Abstract
We present deep X-ray and radio observations of the fast blue optical transient (FBOT) AT 2020xnd/ZTF 20acigmel at
z
= 0.2433 from 13 days to 269 days after explosion. AT 2020xnd belongs to ...the category of optically luminous FBOTs with similarities to the archetypal event AT 2018cow. AT 2020xnd shows luminous radio emission reaching
L
ν
≈ 8 × 10
29
erg s
−1
Hz
−1
at 20 GHz and 75 days post-explosion, accompanied by luminous and rapidly fading soft X-ray emission peaking at
L
X
≈ 6 × 10
42
erg s
−1
. Interpreting the radio emission in the context of synchrotron radiation from the explosion’s shock interaction with the environment, we find that AT 2020xnd launched a high-velocity outflow (
v
∼ 0.1
c
–0.2
c
) propagating into a dense circumstellar medium (effective
M
̇
≈
10
−
3
M
⊙
yr
−1
for an assumed wind velocity of
v
w
= 1000 km s
−1
). Similar to AT 2018cow, the detected X-ray emission is in excess compared to the extrapolated synchrotron spectrum and constitutes a different emission component, possibly powered by accretion onto a newly formed black hole or neutron star. These properties make AT 2020xnd a high-redshift analog to AT 2018cow, and establish AT 2020xnd as the fourth member of the class of optically luminous FBOTs with luminous multiwavelength counterparts.
Volumetric properties and viscosity of mixtures of a synthetic poly(α-olefin) base oil with polymethacrylate-based polymeric additives have been studied. Two different polymeric additives were ...evaluated at addition levels up to 7 wt %. Density data were collected at 298, 323, 348, 373, and 398 K from 10 to 40 MPa in a variable-volume view cell. Viscosity data were collected at 298, 323, 348, and 373 K from 10 to 40 MPa in a high-pressure rotational viscometer. The density and viscosity data were then modeled simultaneously by coupling the Sanchez–Lacombe equation state with the free volume and the density scaling theories of viscosity. Density data were also used to evaluate the derived thermodynamic properties such as isothermal compressibility, isobaric thermal expansion coefficient, and internal pressure. The variations in the volumetric properties and viscosity are discussed in terms of the nature of the polymeric additive and polymer concentration in the mixture. It is shown that for each oil, density scaling reduces the viscosity values generated at different temperatures and pressures into a master curve. Density scaling parameters provide new insights into the effectiveness of the polymeric additives as viscosity modifiers in terms of addition levels and the temperature sensitivity of viscosity.
We present cosmological constraints from the combination of the full mission nine-year WMAP release and small-scale temperature data from the pre-Planck Atacama Cosmology Telescope (ACT) and South ...Pole Telescope (SPT) generation of instruments. This is an update of the analysis presented in Calabrese et al. Phys. Rev. D 87, 103012 (2013), and highlights the impact on ΛCDM cosmology of a 0.06 eV massive neutrino-which was assumed in the Planck analysis but not in the ACT/SPT analyses-and a Planck-cleaned measurement of the optical depth to reionization. We show that cosmological constraints are now strong enough that small differences in assumptions about reionization and neutrino mass give systematic differences which are clearly detectable in the data. We recommend that these updated results be used when comparing cosmological constraints from WMAP, ACT and SPT with other surveys or with current and future full-mission Planck cosmology. Cosmological parameter chains are publicly available on the NASA’s LAMBDA data archive.
ABSTRACT We present results for Vela C obtained during the 2012 flight of the Balloon-borne Large Aperture Submillimeter Telescope for Polarimetry. We mapped polarized intensity across almost the ...entire extent of this giant molecular cloud, in bands centered at 250, 350, and 500 m. In this initial paper, we show our 500 m data smoothed to a resolution of 2 5 (approximately 0.5 pc). We show that the mean level of the fractional polarization p and most of its spatial variations can be accounted for using an empirical three-parameter power-law fit, , where N is the hydrogen column density and S is the polarization-angle dispersion on 0.5 pc scales. The decrease of p with increasing S is expected because changes in the magnetic field direction within the cloud volume sampled by each measurement will lead to cancellation of polarization signals. The decrease of p with increasing N might be caused by the same effect, if magnetic field disorder increases for high column density sightlines. Alternatively, the intrinsic polarization efficiency of the dust grain population might be lower for material along higher density sightlines. We find no significant correlation between N and S. Comparison of observed submillimeter polarization maps with synthetic polarization maps derived from numerical simulations provides a promising method for testing star formation theories. Realistic simulations should allow for the possibility of variable intrinsic polarization efficiency. The measured levels of correlation among p, N, and S provide points of comparison between observations and simulations.
We present a detailed analysis from new multi-wavelength observations of the exceptional galaxy cluster ACT-CL J0102-4915, likely the most massive, hottest, most X-ray luminous and brightest ...Sunyaev-Zel'dovich (SZ) effect cluster known at redshifts greater than 0.6. The Atacama Cosmology Telescope (ACT) collaboration discovered ACT-CL J0102-4915 as the most significant SZ decrement in a sky survey area of 755 deg super(2). Our Very Large Telescope (VLT)/FORS2 spectra of 89 member galaxies yield a cluster redshift, z = 0.870, and velocity dispersion, sigma sub(gal) = 1321 + or - 106 km s super(-1). Our Chandra observations reveal a hot and X-ray luminous system with an integrated temperature of T sub(X) = 14.5 + or - 0.1 keV and 0.5-2.0 keV band luminosity of L sub(X) = (2.19 + or - 0.11) x 10 super(45) h super(-2) sub(70) erg s super(-1). We obtain several statistically consistent cluster mass estimates; using empirical mass scaling relations with velocity dispersion, X-ray Y sub(X), and integrated SZ distortion, we estimate a cluster mass of M sub(200)a = (2.16 + or - 0.32) x 10 super(15) h super(-1) sub(70) M sub(middot in circle). We constrain the stellar content of the cluster to be less than 1% of the total mass, using Spitzer IRAC and optical imaging. The Chandra and VLT/FORS2 optical data also reveal that ACT-CL J0102-4915 is undergoing a major merger between components with a mass ratio of approximately 2 to 1. The X-ray data show significant temperature variations from a low of 6.6 + or - 0.7 keV at the merging low-entropy, high-metallicity, cool core to a high of 22 + or - 6 keV. We also see a wake in the X-ray surface brightness and deprojected gas density caused by the passage of one cluster through the other. Archival radio data at 843 MHz reveal diffuse radio emission that, if associated with the cluster, indicates the presence of an intense double radio relic, hosted by the highest redshift cluster yet. ACT-CL J0102-4915 is possibly a high-redshift analog of the famous Bullet cluster. Such a massive cluster at this redshift is rare, although consistent with the standard LambdaCDM cosmology in the lower part of its allowed mass range. Massive, high-redshift mergers like ACT-CL J0102-4915 are unlikely to be reproduced in the current generation of numerical N-body cosmological simulations.
The development of advanced lubricants to improve vehicle fuel efficiency can appear to be as simple as lowering the viscosity and frictional properties of a fluid. However, applied research studies ...have shown that it is quite difficult to quantify the fuel efficiency properties of advanced lubricants in vehicles. A review of the historical research predominantly performed in North America in this area reveals that there are many factors to consider in order to demonstrate the effectiveness of advanced lubricants. First, the methodology used to measure vehicle fuel efficiency will impact the results since there are many factors not related to the lubricant which will influence vehicle fuel efficiency. Second, developing advanced fuel-efficient lubricants under well controlled conditions overlooks the issue that lubricant properties such as viscosity and friction affect the operating conditions encountered by the lubricant in the vehicle. Finally, the physical properties of lubricants that historically control fuel economy do not have the same effect on fuel efficiency in all vehicles. The proper vehicle or system level test needs to be selected to properly assess the benefits of new advanced lubricants.
Temperature and pressure effects on density and viscosity are reported for six base oils consisting of four mineral oils and two synthetic oils composed of poly(α-olefins). Using a variable-volume ...view cell, density data were collected at 298, 323, 348, 373, and 398 K from 10 to 40 MPa. The data were then fit to the Sanchez–Lacombe equation of state and used to determine isothermal compressibility, isobaric thermal expansion coefficient, and internal pressure. Compressibility and internal pressure were found to vary based on composition, specifically with cycloalkane content. Viscosity data were collected as a function of temperature, pressure, and rotational speed using a custom-built high pressure rotational viscometer. Data were collected at 298, 323, 348, and 373 K from 10 to 40 MPa at rotational speeds of 300–800 rpm. A free-volume model was used to model the viscosity and relate the viscous effects to density.
We measured the cross-correlation between galaxy weak lensing data from the Kilo Degree Survey (KiDS-1000, DR4) and cosmic microwave background (CMB) lensing data from the Atacama Cosmology Telescope ...(ACT, DR4) and the Planck Legacy survey. We used two samples of source galaxies, selected with photometric redshifts, (0.1 < z(B) < 1.2) and (1.2 < z(B) < 2), which produce a combined detection significance of the CMB lensing and weak galaxy lensing cross-spectrum of 7.7σ. With the lower redshift galaxy sample, for which the cross-correlation was detected at a significance of 5.3σ, we present joint cosmological constraints on the matter density parameter, Ω(m), and the matter fluctuation amplitude parameter, σ(8), marginalising over three nuisance parameters that model our uncertainty in the redshift and shear calibration as well as the intrinsic alignment of galaxies. We find our measurement to be consistent with the best-fitting flat ΛCDM cosmological models from both Planck and KiDS-1000. We demonstrate the capacity of CMB weak lensing cross-correlations to set constraints on either the redshift or shear calibration by analysing a previously unused high-redshift KiDS galaxy sample (1.2 < z(B) < 2), with the cross-correlation detected at a significance of 7σ. This analysis provides an independent assessment for the accuracy of redshift measurements in a regime that is challenging to calibrate directly owing to known incompleteness in spectroscopic surveys.
Cyclin-dependent kinase 4/6 (CDK4/6) inhibitors are an established treatment in estrogen receptor-positive breast cancer and are currently in clinical development in melanoma, a tumor that exhibits ...high rates of CDK4 activation. We analyzed melanoma cells with acquired resistance to the CDK4/6 inhibitor palbociclib and demonstrate that the activity of PRMT5, a protein arginine methyltransferase and indirect target of CDK4, is essential for CDK4/6 inhibitor sensitivity. By indirectly suppressing PRMT5 activity, palbociclib alters the pre-mRNA splicing of MDM4, a negative regulator of p53, leading to decreased MDM4 protein expression and subsequent p53 activation. In turn, p53 induces p21, leading to inhibition of CDK2, the main kinase substituting for CDK4/6 and a key driver of resistance to palbociclib. Loss of the ability of palbociclib to regulate the PRMT5–MDM4 axis leads to resistance. Importantly, combining palbociclib with the PRMT5 inhibitor GSK3326595 enhances the efficacy of palbociclib in treating naive and resistant models and also delays the emergence of resistance. Our studies have uncovered a mechanism of action of CDK4/6 inhibitors in regulating the MDM4 oncogene and the tumor suppressor, p53. Furthermore, we have established that palbociclib inhibition of the PRMT5–MDM4 axis is essential for robust melanoma cell sensitivity and provide preclinical evidence that coinhibition of CDK4/6 and PRMT5 is an effective and well-tolerated therapeutic strategy. Overall, our data provide a strong rationale for further investigation of novel combinations of CDK4/6 and PRMT5 inhibitors, not only in melanoma but other tumor types, including breast, pancreatic, and esophageal carcinoma.
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