Detection and Mapping of Chimassorb 944FD Antioxidant Additive in Polyethylene Using TOF-SIMS

Time-of-flight secondary ion mass spectrometry (TOF-SIMS) with either gallium or indium primary beams, has been evaluated as a method to measure the homogeneity of distribution of an antioxidant, Chimassorb 944FD (C944), in linear low-density polyethylene. The parent ion for the oligomer at m/z 599 is sufficiently weak that it could not be used to map the distribution of the additive throughout its most commonly used concentration range (0.1-0.5% (w/w)) in polyethylene. Instead, a mass fragment at m/z 58 was found to be sufficiently clear of interferences that it could be used as a surrogate for the parent ion. As a result, imaging of the antioxidant distribution was possible to concentrations as low as 0.1%, and a linear concentration calibration curve was obtained. The use of an indium primary beam improved the correlation coefficient for the quantitative measurement of C944; moreover, indium reduced the contribution from the polyethylene background at m/z 58 in relation to the total counts acquired.     

Quantitative assessment of surface-enhanced resonance Raman scattering for the analysis of dyes on colloidal silver

Factors that affect quantitative analysis by surface-enhanced resonance Raman scattering (SERRS) have been investigated using azobenzotriazol and reactive dyes. Preaggregation of the silver colloid was the most effective method to obtain repeatable and reproducible scattering. Aggregation by poly(l-lysine) or spermine provided better precision than aggregation by sodium chloride or nitric acid. Repeatable quantitative analysis was achieved with the azobenzotriazol dyes. A linear calibration graph was obtained over different concentration ranges below 10(-)(8) M, depending on the nature of the colloid. Calculations estimate that 10(-)(8) M is the concentration at which monolayer coverage of the dye on the silver colloid is achieved. Above 10(-)(8) M, there was only a minor increase in the scattering intensity from the azobenzotriazol dyes. In contrast, the reactive dyes did not give a response proportional to concentration over the range studied. The different responses obtained for the two types of dye are believed to be caused by differences in the nature of the interaction of the molecules with the silver surface. The conclusion reached is that control of the colloid preparation, aggregation process, and surface chemistry are essential for successful quantitative analysis of dyes on colloidal silver by SERRS.     

Line Harmonics of Converters with DC-Motor Loads

The line current and voltage harmonics generated by thyristor dc-motor drives, in particular with 3-phase 6-pulse dc converters, are analyzed. As industry continues to raise the power level of the converters, it is becoming more and more important to find techniques for calculating the current and voltage harmonics that avoid making the often unrealistic assumptions of the procedures used in the past. Yet these techniques must maintain, in as simple a form as possible, all the necessary curves and expressions for predicting them under the required conditions. A more accurate model of the line- current waveform is analyzed allowing for both the overlap angle and dc-current ripple, and the results are presented as a convenient set of graphs and also as a set of mathematical expressions for use on a programmable calculator. The calculated current harmonics are then used to derive the corresponding voltage harmonics toegther with their phase relationship. These voltage harmonics are then reconstructed into the relevant voltage waveform on a plotter.     

The effect of extended‐hours hemodialysis on outcomes: A systematic review and meta‐analysis

Extended‐hours hemodialysis is associated with improvements in quality of life (QoL) and mortality, but it may accelerate the loss of residual kidney function (RKF) and increase vascular access complications. Multiple established databases were systematically searched; randomized and non‐randomized studies were pooled separately. QoL outcomes were assessed using standardized mean difference (SMD), vascular access adverse events and mortality were assessed with relative risk ratios (RR). Four hundred seventy‐six patients from six trials were eligible. Data from randomized controlled trials (RCTs) could only be synthesized for vascular access adverse events and mortality, which demonstrated no significant change in vascular access adverse events (RR 1.25, 95% CI 0.88 to 1.77) or mortality (RR 2.29, 95% CI 0.60 to 8.71). Pooled data from non‐randomized trials demonstrated no significant difference in QoL (SF‐36 Physical Component Summary SMD 0.61, 95% CI ?0.10 to 1.31, SF‐36 Mental Component Summary SMD ?0.04, 95% CI ?0.61 to 0.54). RKF was assessed in one report which demonstrated a potential reduction over 12 months with extended‐hours hemodialysis. The majority of trials had high risk of bias. Extended‐hours hemodialysis was not associated with improved QoL or mortality, or increased vascular access events. Adequately powered RCTs are needed to fully assess extended‐hours hemodialysis.     

Key design issues for autostereoscopic 2‐D/3‐D displays

Abstract— Flat‐panel 2‐D/3‐D autostereoscopic displays are now being commercialized in a variety of applications, each with its own particular requirements. The autostereoscopic display designer has two key considerations to address in order to meet customer needs — the optical output of the display (defined by the output window structure) and the choice of optical components. Window structure determines 3‐D image resolution, achievable lateral and longitudinal viewing freedom, crosstalk, and 3‐D fringe contrast. Optical‐component selection determines the quality of the imaging of such windows, viewing distances, device ruggedness, thickness, and brightness. Trade‐offs in window design are described, and a comparison of the leading optical component technologies is given. Selection of Polarisation Activated Microlenses? architectures for LCD and OLED applications are described. The technology delivers significant advantages particularly for minimising nominal viewing distances in high pixel density panels and optimizing device ruggedness while maintaining display brightness.     

Experimental and simulated ultrasonic characterization of complex damage in fused silica

The growth of a laser-induced. surface damage site in a fused silica window was monitored by the ultrasonic pulse-echo technique. The laser damage was grown using 12-ns pulses of 1.053-μm wavelength light at a fluence of ~27 J/cm². The ultrasonic data were acquired after each pulse of the laser beam for 19 pulses. In addition, optical images of the surface and subsurface damage shape were recorded after each pulse of the laser. The ultrasonic signal amplitude exhibited variations with the damage size, which were attributed to the subsurface morphology of the damage site. A mechanism for the observed ultrasonic data based on the interaction of the ultrasound with cracks radiating from the damage site was tested using two-dimensional numerical simulations. The simulated results exhibit qualitatively similar characteristics to the experimental data and demonstrate the usefulness of numerical simulation as an aid for ultrasonic signal interpretation. The observed sensitivity to subsurface morphology makes the ultrasonic methodology a promising tool for monitoring laser damage in large aperture laser optics used in fusion energy research     

Simple multiplex genotyping by surface-enhanced resonance Raman scattering

The accurate detection of DNA sequences is essential for a variety of post human genome projects including detection of specific gene variants for medical diagnostics and pharmacogenomics. A specific DNA sequence detection assay based on surface-enhanced resonance Raman scattering (SERRS) and an amplification refractory mutation system (ARMS) is reported. Initially, generation of PCR products was achieved by using specifically designed allele-specific SERRS active primers. Detection by SERRS of the PCR products confirmed the presence of the sequence tested for by the allele-specific oligonucleotides. This lead directly to the multiplex genotyping of human DNA samples for the deltaF508 mutational status of the cystic fibrosis transmembrane conductance regulator gene using SERRS active primers in an ARMS assay. Removal of the unincorporated primers allowed fast and accurate analysis of the three genotypes possible in this system in a multiplex format without any separation of amplicons. The results indicate that SERRS can be used in modern genetic analysis and offers an opportunity for the development of novel assays. This is the first demonstration of the use of SERRS in multiplex genotyping and shows potential advantages over fluorescence as a detection technique with considerable promise for future development.     

SERRS. In situ substrate formation and improved detection using microfluidics

Surface-enhanced resonance Raman scattering (SERRS) of a model derivative of TNT was detected using a microflow cell designed within the framework of the lab-on-a-chip concept, using only the analyte and readily available reagents. The SERRS substrate, silver colloid, was prepared in situ, on-chip, by borohydride reduction of silver nitrate. The silver colloid was imaged within the chip using a white light microscope in either transmission or, due to the high reflectivity of the colloid, reflection mode. A fine stream of colloid approximately 30 microm in width was formed in a 250-microm-wide channel at the point where the colloid preparation reagents met. The chip was designed to produce a concentrated stream of colloid within a laminar regime, such that particles did not readily disperse into the fluid. One result of this was to reduce the effective volume of analysis. Attempts to deliberately disrupt this stream with microstructured pillars, fabricated in the fluidic channels, were unsuccessful. The chip was also designed to have the appropriate dimensions for detection using a modern Raman microscope system, which collects scattering from a very small volume. A dye derived from TNT was used as a model analyte. Quantitative behavior was obtained over 4 orders of magnitude with a detection limit of 10 fmol. This performance is between 1 and 2 orders of magnitude better than that achieved using a macroflow SERRS cell. The technique has the added advantage that both reagent consumption and effluent production are greatly reduced, leading to reduced operating costs and a decreased environmental impact     

The Effect of Yttrium on the Growth Process and Microstructure of α-Al2O3 on FeCrAl

The oxidation behavior of undoped and Y-dopedhigh-purity FeCrAl at 1200°C was investigated. Thescale-growth processes were studied using two-stage¹⁶O/¹⁸O experiments andhigh-resolution imaging SIMS. SEM, TEM, and scanning transmission electronmicroscopy-electron-dispersive X-ray spectrometry(STEM-EDS) studies were performed in order to determinethe microstructure of the oxide and the chemistry of the metal-oxide interface. An equiaxed-Al₂O₃ scale was found togrow by simultaneous outward Al and inward oxygendiffusion on the undoped FeCrAl. In contrast, a columnar-Al₂O₃ grain structure on the Y-doped FeCrAl was produced by inwardoxygen diffusion; outward Al diffusion was suppressed.Y was shown to segregate to-Al₂O₃ grain boundaries andto the metal-oxide interface.     

NK cells from human MHC class I (HLA-B) transgenic mice do not mediate hybrid resistance killing against parental nontransgenic cells

We have investigated the capacity of human MHC class I HLA-B gene products, HLA-B27, -B7 (fully human), and -B7kb (human-mouse hybrid consisting of the alpha1 and alpha2 domains of HLA-B7, and the alpha3 and cytoplasmic domains of mouse H-2Kb), expressed on mouse NK cells during ontogeny to influence NK recognition of otherwise syngeneic mouse target cells. Despite a high level of surface expression of the transgene (comparable to that of endogeneous H-2DbKb molecules), the direct killing of YAC-1 targets, and the killing of P815 targets in a redirected lysis assay, the NK effectors of these transgenic mice could not mediate hybrid resistance-like killing of nontransgenic C57BL/6 target cells either in vitro or in vivo. Splenocytes from B6-B27 mice could be used to generate CTL lines against a B27-binding peptide, implying that T cells restricted by HLA-B27 developed during ontogeny. NK cells from B6-B27 could lyse B6-B27 Con A lymphoblasts pulsed with Db-binding peptide but not B27-binding peptides. Taken together, our results show that these human HLA-B transgene products cannot function as class I MHC "self" elements for mouse NK cells, even when present throughout ontogeny.