Nuclear stopping from 0.09A to 1.93A GeV and its correlation to flow

We present a complete systematics (excitation functions and system-size dependences) of global stopping and side flow for heavy ion reactions in the energy range between 0.09A and 1.93A GeV. For the heaviest system, Au+Au, we observe a plateau of maximal stopping extending from about 0.2A to 0.8A GeV with a fast drop on both sides. The degree of stopping, which is shown to remain significantly below the expectations of a full stopping scenario, is found to be highly correlated to the amount of side flow.     

Electron-electron interaction in strong electromagnetic fields: the two-electron contribution to the ground-state energy in He-like uranium

Radiative recombination transitions into the ground state of cooled bare and hydrogenlike uranium ions were measured at the storage ring ESR. By comparing the corresponding x-ray centroid energies, this technique allows for a direct measurement of the electron-electron contribution to the ionization potential in the heaviest He-like ions. For the two-electron contribution to the ionization potential of He-like uranium we obtain a value of 2248+/-9 eV. This represents the most accurate determination of two-electron effects in the domain of high-Z He-like ions, and the accuracy reaches already the size of the specific two-electron radiative QED corrections.     

Possibilities of Production of New Reference Material – Preparation of Gaseous Standard Mixtures Using Thermal Decomposition of Immobilized Compounds – the Effect of Selected Parameters on the Amount of Released Analyte

The paper presents the results of research on a novel type of matrix-free reference materials for volatile organic compounds based upon thermal decomposition of appropriate immobilized compounds. The effect of parameters such as the kind of support (silica gel, porous glass, glass fiber) and the method of chemical modification of the support surface on the amount of chloromethane released as the analyte has been investigated. It was demonstrated that the amount of chloromethane released during thermal decomposition of immobilized compounds formed on the surface of silica gel and porous glass was larger when trimethylamine rather than N-morpholine was used for the preparation of immobilized compound. Reproducibility of the chemical modification procedure using silica gel and the stability of support with the immobilized compound were also examined. The full uncertainty budget of determination of liberated amount of chloromethane has been calculated.     

Chiral polymers containing a carbohydrate moiety: synthesis

This paper reports the preparation of poly(acetal-ethers) by two alternative synthetic pathways (alkaline and acid-catalyzed conditions). Polycondensations of methyl 2,3:4,6-di-O-salicylidene-alpha-D-mannopyranoside (3) (mixtures of endo-H and exo-H dioxolan-2-yl-diastereomers) with 1,4-dibromobutane (4) (method I a and I b) were performed in solvents (DMF, butyl acetate/DMF, DMSO) and were catalyzed by K2CO3/KI or KOH. A similar polymer (6) was formed by the reaction of methyl alpha-D-mannopyranoside (1) and 1,4-bis(2-formylphenoxy)butane (7), catalyzed by p-toluenesulfonic acid (method II). Regardless of conversion or initial comonomer feed ratios, the composition of the polycondensates depended on the reaction conditions, leading to the formation of macrocyclic [1 + 1] (5) and [2 + 2] compounds, which were macromolecules with diverse molecular weights and optical properties. The regioselective polycondensation was examined by 1H NMR spectroscopy of selected polymers. In the case of 5-membered cyclic acetal units, mixtures of the endo-H and exo-H dioxolan-2-yl system, diastereomers were formed in the polymer chain. The macrocycles and linear oligomers were identified by NMR and electrospray mass spectrometry (ESI-MS). Thermodynamically controlled reactions for making macrocycles as well as oligomers in the absence of templates are also discussed.     

Universal pion freeze-out in heavy-ion collisions

Based on an evaluation of data on pion interferometry and on particle yields at midrapidity, we propose a universal condition for thermal freeze-out of pions in heavy-ion collisions. We show that freeze-out occurs when the mean free path of pions lambda(f) reaches a value of about 1 fm, which is much smaller than the spatial extent of the system at freeze-out. This critical mean free path is independent of the centrality of the collision and beam energy from the Alternating Gradient Synchrotron to the Relativistic Heavy Ion Collider.     

Model-Independent Normalization Condition for Gamow Vectors

Two comments on the theory of Gamow states are presented. First, it is shown that Gamow states may be viewed as two resonating states which correspond to two different eigenproblems for the same real value of energy. Second, a universal normalization condition for all Gamow states is derived.     

Lower Rim Substituted p-tert-Butyl Calix[4]arenes (V). Synthesis of New 5,11,17,22-tetrakis-p-tert-Butyl-25,27-bis(methoxy)- 26,28-bis(dialkoxyphosphorylmethoxy)calix[4]arenes and Cation Complexation Studies in Ion-Selective Membrane Electrodes

The synthesis and characterization of the lower rim bis-phosphorylatedtetrakis-p-tert-butyl-25,27-bis(methoxy)calix[4]arenas(compounds 2–4) is presented. The studied compounds were examined as ionophores in ion-selective membrane electrodes, showing selectivity for rubidium, potassium, and for the large and flat guanidinium cations (G⁺). The correlation wasstudied between the stereochemical structure of the ligands andpotentiometrically determined ion-selectivity. Complex formationconstants in the PVC/BEHS (bis(ethyl)hexyl sebacate) membranes weredetermined. The crystal and molecular structures of compound 4 have been determined by single crystal X-ray diffraction study.     

An efficient synthesis of vinylsilanes from acylsilanes and alkyl 1-phenyl-1H-tetrazol-5-yl sulfones. Brook vs Smiles rearrangement

[reaction: see text] Vinylsilanes are formed in high yields in the reaction of representative acyl(trimethyl)silanes with anions generated from Kocienski's sulfones.