Density-functional theory of positronium and electron bubbles in helium fluids

The density-functional method is applied to excess electrons and positronium atoms in helium fluids. The self-trapping is investigated in a fully self-consistent fashion, and formulas are given for the particle energy and Ps pick-off annihilation rate in quasifree as well as localized states. The numerical results compare well with experimental data. However, the need for a more sophisticated treatment of threshold effects near the onset of bubble formation is indicated.Peer reviewe

Nitrogen deposition does not enhance Sphagnum decomposition

Long-term additions of nitrogen (N) to peatlands have altered bryophyte growth, species dominance, N content in peat and peat water, and often resulted in enhanced Sphagnum decomposition rate. However, these results have mainly been derived from experiments in which N was applied as ammonium nitrate (NH4NO3), neglecting the fact that in polluted areas, wet deposition may be dominated either by NO3- or NH4+. We studied effects of elevated wet deposition of NO3- vs. NH4+ alone (8 or 56 kg N ha(-1) yr(-1) over and above the background of 8 kg N ha(-1) yr(-1) for 5 to 11 years) or combined with phosphorus (P) and potassium (K) on Sphagnum quality for decomposers, mass loss, and associated changes in hummock pore water in an ombrotrophic bog (Whim). Adding N, especially as NH4+, increased N concentration in Sphagnum, but did not enhance mass loss from Sphagnum. Mass loss seemed to depend mainly on moss species and climatic factors. Only high applications of N affected hummock pore water chemistry, which varied considerably over time. Overall, C and N cycling in this N treated bog appeared to be decoupled. We conclude that moss species, seasonal and annual variation in climatic factors, direct negative effects of N (NH4+ toxicity) on Sphagnum production, and indirect effects (increase in pH and changes in plant species dominance under elevated NO3- alone and with PK) drive Sphagnum decomposition and hummock C and N dynamics at Whim. (C) 2016 Elsevier B.V. All rights reserved.Peer reviewe

Distribution of lipid nanocapsules in different cochlear cell populations after round window membrane permeation

Hearing loss is a major public health problem, and its treatment with traditional therapy strategies is often unsuccessful due to limited drug access deep in the temporal bone. Multifunctional nanoparticles that are targeted to specified cell populations, biodegradable, traceable in vivo, and equipped with controlled drug/gene release may resolve this problem. We developed lipid core nanocapsules (LNCs) with sizes below 50 nm. The aim of the present study is to evaluate the ability of the LNCs to pass through the round window membrane and reach inner ear targets. FITC was incorporated as a tag for the LNCs and Nile Red was encapsulated inside the oily core to assess the integrity of the LNCs. The capability of LNCs to pass through the round window membrane and the distribution of the LNCs inside the inner ear were evaluated in rats via confocal microscopy in combination with image analysis using ImageJ. After round window membrane administration, LNCs reached the spiral ganglion cells, nerve fibers, and spiral ligament fibrocytes within 30 min. The paracellular pathway was the main approach for LNC penetration of the round window membrane. LNCs can also reach the vestibule, middle ear mucosa, and the adjacent artery. Nuclear localization was detected in the spiral ganglion, though infrequently. These results suggest that LNCs are potential vectors for drug delivery into the spiral ganglion cells, nerve fibers, hair cells, and spiral ligament

Thermal expansion in small metal clusters and its impact on the electric polarizability

The thermal expansion coefficients of $\mathrm{Na}_{N}$ clusters with $8 \le N \le 40$ and $\mathrm{Al}_{7}$, $\mathrm{Al}_{13}^-$ and $\mathrm{Al}_{14}^-$ are obtained from {\it ab initio} Born-Oppenheimer LDA molecular dynamics. Thermal expansion of small metal clusters is considerably larger than that in the bulk and size-dependent. We demonstrate that the average static electric dipole polarizability of Na clusters depends linearly on the mean interatomic distance and only to a minor extent on the detailed ionic configuration when the overall shape of the electron density is enforced by electronic shell effects. The polarizability is thus a sensitive indicator for thermal expansion. We show that taking this effect into account brings theoretical and experimental polarizabilities into quantitative agreement.Comment: 4 pages, 2 figures, one table. Accepted for publication in Physical Review Letters. References 10 and 23 update

Chemical Equilibration and Transport Properties of Hadronic Matter near TcT_c

We discuss how the inclusion of Hagedorn states near $T_c$ leads to short chemical equilibration times of proton anti-proton pairs, $K\bar{K}$ pairs, and $\Lambda\bar{\Lambda}$ pairs, which indicates that hadrons do not need to be "born" into chemical equilibrium in ultrarelativistic heavy ion collisions. We show that the hadron ratios computed within our model match the experimental results at RHIC very well. Furthermore, estimates for $\eta/s$ near $T_c$ computed within our resonance gas model are comparable to the string theory viscosity bound $\eta/s=1/4\pi$. Our model provides a good description of the recent lattice results for the trace anomaly close to $T_c=196$ MeV.Comment: 4 pages, 3 figures, to appear in the conference proceedings for Quark Matter 2009, March 30 - April 4, Knoxville, Tennesse

Designing multiplayer games to facilitate emergent social behaviours online

This paper discusses an exploratory case study of the design of games that facilitate spontaneous social interaction and group behaviours among distributed individuals, based largely on symbolic presence 'state' changes. We present the principles guiding the design of our game environment: presence as a symbolic phenomenon, the importance of good visualization and the potential for spontaneous self-organization among groups of people. Our game environment, comprising a family of multiplayer 'bumper-car' style games, is described, followed by a discussion of lessons learned from observing users of the environment. Finally, we reconsider and extend our design principles in light of our observations

Composition and temporal behavior of ambient ions in the boreal forest

A recently developed atmospheric pressure interface mass spectrometer (APi-TOF) measured the negative and positive ambient ion composition at a boreal forest site. As observed in previous studies, the negative ions were dominated by strong organic and inorganic acids (e.g. malonic, nitric and sulfuric acid), whereas the positive ions consisted of strong bases (e.g. alkyl pyridines and quinolines). Several new ions and clusters of ions were identified based on their exact masses, made possible by the high resolution, mass accuracy and sensitivity of the APi-TOF. Time series correlograms aided in peak identification and assigning the atomic compositions to molecules. Quantum chemical calculations of proton affinities and cluster stabilities were also used to confirm the plausibility of the assignments. Acids in the gas phase are predominantly formed by oxidation in the gas phase, and thus the concentrations are expected to vary strongly between day and night. This was also the case in this study, where the negative ions showed strong diurnal behavior, whereas the daily changes in the positive ions were considerably smaller. A special focus in this work was the changes in the ion distributions occurring during new particle formation events. We found that sulfuric acid, together with its clusters, dominated the negative ion spectrum during these events. The monomer (HSO<sub>4</sub><sup>−</sup>) was the largest peak, together with the dimer (H<sub>2</sub>SO<sub>4</sub> · HSO<sub>4</sub><sup>−</sup>) and trimer ((H<sub>2</sub>SO<sub>4</sub>)<sub>2</sub> · HSO<sub>4</sub><sup>−</sup>). SO<sub>5</sub><sup>−</sup> also tracked HSO<sub>4</sub><sup>−</sup> at around 20% of the HSO<sub>4</sub><sup>−</sup> concentration at all times. During the strongest events, the tetramer and a cluster with the tetramer and ammonia were also detected. Quantum chemical calculations predict that sulfuric acid clusters containing ammonia are much more stable when neutral, thus the detection of a single ion cluster implies that ammonia can be an important compound in the nucleation process. We also believe to have made the first observations of an organosulfate (glycolic acid sulfate) in the gas phase. This ion, and its cluster with sulfuric acid, correlates with the HSO<sub>4</sub><sup>−</sup>, but peaks in the early afternoon, some hours later than HSO<sub>4</sub><sup>−</sup> itself. A list of all identified ions is presented in the supplementary material, and also a list of all detected masses not yet identified

Probe the QCD phase diagram with \phi-mesons in high energy nuclear collisions

High-energy nuclear collision provide a unique tool to study the strongly interacting medium. Recent results from the Relativistic Heavy Ion Collider (RHIC) on \phi-meson production has revealed the formation of a dense partonic medium. The medium constituents are found to exhibit collective behaviour initiated due to partonic interactions in the medium. We present a brief review of the recent results on \phi production in heavy-ion collisions at RHIC. One crucial question is where, in the phase diagram, does the transition happen for the matter changing from hadronic to partonic degrees of freedom. We discuss how \phi-meson elliptic flow in heavy-ion collisions can be used for the search of the QCD phase boundary.Comment: Plenary talk at Strange Quark Matter 2008, Beijing China, 6-10 October 2008. To appear in proceedings of SQM200