Multiple Elements RegulateMash1Expression in the Developing CNS

AbstractMash1, a transcription factor of the basic helix–loop–helix class, is expressed during embryogenesis in restricted regions of the nervous system. An essential role for Mash1 in neural development was demonstrated previously in mice carrying a targeted disruption of theMash1gene. Regulation of the precise temporal and spatial expression ofMash1is thus likely to be important for proper neural development. In this study, sequences that regulateMash1expression in the central nervous system were characterized by assaying the expression oflacZreporter genes in transgenic embryos. A 1158-bp enhancer localized ∼7 kb upstream of theMash1coding region was identified. Deletions within this enhancer region reveal the presence of both positive and negativecis-acting elements. Analysis of multiple sequences within the enhancer demonstrate that different elements preferentially function in different regions within theMash1-specific CNS expression domain. In addition, a role for sequences 3′ of theMash1coding region is revealed, providing evidence for posttranscriptional control ofMash1expression in multiple CNS domains

Reactions of polycyclic alkylaromatics--VI. Detailed chemical kinetic modeling

We developed a detailed chemical kinetics model for the pyrolysis of long-chain polycyclic n-alkylarenes based on a general free-radical mechanism. The model accounts for the two major primary pathways in the pyrolysis network of polycyclic alkylaromatics. Using 1-dodecylpyrene (DDP) as an example, we show that the model qualitatively predicted the effects of time, temperature, and concentration on the product molar yields and the reaction kinetics. The model also predicted the autocatalytic kinetics associated with the cleavage of the aryl---alkyl bond. The model results showed that radical hydrogen transfer was the dominant hydrogenolysis mechanism during all but the very initial stages of the reaction when reverse radical disproportionation dominated. A sensitivity analysis revealed that reactions involving [alpha]-DDP radicals where the most important in determining the reaction kinetics and the product selectivities.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/31912/1/0000865.pd

Reactions of polycyclic alkylaromatics: Structure and reactivity

A family of alkyl-substituted polycyclic aromatic hydrocarbons was pyrolyzed in microbatch reactors at temperatures between 350°C and 425°C. A general pyrolysis network was deduced for these compounds, and it comprised two major and one minor parallel pathways. The first major pathway resulted in products analogous to the major products observed from alkylbenzene pyrolysis. The second major pathway led to products via the cleavage of the strong aryl-alkyl C[bond]C bond. The third pathway led to small amounts of products, presumably through cyclization and condensation reactions. The relative importance of the two major pathways varied for the different compounds. The rates of aryl-alkyl bond cleavage differed for the different compounds, and these rates were quantitatively related to the compounds' localization energies through Dewar reactivity numbers.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/37418/1/690371104_ftp.pd

Reactions of polycyclic alkylaromatics: 5. pyrolysis of methylanthracenes

1-, 2- and 9-methylanthracene were pyrolyzed neat at temperatures between 350 and 450°C for batch holding times up to 300 min. The pyrolysis proceeded through three parallel primary reaction pathways: one led to anthracene via demethylation; the second to dimethylanthracenes through methyl addition; and the third to methyl-9,10-dihydroanthracenes through hydrogenation. The relative importance of these three paths varied for different methylanthracene isomers. The presence of these primary pathways can be rationalized in terms of recently elucidated hydrogentransfer mechanisms and other aspects of the developing free-radical chemistry of polycyclic alkylarenes. The demethylation rate at 400°C for the methylanthracenes and seven other methylarenes was correlated with Dewar reactivity numbers, which provide a measure of the localization energy, as ln rate (arene yield/min) = 3.7– 7.1 N ts , where N ts is the Dewar reactivity number for the perpheral aromatic carbon atom bearing the methyl substituent. This correlation may be useful in molecular-based reaction models for the conversion of heavy hydrocarbon resources such as coals and heavy oils.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/37427/1/690390812_ftp.pd

FLITECAM: current status and results from observatory verification flights

This paper describes the current status of FLITECAM, the near-infrared (1 - 5 μm) camera and spectrometer for NASA’s Stratospheric Observatory for Infrared Astronomy (SOFIA). Due to a change in schedule FLITECAM’s delivery was advanced, allowing it to be co-mounted with the HIPO instrument and used on four flights in October 2011 for observatory verification. Although not part of FLITECAM’s commissioning time, some preliminary performance characteristics were determined. Image size as a function of wavelength was measured prior to the installation of active mass dampers on the telescope. Preliminary grism spectroscopy was also obtained. In addition, FLITECAM was used to measure the emissivity of the telescope and warm optics in the co-mounted configuration. New narrow band filters were added to the instrument, including a Paschen alpha filter for line emission. Results are illustrated

Flux profile scanners for scattered high-energy electrons

The paper describes the design and performance of flux integrating Cherenkov scanners with air-core reflecting light guides used in a high-energy, high-flux electron scattering experiment at the Stanford Linear Accelerator Center. The scanners were highly radiation resistant and provided a good signal to background ratio leading to very good spatial resolution of the scattered electron flux profile scans.Comment: 22 pages, 17 figure

QSO Absorption Systems Detected in Ne VIII: High-Metallicity Clouds with a Large Effective Cross Section

Using high resolution, high signal-to-noise ultraviolet spectra of the z = 0.9754 quasar PG1148+549 obtained with the Cosmic Origins Spectrograph (COS) on the Hubble Space Telescope, we study the physical conditions and abundances of NeVIII+OVI absorption line systems at z(abs) =0.68381, 0.70152, 0.72478. In addition to NeVIII and OVI, absorption lines from multiple ionization stages of oxygen (OII, OIII, OIV) are detected and are well-aligned with the more highly ionized species. We show that these absorbers are multiphase systems including hot gas (T ~ 10^{5.7} K) that produces NeVIII and OVI, and the gas metallicity of the cool phase ranges from Z = 0.3 Z_{solar} to supersolar. The cool (~10^{4} K) phases have densities n_{H} ~ 10^{-4} cm^{-3} and small sizes (< 4kpc); these cool clouds are likely to expand and dissipate, and the NeVIII may be within a transition layer between the cool gas and a surrounding, much hotter medium. The NeVIII redshift density, dN/dz = 7^{+7}_{-3}, requires a large number of these clouds for every L > 0.1L* galaxy and a large effective absorption cross section (>~ 100 kpc), and indeed, we find a star forming ~L* galaxy at the redshift of the z(abs)=0.72478 system, at an impact parameter of 217 kpc. Multiphase absorbers like these NeVIII systems are likely to be an important reservoir of baryons and metals in the circumgalactic media of galaxies.Comment: Final published version (Astrophysical Journal

Heavy quark symmetry constraints on semileptonic form factors and decay widths of doubly heavy baryons

We show how heavy quark symmetry constraints on doubly heavy baryon semileptonic decay widths can be used to test the validity of different quark model calculations. The large discrepancies in the results observed between different quark model approaches can be understood in terms of a severe violation of heavy quark spin symmetry constraints by some of those models.Comment: 10 LaTex pages, 3 figures, 6 tables. Corrected and enlarged versio

Studies of a three-stage dark matter and neutrino observatory based on multi-ton combinations of liquid xenon and liquid argon detectors

We study a three stage dark matter and neutrino observatory based on multi-ton two-phase liquid Xe and Ar detectors with sufficiently low backgrounds to be sensitive to WIMP dark matter interaction cross sections down to 10E-47 cm^2, and to provide both identification and two independent measurements of the WIMP mass through the use of the two target elements in a 5:1 mass ratio, giving an expected similarity of event numbers. The same detection systems will also allow measurement of the pp solar neutrino spectrum, the neutrino flux and temperature from a Galactic supernova, and neutrinoless double beta decay of 136Xe to the lifetime level of 10E27 - 10E28 y corresponding to the Majorana mass predicted from current neutrino oscillation data. The proposed scheme would be operated in three stages G2, G3, G4, beginning with fiducial masses 1-ton Xe + 5-ton Ar (G2), progressing to 10-ton Xe + 50-ton Ar (G3) then, dependent on results and performance of the latter, expandable to 100-ton Xe + 500-ton Ar (G4). This method of scale-up offers the advantage of utilizing the Ar vessel and ancillary systems of one stage for the Xe detector of the succeeding stage, requiring only one new detector vessel at each stage. Simulations show the feasibility of reducing or rejecting all external and internal background levels to a level <1 events per year for each succeeding mass level, by utilizing an increasing outer thickness of target material as self-shielding. The system would, with increasing mass scale, become increasingly sensitive to annual signal modulation, the agreement of Xe and Ar results confirming the Galactic origin of the signal. Dark matter sensitivities for spin-dependent and inelastic interactions are also included, and we conclude with a discussion of possible further gains from the use of Xe/Ar mixtures