Cryptographic Key Agreement for Mobile Radio

Hassan, A. A., Stark, W. E., Hershey, J. E., and Chennakeshu, S., Cryptographic Key Agreement for Mobile Radio,Digital Signal Processing6(1996), 207–212.The problem of establishing a mutually held secret cryptographic key using a radio channel is addressed. The performance of a particular key distribution system is evaluated for a practical mobile radio communications system. The performance measure taken is probabilistic, and different from the Shannon measure of perfect secrecy. In particular, it is shown that by using a channel decoder, the probability of two users establishing a secret key is close to one, while the probability of an adversary generating the same key is close to zero. The number of possible keys is large enough that exhaustive search is impractical.     

Interpretation revealed in the blink of an eye: Depressive bias in the resolution of ambiguity.

Self-report measures of interpretation have been criticized on methodological grounds. An approach is introduced in this article that enables the assessment of interpretive bias with a greater degree of methodological rigor than previously has been the case. Psychophysiological researchers have established that the magnitude of the human blink reflex is augmented when elicited during negative rather than neutral imagery. The 1st experiment demonstrates that the blink reflex is sensitive to the emotional valence of imagery evoked by interpretations imposed on ambiguous stimuli. In the 2nd experiment, this measure is used to assess interpretations imposed on ambiguous stimuli by individuals who differ in depression levels. The findings are consistent with the hypothesis that depression is associated with a negative interpretive bias. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Intracellular staining for HIV-specific IFN-gamma production: statistical analyses establish reproducibility and criteria for distinguishing positive responses

The cellular immune response plays a pivotal role in controlling the spread of HIV-1 infection by lysing virally infected cells and producing potent antiviral cytokines, such as interferon-gamma (IFN-gamma). Flow cytometric methods have been established to evaluate the contribution of both CD4 and CD8 subsets of T lymphocytes to the immune response to HIV by measuring their production of intracellular IFN-gamma following brief antigenic stimulation. We present a statistical treatment of intracellular cytokine staining (ICS) data that is aimed at establishing the reproducibility and robustness of this assay for use in HIV clinical trials. Comparisons of responses from HIV-seronegative and seropositive individuals were used to establish a 2-fold criterion for distinguishing positive responses with a low probability of false positives (<1%). Additional comparisons established that the reproducibility of the assay is between 1.4 and 2.0-fold depending on the magnitude of the response. Little variability was demonstrated between multiple operators for both the execution and analysis components of these experiments (<10% difference with 95% confidence). We conclude that the statistical criteria established by these analyses allow for the accurate detection and comparison of positive responses. Using these statistical criteria, the ICS assay is sufficiently robust for use in HIV-specific vaccine trials.     

Preparation and characterization of siloxane-containing thermoplastic polymides

Copolyimides and homopolyimides of bis(γ-aminopropyl)tetramethyldisiloxane and 3,3′-diaminobenzophenone have been prepared with benzophenonetetracarboxylic dianhydride. The properties of the copolyimides were compared with those of the homopolyimides to assess the effect of incorporation of siloxane groups in the backbone. Applications of the polymers as adhesives and mouldings are discussed.     

Effect of conformation and drop properties on surface-enhanced Raman spectroscopy of dried biopolymer drops

Biofluids are complex solutions consisting of small ions and large biopolymers such as DNA, proteins, or proteoglycans. Biopolymers affect fluid properties but their effect on drop deposition has not been examined. Hyaluronic acid (HA), an important component in synovial fluid, was chosen as a model biopolymer, and examined using surface-enhanced Raman spectroscopy (SERS). Nanoliter volumes of HA solutions were dried onto a patterned SERS substrate and spectra were collected from the dried hyaluronic acid drops with a near-infrared Raman microscope. Characteristic hyaluronic acid bands were examined. Capillary viscometry measured properties of HA solutions, and entanglement behavior was also modeled using scaling theory principles. Viscosity measurements were incorporated into models of suspended particle droplets to account for the effect of inter-chain attraction on droplet formation. Microscope images were used to evaluate the shape of the dried drop. Relative drop thickness was estimated from concentric rings found at drop edges using established models of light interference by thin films. We found SERS spectra were sensitive not only to polymer conformation, but also to type of deposition (ring versus uniform), and the thickness of the resulting deposition. These data suggest an approach to elucidate the effects of biopolymers and dehydrated biofluids on SERS analysis.     

Fluorescent Mechanism‐Based Probe for Aerobic Flavin‐Dependent Enzyme Activity

Diversity in non‐ribosomal peptide and polyketide secondary metabolism is facilitated by interactions between biosynthetic domains with discrete monomer loading and their cognate tailoring enzymes, such as oxidation or halogenation enzymes. The cooperation between peptidyl carrier proteins and flavin‐dependent enzymes offers a specialized strategy for monomer selectivity for oxidization of small molecules from within a complex cellular milieu. In an effort to study this process, we have developed fluorescent probes to selectively label aerobic flavin‐dependent enzymes. Here we report the preparation and implementation of these tools to label oxidase, monooxygenase, and halogenase flavin‐dependent enzymes.     

Preliminary Evaluation of Hybrid Titanium Composite Laminates

In this study, the mechanical response of hybrid titanium composite laminates (HTCL) was evaluated at room and elevated temperatures. Also, the use of an elastic-plastic laminate analysis program for predicting the tensile response from constituent properties was verified. The improvement in mechanical properties achieved by the laminates was assessed by comparing the results of static strength and constant amplitude fatigue tests with those for monolithic titanium sheet. Two HTCL were fabricated with different fiber volume fractions, resin layer thicknesses and resins. One panel was thicker and was poorly bonded in comparison with the other. Consequently, the former had a lower tensile strength, while fewer cracks grew in this panel and at a slower rate. Both panels showed an improvement in fatigue life of almost two orders of magnitude. The model predictions were also in good agreement with the experimental results for both HTCL panels.     

Adhesive Evaluation for New Forms of LARCTM-TPI

LARC^TM-TPI is a linear aromatic polyimide that was developed at NASA Langley Research Center in the 1970's and subsequently licensed to Mitsui Toatsu Chemicals, Inc., (MTC) in Japan. This company has made it easier to process for use in application as a structural adhesive or as a composite matrix resin. The present forms that exist are (1) high melt viscosity or Low Flow Grade (LFG); (2) medium melt viscosity or Medium Flow Grade (MFG); and (3) low melt viscosity or High Flow Grade (HFG). As expected, the low melt viscosity material is the easiest to process but has poor toughness; the high melt viscosity material is very tough but is more difficult to process. Because of these two extreme situations we have worked closely with MTC to develop an optimized system. This work has resulted in the medium melt viscosity material as well as two other modified or blended medium-flow variations.

These novel forms of LARC^TM-TPI have resulted in adhesives that can be melt processed at pressures as low as 0.01 MPa (15 psi) at temperatures between 343–371°C (650–700°F). Evaluation of adhesive performance has been accomplished using lap shear specimens and evaluating flow, wet out and shear strength. Initial strengths for these optimized materials range from 20.7–41.4 MPa (3000–6000 psi) at room temperature and 13.8–20.7 MPa (2000–3000 psi) at elevated test temperatures.     

Cumene hydrogenation turnover rates on Mo2C: CO and O2 as probes of the active site

The use of CO and O₂ chemisorption to titrate surface sites on β-Mo₂C was examined using cumene (isopropylbenzene) hydrogenation as a test reaction. The tests were carried out using β-Mo₂C samples prepared at two different temperatures so as to deposit different amounts of pyrolytic carbon on their surfaces. Synthesis at 961 K produced a surface that was substantially free of pyrolytic carbon (90% clean), while synthesis at 981 K produced a surface that was contaminated with carbon (25% clean). It was found that O₂ uptakes were about six times higher than CO uptakes, but both gave consistent turnover rates for the reaction. This revised version was published online in July 2006 with corrections to the Cover Date.     

Conservation and diversity of eukaryotic translation initiation factor eIF3

The largest of the mammalian translation initiation factors, eIF3, consists of at least eight subunits ranging in mass from 35 to 170 kDa. eIF3 binds to the 40 S ribosome in an early step of translation initiation and promotes the binding of methionyl-tRNAi and mRNA. We report the cloning and characterization of human cDNAs encoding two of its subunits, p110 and p36. It was found that the second slowest band during polyacrylamide gel electrophresis of eIF3 subunits in sodium dodecyl sulfate contains two proteins: p110 and p116. Analysis of the cloned cDNA encoding p110 indicates that its amino acid sequence is 31% identical to that of the yeast protein, Nip1. The p116 cDNA was cloned and characterized as a human homolog of yeast Prt1, as described elsewhere (Methot, N., Rom, E., Olsen, H., and Sonenberg, N. (1997) J. Biol. Chem. 272, 1110-1116). p36 is a WD40 repeat protein, which is 46% identical to the p39 subunit of yeast eIF3 and is identical to TRIP-1, a phosphorylation substrate of the TGF-beta type II receptor. The p116, p110, and p36 subunits localize on 40 S ribosomes in cells active in translation and co-immunoprecipitate with affinity-purified antibodies against the p170 subunit, showing that these proteins are integral components of eIF3. Although p36 and p116 have homologous protein subunits in yeast eIF3, the p110 homolog, Nip1, is not detected in yeast eIF3 preparations. The results indicate both conservation and diversity in eIF3 between yeast and humans.