AISHa mechanical study and commissioning

ABSTRACT

The ion sources for accelerators devoted to medical applications must provide intense ion beams, with high reproducibility, stability and brightness. AISHa (Advanced Ion Source for Hadron therapy) is a compact ECRIS whose hybrid magnetic system consists of a permanent Halbach-type hexapole magnet and a set of independently energized superconducting coils. These coils will be enclosed in a compact cryostat with two cryocoolers for LHe-free operation. The AISHa ion source has been designed by taking into account the typical requirements of hospital-based facilities, where the minimization of the mean time between failures (MTBF) is a key point together with the maintenance operations which should be fast and easy. It is a multipurpose device, operating at 18?GHz, in order to achieve higher plasma densities able to provide enough versatility for future needs of the hadron therapy, including the ability to run at larger microwave power to produce different species and highly charged ion beams. In this paper, the innovative solutions, used for the plasma containment chamber and for the permanent magnet hexapole holder, are presented to solve the insulation and structural issues. The choice of the different materials used is hereinafter discussed together with all the involved processes (spinning, curing and machining). The glass fibers and carbon fibers are used to reinforce polymer matrices and give rise to structural composites and composites by molding. The paper shows also some results of ion source commissioning along with next developments. Innovative active coupling techniques are planned to be tested to optimize the first pass wave absorption, which plays an important role in the coupling optimization of the new-generation ECRIS.     

Lyotropic mesomorphism of alkyl esters of acyl-L-carnitines

The lyotropic polymorphism of a series of alkyl esters of acyl-L-carnitine has been studied by optical polarizing microscopy and X-ray diffraction. The different structures observed as a function of concentration and temperature have been characterized and their topology determined. As a result, two different phase sequence patterns have been detected: esters of normal alcohols bearing an alkyl chain of 6 or more carbon atoms in the acyl substituent display only a lamellar phase, while compounds which bear a relatively short alkyl chain (4 or less carbon atoms) show in addition non-lamellar type I hexagonal and cubic Q²³⁰ phases. From the analysis of the areas-per-molecule at the polar/apolar interface, the ability of the compounds investigated to form not only non-lamellar phases, but also direct micelles in isotropic solution has been related to the structural characteristics of the molecules. Curved, convex interfaces (in micelles and in non-lamellar phases) are possible only for the most polar acylcarnitines which have a relatively short alkyl chain, so that they behave like single chain surfactants; the most paraffinic derivatives, which have a relatively long alkyl chain, are effective double chain surfactants and then generate only quasi-planar interfaces.     

On the solution set of an equation of the type f(t, Φ(u(t)) = 0

We investigate the solution set Γ of an equation of the type f(t, Φ(u(t)) = 0, where Φ is a linear homeomorphism from a topological vector space X onto L ¹(T) and f: T×R → R is a Carathéodory function. More precisely, we characterize the property of Γ of intersecting each closed hyperplane of X.     

Indole alkaloids from the roots of an african plant securidaca longipedunculata. I. Isolation by column chromatography and preliminary structural characterization by mass spectrometry

The extraction and the isolation of some alkaloids from the roots of an African plant (Securidaca Longipedunculata Fres) are reported. The structural characterization was performed by mass spectrometry. Alternative ionization methods (FAB and EI), collisionally-induced decomposition experiments and accurate mass measurements revealed the presence of elymoclavine and dehydroelymoclavine and the presence of a new ergoline alkaloid.     

Sodium Chloride Molar Conductance in Different Poly(ethylene glycol)–Water Mixed Solvents

The molar conductivities of NaCl in several poly(ethylene glycol)(PEG)–water “mixed solvents” are presented as a function of the PEG content in solution. Three different PEG samples, a monodispersed one and two polydispersed ones, have been used. The comparison between the molar conductivity values in the mixed solvents and the corresponding ones in pure water shows that the only effect of PEG on the ions’ motions is an obstruction effect despite the variation of the macroscopic dielectric constant induced by PEG itself. A comparison between the molar conductivities and the corresponding mutual main diffusion coefficients shows a tight correlation between the two quantities. This correlation is possible only in the absence of electrostatic effects due to the presence of PEG.     

The Oxidative Mechanism in Electrophilic C?H Activation: The Case of CH2F2 and CH2Cl2

The H^.‐atom transfer (HAT) reaction is investigated in the gas phase, starting from two different entrance channels, O₂^.+/CH₂X₂ and CH₂X₂^.+/O₂ (X=F, Cl), that correspond to a step of hydride transfer and to HAT, respectively. Analysis of the spin and charge along the reaction pathway shows that HAT occurs through the same reacting configuration, irrespective of whether the reactants are formed within the complex or are free isolated species.     

Asymmetric radiation-induced inclusion polymerization of 3-methyl-1,4-pentadiene in deoxycholic acid

The radiation-induced polymerization of 3-methyl-1,3-pentadiene (3MPD) as an inclusion complex in deoxycholic acid (DOCA) has produced in good yield the optically active polymer poly(3-methyl-1,4-pentadiene) (P3MPD) whose structure and properties were studied by FT-IR spectroscopy and thermal analysis (TGA, DTG and DTA). The data show that the polymer is essentially trans-1,4-P3MPD as expected for the polymerization in constrained media. Trans-1,4-P3MPD is optically active with [α]_D values comprised between +4.3 and +5.6. The optical rotatory dispersion curve of the P3MPD is completely different from that of DOCA as expected.     

Application of LC–NMR to the identification of bulk drug impurities in NK1 antagonist GW597599 (vestipitant)

Liquid chromatography‐NMR (LC–NMR) spectroscopy was used to obtain detailed information regarding the structure of the major bulk drug impurities present in GW597599 (vestipitant). The one‐dimensional ¹H LC–NMR experiments were performed in both continuous and stop‐flow modes on a sample of GW597599 (vestipitant) enriched with mother liquor impurities. The information derived from both LC–NMR and LC–MS data provided the structural information of all major impurities. The full characterisation of the impurities by high‐resolution NMR spectroscopy was ultimately performed on appropriately synthesised compounds. Copyright © 2010 John Wiley & Sons, Ltd.