Absolute diode laser-based in situ detection of HCl in gasification processes

The release of HCl is an important parameter for industrial combustion and gasification processes, which must be determined in the ppm range for active process control and optimization. Based on a low power vertical-cavity surface-emitting laser (VCSEL) at 1.74 μm, we developed a new tuneable diode laser absorption spectrometer for calibration-free, absolute in situ HCl detection using the H³⁵Cl (2 ← 0) R(3) absorption line with minimized cross-sensitivity to CO₂ and H₂O. The spectrometer was applied to in situ measurements in a gasification process (T = 1,130°C, P = 1 atm, L = 28 cm) and yielded an optical resolution of 2.3·10⁻⁴, i.e. a HCl sensitivity of 45 ppm (13 ppm·m).     

Synthetic compound libraries displayed on the surface of encoded bacteriophage

We describe a technology for attaching libraries of synthetic compounds to coat proteins of bacteriophage particles such that the identity of the chemical structure is encoded in the genome of the phage, analogous to peptides displayed on phage surfaces by conventional phage-display techniques. This format allows a library of synthetic compounds to be screened very efficiently as a single pool. Encoded phage serve as extremely robust reporters of the presence of each compound, providing exquisite sensitivity for identification of active compounds engaged in complex biological processes such as receptor-mediated endocytosis and transcytosis. To evaluate this approach, we constructed a library of 980 analogs of folic acid displayed on T7 phage, and demonstrated rapid identification of compounds that bind to folate receptor and direct endocytosis of associated phage particles into cells that express the targeted receptor.     

Laser-based measurements of line strength, self- and pressure-broadening coefficients of the H35Cl R(3) absorption line in the first overtone region for pressures up to 1 MPa

A high-resolution spectrometer based on a vertical-cavity surface-emitting laser (VCSEL) was developed and used to determine the line strength S(T ₀)=12.53(11)×10⁻²¹ cm⁻¹/(molec cm⁻²) and the self-broadening coefficient g⁰_HCl=0.021787(61)\gamma^{0}_{\mathrm{HCl}}=0.021787(61)  cm⁻¹/atm of the R(3) absorption line in the first rovibrational overtone (2←0) band of H³⁵Cl. Furthermore, the first laser-based high-pressure study on the pressure broadening of HCl by He, N₂ and O₂(g⁰_N2=0.07292(5)\mathrm{O}_{2}(\gamma^{0}_{\mathrm{N}_{2}}=0.07292(5)  cm⁻¹/atm, g⁰_He=0.02113(1)\gamma^{0}_{\mathrm{He}}=0.02113(1)  cm⁻¹/atm, g⁰_O2=0.03978(6)\gamma^{0}_{\mathrm{O}_{2}}=0.03978(6)  cm⁻¹/atm) is presented covering pressures of up to 1 MPa. The results are compared to previously available low-pressure data.     

Mass spectrometry of hyper‐velocity impacts of organic micrograins

The study of hyper‐velocity impacts of micrometeoroids is important for the calibration of dust sensors in space applications. For this purpose, submicron‐sized synthetic dust grains comprising either polystyrene or poly[bis(4‐vinylthiophenyl)sulfide] were coated with an ultrathin overlayer of an electrically conductive organic polymer (either polypyrrole or polyaniline) and were accelerated to speeds between 3 and 35 km s^?1 using the Heidelberg Dust Accelerator facility. Time‐of‐flight mass spectrometry was applied to analyse the resulting ionic impact plasma using a newly developed Large Area Mass Analyser (LAMA). Depending on the projectile type and the impact speed, both aliphatic and aromatic molecular ions and cluster species were identified in the mass spectra with masses up to 400 u. Clusters resulting from the target material (silver) and mixed clusters of target and projectile species were also observed. Impact velocities of between 10 and 35 km s^?1 are suitable for a principal identification of organic materials in micrometeoroids, whereas impact speeds below ～10 km s^?1 allow for an even more detailed analysis. Molecular ions and fragments reflect components of the parent molecule, providing determination of even complex organic molecules embedded in a dust grain. In contrast to previous measurements with the Cosmic Dust Analyser instrument, the employed LAMA instrument has a seven times higher mass resolution – approximately 200 – which allowed for a detailed analysis of the complex mass spectra. These fundamental studies are expected to enhance our understanding of cometary, interplanetary and interstellar dust grains, which travel at similar hyper‐velocities and are known to contain both aliphatic and aromatic organic compounds. Copyright © 2009 John Wiley & Sons, Ltd.     

Analysis of the non-periodic oscillations of a self-excited friction-damped system with closely spaced modes

Nonlinear Dynamics - It is widely known that dry friction damping can bound the self-excited vibrations induced by negative damping. The vibrations typically take the form of (periodic) limit cycle...