Cover Picture

The cover picture shows how thrombosis occurs in the deep veins of the lower limbs. Stasis, which results from slow and turbulent blood flow, combined with hypercoagulation, caused, for example, by a surgical procedure, may result in thrombus formation. The synthetic sulfated pentasaccharide shown in part is a potent antithrombotic compound that exerts its effect by activation of the plasma protein antithrombin III. Conformationally locked monosaccharides have now been synthesized to demonstrate that L-iduronic acid, one part of the pentasaccharide, must adopt an unusual distorted conformation to activate antithrombin III. Such conformational effects might be relevant in explaining the unique biological properties of glycosaminoglycans that contain L-iduronic acid. In the background of the picture, a flight of vampire bats is attracted by the pentasaccharide. Vampire was the name given to South American blood-sucking bats (Latin name: desmodus rotundus) in 1761 by the French naturalist Georges Louis Leclerc Comte de Buffon (1707-1788). These bats are known to attack cattle and, very rarely, sleeping human beings. Although their saliva has been shown to contain an anticoagulant compound, they would also be happy to benefit from the pentasaccharide mentioned above, to suck the blood out of the vein more easily. More details about this compound which would be helpful to vampire bats are reported by Petitou, Sina? et al. on p. 1670 ff.     

Equitable resolvable coverings

In an earlier article, Willem H. Haemers has determined the minimum number of parallel classes in a resolvable 2‐(qk,k,1) covering for all k ≥ 2 and q = 2 or 3. Here, we complete the case q = 4, by construction of the desired coverings using the method of simulated annealing. Secondly, we look at equitable resolvable 2‐(qk,k,1) coverings. These are resolvable coverings which have the additional property that every pair of points is covered at most twice. We show that these coverings satisfy k < 2q ? , and we give several examples. In one of these examples, k > q. © 2003 Wiley Periodicals, Inc. J Combin Designs 11: 113–123, 2003; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/jcd.10024     

Initial stages of oxidation of Cu(1 1 1)

Several surface analysis techniques were combined to study the initial stages of oxidation of Cu(1 1 1) surfaces exposed to O₂ at low pressure (<5 × 10⁻⁶ mbar) and room temperature. Scanning tunneling microscopy (STM) results show that the reactivity is governed by the restructuring of the Cu(1 1 1) surface. On the terraces, oxygen dissociative adsorption leads to the formation of isolated O adatoms and clusters weakly bound to the surface. The O adatoms are located in the fcc threefold hollow sites of the unrestructured terraces. Friedel oscillations with an amplitude lower than 5 pm have been measured around the adatoms. At step edges, surface restructuring is initiated and leads to the nucleation and growth of a two-dimensional disordered layer of oxide precursor. The electronic structure of this oxide layer is characterised by a band gap measured by scanning tunneling spectroscopy to be ∼1.5 eV wide. The growth of the oxide islands progresses by consumption of the upper metal terraces to form triangular indents. The extraction of the Cu atoms at this interface generates a preferential orientation of the interface along the close-packed directions of the metal. A second growth front corresponds to the step edges of the oxide islands and progresses above the lower metal terraces. This is where the excess Cu atoms extracted at the first growth front are incorporated. STM shows that the growing disordered oxide layer consists of units of hexagonal structure with a first nearest neighbour distance characteristic of a relaxed Cu-Cu distance (∼0.3 nm), consistent with local Cu₂O(1 1 1)-like elements. Exposure at 300 °C is necessary to form an ordered two-dimensional layer of oxide precursor. It forms the so-called “29” superstructure assigned to a periodic distorted Cu₂O(1 1 1)-like structure.     

Calibration and evaluation of optical systems for full-field strain measurement

The design and testing of a reference material for the calibration of optical systems for strain measurement is described, together with the design and testing of a standardized test material that allows the evaluation and assessment of fitness for purpose of the most sophisticated optical system for strain measurement. A classification system for the steps in the measurement process is also proposed and allows the development of a unified approach to diagnostic testing of components or sub-systems in an optical system for strain measurement based on any optical technique. The results described arise from a European study known as SPOTS whose objectives were to begin to fill the gap caused by a lack of standards.     

A New Approach to the {\ast} -Genvalue Equation

We show that the eigenvalues and eigenfunctions of the star-genvalue equation can be completely expressed in terms of the corresponding eigenvalue problem for the quantum Hamiltonian. Our methods make use of a Weyl-type representation of the star-product and of the properties of the cross-Wigner transform, which appears as an intertwining operator.     

Rheological properties of fresh and cryopreserved human arteries tested in vitro

Cryopreservation is widely used to preserve blood vessels for a while but is controversially suspected to affect the mechanical behavior of these allografts. The aim of this study was to determine whether differences in the three-dimensional mechanical behavior exist or not between fresh and cryopreserved arteries. Using a previously developed experimental system, in vitro inflation tests were performed on twenty segments of human fresh and cryopreserved arteries, in static conditions. Opening angles were also measured from images of rings in zero-stress state. The initial reference state was chosen as the unloaded state and tests were performed on specimens stretched at natural “in vivo” length. Mechanical measures calculated are “natural” (Hencky) strains (finite deformations), “true” (Cauchy) stresses in radial, circumferential, and longitudinal directions as well as strain energy per unit volume. Tangent moduli are derived from radial and circumferential stress-strain characteristics using non-linear curve fitting. Values of incremental and pressure-strain elastic parameters, wall stiffness, and compliance per unit length are also calculated. Results are presented in terms of characteristics of stresses and strains in the three directions, axial force, tangent moduli vs strains or stresses, and energy per unit volume, for both types of artery, with reference to transmural pressure. Detailed numerical results are given at mean transmural pressure or in the physiological range. Significant differences are indicated by statistic Student T-tests. Results obtained show that significant differences exist between rheological properties of fresh and cryopreserved segments of human artery. Strains, stresses, axial force, strain energy, and wall stiffness values highlight those differences whereas elastic parameters, compliance, and opening angle do not. The usefulness of some parameters to compare the mechanical behavior existing between fresh and cryopreserved arteries is therefore underlined. Received: 3 January 2000 Revision received: 12 April 2000 Accepted: 8 May 2000     

Energy levels of paramagnetic ions: Algebra. IV. The case of fN ions in cubical symmetry

The symmetry-adapted formalism and the weak-field model described in the first three papers of this series are applied to the case of a configuration nf^N in octahedral symmetry. In this case, the latter weakfield model is restricted to a 30-parameter model which accounts for isotropic and anisotropic Coulomb (repulsion) interactions, isotropic and anisotropic spin-orbit interactions, and crystal-field interactions. A comparison between this 30-parameter weak-field model and a 33-parameter strong-field model is established. Equivalence between these two models requires three constraint relations to be satisfied for some strong-field parameters. The three relations are examined on various viewpoints.     

White-light toxicity, resulting from systemically administered 5-aminolevulinic acid, under normal operating conditions

This study has investigated damage to the intraperitoneal organs of the rat after systemic (intraperitoneal and intravenous) administration of low doses of 5-aminolevulinic acid (ALA) and illumination with a standard white-light operating-room (o.r.) lamp. The study has been done within the framework of a larger study in which the possibility of using ALA for localization of small-volume macroscopically nonvisible peritoneal metastasis of ovarian tumors is being investigated. Fluorescence diagnostics are done in addition to the standard staging and localization procedures, either through a laparoscope or during laparotomy. In these circumstances, fluorescence diagnostics involve some risk of photosensitization of critical organs since a broad-band (o.r.) light source is used during the surgical procedures for illumination of the operating area. The drug dose and the time interval between administration of ALA and illumination are varied and normal tissues are examined both macroscopically and microscopically for damage. A relationship is demonstrated between the maximum tolerable dose (MTD) of ALA (defined as the dose that does not cause any tissue damage) and the time interval between administration and illumination. The white light that is used for illumination of the operating area is sufficient to induce damage to the peritoneal organs at relatively low ALA doses. The MDTs for 2, 6 and 16 h intervals are found to be respectively 1, 10 and 100 mg kg⁻¹. The results are similar for both intraperitoneal and intravenous administration.     

Batch processing with interval graph compatibilities between tasks

We analyze batch-scheduling problems that arise in connection with certain industrial applications. The models concern processing on a single max-batch machine with the additional feature that the tasks of the same batch have to be compatible. Compatibility is a symmetric binary relation—the compatible pairs are described with an undirected “compatibility graph”, which is often an interval graph according to some natural practical conditions that we present. We consider several models with varying batch capacities, processing times or compatibility graphs. We summarize known results, and present a min-max formula and polynomial time algorithms.