The giant elliptical galaxy NGC 1275, at the centre of the Perseus cluster, is surrounded by a well-known giant nebulosity of emission-line filaments, which are plausibly in excess of 10(8) years ...old. The filaments are dragged out from the centre of the galaxy by radio-emitting 'bubbles' rising buoyantly in the hot intracluster gas, before later falling back. They act as markers of the feedback process by which energy is transferred from the central massive black hole to the surrounding gas. The mechanism by which the filaments are stabilized against tidal shear and dissipation into the surrounding extremely hot (4 x 10(7) K) gas has been unclear. Here we report observations that resolve thread-like structures in the filaments. Some threads extend over 6 kpc, yet are only 70 pc wide. We conclude that magnetic fields in the threads, in pressure balance with the surrounding gas, stabilize the filaments, so allowing a large mass of cold gas to accumulate and delay star formation.
Celotno besedilo
Dostopno za:
DOBA, IJS, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
Use of biomass is crucial for a sustainable supply of chemicals and fuels for future generations. Compared to fossil feedstocks, biomass is more functionalized and requires defunctionalisation to ...make it suitable for use. Deoxygenation is an important method of defunctionalisation. While thermal deoxygenation is possible, high energy input and lower reaction selectivity makes it less suitable for producing the desired chemicals and fuels. Catalytic deoxygenation is more successful by lowering the activation energy of the reaction, and when designed correctly, is more selective. Catalytic deoxygenation can be performed in various ways. Here we focus on decarboxylation and decarbonylation. There are several classes of catalysts: heterogeneous, homogeneous, bio- and organocatalysts and all have limitations. Homogeneous catalysts generally have superior selectivity and specificity but separation from the reaction is cumbersome. Heterogeneous catalysts are more readily isolated and can be utilised at high temperatures, however they have lower selectivity in complex reaction mixtures. While bio-catalysts can operate at ambient temperatures, the volumetric productivity is lower. Therefore it is not always apparent in advance which catalyst is the most suitable in terms of conversion and selectivity under optimal process conditions. Here we compare classes of catalysts for the decarboxylation and decarbonylation of biobased molecules and discuss their limitations and advantages. We mainly focus on the activity of the catalysts and find there is a strong correlation between specific activity (turn over frequency) and temperature for metal based catalysts (homogeneous or heterogeneous). Thus one is not more active than the other at the same temperature. Alternatively, enzymes have a higher turnover frequency but drawbacks (low volumetric productivity) should be overcome.
During decarboxylation and decarbonylation of biomass the activity of homogeneous and heterogeneous catalysts is mainly determined by temperature not by its nature; enzymes display higher activity.
The hot intra-cluster medium (ICM) permeating galaxy clusters and groups is not pristine, as it has been continuously enriched by metals synthesised in Type Ia (SNIa) and core-collapse (SNcc) ...supernovae since the major epoch of star formation (z ≃ 2–3). The cluster/group enrichment history and mechanisms responsible for releasing and mixing the metals can be probed via the radial distribution of SNIa and SNcc products within the ICM. In this paper, we use deep XMM-Newton/EPIC observations from a sample of 44 nearby cool-core galaxy clusters, groups, and ellipticals (CHEERS) to constrain the average radial O, Mg, Si, S, Ar, Ca, Fe, and Ni abundance profiles. The radial distributions of all these elements, averaged over a large sample for the first time, represent the best constrained profiles available currently. Specific attention is devoted to a proper modelling of the EPIC spectral components, and to other systematic uncertainties that may affect our results. We find an overall decrease of the Fe abundance with radius out to ~0.9 r500 and ~0.6 r500 for clusters and groups, respectively, in good agreement with predictions from the most recent hydrodynamical simulations. The average radial profiles of all the other elements (X) are also centrally peaked and, when rescaled to their average central X/Fe ratios, follow well the Fe profile out to at least ~0.5 r500. As predicted by recent simulations, we find that the relative contribution of SNIa (SNcc) to the total ICM enrichment is consistent with being uniform at all radii, both for clusters and groups using two sets of SNIa and SNcc yield models that reproduce the X/Fe abundance pattern in the core well. In addition to implying that the central metal peak is balanced between SNIa and SNcc, our results suggest that the enriching SNIa and SNcc products must share the same origin and that the delay between the bulk of the SNIa and SNcc explosions must be shorter than the timescale necessary to diffuse out the metals. Finally, we report an apparent abundance drop in the very core of 14 systems (~32% of the sample). Possible origins of these drops are discussed.
We present ALMA observations of the CO(1–0) and CO(3–2) line emission tracing filaments of cold molecular gas in the central galaxy of the cluster PKS 0745−191. The total molecular gas mass of
...$4.6\pm 0.3\times 10^{9} {\rm \, M_{{\odot}}}$
, assuming a Galactic X
CO factor, is divided roughly equally between three filaments each extending radially 3-5 kpc from the galaxy centre. The emission peak is located in the SE filament ∼ 1 arcsec (2 kpc) from the nucleus. The velocities of the molecular clouds in the filaments are low, lying within
$\pm 100 {\rm \, km \rm \, s^{-1}}$
of the galaxy's systemic velocity. Their full width at half-maximum (FWHM) are less than
$150 {\rm \, km \rm \, s^{-1},}$
which is significantly below the stellar velocity dispersion. Although the molecular mass of each filament is comparable to a rich spiral galaxy, such low velocities show that the filaments are transient and the clouds would disperse on < 107 yr time-scales unless supported, likely by the indirect effect of magnetic fields. The velocity structure is inconsistent with a merger origin or gravitational free-fall of cooling gas in this massive central galaxy. If the molecular clouds originated in gas cooling even a few kpc from their current locations their velocities would exceed those observed. Instead, the projection of the N and SE filaments underneath X-ray cavities suggests they formed in the updraft behind bubbles buoyantly rising through the cluster atmosphere. Direct uplift of the dense gas by the radio bubbles appears to require an implausibly high coupling efficiency. The filaments are coincident with low temperature X-ray gas, bright optical line emission and dust lanes indicating that the molecular gas could have formed from lifted warmer gas that cooled in situ.
We present a new technique for choosing spatial regions for X-ray spectroscopy, called ‘contour binning’. The method chooses regions by following contours on a smoothed image of the object. In ...addition, we re-explore a simple method for adaptively smoothing X-ray images according to the local count rate, we term ‘accumulative smoothing’, which is a generalization of the method used by fadapt. The algorithms are tested by applying them to a simulated cluster data set. We illustrate the techniques by using them on a 50 ks Chandra observation of the Cassiopeia A supernova remnant. Generated maps of the object showing abundances in eight different elements, absorbing column density, temperature, ionization time-scale and velocity are presented. Tests show that contour binning reproduces surface brightness considerably better than other methods. It is particularly suited to objects with detailed spatial structure such as supernova remnants and the cores of galaxy clusters, producing aesthetically pleasing results.
We present the results from extensive, new observations of the Perseus Cluster of galaxies, obtained as a Suzaku Key Project. The 85 pointings analysed span eight azimuthal directions out to 2° = 2.6 ...Mpc, to and beyond the virial radius r
200 ∼ 1.8 Mpc, offering the most detailed X-ray measurements of the intracluster medium (ICM) at large radii in any cluster to date. The azimuthally averaged density profile for r > 0.4r
200 is relatively flat, with a best-fitting power-law index δ = 1.69 ± 0.13, significantly smaller than expected from numerical simulations. The entropy profile in the outskirts lies systematically below the power-law behaviour expected from large-scale structure formation models which include only the heating associated with gravitational collapse. Conversely, the pressure profile beyond ∼0.6r
200 shows an excess with respect to the best-fitting model describing the SZ measurements for a sample of clusters observed with the Planck satellite. The differences between the expected and measured density, entropy and pressure profiles can be explained by a systematic overestimation of the ICM density at large radii caused by homogeneous modelling of inhomogeneous gas distributions (i.e. gas clumping), with the density overestimates ranging from factors of ∼1.2 to 2 or more at r
200 along different directions. We find no evidence for a bias in the temperature measurements within the virial radius. Along the cluster minor axis, we find a flattening of the entropy profiles outside ∼0.6r
200, while along the major axis, the entropy rises all the way to the outskirts.
Abstract
We present the first results from the Mapping Obscuration to Reionization with ALMA (MORA) survey, the largest Atacama Large Millimeter/submillimeter Array (ALMA) blank-field contiguous ...survey to date (184 arcmin
2
) and the only at 2 mm to search for dusty star-forming galaxies (DSFGs). We use the 13 sources detected above 5
σ
to estimate the first ALMA galaxy number counts at this wavelength. These number counts are then combined with the state-of-the-art galaxy number counts at 1.2 and 3 mm and with a backward evolution model to place constraints on the evolution of the IR luminosity function and dust-obscured star formation in the past 13 billion years. Our results suggest a steep redshift evolution on the space density of DSFGs and confirm the flattening of the IR luminosity function at faint luminosities, with a slope of
. We conclude that the dust-obscured component, which peaks at
z
≈ 2–2.5, has dominated the cosmic history of star formation for the past ∼12 billion years, back to
z
∼ 4. At
z
= 5, the dust-obscured star formation is estimated to be ∼35% of the total star formation rate density and decreases to 25%–20% at
z
= 6–7, implying a minor contribution of dust-enshrouded star formation in the first billion years of the universe. With the dust-obscured star formation history constrained up to the end of the epoch of reionization, our results provide a benchmark to test galaxy formation models, to study the galaxy mass assembly history, and to understand the dust and metal enrichment of the universe at early times.
One of the main effectors on the quality of life of living-kidney donors is postoperative fatigue. Caloric restriction (CR) and short-term fasting (STF) are associated with improved fitness and ...increased resistance to acute stress. CR/STF increases the expression of cytoprotective genes, increases immunomodulation via increased anti-inflammatory cytokine production, and decreases the expression of pro-inflammatory markers. As such, nutritional preconditioning by CR or STF represents a non-invasive and cost-effective method that could mitigate the effects of acute surgery-induced stress and postoperative fatigue. To investigate whether preoperative STF contributes to a reduction in fatigue after living-kidney donation, a randomized clinical trial is indicated.
We aim to determine whether 2.5 days of fasting reduces postoperative fatigue score in subjects undergoing living-kidney donation. In this randomized study, the intervention group will follow a preoperative fasting regime for 2.5 days with a low-dose laxative, while the control group will receive standard care. The main study endpoint is postoperative fatigue, 4 weeks after living-kidney donation. Secondary endpoints include the effect of preoperative fasting on postoperative hospital admission time, the feasibility of STF, and the postoperative recovery of donor and recipient kidney function. This study will provide us with knowledge of the feasibility of STF and confirm its effect on postoperative recovery.
Our study will provide clinically relevant information on the merits of caloric restriction for living-kidney donors and recipients. We expect to reduce the postoperative fatigue in living-kidney donors and improve the postoperative recovery of living-kidney recipients. It will provide evidence on the clinical merits and potential caveats of preoperative dietary interventions.
Netherlands Trial Register NL9262 . EudraCT 2020-005445-16 . MEC Erasmus MC MEC-2020-0778. CCMO NL74623.078.21.
In a 24‐month, multicenter, open‐label, randomized trial, 715 de novo kidney transplant recipients were randomized at 10–14 weeks to convert to everolimus (n = 359) or remain on standard calcineurin ...inhibitor (CNI) therapy (n = 356; 231 tacrolimus; 125 cyclosporine), all with mycophenolic acid and steroids. The primary endpoint, change in estimated glomerular filtration rate (eGFR) from randomization to month 12, was similar for everolimus versus CNI: mean (standard error) 0.3(1.5) mL/min/1.732 versus −1.5(1.5) mL/min/1.732 (p = 0.116). Biopsy‐proven acute rejection (BPAR) at month 12 was more frequent under everolimus versus CNI overall (9.7% vs. 4.8%, p = 0.014) and versus tacrolimus‐treated patients (2.6%, p < 0.001) but similar to cyclosporine‐treated patients (8.8%, p = 0.755). Reporting on de novo donor‐specific antibodies (DSA) was limited but suggested more frequent anti‐HLA Class I DSA under everolimus. Change in left ventricular mass index was similar. Discontinuation due to adverse events was more frequent with everolimus (23.6%) versus CNI (8.4%). In conclusion, conversion to everolimus at 10–14 weeks posttransplant was associated with renal function similar to that with standard therapy overall. Rates of BPAR were low in all groups, but lower with tacrolimus than everolimus.
In a multicenter, open‐label, randomized trial of de novo kidney transplant recipients, conversion to everolimus at 10–14 weeks posttransplant is associated with similar renal function as in patients who continue to standard tacrolimus or cyclosporine therapy, with low rates of biopsy‐proven acute rejection in all groups, but lower rates with tacrolimus than everolimus.
We examine the velocity width of cool X-ray emitting material using XMM-Newton Reflection Grating Spectrometer (RGS) spectra of a sample of clusters and group of galaxies and elliptical galaxies. ...Improving on our previous analyses, we apply a spectral model which accounts for broadening due to the spatial extent of the source. With both conventional and Markov Chain Monte Carlo approaches we obtain limits, or in a few cases measurements, of the velocity broadening of the coolest X-ray material. In our sample, we include new observations targeting objects with compact, bright, line-rich cores. One of these, MACS J2229.7−2755, gives a velocity limit of
at the 90 per cent confidence level. Other systems with limits close to
include A 1835, NGC 4261 and NGC 4472. For more than a third of the targets we find limits better than
. HCG 62, NGC 1399 and A 3112 show evidence for
velocity broadening. For a smaller sample of objects, we use continuum-subtracted emission line surface brightness profiles to account for the spatial broadening. Although there are significant systematic errors associated with the technique (
), we find broadening at the level of 280 to
in A 3112, NGC 1399 and NGC 4636.
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