Analysis of bit error rate and power penalty for a birefringent wavelength division multiplexer

The power penalty and bit error rate degradation encountered when using wavelength division multiplexing devices is analyzed. Analysis is applied to the birefringent wavelength division multiplexer (BWDM) with a sinusoidal transfer function.¹ The degradation in bit error rate is attributed to laser mode partition noise and crosstalk noise.     

PHOTODYNAMIC DESTRUCTION OF LYSOSOMES MEDIATED BY NILE BLUE PHOTOSENSITIZERS

Previous studies have established that a number of Nile blue derivatives are potent photosensitizers and that they are localized primarily in the lysosomes. The present study examines whether the lysosome is a main target of the photocytotoxic action mediated by these sensitizers. Chosen for this study were NBS-61 and sat-NBS, which represented, respectively, derivatives with high and moderate degrees of lysosomal selectivity. Overall results indicated that both derivatives are very effective in mediating a photodestruction of lysosomes. This is indicated by the light-and drug-dose-dependent losses of acid phosphatase staining particles, reduction of hexosaminidase in the lysosomecontaining subcellular fraction, and impairment of the lysosomes to take up and sequester acndine orange. Ultrastructurally, swollen and ruptured lysosomes were seen as one of the first evidences of cell damage mediated by these photosensitizers. However, the study also showed that sat-NBS, which is less lysosomal selective, was less effective in mediating lysosomal destruction. Also, the degree of lysosomal destruction mediated by sat-NBS did not parallel the degree of cytotoxicity generated. This implies that for derivatives that are not exclusively localized in the lysosome, other subcellular sites may also be damaged by the photodynamic action and may play a role in the photocytotoxic process.     

Introduction of d‐Glutamate at a Critical Residue of Aβ42 Stabilizes a Prefibrillary Aggregate with Enhanced Toxicity

The amyloid beta peptide 42 (Aβ42) is an aggregation‐prone peptide that plays a pivotal role in Alzheimer′s disease. We report that a subtle perturbation to the peptide through a single chirality change at glutamate 22 leads to a pronounced delay in the β‐sheet adoption of the peptide. This was accompanied by an attenuated propensity of the peptide to form fibrils, which was correlated with changes at the level of the fibrillary architecture. Strikingly, the incorporation of d ‐glutamate was found to stabilize a soluble, ordered macromolecular assembly with enhanced cytotoxicity to PC12 cells, highlighting the importance of advanced prefibrillary Aβ aggregates in neurotoxicity.     

Critical compilation of solute-micelle binding constants and related parameters from micellar liquid chromatographic measurements

Over 150 solute-micelle association (binding) constants and free solute retention factors are reported for a variety of neutral compounds and PTH-amino acids. The solute-micelle parameters were calculated from critically evaluated micellar liquid chromatographic data. The potential utility of these parameters for the optimization of micellar liquid chromatography and micellar electrokinetic capillary chromatography, including selection of the surfactant and/or stationary phase and the optimization of surfactant concentration, is briefly discussed.     

Effect of class I and II organic modifiers on retention and selectivity in vesicle electrokinetic chromatography

Vesicles are large aggregates of surfactant monomers consisting of a spherical bilayer surrounding an internal cavity of solvent. The bilayer structure allows vesicles to be attractive models for the study of various transmembrane and binding processes. The use of thermodynamically stable vesicles (TSV) formed from oppositely charged surfactants for use as a pseudostationary phase in electrokinetic chromatography (EKC) was first accomplished using dodecyltrimethylammonium bromide and sodium dodecyl sulfate (DTAB/SDS). Surfactant vesicles have demonstrated enhanced separation characteristics compared to conventional micelles in EKC, although only investigated in aqueous media. Organic modifiers have been widely studied and used in EKC to enhance separation conditions. In this study, vesicles formed from cetyltrimethylammonium bromide and sodium octyl sulfate (CTAB/SOS) were investigated in the presence of "class I and II" organic modifiers. Electrophoretic and chromatographic parameters were examined as well as linear solvation energy relationship analysis (LSER) to characterize the effects of the modifiers on retention and selectivity in EKC. LSER analysis is a useful way to quantitatively investigate solute/solvent interactions responsible for retention and selectivity.     

A novel approach for the determination of detection limits for metal analysis of environmental water samples

Despite the widespread use of the USEPA method (U.S. Environmental Protection Agency, 40 CFR 136 Appendix B) for the determination of method detection limit (MDL), criticisms have been raised that the method does not account for measurement bias and outliers that subsequently lead to a common misunderstanding of the requirement for the determination of MDL. This paper demonstrates that it is difficult to follow the USEPA method for verifying the MDL for analysis involving multiple metals and proposes a precision and bias criterion for determining the MDL. A multiple-point fitted profile, based on the correlation between relative standard deviation (RSD) and concentration, is used to derive a robust MDL value. Representative examples of As, Ca, Cr, and Cu are used to illustrate this procedure. A procedure for identifying outliers is also discussed.     

The global attractivity of the rational difference equation

This paper studies the behavior of positive solutions of the recursive equation

with and , where . We prove that if , and , then tends to . This complements several results in the recent literature, including the main result in K. S.  Berenhaut, J. D. Foley and S. Stevic, The global attractivity of the rational difference equation , Proc. Amer. Math. Soc., 135 (2007) 1133-1140.

     

Microcontact printed antibodies on gold surfaces: function, uniformity, and silicone contamination

The function of microcontact printed protein was investigated using surface plasmon resonance (SPR) imaging, X-ray photoelectron spectroscopy spectroscopy (XPS), and XPS imaging. We chose to analyze a model protein system, the binding of an antibody from solution to a microcontact printed protein antigen immobilized to a gold surface. SPR imaging experiments indicated that the microcontact printed protein antigen was less homogeneous, had increased nonspecific binding, and bound less antibody than substrates to which the protein antigen had been physically adsorbed. SPR images of substrates contacted with a poly(dimethylsiloxane) stamp inked with buffer alone (i.e., no protein) revealed that significant amounts of silicone oligomer were transferred to the surface. The transfer of the silicone oligomer was not homogeneous, and the oligomer nonspecifically bound protein (BSA and IgG) from solution. XPS spectroscopy and imaging were used to quantify the amount of silicon (due to the presence of silicone oligomer), as well as the amounts of other elements, transferred to the surface. The results suggest that the silicone oligomer introduced by the printing process reduces the overall binding capacity of the microcontact-printed protein compared to physically adsorbed protein.