is
composed of proteins and is approximately 40.0 nm in diameter and can reach rotation speeds as high as 1.50 x 103 rpm. If the speed
of the bacterium is 10.0 μm/s, how far has it moved in the time it takes the flagellum to rotate through an angular displacement of 5.00
* 10² rad?
Zina Deretsky, National Science
Foundation/Flickr
H. PYLORI CROSSING MUCUS LAYER OF STOMACH
H.pylori Gastric Epithelial
mucin cells
gel
Number
i
318
Units
um
H.pylori…
T1. Calculate what is the received frequency when the car drives away from the radar antenna at a speed v of a) 1 m/s ( = 3.6 km/h), b) 10 m/s ( = 36 km/h), c) 30 m /s ( = 108 km/h) . The radar transmission frequency f is 24.125 GHz = 24.125*10^9 Hz, about 24 GHz. Speed of light 2.998 *10^8 m/s.
Campbell Essential Biology with Physiology (5th Edition)
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