Rate coefficients for rovibrational transitions in H_2 due to collisions with He

We present quantum mechanical and quasiclassical trajectory calculations of cross sections for rovibrational transitions in ortho- and para-H_2 induced by collisions with He atoms. Cross sections were obtained for kinetic energies between 10^-4 and 3 eV, and the corresponding rate coefficients were calculated for the temperature range 100<T<4000 K. Comparisons are made with previous calculations.Comment: 21 pages, 2 figures, AAS, eps

Effect of Grain Size and Preferred Crystal Texture on Acoustic Properties of 304 Stainless Steel

Several acoustic properties have been measured in an annealed round rolled bar of type 304 stainless steel. These properties were observed to depend upon both microstructure and the non-random crystal texture of this single phase, polycrystalline, face-centered cubic alloy. All measurements were made with longitudinal waves propagating parallel to the bar axis. The acoustic velocity was observed to be 0.3% higher near the outer surface than along the center of the bar, consistent with a stronger [111] texture in the outer fibers than at the center. The attenuation coefficient at the center was twice as large as at the outer surface. The measured difference in grain size at the center and surface was consistent with the observed attenuation difference. The acousto-elastic coefficient measured for a uniaxial tension stress applied along a bar diameter was at least 20% higher at the bar center than at its outer surface

Polypyrrole grafts with poly[(methyl methacrylate)-CO-(2-(N-pyrrolyl)ethyl methacrylate)]

Cataloged from PDF version of article.Conducting polymer grafts of pyrrole and poly[(methyl methacrylate)-co-(2- (N-pyrrolyl) ethyl methacrylate)] containing 0.7% PEMA units were prepared by potentiostatic anodic polymerization of pyrrole in different electrolytic media. Grafting between copolymer and pyrrole was achieved in media where tetrabutylammonium fluoroborate and sodium perchlorate were used as the supporting electrolytes. Characterizations were made by using IT-IR, DSC, TGA, SEM, CV, and elemental analysis. The conductivities of the resultant polymers seemed to be in the order of pure polypyrrole prepared under the same conditions. Copyright o 1997 Elsevier Scienc

A mid-IR survey of the L 1641-N region with ISOCAM

We present an analysis of the L 1641 outflow region using broad-band and narrow-band imaging data at mid-infrared wavelengths from ISOCAM. We detect a total of 34 sources in the $7.65^{\prime}$ x $8.40^{\prime}$ region covered by the broad-band filters. Four of these sources have no reported detection in previous studies of the region. We find that the source previously identified as the near-IR counter-part to the IRAS detected point-source (IRAS 05338-0624) is not the brightest source in the wavelength region of the IRAS 12 \micron\ filter. We find instead that a nearby object (within the beam of IRAS and not detected at near-IR wavelengths) outshines all others sources in the area by a factor of $\sim$2. We submit that this source is likely to be the IRAS detected point source. A comparison of the near-IR (J-H vs H-K) and mid-IR (J-K vs [6.7 um]-[14 um]) color-color plots shows only four sources with excess emission at near-IR wavelengths, but atleast 85% of all sources show excess emission at mid-IR wavelengths. The CVF spectra suggest a range of evolutionary status in the program stars ranging from embedded YSOs to the young disks. When combined with optical and near-IR age estimates, these results show active current star-formation in the region that has been on-going for at least 2 Myr.Comment: Submitted to ApJ. Abstracted edited for arXiv submission Replaced by version accepted by Ap

Acoustic Measurement of Microstructures in Steels

The measurement of acoustic properties can be used for the nondestructive characterization of the microstructure of materials. We have measured the changes in longitudinal acoustic wave velocity and acoustic attenuation in steel specimens whose microstructure and properties differ widely because of differing compositions and heat treatment. The spatial variation of the relative acoustic velocity in standard Jominy end-quench hardenability test specimens was found to correlate very well with Rockwell C hardness scans, indicating a potentially practical method for measuring the hardening response of heat treated steel. Absolute velocity measurements on steel specimens were found to be subject to random scatter related to minor compositional variations; this limits the utility of absolute velocity measurements for microstructural NDE. Attenuation measurements have also been performed on steel samples with different microstructures. The measurement utilized broadband acoustic pulses corrected for transducer response, liquid buffer/solid specimen reflection, and diffraction effects. Attenuation coefficients were seen to be proportional to frequency squared for martensite and to the fourth power of frequency for pearlite. Higher attenuation was observed for pearlitic than for martensitic microstructures

Herschel/PACS Imaging of Protostars in the HH 1-2 Outflow Complex

We present 70 and 160 micron Herschel science demonstration images of a field in the Orion A molecular cloud that contains the prototypical Herbig-Haro objects HH 1 and 2, obtained with the Photodetector Array Camera and Spectrometer (PACS). These observations demonstrate Herschel's unprecedented ability to study the rich population of protostars in the Orion molecular clouds at the wavelengths where they emit most of their luminosity. The four protostars previously identified by Spitzer 3.6-40 micron imaging and spectroscopy are detected in the 70 micron band, and three are clearly detected at 160 microns. We measure photometry of the protostars in the PACS bands and assemble their spectral energy distributions (SEDs) from 1 to 870 microns with these data, Spitzer spectra and photometry, 2MASS data, and APEX sub-mm data. The SEDs are fit to models generated with radiative transfer codes. From these fits we can constrain the fundamental properties of the protostars. We find luminosities in the range 12-84 L_sun and envelope densities spanning over two orders of magnitude. This implies that the four protostars have a wide range of envelope infall rates and evolutionary states: two have dense, infalling envelopes, while the other two have only residual envelopes. We also show the highly irregular and filamentary structure of the cold dust and gas surrounding the protostars as traced at 160 microns.Comment: 6 pages, 4 figures, accepted for publication in the A&A Herschel special issu

The Chlamydomonas genome project: A decade on

The green alga Chlamydomonas reinhardtii is a popular unicellular organism for studying photosynthesis, cilia biogenesis, and micronutrient homeostasis. Ten years since its genome project was initiated an iterative process of improvements to the genome and gene predictions has propelled this organism to the forefront of the omics era. Housed at Phytozome, the plant genomics portal of the Joint Genome Institute (JGI), the most up-to-date genomic data include a genome arranged on chromosomes and high-quality gene models with alternative splice forms supported by an abundance of whole transcriptome sequencing (RNA-Seq) data. We present here the past, present, and future of Chlamydomonas genomics. Specifically, we detail progress on genome assembly and gene model refinement, discuss resources for gene annotations, functional predictions, and locus ID mapping between versions and, importantly, outline a standardized framework for naming genes