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.     

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.     

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.     

First total synthesis of (-)-achilleol B: reassignment of its relative stereochemistry

The first total synthesis of (-)-achilleol B was achieved using a convergent approach with a longest linear sequence of 14 steps. Three key steps were employed, including an enantioselective Robinson annelation for the construction of the bicyclic moiety. The monocyclic synthon was prepared through a Ti(III)-mediated cylization of a chiral monoepoxide obtained via asymmetric dihydroxylation of geranylacetone. The asymmetric preparation of these subunits also permitted us to achieve the enantioselective synthesis of elegansidiol, achilleol A, and farnesiferol B.     

Development and validation of a capillary electrophoresis method for the characterization of sulfoethyl cellulose

To characterize sulfoethyl cellulose el samples, a capillary electrophoresis method was developed and validated sulfoethyl cellulose el was hydrolyzed, and the resulting d ‐glucose derivatives were analyzed after reductive amination with 4‐aminobenzoic acid using 150 mM boric acid, pH 9.5, as background electrolyte at 20°C and a voltage of 28 kV. Peak identification was derived from capillary electrophoresis with mass spectrometry using 25 mM ammonia adjusted to pH 6.2 by acetic acid as electrolyte. Besides mono‐, di‐, and trisulfoethyl d ‐glucose small amounts of disaccharides could be identified resulting from incomplete hydrolysis. The linearity of the borate buffer‐based capillary electrophoresis method was evaluated using d ‐glucose in the concentration range of 3.9–97.5 μg/mL, while limits of detection and quantification derived from the signal‐to‐noise ratio of 3 and 10 were 0.4 ± 0.1 and 1.2 ± 0.3 μg/mL, respectively. Reproducibility and intermediate precision were determined using a hydrolyzed sulfoethyl cellulose el sample and ranged between 0.2 and 8.8% for migration times and between 0.3 and 10.4% for peak area. The method was applied to the analysis of the degree of substitution of synthetic sulfoethyl cellulose el samples obtained by variation of the synthetic process and compared to data obtained by elemental analysis.