Search

The Multipurpose Detector (MPD) consists of a typical array of sub-detectors to study the nuclear matter originating from the collisions of beams provided by the Nuclotron-based Ion Collider fAcility (NICA). A beam monitoring detector~(BeBe) is proposed for stage 2 of MPD to increase the trigger capabilities. BeBe is constituted of two plastic scintillator disks segmented in 80 cells $\pm~2~m$ away from the interaction point of MPD. Laboratory measurements to obtain the energy resolution of an individual BeBe cell prototype are presented. It is shown that an energy resolution of $22\pm6\%$ can be obtained. Based on Monte Carlo simulations, the trigger efficiencies of the BeBe are presented for p+p collisions at 11~GeV considering a threshold in the energy loss of the charged particles reaching the detector.

One of the must important non-invasive techniques in medicine is the Magnetic Resonance Imaging (MRI), it is used to obtain information of the structure of the human body parts using three dimensional images. The technique to obtain these images is based by the emission of radio waves produced by the protons of the hydrogen atoms in water molecules when placed in a constant magnetic field after they interact with a pulsed radio frequency (RF) current, the spin of the protons are in a spin excited state. When the RF field is turned off, the MRI sensors are able to detect the energy released (RF waves) as the protons realign their spins with the magnetic field. We used a three particles model for the water molecule: the two protons from the hydrogen atoms move around the doubly negatively charged oxygen (unstructured), to describe the total angular momentum. The energy levels from the water molecule are studied in presence of an uniform external magnetic field, which interacts with the proton's spin and orbital angular momentum. The energy is shifted and the degeneration is lifted. To illustrate the results, we provide numerical results for a magnetic field strength commonly used in MRI devices.

This study presents an automated bibliometric analysis of 6569 research papers published in thirteen Brazilian Computer Science Society (SBC) conferences from 1999 to 2021. Our primary goal was to gather data to understand the gender representation in publications in the field of Computer Science. We applied a systematic assignment of gender to 23.573 listed papers authorships, finding that the gender gap for women is significant, with female authors being under-represented in all years of the study.

Gliomas are brain tumors composed of different highly heterogeneous histological subregions. Image analysis techniques to identify relevant tumor substructures have high potential for improving patient diagnosis, treatment and prognosis. However, due to the high heterogeneity of gliomas, the segmentation task is currently a major challenge in the field of medical image analysis. In the present work, the database of the Brain Tumor Segmentation (BraTS) Challenge 2018, composed of multimodal MRI scans of gliomas, was studied. A segmentation methodology based on the design and application of convolutional neural networks (CNNs) combined with original post-processing techniques with low computational demand was proposed. The post-processing techniques were the main responsible for the results obtained in the segmentations. The segmented regions were the whole tumor, the tumor core, and the enhancing tumor core, obtaining averaged Dice coefficients equal to 0.8934, 0.8376, and 0.8113, respectively. These results reached the state of the art in glioma segmentation determined by the winners of the challenge., Comment: 34 pages, 12 tables, 23 figures

The Multipurpose Detector (MPD) is an experimental array, currently under construction, designed to study the nuclear matter created during the collisions that will be provided by the Nuclotron-based Ion Collider fAcility (NICA) at JINR. The MPD-NICA experiment consists of a typical array of particle detectors as those used to study heavy-ion collisions at LHC and RHIC. To increase the trigger capabilities of MPD for stage 2 of NICA operation, a detector conformed by two arrays of 80 plastic scintillator cells each located symmetrically at opposite sides of the interaction point of MPD is proposed (BeBe). Based on Monte Carlo simulations, a discussion of the potential physics performance of BeBe detector is given for triggering tasks and for the resolution in the determination of the event plane reaction and the centrality of the collisions at NICA. Also, laboratory measurements to estimate the time resolution of individual BeBe cells prototypes are presented. It is shown that a time resolution between 0.65 and 1.48 ns can be reached depending on the number of photosensors employed to collect the scintillation photons. The BeBe detector will be complementary to FFD and FHCAL forward detectors., Comment: 30 pages, 25 figures. Submitted to JINST

The concept of a Magnetic Resonance Imaging (MRI) device is based on the emission of radio waves produced by the protons of the hydrogen atoms in water molecules when placed in a constant magnetic field after they interact with a pulsed radio frequency (RF) current. When the RF field is turned on, the protons are brought to a spin excited state. When the RF field is turned off, the MRI sensors are able to detect the energy released as the protons realign their spins with the magnetic field. In this work we provide a simple model to describe the basic physical mechanism responsible for the operation of MRI devices. We model the water molecule in terms of a central force problem, where the protons move around the (unstructured) doubly negatively charged oxygen atom. First, we employ an analytical treatment to obtain the system's wave function as well as its energy levels, which we show are degenerate. Next, the energy levels from the water molecule are studied in the presence of a uniform external magnetic field. As a result, they get shifted and the degeneration is lifted. We provide numerical results for a magnetic field strength commonly used in MRI devices.

The time resolution (TR) is one of the most important characteristic of a detector. For the case of a scintillator, the collection of light also is important, it depends of the effective area of the photo-sensor (\textit{Scorer}). The Photomultipliers Tubes (PMTs), normally, have an effective area greater than the Silicon Photomultipliers (SiPMs), however, due to its voltage of operation, their size or cost, in some cases it can be difficult to work with them. In which case, it is preferable to use SiPMs. The value of TR also depends of the size and geometry of the scintillator, number of photo-sensors and the electronic part.\\ In this work, we study the mean optical photon arrival time distribution (AT) to a Scorer from a SiPM of 6$\times$6~mm$^2$. We define the variation of AT as \textit{the intrinsic time resolution} (ITR). In Geant4, we simulated two different geometries: square and hexagonal, for a BC-404 plastic scintillator coupled to one Scorer. The sources simulated were Sr$^{90}$, Co$^{60}$, Cs$^{137}$, Na$^{22}$ and $\mu^-$ of 1~GeV. It is shown that AT and ITR depends of the geometry and size of the plastic scintillator, the location of the Scorer, the incident particle and its energy. Then, the ITR and therefore the TR is not a constant for a detector. Finally, we show the relation between AT and the deposited energy by the particle incident, which are related in the experiment to the response time event of the detector and the deposited charge by the incident particle, respectively.

Digital analysis of mammographic images is a complementary tool to clinical evaluation, commonly used to identify tumors and/or microcalcifications in mammograms. Recent mammographic equipment, can automatically classify them using this methodology. The difficulty in finding and classifying such areas, arise from different factors such as: image acquisition methodology, excess of brightness, similar physiological and radiological properties of tissues, etc. In this work it is proposed that the numerical computations of fractal dimension and entropy are tools that could be used to automatically segment and distinguish malignant tumors and/or microcalcifications in digital mammograms. The study consisted in segment the image in two areas: background and confirmed malignant tumor and/or microcalcification, to which the fractal dimension and entropy values are calculated and it was found the correlation between them. The analysis was performed on a grayscale re-digitized images from images provided locally by hospital for microcalcifications and from public databases for malignant tumors. From these re-digitized images, it was able to give the exact coordinates as the diagnosis provides. For any image, the highest intensity value was located in the tumor and/or microcalcification area, resulting that the fractal dimension had a higher value than the rest of the image, while the entropy value was lower, due to the uniformity of intensities in these areas. To complete this study, it was performed a data analysis with the set of intensities in each area. This allowed to distinguish between the areas of interest according to the value of the intensities, having a value greater than 3 {\sigma}. Finally, it is shown a technique to visually highlight the malignant tumor and/or microcalcification.

We present the conceptual design for the miniBeBe detector proposed to be installed as a level-0 trigger for the TOF of the NICA-MPD. We discuss the design and the geometrical array of its sensitive parts, the read-out electronics as well as the mechanical support that is envisioned. We also present simulation results for p + p and Bi + Bi collisions to study its capabilities as a function of multiplicity both as a level-0 trigger for the TOF, as well as to serve as a beam-gas interaction veto and to locate the beam-beam interaction vertex., Comment: Version to appear in JINST, 29 pages, 29 figures

We develop herein plasmonic-catalytic Au-IrO$_2$ nanostructures with a morphology optimized for efficient light harvesting and catalytic surface area; the nanoparticles have a dendritic morphology, with closely spaced Au branches all partially covered by an ultrathin (1 nm) IrO$_2$ shell. This nanoparticle architecture optimizes optical features due to the interactions of closely spaced plasmonic branches forming electromagnetic hot spots, and the ultra-thin IrO$_2$ layer maximizes efficient use of this expensive catalyst. This concept was evaluated towards the enhancement of the electrocatalytic performances towards the oxygen evolution reaction (OER) as a model transformation. The OER can play a central role in meeting future energy demands but the performance of conventional electrocatalysts in this reaction is limited by the sluggish OER kinetics. We demonstrate an improvement of the OER performance for one of the most active OER catalysts, IrO$_2$, by harvesting plasmonic effects from visible light illumination in multimetallic nanoparticles. We find that the OER activity for the Au-IrO$_2$ nanodendrites can be improved under LSPR excitation, matching best properties reported in the literature. Our simulations and electrocatalytic data demonstrate that the enhancement in OER activities can be attributed to an electronic interaction between Au and IrO$_2$ and to the activation of Ir-O bonds by LSPR excited hot holes, leading to a change in the reaction mechanism (rate-determinant step) under visible light illumination., Comment: 5 figures

The Latin American Giant Observatory (LAGO) is an extended astroparticle observatory with the goal of studying Gamma Ray Bursts (among other extreme universe phenomena), space weather and atmospheric radiation at ground level. It consists of a network of several Water Cherenkov Detectors (WCD) located at different sites and different latitudes along the American Continent (from Mexico up to the Antarctic region). Another interest of LAGO is to encourage and support the development of experimental basic research in Latin America, mainly with low cost equipment. In the case of Chiapas, Mexico, the experimental astroparticle physics activity was limited, up to now, to data analysis from other detectors located far away from the region. Thanks to the collaboration within LAGO, the deployment of one WCD is ongoing at the Universidad Aut\'onoma de Chiapas (UNACH). This will allow, for the first time in the region, to train students and researchers in the deployment processes. Till now the setup of the signal-processing electronics has been performed and the characterization of the photomultiplier tube is currently being done. The main, short-term goal is to install one WCD on top of the Tacan\'a volcano in Chiapas in a short term. The status of the work is presented., Comment: International Cosmic Ray Conference, Busan, Korea, 10-20 July, 2017 https://pos.sissa.it/301/