The bubble oxygenator as a source of gaseous microemboli

The role of the bubble oxygenator in the production of gaseous microemboli (GME) in the extracorporeal circuit is a consequence of both the mechanism by which the oxygenator functions and the designs employed to implement that mechanism. In the past ultrasonic devices were used to evaluate the production of GME by bubble oxygenators. This report describes the application of dilatometry to provide a more quantitative determination of GME production. This technique uses the compressibility of gases to measure their volume in a gas-liquid mixture. The results obtained provide a new perspective for the study of GME in the extracorporeal circuit.     

A Method for the Verification of Wire Crimp Compression Using Ultrasonic Inspection

The development of a new ultrasonic measurement technique to assess wire crimp terminations is discussed. The amplitude change of a compressional ultrasonic wave propagating at right angles to the wire axis and through the junction of a crimp termination is shown to correlate with the results of a destructive pull test. The case of incomplete compression of crimped connections is ultrasonically tested, and the results are correlated with pull tests. Results show that the ultrasonic measurement technique consistently predicts good crimps when the ultrasonic transmission is above a certain threshold amplitude level. A quantitative measure of the quality of the crimped connection based on the ultrasonic energy transmitted is shown to respond accurately to crimp quality. A wave propagation model, describes the compressional ultrasonic wave propagation through the junction during the crimping process. This model is in agreement within 6% of the ultrasonic measurements. A prototype instrument for applying this technique while wire crimps are installed is also presented. The instrument is based on a two-jaw type crimp tool suitable for butt-splice type connections. A comparison of the results of two different instruments is presented and shows reproducibility between instruments within a 95% confidence bound.     

Effects of fragile ions on mass resolution and on isolation for tandem mass spectrometry in the quadrupole ion trap mass spectrometer.

In the quadrupole ion trap, it has been noted that factors other than an ion's mass and charge may affect its measured m/z, resulting in compound-dependent, or "chemical", mass shifts. We propose that ions can exhibit a chemical mass shift because they are "fragile" and may fragment during the application of resonance ejection during mass analysis; these effects were studied using ions that include protonated, deprotonated, and adduct ions of explosives, acylcarnitines, and macrolide antibiotics. Fragile ions affect mass resolution by causing broader peaks than nonfragile ions, especially at slower scan speeds, as the result of the application of resonance ejection. Fragile ions may also be fragmented by the application of the isolation waveform during selection of the parent ion for tandem mass spectrometry experiments, making it impossible to achieve unit isolation of a fragile ion. To obtain adequate isolation intensity, the isolation waveform notch width must be increased and the time period of isolation must be decreased. Fragile ions also require lower optimum collision energy to achieve efficient collision-induced dissociation. We have developed criteria for the determination of the degree of ion fragility based upon experimental results.     

Simultaneous determination of trace levels of nine haloacetic acids in biological samples as their pentafluorobenzyl derivatives by gas chromatography/tandem mass spectrometry in electron capture negative ion chemical ionization mode

Haloacetic acids (HAAs) are environmentally and medically important chemicals. No analytical method is currently available to analyze EPA-regulated HAAs in biological samples at environmentally relevant low concentrations. Clinical studies of this class of chemicals are also limited by the lack of analytical techniques of high sensitivity and precision. We now report a new analytical method using gas chromatography/ion trap mass spectrometry for quantifying nine HAAs present inplasma, urine, and water at picogram per milliliter levels. The derivatization reactions of HAAs with pentafluorobenzyl bromide were optimized and detection with an electron capture negative ion chemical ionization mode was employed to enhance the sensitivity. Selected ion monitoring and selected reaction monitoring methods were utilized for quantitation. The detection limits of HAAs in plasma, urine, and water were 25-1000 pg/mL. Accuracies varied from 86.6 to 118.1% (intraday) and 81.7 to 119.6% (interday). Precisions (CV) varied from 0.9 to 19.9% (intraday) and 0.8 to 19.8% (interday), and linearities (r2) varied from 0.9732 to 0.9998 (intraday) and 0.9422 to 0.9987 (interday), respectively. Methyl tertbutyl ether and diethyl ether provided the highest extraction recoveries for the HAAs (74.9-107.2%). The method was applied successfully to a kinetic investigation of low levels of HAAs in humans consuming chlorinated drinking water.     

The synthetic-analytic listening task for modulated signals

The synthetic-analytic listening task (SALT) developed by Dye and colleagues [Dye et al., J. Acoust. Soc. Am. 96, 2720-2731 (1994)] was applied to a task in which an amplitude-modulated tonal carrier was presented as a target during the standard stimulus. The standard stimulus was followed by a test stimulus in which the target along with another amplitude-modulated carrier (the distractor) was presented. The listener determined if in the test stimulus, the target (which was presented along with the distractor) was higher or lower in modulation depth than when the target was presented alone as the standard stimulus. The target and distractor were either 1- or 4-kHz carriers modulated at one of ten depths of modulation during the test stimulus at modulation rates ranging from 4 to 64 Hz. SALT was used to estimate the relative weight listeners assigned to the target and distractor as a function of the difference between their modulation rates, both for target carrier frequencies above and for target carrier frequencies below the distractor carrier frequency. When the target and distractor were modulated at the same rate, the target and distractor weights were equal, indicating synthetic listening. When the target and distractor differed in modulation rate, the listener gave more weight to the target suggesting a form of analytic listening. The result demonstrate the applicability of SALT to studies of modulation and reinforce the claim that different spectral components modulated with the same modulation pattern are processed synthetically.     

Drosophila melanogaster Stress Odorant (dSO) Displays the Characteristics of an Interspecific Alarm Cue

Journal of Chemical Ecology - Organisms depend on visual, auditory, and olfactory cues to signal the presence of danger that could impact survival and reproduction. Drosophila melanogaster emits an...     

Lead contamination of inexpensive plastic jewelry

The neurological hazards of lead to children are well-known. As a result of recent documented cases of lead poisoning, regulatory attention in the United States has focused on the lead content of children's metal jewelry. By contrast, little is known about the possible hazards of plastic jewelry items. The objective of this study was to determine whether inexpensive plastic jewelry is a possible source of toxic lead for children. Samples of more than 100 inexpensive plastic jewelry items were analyzed for lead content. Beads were screened by soaking in 1 M nitric acid. Nine items found to release more than 30 microg of lead per bead were further tested for accessible lead, and scrapings of the bead coatings were analyzed for total lead content. The maximum accessible lead found was 49 microg per bead, which is below the current US Consumer Product Safety Commission limit of 175 microg. However, when the number of beads in each item was taken into account, six of the nine leaded samples contained more than 175 microg accessible lead per item. The lead in these items appears to be associated with lead-based paints used to produce glossy coatings on imitation pearls and similar items. Coatings obtained by scraping individual beads contained 3.5-23% lead, which far exceeds the US regulatory limit of 0.06% lead in paints on items intended for children. Our results demonstrate that plastic jewelry items merit the attention of public health and consumer protection agencies seeking to limit the exposure of children to lead.     

Nanoscale viscoelastic properties of an aligned collagen scaffold

Localised mechanical properties for aligned collagen scaffolds derived from Type 1 collagen were determined by application of nanoindentation based techniques. It was possible to measure the modulus and hardness with nanometre control over the depth of penetration and quasi-static testing under displacement control yielded average modulus values ranging from 1.71 GPa to 3.31 GPa; a narrower range of values than obtained by other methods. Hardness values of 222 MPa to 256 MPa were recorded and showed little scatter, highlighting the potential of nanoindentation hardness values as a reproducible and accurate measure of soft material properties. Open loop Load-displacement curves for the collagen exhibited the expected shapes for a viscoelastic material and it was thus possible to apply dynamic stiffness measurement at the nano scale. As well as determining the storage modulus (0.71 GPa) and the loss modulus (0.40 GPa) at the sub-micron length and nano depth resolution it was also possible to discriminate between surface and bulk readings allowing surface effects to be discarded if necessary. In addition to being a more accurate indentation method than atomic force microscopy, the localised dynamic mechanical properties of collagen were measured for the first time. These results demonstrate that this nanoindentation technique can serve as a powerful tool for the characterisation of collagen based biomaterials that are used as scaffolds for a variety of engineered tissues, such as artificial skin, skeletal muscle, heart valves and neuroregeneration guides.