The objective of this investigation was to study the effect of carbonation on two reinforced concrete structures of 42 and 60 years old, located on two different environments: urban and rural. ...Samples of concrete were taken, the carbonation depth was measured and density, absorption and porosity tests were performed. The carbonation process can be modeled by the equation of the square root of time. From that model, the carbonation constant for each sample was calculated, the progress of the carbonation depth versus time was plotted and the correlation between porosity and depth of carbonation was analyzed. It was verified the existence of different microclimates surrounding structural elements. The moisture content of the surrounding surface of each structural element is the most important factor affecting the progress of carbonation.
We have studied the methods for comparing the values of the critical current measured on superconducting strands with the ones obtained on a complex Rutherford cable made of the same strands. This ...problem is related to the definition of critical magnetic field for strands and cables carrying a given current, which generates a not negligible and inhomogeneous self-field. The method is based on the evaluation of the electrical field along the conductors carrying currents around the critical value. The developed criteria are adopted for comparing the critical currents measured on short samples of strands and Rutherford cables made of 32 strands embedded in pure aluminum matrix.
The cancer therapy (hadrontherapy) with accelerated particle beams is an innovative method that allows an accurate and effective treatment of several kinds of tumors minimizing the irradiation of the ...surrounding tissues and avoiding intercepting vital organs. The deep tumors are usually treated with proton or ion beams by using a rotating gantry that allows the 360/spl deg/ irradiation of the patient. For the carbon ion hadrontherapy, being the energy in the order of 400 MeV, huge gantry structures are required if resistive magnets are used. An alternative solution was studied, involving the use of a cryogenic free superconducting magnet. The magnet consists of ten 90/spl deg/ bent superconducting dipoles wound with an aluminum stabilized Cu/NbTi conductor and mechanically supported by an aluminum alloy structure. In order to validate the feasibility of such a magnet, an accurate study of the winding technique was carried out, together with a winding test of a coil prototype.
The therapy of cancer (hadrontherapy) with accelerated particle beams is an out coming method that allows an accurate and effective treatment of several kinds of tumors minimizing the irradiation of ...the surrounding tissues and avoiding intercepting vital organs. The deep tumors are usually treated with proton or ion beams by using a rotating gantry that allows the 360/spl deg/ irradiation around the patient. For carbon ion hadrontherapy being the energy in the order of 400 MeV, huge gantries structure are required if resistive magnets are used. The size of a ion gantry can be of the order of 10 m in diameter and 100 tons in weight. An alternative solution has been studied, involving the use of a cryogenic free superconducting magnet. The magnet consists of ten 90/spl deg/ bent superconducting dipoles wound with an aluminum stabilized Cu/NbTi conductor and mechanically supported by an aluminum alloy structure. An optimization of the magnetic design is running by using genetic algorithms with the goal to obtain a field homogeneity within 0.2% in a region of 60/spl times/200 mm/sup 2/ along the beam path. Furthermore, an accurate study of the winding technique is in progress. The magnet will be kept at 4.5 K by a cooling system based on two cryocoolers operating alternately in steady state or together during the cool down and the electrical transients. The current is supplied via a couple of HTCS current leads always connected. In the paper, a description of the design is given.
A conceptual design of a mobile isocenter carbon ion gantry was carried out in the framework of the Particle Training Network for European Radiotherapy (PARTNER) and Union of Light Ion Centres in ...Europe (ULICE) projects. To validate the magnets used in this gantry, Finite Element Method (FEM) simulations were performed with COMSOL multiphysics; the purpose was to evaluate the magnetic field quality and the influence of additional support structures for correctors, 90° bending dipole and quadrupoles, both in dynamic and static regimes. Due to the low ramp rates, the dynamic effects do not disturb the homogeneity and the magnetic field level. The differences between the stationary field and the corresponding dynamic field after the end of the ramps are in the order of 10-4; it implies that the magnets can be operated without significant field lag at the nominal ramp rate. However, even in static regime the magnetic length of corrector magnet decreases by 5% when the rotator mechanical structure is considered. The simulations suggest an optimization phase of the correctors in the rotator.
We have analyzed both conformational and functional changes caused by two large cis-acting deletions (delta 159 and delta 549) located within the read-through domain, a 850 nucleotide hairpin, in ...coliphage Q beta genomic RNA. Studies in vivo show that co-translational regulation of the viral coat and replicase genes has been uncoupled in viral genomes carrying deletion delta 159. Translational regulation is restored in deletion delta 549, a naturally evolved pseudorevertant. Structural analysis by computer modeling shows that structural features within the read-through domain of delta 159 RNA are less well determined than they are in the read-through domain of wild-type RNA, whereas predicted structure in the read-through domain of evolved pseudorevertant delta 549 is unusually well determined. Structural analysis by electron microscopy of the genomic RNAs shows that several long range helices at the base of the read-through domain, that suppress translational initiation of the viral replicase gene in the wild-type genome, have been destabilized in delta 159 RNA. In addition, the structure of local hairpins within the read-through region is more variable in delta 159 RNA than in wild-type RNA. Stable RNA secondary structure is restored in the read-through domain of delta 549 RNA. Our analyses suggest that structure throughout the read-through domain affects the regulation of viral replicase expression by altering the likelihood that long-range interactions at the base of the domain will form. We discuss possible kinetic and equilibrium models that can explain this effect, and argue that observed changes in structural plasticity within the read-through domain of the mutant genomes are key in understanding the process. During the course of these studies, we became aware of the importance of the information contained in the energy dot plot produced by the RNA secondary structure prediction program mfold. As a result, we have improved the graphical representation of this information through the use of color annotation in the predicted optimal folding. The method is presented here for the first time.
The resistance of a joint between superconducting cables during and after a transient is a function of time, depending on the inductance per unit length, the steady state resistance and the joint ...configuration. We propose analytical solutions to the problem of current diffusion in joints between superconducting cables in few cases of practical interest for magnet applications. Furthermore general solutions are given, that allow obtaining the time evolution of the joint current and voltage in case of any time depending transport current.
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