Effects of quenched impurities on surface diffusion, spreading, and ordering of O/W(110)

We study how quenched impurities affect the surfacediffusion and ordering of strongly interactingadsorbate atoms on surfaces. To this end, we carry out Monte Carlo simulations for a lattice-gas model of O/W(110), including small concentrations of immobile impurities which block their adsorption sites. We examine the behavior of the diffusion coefficients and order parameters as a function of coverage corresponding to various ordered phases at low temperatures. The effects of impurities are examined under both equilibrium and nonequilibrium conditions, and the results are compared to recent studies on a completely clean surface. We find that even minute impurity concentrations affect the diffusion behavior considerably in equilibrium. The effects are strongest in ordered phases and close to phase boundaries, where quenched impurities lead to a reduction of order, which in turn leads to significant changes in the collective diffusion and phase behavior. As the impurity concentration is increased to a level of a few percent of the total surface area, the reduction in order becomes particularly prominent at high coverages. Further studies under nonequilibrium conditions reveal that nonequilibrium effects are strong in the absence of impurities, while for surfaces covered by impurities the nonequilibrium effects are relatively weaker.Peer reviewe

Lattice Green functions in all dimensions

We give a systematic treatment of lattice Green functions (LGF) on the $d$-dimensional diamond, simple cubic, body-centred cubic and face-centred cubic lattices for arbitrary dimensionality $d \ge 2$ for the first three lattices, and for $2 \le d \le 5$ for the hyper-fcc lattice. We show that there is a close connection between the LGF of the $d$-dimensional hypercubic lattice and that of the $(d-1)$-dimensional diamond lattice. We give constant-term formulations of LGFs for all lattices and dimensions. Through a still under-developed connection with Mahler measures, we point out an unexpected connection between the coefficients of the s.c., b.c.c. and diamond LGFs and some Ramanujan-type formulae for $1/\pi.$Comment: 30 page

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Political Scienc

Cost-effectiveness of lung transplantation in The Netherlands: a scenario analysis

STUDY OBJECTIVES: To calculate cost-effectiveness of scenarios concerning lung transplantation in The Netherlands. DESIGN: Microsimulation model predicting survival, quality of life, and costs with and without transplantation program, based on data of the Dutch lung transplantation program of 1990 to 1995. SETTING: Netherlands, University Hospital Groningen. PATIENTS: Included were 425 patients referred for lung transplantation, of whom 57 underwent transplantation. INTERVENTION: Lung transplantation. RESULTS: For the baseline scenario, the costs per life-year gained are G 194,000 (G=Netherlands guilders) and the costs per quality-adjusted life-year (QALY) gained are G 167,000. Restricting patient inflow ("policy scenario") lowers the costs per life-year gained: G 172,000 (costs per QALY gained: G 144,000). The supply of more donor lungs could reduce the costs per life-year gained to G 159,000 (G 135,000 per QALY gained; G1 =US $0.6, based on exchange rate at the time of the study). CONCLUSIONS: Lung transplantation is an expensive but effective intervention: survival and quality of life improve substantially after transplantation. The costs per life-year gained are relatively high, compared with other interventions and other types of transplantation. Restricting the patient inflow and/or raising donor supply improves cost-effectiveness to some degree. Limiting the extent of inpatient screening or lower future costs of immunosuppressives may slightly improve the cost-effectiveness of the program

One-pot synthesis, crystallization and deracemization of isoindolinones from achiral reactants

The synthesis, crystallization, and complete solid-state deracemization of isoindolinones was realized in one pot simply by grinding achiral reaction components in a suitable solvent with an achiral catalyst. Previously, this concept was applied to a reversible reaction, but herein we showed that it could also be used in combination with reactions in which product formation is irreversible. A controlled final configuration of the product was obtained by using small amounts of chiral additives or seed crystals of the product

A Note on Computations of D-brane Superpotential

We develop some computational methods for the integrals over the 3-chains on the compact Calabi-Yau 3-folds that plays a prominent role in the analysis of the topological B-model in the context of the open mirror symmetry. We discuss such 3-chain integrals in two approaches. In the first approach, we provide a systematic algorithm to obtain the inhomogeneous Picard-Fuchs equations. In the second approach, we discuss the analytic continuation of the period integral to compute the 3-chain integral directly. The latter direct integration method is applicable for both on-shell and off-shell formalisms.Comment: 61 pages, 5 figures; v2: typos corrected, minor changes, references adde

Diamond deposition on modified silicon substrates: Making diamond atomic force microscopy tips for nanofriction experiments

Fine-crystalline diamond particles are grown on standard Si atomic force microscopy tips, using hot filament-assisted chemical vapor deposition. To optimize the conditions for diamond deposition, first a series of experiments is carried out using silicon substrates covered by point-topped pyramids as obtained by wet chemical etching. The apexes and the edges of the silicon pyramids provide favorable sites for diamond nucleation and growth. The investigation of the deposited polycrystallites is done by means of optical microscopy, scanning electron microscopy and micro-Raman spectroscopy. The resulting diamond-terminated tips are tested in ultra high vacuum using contact-mode atomic force microscope on a stepped surface of sapphire showing high stability, sharpness, and hardnes

Voorwaarts met de milieuprestaties van de Nederlandse open-teelt sectoren: een verkenning naar 2020 ten behoeve van 'Telen met toekomst'

Dit rapport beschrijft het overheidsbeleid voor landbouw en milieu op het gebied van nutriënten en gewasbeschermingsmiddelen, en de daaruit afgeleide doelen welke voor de bedrijven binnen 'Telen met toekomst' gesteld zullen worden. Verder worden beschreven de huidige milieuprestaties van de vier sectoren en de tekortkomingen ten aanzien van milieudoelstellingen en oplossingsrichtingen om de gestelde doelen te kunnen gaan voldoe

Holonomic functions of several complex variables and singularities of anisotropic Ising n-fold integrals

Lattice statistical mechanics, often provides a natural (holonomic) framework to perform singularity analysis with several complex variables that would, in a general mathematical framework, be too complex, or could not be defined. Considering several Picard-Fuchs systems of two-variables "above" Calabi-Yau ODEs, associated with double hypergeometric series, we show that holonomic functions are actually a good framework for actually finding the singular manifolds. We, then, analyse the singular algebraic varieties of the n-fold integrals $\chi^{(n)}$, corresponding to the decomposition of the magnetic susceptibility of the anisotropic square Ising model. We revisit a set of Nickelian singularities that turns out to be a two-parameter family of elliptic curves. We then find a first set of non-Nickelian singularities for $\chi^{(3)}$ and $\chi^{(4)}$, that also turns out to be rational or ellipic curves. We underline the fact that these singular curves depend on the anisotropy of the Ising model. We address, from a birational viewpoint, the emergence of families of elliptic curves, and of Calabi-Yau manifolds on such problems. We discuss the accumulation of these singular curves for the non-holonomic anisotropic full susceptibility.Comment: 36 page