A Tangential Microslip Model for Circularly and Elliptically Loaded Structures

It is well known that the noise and vibration control of structures is a continuing challenge. With many structures this is commonly achieved through passive vibration damping; often using viscoelastic materials. Many structures however do not permit the use of such materials as their properties change over time, or when they are subjected to low and high temperature environments. For these structures, it is often that clamping or applied boundary conditions are critical for providing the energy dissipation through microslip. This makes it necessary to understand the level of damping that arises from the clamping zones. In general, the estimation of damping is complicated in that most structures are not uni-directionally loaded and can have a planar path of motion (e.g. gas turbine blades, circular motion valves). Although it is typical during experiments and simulations to reduce a structure into a single axis of excitation, this can often be an over simplification which does not describe the dynamics of the system; but should be included. This paper presents a biaxial planar motion tangential microslip model that accounts for the vibratory loads arising from circular and elliptical motion. This model vectorially decouples and reduces the planar vibratory circular and elliptical motion into two separate independent tangential microslip models. The models account for tip loading and for centroid loading within the microslip region of the clamping zone. Each analytical microslip model is presented and is compared to numerical simulations using finite elements. The analytical models are then coupled to demonstrate the net effect that various eccentricities have on the overall energy dissipation within the structure. The coupled models are then compared to numerical simulations using finite elements through ANSYS

Professionalism and the Millbank Tendency: The Political Sociology of New Labour's employees

This article analyses party employees, one of the most under-researched subjects in the study of British political parties. We draw on a blend of quantitative and qualitative data in order to shed light on the social and political profiles of Labour Party staff, and on the question of their professionalisation. The latter theme is developed through a model derived from the sociology of professions. While a relatively limited proportion of party employees conform to the pure ideal-type of professionalism, a considerably greater number manifest enough of the core characteristics of specialisation, commitment, mobility, autonomy and self-regulation to be reasonably described as 'professionals in pursuit of political outcomes'

Frost weathering of chalk

The processes and factors that determine the heave and fracture of frost-susceptible bedrock exposed to temperature cycling above and below 0°C are little known but important to understanding of rock deformation, weathering and ground conditions. To investigate the early stages of heave, settlement and fracture of intact chalk, physical modelling experiments were performed on blocks of Saint Cyr Tuffeau and Totternhoe Clunch. Unidirectional (downward) freezing simulated seasonally frozen bedrock in non-permafrost regions, and bidirectional (upward from permafrost and downward from the surface) simulated an active layer above permafrost. Heave and settlement of the top of the blocks were monitored in relation to rock temperature and unfrozen water content. Heave and settlement showed complex behavior that varied with moisture content, freezing regime and time. Progressive heave of wet chalk during thaw periods (simulated summers) is attributed to microcracking in near-surface permafrost. Macrocracking was favoured near the rock top during unidirectional freezing and near the permafrost table during bidirectional freezing, producing extensive fracture networks. Four processes, operating singly or in combination, account for the heave and settlement behavior: (1) thermal expansion and contraction in dry chalk; (2) volumetric expansion of freezing water, causing bursts of heave; (3) ice segregation, causing sustained heave and rock fracture; and (4) freeze‒thaw cycling, causing initial consolidation and settling of wet chalk during unidirectional freezing. The experimental data and field observations of chalk weathering profiles elucidate the nature and origin of chalk brecciation. Type 1 brecciation (angular or subangular rock fragments separated by unfilled fractures with matched sides) is attributed primarily to ice segregation. Type 2 brecciation (subangular to rounded lumps of rock—lithorelicts—set in a fine-grained matrix of the same, but softer and remoulded material) probably resulted from frost weathering and limited ground movement, particularly beneath the sides and bottoms of wet (now dry) valleys

The dissipative characteristics of oblate particles in granular dampers

In numerical models for granular dampers, particles are generally considered to be perfect spheres. However, in practical engineering applications these particles can slightly deviate from being true spheres. It has been observed experimentally that sphericity, which defines the proximity degree of a shape to a sphere, plays an important role in the amplitude dependent behaviour of granular dampers. This paper mainly examines the significance of the sphericity level for slightly oblate particles in a granular damper that are subjected to sinusoidal vibrations in the same direction as standard gravity. This investigation is carried out by evaluating the dissipated power from the granular medium by utilizing three-dimensional discrete element method simulations. Apart from the effect of amplitude of vibrations in the dissipated power, the relative contributions of frictional and inelastic collisional damping mechanisms in the overall power dissipation, are also investigated for varying sphericity levels of the oblate particles

Optical properties of tungsten thin films perforated with a bidimensional array of subwavelength holes

We present a theorical investigation of the optical transmission of a dielectric grating carved in a tungsten layer. For appropriate wavelengths tungsten shows indeed a dielectric behaviour. Our numerical simulations leads to theoretical results similar to those found with metallic systems studied in earlier works. The interpretation of our results rests on the idea that the transmission is correlated with the resonant response of eigenmodes coupled to evanescent diffraction orders.Comment: 4 pages, 3 figure

Expansions of algebras and superalgebras and some applications

After reviewing the three well-known methods to obtain Lie algebras and superalgebras from given ones, namely, contractions, deformations and extensions, we describe a fourth method recently introduced, the expansion of Lie (super)algebras. Expanded (super)algebras have, in general, larger dimensions than the original algebra, but also include the Inonu-Wigner and generalized IW contractions as a particular case. As an example of a physical application of expansions, we discuss the relation between the possible underlying gauge symmetry of eleven-dimensional supergravity and the superalgebra osp(1|32).Comment: Invited lecture delivered at the 'Deformations and Contractions in Mathematics and Physics Workshop', 15-21 January 2006, Mathematisches Forschungsinstitut Oberwolfach, German

4f spin density in the reentrant ferromagnet SmMn2Ge2

The spin contribution to the magnetic moment in SmMn2Ge2 has been measured by magnetic Compton scattering in both the low and high temperature ferromagnetic phases. At low temperature, the Sm site is shown to possess a large 4f spin moment of 3.4 +/- 0.1 Bohr magnetons, aligned antiparallel to the total magnetic moment. At high temperature, the data show conclusively that ordered magnetic moments are present on the samarium site.Comment: 5 pages, 2 figures, transferred from PRL to PRB (Rapid Comm.

Chitayat syndrome: hyperphalangism, characteristic facies, hallux valgus and bronchomalacia results from a recurrent c.266A>G p.(Tyr89Cys) variant in the ERF gene.

BACKGROUND: In 1993, Chitayat et al., reported a newborn with hyperphalangism, facial anomalies, and bronchomalacia. We identified three additional families with similar findings. Features include bilateral accessory phalanx resulting in shortened index fingers; hallux valgus; distinctive face; respiratory compromise. OBJECTIVES: To identify the genetic aetiology of Chitayat syndrome and identify a unifying cause for this specific form of hyperphalangism. METHODS: Through ongoing collaboration, we had collected patients with strikingly-similar phenotype. Trio-based exome sequencing was first performed in Patient 2 through Deciphering Developmental Disorders study. Proband-only exome sequencing had previously been independently performed in Patient 4. Following identification of a candidate gene variant in Patient 2, the same variant was subsequently confirmed from exome data in Patient 4. Sanger sequencing was used to validate this variant in Patients 1, 3; confirm paternal inheritance in Patient 5. RESULTS: A recurrent, novel variant NM_006494.2:c.266A>G p.(Tyr89Cys) in ERF was identified in five affected individuals: de novo (patient 1, 2 and 3) and inherited from an affected father (patient 4 and 5). p.Tyr89Cys is an aromatic polar neutral to polar neutral amino acid substitution, at a highly conserved position and lies within the functionally important ETS-domain of the protein. The recurrent ERF c.266A>C p.(Tyr89Cys) variant causes Chitayat syndrome. DISCUSSION: ERF variants have previously been associated with complex craniosynostosis. In contrast, none of the patients with the c.266A>G p.(Tyr89Cys) variant have craniosynostosis. CONCLUSIONS: We report the molecular aetiology of Chitayat syndrome and discuss potential mechanisms for this distinctive phenotype associated with the p.Tyr89Cys substitution in ERF