Description: Author(s): S. R. Souza, R. Donangelo, W. G. Lynch, and M. B. Tsang The properties of the kinetic energy spectra of light isotopes produced in the breakup of a nuclear source and during the de-excitation of its products are examined. The initial stage, at which the hot fragments are created, is modeled by the statistical multifragmentation model, whereas the Weissko... [Phys. Rev. C 97, 034614] Published Tue Mar 20, 2018

Description: Nature Reviews Cancer 13, 315 (2013). doi:10.1038/nrc3507 Authors: Jeanne L. Becker & Glauco R. Souza Experiments conducted in the microgravity environment of space are not typically at the forefront of the mind of a cancer biologist. However, space provides physical conditions that are not achievable on Earth, as well as conditions that can be exploited to study mechanisms and pathways

Description: Soil mapping across large areas can be enhanced by integrating different methods and data sources. This study merges laboratory, field and remote sensing data to create digital maps of soil suborders based on the Brazilian Soil Classification System, with and without additional textural classification, in an area of 13 000 ha in the state of São Paulo, southeastern Brazil. Data from 289 visited soil profiles were used in multinomial logistic regression to predict soil suborders from geospatial data (geology, topography, emissivity and vegetation index) and visible–near infrared (400–2500 nm) reflectance of soil samples collected at three depths (0–20, 40–60 and 80–100 cm). The derived maps were validated with 47 external observations, and compared with two conventional soil maps at scales of 1:100 000 and 1:20 000. Soil suborders with and without textural classification were predicted correctly for 44 and 52% of the soil profiles, respectively. The derived suborder maps agreed with the 1:100 000 and 1:20 000 conventional maps in 20 and 23% (with textural classification) and 41 and 46% (without textural classification) of the area, respectively. Soils that were well defined along relief gradients (Latosols and Argisols) were predicted with up to 91% agreement, whereas soils in complex areas (Cambisols and Neosols) were poorly predicted. Adding textural classification to suborders considerably degraded classification accuracy; thus modelling at the suborder level alone is recommended. Stream density and laboratory soil reflectance improved all classification models, showing their potential to aid digital soil mapping in complex tropical environments.

Description: We have investigated the ionospheric response close to the subsolar point in South America due to the strong solar flare (X2.8) that occurred on 13-May-2013. The present work discusses the sudden disturbances in the D-region in the form of High Frequency (HF) radio wave blackout recorded in ionograms, the E-region disturbances in the form of the Sq-current and Equatorial electrojet (EEJ) intensifications, and the enhancement and decay in the ionospheric total electron content (TEC) as observed by a network of GNSS receivers, the last of these manifestations constituting the main focuses of this study. The dayside ionosphere showed an abrupt increase of the TEC, with the region of the TEC increase being displaced away from the sub-solar point towards the Equatorial Ionization Anomaly (EIA) crest region. The decay in the ∆TEC following the decrease of the flare EUV flux varied at a slower ratio near the EIA crest than at the sub-solar point. We used the Sheffield University Plasmasphere-Ionosphere Model (SUPIM) to simulate the TEC enhancement and the related variations as arising from the flare enhanced solar EUV flux and soft X-rays. The simulations are compared with the observational data to validate our results, and it is found that a good part of the observed TEC variation features can be accounted for by the model simulation. The combined results from model and observational can contribute significantly to advance our knowledge about ionospheric photochemistry and dynamics needed to improve our predictive capability on the low latitude ionospheric response to solar flares.

Description: Author(s): S. R. Souza, B. V. Carlson, R. Donangelo, W. G. Lynch, and M. B. Tsang The agreement between the fragments' internal and kinetic temperatures with the breakup temperature is investigated using a statistical multifragmentation model, which makes no a priori assumption on the relationship between them. We thus examine the conditions for obtaining such agreement and find … [Phys. Rev. C 92, 024612] Published Mon Aug 17, 2015

Description: In this study, we investigate a novel in vitro model to mimic heterogeneous breast tumors without the use of a scaffold while allowing for cell-cell and tumor-fibroblast interactions. Previous studies have shown that magnetic levitation system under conventional culturing conditions results in the formation of three-dimensional (3D) structures, closely resembling in vivo tissues (fat tissue, vasculature, etc.). Three-dimensional heterogeneous tumor models for breast cancer were designed to effectively model the influences of the tumor microenvironment on drug efficiency. Various breast cancer cells were co-cultured with fibroblasts and then magnetically levitated. Size and cell density of the resulting tumors were measured. The model was phenotypically compared to in vivo tumors and examined for the presence of ECM proteins. Lastly, the effects of tumor stroma in the 3D in vitro model on drug transport and efficiency were assessed. Our data suggest that the proposed 3D in vitro breast tumor is advantageous due to the ability to: (1) form large-sized (millimeter in diameter) breast tumor models within 24 h; (2) control tumor cell composition and density; (3) accurately mimic the in vivo tumor microenvironment; and (4) test drug efficiency in an in vitro model that is comparable to in vivo tumors. Scientific Reports 4 doi: 10.1038/srep06468

Description: In the present work, we investigate the behavior of the equatorial F region zonal plasma drifts over the Peruvian region under magnetically disturbed conditions during two solar minimum epochs, one of them being the recent prolonged solar activity minimum. The study utilizes the vertical and zonal components of the plasma drifts measured by the Jicamarca (11.95° S; 76.87° W) incoherent scatter radar during two events that occurred on 10 April 1997 and 24 June 2008 and model calculation of the zonal drift in a realistic ionosphere simulated by the SUPIM-INPE. Two main points are focused: (1) the connection between electric fields and plasma drifts under prompt penetration electric field during a disturbed periods and (2) anomalous behavior of daytime zonal drift in the absence of any magnetic storm. A perfect anticorrelation between vertical and zonal drifts was observed during the night and in the initial and growth phases of the magnetic storm. For the first time, based on a realistic low latitude ionosphere, we will show, on a detailed quantitative basis, that this anticorrelation is driven mainly by a vertical Hall electric field induced by the primary zonal electric field in the presence of an enhanced nighttime E region ionization. It is shown that an increase in the field line integrated Hall-to-Pedersen conductivity ratio , that can arise from precipitation of energetic particles in the region of the South American Magnetic Anomaly (SAMA), is capable of explaining the observed anti correlation between the vertical and zonal plasma drifts. Evidence for the particle ionization is provided from the occurrence of anomalous sporadic E layers over the low latitude station, Cachoeira Paulista (22.67° S; 44.9° W) – Brazil. It will also be shown that the zonal plasma drift reversal to eastward in the afternoon two hours earlier than its reference quiet time pattern is possibly caused by weakening of the zonal wind system during the prolonged solar minimum period.

Description: In this paper we present the results of a study on the characteristics of large scale wave structure in the equatorial ionospheric F region that serve as precursor to post sunset development of the spread F/plasma bubble irregularities. The study is based on analysis of Digisonde data from three equatorial sites in Brazil (Fortaleza, Sao Luis and Cachimbo) for a period of about two months at a medium solar activity phase. Small amplitude oscillations in the F layer heights, extracted at a number of plasma frequencies, present characteristics as them being generated from upward propagating gravity waves. They represent wave structures in polarization electric field having zonal scale of a few hundred kilometers. Their amplitudes in the afternoon hours undergo amplification towards evening, leading to post sunset development of ESF/plasma bubble irregularities, on a statistical basis. On the days of their larger amplitudes they appear to occur in phase coherence on all days, and correspondingly the evening prereversal vertical drift velocities are larger than on days of the smaller amplitudes of the wave structure that appear at random phase on the different days. The sustenance of these precursor waves structures is supported by the relatively large ratio (approaching unity) of the F-region-to- total field line integrated Pedersen conductivities as calculated using the SUPIM simulation of the low latitude ionosphere. The significant amplification in the wave structure towards sunset and the “phase coherent” nature of their occurrences on different days, are explained tentatively on the basis of the spatial resonance mechanism.

Description: Author(s): S. R. Souza, B. V. Carlson, R. Donangelo, W. G. Lynch, and M. B. Tsang The generalized Fermi breakup model, recently demonstrated to be formally equivalent to the statistical multifragmentation model, if the contribution of excited states is included in the state densities of the former, is implemented. Because this treatment requires application of the statistical mul... [Phys. Rev. C 88, 014607] Published Thu Jul 18, 2013

Description: Nature Protocols 8, 1940 (2013). doi:10.1038/nprot.2013.125 Authors: William L Haisler, David M Timm, Jacob A Gage, Hubert Tseng, T C Killian & Glauco R Souza Recently, biomedical research has moved toward cell culture in three dimensions to better recapitulate native cellular environments. This protocol describes one method for 3D culture, the magnetic levitation method (MLM), in which cells bind with a magnetic nanoparticle assembly overnight to render them magnetic. When