Imaging Ferromagnetic Tracers With An Ac Biosusceptometer

The aim of this work was to study the feasibility of obtaining images of the distribution of ferromagnetic tracers using an ac biosusceptometer (ACB). The images were generated by mapping the response of the ACB at short distances due to the presence of a ferrite powder dispersed in a planar gel matrix with different shapes. The ACB was scanned over the sample and the voltages generated by the variation in ferrite concentration were sampled. Methods to render and image the distribution of ferromagnetic particles were studied. The generalized Wiener parametric method gave the best results. The system has a potential to be used in functional images of the gastrointestinal tract where a moderate resolution is required. We conclude that this biomagnetic method can be successfully used to generate planar functional images of magnetic particles in the near field. © 2000 American Institute of Physics.71625322538Erol, R.A., Cherian, P., Smallwood, R.H., Brown, B.H., Bardhan, K.D., (1996) Physiol. Meas., 17, pp. A141Ikeya, M., Ishii, H., (1990) J. Magn. Reson., 88, p. 130Smith, C.M., Stevens, A.D., (1994) Br. J. Radiol., 67, p. 1186Roth, B.J., Sepulveda, N.G., Wikswo J.P., Jr., (1989) J. Appl. Phys., 65, p. 361Moreira, M., Murta, L.O., Baffa, O., (1994) Phys. Med. Biol., 39 A, p. 633Miranda, J.R.A., Baffa, O., Oliveira, R.B., Matsuda, N.M., (1992) Med. Phys., 19, p. 445Baffa, O., Oliveira, R.B., Miranda, J.R., Troncon, L.E.A., (1995) Med. Biol. Eng. Comput., 33, p. 353Oliveira, R.B., Baffa, O., Troncon, L.E.A., Miranda, J.R.A., Cambrea, C.R., (1996) Eur. J. Gastroent. Hepatol., 8, p. 491Miranda, J.R.A., Oliveira, R.B., Sousa, P.L., Braga, F.J.H., Baffa, O., (1997) Phys. Med. Biol., 42, p. 1791Daghastanli, N.A., Braga, F.J.H.N., Oliveira, R.B., Baffa, O., (1998) Physiol. Meas., 19, p. 413Forsman, M., Hultin, L., Abrahamsson, H., (1995) Biomagnetism: Fundamental Research and Clinical Applications. Studies in Applied Electromagnetics and Mechanics, 7, p. 739. , edited by C. Baumgartner, L. Deecke, G. Stroink, and S. J. Williamson Elsevier, AmsterdamBasile, M., Neri, M., Carriero, A., Casciardi, S., Comani, S., Del Gratta, C., Donate, L.G., Romani, G.L., (1992) Dig. Dis. Scie., 37, p. 1537Bruno, A.C., (1997) J. Appl. Phys., 82, p. 1Cruvinel, P.E., Cesareo, R., Crestana, S., Mascarenhas, S., (1990) IEEE Trans. Instrum. Meas., 39, p. 745Lim, J.S., (1990) Two-Dimensional Signal and Image Processing, , Prentice-Hall, Englewood Cliffs, NJJ. P. Wikswo, Jr., N. G. Sepulveda, and I. M. Thomas, Ref. 11, p. 789Tan, S., Ma, Y.P., Smith, I.M., Wikswo J.P., Jr., (1996) IEEE Trans. Magn., 32, p. 230Weber, E., (1951) Electromagnetic Fields: Theory and Applications, Mapping of Magnetic Fields, 1. , Wiley, New YorkSpiegel, M.R., (1990) Mathematical Handbook of Formulas and Tables, , McGraw-Hill, New YorkBruno, A.C., Costa Ribeiro, P., Von Der Wied, J.P., Symko, O., (1986) J. Appl. Phys., 59, p. 2584Vrba, J., Fife, A.A., Burbank, M., Weinberg, H., Bricket, P.A., (1982) Can. J. Phys., 60, p. 106

TMS with fast and accurate electronic control : Measuring the orientation sensitivity of corticomotor pathways

Background: Transcranial magnetic stimulation (TMS) coils allow only a slow, mechanical adjustment of the stimulating electric field (E-field) orientation in the cerebral tissue. Fast E-field control is needed to synchronize the stimulation with the ongoing brain activity. Also, empirical models that fully describe the relationship between evoked responses and the stimulus orientation and intensity are still missing. Objective: We aimed to (1) develop a TMS transducer for manipulating the E-field orientation electronically with high accuracy at the neuronally meaningful millisecond-level time scale and (2) devise and validate a physiologically based model describing the orientation selectivity of neuronal excitability. Methods: We designed and manufactured a two-coil TMS transducer. The coil windings were computed with a minimum-energy optimization procedure, and the transducer was controlled with our custommade electronics. The electronic E-field control was verified with a TMS characterizer. The motor evoked potential amplitude and latency of a hand muscle were mapped in 3 degrees steps of the stimulus orientation in 16 healthy subjects for three stimulation intensities. We fitted a logistic model to the motor response amplitude. Results: The two-coil TMS transducer allows one to manipulate the pulse orientation accurately without manual coil movement. The motor response amplitude followed a logistic function of the stimulus orientation; this dependency was strongly affected by the stimulus intensity. Conclusion: The developed electronic control of the E-field orientation allows exploring new stimulation paradigms and probing neuronal mechanisms. The presented model helps to disentangle the neuronal mechanisms of brain function and guide future non-invasive stimulation protocols. (C) 2022 The Authors. Published by Elsevier Inc.Peer reviewe

The outburst of an embedded low-mass YSO in L1641

Strong outbursts in very young and embedded protostars are rare and not yet fully understood. They are believed to originate from an increase of the mass accretion rate onto the source. We report the discovery of a strong outburst in a low-mass embedded young stellar object (YSO), namely 2MASS-J05424848-0816347 or [CTF93]216-2, as well as its photometric and spectroscopic follow-up. Using near- to mid-IR photometry and NIR low-resolution spectroscopy, we monitor the outburst, deriving its magnitude, duration, as well as the enhanced accretion luminosity and mass accretion rate. [CTF93]216-2 increased in brightness by ~4.6, 4.0, 3.8, and 1.9 mag in the J, H, Ks bands and at 24 um, respectively, corresponding to an L_bol increase of ~20 L_sun. Its early spectrum, probably taken soon after the outburst, displays a steep almost featureless continuum, with strong CO band heads and H_2O broad-band absorption features, and Br gamma line in emission. A later spectrum reveals more absorption features, allowing us to estimate T_eff~3200 K, M~0.25 M_sun, and mass accretion rate~1.2x10^{-6} M_sun yr^{-1}. This makes it one of the lowest mass YSOs with a strong outburst so far discovered.Comment: To be published in A&A letter; 5 pages, 4 figure

Pulsar Searches with the SKA

The Square Kilometre Array will be an amazing instrument for pulsar astronomy. While the full SKA will be sensitive enough to detect all pulsars in the Galaxy visible from Earth, already with SKA1, pulsar searches will discover enough pulsars to increase the currently known population by a factor of four, no doubt including a range of amazing unknown sources. Real time processing is needed to deal with the 60 PB of pulsar search data collected per day, using a signal processing pipeline required to perform more than 10 POps. Here we present the suggested design of the pulsar search engine for the SKA and discuss challenges and solutions to the pulsar search venture.Comment: 4 pages, 1 figure. To be published in Proceedings of IAU Symposium 337: Pulsar Astrophysics - The Next 50 Year

Molecular jets driven by high-mass protostars: a detailed study of the IRAS 20126+4104 jet

We present here an extensive analysis of the protostellar jet driven by IRAS 20126+4104, deriving the kinematical, dynamical, and physical conditions of the H2 gas along the flow. The jet has been investigated by means of near-IR H2 and [FeII] narrow-band imaging, high resolution spectroscopy of the 1-0S(1) line (2.12 um), NIR (0.9-2.5 um) low resolution spectroscopy, along with ISO-SWS and LWS spectra (from 2.4 to 200 um). The flow shows a complex morphology. In addition to the large-scale jet precession presented in previous studies, we detect a small-scale wiggling close to the source, that may indicate the presence of a multiple system. The peak radial velocities of the H2 knots range from -42 to -14 km s^-1 in the blue lobe, and from -8 to 47 km s^-1 in the red lobe. The low resolution spectra are rich in H_2 emission, and relatively faint [FeII] (NIR), [OI] and [CII] (FIR) emission is observed in the region close to the source. A warm H2 gas component has an average excitation temperature that ranges between 2000 K and 2500 K. Additionally, the ISO-SWS spectrum reveals the presence of a cold component (520 K), that strongly contributes to the radiative cooling of the flow and plays a major role in the dynamics of the flow. The estimated L(H2) of the jet is 8.2+/-0.7 L_sun, suggesting that IRAS20126+4104 has an accretion rate significantly increased compared to low-mass YSOs. This is also supported by the derived mass flux rate from the H2 lines (Mflux(H2)~7.5x10^-4 M_sun yr^-1). The comparison between the H2 and the outflow parameters strongly indicates that the jet is driving, at least partially, the outflow. As already found for low-mass protostellar jets, the measured H2 outflow luminosity is tightly related to the source bolometric luminosity.Comment: 16 pages, 12 figures. A&A accepte

Sergio Mascarenhas a polymath in physics.

Sergio Mascarenhas was born in Rio de Janeiro on May 2, 1928, and sadly passed away on May 31, 2021, at the age of 93, after a prolifc life dedicated to developing science and technology in Brazil. Sergio Mascarenhas is one of the founding fathers of condensed matter physics in Brazil. He was a student of the Joaquim da Costa Ribeiro at Universidade do Brasil in Rio de Janeiro. He published his frst papers working on the thermodieletric efect, discovered by Costa Ribeiro. Mascarenhas was the one who called the new phenomenon the Costa Ribeiro efect. He took the frst steps in his academic career in 1955 by moving from Rio de Janeiro, at the time, the country’s capital and principal city, to a small city in the inland of the state of Sao Paulo, São Carlos, when the University of Sao Paulo was expanding its activities beyond the city of Sao Paulo. At that time, Sao Carlos was the host of a promising engineering school. Sergio was hired at the Physics Department and from the very beginning was doing research in condensed matter. This was of-stream at that moment, when the most prestigious areas of physics research were nuclear, high energy, and theoretical physics, and solid-state physics was considered as a second-class research area. He followed the steps of Joaquim da Costa Ribeiro, his mentor in Rio de Janeiro, working in the same class of problems. Of course, this was what was possible to do with the limited experimental resources available. Nevertheless, Mascarenhas published, as a sole author, an important paper in 1970 (S. Mascarenhas (1970) Charge and polarization storage n solids, Radiation Efects: Incorporating Plasma Science and Plasma Technology, 4:2, 263–270, https://doi.org/10.1080/00337577008242012), which summarizes the research he had done. In the paper, he reported on the study of the Costa Ribeiro efect (charge storage during phase changes), photo and thermo electrets (charge and polarization storage due to dipoles, space charge, or electronic efects associated with trapping), and ferroelectricity (in this case only related to ice). Thus, one can appreciate the breadth of studies he pursued and the vast network of collaborators he developed in his career. This is an important point to underline. Sergio always thought of research as a collaborative enterprise and loved sharing ideas and working with research teams

BRSMG Predileta: nova cultivar de arroz irrigado para as várzeas mineiras.

A BRSMG Predileta é originária do cruzamento entre as linhagens CNAx 4267 e CNA 6080, realizado pela Embrapa Arroz e Feijão em 1988. No período de 1989/90 a 1995/96, as populações segregantes foram conduzidas utilizando-se os métodos genealógicos e massal, selecionando-se uma linhagem que foi registrada no BAG da unidade com o código de CNA 8575

Peculiar Motions in the Region of the Ursa Major Supercluster of Galaxies

We have investigated the peculiar motions of clusters of galaxies in the Ursa Major (UMa) supercluster and its neighborhood. Based on SDSS (Sloan Digital Sky Survey) data, we have compiled a sample of early-type galaxies and used their fundamental plane to determine the cluster distances and peculiar velocities. The samples of early-type galaxies in the central regions (within R_200) of 12 UMa clusters of galaxies, in three main subsystems of the supercluster -- the filamentary structures connecting the clusters, and in nine clusters from the nearest UMa neighborhood have similar parameters. The fairly high overdensity (3 by the galaxy number and 15 by the cluster number) suggests that the supercluster as a whole is gravitationally bound, while no significant peculiar motions have been found: the peculiar velocities do not exceed the measurement errors by more than a factor of 1.5-2. The mean random peculiar velocities of clusters and the systematic deviations from the overall Hubble expansion in the supercluster are consistent with theoretical estimates. For the possible approach of the three UMa subsystems to be confirmed, the measurement accuracy must be increased by a factor of 2-3.Comment: 21 pages, 4 tables, 7 figure

BRSMG Predileta: irrigated rice cultivar for lowlands in Minas Gerais, Brazil.

The cultivar of irrigated rice BRSMG Predileta has high grain yield, resistance to the main rice diseases and produces good quality grains for industry and cooking. It was recommended in 2007 by the Genetic Improvement Program for lowland rice in Minas Gerais, developed by EPAMIG in partnership with Embrapa Arroz e Feijão