En este trabajo se presentan los resultados del análisis de aerosoles atmosféricos obtenidos en un sitio de 13 ciudades de Buenos Aires, durante los meses de abril y mayo de 1997. La concentración de Pb en la atmósfera ha disminuido respecto a las mediciones realizadas en 1988.

The yrast level structure of Rn-215 has been studied by means of in-beam spectroscopy alpha-gamma-gamma coincidence techniques through the Pb-207(O-18,2 alpha 2n) reaction at 93 MeV bombarding energy, using the 8 pi GASP-ISIS spectrometer at Legnaro. New spectroscopic information has been obtained. The deduced low-lying level scheme of Rn-215 does not exhibit the alternating parity structure observed in the heavier known isotones Fr-216, Ra-217, Ac-218, and Th-219. From this result, the lightest nucleus showing evidence for octupole collectivity is Fr-216, defining the lowest-mass corner for this kind of phenomenon as N >= 129 and Z >= 87.

The yrast level structure of ${}^{215}$Rn has been studied by means of in-beam spectroscopy $\ensuremath{\alpha}$-$\ensuremath{\gamma}$-$\ensuremath{\gamma}$ coincidence techniques through the ${}^{207}$Pb(${}^{18}$O,2$\ensuremath{\alpha}2n$) reaction at 93 MeV bombarding energy, using the 8$\ensuremath{\pi}$ GASP-ISIS spectrometer at Legnaro. New spectroscopic information has been obtained. The deduced low-lying level scheme of ${}^{215}$Rn does not exhibit the alternating parity structure observed in the heavier known isotones ${}^{216}$Fr, ${}^{217}$Ra, ${}^{218}$Ac, and ${}^{219}$Th. From this result, the lightest nucleus showing evidence for octupole collectivity is ${}^{216}$Fr, defining the lowest-mass corner for this kind of phenomenon as $N\ensuremath{\ge}129$ and $Z\ensuremath{\ge}87$.

The aim of this study was to evaluate the DNA damage induced by low and high linear energy transfer radiation in two related cell lines with different radiation sensitivity, CHO10B2 and irs-20 cells (defective in DNA-PKcs). Double-strand breaks were assessed by the detection of phosphorylated histone H2AX foci (γH2AX). The number of foci increased as a function of dose for both cell lines and types of radiation. However, irs-20 cells showed a higher number of foci than the parental CHO10B2. An increase in the foci size was observed for both cell lines after lithium irradiation. This could be attributed to clusters of DNA damage. Moreover, the number of lithium-induced larger foci per nuclei increased with dose and fitted with the expected number of hits per nucleus. Concluding, γH2AX foci size provides a potential tool to characterise the intrinsic radiosensitivity of cells related to DNA damage and to compare the effects of different quality radiations.

The use of proton and heavy ion beams for radiotherapy is a well established cancer treatment modality in the first world, which is becoming increasingly widespread, due to its clear advantages over conventional photon-based treatments. This strategy is suitable when the tumor is spatially well localized. Also the use of neutrons has tradition. Here Boron Neutron Capture Therapy (BNCT) stands out, though on a much smaller scale, being a promising alternative for tumors which are diffuse and infiltrating. On this sector, so far only nuclear reactors have been used as neutron sources. In this paper we briefly describe the situation in Latin America and in particular we discuss the present status of an ongoing project to develop a folded Tandem-ElectroStatic-Quadrupole (TESQ) accelerator for Accelerator-Based (AB)-Boron Neutron Capture Therapy (BNCT) at the Atomic Energy Commission of Argentina. The project goal is a machine capable of delivering 30 mA of 2.4 MeV protons to be used in conjunction with a neutron production target based on the (7)Li(p,n)(7)Be reaction. These are the specifications needed to produce sufficiently intense and clean epithermal neutron beams to perform BNCT for deep-seated tumors in less than an hour. The machine being currently designed and constructed is a folded TESQ with a terminal at 0.6MV as a smaller scale prototype. Since the concept is modular the same structure will be used for the 1.2MV final accelerator.

Total suspended particulate (TSP) samples have been collected at six stations in the C and B lines of the Buenos Aires underground system and, almost simultaneously, at six ground level sites outside and nearby the corresponding underground stations, in the Oct 2005/Oct 2006 period. All these samples were analyzed for mass and elemental Fe, Cu, and Zn concentrations by using the Particle Induced X-ray Emission (PIXE) technique. Mostly, TSP concentrations were found to be between 152 mu g m(-3) (25% percentile) and 270 mu g m(-3) (75% percentile) in the platform of the stations, while those in outside ambient air oscillated from 55 mu g m(-3) (25% percentile) to 137 mu g m(-3) (75% percentile). Moreover, experimental results indicate that TSP levels are comparable to those measured for other underground systems worldwide. Statistical results demonstrate that subway TSP levels are about 3 times larger on average than those for urban ambient air. The TSP levels inside stations and outdoors are poorly correlated, indicating that TSP levels in the metro system are mainly influenced by internal sources.Regarding metal concentrations, the most enriched element in TSP samples was Fe, the levels of which ranged from 36 (25% percentile) to 86 mu g m(-3) (75% percentile) in Line C stations, while in Line B ones they varied between 8 mu g m(-3) (25% percentile) and 46 mu g m(-3) (75% percentile). As a comparison, Fe concentrations in ambient air oscillated between 0.7 mu g m-3 (25% percentile) and 1.2 mu g m(-3) (75% percentile). Other enriched elements include Cu and Zn. With regard to their sources, Fe and Cu have been related to processes taking place inside the subway system, while Zn has been associated with outdoor vehicular traffic. Additionally, concerns about possible health implications based on comparisons to various indoor air quality limits and available toxicological information are discussed. (C) 2009 Elsevier Ltd. All rights reserved.

In this work 3D micromachining of x-cut lithium niobate crystals was performed using the high energy heavy ion microbeam (HIM) at the Tandar Laboratory, Buenos Aires. The samples were machined using 35Cl beams at 70MeV bombarding energy combined with wet etching with hydrofluoric acid solutions at room temperature. As the ion beam penetrates the sample, it induces lattice damage increasing dramatically the local etching rate of the material. This technique was applied to the fabrication of 3D waveguides with long control electrodes. The resulting structures indicate that well defined contours with nearly vertical sidewalls can be made. The results also show that with fluences of only 5×1012ions/cm2, this technique is suitable for the fabrication of different shapes of LiNbO3 control-waveguides that can be used in different optical devices and matched with the existing optical fibers.

This study analyzes total suspended particle (TSP) samples collected at two sites of Buenos Aires City (34S, 58W). One site (San Martin) placed 17 kin from city center, and the other one at an underground subway station (Diagonal Norte) in downtown Buenos Aires. In both cases, gravimetric analysis has been performed, while elemental analysis using PIXE has been only carried out in the first case. To the best our knowledge, this is the first airborne particle measurement perform at a Buenos Aires underground subway station.

The yrast level structure of 215,216Rn has been studied using in beam spectroscopy α − γ − γ coincidence techniques mainly through the 207Pb(18O, 2α2n) and 208Pb(18O, 2α2n) reactions in the 91–93 MeV energy range, using the 8π GASP‐ISIS spectrometer at Legnaro. The obtained low lying level scheme of 215Rn does not exhibit the alternating parity structure observed in their heavier known isotones 216Fr, 217Ra and 218Ac. The level scheme of 216Rn resulting from this study shows >From this result, the lightest nucleus showing evidence for reflection asymmetry is 216Fr defining one lowest‐mass corner for this kind of phenomenon as N⩾129 and Z⩾87.

Different analytical techniques are typically used to perform multi-elemental and densitometric analysis by means of particle beams with micrometric space resolution. Usually, those analyses are respectively performed by PIXE and STIM. Traditionally, to characterize the trace element concentrations in a specimen two different experiments are required with differences in setups and types of detectors employed, as well as in the necessary ion current intensifies. In this work, we discuss the latest results in the development of a new technique that synthesizes both analyses in just a single one, by means of heavy ion induced x-ray emission. This technique, implemented for the first time at the Tandar Laboratory, employs a second target in addition to the sample under study. The multi-elemental information of the specimen is provided by its PIXE signal and its densitometric information is supplied by the PIXE signal of the secondary target, which is placed immediately behind the sample under analysis. These PIXE signals are produced and acquired during the same experiment, allowing the analysis of both features (composition and density) at the same time. The X-rays originated in the secondary target are attenuated when traversing the specimen in the direction of the detector and consequently a radiographic image of the specimen is obtained. In this case, the characteristic X-rays of the secondary target act like a monochromatic secondary source. In the present work a method to estimate the thickness of specimens is introduced and compared with estimations performed by the STIM method.

High-spin states in Tm-168 were investigated by means of gamma-ray spectroscopy techniques using the GASP multidetector array. Rotational bands have been established and identified in terms of their configurations.

The yrast level structure of Rn-215,Rn-216 has been studied using in beam spectroscopy alpha - gamma - gamma coincidence techniques mainly through the Pb-207(O-18, 2 alpha 2n) and Pb-208(O-18, 2 alpha 2n) reactions in the 91-93 MeV energy range, using the 8 pi GASP-ISIS spectrometer at Legnaro. The obtained low lying level scheme of Rn-215 does not exhibit the alternating parity structure observed in their heavier known isotones Fr-216, Ra-217 and Ac-218. The level scheme of Rn-216 resulting from this study shows >From this result, the lightest nucleus showing evidence for reflection asymmetry is Fr-216 defining one lowest-mass corner for this kind of phenomenon as N >= 129 and Z >= 87.

The yrast level structure of Rn-216 has been studied using in-beam spectroscopy alpha-gamma-gamma coincidence techniques through the Pb-208(O-18, 2 alpha 2n) reaction in the 91-93 MeV energy range, using the 8 pi GASP-ISIS spectrometer at Legnaro. The level scheme of Rn-216 resulting from this study shows alternating parity bands only above a certain excitation energy. From this result, the lightest nucleus showing evidence of octupole collectivity at low spins is still Fr-216, thereby defining the lowest-mass corner for this kind of phenomenon as N >= 129 and Z >= 87.

Angular distributions and angular correlations have been measured for the emission of one and two alpha-particles in the O-18+Pb-207,Pb-208,Bi-209 reactions at several beam energies above the Coulomb barrier. The results rule out fusion evaporation as the main reaction mechanism for the channels involving alpha-particle emission and support the interpretation of the breakup of the O-18 projectiles into at least C-14+alpha and Be-10+Be-8 before fusion.

Background and purpose: Several techniques with different sensitivity to single-strand breaks and/or double strand breaks were applied to detect DNA breaks generated by high LET particles. Tests that assess DNA damage in single cells might be the appropriate tool to estimate damage induced by particles, facilitating the assessment of heterogeneity of damage in a cell population. The microgel electrophoresis (comet) assay is a sensitive method for measuring DNA damage in single cells. The objective of this work was to evaluate the proficiency of comet assay to assess the effect of high LET radiation on peripheral blood lymphocytes, compared to protons and Co-60 gamma rays. Materials and methods: Irradiations of blood samples were performed at TANDAR laboratory (Argentina). Thin samples of human peripheral blood were irradiated with different doses (0 – 2.5 Gy) of 20.2 MeV helium-4 particles in the track segment mode, at nearly constant LET. Data obtained were compared with the effect induced by 4 MeV protons and Co-60 gamma rays. Alkaline comet assay was applied. Comets were quantified by the Olive tail moment. Results: Distribution of the helium-4 particles and protons were evaluated considering Poisson distribution in lymphocyte nuclei. The mean dose per nucleus per particle result 0.053 Gy for protons and 0.178 Gy for helium4 particles. When cells are exposed to a dose of 0.1 Gy, the hit probability model predicts that 43 % of the nuclei should have experienced an alpha traversal while with protons, 85% of the nuclei should be hit. The experimental results show a biphasic response for helium-4 particles (0.1 Gy), indicating the existence of two subpoulations: unhit and hit. Distributions of tail moment as a function of fluence and experimental dose for comets induced by helium-4 particles, protons and Co-60 gamma rays were analyzed. With helium-4 irradiations, lymphocyte nuclei show an Olive tail moment distribution flattened to higher tail moments as dose increase. However, for irradiations with protons and gamma rays, at increasing doses the tail moments are shifted towards high values with the same distribution, characterized by its asymmetry. Conclusions: The comet assay allowed to observe differences in the patterns of DNA damage induced by helium-4 particles compared to protons and gamma rays, indicating that the mean dose and the hit distribution in the lymphocyte population influence the damage induction.

Microdistributions of the prospective BNCT-compound CuTCPH, a carborane-containing tetraphenylporphyrin with one Cu atom in its molecular structure, have been obtained in tissue sections of different organs of tumor-bearing and normal Syrian hamsters injected with the boron compound by employing a heavy ion microbeam. High resolution X-ray spectroscopy following micro-PIXE (Particle Induced X-ray Emission with micrometer-sized beams) with a focused 16O ion beam was used. Focusing was performed with a heavy-ion scanning high-precision magnetic quadrupole triplet microprobe. Squamous Cell Carcinomas were induced on the right Cheek Pouch of Syrian Hamsters (HCP), sampled, cryo-sectioned and freeze-dried. Two-dimensional maps of elemental concentration were obtained by scanning the beam over the samples. Very non-uniform Cu concentrations were found in all sections.