Accurate transition rates for the 5p - 5s transitions in Kr I

Branching fractions were measured for electric dipole transitions from the 5p upper levels to the 5s levels in neutral krypton atoms. The measurements were made with a wall-stabilized electric arc and a 2m monochromator for the spectral lines in the visible, and with a hollow cathode lamp and the NIST 2m-Fourier transform spectrometer for the lines in the near infrared. A semi-empirical calculation, based on accurately known lifetimes for six upper levels, was used to calculate lifetimes for which accurate measurements do not exist. This resulted in a complete set of lifetimes for all 5p levels. Branching fractions and lifetimes were used to calculate transition rates for the 5p-5s transitions. The relative uncertainties of the transition rates range from less than 1% for the strongest lines to about 10% for the weakest lines. Our data also reveal that most of the previous measurements appear to have been affected by opacity effects in the light sources.Comment: 18 pages, 6 figures, 5 table

Interferometric measurement of resonance transition wavelengths in C IV, Si IV, Al III, Al II, and Si II

We have made the first interferomeric measurements of the wavelengths of the important ultraviolet diagnostic lines in the spectra \ion{C}{4} near 155 nm and \ion{Si}{4} near 139 nm with a vacuum ultraviolet Fourier transform spectrometer and high-current discharge sources. The wavelength uncertainties were reduced by one order of magnitude for the \ion{C}{4} lines and by two orders of magnitude for the \ion{Si}{4} lines. Our measurements also provide accurate wavelengths for resonance transitions in \ion{Al}{3}, \ion{Al}{2}, and \ion{Si}{2}.Comment: 6 pages, 2 figures, 1 tabl

Wavelengths of the 3d6(5D)4s a6D - 3d6(5D)4p y6P Multiplet of Fe II (UV 8)

We investigate the wavenumber scale of Fe I and Fe II lines using new spectra recorded with Fourier transform spectroscopy and using a re-analysis of archival spectra. We find that standards in Ar II, Mg I, Mg II and Ge I give a consistent wavenumber calibration. We use the recalibrated spectra to derive accurate wavelengths for the a6D-y6P multiplet of Fe II (UV 8) using both directly measured lines and Ritz wavelengths. Lines from this multiplet are important for astronomical tests of the invariance of the fine structure constant on a cosmological time scale. We recommend a wavelength of 1608.45081 {\AA} with a one standard deviation uncertainty of 0.00007 {\AA} for the a6D9/2-y6P7/2 transition.Comment: 29 pages, 7 figures, 8 tables. Accepted for publication in J. Opt. Soc. Am

Probing the time-variation of the fine-structure constant: Results based on Si IV doublets from a UVES sample

We report a new constraint on the variation of the fine-structure constant based on the analysis of 15 Si IV doublets selected from a ESO-UVES sample. We find \Delta\alpha/\alpha = (+0.15+/-0.43) x 10^-5 over a redshift range of 1.59< z < 2.92 which is consistent with no variation in \alpha. This result represents a factor of three improvement on the constraint on \Delta\alpha/\alpha based on Si IV doublets compared to the published results in the literature. The alkali doublet method used here avoids the implicit assumptions used in the many-multiplet method that chemical and ionization inhomogeneities are negligible and isotopic abundances are close to the terrestrial value.Comment: 12 Pages, 7 figures. Accepted for publication in A&A. In addition to minor corrections an appendix is added in this revised versio

Probing the cosmological variation of the fine-structure constant: Results based on VLT-UVES sample

Development of fundamental physics relies on the constancy of various fundamental quantities such as the fine structure constant. Detecting or constraining the possible time variations of these fundamental physical quantities is an important step toward a complete understanding of basic physics. Here we present the results from a detailed many-multiplet analysis performed using high signal-to-noise ratio, high spectral resolution observations of 23 Mg II systems detected toward 18 QSOs in the redshift range 0.4<z<2.3 obtained using UVES at the VLT. We validate our procedure and define the selection criteria that will avoid possible systematics using detail analysis of simulated data set. We show our Voigt profile fitting code recovers the variation in \alpha very accurately when we use single component systems and multiple component systems that are not heavily blended. Spurious detections are frequently seen when we use heavily blended systems or the systems with very weak lines. Thus we avoided heavily blended systems and the systems with Fe II column density < 2x10^12 cm^-2 in the analysis. All steps involved in the analysis are presented in detail. The weighted mean value of the variation in \alpha obtained from our analysis over the redshift range 0.4<z<2.3 is {\Delta\alpha/\alpha} = (-0.06+/-0.06)x10^-5. The median redshift of our sample is 1.55 the 3\sigma upper limit on the time variation of $\alpha$ is -2.5x10^-16 yr^-1< (\Delta\alpha/\alpha\Delta t) <+1.2x10^-16 yr^-1. To our knowledge this is the strongest constraint from quasar absorption line studies till date.Comment: 23 pages; A&A style, 15 figures, accepte

Infrared Computer-Generated Holograms: Design and Application for the WFIRST Grism Using Wavelength-Tuning Interferometry

Interferometers using computer-generated holograms (CGHs) have become the industry standard to accurately measure aspheric optics. The CGH is a diffractive optical element that can create a phase or amplitude distribution and can be manufactured with low uncertainty using modern lithographic techniques. However, these CGHs have conventionally been used with visible light and piezo-shifting interferometers. Testing the performance of transmissive optics in the infrared requires infrared CGHs and an infrared interferometer. Such an instrument is used in this investigation, which introduces its phase shift via wavelength-tuning. A procedure on how to design and manufacture infrared CGHs and how these were successfully used to model and measure the Wide-Field Infrared Survey Telescope grism elements is provided. Additionally, the paper provides a parametric model, simulation results, and calculations of the errors and measurements that come about when interferometers introduce a phase variation via wavelength-tuning interferometry to measure precision aspheres

Wide-Field InfraRed Survey Telescope (WFIRST) Slitless Spectrometer: Design, Prototype, and Results

The slitless spectrometer plays an important role in the Wide-Field InfraRed Survey Telescope (WFIRST) mission for the survey of emission-line galaxies. This will be an unprecedented very wide field, HST quality 3D survey of emission line galaxies. The concept of the compound grism as a slitless spectrometer has been presented previously. The presentation briefly discusses the challenges and solutions of the optical design, and recent specification updates, as well as a brief comparison between the prototype and the latest design. However, the emphasis of this paper is the progress of the grism prototype: the fabrication and test of the complicated diffractive optical elements and powered prism, as well as grism assembly alignment and testing. Especially how to use different tools and methods, such as IR phase shift and wavelength shift interferometry, to complete the element and assembly tests. The paper also presents very encouraging results from recent element tests to assembly tests. Finally we briefly touch the path forward plan to test the spectral characteristic, such as spectral resolution and response

Lotus japonicus karrikin receptors display divergent ligand-binding specificities and organ-dependent redundancy

Author summary Plant hormone signaling is crucial for development and for adequate responses to biotic and abiotic environmental conditions. The most recently discovered plant hormone receptor KARRIKIN INSENSITVE 2 (KAI2), binds a small butenolide called karrikin that was discovered in smoke and induces germination of fire-following plants. Several lines of evidence suggest a yet elusive endogenous hormone, which acts as ligand for KAI2. Until its identification, synthetic karrikins or the strigolactone-like molecule GR24 are used to probe the karrikin signaling pathway. While the model plant Arabidopsis contains only one KAI2 gene, several copies are maintained in other species suggesting sub-functionalization. We report that genomes of species in the legume hologalegina clade encode two KAI2 versions. In Lotus japonicus, they diverge in their binding ability to synthetic ligands due to three amino acid changes in their binding pocket, of which two are conserved across legumes and one has independently occurred in several species across the angiosperm phylogeny. Surprisingly, L. japonicus hypocotyls react with developmental responses to two different karrikins (KAR(1), KAR(2)) and a synthetic strigolactone rac-GR24, while root development responds only to KAR(1). This shows that there is not only diversity in ligand-receptor relationships but possibly also organ-specific uptake or metabolism of divergent butenolide molecules. Karrikins (KARs), smoke-derived butenolides, are perceived by the alpha/beta-fold hydrolase KARRIKIN INSENSITIVE2 (KAI2) and thought to mimic endogenous, yet elusive plant hormones tentatively called KAI2-ligands (KLs). The sensitivity to different karrikin types as well as the number of KAI2 paralogs varies among plant species, suggesting diversification and co-evolution of ligand-receptor relationships. We found that the genomes of legumes, comprising a number of important crops with protein-rich, nutritious seed, contain two or more KAI2 copies. We uncover sub-functionalization of the two KAI2 versions in the model legume Lotus japonicus and demonstrate differences in their ability to bind the synthetic ligand GR24(ent-5DS) in vitro and in genetic assays with Lotus japonicus and the heterologous Arabidopsis thaliana background. These differences can be explained by the exchange of a widely conserved phenylalanine in the binding pocket of KAI2a with a tryptophan in KAI2b, which arose independently in KAI2 proteins of several unrelated angiosperms. Furthermore, two polymorphic residues in the binding pocket are conserved across a number of legumes and may contribute to ligand binding preferences. The diversification of KAI2 binding pockets suggests the occurrence of several different KLs acting in non-fire following plants, or an escape from possible antagonistic exogenous molecules. Unexpectedly, L. japonicus responds to diverse synthetic KAI2-ligands in an organ-specific manner. Hypocotyl growth responds to KAR(1), KAR(2) and rac-GR24, while root system development responds only to KAR(1). This differential responsiveness cannot be explained by receptor-ligand preferences alone, because LjKAI2a is sufficient for karrikin responses in the hypocotyl, while LjKAI2a and LjKAI2b operate redundantly in roots. Instead, it likely reflects differences between plant organs in their ability to transport or metabolise the synthetic KLs. Our findings provide new insights into the evolution and diversity of butenolide ligand-receptor relationships, and open novel research avenues into their ecological significance and the mechanisms controlling developmental responses to divergent KLs

Common variants in the CLDN2-MORC4 and PRSS1-PRSS2 loci confer susceptibility to acute pancreatitis

BACKGROUND/OBJECTIVES: Acute pancreatitis (AP) is one of the most common gastrointestinal disorders often requiring hospitalization. Frequent aetiologies are gallstones and alcohol abuse. In contrast to chronic pancreatitis (CP) few robust genetic associations have been described. Here we analysed whether common variants in the CLDN2-MORC4 and the PRSS1-PRSS2 locus that increase recurrent AP and CP risk associate with AP. METHODS: We screened 1462 AP patients and 3999 controls with melting curve analysis for SNPs rs10273639 (PRSS1-PRSS2), rs7057398 (RIPPLY), and rs12688220 (MORC4). Calculations were performed for the overall group, aetiology, and gender sub-groups. To examine genotype-phenotype relationships we performed several meta-analyses. RESULTS: Meta-analyses of all AP patients depicted significant (p-value<0.05) associations for rs10273639 (odds ratio (OR) 0.88, 95% confidence interval (CI) 0.81-0.97, p-value 0.01), rs7057398 (OR 1.27, 95% CI 1.07-1.5, p-value 0.005), and rs12688220 (OR 1.32, 95% CI 1.12-1.56, p-value 0.001). For the different aetiology groups a significant association was shown for rs10273639 (OR 0.76, 95% CI 0.63-0.92, p-value 0.005), rs7057398 (OR 1.43, 95% CI 1.07-1.92, p-value 0.02), and rs12688220 (OR 1.44, 95% CI 1.07-1.93, p-value 0.02) in the alcoholic sub-group only. CONCLUSIONS: The association of CP risk variants with different AP aetiologies, which is strongest in the alcoholic AP group, might implicate common pathomechanisms most likely between alcoholic AP and CP