Crosscut-Simplicial Lattices

We call a finite lattice crosscut-simplicial if the crosscut complex of every nuclear interval is equal to the boundary of a simplex. Every interval of such a lattice is either contractible or homotopy equivalent to a sphere. Recently, Hersh and Mészáros introduced SB-labelings and proved that if a lattice has an SB-labeling then it is crosscut-simplicial. Some known examples of lattices with a natural SB-labeling include the join-distributive lattices, the weak order of a Coxeter group, and the Tamari lattice. Generalizing these three examples, we prove that every meet-semidistributive lattice is crosscut-simplicial, though we do not know whether all such lattices admit an SB-labeling. While not every crosscut-simplicial lattice is meet-semidistributive, we prove that these properties are equivalent for chamber posets of real hyperplane arrangements.     

One‐dimensional chains in sodium tetraphenylphosphonium bis(2‐mercapto‐4‐methylphenolato‐O,S)oxovanadate(IV)

The title compound, Na(C₂₄H₂₀P)[V(C₇H₆OS)₂O], contains oxovanadium(IV) in a square‐pyramidal coordination geometry with a basal plane consisting of a cis‐S₂O₂ donor group. The [VO(mmp)₂]^2? (mmpH₂ = 2‐mercapto‐4‐methyl­phenol) units are linked into infinite chains by the sodium ions.     

Observation of occupation and dispersion of 2π1 associated states for CO adsorbed on Cu{100}

Angle-resolved photoemission observations of CO adsorbed on Cu{100} to form the (√2 × √2)R45° structure show emission from a CO 2π¹ related state away from the centre of the surface Brillouin zone. These observations are shown to be compatible with the anticipated dispersion of such states and with weak 2π¹ backbonding on this substrate.     

Homotopy Type of Intervals of the Second Higher Bruhat Orders

The higher Bruhat order is a poset generalizing the weak order on permutations. Another special case of this poset is an ordering on simple wiring diagrams. For this case, we prove that every interval is either contractible or homotopy equivalent to a sphere. This partially proves a conjecture due to Reiner. Our proof uses some tools developed by Felsner and Weil to study wiring diagrams.     

Direct equilibration of soil water for delta(18)O analysis and its application to tracer studies

Current methods for stable oxygen isotopic (delta (18)O) analysis of soil water rely on separation of water from the soil matrix before analysis. These separation procedures are not only time consuming and require relatively large samples of soil, but also have been shown to introduce a large potential source of error. Current research at Queen's University Belfast is focused on using direct equilibration of CO(2) with the pore water to eliminate this extraction step using the automated Multiprep system and a Micromass Prism III isotope ratio mass spectrometer (IRMS). The findings of this research indicate the method is less time consuming, more reliable, and reproducible to within accepted limits (+/-0.1% per thousand delta (18)O). In this study the direct equilibration method is used to analyse delta (18)O tracer profiles in the unsaturated zone of field soils, concurrently with chloride tracer profiles, which can be used to assess infiltration rates and mechanisms through the unsaturated zone. Copyright 1999 John Wiley & Sons, Ltd.     

Some physical properties of cubic boron

Crystal of a cubic form of boron have been produced in a plasma torch. In a search for superconductivity, which was negative, the cubic structure was found to be stable up to 10⁴ MPa (100 kbar) at a temperature of 0.04 K.     

Analysis of the interactions between He+ ions and transition metal surfaces using co-axial impact collision ion scattering spectroscopy

The interactions between low energy He⁺ ions and a series of transition metal surfaces have been studied using co-axial impact collision ion scattering spectroscopy (CAICISS). Experimental data were collected from the Ni(110), Cu(100), Pd(111), Pt(111) and Au(111) surfaces using ion beams with primary energies between 1.5 keV and 4.0 keV. The shadow cone radii deduced from the experimental surface peak positions were found to closely match theoretical predictions. Data analysis was performed using both the FAN and Kalypso simulation codes, revealing a consistent requirement for a reduction of 0.252 in the screening length correction in the Molière approximation within the Thomas–Fermi (TFM) interaction potential. The adjustments of the screening length in the TFM potential, predicted by O'Connor, and the uncorrected Ziegler–Biersack–Littmark (ZBL) potential both yielded inaccurate results for all of the surfaces and incident energies studied. We also provide evidence that, despite their different computational methodologies, the FAN and Kalypso simulation codes generate similar results given identical input parameters for the analysis of 180° backscattering spectra.