81 research outputs found

    SIGAME simulations of the [CII], [OI] and [OIII] line emission from star forming galaxies at z ~ 6

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    Of the almost 40 star forming galaxies at z>~5 (not counting QSOs) observed in [CII] to date, nearly half are either very faint in [CII], or not detected at all, and fall well below expectations based on locally derived relations between star formation rate (SFR) and [CII] luminosity. Combining cosmological zoom simulations of galaxies with SIGAME (SImulator of GAlaxy Millimeter/submillimeter Emission) we have modeled the multi-phased interstellar medium (ISM) and its emission in [CII], [OI] and [OIII], from 30 main sequence galaxies at z~6 with star formation rates ~3-23Msun/yr, stellar masses ~(0.7-8)x10^9Msun, and metallicities ~(0.1-0.4)xZsun. The simulations are able to reproduce the aforementioned [CII]-faintness at z>5, match two of the three existing z>~5 detections of [OIII], and are furthermore roughly consistent with the [OI] and [OIII] luminosity relations with SFR observed for local starburst galaxies. We find that the [CII] emission is dominated by the diffuse ionized gas phase and molecular clouds, which on average contribute ~66% and ~27%, respectively. The molecular gas, which constitutes only ~10% of the total gas mass is thus a more efficient emitter of [CII] than the ionized gas making up ~85% of the total gas mass. A principal component analysis shows that the [CII] luminosity correlates with the star formation activity as well as average metallicity. The low metallicities of our simulations together with their low molecular gas mass fractions can account for their [CII]-faintness, and we suggest these factors may also be responsible for the [CII]-faint normal galaxies observed at these early epochs.Comment: 24 pages, 14 figures. Accepted for publication in the Astrophysical Journa

    Synthesis of Oligodeoxyribo‐ and Oligoribonucleotides According to the H‐Phosphonate Method

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    Oligonucleotides can be synthesized by condensing a protected nucleoside H‐phosphonate monoester with a second nucleoside in the presence of a coupling agent to produce a dinucleoside H‐phosphonate diester. This can then be converted to a dinucleoside phosphate or to a backbone‐modified analog such as a phosphorothioate or phosphoramidite. This unit discusses four alternative methods for synthesizing nucleoside H‐phosphonate monoesters. The methods are efficient and experimentally simple, and use readily available reagents. The unit describes the activation of the monoesters, as well as competing acylation and other potential side reactions.Peer Reviewedhttps://deepblue.lib.umich.edu/bitstream/2027.42/143594/1/cpnc0304.pd

    CEERS Key Paper. V. Galaxies at 4 < z < 9 Are Bluer than They Appear-Characterizing Galaxy Stellar Populations from Rest-frame ∌1 ÎŒm Imaging

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    We present results from the Cosmic Evolution Early Release Survey on the stellar population parameters for 28 galaxies with redshifts 4 &lt; z &lt; 9 using imaging data from the James Webb Space Telescope (JWST) Mid-Infrared Instrument (MIRI) combined with data from the Hubble Space Telescope and the Spitzer Space Telescope. The JWST/MIRI 5.6 and 7.7 ÎŒm data extend the coverage of the rest-frame spectral energy distribution to nearly 1 ÎŒm for galaxies in this redshift range. By modeling the galaxies’ SEDs the MIRI data show that the galaxies have, on average, rest-frame UV (1600 Å)—I-band colors 0.4 mag bluer than derived when using photometry that lacks MIRI. Therefore, the galaxies have lower ratios of stellar mass to light. The MIRI data reduce the stellar masses by 〈 Δ log M * 〉 = 0.25 dex at 4 &lt; z &lt; 6 and 0.37 dex at 6 &lt; z &lt; 9. This also reduces the star formation rates (SFRs) by 〈ΔlogSFR〉 = 0.14 dex at 4 &lt; z &lt; 6 and 0.27 dex at 6 &lt; z &lt; 9. The MIRI data also improve constraints on the allowable stellar mass formed in early star formation. We model this using a star formation history that includes both a “burst” at z f = 100 and a slowly varying (“delayed-τ”) model. The MIRI data reduce the allowable stellar mass by 0.6 dex at 4 &lt; z &lt; 6 and by ≈1 dex at 6 &lt; z &lt; 9. Applying these results globally, this reduces the cosmic stellar-mass density by an order of magnitude in the early Universe (z ≈ 9). Therefore, observations of rest-frame ≳1 ÎŒm are paramount for constraining the stellar-mass buildup in galaxies at very high redshifts.</p

    CEERS Key Paper IV: Galaxies at 4<z<94 < z < 9 are Bluer than They Appear -- Characterizing Galaxy Stellar Populations from Rest-Frame ∌1\sim 1 micron Imaging

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    We present results from the Cosmic Evolution Early Release Survey (CEERS) on the stellar-population parameters for 28 galaxies with redshifts 4<z<94<z<9 using imaging data from the James Webb Space Telescope (JWST) Mid-Infrared Instrument (MIRI) combined with data from the Hubble Space Telescope and the Spitzer Space Telescope. The JWST/MIRI 5.6 and 7.7 ÎŒ\mum data extend the coverage of the rest-frame spectral-energy distribution (SED) to nearly 1 micron for galaxies in this redshift range. By modeling the galaxies' SEDs the MIRI data show that the galaxies have, on average, rest-frame UV (1600 \r{A}) −- II-band colors 0.4 mag bluer than derived when using photometry that lacks MIRI. Therefore, the galaxies have lower (stellar)-mass-to-light ratios. The MIRI data reduce the stellar masses by ⟹Δlog⁥M∗⟩=0.25\langle \Delta\log M_\ast\rangle=0.25 dex at 4<z<64<z<6 (a factor of 1.8) and 0.37 dex at 6<z<96<z<9 (a factor of 2.3). This also reduces the star-formation rates (SFRs) by ⟹Δlog⁥SFR⟩=0.14\langle \Delta\log\mathrm{SFR} \rangle=0.14 dex at 4<z<64<z<6 and 0.27 dex at 6<z<96<z<9. The MIRI data also improve constraints on the allowable stellar mass formed in early star-formation. We model this using a star-formation history that includes both a "burst' at zf=100z_f=100 and a slowly varying ("delayed-τ\tau") model. The MIRI data reduce the allowable stellar mass by 0.6 dex at 4<z<64<z< 6 and by ≈\approx1 dex at 6<z<96<z<9. Applying these results globally, this reduces the cosmic stellar-mass density by an order of magnitude in the early universe (z≈9z\approx9). Therefore, observations of rest-frame ≳\gtrsim1 ÎŒ\mum are paramount for constraining the stellar-mass build-up in galaxies at very high-redshifts.Comment: Updated with accepted ApJ version. Part of the CEERS Focus Issue. 27 pages, many figures (4 Figure Sets, available upon reasonable request

    Insights into the Transposable Mobilome of Paracoccus spp. (Alphaproteobacteria)

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    Several trap plasmids (enabling positive selection of transposition events) were used to identify a pool of functional transposable elements (TEs) residing in bacteria of the genus Paracoccus (Alphaproteobacteria). Complex analysis of 25 strains representing 20 species of this genus led to the capture and characterization of (i) 37 insertion sequences (ISs) representing 9 IS families (IS3, IS5, IS6, IS21, IS66, IS256, IS1182, IS1380 and IS1634), (ii) a composite transposon Tn6097 generated by two copies of the ISPfe2 (IS1634 family) containing two predicted genetic modules, involved in the arginine deiminase pathway and daunorubicin/doxorubicin resistance, (iii) 3 non-composite transposons of the Tn3 family, including Tn5393 carrying streptomycin resistance and (iv) a transposable genomic island TnPpa1 (45 kb). Some of the elements (e.g. Tn5393, Tn6097 and ISs of the IS903 group of the IS5 family) were shown to contain strong promoters able to drive transcription of genes placed downstream of the target site of transposition. Through the application of trap plasmid pCM132TC, containing a promoterless tetracycline resistance reporter gene, we identified five ways in which transposition can supply promoters to transcriptionally silent genes. Besides highlighting the diversity and specific features of several TEs, the analyses performed in this study have provided novel and interesting information on (i) the dynamics of the process of transposition (e.g. the unusually high frequency of transposition of TnPpa1) and (ii) structural changes in DNA mediated by transposition (e.g. the generation of large deletions in the recipient molecule upon transposition of ISPve1 of the IS21 family). We also demonstrated the great potential of TEs and transposition in the generation of diverse phenotypes as well as in the natural amplification and dissemination of genetic information (of adaptative value) by horizontal gene transfer, which is considered the driving force of bacterial evolution

    Influence of experience on orientation maps in cat visual cortex

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    Experience is known to affect the development of ocular dominance maps in visual cortex, but it has remained controversial whether orientation preference maps are similarly affected by limiting visual experience to a single orientation early in life. Here we used optical imaging based on intrinsic signals to show that the visual cortex of kittens reared in a striped environment responded to all orientations, but devoted up to twice as much surface area to the experienced orientation as the orthogonal one. This effect is due to an instructive role of visual experience whereby some neurons shift their orientation preferences toward the experienced orientation. Thus, although cortical orientation maps are remarkably rigid in the sense that orientations that have never been seen by the animal occupy a large portion of the cortical territory, visual experience can nevertheless alter neuronal responses to oriented contours
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