Development of a Carbon Mesh Supported Thin Film Microextraction Membrane As a Means to Lower the Detection Limits of Benchtop and Portable GC/MS Instrumentation

This document is the Accepted Manuscript version of a Published Work that appeared in final form in Analytical Chemistry, copyright © American Chemical Society after peer review and technical editing by the publisher. To access the final edited and published work see http://pubs.acs.org/doi/abs/10.1021/acs.analchem.5b04008.In this work, a durable and easy to handle thin film microextraction (TFME) device is reported. The membrane is comprised of poly(divinylbenzene) (DVB) resin particles suspended in a high-density polydimethylsiloxane (PDMS) glue, which is spread onto a carbon fiber mesh. The currently presented membrane was shown to exhibit a substantially lesser amount of siloxane bleed during thermal desorption, while providing a statistically similar extraction efficiency toward a broad spectrum of analytes varying in polarity when compared to an unsupported DVB/PDMS membrane of similar shape and size which was prepared with previously published methods. With the use of hand-portable GC-TMS instrumentation, membranes cut with dimensions 40 mm long by 4.85 mm wide and 40 ± 5 μm thick (per side) were shown to extract 21.2, 19.8, 18.5, 18,4, 26.8, and 23.7 times the amount of 2,4 dichlorophenol, 2,4,6 trichlorophenol, phorate D10, fonofos, chloropyrifos, and parathion, respectively, within 15 min from a 10 ppb aqueous solution as compared to a 65 μm DVB/PDMS solid phase microextraction (SPME) fiber. A portable high volume desorption module prototype was also evaluated and shown to be appropriate for the desorption of analytes with a volatility equal to or lesser than benzene when employed in conjunction with TFME membranes. Indeed, the coupling of these TFME devices to hand-portable gas chromatography toroidial ion trap mass spectrometry (GC-TMS) instrumentation was shown to push detection limits for these pesticides down to the hundreds of ppt levels, nearing that which can be achieved with benchtop instrumentation. Where these membranes can also be coupled to benchtop instrumentation it is reasonable to assume that detection limits could be pushed down even further. As a final proof of the concept, the first ever, entirely on-site TFME-GC-TMS analysis was performed at a construction impacted lake. Results had indicated the presence of contaminants such as toluene, ethylbenzene, xylene, 2,2,4-trimethyl-1,3-pentanediol diisobutyrate, and tris(1-chloro-2-propyl)phosphate, which stood out from other naturally occurring compounds detected.the Natural Sciences and Engineering Research Council of Canada (NSERC

Lack of association between dual antiplatelet therapy use and stent thrombosis between 1 and 12 months following resolute zotarolimus-eluting stent implantation

Aim The optimal duration of dual antiplatelet therapy (DAPT) following the use of new generation drug-eluting stents is unknown. Methods and results The association between DAPT interruption and the rates of stent thrombosis (ST) and cardiac death/target-vessel myocardial infarction (CD/TVMI) in patients receiving a Resolute zotarolimus-eluting stent (R-ZES) was analysed in 4896 patients from the pooled RESOLUTE clinical programme. Daily acetylsalicylate (ASA) and a thienopyridine for 6-12 months were prescribed. A DAPT interruption was defined as any interruption of ASA and/or a thienopyridine of >1 day; long interruptions were >14 days. Three groups were analysed: no interruption, interruption during the first month, and >1-12 months. There were 1069 (21.83%) patients with a DAPT interruption and 3827 patients with no interruption. Among the 166 patients in the 1-month interruption group, 6 definite/probable ST events occurred (3.61%; all long DAPT interruptions), and among the 903 patients in the >1-12 months (60% occurred between 6 and 12 months) interruption group, 1 ST event occurred (0.11%; 2-day DAPT interruption). Among patients with no DAPT interruption, 32 ST events occurred (0.84%). Rates of CD/TVMI were 6.84% in the 1-month long interruption group, 1.41% in the >1-12 months long interruption group, and 4.08% in patients on continuous DAPT. Conclusion In a pooled population of patients receiving an R-ZES, DAPT interruptions within 1 month are associated with a high risk of adverse outcomes. Dual antiplatelet therapy interruptions between 1 and 12 months were associated with low rates of ST and adverse cardiac outcomes. Randomized clinical trials are needed to determine whether early temporary or permanent interruption of DAPT is truly safe. Clinical Trials.gov identifiers NCT00617084; NCT00726453; NCT00752128; NCT0092794

WD1032+011, an inflated brown dwarf in an old eclipsing binary with a white dwarf

We present the discovery of only the third brown dwarf known to eclipse a non-accreting white dwarf. Gaia parallax information and multicolour photometry confirm that the white dwarf is cool (9950 ± 150 K) and has a low mass (0.45 ± 0.05 M⊙), and spectra and light curves suggest the brown dwarf has a mass of 0.067 ± 0.006 M⊙ (70MJup) and a spectral type of L5 ± 1. The kinematics of the system show that the binary is likely to be a member of the thick disc and therefore at least 5-Gyr old. The high-cadence light curves show that the brown dwarf is inflated, making it the first brown dwarf in an eclipsing white dwarf-brown dwarf binary to be so

Advances in high power short pulse fiber laser systems and technology

We review recent advances in Yb fiber lasers and amplifiers for high power short pulse systems. We go on to describe associated recent developments in fiber components for use in such systems. Examples include microstructured optical fibers for pulse compression and supercontinuum generation, and advanced fiber grating technology for chirped-pulse amplifier systems

Synchronously pumped mid-IR hollow core fiber gas laser

We report a synchronously pumped 3.16 μm acetylene fiber laser based entirely on low-loss silica hollow-core fiber. Our system oscillates at 2.568 MHz repetition rate, when pumped with a modulated amplified 1.53 μm diode laser.</p

Physical limits of flight performance in the heaviest soaring bird

Flight costs are predicted to vary with environmental conditions, and this should ultimately determine the movement capacity and distributions of large soaring birds. Despite this, little is known about how flight effort varies with environmental parameters. We deployed bio-logging devices on the world’s heaviest soaring bird, the Andean condor (Vultur gryphus), to assess the extent to which these birds can operate without resorting to powered flight. Our records of individual wingbeats in >216 hours of flight show that condors can sustain soaring across a wide range of wind and thermal conditions, only flapping for 1 % of their flight time. This is amongst the very lowest estimated movement costs in vertebrates. One bird even flew for > 5 hours without flapping, covering ~ 172 km. Overall, > 70 % of flapping flight was associated with take-offs. Movement between weak thermal updrafts at the start of the day also imposed a metabolic cost, with birds flapping towards the end of glides to reach ephemeral thermal updrafts. Nonetheless, the investment required was still remarkably low, and even in winter conditions with weak thermals, condors are only predicted to flap for ~ 2 s per km. The overall flight effort in the largest soaring birds therefore appears to be constrained by the requirements for take-off

Multiwavelength observations of the EUV variable metal-rich white dwarf GD 394

We present new Hubble Space Telescope (HST) ultraviolet and ground-based optical observations of the hot, metal-rich white dwarf GD394. Extreme-ultraviolet (EUV) observations in 1992-1996 revealed a 1.15 d periodicity with a 25 per cent amplitude, hypothesized to be due to metals in a surface accretion spot. We obtained phase resolved HST/Space Telescope Imaging Spectrograph high resolution far-ultraviolet spectra of GD394 that sample the entire period, along with a large body of supplementary data. We find no evidence for an accretion spot, with the flux, accretion rate, and radial velocity of GD394 constant over the observed time-scales at ultraviolet and optical wavelengths. We speculate that the spot may have no longer been present when our observations were obtained, or that the EUV variability is being caused by an otherwise undetected evaporating planet. The atmospheric parameters obtained from separate fits to optical and ultraviolet spectra are inconsistent, as is found for multiple hot white dwarfs. We also detect non-photospheric, high ionisation absorption lines of multiple volatile elements, which could be evidence for a hot plasma cocoon surrounding the white dwarf.European Research Council under the European Union's Seventh Framework Programme (FP/2007-2013 / ERC Grant) [320964]; Leverhulme Trust Research Project Grant; NASA [NAS 5-26555]; NASA through a Space Telescope Science Institute [13719]; W. M. Keck FoundationThis item from the UA Faculty Publications collection is made available by the University of Arizona with support from the University of Arizona Libraries. If you have questions, please contact us at [email protected]