Identification of oxidized phospholipids by electrospray ionization mass spectrometry and LC-MS using a QQLIT instrument

Phospholipids are complex and varied biomolecules that are susceptible to lipid peroxidation after attack by free radicals or electrophilic oxidants and can yield a large number of different oxidation products. There are many available methods for detecting phospholipid oxidation products, but also various limitations and problems. Electrospray ionization mass spectrometry allows the simultaneous but specific analysis of multiple species with good sensitivity and has a further advantage that it can be coupled to liquid chromatography for separation of oxidation products. Here, we explain the principles of oxidized phospholipid analysis by electrospray mass spectrometry and describe fragmentation routines for surveying the structural properties of the analytes, in particular precursor ion and neutral loss scanning. These allow targeted detection of phospholipid headgroups and identification of phospholipids containing hydroperoxides and chlorine, as well as the detection of some individual oxidation products by their specific fragmentation patterns. We describe instrument protocols for carrying out these survey routines on a QTrap5500 mass spectrometer and also for interfacing with reverse-phase liquid chromatography. The article highlights critical aspects of the analysis as well as some limitations of the methodology.

Wavefront analyzers induce instrument myopia

PURPOSE: To assess the accuracy of three wavefront analyzers versus a validated binocular open-view autorefractor in determining refractive error in non-cycloplegic eyes. METHODS: Eighty eyes were examined using the SRW-5000 open-view infrared autorefractor and, in randomized sequence, three wavefront analyzers: 1) OPD-Scan (NIDEK, Gamagori, Japan), 2) WASCA (Zeiss/Meditec, Jena, Germany), and 3) Allegretto (WaveLight Laser Technologies AG, Erlangen, Germany). Subjects were healthy adults (19 men and 21 women; mean age: 20.8 +/- 2.5 years). Refractive errors ranged from +1.5 to -9.75 diopters (D) (mean: +1.83 +/- 2.74 D) with up to 1.75 D cylinder (mean: 0.58 +/- 0.53 D). Three readings were collected per instrument by one examiner without anticholinergic agents. Refraction values were decomposed into vector components for analysis, resulting in mean spherical equivalent refraction (M) and J0 and J45 being vectors of cylindrical power at 0 degrees and 45 degrees, respectively. RESULTS: Positive correlation was observed between wavefront analyzers and the SRW-5000 for spherical equivalent refraction (OPD-Scan, r=0.959, P<.001; WASCA, r=0.981, P<.001; Allegretto, r=0.942, P<.001). Mean differences and limits of agreement showed more negative spherical equivalent refraction with wavefront analyzers (OPD-Scan, 0.406 +/- 0.768 D [range: 0.235 to 0.580 D] [P<.001]; WASCA, 0.511 +/- 0.550 D [range: 0.390 to 0.634 D] [P<.001]; and Allegretto, 0.434 +/- 0.904 D [range: 0.233 to 0.635 D] [P<.001]). A second analysis eliminating outliers showed the same trend but lower differences: OPD-Scan (n=75), 0.24 +/- 0.41 D (range: 0.15 to 0.34 D) (P<.001); WASCA (n=78), 0.46 +/- 0.47 D (range: 0.36 to 0.57 D) (P<.001); and Allegretto (n=77), 0.30 +/- 0.62 D (range: 0.16 to 0.44 D) (P<.001). No statistically significant differences were noted for J0 and J45. CONCLUSIONS: Wavefront analyzer refraction resulted in 0.30 D more myopia compared to SRW-5000 refraction in eyes without cycloplegia. This is the result of the accommodation excess attributable to instrument myopia. For the relatively low degrees of astigmatism in this study (<2.0 D), good agreement was noted between wavefront analyzers and the SRW-5000. Copyright (C) 2006 SLACK Incorporated

Automobile friction materials: a test instrument and technique for determining dynamic mechanical properties in relation to brake squeal

This study is primarily concerned with the problem of break-squeal in disc brakes, using moulded organic disc pads. Moulded organic friction materials are complex composites and due to this complexity it was thought that they are unlikely to be of uniform composition. Variation in composition would under certain conditions of the braking system, cause slight changes in its vibrational characteristics thus causing resonance in the high audio-frequency range. Dynamic mechanical propertes appear the most likely parameters to be related to a given composition's tendency to promote squeal. Since it was necessary to test under service conditions a review was made of all the available commercial test instruments but as none were suitable it was necessary to design and develop a new instrument. The final instrument design, based on longitudinal resonance, enabled modulus and damping to be determined over a wide range of temperatures and frequencies. This apparatus has commercial value since it is not restricted to friction material testing. Both used and unused pads were tested and although the cause of brake squeal was not definitely established, the results enabled formulation of a tentative theory of the possible conditions for brake squeal. The presence of a temperature of minimum damping was indicated which may be of use to braking design engineers. Some auxilIary testing was also performed to establish the effect of water, oil and brake fluid and also to determine the effect of the various components of friction materials.

Large-volume metrology instrument selection and measurability analysis

A wide range of metrology processes are involved in the manufacture of large products. In addition to the traditional tool-setting and product-verification operations, increasingly flexible metrology-enabled automation is also being used. Faced with many possible measurement problems and a very large number of metrology instruments employing diverse technologies, the selection of the appropriate instrument for a given task can be highly complex. Also, as metrology has become a key manufacturing process, it should be considered in the early stages of design, and there is currently very little research to support this. This paper provides an overview of the important selection criteria for typical measurement processes and presents some novel selection strategies. Metrics that can be used to assess measurability are also discussed. A prototype instrument selection and measurability analysis application is also presented, with discussion of how this can be used as the basis for development of a more sophisticated measurement planning tool. © 2010 Authors.

Naturally occurring data as research instrument:analyzing examination responses to study the novice programmer

In New Zealand and Australia, the BRACElet project has been investigating students' acquisition of programming skills in introductory programming courses. The project has explored students' skills in basic syntax, tracing code, understanding code, and writing code, seeking to establish the relationships between these skills. This ITiCSE working group report presents the most recent step in the BRACElet project, which includes replication of earlier analysis using a far broader pool of naturally occurring data, refinement of the SOLO taxonomy in code-explaining questions, extension of the taxonomy to code-writing questions, extension of some earlier studies on students' 'doodling' while answering exam questions, and exploration of a further theoretical basis for work that until now has been primarily empirical.

High accuracy mobile robot positioning using an external large volume metrology instrument

A method of accurately controlling the position of a mobile robot using an external Large Volume Metrology (LVM) instrument is presented in this paper. Utilizing a LVM instrument such as the laser tracker in mobile robot navigation, many of the most difficult problems in mobile robot navigation can be simplified or avoided. Using the real- Time position information from the laser tracker, a very simple navigation algorithm, and a low cost robot, 5mm repeatability was achieved over a volume of 30m radius. A surface digitization scan of a wind turbine blade section was also demonstrated, illustrating possible applications of the method for manufacturing processes. © Springer-Verlag Berlin Heidelberg 2010.

Large volume metrology instrument selection and measurability analysis

Metrology processes used in the manufacture of large products include tool setting, product verification and flexible metrology enabled automation. The range of applications and instruments available makes the selection of the appropriate instrument for a given task highly complex. Since metrology is a key manufacturing process it should be considered in the early stages of design. This paper provides an overview of the important selection criteria for typical measurement processes and presents some novel selection strategies. Metrics which can be used to assess measurability are also discussed. A prototype instrument selection and measurability analysis application is presented with discussion of how this can be used as the basis for development of a more sophisticated measurement planning tool. © Springer-Verlag Berlin Heidelberg 2010.