[en] The study of geomagnetic storms is a topic of great practical interest due to its effects on everyday's life. Originating from the sun, these storms result from high energy ions that couple to the earth's magnetosphere and are sometimes responsible for damaging satellites, interrupting radio communications and even causing power surges on some extreme occasions. Coronal mass ejections (CME's) are large scale solar events consisting of massive quantities of over-dense hot plasma (∼10''16 g of plasma in the temperature range of ∼ 4MK) that is ejected from the sun's streamer belt in a region known as the coronal. CME's can travel at speeds up to 1000 km/s interacting with the slower solar wind and causing the large scale formation of highly energetic ions due to wave particle interactions in the shock front. The actual acceleration mechanisms of the energetic ions are still under strong debate. In this paper the acceleration processes of solar energetic particle events due to CMEs are investigated. A 3D hybrid particle code called dHybrid simulate the corona environment. In dHybrid, the ions are assumed kinetic and the electrons are treated as a neutralizing massless fluid. A arbitrary number of particle species can be initialized in the simulation box, along with an arbitrary external magnetic field allowing a suitable configuration for this kind of studies. The code can also solve the MHD set of equations allowing for comparison between the models. Initial conditions are set in accordance with MHD models of the corona widely described in the literature. The simulation reveals the presence of shock like structures, being the source of SEPs. Analysis of the acceleration of ions in the shocks is examined. A detailed comparison between MHD results and hybrid simulation results is also presented. (Author)

[en] Polyethylene foams, produced by radio-induced crosslinking, show a smooth and homogeneous surface, when compared to chemical crosslinking method using peroxide as crosslinking agent. This process fosters excellent adhesive and printability properties. Besides that, closed cells, intrinsic to these foams, imparts optimum mechanical, shocks and insulation resistance, indicating these foams to some markets segments as: automotive and transport; buoyancy, flotation and marine; building and insulation; packaging; domestic sports and leisure goods. We were in search of an ideal foam, by adding 5 to 15% of blowing agent in LDPE. A series of preliminary trials defined 203 degree sign C as the right blowing agent decomposition temperature. At a 22.7 kGys/dose ratio, the lowest dose for providing an efficient foam was 30 kGy, for a formulation comprising 10% of azodicarbonamide in LDPE, within a 10 minutes foaming time

[en] Laser induced stress waves are being used in a variety of medical applications, including drug delivery and targeted tissue disruption. Stress waves can also be an undesirable side effect in laser procedures such as ophthalmology and angioplasty. Thus, a study of the effects of stress waves on a cellular level is useful. Thermoelastic stress waves were produced using a Q-switched frequency-doubled Nd:YAG laser (λ=532nm) with a pulse duration of 4 ns. The laser radiation was delivered to an absorbing media. A thermoelastic stress wave was produced in the absorbing media and propagated into plated cells. The energy per pulse delivered to a sample and the spot size were varied. Stress waves were quantified. We assayed for cell viability and damage using two methods. The laser parameters within which cells maintain viability were investigated and thresholds for cell damage were defined. A comparison of cell damage thresholds for different cell lines was made

[en] The interaction of an electromagnetic wave packet with a superluminous ionization front is described here using the Hamiltonian theory of photon acceleration. The authors also describe the interaction with accelerated ionization fronts. The different qualitative photon trajectories are presented for both cases. The frequency up-shift is also derived. It is shown that a proper tailoring of the ionization front velocity can lead to higher frequency up-shifts than in constant velocity ionization fronts

[en] We present a full wave description of the frequency up-shift of the electromagnetic radiation inside a cavity, in the presence of a space and time dependent refractive index. An intense laser beam propagating along a gas creates an ionization front, moving with the group velocity of the laser beam, described by the plasma frequency ω_p = ω_p (rvec r - rvec v_ft) where rvec v_f is the velocity of the front. Assuming that the electric field inside the cavity can be written as a linear superposition of the spatial eigenmodes of the cavity, we derive the linear mode coupling equations governing photon acceleration by ionization fronts. With this model, we calculate analytically and numerically the full spectrum content of the radiation inside the cavity. It is shown that the spectrum of the electromagnetic wave is much broader than it is usually assumed by other theories. The results are compared with the predictions of the hamiltonian theory of photon acceleration. We generalize this formulation to take into account the frequency up-shift due to collective plasma oscillations or an electron beam. It is shown that the amplitude of the electric field is considerably higher in these situations

[en] This report summarizes the major accomplishments of this three-year Laboratory Directed Research and Development (LDRD) Lab Wide (LW) project entitled, ''An Inner-Shell Photo-Ionized X-Ray Laser at 45 (angstrom)'', tracking code 99-LW-042. The most significant accomplishments of this project include the design of a suitable x-ray laser target, the invention of a measurement technique for the determination of rise times of x-ray pulses on the order of 50 femtoseconds, and a novel setup for generating a traveling wave with an ultrashort optical laser pulse. The pump probe technique for rise time measurement will allow us to detect ultrashort x-ray pulses, whose generation by means of a variety of 4th generation light sources is currently under planning elsewhere

[en] The spatial and spectral features of photon acceleration are considered in the framework of a kinetic theory based on a generalization of the photon number concept and the Klimontovich equation for the photons. We describe the spectral chirp induced by the wake field in the photon accelerator scheme. The explicit expression for the induced chirp and the conditions for maximum chirp are derived. (author)

[en] Atmospheric radioactivity monitoring of natural and anthropogenic radionuclides is important, not only for radiological protection purposes but also in studying global atmospheric transport and deposition processes. Atmospheric radioactivity resulting from anthropogenic activities has dropped to very low levels. However, natural occurring radionuclides such as 7 Be and 210 Pb are always detected in air monitoring programmes based on the collection and measurement of aerosol particles, providing important long - term data that could be used to study air masses transport pathways and aerosol particles behaviour in the atmosphere. ⁷Be (with a half-life of 53.3 days) is mainly produced in the stratosphere by spallation reactions through the interaction of cosmic rays with light atmospheric nuclei, such as nitrogen and oxygen. ²¹⁰Pb (with a half-life of 22.3 years) is produced by the decay of ²²²Rn, which diffuses from soils into the continental boundary layer. Since ²²²Rn flux from the oceans is negligible, ²¹⁰Pb could be used as a natural tracer of continental emissions. Following their production in the atmosphere, both nuclides rapidly attaches to existing aerosol particles. As ⁷Be and ²¹⁰Pb are of different origin their relative activity on aerosol particles should depend on the altitude from which the particles were transported, on the strength of continental influences and on removal processes. In this paper weekly measurements of 7 Be and ²¹⁰Pb activities in aerosol particles are reported for a period of approximately 4 years. Aerosol sampling was carried out using a high volume A.S.S.-500 station with an average air flow of about 800 m³ h^-1. The activity of all the samples was measured by g spectrometry, using a well type HPGe detector. ⁷Be/²¹⁰Pb activity ratios were also calculated, attempting to understand the origin and atmospheric pathways of the air masses that influence the local atmospheric radioactivity levels. The activity concentrations of ⁷Be in ground level air were found to be in the range of 1.2 to 12.2 mBq m^-3, with an average of 3.8 mBq m^-3. The concentrations of ²¹⁰Pb were in the range of 0.1 to 4.7 mBq m^-3, with an average value of 0.6 mBq m^-3, while the ⁷Be/²¹⁰Pb activity ratios were found to be in the range of 1.3 to 32.9. (authors)

[en] Sediment samples from Tejo River were analyzed for "2"2"8Ra, "2"2"6Ra, "1"3"7Cs and "4"0K by HPGe gamma spectrometry. The activity concentration data were statistically analyzed. The activity concentrations values were in the range of about two orders of magnitude for each radionuclide. The influence of the particle size on the radionuclide concentrations was observed. The different environmental origins of the radionuclides "2"2"8Ra, "2"2"6Ra, "1"3"7Cs and "4"0K, in the sediments were demonstrated through correlation analysis. Cluster analysis showed a close relationship between "2"2"8Ra and "2"2"6Ra and a different behavior for "4"0K. The data obtained in this study provides useful information on the background radioactivity of the studied area and can be further used for radiological mapping of the Tejo River. - Highlights: • Sediment samples were analyzed for "2"2"8Ra, "2"2"6Ra, "4"0K and "1"3"7Cs by gamma spectrometry. • Radionuclide activity concentrations are dependent on the sediment particle size. • Correlation analysis demonstrates the different origins of the radionuclides. • Cluster analysis has distinguished two different groups: "2"2"8Ra, "2"2"6Ra and "4"0K

[en] Highlights: • The gasification of manure was evaluated using the software Aspen Plus®. • Composition and LHV of the obtained syngas depends on the operating conditions. • CO_2 net emissions for the steam and CO_2 gasification processes were calculated. • Manure steam gasification can be used as feedstock for Fischer-Tropsch. • Manure CO_2 gasification lead to a syngas suitable for energy production. - Abstract: The gasification of an animal waste biomass (manure) in a dual gasifier was studied using the software Aspen Plus®. For this purpose, a model based on a Gibbs free energy reactor was considered. Effects of the gasification temperature, the gasifying/biomass ratio and the use of steam and CO_2 as the gasifying agents on the composition and the low heating value (LHV) of the produced syngas were evaluated. In this sense, the H_2/CO ratio and the LHV were the parameters calculated to stablish the best operating conditions for the production of either hydrocarbons via Fischer-Tropsch or energy. Furthermore, the CO_2 net emissions generated by the gasification process were also important in the selection of the best operating conditions from an environmental point of view. The obtained results showed that for both gasifying agents the H_2 and CO production was favoured at high temperatures whereas the production of CH_4 and CO_2 was favoured at low ones. On the other hand, the H_2 production was higher when steam was used as the gasifying agent and the formation of CO was enhanced when CO_2 was considered as gasification agent. An increase of the gasifying agent/biomass ratio had a negatively influence on the production of CH_4, leading to a decrease of the LHV. Therefore, steam as the gasifying agent and high temperatures favoured the obtaining of a syngas suitable for the Fischer-Tropsch process whereas CO_2 and low gasification temperatures enhanced a syngas with a high LHV which could be used for energy production. Finally, the net CO_2 emissions were estimated to be lower when CO_2 was again used as the gasifying agent.