SRI International

About: SRI International is a nonprofit organization based out in Menlo Park, California, United States. It is known for research contribution in the topics: Ionosphere & Incoherent scatter. The organization has 7222 authors who have published 13102 publications receiving 660724 citations. The organization is also known as: Stanford Research Institute & SRI.

Frozen-solution MALDI mass spectrometry studies of DNA

Abstract: Matrix-assisted laser desorption/ionization (MALDI) in conjunction with time-of-flight mass spectrometry is an effective technique for analysis of DNA oligomers. However, with increasing oligomer length, mass resolution and sensitivity degrade as the effects of prompt and metastable decay, adduct formation, and ion kinetic energy spreads become increasingly dominant. Attempts to reduce these factors have focused on the use of volatile liquids as matrices because these molecules have lower binding energies both to themselves and to the DNA and theoretically require less energy for desorption. We have investigated thin films of DNA in liquid matrices frozen on a liquid nitrogen-cooled sample stage. Several solvent systems have resulted in reproducible mass spectra of single-stranded DNA oligomers.

Photon-echo novelty filter for measuring a sudden change in index of refraction

Abstract: An optical novelty filter with phase-conjugate photon echoes is constructed to measure a sudden change in the index of refraction of a transparent medium. This novelty filter is set up as a Michelson interferometer and employs a europium-doped crystal as a phase-conjugate mirror. The filter is sensitive to the sudden change in index of refraction when the phase-conjugate echo experiences a different path length from the first laser excitation pulse in a photon-echo experiment. Using a Pockels cell as a pure phase modulator, we demonstrate that the filter can resolve a sudden phase change occurring on a nanosecond time scale with an accuracy and resolution close to 5°.