Experimental characterization of deployable trusses and joints

The structural dynamic properties of trusses are strongly affected by the characteristics of joints connecting the individual beam elements. Joints are particularly significant in that they are often the source of nonlinearities and energy dissipation. While the joints themselves may be physically simple, direct measurement is often necessary to obtain a mathematical description suitable for inclusion in a system model. Force state mapping is a flexible, practical test method for obtaining such a description, particularly when significant nonlinear effects are present. It involves measurement of the relationship, nonlinear or linear, between force transmitted through a joint and the relative displacement and velocity across it. An apparatus and procedure for force state mapping are described. Results are presented from tests of joints used in a lightweight, composite, deployable truss built by the Boeing Aerospace Company. The results from the joint tests are used to develop a model of a full 4-bay truss segment. The truss segment was statically and dynamically tested. The results of the truss tests are presented and compared with the analytical predictions from the model

Curvaton Scenario with Affleck-Dine Baryogenesis

We discuss the curvaton scenario with the Affleck-Dine baryogenesis. In this scenario, non-vanishing baryonic entropy fluctuation may be generated even without primordial fluctuation of the Affleck-Dine field. Too large entropy fluctuation is inconsistent with the observations and hence constraints on the curvaton scenario with the Affleck-Dine baryogenesis are obtained. We calculate the baryonic entropy fluctuation (as well as other cosmological density fluctuations) in this case and derive constraints. Implications to some of the models of the curvaton are also discussed.Comment: 16 pages,2 figure

Clinical biological and genetic heterogeneity of the inborn errors of pulmonary surfactant metabolism

Pulmonary surfactant is a multimolecular complex located at the air-water interface within the alveolus to which a range of physical (surface-active properties) and immune functions has been assigned. This complex consists of a surface-active lipid layer (consisting mainly of phospholipids), and of an aqueous subphase. From discrete surfactant sub-fractions one can isolate strongly hydrophobic surf acta nt proteins B (SP-B) and C (SP-C) as well as collectins SP-A and SP-D, which were shown to have specific structural, metabolic, or immune properties. Inborn or acquired abnormalities of the surfactant, qualitative or quantitative in nature, account for a number of human diseases. Beside hyaline membrane disease of the preterm neonate, a cluster of hereditary or acquired lung diseases has been characterized by periodic acid-Schiff-positive material filling the alveoli. From this heterogeneous nosologic group, at least two discrete entities presently emerge. The first is the SP-B deficiency, in which an essentially proteinaceous material is stored within the alveoli, and which represents an autosomal recessive Mendelian entity linked to the SFTPB gene (MIM 1786640). The disease usually generally entails neonatal respiratory distress with rapid fatal outcome, although partial or transient deficiencies have also been observed. The second is alveolar proteinosis, characterized by the storage of a mixed protein and lipid material, which constitutes a relatively heterogeneous clinical and biological syndrome, especially with regard to age at onset (from the neonate through to adulthood) as well as the severity of associated signs. Murine models, with a targeted mutation of the gene encoding granulocyte macrophage colony-stimulating factor (GM-CSF) (Csfgm) or the beta subunit of its receptor (II3rb1) support the hypothesis of an abnormality of surfactant turnover in which the alveolar macrophage is a key player. Apart from SP-B deficiency, in which a near-consensus diagnostic chart can be designed, the ascertainment of other abnormalities of surfactant metabolism is not straightforward. The disentanglement of this disease cluster is however essential to propose specific therapeutic procedures: repeated broncho-alveolar ravages, GM-CSF replacement, bone marrow grafting or lung transplantation

Electronic structure of periodic curved surfaces -- topological band structure

Electronic band structure for electrons bound on periodic minimal surfaces is differential-geometrically formulated and numerically calculated. We focus on minimal surfaces because they are not only mathematically elegant (with the surface characterized completely in terms of "navels") but represent the topology of real systems such as zeolites and negative-curvature fullerene. The band structure turns out to be primarily determined by the topology of the surface, i.e., how the wavefunction interferes on a multiply-connected surface, so that the bands are little affected by the way in which we confine the electrons on the surface (thin-slab limit or zero thickness from the outset). Another curiosity is that different minimal surfaces connected by the Bonnet transformation (such as Schwarz's P- and D-surfaces) possess one-to-one correspondence in their band energies at Brillouin zone boundaries.Comment: 6 pages, 8 figures, eps files will be sent on request to [email protected]

Band structures of P-, D-, and G-surfaces

We present a theoretical study on the band structures of the electron constrained to move along triply-periodic minimal surfaces. Three well known surfaces connected via Bonnet transformations, namely P-, D-, and G-surfaces, are considered. The six-dimensional algebra of the Bonnet transformations [C. Oguey and J.-F. Sadoc, J. Phys. I France 3, 839 (1993)] is used to prove that the eigenstates for these surfaces are interrelated at a set of special points in the Brillouin zones. The global connectivity of the band structures is, however, different due to the topological differences of the surfaces. A numerical investigation of the band structures as well as a detailed analysis on their symmetry properties is presented. It is shown that the presence of nodal lines are closely related to the symmetry properties. The present study will provide a basis for understanding further the connection between the topology and the band structures.Comment: 21 pages, 8 figures, 3 tables, submitted to Phys. Rev.

Hanging in there: Prenatal origins of antigravity homeostasis in humans

All life on Earth must find a way to manage the continuous perturbation of gravity. From birth, and even before, humans exhibit effortful antigravity work to enact bodily, postural and behavioural form despite gravity. Indeed, observable antigravity behaviour is a standard diagnostic indicator of neonatal sensorimotor health. Antigravity behaviour has been investigated extensively in its biomechanical details. Yet its motivational structure has not been a focus of research. What drives the human body to expend energy on this effortful behaviour? It is widely understood that thermic homeostasis in humans is organised around conserving core body temperature at a set-point of 36.5-37.5oC. There is currently no equivalent concept of a general homeostatic set-point driving antigravity effort. In this theoretical paper, we aim to establish such a concept. We make the case that the core developmental set-point for human antigravity homeostasis is neutral buoyancy (gravity and buoyant force are balanced), which is afforded to the foetus by its approximately equi-dense amniotic fluid medium in utero. We argue that postnatally, the general task of human antigravity balance is to emulate the conditions of neutral buoyancy, based upon prenatal experience thereof. Our aim in this paper is to sketch a high-level outline of a novel characterisation of antigravity balance as conservative homeostasis, and lay out some implications and predictions of this model, with the intention of spurring wider research and discussion on this hitherto little explored topic. Keywords: antigravity, posture, homeostasis, prenatal, buoyancy, density, fetus, foetusComment: 19 pages (including references) Zero figure

Search for Short-Lived Neutron-Rich Nuclei Produced by Charged-Particle- Induced Fission of 238U with IGISOL

開始ページ、終了ページ: 冊子体のページ付

IVth symposium on ‘intracellular protein catabolism’ Reinhardsbrunn Castle, Thuringia, DDR, 21–27 May 1981

While index-based microinsurance has attracted considerable attention, uptake rates have been weak in many low-income countries. We explore the purchase patterns of index-based livestock insurance in southern Ethiopia, focusing on the role of accurate product comprehension and price. We find that randomly distributed learning kits improve subjects’ knowledge of the products; however, we do not find strong evidence that the improved knowledge per se causes greater insurance uptake. We also find that reduced price due to randomly distributed discount coupons has an immediate, positive impact on uptake, without dampening subsequent period demand due to reference-dependence associated with price anchoring effects