Gamow-Teller strength in the exotic odd-odd nuclei 138La and 180Ta and its relevance for neutrino nucleosynthesis

The Gamow-Teller strength distributions below the particle threshold in 138La and 180Ta, deduced from high-resolution measurements of the (3He,t) reaction at 0 degrees, allow us to evaluate the role of charged-current reactions for the production of these extremely rare nuclides in neutrino-nucleosynthesis models. The analysis suggests that essentially all 138La in the Universe can be made that way. Neutrino nucleosynthesis also contributes significantly to the abundance of 180Ta but the magnitude depends on the unknown branching ratio for population of the long-lived isomer.     

Role of nuclear motion in double ionization of molecular hydrogen by a single photon

We examine the origin of recently observed variations with internuclear distance (R) of the fully differential cross sections for double ionization of aligned H2 by absorption of a single photon. Using the results of fully converged numerical solutions of the Schr?dinger equation, we show that these variations arise primarily from pronounced differences in the R dependence of the parallel and perpendicular components of the ionization amplitude. We also predict that R dependences should be readily observable in the asymmetry parameter for photodouble ionization, even in experimental measurements that are not differential in the energy sharings between ejected photoelectrons.     

Fermion family recurrences in the Dyson–Schwinger formalism

We study the multiple solutions of the truncated propagator Dyson–Schwinger equation for a simple fermion theory with Yukawa coupling to a scalar field. Upon increasing the coupling constant g, other parameters being fixed, more than one non-perturbative solution breaking chiral symmetry becomes possible and we find these numerically. These “recurrences” appear as a mechanism to generate different fermion generations as quanta of the same fundamental field in an interacting field theory, without assuming any composite structure. The number of recurrences or flavors is reduced to the question of the value of the Yukawa coupling, and it has no special profound significance in the standard model. The resulting mass function can have one or more nodes and the measurement that potentially detects them can be thought of as a collider-based test of the virtual dispersion relation for the charged lepton member of each family. This requires the three independent measurements of the charged lepton’s energy, three-momentum and off-shellness. We illustrate how this can be achieved for the (more difficult) case of the tau lepton. PACS 12.15.Ff; 11.30.Rd     

Photo-induced Fluorescence of Fluometuron in a Continuous-flow Multicommutation Assembly

This paper deals with the photo-induced fluorimetric determination of the herbicide Fluometuron with the aid of a continuous-flow assembly of the emergent and new methodology known as Multicommutation which was provided with an on-line photoreactor. Maximum fluorescence intensity was observed at basic pH solutions, 1×10⁻⁴ mol l⁻¹ NaOH, after 1.4 min of irradiation and being the maximum at λ_exc 247.0 nm and λ_em 325.0 nm. The influence of different experimental parameters either chemical (pH, surfactants presence, solvent polarity and temperature) or hydrodynamic (time of photo-degradation, size and number of different segments and flow-rate) was tested. The linear dynamic range was from 0.01 to 4.0 mg l⁻¹ of Fluometuron; the inter-day reproducibility (as R.S.D.) of the slope was 0.001% and 1.7% from the peaks intra-day reproducibility. A large series of potential interferents was studied and finally the method was applied to human urine, soil, formulation and water samples.     

Stability of AgIII towards Halides in Organosilver(III) Complexes

The involvement of silver in two-electron Ag^I/Ag^III processes is currently emerging. However, the range of stability of the required and uncommon Ag^III species is virtually unknown. Here, the stability of Ag^III towards the whole set of halide ligands in the organosilver(III) complex frame [(CF₃)₃AgX]⁻ (X=F, Cl, Br, I, At) is theoretically analyzed. The results obtained depend on a single factor: the nature of X. Even the softest and least electronegative halides (I and At) are found to form reasonably stable Ag^III−X bonds. Our estimates were confirmed by experiment. The whole series of nonradiative halide complexes [PPh₄][(CF₃)₃AgX] (X=F, Cl, Br, I) has been experimentally prepared and all its constituents have been isolated in pure form. The pseudohalides [PPh₄][(CF₃)₃AgCN] and [PPh₄][(CF₃)₃Ag(N₃)] have also been isolated, the latter being the first silver(III) azido complex. Except for the iodo compound, all the crystal and molecular structures have been established by single-crystal X-ray diffraction methods. The decomposition paths of the [(CF₃)₃AgX]⁻ entities at the unimolecular level have been examined in the gas phase by multistage mass spectrometry (MSⁿ). The experimental detection of the two series of mixed complexes [CF₃AgX]⁻ and [FAgX]⁻ arising from the corresponding parent species [(CF₃)₃AgX]⁻ demonstrate that the Ag−X bond is particularly robust. Our experimental observations are rationalized with the aid of theoretical methods. Smooth variation with the electronegativity of X is also observed in the thermolyses of bulk samples. The thermal stability in the solid state gradually decreases from X=F (145 °C, dec.) to X=I (78 °C, dec.) The experimentally established compatibility of Ag^III with the heaviest halides is of particular relevance to silver-mediated or silver-catalyzed processes.     

Engineered pixels using active plasmonic holograms with liquid crystals

Digital holography requires arrays of small reconfigurable elements to achieve complex reconstruction of the hologram with common systems based on pixels utilizing liquid crystal on silicon (LCoS) technology. The backplane of a typical pixel element is potentially underutilized and thus relatively large physical areas exist in which information can be stored and exploited to give additional functionality to pixel elements. Polarisation and wavelength dependent optical properties can be achieved in small areas using the plasmonic effects of optical antennae. The integration of LCs with optical antennae‐based plasmonic holograms allows active modulation of the far field pattern. The work here demonstrates the concept that conventional LCoS pixel elements can be greatly enhanced with the integration of plasmonic holograms, composed of optical antennae patterned on the surface, giving rise to new levels of modulation capability for holographic pixel elements. Using LCs, polarisation dependent effects in plasmonic holograms can be switched. ‘Engineered pixels', with sub‐wavelength multiplexing over both polarisation and wavelength, can increase the channel capacity of a typical LC display device. (© 2015 WILEY‐VCH Verlag GmbH &Co. KGaA, Weinheim)     

DFT analysis: Fe4 cluster and Fe(110) surface interaction studies with pyrrole,furan, thiophene,and selenophene molecules

DFT studies of both the Fe₄ cluster and the Fe(110) surface interaction with pyrrole, furan, thiophene, and selenophene showed that selenophene forms a stabler adsorbate iron complex than the other heterocyclic molecules; this is consistent with the binding energy data that were calculated between the Fe cluster and the Fe(110) surface with the heterocycles. Furthermore, when the adsorption of the compounds with the iron cluster was analyzed by molecular orbital studies, the orbitals of selenophene overlapped more strongly with the Fe atom than that of the other molecules. In TD-DFT, the π → π* peak observed for the molecules disappeared when they formed complexes, and there appeared a charge transfer band (ligand to metal), thus confirming the coordination of these molecules with the cluster. The data suggest that the chemisorption is an exothermic process.     

Analysis of the Lipidome of Xenografts Using MALDI-IMS and UHPLC-ESI-QTOF

Human tumor xenografts in immunodeficient mice are a very popular model to study the development of cancer and to test new drug candidates. Among the parameters analyzed are the variations in the lipid composition, as they are good indicators of changes in the cellular metabolism. Here, we present a study on the distribution of lipids in xenografts of NCI-H1975 human lung cancer cells, using MALDI imaging mass spectrometry and UHPLC-ESI-QTOF. The identification of lipids directly from the tissue by MALDI was aided by the comparison with identification using ESI ionization in lipid extracts from the same xenografts. Lipids belonging to PCs, PIs, SMs, DAG, TAG, PS, PA, and PG classes were identified and their distribution over the xenograft was determined. Three areas were identified in the xenograft, corresponding to cells in different metabolic stages and to a layer of adipose tissue that covers the xenograft.

Synthesis and Conformational Analysis of Cyclic Homooligomers from Pyranoid ε‐Sugar Amino Acids

New pyranoid ε‐sugar amino acids were designed as building blocks, in which the carboxylic acid and the amine groups were placed in positions C2 and C3 with respect to the tetrahydropyran oxygen atom. By using standard solution‐phase coupling procedures, cyclic homooligomers containing pyranoid ε‐sugar amino acids were synthesized. Conformation analysis was performed by using NMR spectroscopic experiments, FTIR spectroscopic studies, X‐ray analysis, and a theoretical conformation search. These studies reveal that the presence of a methoxy group in the position C4 of the pyran ring produces an important structural change in the cyclodipeptides. When the methoxy groups are present, the structure collapses through interresidue hydrogen bonds between the oxygen atoms of the pyran ring and the amide protons. However, when the cyclodipeptide lacks the methoxy groups, a U‐shape structure is adopted, in which there is a hydrophilic concave face with four oxygen atoms and two amide protons directed toward the center of the cavity. Additionally, we found important evidence of the key role played by weak electrostatic interactions, such as the five‐membered hydrogen‐bonded pseudocycles (C₅) between the amide protons and the ether oxygen atoms, in the conformation equilibrium of the macrocycles and in the cyclization step of the cyclic tetrapeptides.