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 & Laser. The organization has 7222 authors who have published 13102 publications receiving 660724 citations. The organization is also known as: Stanford Research Institute & SRI.

Liquid crystalline polymer compositions, process, and products

Abstract: Novel compositions comprising a high concentration of one or more extended chain homopolymer, copolymer, or block polymer and certain polyphosphoric acids are prepared. Such compositions are optically anisotropic (liquid crystalline), capable of exhibiting excellent cohesive strength, and are especially suited to the production of high molecular weight ordered polymer fibers by dry-jet wet spinning. These liquid crystalline compositions are capable of being drawn through long air gap distances and spun at exceptionally high spin draw ratios. Fibers, films and other articles formed from these liquid crystalline compositions exhibit exceptionally high physical and heat resistant properties.

Electroactive polymer animated devices

Abstract: The present invention relates to animated devices that include one or more electroactive polymer transducers. When actuated by electrical energy, an electroactive polymer produces mechanical deflection in one or more directions. This deflection may be used to produce motion of a feature included in an animated device. Electroactive polymer transducers offer customizable shapes and deflections. Combining different ways to configure and constrain a polymer, different ways to arrange active areas on a single polymer, different animated device designs, and different polymer orientations, permits a broad range of animated devices that use an electroactive polymer transducer to produce motion. These animated devices find use in a wide range of animated device applications.

Time-of-Flight Mass Spectrometry Of Underivatized Single-Stranded DNA Oligomers by Matrix-Assisted Laser Desorption

Abstract: Matrix-assisted laser desorption with concomitant ionization (MALDI) in conjunction with time-of-flight mass spectrometry (TOF-MS) has been used to analyze underivatized random-base single-stranded DNA (ssDNA) oligomers ranging from 10 to 89 nucleotides in length by embedding them in a solid matrix of 3-hydroxypicolinic acid. At 355-nm desorption wavelength, mass spectra of positive and negative ions measured by reflecting and linear time-of-flight mass spectrometers are compared. Results from the linear system show the ionization yield is approximately equal for each polarity. Metastable ion decay is significant for the larger ssDNA oligomer ions, which results in a decrease in signal intensity and the broadening of mass peaks. In order to obtain an acceptable signal-to-noise ratio on a reflecting TOF system, a higher laser irradiance is needed, which consequently causes further degradation of mass resolution. With the apparent advantages of better sensitivity and mass resolution, it is concluded that a linear TOF system is better suited for the mass spectrometric analysis of ssDNA oligomers larger than about a 25-mer. The current system permits one-base resolution up to about a 40-mer. Mass accuracy for a 20-mer or smaller is within +/- 0.05%. Comparison of mass spectra from 5-ns and 35-ps pulse widths at the same energy density shows no significant differences. Mechanisms for oligonucleotide ion production in these experiments are discussed.

Modeling dynamic prosodic variation for speaker verification.

Abstract: Statistics of frame-level pitch have recently been used in speaker recognition systems with good results [1, 2, 3]. Although they convey useful long-term information about a speaker’s distribution of f0 values, such statistics fail to capture information about local dynamics in intonation that characterize an individual’s speaking style. In this work, we take a first step toward capturing such suprasegmental patterns for automatic speaker verification. Specifically, we model the speaker’s f0 movements by fitting a piecewise linear model to the f0 track to obtain a stylized f0 contour. Parameters of the model are then used as statistical features for speaker verification. We report results on 1998 NIST speaker verification evaluation. Prosody modeling improves the verification performance of a cepstrum-based Gaussian mixture model system (as measured by a task-specific Bayes risk) by 10%.

Analysis of measurements of Saharan dust by airborne and ground-based remote sensing methods during the Puerto Rico Dust Experiment (PRIDE)

Abstract: For 26 days in mid-June and July 2000, a research group comprised of U.S. Navy, NASA, and university scientists conducted the Puerto Rico Dust Experiment (PRIDE). In this paper we give a brief overview of mean meteorological conditions during the study. We focus on findings on African dust transported into the Caribbean utilizing Navajo aircraft and AERONET Sun photometer data. During the study midvisible aerosol optical thickness (AOT) in Puerto Rico averaged 0.25, with a maximum less than 0.5 and with clean marine periods of _0.08. Dust AOTs near the coast of Africa (Cape Verde Islands and Dakar) averaged _0.4, 30% less than previous years. By analyzing dust vertical profiles in addition to supplemental meteorology and MPLNET lidar data we found that dust transport cannot be easily categorized into any particular conceptual model. Toward the end of the study period, the vertical distribution of dust was similar to the commonly assumed Saharan Air Layer (SAL) transport. During the early periods of the study, dust had the highest concentrations in the marine and convective boundary layers with only a, weak dust layer in the SAL being present, a state usually associated with wintertime transport patterns. We corroborate the findings of Maring et al. that in most cases, there was an unexpected lack of vertical stratification of dust particle size. We systematically analyze processes which may impact dust vertical distribution and determine and speculate that dust vertical distribution predominately influenced by flow patterns over Africa and differential advection couple with mixing by easterly waves and regional subsidence.