Quantum Monte Carlo study of the H- impurity in small helium clusters

We report ground state energies and structural properties for small helium clusters (4He) containing an H- impurity computed by means of variational and diffusion Monte Carlo methods. Except for 4He_2H- that has a noticeable contribution from collinear geometries where the H- impurity lies between the two 4He atoms, our results show that our 4He_NH- clusters have a compact 4He_N subsystem that binds the H- impurity on its surface. The results for $N\geq 3$ can be interpreted invoking the different features of the minima of the He-He and He-H- interaction potentials.Comment: 12 pages, 7 Ps figure

Hydrophobic aggregation and collective absorption of dioxin into lipid membranes: insights from atomistic simulations

Dioxins are a highly toxic class of chlorinated aromatic chemicals. They have been extensively studied, but several molecular-level details of their action are still missing. Here we present molecular dynamics simulations of their absorption and diffusion through cell membranes. We show that, due to their hydrophobic character, dioxins can quickly penetrate into a lipid membrane, both as single molecules and as aggregates. We find clear evidence for their ability to accumulate in cell membranes. Our free energy calculations indicate that subsequent transport into the cell is unlikely to be a simple diffusive process

Positron and positronium chemistry by quantum Monte Carlo. VI. The ground state of LiPs, NaPs, e(+)Be, and e(+)Mg

The ground states of the positronic complexes LiPs, NaPs, e(+)Be, e(+)Mg, and of the parent ordinary-matter systems have been simulated by means of the all-electron fixed-node diffusion Monte Carlo (DMC) method. Positron affinities and positronium binding energies are computed by direct difference between the DMC energy results. LiPs was recomputed in order to test the possibility of approximating the electron-positron Coulomb potential with a model one that does not diverge for r=0, finding accurate agreement with previous DMC results. As to e(+)Be, the effect due to the near degeneracy of the 1s(2)2s(2) and 1s(2)2p(2) configurations in Be is found to be relevant also for the positron affinity, and is discussed on the basis of the change in the ionization potential and the dipole polarizability. The DMC estimate of the positron affinity of Mg, a quantity still under debate, is 0.0168(14) hartree, in close agreement with the value 0.015 612 hartree computed by Mitroy and Ryzhihk [J. Phys. B. 34, 2001 (2001)] using explicitly correlated Gaussians. (C) 2002 American Institute of Physics

Experimental Analysis of Failure Mechanisms in Masonry-PFRP Profiles Connections

Fibre-reinforced polymer (FRP) profiles, with their low density, high durability, and ease of construction, are particularly suitable for the retrofit of traditional masonry structures, particularly historic constructions in seismic zones. However, a critical aspect of this new technology application is the connection between FRP profiles and masonry walls. So far, no research studies are available on this subject. The authors carried out a preliminary experimental campaign on different connection systems between masonry and pultruded glass-fibre-reinforced polymer (GFRP) profiles. The note presents the immediate results of this study, focusing on the performance and collapse mechanisms; the study may contribute to the development of an effective connection system between masonry and FRP profiles to be adopted in the retrofitting of existing building with juxtaposed FRP frames

From dioxin to dioxin congeners: understanding the differences in hydrophobic aggregation in water and absorption into lipid membranes by means of atomistic simulations

Translocation of small molecules through a cell membrane barrier is a fundamental step to explain the response of cells to foreign molecules. Investigating the mechanisms through which this complex process takes place is especially important in the study of the adverse effects of toxicants. In this work, we start from the results of a previous simulation study of the mechanism of dioxin (2,3,7,8-tetrachlorodibenzo-p-dioxin) absorption into a model membrane, and extend it to four structural congeners of dioxin. The new molecules have been chosen taking into consideration the structural features that characterize dioxin: aromaticity, planarity, the presence of chlorine and oxygen atoms, and hydrophobicity. Our results for the absorption mechanism confirm our expectations based on the chemical structures, but also reveal some interesting differences in single-molecules and especially in cooperative actions underlying cluster absorption. The analysis of key parameters, such as free energies of transfer and translocation times, supports the idea that dioxin, more than its congeners investigated here, likely accumulates in cell membranes

ReActive: Exploring Hybrid Interactive Materials in Craftsmanship

This paper presents ReActive, a design exploration aimed at embedding interactivity in traditional materials by artisanal processes. In the attempt to reconciling technology with human experience and tradition, we experimented with artisans to understand how craftsmanship can embrace technological innovations while at the same time maintaining its nature and value. We built samples of hybrid materials, where electronics and smart materials are embedded in traditional ones, in order to make them reactive and interactive. We discuss implications and new possibilities offered by these new hybrid materials both for artisans and users and new perspectives for interaction design

Expression of and immune responses to leukemia antigens in patients with hematological malignancies

Leukemia cells are characterized by differentially expressed leukemia-associated antigens (LAAs). We wondered whether the expression of the LAAs WT1 and RHAMM as well as the T cellular immune response to these LAAs correlated with the clinical outcome of patients suffering from leukemia. We investigated the expression of WT1 and RHAMM at RNA level using qPCR before and after treatment. We concluded that WT1 is a suitable marker for MRD after allogeneic SCT and that a WT1-specific T cell response might contribute to the maintenance of CR