Analysis of the low molecular weight fraction of serum by LC-dual ESI-FT-ICR mass spectrometry: precision of retention time, mass, and ion abundance

This study quantifies the experimental uncertainty for LC retention time, mass measurement precision, and ion abundance obtained from replicate nLC-dual ESI-FT-ICR analyses of the low molecular weight fraction of serum. We used ultrafiltration to enrich the < 10-kDa fraction of components from the high-abundance proteins in a pooled serum sample derived from ovarian cancer patients. The THRASH algorithm for isotope cluster detection was applied to five replicate nLC-dual ESI-FT-ICR chromatograms. A simple two-level grouping algorithm was applied to the more than 7000 isotope clusters found in each replicate and identified 497 molecular species that appeared in at least four of the replicates. In addition, a representative set of 231 isotope clusters, corresponding to 188 unique molecular species, were manually interpreted to verify the automated algorithm and to set its tolerances. For nLC retention time reproducibility, 95% of the 497 species had a 95% confidence interval of the mean of +/- 0.9 min or less without the use of chromatographic alignment procedures. Furthermore, 95% of the 497 species had a mass measurement precision of < or = 3.2 and < or = 6.3 ppm for internally and externally calibrated spectra, respectively. Moreover, 95% of replicate ion abundance measurements, covering an ion abundance range of approximately 3 orders of magnitude, had a coefficient of variation of less than 62% without using any normalization functions. The variability of ion abundance was independent of LC retention time, mass, and ion abundance quartile. These measures of analytical reproducibility establish a statistical rationale for differentiating healthy and disease patient populations for the elucidation of biomarkers in the low molecular fraction of serum.     

The Characterization of Transistor Electrical Overstress Failure Probability Density Functions

An empirical approach for characterizing transistor emitter-base failure threshold probability density functions is presented. The data analyzed come from a program of experiments designed to test component failures due to electrical overstress transients. First, an empirical distribution is obtained which describes the variation of the relative width of a large set of measured failure threshold distributions. Using this distribution, a technique is presented for obtaining threshold distribution parameters when the mean failure threshold is assumed to be known, Second, a technique is presented for combining the distribution of relative width with a derived mean uncertainty estimate. This yields a probabilistic statement of the threshold distribution parameters based on the estimated mean and the described uncertainty distributions. This approach is used to provide probabilistic statements on threshold lower bounds. An example of the use of these techniques is included.     

Effectiveness of SO2 sorbents by thermogravimetry-combustion with coal

A new experimental method is described for non-isothermal thermogravimetry (TG) involving combustion of mixtures of sieved coal with sieved calcium-containing sorbents. This rapid TG method utilizes a baseline for TG combustion of coal alone, derives an equation that gives a semi-quantitative measure (±10% repeatability) of the coal's reactive sulphur retained by the sorbent, the extent of retention of S0₂ generated in situ during combustion varying with different sorbents. The method permits direct variation in separate experiments of the calcium-to-sulphur ratio during combustion and relative ranking of different sorbents by retention of reactive sulphur in combustion. Relative rankings are presented for three pre-calcined natural stones (two limestones and one dolomite); these results correlate with relative rankings from another TG method reported in the literature. It is suggested that this new method is useful for pre-screening the effectiveness of S0₂ sorbents considered for use in fluidizedbed combustion of coal.     

Internal friction,acoustic emission and fatigue in metals for high amplitude ultrasonic frequencies

High amplitudes (strains up to 3 × 10^?3) have been used in studying internal friction, acoustic emission and fatigue in metals. The internal friction in the high amplitude range is due to breakaway of dislocations from pinning points and by the generation of Frank-Read loops which results in plastic strain. There are two plastic regions, one when the added loops are held up by the grain boundaries, and the second when the loops break through the grain boundaries. In the second region, slip bands are produced in the metal. As the amplitude increases slip bands can join up and fatigue in the metal occurs. Ultrasonic frequencies are useful for studying fatigue since a large number of cycles can occur in a reasonable time.Acoustic emission—that is, a noise in the sample associated with the dislocation motion—can be studied by putting transducers on the sample. It is shown that the emission is closely associated with the internal friction since it goes through two regions in the plastic range.     

A universal equivalent circuit model for the impedance response of composites

An equivalent circuit model has been developed to describe the impedance response of composites with insulating or conductive particles or fibers. Required inputs are the matrix conductivity, the intrinsic conductivity of the particles, and their volume fraction. The model has general applicability to systems involving moderately conductive matrices, insulating or conductive particles/fibers, and, in the case of conducting particles, the presence of a high impedance coating element on the particle surfaces. Ramifications for the use of impedance spectroscopy in the characterization of composite properties and the monitoring of their performance under load are discussed.     

Signal extraction and optical design for an advanced gravitational-wave interferometer

We present an experimental demonstration of a locking and control scheme for an interferometer using a power-recycled resonant sideband extraction configuration and show that the measured response to mirror vibrations matches an optical model. We discuss some aspects of resonant sideband extraction that are relevant to gravitational-wave detection.     

Analysis of the impedance spectra of short conductive fiber-reinforced composites

The presence of small amounts of short conductive fibers in a composite of finite matrix conductivity results in the subdivision of the one matrix impedance arc into two separate low and high frequency arcs in the complex impedance plane. These features are attributable to a frequency-switchable interfacial impedance on the fiber surfaces, rendering them insulating at DC and low AC frequencies, but conducting at intermediate frequencies. A combination of physical simulations (single wires in tap water) and pixel-based computer modeling was employed to investigate the roles of fiber pull-out, debonding, and orientation on the impedance response of fiber-reinforced composites. The ratio of the low frequency arc size to the overall DC resistance (-parameter) is sensitive to pull-out and/or debonding, especially when a fiber just barely makes contact with the matrix. The -parameter is also quite sensitive to fiber orientation with respect to the direction of the applied field. Ramifications for the characterization of cement, ceramic, and polymer matrix composites are discussed.     

Immunolocalization of steroidogenic enzymes in the corpus luteum and placenta of the Japanese black bear, Ursus thibetanus japonicus, during pregnancy

The Japanese black bear, Ursus thibetanus japonicus, is a seasonal breeder and shows delayed implantation for several months during pregnancy. The objective of this study was to clarify the steroidogenic capability of the corpus luteum and placenta during pregnancy, including both delayed implantation and fetal development, by immunolocalization of steroidogenic enzymes in these organs of the Japanese black bear. Ovaries and placentae from 15 wild Japanese black bears, which had been killed legally by hunters and were thought to be pregnant, were used in an immunocytochemical study to localize the cholesterol side chain cleavage cytochrome P450 (P450scc), 3beta-hydroxysteroid dehydrogenase (3betaHSD), 17alpha-hydroxylase cytochrome P450 (P450c17) and aromatase cytochrome P450 (P450arom) by the avidin-biotin-peroxidase complex method using polyclonal antisera raised in mammals against P450scc, 3betaHSD, P450c17 and P450arom. P450scc and 3betaHSD were localized in all luteal cells throughout pregnancy. P450c17 was present in a few luteal cells, especially in the outer area of the corpus luteum throughout pregnancy, but the number of positively immunostained cells decreased during the post-implantation period. Cells positively immunostained for P450c17 were significantly smaller than negatively immunostained cells (P < 0.01). P450arom was present sporadically in a few luteal cells throughout pregnancy, but the number of positively immunostained cells decreased during the post-implantation period. The size of cells positively immunostained for P450arom was not significantly different from that of negatively immunostained cells. The whole placenta was negatively immunostained for P450scc, 3betaHSD and P450c17, but P450arom was present in the syncytiotrophoblasts and endothelial cells of maternal blood vessels. These results indicate that, in the Japanese black bear, corpora lutea are a source of progesterone which may play an important role in the maintenance of delayed implantation and fetal development during pregnancy. Corpora lutea have a minimum capability to synthesize androgen in small luteal cells and oestrogen in normal-sized luteal cells during pregnancy, and placentae have the ability to synthesize oestrogen during late pregnancy.     

Library design using BCUT chemistry-space descriptors and multiple four-point pharmacophore fingerprints: simultaneous optimization and structure-based diversity

New applications of fingerprints of multiple potential 4-point three-dimensional (3D) pharmacophores in combinatorial library design and virtual screening are presented. Preliminary results demonstrating the feasibility of a simulated annealing process for combinatorial reagent selection that concurrently optimizes product diversity in BCUT chemistry space and in terms of unique 4-point pharmacophores are discussed, and the advantage of using a customized chemistry-space derived for the library design is demonstrated. In addition, an extension to the multiple pharmacophore method for structure-based design that uses the shape of the target site as an additional constraint is presented. This development enables the docking process to be quantified in terms of the number and identities of the pharmacophoric hypotheses that can be matched by a compound or a library of compounds. The design of an example combinatorial library based on the Ugi condensation reaction and a serine protease active site is described.     

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