Destruction of dimethyl ether and methyl formate by collisions with He+^+

To correctly model the abundances of interstellar complex organic molecules (iCOMS) in different environments, both formation and destruction routes should be appropriately accounted for. While several scenarios have been explored for the formation of iCOMs via grain and gas-phase processes, much less work has been devoted to understanding the relevant destruction pathways, with special reference to (dissociative) charge exchange or proton transfer reactions with abundant atomic and molecular ions such as He$^+$, H$_3^+$ and HCO$^+$. By using a combined experimental and theoretical methodology we provide new values for the rate coefficients and branching ratios (BRs) of the reactions of He$^+$ ions with two important iCOMs, namely dimethyl ether (DME) and methyl formate (MF). We also review the destruction routes of DME and MF by other two abundant ions, namely H$_3^+$ and HCO$^+$. Based on our recent laboratory measurements of cross sections and BRs for the DME/MF + He$^+$ reactions over a wide collision energy range, we extend our theoretical insights on the selectivity of the microscopic dynamics to calculate the rate coefficients $k(T)$ in the temperature range from 10 to 298 K. We implement these new and revised kinetic data in a general model of cold and warm gas, simulating environments where DME and MF have been detected. Due to stereodynamical effects present at low collision energies, the rate coefficients, BRs and temperature dependences here proposed differ substantially from those reported in KIDA and UDfA, two of the most widely used astrochemical databases. These revised rates impact the predicted abundances of DME and MF, with variations up to 40% in cold gases and physical conditions similar to those present in prestellar coresComment: accepted for publication in Astronomy and Astrophysics (manuscript no. AA/2018/34585), 10 pages, 3 figure

A Physical Model for the Origin of Quasar Lifetimes

We propose a model of quasar lifetimes in which observational quasar lifetimes and an intrinsic lifetime of rapid accretion are strongly distinguished by the physics of obscuration by surrounding gas and dust. Quasars are powered by gas funneled to galaxy centers, but for a large part of the accretion lifetime are heavily obscured by the large gas densities powering accretion. In this phase, starbursts and black hole growth are fueled but the quasar is buried. Eventually, feedback from accretion energy disperses surrounding gas, creating a window in which the black hole is observable optically as a quasar, until accretion rates drop below those required to maintain a quasar luminosity. We model this process and measure the unobscured and intrinsic quasar lifetimes in a hydrodynamical simulation of a major galaxy merger. The source luminosity is determined from the black hole accretion rate, calculated from local gas properties. We calculate the column density of hydrogen to the source along multiple lines of sight and use these column densities and gas metallicities to determine B-band attenuation of the source. Defining the observable quasar lifetime as the total time with an observed B-band luminosity above some limit L_B,min, we find lifetimes ~10-20 Myr for L_B,min=10^11 L_sun (M_B=-23), in good agreement with observationally determined quasar lifetimes. This is significantly smaller than the intrinsic lifetime ~100 Myr obtained if attenuation is neglected. The ratio of observed to intrinsic lifetime is also strong function of both the limiting luminosity and the observed frequency.Comment: 5 pages, 4 figures, submitted to ApJ Letter

Modulation of pain threshold by virtual body ownership

Appropriate sensorimotor correlations can result in the illusion of ownership of exogenous body parts. Nevertheless, whether and how the illusion of owning a new body part affects human perception, and in particular pain detection, is still poorly investigated. Recent findings have shown that seeing one's own body is analgesic, but it is not known whether this effect is transferable to newly embodied, but exogenous, body parts. In recent years, results from our laboratory have demonstrated that a virtual body can be felt as one's own, provided realistic multisensory correlations

What Color is My Arm? Changes in Skin Color of an Embodied Virtual Arm Modulates Pain Threshold

It has been demonstrated that visual inputs can modulate pain. However, the influence of skin color on pain perception is unknown. Red skin is associated to inflamed, hot and more sensitive skin, while blue is associated to cyanotic, cold skin. We aimed to test whether the color of the skin would alter the heat pain threshold. To this end, we used an immersive virtual environment where we induced embodiment of a virtual arm that was co-located with the real one and seen from a first-person perspective. Virtual reality allowed us to dynamically modify the color of the skin of the virtual arm. In order to test pain threshold, increasing ramps of heat stimulation applied on the participants' arm were delivered concomitantly with the gradual intensification of different colors on the embodied avatar's arm. We found that a reddened arm significantly decreased the pain threshold compared with normal and bluish skin. This effect was specific when red was seen on the arm, while seeing red in a spot outside the arm did not decrease pain threshold. These results demonstrate an influence of skin color on pain perception. This top-down modulation of pain through visual input suggests a potential use of embodied virtual bodies for pain therapy

Testicular biodistribution of silica-gold nanoparticles after intramuscular injection in mice

International audienceWith the continuing development of nanomaterials, the assessment of their potential impact on human health, and especially human reproductive toxicity, is a major issue. The testicular biodistribution of nanoparticles remains poorly studied. This study investigated whether gold-silica nanoparticlescould be detected in mouse testes after intramuscular injection, with a particular focus on their ability to cross the blood– testis barrier. To that purpose, well-characterized 70-nm gold core–silica shell nanoparticles were used to ensure sensitive detection using high-resolution techniques. Testes were collected at different time points corresponding to spermatogenesis stages in mice. Transmission electronmicroscopy and confocal microscopy were used for nanoparticle detection, and nanoparticle quantification was performed by atomic emission spectroscopy. All these techniques showed that no particles were able to reach the testes. Results accorded with the normal histological appearance of testes even at 45 days post sacrifice.High-resolution techniques did not detect 70-nm silica-gold nanoparticles in mouse testes after intramuscular injection.These results are reassuring about the safety of nanoparticles with regard to male human reproduction, especially in the context of nanomedicine

The Evolution of the M-sigma Relation

(Abridged) We examine the evolution of the black hole mass - stellar velocity dispersion (M-sigma) relation over cosmic time using simulations of galaxy mergers that include feedback from supermassive black hole growth. We consider mergers of galaxies varying the properties of the progenitors to match those expected at redshifts z=0-6. We find that the slope of the resulting M-sigma relation is the same at all redshifts considered. For the same feedback efficiency that reproduces the observed amplitude of the M-sigma relation at z=0, there is a weak redshift-dependence to the normalization that results from an increasing velocity dispersion for a given galactic stellar mass. We develop a formalism to connect redshift evolution in the M-sigma relation to the scatter in the local relation at z=0. We show that the scatter in the local relation places severe constraints on the redshift evolution of both the normalization and slope of the M-sigma relation. Furthermore, we demonstrate that cosmic downsizing introduces a black hole mass-dependent dispersion in the M-sigma relation and that the skewness of the distribution about the locally observed M-sigma relation is sensitive to redshift evolution in the normalization and slope. In principle, these various diagnostics provide a method for differentiating between theories for producing the M-sigma relation. In agreement with existing constraints, our simulations imply that hierarchical structure formation should produce the relation with small intrinsic scatter.Comment: 12 pages, 6 figures, version accepted by Ap

Active learning of debugging practices and effects in high schools

openImparare a eseguire il debug è un aspetto difficile, ma essenziale, dell'apprendimento della programmazione e alle scuole superiori spesso non viene insegnato esplicitamente. Seguendo l'algoritmo di "Debugging Wolf-fence" e una piattaforma per potenziare il punto di forza di questo algoritmo; l'obiettivo è proporre agli studenti diverse attività su questo argomento e vedere se ciò può migliorare la loro capacità di debugging.Learning to debug is a difficult, yet essential, aspect of learning to program and in high school often it is not explicitly taught. Following the algorithm of "Wolf-fence debugging" and a platform to enhance the strong point of this algorithm; the goal is to propose at the students different activities on this topic and see if that can improve their ability on debugging

Secular evolution and a non-evolving black hole to galaxy mass ratio in the last 7 Gyr

We present new constraints on the ratio of black hole (BH) mass to total galaxy stellar mass at 0.3<z<0.9 for a sample of 32 type-1 active galactic nuclei (AGNs) from the XMM-COSMOS survey covering the range M_BH/M_sun~10^(7.2--8.7). Virial M_BH estimates based on H_beta are available from the COSMOS Magellan/IMACS survey. We use high-resolution Hubble Space Telescope (HST) imaging to decompose the light of each type-1 AGN and host galaxy, and employ a specially-built mass-to-light ratio to estimate the stellar masses (M_*). The M_BH-M_* ratio shows a zero offset with respect to the local relation for galactic bulge masses, and we also find no evolution in the mass ratio M_BH/M_*=(1+z)^{0.02+-0.34} up to z~0.9. Interestingly, at the high-M_BH end there is a positive offset from the z=0 relation, which can be fully explained by a mass function bias with a cosmic scatter of 0.3, reaffirming that the intrinsic distribution is consistent with zero evolution. From our results we conclude that since z~0.9 no substantial addition of stellar mass is required: the decline in star formation rates and merger activity at z<1 support this scenario. Nevertheless, given that a significant fraction of these galaxies show a disk component, their bulges are indeed undermassive. This is a direct indication that for the last 7 Gyr the only essential mechanism required in order that these galaxies obey the z=0 relation is a redistribution of stellar mass to the bulge, likely driven by secular processes, i.e., internal instabilities and minor merging.Comment: 7 pages, 4 figures, accepted for publication in ApJ Letter

Packed Bed Ca-Cu Looping Process Integrated with a Natural Gas Combined Cycle for Low Emission Power Production

This work investigates the full process design of a natural gas combined cycle integrated with a packed-bed reactor system where a hydrogen rich gas is produced with inherent CO2capture based of the CaO/CaCO3and Cu/CuO chemical loops. The different stages of this Ca-Cu process were modelled with a dynamic 1D pseudo-homogeneous model, proposing a novel reactor configuration allowing to achieve carbon capture efficiency close to 90%. Process simulations of the whole power plant resulted in electric efficiencies of around 48%LHVand SPECCA of 4.7 MJ/kgCO2. Published by Elsevier Ltd

Ongoing Star Formation In AGN Host Galaxy Disks: A View From Core-collapse Supernovae

The normalized radial distribution of young stellar populations (and cold gas) in nearby galactic disks is compared between AGN host galaxies and starforming galaxies (both with Hubble types between S0/a and Scd) by using type II supernovae (SNe) as tracers. A subset of 140 SNe\,II with available supernova position measurements are selected from the SAI-SDSS image catalog by requiring available SDSS spectroscopy data of their host galaxies. Our sample is finally composed of 46 AGNs and 94 starforming galaxies. Both directly measured number distributions and inferred surface density distributions indicate that a) the SNe detected in starforming galaxies follow an exponential law well; b) by contrast, the SNe detected in AGN host galaxies significantly deviate from an exponential law, which is independent of both morphological type and redshift. Specifically, we find a detection deficit around $R_{\mathrm{SN}}/R_{25,\mathrm{cor}}\sim0.5$ and an over-detection at outer region $R_{\mathrm{SN}}/R_{25,\mathrm{cor}}\sim0.6-0.8$. This finding provides a piece of evidence supporting that there is a link between ongoing star formation (and cold gas reservoir) taking place in the extended disk and central AGN activity.Comment: 5 pages, 4 figures, accepted by MNRA