In this paper, a multi-pass retro-reflection-cavity-enhanced photoacoustic spectroscopy (PAS) based gas sensor is reported for the first time. The multi-pass retro-reflection-cavity consisted of two ...right-angle prisms and was designed to reflect the laser beam to pass through the photoacoustic (PA) cell four times, which improved the acetylene (C
H
)-PAS sensor signal level significantly. The optical power of a near-infrared distributed feedback (DFB) diode laser emitting a continuous wave (CW) was amplified to 1000 mW with an erbium-doped fiber amplifier. The background noise was reduced with wavelength modulation spectroscopy (WMS) and 2nd harmonic demodulation techniques. The linear optical power and concentration response of such a PAS sensor were investigated, and the experimental results showed excellent characteristics. When the integration the time of the sensor system was set to 1 s, the minimum detection limit (MDL) for C
H
detection was 8.17 ppb, which corresponds to a normalized noise equivalent absorption coefficient (NNEA) of 1.84 × 10
cm
W/√Hz. The long-term stability of such a multi-pass retro-reflection-cavity-enhanced PAS based C
H
sensor was evaluated by an Allan deviation analysis. It was demonstrated that the multi-pass retro-reflection-cavity-enhanced PAS sensor had an excellent stability. An MDL of 600 ppt was achieved when the integration time was set to ~1000 s. It was verified that the method of multi-pass retro-reflection-cavity-enhanced PAS with an amplified laser source improved the sensor performance significantly. If an appropriate cavity design with increasing reflection times is used, the MDL of such a PAS-based sensor can be further improved.
In this report, a sensitive quartz-enhanced photoacoustic spectroscopy (QEPAS) based hydrogen chloride (HCl) sensor using a quartz tuning fork (QTF) with a resonance frequency of 30.72kHz was ...demonstrated for the first time. A fiber-coupled, continuous wave (CW), distributed feedback (DFB) diode laser emitting at 1.74μm was employed as the excitation laser source. Wavelength modulation spectroscopy and a 2nd harmonic detection technique were used to reduce the sensor background noise. An acoustic micro-resonator (mR) was added to the QTF sensor architecture to improve the signal amplitude. For the reported HCl sensor system operating at atmospheric pressure, a 550 ppbv (parts per billion by volume) minimum detection limit at 5739.27cm−1 was achieved when the modulation depth and the data acquisition time were set to 0.23cm−1 and 1s, respectively. The ppb-level detection sensitivity and robust design of the QEPAS technique makes it suitable for use in environmental monitoring and other applications.
A multi-gas sensor system was developed that uses a single broadband light source and multiple carbon monoxide (CO), carbon dioxide (CO₂) and methane (CH₄) pyroelectric detectors by use of the time ...division multiplexing (TDM) technique. A stepper motor-based rotating system and a single-reflection spherical optical mirror were designed and adopted to realize and enhance multi-gas detection. Detailed measurements under static detection mode (without rotation) and dynamic mode (with rotation) were performed to study the performance of the sensor system for the three gas species. Effects of the motor rotating period on sensor performances were also investigated and a rotation speed of 0.4π rad/s was required to obtain a stable sensing performance, corresponding to a detection period of ~10 s to realize one round of detection. Based on an Allan deviation analysis, the 1
detection limits under static operation are 2.96, 4.54 and 2.84 parts per million in volume (ppmv) for CO, CO₂ and CH₄, respectively and the 1
detection limits under dynamic operations are 8.83, 8.69 and 10.29 ppmv for the three gas species, respectively. The reported sensor has potential applications in various fields requiring CO, CO₂ and CH₄ detection such as in coal mines.
A multi-quartz-enhanced photothermal spectroscopy (M-QEPTS) based trace gas detection method is reported for the first time. Different from traditional QEPTS sensor employing a single quartz tuning ...fork (QTF) as a photothermal detector, two QTFs were used in M-QEPTS to increase the signal amplitude by adding the generated piezoelectric signals. The coating film of the QTFs was removed in order to improve the laser absorption and transmission. Acetylene (C2H2) was chosen as the target analyte. Wavelength modulation spectroscopy (WMS) and 2nd harmonic detection were utilized for the concentration detection. Limit of detection (LoD) of 0.97 ppm was achieved with a 1 second integration time for the M-QEPTS sensor, which realized a 1.51 times signal enhancement compared to a traditional QEPTS sensor employing a single QTF. By using an Allan deviation analysis approach, LoD of 0.19 ppm for an optimum integration time of 200 s was obtained.
Natural materials are highly anisotropic, maximizing performance of the polymeric structures while conserving mass and enhancing function. In synthetic materials, nanoscale fibers produced by ...electrospinning often contain molecular alignment of polymers along the fiber axis achieving some similarity to natural fibers. In this study, isolated softwood kraft lignin (SKL) was electrospun into aligned fibers utilizing a special collector. The molecular organization of lignin within the aligned nanofibers was investigated by polarized light optical microscopy. Furthermore, the functional groups that had preferred alignment along the fiber axis were identified with polarized Fourier transform infrared (FTIR) spectroscopy based on dichroism measurements. In addition, nanocrystalline cellulose (NCC) was added to the lignin solutions in order to create composite nanofibers. Both the orientation of NCC within the nanoscale fibers and the impact this component had on the degree of orientation of SKL within the aligned nanofibers were revealed by utilizing polarized FTIR. Finally, solvent cast lignin films were analyzed for their anisotropic polarizability, demonstrating birefringence with and without nanocrystalline cellulose. The work provided unique insight into both preferred orientation (fibers) and assembly (films) for technical lignin due to processing.
A compact and sensitive quartz-enhanced photoacoustic spectroscopy (QEPAS) based sensor for carbon monoxide (CO) detection was demonstrated by using a mid-infrared all-fiber structure as well as a ...3D-printed acoustic detection module. An all-fiber configuration has advantages of easier optical alignment, lower insertion loss, improvement in system stability, reduction in sensor size and lower cost. The 3D-printed acoustic detection module was introduced to match the mid-infrared all-fiber structure and further decrease the sensor volume, which resulted in a small size of 3.5 cm
and a weight of 5 grams. A 2.33 μm distributed feedback fiber-coupled diode laser was used as the laser excitation source. A custom quartz tuning fork (QTF) with a small-gap of 200 μm was used as the acoustic wave transducer in order to improve the signal level of the QEPAS sensor. An acoustic micro resonator was utilized as the acoustic wave enhancer. The gas pressure and laser wavelength modulation depth were optimized, respectively. Water vapor was used to accelerate the vibrational-translational relaxation rate of the targeted CO molecule. Finally, a minimum detection limit (MDL) of 4.2 part per million (ppm) was achieved, corresponding to a normalized noise equivalent absorption (NNEA) coefficient of 7.4 × 10
cm
W/√Hz. An Allan deviation analysis was used to evaluate the long-term stability of the reported CO-QEPAS sensor system. With an integration time of 150 s, the MDL was improved to be 1.3 ppm.
This book describes and explains the methods by which three related ores and recyclables are made into high purity metals and chemicals, for materials processing. It focuses on present day processes ...and future developments rather than historical processes. Nickel, cobalt and platinum group metals are key elements for materials processing. They occur together in one book because they (i) map together on the periodic table (ii) occur together in many ores and (iii) are natural partners for further materials processing and materials manufacturing. They all are, for example, important catalysts with platinum group metals being especially important for reducing car and truck emissions. Stainless steels and CoNiFe airplane engine super alloys are examples of practical usage. The book emphasizes a sequential, building-block approach to the subject gained through the author’s previous writings and extensive experience. Due to the multiple metals involved and because each metal originates in several types of ore, e.g. tropical ores and arctic ores, this necessitates a multi-contributor work drawing from multiple networks and both engineering and science.
The cysteinyl leukotrienes (cys-LTs), leukotriene C4 (LTC4), a conjugation product of glutathione and eicosatetraenoic acid, and its metabolites, LTD4 and LTE4, are lipid mediators of smooth muscle ...constriction and inflammation in asthma. LTD4 is the most potent ligand for the type 1 cys-LT receptor (CysLT1R), and LTC4 and LTD4 have similar lesser potency for CysLT2R, whereas LTE4 has little potency for either receptor. Cysltr1/Cysltr2−/− mice, lacking the two defined receptors, exhibited a comparable dose-dependent vascular leak to intradermal injection of LTC4 or LTD4 and an augmented response to LTE4 as compared with WT mice. As LTE4 retains a cysteine residue and might provide recognition via a dicarboxylic acid structure, we screened cDNAs within the P2Y nucleotide receptor family containing CysLTRs and dicarboxylic acid receptors with trans-activator reporter gene assays. GPR99, previously described as an oxoglutarate receptor (Oxgr1), showed both a functional and a binding response to LTE4 in these transfectants. We generated Gpr99−/− and Gpr99/Cysltr1/Cysltr2−/− mice for comparison with WT and Cysltr1/Cysltr2−/− mice. Strikingly, GPR99 deficiency in the Cysltr1/Cysltr2−/− mice virtually eliminated the vascular leak in response to the cys-LT ligands, indicating GPR99 as a potential CysLT3R active in the Cysltr1/Cysltr2−/− mice. Importantly, the Gpr99−/− mice showed a dose-dependent loss of LTE4-mediated vascular permeability, but not to LTC4 or LTD4, revealing a preference of GPR99 for LTE4 even when CysLT1R is present. As LTE4 is the predominant cys-LT species in inflamed tissues, GPR99 may provide a new therapeutic target.
Background: A most stable cysteinyl leukotriene, LTE4, mediates vascular permeability in mice lacking the two known receptors.
Results: GPR99 deficiency abolishes LTE4-induced vascular permeability in mice also lacking the two known receptors.
Conclusion: GPR99 is a potential third cysteinyl leukotriene receptor.
Significance: GPR99 may be a therapeutic target for inflammatory diseases.
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