Phase-sensitive optical coherence tomography at up to 370,000 lines per second using buffered Fourier domain mode-locked lasers

Buffered Fourier domain mode-locked (FDML) lasers are demonstrated for dynamic phase-sensitive optical coherence tomography (OCT) and 3D OCT phase microscopy. Systems are operated at sweep speeds of 42, 117, and 370 kHz, and displacement sensitivities of 39, 52, and 102 pm are achieved, respectively. Sensitivities are comparable to spectrometer-based OCT phase microscopy systems, but much faster acquisition speeds are possible. An additional factor of sqrt 2 improvement in noise performance is observed for differential phase measurements, which is important for Doppler OCT. Dynamic measurements of piezoelectric transducer motion and static 3D OCT phase microscopy are demonstrated. Buffered FDML lasers provide excellent displacement sensitivities at extremely high sweep speeds.     

Dual colorimetric and electrochemical sensing of organothiophosphorus pesticides by an azastilbene derivative

We have investigated the optical and electrochemical changes of the azastilbene, dimethyl-[4-(2-quinolin-2-yl-vinyl)-phenyl]-amine (DQA), with four organothiophosphorus (OTP) pesticides: ethion, malathion, parathion, and fenthion. Significant changes in UV-visible absorbance wavelength and in electrochemical signals indicate the effectiveness of DQA as an OTP sensor.     

Biochemistry of human skin--our brain on the outside

The skin, our body's largest organ, is located at the interface between the external and internal environments, and so is strategically placed to provide not only a barrier against a range of noxious stressors (UV radiation, mechanical, chemical and biological insults) but also to act as the periphery's 'sensing' system. Recent developments suggest that this organ is much more critical to maintaining body homeostasis than previously thought. This tutorial review introduces the reader to some of the biochemistry that underpins the skin's enormous multi-functionality.     

Buffered Fourier domain mode locking: Unidirectional swept laser sources for optical coherence tomography imaging at 370,000 lines/s

We describe buffered Fourier domain mode locking (FDML), a technique for tailoring the output and multiplying the sweep rate of FDML lasers. Buffered FDML can be used to create unidirectional wavelength sweeps from the normal bidirectional sweeps in an FDML laser without sacrificing sweep rate. We also investigate the role of the laser source in dynamic range versus sensitivity performance in optical coherence tomography (OCT) imaging. Unidirectional sweep rates of 370 kHz over a 100 nm range at a center wavelength of 1300 nm are achieved. High-speed, swept-source OCT is demonstrated at record speeds of up to 370,000 axial scans per second.     

High-throughput bioanalysis with simultaneous acquisition of metabolic route data using ultra performance liquid chromatography coupled with time-of-flight mass spectrometry

The capability of ultra performance liquid chromatography coupled with time-of-flight mass spectrometry (UPLC/TOFMS) in the high-throughput quantitative analysis of a drug candidate in plasma has been investigated. Data obtained were compared with results from conventional analysis by high-performance liquid chromatography with tandem mass spectrometric detection on a triple quadrupole instrument (HPLC/MS/MS). The accuracies and precisions of the two approaches were comparable. The UPLC/TOFMS system displayed excellent robustness over the course of 276 injections of protein-precipitated plasma samples. With the instrumentation used, the limits of detection and quantification were approximately five-fold higher with UPLC/TOFMS than for HPLC/MS/MS. Nevertheless, the UPLC/TOFMS system proved adequate to quantify plasma concentrations of a drug molecule administered orally to rats at a pharmacologically relevant dose of 4 mg/kg. As well as providing quantitative data on the test compound, it was also possible to extract data for eight different metabolites, including several isomeric species (three +O and three +2O) from the UPLC/TOFMS data sets, using an analytical method with a 2.5-minute run time. Selectivity for the test compound and its metabolites was derived from the accurate mass capabilities of the TOF instrument, and no MS method development was required.     

Weak correction to the muon magnetic moment in a gauge model

The weak correction, a_μ^w, to the anomalous magnetic moment of the muon is calculated in an SU(2) ? U(1) ? U(1) gauge model of weak and electromagnetic interactions. The R_ξ gauge is used and Ward-Takahashi indentities are utilized eliminating all ξ-dependence before the loop integration is performed. a_μ^w,expt places no constraint on the mass of one of the neutral vector mesons, which may be arbitrarily small.     

The Structure of Pyroergotamine

The molecular structure of pyroergotamine has been determined by single-crystal X-ray diffraction analysis to be the pyruvoyldiketopiperazine 1 . The diketopiperazine ring exists in a folded or boat conformation, with a dihedral angle of 40° between the two almost planar peptide units. The R-group of the phenylalanine residue occupies a quasi-axial position of the diketopiperazine ring, while that of the proline residue is in a quasi-equatorial position. Puzzling spectroscopic and chemical properties of the compound can be rationalised in terms of crowding within the molecule.     

'All-in-one' analysis for metabolite identification using liquid chromatography/hybrid quadrupole time-of-flight mass spectrometry with collision energy switching

The removal of bottlenecks in discovery stage metabolite identification studies is an ongoing challenge for the pharmaceutical industry. We describe the use of an 'All-in-One' approach to metabolite characterization that leverages the fast scanning and high mass accuracy of hybrid quadrupole time-of-flight mass spectrometry (QqToFMS) instruments. Full-scan MS and MS/MS data is acquired using collision energy switching without the preselection, either manually or in a data-dependent manner, of precursor ions. The acquisition of 'clean' MS/MS data is assisted by the use of ultrahigh-performance chromatography. Data acquired using this method can then be mined post-acquisition in a number of ways. These include using narrow window extracted ion chromatograms (nwXICs) for expected biotransformations, XICs for the product ions of the parent compound and/or expected modification of these product ions, and neutral loss chromatograms. This approach has the potential to be truly comprehensive for the determination of in vitro biotransformations in a drug discovery environment.