arXiv subjects

O. Rodriguez

Publications and source records attributed to O. Rodriguez.

8 recordsLinked to original sources

arXiv2021

Optical and magnetic resonance imaging approaches for investigating the tumour microenvironment: state-of-the-art review and future trends

The tumour microenvironment (TME) strongly influences tumorigenesis and metastasis. Two of the most characterized properties of the TME are acidosis and hypoxia, both of which are considered hallmarks of tumours as well as critical factors in response to anticancer treatments. Currently, various imaging approaches exist to measure acidosis and hypoxia in the TME, including magnetic resonance imaging (MRI), positron emission tomography and optical imaging. In this review, we will focus on the latest fluorescent-based methods for optical sensing of cell metabolism and MRI as diagnostic imaging tools applied both in vitro and in vivo. The primary emphasis will be on describing the current and future uses of systems that can measure intra- and extra-cellular pH and oxygen changes at high spatial and temporal resolution. In addition, the suitability of these approaches for mapping tumour heterogeneity, and assessing response or failure to therapeutics will also be covered.

physics.med-ph↗

arXiv2020

Low luminosity Type II supernovae III. SN 2018hwm, a faint event with an unusually long plateau

In this work, we present photometric and spectroscopic data of the low-luminosity Type IIP supernova (SN) 2018hwm. The object shows a faint ($M_r=-15$ mag) and very long ($\sim$130 days) plateau, followed by a 2.7 mag drop in the $r$-band to the radioactive tail. The first spectrum shows a blue continuum with narrow Balmer lines, while during the plateau the spectra show numerous metal lines, all with strong and narrow P-Cygni profiles. The expansion velocities are low, in the 1000-1400 km s$^{-1}$ range. The nebular spectrum, dominated by H$\alpha$ in emission, reveals weak emission from [O I] and [Ca II] doublets. The absolute light curve and spectra at different phases are similar to those of low-luminosity SNe IIP. We estimate that 0.0085 $M_{\odot}$ of $^{56}$Ni mass were ejected, through hydrodynamical simulations. The best fit of the model to the observed data is found for an extremely low explosion energy of 0.075 foe, a progenitor radius of 845 $R_{\odot}$ and a final progenitor mass of 9-10 $M_{\odot}$. Finally, we performed a modeling of the nebular spectrum, to establish the amount of oxygen and calcium ejected. We found a low M($^{16}$O)$\approx 0.02$ $M_{\odot}$, but a high M($^{40}$Ca) of 0.3 $M_{\odot}$. The inferred low explosion energy, the low ejected $^{56}$Ni mass and the progenitor parameters, along with peculiar features observed in the nebular spectrum, are consistent with both an electron-capture SN explosion of a super-asymptotic giant branch star and with a low-energy, Ni-poor iron core-collapse SN from a 10-12 $M_{\odot}$ red supergiant.

astro-ph.SR↗

arXiv2020

Constraints on the Physical Properties of GW190814 through Simulations based on DECam Follow-up Observations by the Dark Energy Survey

On 14 August 2019, the LIGO and Virgo Collaborations detected gravitational waves from a black hole and a 2.6 solar mass compact object, possibly the first neutron star -- black hole (NSBH) merger. In search of an optical counterpart, the Dark Energy Survey (DES) obtained deep imaging of the entire 90 percent confidence level localization area with Blanco/DECam 0, 1, 2, 3, 6, and 16 nights after the merger. Objects with varying brightness were detected by the DES Pipeline and we systematically reduced the candidate counterparts through catalog matching, light curve properties, host-galaxy photometric redshifts, SOAR spectroscopic follow-up observations, and machine-learning-based photometric classification. All candidates were rejected as counterparts to the merger. To quantify the sensitivity of our search, we applied our selection criteria to full light curve simulations of supernovae and kilonovae as they would appear in the DECam observations. Since the source class of the merger was uncertain, we utilized an agnostic, three-component kilonova model based on tidally-disrupted NS ejecta properties to quantify our detection efficiency of a counterpart if the merger included a NS. We find that if a kilonova occurred during this merger, configurations where the ejected matter is greater than 0.07 solar masses, has lanthanide abundance less than $10^{-8.56}$, and has a velocity between $0.18c$ and $0.21c$ are disfavored at the $2\sigma$ level. Furthermore, we estimate that our background reduction methods are capable of associating gravitational wave signals with a detected electromagnetic counterpart at the $4\sigma$ level in $95\%$ of future follow-up observations.

astro-ph.HE↗

arXiv2020

First principles determination of some static and dynamic properties of the liquid 3$d$ transition metals near melting

We report an ab initio molecular dynamics simulation study of several static and dynamic properties of the liquid 3d transition metals. The calculated static structure factors show qualitative agreement with the available experimental data, and its second peak displays an asymmetric shape which suggests a significant local icosahedral short-range order. The dynamical structure reveals propagating density fluctuations whose dispersion relation has been evaluated; moreover, its long wavelength limit is compatible with their respective experimental sound velocity. Results are reported for the longitudinal and transverse current spectral functions as well as for the respective dispersion relations. We also analyze the possible appearance of transverse-like low-energy excitations in the calculated dynamic structure factors. Several transport coefficients have been evaluated and compared with the available experimental data.

cond-mat.soft↗

arXiv2019

SN 2016gsd: An unusually luminous and linear type II supernova with high velocities

We present observations of the unusually luminous Type II supernova (SN) 2016gsd. With a peak absolute magnitude of V = $-$19.95 $\pm$ 0.08, this object is one of the brightest Type II SNe, and lies in the gap of magnitudes between the majority of Type II SNe and the superluminous SNe. Its light curve shows little evidence of the expected drop from the optically thick phase to the radioactively powered tail. The velocities derived from the absorption in H$\alpha$ are also unusually high with the blue edge tracing the fastest moving gas initially at 20000 km s$^{-1}$, and then declining approximately linearly to 15000 km s$^{-1}$ over $\sim$100 d. The dwarf host galaxy of the SN indicates a low-metallicity progenitor which may also contribute to the weakness of the metal lines in its spectra. We examine SN 2016gsd with reference to similarly luminous, linear Type II SNe such as SNe 1979C and 1998S, and discuss the interpretation of its observational characteristics. We compare the observations with a model produced by the JEKYLL code and find that a massive star with a depleted and inflated hydrogen envelope struggles to reproduce the high luminosity and extreme linearity of SN 2016gsd. Instead, we suggest that the influence of interaction between the SN ejecta and circumstellar material can explain the majority of the observed properties of the SN. The high velocities and strong H$\alpha$ absorption present throughout the evolution of the SN may imply a circumstellar medium configured in an asymmetric geometry.

astro-ph.HE↗

arXiv2019

A luminous stellar outburst during a long-lasting eruptive phase first, and then SN IIn 2018cnf

We present the results of the monitoring campaign of the Type IIn supernova (SN) 2018cnf (aka ASASSN-18mr). It was discovered about 10 days before the maximum light (on MJD = 58293.4+-5.7 in the V band, with MV = -18.13+-0.15 mag). The multiband light curves show an immediate post-peak decline with some minor luminosity fluctuations, followed by a flattening starting about 40 days after maximum. The early spectra are relatively blue and show narrow Balmer lines with P Cygni profiles. Additionally, Fe II, O I, He I and Ca II are detected. The spectra show little evolution with time, with intermediate-width features becoming progressively more prominent, indicating stronger interaction of the SN ejecta with the circumstellar medium. The inspection of archival images from the Panoramic Survey Telescope and Rapid Response System (Pan-STARRS) survey has revealed a variable source at the SN position, with a brightest detection in December 2015 at Mr = -14.66+-0.17 mag. This was likely an eruptive phase from the massive progenitor star started from at least mid-2011, and that produced the circumstellar environment within which the star exploded as a Type IIn SN. The overall properties of SN 2018cnf closely resemble those of transients such as SN 2009ip. This similarity favours a massive hypergiant, perhaps a luminous blue variable, as progenitor for SN 2018cnf.

astro-ph.SR↗

arXiv2002

Quasi free electro fission of 238U

We present the result of a theoretical study of the quasi free electrofission of $^{238}$U. The exclusive differential cross sections for the quasi free scattering reaction stage have been calculated in PWIA, using a Macroscopic-Microscopic approach for the description of the proton bound states. The nuclear shape was parametrized in terms of cassinian ovaloids. The equilibrium deformation parameters have been calculated by minimizing the total nuclear energy. In the calculation the axially deformed Woods-Saxon single particle potential was used. The obtained single particle momentum distributions were averaged over the nuclear symmetry axis direction. The occupation numbers were calculated in the BCS approach. The fissility for the single hole excited states of the residual nucleus $^{237}$% Pa was calculated on the statistical theory grounds both without taking into account the pre-equilibrium emission of the particle, and with preequilibrium emission in the framework of the exciton model.

nucl-th↗

arXiv2002

A non extensive approach for DNA breaking by ionizing radiation

Tsallis entropy and a maximum entropy principle allows to reproduce experimental data of DNA double strand breaking by electron and neutron radiation. Analytic results for the probability of finding a DNA segment of length l are obtained reproducing quite well the fragment distribution function experimentally obtained.

cond-mat↗