New Developments in Fourier Transform Infrared Vibrational Circular Dichroism Measurements

A new FT-IR vibrational circular dichroism (VCD) spectrometer has been assembled to record VCD spectra with excellent signal quality up to ∼650 cm−1. A special detector with 600 cm−1 cutoff ( D* = 4 × 1010), a ZnSe modulator, and a KRS-5 polarizer were used in these measurements. Typical VCD spectra at 4 cm−1 resolution can be obtained within a one-hour data acquisition period, while those at 1 cm−1 resolution, in the ∼ 1500-650 cm−1 region, can be obtained within four hours of data acquisition per sample. VCD spectra for ã-pinene, 3-bromocamphor, and propylene oxide are presented.

Integral Pulse Frequency Modulated Ultrasound for the Detection and Quantification of Gas Microbubbles in Flowing Blood

An integral pulse frequency modulated gas microbubble detector is described. When used in conjunction with an electromagnetic blood flowmeter, the ultrasound pulse repetition frequency can be regulated to reduce multiple counting errors due to variations in blood flow rate. A special detector mounting head eliminates problems due to wall curvature and pulsation, permits reliable and reproducible transducer coupling and makes it possible to gate the ultrasound field electronically in order to avoid spurious counts due to crystal and wall artefacts and low intensity regions. Results obtained from the detector during an in vitro evaluation of bubble oxygenators suggest that the number of arterial line gas microbubbles is less than has been claimed previously and that the total volume of gas liberated in the form of microbubbles may be too small to have any demonstrable primary clinical effects.

Imaging and diffraction modes in Scanning Transmission Electron Microscopy

Some of the most important applications of STEM depend on the variety of imaging and diffraction made possible by the versatility of the detector system and the serial nature, of the image acquisition. A special detector system, previously described, has been added to our STEM instrument to allow us to take full advantage of this versatility. In this, the diffraction pattern in the detector plane may be formed on either of two phosphor screens, one with P47 (very fast) phosphor and the other with P20 (high efficiency) phosphor. The light from the phosphor is conveyed through a fiber-optic rod to an image intensifier and TV system and may be photographed, recorded on videotape, or stored digitally on a frame store. The P47 screen has a hole through it to allow electrons to enter a Gatan EELS spectrometer. Recently a modified SEM detector has been added so that high resolution (10Å) imaging with secondary electrons may be used in conjunction with other modes.