[Emigration of social medicine experts of the Berlin Charité to the USA - careers of the students of Alfred Grotjahn].

Background: In 1920, the physician Alfred Grotjahn was appointed as first Chair for Social Hygiene in Germany at the University of Berlin. During reign of national socialism, the Institute for Social Hygiene was closed and from 1933 and 1945 transformed into an Institute for Racial Hygiene. During that period, many German scientists including social medicine co-workers of the Berlin Charité emigrated due to political, religious or racial prosecution.

New technique for ultrasound imaging.

A new system of ultrasonic imaging has been developed which utilizes optical interferometry. This system has a broad frequency range, wide angular response, and good resolution. Operation of the system and the results of experimental imaging are described.

Differences in the attenuation of ultrasound by normal, benign, and malignant breast tissue.

In quantitative measurements of the attenuation of ultrasound in 18 samples of variously normal, benign, and malignant breast tissue, we found significantly different ranges of attenuation. As observed in previous in vivo studies, with the exception of medullary carcinoma, malignant tissue produces the most attentuation of ultrasound in the frequency range of 1.5 to 3.

Ultrasonic waves: their interferometric measurement and display.

A system for the measurement and visualization of small displacements has been developed that features high sensitivity and acoustic-wavelength-limited resolution over apertures as large as 15 cm at frequencies up to 10 MH(z). Acoustic-wave displacement amplitudes as small as 0.07 A are measured by interferometrically detecting the motion of a thin, acoustically transparent, metallized pellicle as the ultrasonic wave passes through it.