Intracluster stars in the Virgo cluster core

We have investigated the properties of the diffuse light in the Virgo cluster core region, based on the detection of intracluster planetary nebulae (PNe) in four fields. We eliminate the bias from misclassified faint continuum objects, using improved Monte Carlo simulations, and the contaminations by high redshift Ly$\alpha$ galaxies, using the Ly$\alpha$ luminosity function in blank fields. Recent spectroscopic observations confirm that our photometric PN samples are well-understood. We find that the diffuse stellar population in the Virgo core region is inhomogeneous on scales of 30'-90': there exist significant field-to-field variations in the number density of PNe and the inferred amount of intracluster light, with some empty fields, some fields dominated by extended Virgo galaxy halos, and some fields dominated by the true intracluster component. There is no clear trend with distance from M87. The mean surface luminosity density, its rms variation, and the mean surface brightness of diffuse light in our 4 fields are $\Sigma_B = 2.7 x 10^{6}$ L$_{B\odot}$ arcmin$^{-2}$, ${rms} = 2.1 \times 10^{6}$ L$_{B\odot}$ arcmin$^{-2}$, and $\bar{\mu}_{B}=29.0$ mag arcsec$^{-2}$ respectively. Our results indicate that the Virgo cluster is a dynamically young environment, and that the intracluster component is associated at least partially with local physical processes like galaxy interactions or harassment. We also argue, based on kinematic evidence, that the so-called 'over-luminous' PNe in the halo of M84 are dynamically associated with this galaxy, and must thus be brighter than and part of a different stellar population from the normal PN population in elliptical galaxies.Comment: 31 pages, 6 figure. In press on the Astronomical Journa

Nanoscale Au-In alloy-oxide core-shell particles as electrocatalysts for efficient hydroquinone detection

The presence of hydroquinone (HQ), a phenol ubiquitous in nature and widely used in industry, needs to be monitored because of its toxicity to the environment. Here we demonstrate efficient detection of HQ using simple, fast, and noninvasive electrochemical measurements on indium tin oxide (ITO) electrodes modified with nanoparticles comprising bimetallic Au–In cores and mixed Au–In oxide shells. Whereas bare ITO electrodes show very low activity for the detection of HQ, their modification with Au–In core–shell nanoparticles induces a pronounced shift of the oxidation peak to lower potentials, i.e., facilitated oxidation. The response of the different electrodes was correlated with the initial composition of the bimetallic nanoparticle cores, which in turn determined the amount of Au and In stabilized on the surface of the amorphous Au–In oxide shells available for the electrochemical reaction. While adding core–shell nanostructures with different compositions of the alloy core facilitates the electrocatalytic (reduction-) oxidation of HQ, the activity is highest for particles with AuIn cores (i.e., a Au:In ratio of 1). This optimal system is found to follow a single pathway, the two-electron oxidation of the quinone–hydroquinone couple, which gives rise to high oxidation peaks and is most effective in facilitating the electrode-to-analyte charge transfer and thus detection. The limits of detection (LOD) decreased when increasing the amount of Au exposed on the surface of the amorphous Au–In oxide shells. The LODs were in the range of 10–5–10–6 M and were lower than those obtained using bulk Au.2022-07-72022-07-07Research carried out in part at the Center for Functional Nanomaterials, Brookhaven National Laboratory, which is supported by the U.S. Department of Energy, Office of Basic Energy Sciences, under Contract DE-SC0012704. EB- 14, University of Valladolid (PIF-UVa) Ministerio de Economía, Industria y Competitividad – FEDER (Grant CICYT AGL2012-335

Fossil group origins V. The dependence of the luminosity function on the magnitude gap

In nature we observe galaxy aggregations that span a wide range of magnitude gaps between the two first-ranked galaxies of a system ($\Delta m_{12}$). There are systems with gaps close to zero (e.g., the Coma cluster), and at the other extreme of the distribution, the largest gaps are found among the so-called fossil systems. Fossil and non-fossil systems could have different galaxy populations that should be reflected in their luminosity functions. In this work we study, for the first time, the dependence of the luminosity function parameters on $\Delta m_{12}$ using data obtained by the fossil group origins (FOGO) project. We constructed a hybrid luminosity function for 102 groups and clusters at $z \le 0.25$. We stacked all the individual luminosity functions, dividing them into bins of $\Delta m_{12}$, and studied their best-fit Schechter parameters. We additionally computed a relative luminosity function, expressed as a function of the central galaxy luminosity, which boosts our capacity to detect differences, especially at the bright end. We find trends as a function of $\Delta m_{12}$ at both the bright and faint ends of the luminosity function. In particular, at the bright end, the larger the magnitude gap, the fainter the characteristic magnitude $M^\ast$. We also find differences at the faint end. In this region, the larger the gap, the flatter the faint-end slope $\alpha$. The differences found at the bright end support a dissipationless, dynamical friction-driven merging model for the growth of the central galaxy in group- and cluster-sized halos. The differences in the faint end cannot be explained by this mechanism. Other processes, such as enhanced tidal disruption due to early infall and/or prevalence of eccentric orbits, may play a role. However, a larger sample of systems with $\Delta m_{12} > 1.5$ is needed to establish the differences at the faint end.Comment: 11 pages, 10 figures, accepted for publication in A&

Fossil Groups Origins III. The relation between optical and X-ray luminosities

This study is part of the FOssil Groups Origin (FOGO) project which aims at carrying out a systematic and multiwavelength study of a large sample of fossil systems. Here we focus on the relation between the optical luminosity (Lopt) and X-ray luminosity (Lx). Out of a sample of 28 candidate fossil systems, we consider a sample of 12 systems whose fossil classification has been confirmed by a companion study. They are compared with the complementary sample of 16 systems whose fossil nature is not confirmed and with a subsample of 102 galaxy systems from the RASS-SDSS galaxy cluster survey. Fossil and normal systems span the same redshift range 0<z<0.5 and have the same Lx distribution. For each fossil system, the Lx in the 0.1-2.4 keV band is computed using data from the ROSAT All Sky Survey. For each fossil and normal system we homogeneously compute Lopt in the r-band within the characteristic cluster radius, using data from the SDSS DR7. We sample the Lx-Lopt relation over two orders of magnitude in Lx. Our analysis shows that fossil systems are not statistically distinguishable from the normal systems both through the 2D KS test and the fit of the Lx-Lopt relation. The optical luminosity of the galaxy system does strongly correlate with the X-ray luminosity of the hot gas component, independently of whether the system is fossil or not. We conclude that our results are consistent with the classical "merging scenario" of the brightest galaxy formed via merger/cannibalism of other group galaxies, with conservation of the optical light. We find no evidence for a peculiar state of the hot intracluster medium.Comment: A&A, 12 pages, 4 figures, 3 tables, typos corr. and paper re-numbe

Enose lab made with vacuum sampling: quantitative applications

A lab-made electronic nose (Enose) with vacuum sampling and a sensor array, comprising nine metal oxide semiconductor Figaro gas sensors, was tested for the quantitative analysis of vapor–liquid equilibrium, described by Henry’s law, of aqueous solutions of organic compounds: three alcohols (i.e., methanol, ethanol, and propanol) or three chemical compounds with different functional groups (i.e., acetaldehyde, ethanol, and ethyl acetate). These solutions followed a fractional factorial design to guarantee orthogonal concentrations. Acceptable predictive ridge regression models were obtained for training, with RSEs lower than 7.9, R2 values greater than 0.95, slopes varying between 0.84 and 1.00, and intercept values close to the theoretical value of zero. Similar results were obtained for the test data set: RSEs lower than 8.0, R2 values greater than 0.96, slopes varying between 0.72 and 1.10, and some intercepts equal to the theoretical value of zero. In addition, the total mass of the organic compounds of each aqueous solution could be predicted, pointing out that the sensors measured mainly the global contents of the vapor phases. The satisfactory quantitative results allowed to conclude that the Enose could be a useful tool for the analysis of volatiles from aqueous solutions containing organic compounds for which Henry’s law is applicable.The authors are grateful to the Foundation for Science and Technology (FCT, Portugal) and FED-ER under Programme PT2020 for financial support by national funds FCT/MCTES to CIMO (UID/AGR/00690/2019) and SusTEC (LA/P/0007/2020)info:eu-repo/semantics/publishedVersio

Aquaporin-11 Contributes to TGF-β1-Induced Endoplasmic Reticulum Stress in Human Visceral Adipocytes: Role in Obesity-Associated Inflammation

Aquaporin-11 (AQP11) is expressed in human adipocytes, but its functional role remains unknown. Since AQP11 is an endoplasmic reticulum (ER)-resident protein that transports water, glycerol, and hydrogen peroxide (H2O2), we hypothesized that this superaquaporin is involved in ER stress induced by lipotoxicity and inflammation in human obesity. AQP11 expression was assessed in 67 paired visceral and subcutaneous adipose tissue samples obtained from patients with morbid obesity and normal-weight individuals. We found that obesity and obesity-associated type 2 diabetes increased (p &lt; 0.05) AQP11 mRNA and protein in visceral adipose tissue, but not subcutaneous fat. Accordingly, AQP11 mRNA was upregulated (p &lt; 0.05) during adipocyte differentiation and lipolysis, two biological processes altered in the obese state. Subcellular fractionation and confocal microscopy studies confirmed its presence in the ER plasma membrane of visceral adipocytes. Proinflammatory factors TNF-α, and particularly TGF-β1, downregulated (p &lt; 0.05) AQP11 mRNA and protein expression and reinforced its subcellular distribution surrounding lipid droplets. Importantly, the AQP11 gene knockdown increased (p &lt; 0.05) basal and TGF-β1-induced expression of the ER markers ATF4 and CHOP. Together, the downregulation of AQP11 aggravates TGF-β1-induced ER stress in visceral adipocytes. Owing to its "peroxiporin" properties, AQP11 overexpression in visceral fat might constitute a compensatory mechanism to alleviate ER stress in obesity

Testing the theory of immune selection in cancers that break the rules of transplantation

Modification of cancer cells likely to reduce their immunogenicity, including loss or down-regulation of MHC molecules, is now well documented and has become the main support for the concept of immune surveillance. The evidence that these modifications, in fact, result from selection by the immune system is less clear, since the possibility that they may result from reorganized metabolism associated with proliferation or from cell de-differentiation remains. Here, we (a) survey old and new transplantation experiments that test the possibility of selection and (b) survey how transmissible tumours of dogs and Tasmanian devils provide naturally evolved tests of immune surveillance

Post-ischaemic silencing of p66Shc reduces ischaemia/reperfusion brain injury and its expression correlates to clinical outcome in stroke

In light of the limited repertoire of therapeutical options available for the treatment of ischaemic stroke, the identification of novel potential targets is vital; in this respect, the present study demonstrates that the adaptor protein p66Shc holds this potential as an adjunct therapy to thrombolysis. Post-ischaemic silencing of p66Shc protein yielded beneficial effects in a mouse model of I/R brain injury underlying an interesting translational perspective for this target protein. Further, in proof-of-principle clinical experiments using PBMs, we demonstrate that p66Shc gene expression is transiently increased and that its levels correlate to short-term outcome in ischaemic stroke patients. Although these latter experiments are not directly relevant to the experiments performed in mice and in human endothelial cells, they provide novel important information about p66Shc regulation in stroke patients and set the basis for further investigations aimed at assessing the potential for p66Shc to become a novel therapeutic target as an adjunct of thrombolysis for the management of acute ischaemic strok

Involvement of the TPR2 subdomain movement in the activities of ϕ29 DNA polymerase

The polymerization domain of ϕ29 DNA polymerase acquires a toroidal shape by means of an arch-like structure formed by the specific insertion TPR2 (Terminal Protein Region 2) and the thumb subdomain. TPR2 is connected to the fingers and palm subdomains through flexible regions, suggesting that it can undergo conformational changes. To examine whether such changes take place, we have constructed a ϕ29 DNA polymerase mutant able to form a disulfide bond between the apexes of TPR2 and thumb to limit the mobility of TPR2. Biochemical analysis of the mutant led us to conclude that TPR2 moves away from the thumb to allow the DNA polymerase to replicate circular ssDNA. Despite the fact that no TPR2 motion is needed to allow the polymerase to use the terminal protein (TP) as primer during the initiation of ϕ29 TP–DNA replication, the disulfide bond prevents the DNA polymerase from entering the elongation phase, suggesting that TPR2 movements are necessary to allow the TP priming domain to move out from the polymerase during transition from initiation to elongation. Furthermore, the TPR2-thumb bond does not affect the equilibrium between the polymerization and exonuclease activities, leading us to propose a primer-terminus transference model between both active sites