Identification of non-stopping ions with Z>65 in polycarbonate track detector stacks

Several corrections have been added to the well-known Bethe–Bloch formula to extend its range of validity to any incident ion penetrating almost any absorber. The possible contribution of close collisions to track formation has been studied, in opposition with the REL model that considers only distant collisions. A method based on the fractional gradient of the recorded signal strength is applied in this work to identify ions with Z>65 recorded in polycarbonate stacks that were exposed as part of the ultra heavy cosmic ray experiment. The results are consistent with a contribution of close collisions to track formation either small or null.     

Sequential injection flow system with improved sample throughput: determination of glycerol and ethanol in wines

The performance of sequential injection (SI) systems has often been criticized for its low sampling frequency. The present work describes a SI system where an injection valve and an additional pump were incorporated to enhance sample throughput rate. The proposed system was applied to the enzymatic determination of glycerol and ethanol in wines, using spectrophotometric detection and immobilized glycerol and alcohol dehydrogenases. The method proposed was applied to the determination of ethanol between 0.10 and 0.50% (v/v) and glycerol between 0.03 and 0.30 g l⁻¹. These ranges were appropriate for determination in table and port wines, since samples were diluted 50 times before introduction into the system. The results obtained from 15 wine samples were statistically comparable to those obtained by the reference methods, with good repeatability (R.S.D.<3.4%, n=10). The sampling rate was 22.5 h⁻¹, corresponding to 45 determinations per hour. This way, the time required for each determination was decreased by 30% when compared to a conventional SI system.     

Intramolecular Diels-Alder reaction of 1-aminoisobenzofurans: Application to the synthesis of benzo[c]phenanthridines

Intramolecular Diels-Alder reactions of 1-aminoisobenzofurans give benzo[c]phenanthridines. The reactive intermediates are generated from o-(diazomethyl)benzamides.     

A modified REL track formation model and its application to registration of 1 GeV/n Au and U ions in polycarbonate

Identification of heavy ions recorded in track detectors requires the knowledge of the physical processes which take place in each of the three steps involved in ion registration: (i) energy deposition by the incident particle in the detector; (ii) track formation; and (iii) the identification method itself. The amount of energy deposited by the incident particle per unit path length (dE/dx) is usually calculated by means of the Bethe–Bloch formula, which is described in terms of the so-called close and distant collisions. The REL track formation model excludes the contribution of close collisions when calculating the fraction of dE/dx leading to track formation. The identification method relates REL to a measurable signal S in the detector, so that S=g(REL)^h where g and h are parameters to be obtained from calibration. In this work, we present a modified REL model in which the energy deposited by close collisions may contribute partially to track formation. This contribution is accounted for by means of a new coefficient κ, introduced in the modified REL expression, which can take values between 0 and 1. We estimate the value of κ from measurements of tracks originated in polycarbonate detectors by incident Au and U ions of energy from accelerator. The results are consistent with a small contribution (κ0.3) of close collisions.     

Reactions with Weakly Bound Nuclei,at near Barrier Energies,and the Breakup and Transfer Influences on the Fusion and Elastic Scattering

We present a brief review of the reaction mechanisms involved in collisions of weakly bound projectiles with tightly bound targets, at near-barrier energies. We discuss systematic behaviors of the data, with emphasis in fusion, breakup, nucleon transfer and elastic scattering. The dependence of the breakup cross section on the charge and mass of the target is discussed, and the influence of the breakup channel on complete fusion is investigated. For this purpose, we compare reduced fusion cross sections with a benchmark universal curve. The behaviors observed in the comparisons are explained in terms of polarization potentials and of nucleon transfer followed by breakup. The influence of the breakup process on elastic scattering is also discussed. Some apparent contradictions between results of different authors are explained and some perspectives of the field are presented.     

Ruthenium complexes of 3-hydroxy-4-pyranones and of 3-hydroxy-4-pyridinones

Reactions of hydrated ruthenium chloride with 2-methyl-3-hydroxy-4-pyranone, ethylmaltol (etmaltH) and with 1,2-dimethyl-3-hydroxy-4-pyridinone (dmppH) are described. The former results in the formation of Ru(etmalt)₃, but the course of the latter depends on conditions, producing the earlier-characterised Ru(dmmp)₃Cl in ethanol–water solution, Ru(dmmp)₃ in aqueous solution under mild conditions, and Ru(dmpp)₂(H₂O)₂ after extended refluxing. EXAFS studies established ruthenium-oxygen distances in Ru(etmalt)₃ and in Ru(dmmp)₃ · 6H₂O. Solubilities of Ru(dmmp)₃ in methanol–water mixtures reveal greater solubility in methanol than in water, and indications of a modest solubility maximum, and thus synergic solvation, in methanol-rich mixtures.     

Polymorphic coordination networks responsive to CO2, moisture, and thermal stimuli: porous cobalt(II) and zinc(II) fluoropyrimidinolates

The novel porous [{M(F-pymo)(2)}(n)]2.5n H(2)O coordination networks (M=Co, Zn; F-pymo=5-fluoropyrimidin-2-olate), possessing sodalitic topology, have been synthesised and structurally characterised by means of powder diffraction methods. Thermodiffractometry demonstrated their plasticity: when heated up to 363 K, they reversibly transform into three-dimensional dehydrated [{M(F-pymo)(2)}(n)] species, with significantly different lattice parameters. Further heating induces irreversible polymorphic transformations into layered phases, in which the original MN(4) coordination sphere changes into an MN(3)O one. A mixed-metal phase, [{Co(x)Zn(1-x)(F-pymo)(2)}(n)]2.5n H(2)O, was also prepared, showing that zinc is preferentially inserted, when starting from a Co/Zn reagent ratio of 1:1. The solid-gas adsorption properties of the anhydrous 3D frameworks have been explored towards N(2), H(2) (77 K) and CH(4), CO(2) (273 K). These results show that these materials permit the diffusion of CO(2) molecules only. Remarkably, the CO(2) adsorption process for the [{Co(F-pymo)(2)}(n)] network proceeds in two steps: the first step takes place at low pressures (<600 kPa) and the second one above a threshold pressure of 600 kPa. By contrast, the [{Zn(F-pymo)(2)}(n)] network only permits CO(2) diffusion by applying pressures above 900 kPa. This type of behaviour is typical of porous networks with gated channels. The high CO(2) selectivity of these systems over the rest of the essayed probe gases is explained in terms of flexibility and polarity of the porous network. Finally, the magnetic studies on the Co(II) systems reveal that the as synthesised [{Co(F-pymo)(2)}(n)]2.5n H(2)O material behaves as an antiferromagnet with a T(N) of about 29 K. At variance, the [{Co(F-pymo)(2)}(n)] layered phase shows an unusually weak ferromagnetic ordering below 17 K, arising from a spin-canting phenomenon.     

Sesquiterpenes from Culcasia scandens P. Beauv

From Culcasia scandens P. Beauv., carota-4(5), 11(12)-diene (isodaucene), carota-3(4), 11(12)-dien-5-one, a new epoxide, 4,5-epoxy-carota-11(12)-ene (isodaucene epoxide) and beta-caryophyllene epoxide were isolated. The structures were established spectroscopically. Epoxidation of isodaucene with m-CPBA confirmed the structure and stereochemistry of the new epoxide.