The functionalization of molecules by cleaving inert carbon-carbon single bonds is regarded as a great synthetic challenge due to their inherent stability. In recent years, significant progress has ...been made in the activation of small rings relying on the release of strain energy. By contrast, the number of catalytic methodologies for the activation of unstrained carbon-carbon single bonds is still limited. This review focuses on the recent developments in transition-metal-catalyzed cleavage of C-C bonds in unstrained alcohols via β-carbon elimination. Emphasis is placed on the mechanistic aspects of the discussed transformations and their applications to the deconstruction and reorganization of molecules.
Abstract
This paper provides an update of our previous scaling relations between galaxy-integrated molecular gas masses, stellar masses, and star formation rates (SFRs), in the framework of the star ...formation main sequence (MS), with the main goal of testing for possible systematic effects. For this purpose our new study combines three independent methods of determining molecular gas masses from CO line fluxes, far-infrared dust spectral energy distributions, and ∼1 mm dust photometry, in a large sample of 1444 star-forming galaxies between
z
= 0 and 4. The sample covers the stellar mass range log(
M
*
/
M
⊙
) = 9.0–11.8, and SFRs relative to that on the MS,
δ
MS = SFR/SFR(MS), from 10
−1.3
to 10
2.2
. Our most important finding is that all data sets, despite the different techniques and analysis methods used, follow the same scaling trends, once method-to-method zero-point offsets are minimized and uncertainties are properly taken into account. The molecular gas depletion time
t
depl
, defined as the ratio of molecular gas mass to SFR, scales as (1 +
z
)
−0.6
× (
δ
MS)
−0.44
and is only weakly dependent on stellar mass. The ratio of molecular to stellar mass
μ
gas
depends on (
1
+
z
)
2.5
×
(
δ
MS
)
0.52
×
(
M
*
)
−
0.36
, which tracks the evolution of the specific SFR. The redshift dependence of
μ
gas
requires a curvature term, as may the mass dependences of
t
depl
and
μ
gas
. We find no or only weak correlations of
t
depl
and
μ
gas
with optical size
R
or surface density once one removes the above scalings, but we caution that optical sizes may not be appropriate for the high gas and dust columns at high
z
.
ABSTRACT
We report on the determination of electron densities, and their impact on the outflow masses and rates, measured in the central few hundred parsecs of 11 local luminous active galaxies. We ...show that the peak of the integrated line emission in the active galactic nuclei (AGN) is significantly offset from the systemic velocity as traced by the stellar absorption features, indicating that the profiles are dominated by outflow. In contrast, matched inactive galaxies are characterized by a systemic peak and weaker outflow wing. We present three independent estimates of the electron density in these AGN, discussing the merits of the different methods. The electron density derived from the S ii doublet is significantly lower than that found with a method developed in the last decade using auroral and transauroral lines, as well as a recently introduced method based on the ionization parameter. The reason is that, for gas photoionized by an AGN, much of the S ii emission arises in an extended partially ionized zone where the implicit assumption that the electron density traces the hydrogen density is invalid. We propose ways to deal with this situation and we derive the associated outflow rates for ionized gas, which are in the range 0.001–0.5 M⊙ yr−1 for our AGN sample. We compare these outflow rates to the relation between $\dot{M}_{\rm out}$ and LAGN in the literature, and argue that it may need to be modified and rescaled towards lower mass outflow rates.
We report new detections and limits from a NOEMA and ALMA CO(1-0) search for molecular outflows in 13 local galaxies with high far-infrared surface brightness, and combine these with local universe ...CO outflow results from the literature. The CO line ratios and spatial outflow structure of our targets provide some constraints on the conversion steps from observables to physical quantities such as molecular mass outflow rates. Where available, ratios between outflow emission in higher J CO transitions and in CO(1-0) are typically consistent with excitation
R
i
1
≲ 1. However, for IRAS 13120−5453,
R
31
= 2.10 ± 0.29 indicates optically thin CO in the outflow. Like much of the outflow literature, we use
α
CO(1 − 0)
= 0.8, and we present arguments for using
C
= 1 in deriving molecular mass outflow rates
Ṁ
out
=
C
M
out
v
out
/
R
out
. We compare the two main methods for molecular outflow detection: CO millimeter interferometry and
Herschel
OH-based spectroscopic outflow searches. For 26 sources studied with both methods, we find an 80% agreement in detecting
v
out
≳ 150 km s
−1
outflows, and non-matches can be plausibly ascribed to outflow geometry and signal-to-noise ratio. For a published sample of 12 bright ultraluminous infrared galaxies with detailed OH-based outflow modeling, CO outflows are detected in all but one. Outflow masses, velocities, and sizes for these 11 sources agree well between the two methods, and modest remaining differences may relate to the different but overlapping regions sampled by CO emission and OH absorption. Outflow properties correlate better with active galactic nucleus (AGN) luminosity and with bolometric luminosity than with far-infrared surface brightness. The most massive outflows are found for systems with current AGN activity, but significant outflows in nonAGN systems must relate to star formation or to AGN activity in the recent past. We report scaling relations for the increase of outflow mass, rate, momentum rate, and kinetic power with bolometric luminosity. Short flow times of ∼10
6
yr and some sources with resolved multiple outflow episodes support a role of intermittent driving, likely by AGNs.
Evidence of strong quasar feedback in the early Universe Maiolino, R.; Gallerani, S.; Neri, R. ...
Monthly notices of the Royal Astronomical Society. Letters,
September 2012, 2012-09-01, 20120901, Volume:
425, Issue:
1
Journal Article
Peer reviewed
Open access
ABSTRACT
Most theoretical models invoke quasar‐driven outflows to quench star formation in massive galaxies, and this feedback mechanism is required to account for the population of old and passive ...galaxies observed in the local Universe. The discovery of massive, old and passive galaxies at z∼ 2 implies that such quasar feedback on to the host galaxy must have been at work very early on, close to the reionization epoch. We have observed the C ii 158 m transition in SDSS J114816.64+525150.3, which, at z= 6.4189, is one of the most distant quasars known. We detect broad wings of the line tracing a quasar‐driven massive outflow. This is the most distant massive outflow ever detected and is likely tracing the long‐sought quasar feedback, already at work in the early Universe. The outflow is marginally resolved on scales of ∼16 kpc, implying that the outflow can really affect the whole galaxy, as required by quasar feedback models. The inferred outflow rate, , is the highest ever found. At this rate, the outflow can clean the gas in the host galaxy, and therefore quench star formation, in a few million years.
The SHINING survey offers a great opportunity to study the properties of the ionized and neutral media of galaxies from prototypical starbursts and active galactic nuclei (AGNs) to heavily obscured ...objects. Based on Herschel/PACS observations of the main far-infrared (FIR) fine-structure lines, in this paper, we analyze the physical mechanisms behind the observed line deficits in galaxies, the apparent offset of luminous infrared galaxies (LIRGs) from the mass-metallicity relation, and the scaling relations between C ii 158 m line emission and star formation rate (SFR). Based on a toy model and the Cloudy code, we conclude that the increase in the ionization parameter with FIR surface brightness can explain the observed decrease in the line-to-FIR continuum ratio of galaxies. In the case of the C ii line, the increase in the ionization parameter is accompanied by a reduction in the photoelectric heating efficiency and the inability of the line to track the increase in the FUV radiation field as galaxies become more compact and luminous. In the central approximately kiloparsec regions of AGN galaxies, we observe a significant increase in the O i 63 m/C ii line ratio; the AGN impact on the line-to-FIR ratios fades on global scales. Based on extinction-insensitive metallicity measurements of LIRGs, we confirm that they lie below the mass-metallicity relation, but the offset is smaller than those reported in studies that use optical-based metal abundances. Finally, we present scaling relations between C ii emission and SFR in the context of the main sequence of star-forming galaxies.
We study the incidence of nuclear obscuration on a complete sample of 1310 active galactic nuclei (AGN) selected on the basis of their rest-frame 2-10 keV X-ray flux from the XMM-COSMOS survey, in ...the redshift range 0.3 < z < 3.5. We classify the AGN as obscured or unobscured on the basis of either the optical spectral properties and the overall SED or the shape of the X-ray spectrum. The two classifications agree in about 70 per cent of the objects, and the remaining 30 per cent can be further subdivided into two distinct classes: at low luminosities X-ray unobscured AGN do not always show signs of broad lines or blue/UV continuum emission in their optical spectra, most likely due to galaxy dilution effects; at high-luminosities broad-line AGN may have absorbed X-ray spectra, which hints at an increased incidence of small-scale (sub-parsec) dust-free obscuration. We confirm that the fraction of obscured AGN is a decreasing function of the intrinsic X-ray luminosity, while the incidence of absorption shows significant evolution only for the most luminous AGN, which appear to be more commonly obscured at higher redshift. We find no significant difference between the mean stellar masses and star formation rates of obscured and unobscured AGN hosts. We conclude that the physical state of the medium responsible for obscuration in AGN is complex and mainly determined by the radiation environment (nuclear luminosity) in a small region enclosed within the gravitational sphere of influence of the central black hole, but is largely insensitive to the wider scale galactic conditions.
Remdesivir (RDV, Veklury
®
) is a once-daily, nucleoside ribonucleic acid polymerase inhibitor of severe acute respiratory syndrome coronavirus 2 replication. Remdesivir has been granted approvals in ...several countries for use in adults and children hospitalized with severe coronavirus disease 2019 (COVID-19). Inside the cell, remdesivir undergoes metabolic activation to form the intracellular active triphosphate metabolite, GS-443902 (detected in peripheral blood mononuclear cells), and ultimately, the renally eliminated plasma metabolite GS-441524. This review discusses the pre-clinical pharmacology of RDV, clinical pharmacokinetics, pharmacodynamics/concentration-QT analysis, rationale for dose selection for treatment of patients with COVID-19, and drug–drug interaction potential based on available in vitro and clinical data in healthy volunteers. Following single-dose intravenous administration over 2 h of an RDV solution formulation across the dose range of 3–225 mg in healthy participants, RDV and its metabolites (GS-704277and GS-441524) exhibit linear pharmacokinetics. Following multiple doses of RDV 150 mg once daily for 7 or 14 days, major metabolite GS-441524 accumulates approximately 1.9-fold in plasma. Based on pharmacokinetic bridging from animal data and available human data in healthy volunteers, the RDV clinical dose regimen of a 200-mg loading dose on day 1 followed by 100-mg maintenance doses for 4 or 9 days was selected for further evaluation of pharmacokinetics and safety. Results showed high intracellular concentrations of GS-443902 suggestive of efficient conversion from RDV into the triphosphate form, and further supporting this clinical dosing regimen for the treatment of COVID-19. Mathematical drug–drug interaction liability predictions, based on in vitro and phase I data, suggest RDV has low potential for drug–drug interactions, as the impact of inducers or inhibitors on RDV disposition is minimized by the parenteral route of administration and extensive extraction. Using physiologically based pharmacokinetic modeling, RDV is not predicted to be a clinically significant inhibitor of drug-metabolizing enzymes or transporters in patients infected with COVID-19 at therapeutic RDV doses.
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