Electron capture to continuum in collisions of bare projectiles with Ne targets

Abstract. We have investigated the cusp resulting from electron capture to the continuum of 1.25-5 MeV m u- ' fully stripped hydrogen and oxygen as a function of the collision energy and the detector angular resolution B o. It is revealed that the characteristic cusp shape parameters depend strongly on the experimental resolution. Our experimental data are "pared with the second-order Born theory and the impulse approximation. Both theories mnhrm the 8, dependence of the shape parameters and gjve a reasonable descrip-lion of the cusp asymmetry. However, theory tends to overestimate the absolute cross sections, in particular in the case of oxygen. 1

Electron-spectroscopic investigation of metal-insulator transition in Sr2Ru1-xTixO4 (x=0.0-0.6)

We investigate the nature and origin of the metal-insulator transition in Sr2Ru1-xTixO4 as a function of increasing Ti content (x). Employing detailed core, valence, and conduction band studies with x-ray and ultraviolet photoelectron spectroscopies along with Bremsstrahlung isochromat spectroscopy, it is shown that a hard gap opens up for Ti content greater than equal to 0.2, while compositions with x<0.2 exhibit finite intensity at the Fermi energy. This establishes that the metal-insulator transition in this homovalent substituted series of compounds is driven by Coulomb interaction leading to the formation of a Mott gap, in contrast to transitions driven by disorder effects or band flling.Comment: Accepted for publication in Phys. Rev.

Relationship between hippocampal structure and memory function in elderly humans

With progressing age, the ability to recollect personal events declines, whereas familiarity-based memory remains relatively intact. It has been hypothesized that age-related hippocampal atrophy may contribute to this pattern because of its critical role for recollection in younger humans and after acute injury. Here, we show that hippocampal volume loss in healthy older persons correlates with gray matter loss (estimated with voxel-based morphometry) of the entire limbic system and shows no correlation with an electrophysiological (event-related potential [ERP]) index of recollection. Instead, it covaries with more substantial and less specific electrophysiological changes of stimulus processing. Age-related changes in another complementary structural measure, hippocampal diffusion, on the other hand, seemed to be more regionally selective and showed the expected correlation with the ERP index of recollection. Thus, hippocampal atrophy in older persons accompanies limbic atrophy, and its functional impact on memory is more fundamental than merely affecting recollection

A Record of Lateglacial and Early Holocene Environmental and Ecological Change from Southwestern Connecticut, USA

Analyses of a sediment core from Highstead Swamp in southwestern Connecticut, USA, reveal Lateglacial and early Holocene ecological and hydrological changes. Lateglacial pollen assemblages are dominated by Picea and Pinus subg. Pinus, and the onset of the Younger Dryas (YD) cold interval is evidenced by higher abundance of Abies and Alnus viridis subsp. crispa. As climate warmed at the end of the YD, Picea and Abies declined and Pinus strobus became the dominant upland tree species. A shift from lacustrine sediment to organic peat at the YD-Holocene boundary suggests that the lake that existed in the basin during the Lateglacial interval developed into a swamp in response to reduced effective moisture. A change in wetland vegetation from Myrica gale to Alnus incana subsp. rugosa and Sphagnum is consistent with this interpretation of environmental changes at the beginning of the HoloceneOther Research Uni

Pollen Morphology and Its Relationship to the Taxonomy of the Genus Sarracenia (Sarraceniaceae)

Despite nearly a century of research, the systematic relationships among North American pitcher plants in the genus Sarracenia (Sarraceniaceae) remain unresolved. In this study we analyzed pollen morphology of the 11 currently recognized species of Sarracenia and examined how variations in key pollen characteristics relate to our current understanding of the taxonomy of this genus. We used principal components analysis to explore variations in pollen grain size (equatorial diameter and length) and shape (number of colpi) among Sarracenia species, and used cluster analysis to compare systematic groupings of Sarracenia based on floral, vegetative, and pollen characters. We compared these results with a previously published phylogeny based on molecular data. Groupings based on pollen characteristics alone did not align completely with those based on molecular or all morphological data. In clusters based on pollen alone and those using all morphological characters, S. purpurea and S. rosea formed a single group, and S. flava, S. alata, and S. leucophylla grouped together consistently. The pollen morphology of S. jonesii and S. alabamensis differed substantially from that of S. rubra, supporting the current systematic treatment of the genus that recognizes these three taxa as distinct species.Other Research Uni

Structural investigation and compression of a co-crystal of indomethacin and saccharin

The co-crystalline structure of the non-steroidal, anti-inflammatory indomethacin with the non-toxic, Generally Regarded As Safe (GRAS) sweetener component saccharin was investigated up to 6.33 GPa using a Diamond Anvil Cell (DAC). Single crystal X-ray diffraction measurements show that the co-crystal remains in the same triclinic, P-1, phase throughout the compression with a significant reduction in void space (155.69 to 55.61Å3). Information on the response of different types of intermolecular interactions to external force at the same time is enabled by the use of a co-crystal. We have rationalised that the length and compression rate of the saccharin amide dimer in the co-crystal is caused by the dimer sitting in a ‘pocket’ surrounded by the indomethacin framework. This framework reduces the effects of molecular packing on the dimer allowing for an ideal hydrogen bonding geometry

Formation of quinol co-crystals with hydrogen-bond acceptors

The crystal structures of eight new co-crystals of quinol with pyrazine, piperazine, morpholine, pyridine, piperidine, 4,4'-bipyridine, N-methylmorpholine and N,N'-dimethylpiperazine are reported. Quinol forms 1: 1 co-crystals with pyrazine, piperazine and N, N'-dimethylpiperazine, but 1: 2 co-crystals with morpholine, 4,4'-bipyridine, N-methylmorpholine, pyridine and piperidine. This difference can be rationalized in most cases by the presence of, respectively, two or one strong hydrogen-bond acceptor(s) in the guest molecule. The exception to this generalization is 4,4'-bipyridine, which forms a 1: 2 co-crystal, possibly to optimize crystal packing. All structures are dominated by hydrogen bonding between quinol and the guest molecules. A doubly bridging motif, which connects pairs of quinol and guest molecules via NH...O or CH...O interactions, is present in all but the sterically hindered N, N'-dimethylpiperazine and N-methylmorpholine co-crystals

Formation of disclination lines near a free nematic interface

We have studied the nucleation and the physical properties of a -1/2 wedge disclination line near the free surface of a confined nematic liquid crystal. The position of the disclination line has been related to the material parameters (elastic constants, anchoring energy and favored anchoring angle of the molecules at the free surface). The use of a planar model for the structure of the director field (whose predictions have been contrasted to those of a fully three-dimensional model) has allowed us to relate the experimentally observed position of the disclination line to the relevant properties of the liquid crystals. In particular, we have been able to observe the collapse of the disclination line due to a temperature-induced anchoring angle transition, which has allowed us to rule out the presence of a real disclination line near the nematic/isotropic front in directional growth experiments. 61.30.Jf,61.30.G

Verification and intercomparison of reactive transport codes to describe root-uptake

Several mathematical models have been developed to simulate processes and interactions in the plant rhizosphere. Most of these models are based on a rather simplified description of the soil chemistry and interactions of plant roots in the rhizosphere. In particular the feedback loops between exudation, water and solute uptake are mostly not considered, although their importance in the bioavailability of mineral elements for plants has been demonstrated. The aim of this work was to evaluate three existing coupled speciation-transport tools to model rhizosphere processes. In the field of hydrogeochemistry, such␣computational tools have been developed to␣describe acid-base and redox reactions, complexation and ion exchange, adsorption and precipitation of chemical species in soils and aquifers using thermodynamic and kinetic relationships. We implemented and tested a simple rhizosphere model with three geochemical computational tools (ORCHESTRA, MIN3P, and PHREEQC). The first step was an accuracy analysis of the different solution strategies by comparing the numerical results to the analytical solution of solute uptake (K or Ca) by a single cylindrical root. All models are able to reproduce the concentration profiles as well as the uptake flux. The relative error of the simulated concentration profile decreases with increasing distance from the root. The uptake flux was simulated for all codes with less than 5% error for K and less than 0.4% for Ca. The strength of the codes presented in this paper is that they can also be used to investigate more complex and coupled biogeochemical processes in rhizosphere models. This is shown exemplarily with simulations involving both exudation and uptake and the simultaneous uptake of solute and wate