Impact of water vapor on 1.51 μm ammonia absorption features used in trace gas sensing applications

Water-vapor-induced pressure broadening is reported for two NH3 absorption features at 6612.7 and 6596.4cm−1 that are exploitable for gas sensing applications at atmospheric pressure. Absorption spectra of different NH3-H2O-N2 mixtures were measured at an elevated temperature of 70°C to enable high H2O concentrations to be reached. Line parameters were determined from a fitting procedure. The significantly greater values obtained for the H2O-broadening coefficients of the two lines compared to N2-broadening leads to cross-sensitivity effects in NH3 trace gas sensors based on spectroscopic techniques that are sensitive to the width of the analyzed absorption line, as is the case in a simple implementation of wavelength modulation spectroscopy or in photoacoustic spectroscopy. In such a case, cross-sensitivity results in inaccurate gas concentration retrieval when the composition of the diluting gas changes. H2O represents a potentially significant cross-sensitivity source as its concentration may be subject to large variations, especially in high-temperature applications where concentrations up to a couple of tens of percent may be encountered. In contrast to interference which can be minimized by an appropriate choice of the analyzed transitions, cross-sensitivity affects the entire spectrum of the analyte and is thus unavoidable in the mentioned type of gas sensor

Prognostic value of bronchoalveolar lavage fluid CD103+CD4+/CD4+ ratio in sarcoidosis

The CD103+ integrin is an adhesion molecule found on > 95% of intra-epithelial mucosal lymphocytes, but on <2% of circulating lymphocytes. Several studies have shown that the proportion of CD4+ lymphocytes expressing the CD103+ integrin (CD103+CD4+/CD4+ ratio) in bronchoalveolar lavage fluid (BALF) was low in sarcoidosis compared to other interstitial lung diseases, but we previously demonstrated that the difference was insufficient to allow a confident diagnosis of sarcoidosis without tissue biopsy. Whether BALF CD103+CD4+/CD4+ ratio could have prognostic value in sarcoidosis is unknown. To address this issue, we examined the associations between BALF CD103+CD4+/CD4+ ratio and clinical and imaging characteristics in a retrospective series of 115 patients with sarcoidosis. 63% were men, with a median age of 48 years. 47% had radiographic stage I, 49% had stage II, and 4% had stage III or IV. The median BALF lymphocyte count was 43% and the median CD103+CD4+/CD4+ ratio was 17%. A higher CD103+CD4+/CD4+ ratio was significantly associated with a higher radiographic stage at diagnosis (p=0.017) and last visit (p<0.0001), as well as the presence of fibrosis at imaging at diagnosis (p=0.043) and last visit (p=0.032). Besides an inverse correlation with forced vital capacity at diagnosis (β=-0.16, p=0.031), no consistent association was found between the BALF CD103+CD4+/CD4+ ratio at diagnosis and lung function parameters at diagnosis and last visit. We conclude that BALF CD103+CD4+/CD4+ ratio may have prognostic value in sarcoidosis

Self-mixing interference effects in tunable diode laser absorption spectroscopy

We report the effects of self-mixing interference on gas detection using tunable diode laser spectroscopy. For very weak feedback, the laser diode output intensity gains a sinusoidal modulation analogous to that caused by low finesse etalons in the optical path. Our experiments show that self-mixing interference can arise from both specular reflections (e.g. cell windows) and diffuse reflections (e.g. Spectralon™ and retroreflective tape), potentially in a wider range of circumstances than etalon-induced interference. The form and magnitude of the modulation is shown to agree with theory. We have quantified the effect of these spurious signals on methane detection using wavelength modulation spectroscopy and discuss the implications for real gas detecto

Steeple Echoes - Revival - Aug 29 1983 - Gene Watterson

Flyer and publicity notes for West Asheville Baptist Church\u27s Old Fashioned Revival, featuring Gene L. Watterson.https://digitalcommons.gardner-webb.edu/first-baptist-shelby-gene-watterson/1041/thumbnail.jp

Carrier-Envelope Offset Stabilized Ultrafast Diode-Pumped Solid-State Lasers

Optical frequency combs have been revolutionizing many research areas and are finding a growing number of real-world applications. While initially dominated by Ti:Sapphire and fiber lasers, optical frequency combs from modelocked diode-pumped solid-state lasers (DPSSLs) have become an attractive alternative with state-of-the-art performance. In this article, we review the main achievements in ultrafast DPSSLs for frequency combs. We present the current status of carrier-envelope offset (CEO) frequency-stabilized DPSSLs based on various approaches and operating in different wavelength regimes. Feedback to the pump current provides a reliable scheme for frequency comb CEO stabilization, but also other methods with faster feedback not limited by the lifetime of the gain material have been applied. Pumping DPSSLs with high power multi-transverse-mode diodes enabled a new class of high power oscillators and gigahertz repetition rate lasers, which were initially not believed to be suitable for CEO stabilization due to the pump noise. However, this challenge has been overcome, and recently both high power and gigahertz DPSSL combs have been demonstrated. Thin disk lasers have demonstrated the highest pulse energy and average power emitted from any ultrafast oscillator and present a high potential for the future generation of stabilized frequency combs with hundreds of watts average output power

Cross-reactions of immunoglobulin M and G antibodies with enterovirus-specific viral structural proteins

We analysed the reactivity of enterovirus-specific human IgM and IgG antibodies with the structural proteins of different enteroviruses by the immunoblot technique. In general, all immunoglobulin G antibodies of the tested sera reacted with capsid polypeptide VP 1 of the viruses tested (echoviruses 9 and 11, coxsackievirus B3 and poliovirus 2). In contrast, enterovirus specific immunoglobulin M antibodies of adults reacted with capsid polypeptides VP 1, VP 2, and/or VP 3 of the viruses mentioned above. The reactions with VP 2 and/or VP 3 were often stronger than with VP 1. IgM antibodies from sera of newborns infected by echovirus 11 reacted with VP 1 and VP 2/3 of echovirus 11 and also with VP 2 and VP 3 of poliovirus 2. Preabsorption experiments indicate that cross-reactive IgG antibodies react with epitopes of VP 1 not present on the surface of intact virus particles. The results from the immunoblot technique were compared to data from microneutralization tests and M-antibody capture radioimmunoassay

Molecular relaxation effects in hydrogen chloride photoacoustic detection

A photoacoustic (PA) sensor has been developed to monitor hydrogen chloride at sub-ppm level in the 1740-nm region. The system was designed to control the process in the novel low-water-peak optical fiber manufacturing process. Relaxation effects in hydrogen chloride PA detection in oxygen-helium and nitrogen-helium gas mixtures are presented, showing that the generation of the PA signal is strongly affected by the ratio of these substances. In addition, the role of water vapor in the PA signal is investigate