Diffusion Bonding Aeroengine Components

Abstract not available

On automorphisms of algebraic curves

An irreducible, algebraic curve $\mathcal X_g$ of genus $g\geq 2$ defined over an algebraically closed field $k$ of characteristic \mbox{char } \, k = p \geq 0, has finite automorphism group \mbox{Aut} (\mathcal X_g). In this paper we describe methods of determining the list of groups \mbox{Aut} (\mathcal X_g) for a fixed $g\geq 2$. Moreover, equations of the corresponding families of curves are given when possible

Suspending Lefschetz fibrations, with an application to Local Mirror Symmetry

We consider the suspension operation on Lefschetz fibrations, which takes p(x) to p(x)-y^2. This leaves the Fukaya category of the fibration invariant, and changes the category of the fibre (or more precisely, the subcategory consisting of a basis of vanishing cycles) in a specific way. As an application, we prove part of Homological Mirror Symmetry for the total spaces of canonical bundles over toric del Pezzo surfaces.Comment: v2: slightly expanded expositio

Million-atom molecular dynamics simulation by order-N electronic structure theory and parallel computation

Parallelism of tight-binding molecular dynamics simulations is presented by means of the order-N electronic structure theory with the Wannier states, recently developed (J. Phys. Soc. Jpn. 69,3773 (2000)). An application is tested for silicon nanocrystals of more than millions atoms with the transferable tight-binding Hamiltonian. The efficiency of parallelism is perfect, 98.8 %, and the method is the most suitable to parallel computation. The elapse time for a system of $2\times 10^6$ atoms is 3.0 minutes by a computer system of 64 processors of SGI Origin 3800. The calculated results are in good agreement with the results of the exact diagonalization, with an error of 2 % for the lattice constant and errors less than 10 % for elastic constants.Comment: 5 pages, 3 figure

Investigation of the sequential validity of quality improvement team self-assessments in a health facility HIV improvement collaborative in Tanzania

Background: Self-assessment is widely used in the health care improvement collaboratives quality improvement (QI) teams’ to assess their own performance. There is mixed evidence on the validity of this approach. This study investigated sequential validity of self-assessments in a QI HIV collaborative in Tanzania.Objectives: Define the separate self-assessment steps in QI process; determine if the validity of self-assessments improved over time; determine if validity improvement is the same for the different self-assessment activities and determine if validity is the same for the different facilities and type of care.Design: Prospective semi-quantitative study.Setting: The study was undertaken over 10 months in nine facilities in Mtwara region of Tanzania following appropriate approvals. Study did not interfere with routine services and processes of continuous quality improvement at the facilities.Subjects:Trained investigators retrieved information from records and the computers using data capture forms. Patients of service providers were not questioned or participate in the study.Conclusion:The validity of self-assessments in the HIV/ART/PMTCT Improvement Collaborative in Mtwara region of Tanzania improved as the collaborative matured. Data from computerised data bases unreliable, calling for more training in the use of computers. The weakness in communication should be addressed by collaborative designers and coaches

An Empirical Charge Transfer Potential with Correct Dissociation Limits

The empirical valence bond (EVB) method [J. Chem. Phys. 52, 1262 (1970)] has always embodied charge transfer processes. The mechanism of that behavior is examined here and recast for use as a new empirical potential energy surface for large-scale simulations. A two-state model is explored. The main features of the model are: (1) Explicit decomposition of the total system electron density is invoked; (2) The charge is defined through the density decomposition into constituent contributions; (3) The charge transfer behavior is controlled through the resonance energy matrix elements which cannot be ignored; and (4) A reference-state approach, similar in spirit to the EVB method, is used to define the resonance state energy contributions in terms of "knowable" quantities. With equal validity, the new potential energy can be expressed as a nonthermal ensemble average with a nonlinear but analytical charge dependence in the occupation number. Dissociation to neutral species for a gas-phase process is preserved. A variant of constrained search density functional theory is advocated as the preferred way to define an energy for a given charge.Comment: Submitted to J. Chem. Phys. 11/12/03. 14 pages, 8 figure

Occupation of wood warbler Phylloscopus sibilatrix nests by Myrmica and Lasius ants

Bird nests can provide habitats for various invertebrates, including ectoparasites, scavengers and predators. Records of ants associating with active bird nests mostly involve the insects searching for food, with some exceptional records of ants raising their broods (eggs, larvae or pupae) within songbird nests in tree cavities. We present data for a previously undocumented, but apparently regular, occurrence of ants and their broods within the active nests of a songbird, the wood warbler Phylloscopus sibilatrix (Bechstein, 1793), which builds domed nests on the ground in European forests. Systematic recording found ants, mostly Myrmica ruginodis Nylander, 1846, in 43% of 80 wood warbler nests in the primary forest of Białowieża National Park (Poland) during the springs of 2016-2017, including ant broods in 30%. Ad hoc records from this site in 2004-2015 found ants in a further 29% of 163 nests, including broods in 20%, indicating a regular association. However, examination of 37 nests from secondary forest in Switzerland and Great Britain founds ants in only 14%, and broods in just 5%. We discuss the potential drivers and mechanisms of the observed association between breeding wood warblers and ants, including the apparent difference in frequency between the primary and secondary forests

Computational modelling of particulate-reinforced materials up to high volume fractions: Linear elastic homogenisation

This work focuses on the analysis of the micro and macroscopic mechanical response of particle-reinforced composites. A particular attention is paid to the influence of two fundamental design parameters, i.e. the particles shape and their volume fraction (up to very high values ranging from 0 to almost 0.8), on the overall mechanical response of the structure as well as on the resulting elastic symmetry of the material. The strain energy-based homogenisation technique of periodic media is here applied to a 2D finite element model of a representative volume element of the composite. Different algorithms are developed to generate, with a good level of accuracy, the real microstructure of the composite material characterised by circular as well as polygonal particles. Moreover, for each studied configuration, a link between the geometrical parameters of the microstructure (particles shape, size, distribution, and volume fraction) and the size of the representative volume element is also provided in order to properly describe the constitutive behaviour of the composite at the macroscopic scale. The numerical results are compared with analytical models taken from the literature to prove on the one hand the limitations of the analytical approaches and on the other hand the effectiveness of the proposed numerical models

Results of two multi-chord stellar occultations by dwarf planet (1) Ceres

We report the results of two multi-chord stellar occultations by the dwarf planet (1) Ceres that were observed from Brazil on 2010 August 17, and from the USA on 2013 October 25. Four positive detections were obtained for the 2010 occultation, and nine for the 2013 occultation. Elliptical models were adjusted to the observed chords to obtain Ceres' size and shape. Two limb fitting solutions were studied for each event. The first one is a nominal solution with an indeterminate polar aspect angle. The second one was constrained by the pole coordinates as given by Drummond et al. Assuming a Maclaurin spheroid, we determine an equatorial diameter of 972 $\pm$ 6 km and an apparent oblateness of 0.08 $\pm$ 0.03 as our best solution. These results are compared to all available size and shape determinations for Ceres made so far, and shall be confirmed by the NASA's Dawn space mission.Comment: 9 pages, 6 figures. Accepted for publication in MNRA