Kinetics of the reaction of nitric oxide with hydrogen

Mixtures of NO and H2 diluted in argon or krypton were heated by incident shock waves, and the infrared emission from the fundamental vibration-rotation band of NO at 5.3 microns was used to monitor the time-varying NO concentration. The reaction kinetics were studied in the temperature range 2400-4500 K using a shock-tube technique. The decomposition of nitric oxide behind the shock was found to be modeled well by a fifteen-reaction system. A principle result of the study was the determination of the rate constant for the reaction H + NO yields N + OH, which may be the rate-limiting step for NO removal in some combustion systems. Experimental values of k sub 1 were obtained for each test through comparisons of measured and numerically predicted NO profiles

Decomposition of NO studied by infrared emission and CO laser absorption

A diagnostic technique for monitoring the concentration of NO using absorption of CO laser radiation was developed and applied in a study of the decomposition kinetics of NO. Simultaneous measurements of infrared emission by NO at 5.3 microns were also made to validate the laser absorption technique. The data were obtained behind incident shocks in NO-N2O-Ar (or Kr) mixtures, with temperatures in the range 2400-4100 K. Rate constants for dominant reactions were inferred from comparisons with computer simulations of the reactive flow

Rotational quenching of CO due to H2_2 collisions

Rate coefficients for state-to-state rotational transitions in CO induced by both para- and ortho-H$_2$ collisions are presented. The results were obtained using the close-coupling method and the coupled-states approximation, with the CO-H$_2$ interaction potential of Jankowski & Szalewicz (2005). Rate coefficients are presented for temperatures between 1 and 3000 K, and for CO($v=0,j$) quenching from $j=1-40$ to all lower $j^\prime$ levels. Comparisons with previous calculations using an earlier potential show some discrepancies, especially at low temperatures and for rotational transitions involving large $|\Delta j|$. The differences in the well depths of the van der Waals interactions in the two potential surfaces lead to different resonance structures in the energy dependence of the cross sections which influence the low temperature rate coefficients. Applications to far infrared observations of astrophysical environments are briefly discussed.Comment: 28 pages, 10 figure

Port Stanley Magnetic Observatory installation report 6 - 10 February 2003

This report describes the modifications made to the Port Stanley Geomagnetic Observatory during a visit to the Falkland Islands in February 2003. Since the report is intended as a technical reference for observatory operation, the instruments, computing equipment, software and cabling have been described in detail. The modifications were undertaken to ensure the continued supply of high quality geomagnetic data from this observatory, and to this end, there are some further recommendations for future visits listed in the final section of the report

H2_2D+^+ line emission in Proto-Planetary Disks

%Context: {Previous studies have indicated that the 372.4 GHz ground transition of ortho-H$_2$D$^+$ might be a powerful probe of Proto-Planetary Disks. The line could be especially suited for study of the disk mid-plane, where the bulk of the mass resides and where planet formation takes place.} %Aims: {Provide detailed theoretical predictions for the line intensity, profile and maps expected for representative disk models.} %Methods: {We determine the physical and chemical structure of the disks from the model developed by Ceccarelli & Dominik (2005). The line emission is computed with the new radiative transfer method developed recently by Elitzur & Asensio Ramos (2006).} %Results: {We present intensity maps convolved with the expected ALMA resolution, which delineate the origin of the H$_2$D$^+$ 372.4 GHz line. In the disk inner regions, the line probes the conditions in the mid-plane out to radial distances of a few tens of AU, where Solar-like planetary systems might form. In the disk outermost regions, the line originates from slightly above the mid-plane. When the disk is spatially resolved, the variation of line profile across the image provides important information about the velocity field. Spectral profiles of the entire disk flux show a double peak shape at most inclination angles.} %Conclusions: {Our study confirms that the 372.4 GHz H$_2$D$^+$ line provides powerful diagnostics of the mid-plane of Proto-Planetary Disks. Current submillimeter telescopes are capable of observing this line, though with some difficulties. The future ALMA interferometer will have the sensitivity to observe and even spatially resolve the H$_2$D$^+$ line emission.}Comment: To appear in A&

A Brush Seals Program Modeling and Developments

Some events of a US Army/NASA Lewis Research Center brush seals program are reviewed, and the development of ceramic brush seals is described. Some preliminary roomtemperature flow data are modeled and compare favorably to the results of Ergun

Therapeutic strategies for Huntington’s disease

PURPOSE AND REVIEW: Huntington's disease is a fatal autosomal dominant neurodegenerative disorder caused by a trinucleotide expansion in the HTT gene, and current therapies focus on symptomatic treatment. This review explores therapeutic approaches that directly target the pathogenic mutation, disrupt HTT mRNA or its translation. RECENT FINDINGS: Zinc-finger transcription repressors and CRISPR-Cas9 therapies target HTT DNA, thereby preventing all downstream pathogenic mechanisms. These therapies, together with RNA interference (RNAi), require intraparenchymal delivery to the brain in viral vectors, with only a single delivery potentially required, though they may carry the risk of irreversible side-effects. Along with RNAi, antisense oligonucleotides (ASOs) target mRNA, but are delivered periodically and intrathecally. ASOs have safely decreased mutant huntingtin protein (mHTT) levels in the central nervous system of patients, and a phase 3 clinical trial is currently underway. Finally, orally available small molecules, acting on splicing or posttranslational modification, have recently been shown to decrease mHTT in animal models. SUMMARY: Huntingtin-lowering approaches act upstream of pathogenic mechanisms and therefore have a high a priori likelihood of modifying disease course. ASOs are already in late-stage clinical development, whereas other strategies are progressing rapidly toward human studies

Water emission from the high-mass star-forming region IRAS 17233-3606. High water abundances at high velocities

We investigate the physical and chemical processes at work during the formation of a massive protostar based on the observation of water in an outflow from a very young object previously detected in H2 and SiO in the IRAS 17233-3606 region. We estimated the abundance of water to understand its chemistry, and to constrain the mass of the emitting outflow. We present new observations of shocked water obtained with the HIFI receiver onboard Herschel. We detected water at high velocities in a range similar to SiO. We self-consistently fitted these observations along with previous SiO data through a state-of-the-art, one-dimensional, stationary C-shock model. We found that a single model can explain the SiO and H2O emission in the red and blue wings of the spectra. Remarkably, one common area, similar to that found for H2 emission, fits both the SiO and H2O emission regions. This shock model subsequently allowed us to assess the shocked water column density, N(H2O)=1.2x10^{18} cm^{-2}, mass, M(H2O)=12.5 M_earth, and its maximum fractional abundance with respect to the total density, x(H2O)=1.4x10^{-4}. The corresponding water abundance in fractional column density units ranges between 2.5x10^{-5} and 1.2x10^{-5}, in agreement with recent results obtained in outflows from low- and high-mass young stellar objects.Comment: accepted for publication as a Letter in Astronomy and Astrophysic

The Great Eruption of Eta Carinae

During the years 1838-1858, the very massive star {\eta} Carinae became the prototype supernova impostor: it released nearly as much light as a supernova explosion and shed an impressive amount of mass, but survived as a star.1 Based on a light-echo spectrum of that event, Rest et al.2 conclude that "a new physical mechanism" is required to explain it, because the gas outflow appears cooler than theoretical expectations. Here we note that (1) theory predicted a substantially lower temperature than they quoted, and (2) their inferred observational value is quite uncertain. Therefore, analyses so far do not reveal any significant contradiction between the observed spectrum and most previous discussions of the Great Eruption and its physics.Comment: To appear in Nature, a brief communication arising in response to Rest et al. 2012. Submitted to Nature February 17, 201

Rovibrationally resolved photodissociation of HeH+

Accurate photodissociation cross sections have been obtained for the A-X electronic transition of HeH+ using ab initio potential curves and dipole transition moments. Partial cross sections have been evaluated for all rotational transitions from the vibrational levels v"=0-11 and over the entire accessible wavelength range 100-1129 Angstrom. Assuming a Boltzmann distribution of the rovibrational levels of the X state, photodissociation cross sections are presented for temperatures between 500 and 12,000 K. A similar set of calculations was performed for the pure rovibrational photodissociation in the X-X electronic ground state, but covering photon wavelengths into the far infrared. Applications of the cross sections to the destruction of HeH+in the early Universe and in UV-irradiated environments such as primordial halos and protoplanetary disks are briefly discussed