[en] If neutrinos have non-vanishing mass and non-vanishing magnetic moments, then electron neutrinos emitted in nuclear reactions in the solar interior may undergo flavour oscillations, spin precession or resonant spin-flavour precession. Assuming equal values for the magnetic moments of all neutrino flavours and using the data from Homestake and SuperKamiokande we obtain an upper limit on the neutrino magnetic moment and find μ_νe ≤ (2.2-2.3) x 10^-10 μ_B, within four standard solar models. We also point out that this limit may be further reduced if the detector threshold energy for the ν_e,xe^- scattering is decreased

[en] We study the gaugino+s-electron, Wν and Ze photoproductions off electrons with both beams polarized. We make a systematic calculation of the spin and angular asymmetries and obtain model independent results, which allow to identify the spin and/or charge of the scalar s-leptons and of the electroweak gauge bosons, either in the high energy limit or at the threshold. For example, the photon helicity asymmetries of the W and Z total cross sections have the distinct value 1 at threshold, but it is negative for the reactions γe → spinor + scalar. In the high energy limit, the same asymmetry for the differential cross sections is equal to one for spin zero boson and negative for W and Z photoproductions and Compton scattering. (orig.)

[en] Currently, many kinds of radioactive sources are used in brachytherapy for cancer treatment. The 125I seed used in this work is the model Onco Seed 6711, produced by Oncura, which is ranked among the best options for treating prostate cancer. This source emits gamma photons with average energy of 28 keV and has a half-life of 59.4 days. After the implants, the natural movement of the organ can cause the seeds undergo slight displacements relative to the position originally planned, which can cause changes in dose distribution in the tumor volume. This work seeks to compare the dose distribution in a solid water phantom of two symmetrical, but different arrangements of four seeds. For this study, the phantom was machined to accommodate the seeds and TLD-100 LiF rod type dosimeters. The study, using TLD dosimeters, was conducted up to 4 cm of the settings. In addition, an Ebt Gafchromic radiochromic film was positioned over the two configurations during a period of time enough for 1 Gy deposition on it, to observe possible changes in the shape of the isodose curves. The TLD results showed a difference up to 35.8% of the dose deposited in the center of the configurations and different doses were deposited at distances corresponding to 1 and 2 cm radius from the symmetrical seeds arrangements. After 3 cm radius, the dose discrepancy is no longer significant. Another important point is that despite the configurations are symmetric, different dose values were deposited at symmetrical points. The isodose qualitative curves shown by the films showed a difference in the shape of that curves. Thus, the different positions of the seeds proved decisive in dose deposition and this fact should be taken into consideration in planning treatment

[en] Computed Tomography (CT) is an essential method for tracking neoplasia and efficiently diagnosing a wide variety of thoracic diseases. CT is generally considered the most accurate choice for lung examination. Due to the growing use of CT, breast and other superficial and radiosensitive organs are unnecessarily irradiated during radiological procedures, thus requiring the development of strategies appropriate to optimize and, if possible, to reduce the radiation dose. The use of bismuth shielding to reduce radiation dose absorbed by breast during thoracic CT examinations has been the subject of many studies recently published by Brazilian and foreign authors of various fields. The purpose of this paper is both to accurately determine the glandular dose when breast is exposed to radiation and to assess the reduction in absorbed dose during thoracic CT examinations, using a set of Thermoluminescent Dosimeters, an anthropomorphic phantom and bismuth shielding. (Author)

[en] Computed tomography (CT) has become the most important and widely used technique for diagnosis purpose. As CT exams impart high doses to patients in comparison to other radiologist techniques, reliable dosimetry is required. Dosimetry in CT is done in terms of air kerma index in air or in a phantom measured by a pencil ionization chamber under a single X-ray tube rotation. In this work, a comparison among CT dosimetric quantities measured by an UNFORS pencil ionization chamber, MTS-N RADOS thermoluminescent dosimeters and GAFCHROMIC XR-CT radiochromic film was done. The three dosimetric systems were properly calibrated in X-ray reference radiations in a calibration laboratory. CT dosimetric quantities were measured in CT Bright Speed GE Medical Systems Inc., scanner in a PMMA trunk phantom and a comparison among the three dosimetric techniques was done. (Author)

[en] The cervical spine is the region of the column that articulates the head and chest. The tests of computed tomography (CT) performed in this region have as main objectives to diagnose fractures, dislocations and tumors. In CT scans the cervical spine volume is limited by the foramen Magnum and the first thoracic vertebra. In this region is the thyroid that is directly irradiated by X-ray beam during cervical scan. Based on this information, it was studied the dose variation deposited in thyroid and in nearby organs, such as: lenses, spinal cord in the foramen Magnum region and breasts, with and without the use of bismuth protector. In this study was used a male anthropomorphic phantom and thermoluminescent s dosimeters (TLD-100) were required to register the individual doses in the organs of interest. CT scans were performed on a GE Bright Speed scanner of 32 channels. With the data obtained, it was found the organ dose variation. The largest recorded dose was in the thyroid. Comparing two scans it was possible to note that the use of the bismuth protector promoted a 26% reduction in the thyroid dose and an increase in the lens dose. (Author)

[en] In this study, doses in the lens, pituitary and thyroid were compared for different stress values ​​of X-ray tube feeding in male and female anthropomorphic mannequins. A General Electric 64-Channel Discovery Model CT Scanner; two anthropomorphic mannequins Alderson Rando Male and Female Head and Neck Radiochromic Filmstrips GAFCHROMIC AQ-R2 were used to record the point doses. Strips were located of radiochromic film in the areas corresponding to the lens, thyroid and pituitary in each of the mannequins being irradiated with beams of 80, 100 and 120 kV supply voltage from the X-rays making explorations of 30 cm in length. Noise index analyzes of the images of the central slice of each mannequin. The dose values ​​recorded by the test strips radiochromic films are among the reference values ​​proposed by legislation Brazilian with significant differences between the two mannequins. The percentages of noise found in the images are within acceptable values ​​for radiodiagnosis on CT.

[en] Digital Breast Tomosynthesis (DBT) is an efficient method to diagnose changes in the breast tissues. However, it may promote some future detriment to the patient exposed in this test. The future effects can be evaluating using absorbed dose values. In this work a breast compressed phantom was developed for use mammography and DBT tests. This phantom is made in PMMA and it is composed of four plates. It has a semicircular shape with dimensions of 18 to 10 cm and a thickness of 5 cm. The phantom was used for observe the dose distribution in the central area of the phantom and the entrance skin air kerma (ESAK) in the superior surface. To record profile doses it was used radiochromic film sheets cut in a semi circular shape. The experiments were made in a device Selenia, Dimensions model, using the automatic exposition control to define the optimized acquisition protocol. The phantom was irradiated with 30 kV and 55,4 m A.s, using tungsten target and aluminium filter. The defined X-ray beam and a mammographic ionizing chamber were used for expose some film strips and obtain two calibration curves, one for the surface and another for the middle, in the range of interest. The film sheets were placed in the phantom alternatively, in two different expositions, using the same protocol. After digital images of the film sheets were made and worked to obtain dose profiles. The average air kerma recorded in the central cut was 1.54 mGy and the average ESAK recorded was 5.48 mGy. The variation of the ESAK in the surface area was lower than 10% and in the middle the air kerma variation was lower than 8%. The use of radiochromic film was good to obtain dose profiles in breast tomosynthesis expositions. (Author)

[en] The authors present optical spectra of the peculiar Type Ia supernova (SN Ia) 1999ac. The data extend from -15 to +42 days with respect to B-band maximum and reveal an event that is unusual in several respects. prior to B-band maximum, the spectra resemble those of SN 1999aa, a slowly declining event, but possess stronger Si II and Ca II signatures (more characteristic of a spectroscopically normal SN). Spectra after B-band maximum appear more normal. The expansion velocities inferred from the Iron lines appear to be lower than average; whereas, the expansion velocity inferred from Calcium H and K are higher than average. The expansion velocities inferred from the Iron lines appear to be lower than average; whereas, the expansion velocity inferred from Calcium H and K are higher than average. The expansion velocities inferred from Si II are among the slowest ever observed, though SN 1999ac is not particularly dim. The analysis of the parameters v₁₀(Si II), R(Si II), v, and Δm₁₅ further underlines the unique characteristics of SN 1999ac. They find convincing evidence of C II λ6580 in the day -15 spectrum with ejection velocity v > 16,000 km s^-1, but this signature disappears by day -9. This rapid evolution at early times highlights the importance of extremely early-time spectroscopy

[en] We present an extensive new time series of spectroscopic data of the peculiar SN 1999aa in NGC 2595. Our data set includes 25 optical spectra between -11 and +58 days with respect to B-band maximum light, providing an unusually complete time history. The early spectra resemble those of an SN 1991T-like object but with a relatively strong CaH and K absorption feature. The first clear sign of Si II lambda 6355, characteristic of Type Ia supernovae, is found at day -7, and its velocity remains constant up to at least the first month after B-band maximum light. The transition to normal-looking spectra is found to occur earlier than in SN 1991T, suggesting SN 1999aa as a possible link between SN 1991T-like and Branch-normal supernovae. Comparing the observations with synthetic spectra, doubly ionized Fe, Si, and Ni are identified at early epochs. These are characteristic of SN 1991 T-like objects. Furthermore, in the day -11 spectrum, evidence is found for an absorption feature that could be identified as high velocity C II lambda 6580 or H alpha. At the same epoch C III lambda 4648.8 at photospheric velocity is probably responsible for the absorption feature at 4500 8. High-velocity Ca is found around maximum light together with Si II and Fe II confined in a narrow velocity window. Implied constraints on supernovae progenitor systems and explosion hydrodynamic models are briefly discussed