Galaxy mergers are believed to trigger strong starbursts. This is well assessed by observations in the local Universe. However, the efficiency of this mechanism has poorly been tested so far for ...high-redshift, actively star-forming, galaxies. We present a suite of pc-resolution hydrodynamical numerical simulations to compare the star formation process along a merging sequence of high- and low-redshift galaxies, by varying the gas mass fraction between the two models. We show that, for the same orbit, high-redshift gas-rich mergers are less efficient than low-redshift ones at producing starbursts; the star formation rate excess induced by the merger and its duration are both around 10 times lower than in the low gas fraction case. The mechanisms that account for the star formation triggering at low redshift -- the increased compressive turbulence, gas fragmentation, and central gas inflows -- are only mildly, if not at all, enhanced for high gas fraction galaxy encounters. Furthermore, we show that the strong stellar feedback from the initially high star formation rate in high-redshift galaxies does not prevent an increase of the star formation during the merger. Our results are consistent with the observed increase of the number of major mergers with increasing redshift being faster than the respective increase in the number of starburst galaxies.
Abstract
We use hydrodynamical simulations of a Cartwheel-like ring galaxy, modelled as a nearly head-on collision of a small companion with a larger disc galaxy, to probe the evolution of the ...gaseous structures and flows, and to explore the physical conditions setting the star formation activity. Star formation is first quenched by tides as the companion approaches, before being enhanced shortly after the collision. The ring ploughs the disc material as it radially extends, and almost simultaneously depletes its stellar and gaseous reservoir into the central region, through the spokes, and finally dissolve 200 Myr after the collision. Most of star formation first occurs in the ring before this activity is transferred to the spokes and then the nucleus. We thus propose that the location of star formation traces the dynamical stage of ring galaxies, and could help constrain their star formation histories. The ring hosts tidal compression associated with strong turbulence. This compression yields an azimuthal asymmetry, with maxima reached in the side furthest away from the nucleus, which matches the star formation activity distribution in our models and in observed ring systems. The interaction triggers the formation of star clusters significantly more massive than before the collision, but less numerous than in more classical galaxy interactions. The peculiar geometry of Cartwheel-like objects thus yields a star (cluster) formation activity comparable to other interacting objects, but with notable second order differences in the nature of turbulence, the enhancement of the star formation rate, and the number of massive clusters formed.
Abstract
We present Atacama Large Millimeter/submillimeter Array observations at a spatial resolution of 0.″2 (60 pc) of CO emission from the Taffy galaxies (UGC 12914/5). The observations are ...compared with narrowband Pa
α
, mid-IR, radio continuum and X-ray imaging, plus optical spectroscopy. The galaxies have undergone a recent head-on collision, creating a massive gaseous bridge that is known to be highly turbulent. The bridge contains a complex web of narrow molecular filaments and clumps. The majority of the filaments are devoid of star formation, and fall significantly below the Kennicutt–Schmidt relationship for normal galaxies, especially for the numerous regions undetected in Pa
α
emission. Within the loosely connected filaments and clumps of gas we find regions of high velocity dispersion that appear gravitationally unbound for a wide range of likely values of
X
CO
. Like the “Firecracker” region in the Antennae system, they would require extremely high external dynamical or thermal pressure to stop them dissipating rapidly on short crossing timescales of 2–5 Myr. We suggest that the clouds may be transient structures within a highly turbulent multiphase medium that is strongly suppressing star formation. Despite the overall turbulence in the system, stars seem to have formed in compact hotspots within a kiloparsec-sized extragalactic H
ii
region, where the molecular gas has a lower velocity dispersion than elsewhere, and shows evidence for a collision with an ionized gas cloud. Like the shocked gas in the Stephan’s Quintet group, the conditions in the Taffy bridge shows how difficult it is to form stars within a turbulent, multiphase, gas.
The vascular endothelium acts as a dynamic interface between blood and tissue. TNF-α, a major regulator of inflammation, induces endothelial cell (EC) transcriptional changes, the overall response ...dynamics of which have not been fully elucidated. In the present study, we conducted an extended time-course analysis of the human EC response to TNF, from 30 min to 72 h. We identified regulated genes and used weighted gene network correlation analysis to decipher coexpression profiles, uncovering two distinct temporal phases: an acute response (between 1 and 4 h) and a later phase (between 12 and 24 h). Sex-based subset analysis revealed that the response was comparable between female and male cells. Several previously uncharacterized genes were strongly regulated during the acute phase, whereas the majority in the later phase were IFN-stimulated genes. A lack of IFN transcription indicated that this IFN-stimulated gene expression was independent of de novo IFN production. We also observed two groups of genes whose transcription was inhibited by TNF: those that resolved toward baseline levels and those that did not. Our study provides insights into the global dynamics of the EC transcriptional response to TNF, highlighting distinct gene expression patterns during the acute and later phases. Data for all coding and noncoding genes is provided on the Web site (http://www.endothelial-response.org/). These findings may be useful in understanding the role of ECs in inflammation and in developing TNF signaling-targeted therapies.
Abstract
Although the U-value of glazing has improved significantly in the last decades, the thermal transmittance of windows remains relatively high compared to opaque elements of the thermal shell. ...Consequently, glazing has a relatively low interior surface temperature in the heating season, which can cause thermal discomfort. A novel heated glass element has been developed, allowing for the control of its interior surface temperature. In-situ measurements were conducted on a heated glass element, with the objective to (i) characterize its thermal behaviour, (ii) assess its thermal performance and (iii) to assess its impact on thermal comfort. The examination of heating-up and cooling-down curves of the heated glass element revealed that cooling-down is a slower process (τ
2
of 100 – 145 minutes) than heating-up (τ
2
of 70-85 minutes). In terms of thermal performance, it is shown that most of the heat provided by the heated glass element is effectively directed towards the room, rather than lost to the outdoor environment. The efficiency depends on the temperature difference between interior glass surface and the room, with efficiencies of 58 – 65% reached at surface temperatures of 23 - 25 °C, and efficiencies of 90% reached at surface temperatures of 39 – 43 °C. Comparative measurements of thermal comfort in a room with the heated glazing, and in a room with conventional triple glazing show an improvement in operative temperature.
IMPORTANCE: Pediatric primary posterior intraocular lens (IOL) implantation in children older than 24 months has become the standard of care. Results of the Infantile Aphakia Treatment Study have ...concluded that primary IOL implantation before age 7 months has no advantages over aphakia. The current evidence does not address our understanding of the risks and benefits of primary IOL implantation for children aged 7 to 24 months. OBSERVATIONS: Final optotype acuity, adverse events, refractive growth, strabismus, binocular function, and need for additional surgery were retrospectively reviewed for 14 eyes of 10 patients from November 2001 to June 2012. The records were reviewed for children aged 6 to 24 months; included patients were aged 7 to 22 months. The mean (SD) visual acuity was 0.29 (0.30) logMAR (Snellen equivalent 20/40). The mean follow-up was 5 years. The rate of adverse events was 3 in 14 eyes (21%). Adverse events included lens reproliferation (2 eyes) and lens dislocation (1 eye). The rate of strabismus correction was 4 in 10 patients (40%). The mean (SD) rate of refractive growth at 3 times the age at surgery was −5.80 (3.09) diopters. CONCLUSIONS AND RELEVANCE: The data suggest that primary IOL implantation in this age group has a lower rate of adverse events than reported in the Infantile Aphakia Treatment Study. Additionally, favorable visual outcome was found, similar to that in children undergoing primary IOL implantation when older than 2 years. Primary IOL implantation should be considered in children who require cataract surgery after age 7 months.
Abstract
The new Smart TinyLab (STL) for system integration in the building industry is a lab where building partners and construction-related companies can develop, test, validate and demonstrate ...their products in practice to be as energy-efficient as possible to contribute to formulated CO2 emission reduction targets. STL is located near the Saxion University of Applied Sciences in Enschede and has been operationalized since the spring of 2021. In the lab, one can simulate and assess quantitatively the effect of building products, HVAC components, smart technologies, user-related aspects and the outdoor climate on energy consumption and indoor climate conditions. The lab allows the comparison between theoretical and practical characteristics and energy consumption figures. Together with partners from the construction industry, innovative products, devices and systems in a simulation and field test environment have been tested and validated. During STL′s start-up phase other tiny twin-labs with outdoor setups in Europe were compared. Turning the lab in its entirety to face or be averted from direct sunlight makes STL rather unique in its kind.
We present a Gemini-GMOS spectroscopic study of Hubble Space Telescope (HST)-selected H alpha -emitting regions in Stephan's Quintet (HCG 92), a nearby compact galaxy group, with the aim of ...disentangling the processes of shock-induced heating and star formation in its intra-group medium. The emission-line ratios of the two populations of H alpha -emitters confirm their nature as H II regions (90% of the sample) or molecular gas heated by a shock front propagating at lap300 km s super(-1). Their redshift distribution reveals interesting three-dimensional structure with respect to gas-phase baryons, with no H II regions associated with shocked gas, no shocked regions in the intruder galaxy NGC 7318B, and a sharp boundary between shocks and star formation. We also examine Stephan's Quintet in the context of compact galaxy group evolution, as a paradigm for intermittent star formation histories in the presence of a rich, X-ray-emitting intra-group medium. All spectra are provided as supplemental materials.
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