arXiv subjects

Maria Lopes

Publications and source records attributed to Maria Lopes.

8 recordsLinked to original sources

arXiv2026

First tomographic measurements of the angular clustering and bias of photometric quasars from S-PLUS

We investigate the quasar clustering in the QuCatS photometric catalog, constructed from the fourth data release of the Southern Photometric Local Universe Survey (S-PLUS). The quasar sample for this study consists of $23,402$ quasars, spanning the redshift interval $1.1 \leq z_{\rm phot} \leq 2.6$, which we divided into four bins for our tomographic analyses. In each bin, we measured the two-point angular correlation function and compared it with theoretical predictions for the clustering of dark matter in the flat-$\Lambda$CDM cosmological model. We then estimate the effective linear bias in each bin that best fits the data, obtaining $b_{Q}(z_{\rm eff}=1.26)=2.17^{+0.30}_{-0.35}$, $b_{Q}(z_{\rm eff}=1.63)=2.67^{+0.36}_{-0.42}$, $b_{Q}(z_{\rm eff}=2.04)=3.29^{+0.52}_{-0.62}$, and $b_{Q}(z_{\rm eff}=2.38)=4.05^{+0.71}_{-0.86}$. These measurements are consistent with previous analyses in the literature. Moreover, the evolution of the bias agrees well with the $b(z)$ parameterization proposed by \cite{laurent2017}. Our measurements constitute the first cosmological study of the tomographic clustering of photometric quasars provided by the S-PLUS dataset, contributing to the mapping of the evolution of linear bias and paving the way for future analyses of data releases with larger datasets. In addition, our study also serves as a consistency test for the calibration procedure of the photometric redshift probability distributions of the quasars in the QuCatS catalog.

astro-ph.CO↗

arXiv2026

LiDRoSIS: An Automated MATLAB-Python Platform for Image Processing and Quantitative Analysis of Lipid Droplets and ROS in Irradiated Cells

LiDRoSIS is an automated MATLAB-Python software suite for the segmentation and quantification of lipid droplets (LDs) and reactive oxygen species (ROS) in fluorescence microscopy images of irradiated A549 and MCF7 cells exposed to gold-based nanoparticles. It combines classical image processing algorithms with statistical post-analysis through a companion Python tool, StatLysis. The platform enables reproducible, high-throughput analysis of morphological and spectral parameters linked to nanoparticle-enhanced radiobiological responses. By bridging imaging and quantitative analytics, LiDRoSIS provides a robust framework for nanomedicine and radiation biology research.

physics.med-ph↗

arXiv2025

Probing the Cosmic Distance Duality Relation via Non-Parametric Reconstruction for High Redshifts

We test the validity of the cosmic distance duality relation (CDDR) by combining angular diameter distance and luminosity distance measurements from recent cosmological observations. For the angular diameter distance, we use data from transverse baryon acoustic oscillations and galaxy clusters. On the other hand, the luminosity distance is obtained from Type Ia supernovae in the Pantheon+ sample and from quasar catalogs. To reduce the large dispersion in quasar luminosity distances, we apply a selection criterion based on their deviation from the $\Lambda$CDM model and implement a binning procedure to suppress statistical noise. We reconstruct the CDDR using Gaussian Processes, a non-parametric supervised machine learning method. Our results show no significant deviation from the CDDR within the $2\sigma$ confidence level across the redshift range explored, supporting its validity even at high redshifts.

astro-ph.CO↗

arXiv2025

Probing cosmic isotropy: Hubble constant and matter density large-angle variations with the Pantheon+SH0ES data

In this study we investigate potential large-angle anisotropies in the angular distribution of the cosmological parameters $H_0$ (the Hubble constant) and $\Omega_m$ (the matter density) in the flat-$\Lambda$CDM framework, using the Pantheon+SH0ES supernovae catalog. For this we perform a directional analysis by dividing the celestial sphere into a set of directions, and estimate the best-fit cosmological parameters across the sky using a MCMC approach. Our results show a dominant dipolar pattern for both parameters in study, suggesting a preferred axis in the universe expansion and in the distribution of matter. However, we also found that for $z \gtrsim 0.015$, this dipolar behavior is not statistically significant, confirming the expectation -- in the $\Lambda$CDM scenario -- of an isotropic expansion and a uniform angular distribution of matter (both results at $1\,\sigma$ confidence level). Nevertheless, for nearby supernovae, at distances $\lesssim 60$ Mpc or $z \lesssim 0.015$, the peculiar velocities introduce a highly significant dipole in the angular distribution of $H_0$. Furthermore, we perform various robustness tests that support our findings, and consistency tests of our methodology.

astro-ph.CO↗

arXiv2024

Dipolar fluence distribution of statistically isotropic FERMI gamma-ray bursts

We investigated the large-angle distribution of the gamma-ray bursts (GRBs) from the updated FERMI/GBM catalog to probe the statistical isotropy of these astrophysical transient events. We also studied the angular distribution of the GRB fluence as a way to explore whether this radiative feature shows some preferred direction on the sky that suggest their origin. Our model-independent approach performed a directional analysis of the updated FERMI/GBM catalog. The statistical significance of our results is obtained by comparison with a large set of statistically isotropic samples of cosmic objects, with the same features of the FERMI data. Our analyses confirm that the angular distribution of the FERMIGRB is statistically isotropic on the celestial sphere. Moreover, analyzing the directional distribution of the FERMIGRB fluence, that is, the median GRB fluence in a set of directions that scans the celestial sphere, we found that this astrophysical property exhibits a net dipolar structure with a directional preference for latitudes near the Galactic plane. However, additional studies show that this directional preference is not correlated with the Milky Way Galactic plane, which suggests that the GRB dataset, and its fluence dipolar structure, are extra-Galactic in origin. Interestingly, the analyses of the BATSE Channel 4 fluence data, that is, those GRBs from BATSE with energy $>$ 300 keV, reveal that its dipole direction is very well aligned with the cosmic microwave background dipole.

astro-ph.HE↗

arXiv2024

Measuring the matter fluctuations in the Local Universe with the ALFALFA catalog

The standard model of cosmology describes the matter fluctuations through the matter power spectrum, where $\sigma_{8} \equiv \sigma_{8,0} \equiv \sigma_{8}(z = 0)$, defined at the scale of $8 h^{-1}$ Mpc, acts as a normalisation parameter. Currently, the literature reports measurements of $\sigma_{8}$ analysing different cosmic tracers, where some of these results were obtained assuming a fiducial cosmology. In this study we measure, in a model-independent approach, the matter fluctuations in the Local Universe using HI extragalactic sources mapped by the ALFALFA survey. Our analyses allow us to test the standard cosmological model under extreme conditions in the highly non-linear Local Universe, quantifying the amplitude of the matter fluctuations there. Our work directly measures $\sigma_{8}$ using the 3-dimensional distances of the HI sources determined by the ALFALFA survey without assuming a fiducial cosmology, resulting in a robust model-independent measurement of $\sigma_{8}$. Our methodology involves the construction of suitable mock catalogues to simulate the large scale structure features observed in the data, applying the 2-point correlation function, and making use of Markov Chain Monte Carlo methods to estimate the parameters. Analysing these data we measure $\sigma_8 = 0.78 \pm 0.04$ for $h = 0.6727$, $\sigma_8 = 0.80 \pm 0.05$ for $h = 0.698$, and $\sigma_8 = 0.83 \pm 0.05$ for $h = 0.7304$. Considering the data pairs $(\sigma_8, H_0)$ from the Planck CMB and Atacama Cosmology Telescope (ACT) CMB-lensing analyses, our measurement agrees with them within $1\,\sigma$ confidence level. From a model-independent perspective, we find that the scale where the matter fluctuation is $1$ is $R = 7.2 \pm 1.5~\text{Mpc}$.

astro-ph.CO↗

arXiv2024

Bulk Flow Motion Detection in the Local Universe with Pantheon$+$ Type Ia Supernovae

The {\em bulk flow} in the Local Universe is a collective phenomenon due to the peculiar motions of matter structures, which, instead of moving in random directions, appears to follow an approximate dipole velocity flow. We apply a directional analysis to investigate, through the Hubble-Lema\^{\i}tre diagram, the angular dependence of the Hubble constant $H_0$ of a sample of Type Ia Supernovae from the Pantheon+ catalog in the Local Universe ($0.015 \le z \le 0.06$). We perform a directional analysis that reveals a statistically significant dipole variation of $H_0$, at more than $99.9\%$ confidence level, showing that matter structures follow a dipole bulk flow motion towards $(l,b) = (326.^\circ1 \pm 11.^\circ2,27.^\circ8 \pm 11.^\circ2)$, close to the Shapley supercluster $(l_{\scalebox{0.6}{Shapley}},b_{\scalebox{0.6}{Shapley}}) = (311.^\circ5, 32.^\circ3)$, with velocity $132.14 \pm 109.3$ km s$^{-1}$ at the effective distance $102.83 \pm 10.2$~Mpc. Interestingly, the antipodal direction of this dipole points close to the Dipole Repeller structure. Our analyses confirm that the gravitational dipole system Shapley-Dipole Repeller explains well the observed bulk flow velocity field in the Local Universe. Furthermore, we performed robustness tests that support our results. Additionally, our approach provides a measurement of the Hubble constant $H_0 = 70.39 \pm 1.4$~\text{km s$^{-1}$ Mpc$^{-1}$}, at the effective distance $102.8$~Mpc, $z \simeq 0.025$. Note that this value was obtained using the first order approximation of the Hubble law because our methodology is model-independent. If one assumes, for instance, cosmography at second order with the $\Lambda$CDM value $q_0 = -0.55$, which is a model-dependent hypothesis, then $H_0 = 72.6 \pm 1.5$ km s$^{-1}$ Mpc$^{-1}$, but our results: bulk flow velocity, dipole direction and its statistical significance remain the same.

astro-ph.CO↗

arXiv2018

The long non-coding RNA HOTAIR is transcriptionally activated by HOXA9 and is an independent prognostic marker in patients with malignant glioma

The lncRNA HOTAIR has been implicated in several human cancers. Here, we evaluated the molecular alterations and upstream regulatory mechanisms of HOTAIR in glioma, the most common primary brain tumors, and its clinical relevance. HOTAIR gene expression, methylation, copy-number and prognostic value were investigated in human gliomas integrating data from online datasets and our cohorts. High levels of HOTAIR were associated with higher grades of glioma, particularly IDH wild-type cases. Mechanistically, HOTAIR was overexpressed in a gene dosage-independent manner, while DNA methylation levels of particular CpGs in HOTAIR locus were associated with HOTAIR expression levels in GBM clinical specimens and cell lines. Concordantly, the demethylating agent 5-Aza-2'-deoxycytidine affected HOTAIR transcriptional levels in a cell line-dependent manner. Importantly, HOTAIR was frequently co-expressed with HOXA9 in high-grade gliomas from TCGA, Oncomine, and our Portuguese and French datasets. Integrated in silico analyses, chromatin immunoprecipitation, and qPCR data showed that HOXA9 binds directly to the promoter of HOTAIR. Clinically, GBM patients with high HOTAIR expression had a significantly reduced overall survival, independently of other prognostic variables. In summary, this work reveals HOXA9 as a novel direct regulator of HOTAIR, and establishes HOTAIR as an independent prognostic marker, providing new therapeutic opportunities to treat this highly aggressive cancer.

q-bio.GN↗