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

Biomechanical Analysis of Body Movement During Skiing Over Bumps

Maintenance of balance of the skier's body is one of the most important and basic techniques in skiing on slopes of various conditions. However, skiers, especially beginners are likely to lose their balance on an uneven terrain with dips and swells. In order to keep his balance during skiing on an uneven terrain, it seems to be important for a skier to avoid receiving impulse from the snow surface. Some investigations have been conducted about maintenance of balance of body during skiing over artificially constructed bumps by means of electromyography (Miyashita and Sakurai, 1979), electrogoniometry (Iizuka and Miyashita, 1979) and cinematography (Miyashita and Sakurai, 1979, Iizuka and Miyashita, 1979, Sodeyama et al., 1979 and Ikegami et al. 1985). However, there is no research to try to measure force or acceleration acting on the skier's body during running over bumps. Therefore the purpose of this study is to measure force acting on skier's body by analyzing the movement of skier's body mechanically as well as kinematically, and to find out essential motions to maintain the balance of skier's body against rapid change of force acting from snow surface while skiing over bumps on a straight downhill run

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.

The Changes in Mechanical Energy During the Giant Swing Backward on the Horizontal Bar

In the giant swing backward, mechanical energy of the whole body is decreased due to friction between gymnast hands and the bar, and to air resistance. To complete the rotation, the gymnast has to do muscular work to offset these energy losses. Total mechanical energy changes with the relationship between energy loss and muscular work. Therefore, for biomechanical investigation of the giant swing backward, it is important to have an accurate measure of the mechanical energy changes of the whole body. Although there are many studies of energetics of the human fundamental movement such as walking and running, the mechanical energy changes of the whole body have not been reported during the giant swing backward on the horizontal bar. The purpose of this study is to report the mechanical energy changes of the whole body, and to identify the muscular work donc by the gymnast during the giant swing backward on the horizontal bar

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

Open problems in artificial life

This article lists fourteen open problems in artificial life, each of which is a grand challenge requiring a major advance on a fundamental issue for its solution. Each problem is briefly explained, and, where deemed helpful, some promising paths to its solution are indicated

Reference gene validation for gene expression studies using quantitative RT-PCR during berry development of ‘Aki Queen’ grapes

In order to understand the gene regulation during berry development and examine the effect of abscisic acid (ABA) on gene expression related to berry maturation, we evaluated the validity of four housekeeping genes, elongation factor 1-α (EF1-α), glyceraldehyde-3-phosphate dehydrogenase (GAPDH), ubiquitin-conjugating enzyme (UBC), and 60S ribosomal protein L40-1 (VvUbiquitin1), as references by using 'Aki Queen' grapes with and without ABA treatment. The main contribution of this study is that a gene expression analysis using GAPDH as a reference gene will help to elucidate the berry development process and the physiological effects of ABA on berry maturation of 'Aki Queen' grapes

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]

Caenorhabditis elegans chromosome arms are anchored to the nuclear membrane via discontinuous association with LEM-2

Abstract Background Although Caenorhabditis elegans was the first multicellular organism with a completely sequenced genome, how this genome is arranged within the nucleus is not known. Results We determined the genomic regions associated with the nuclear transmembrane protein LEM-2 in mixed-stage C. elegans embryos via chromatin immunoprecipitation. Large regions of several megabases on the arms of each autosome were associated with LEM-2. The center of each autosome was mostly free of such interactions, suggesting that they are largely looped out from the nuclear membrane. Only the left end of the X chromosome was associated with the nuclear membrane. At a finer scale, the large membrane-associated domains consisted of smaller subdomains of LEM-2 associations. These subdomains were characterized by high repeat density, low gene density, high levels of H3K27 trimethylation, and silent genes. The subdomains were punctuated by gaps harboring highly active genes. A chromosome arm translocated to a chromosome center retained its association with LEM-2, although there was a slight decrease in association near the fusion point. Conclusions Local DNA or chromatin properties are the main determinant of interaction with the nuclear membrane, with position along the chromosome making a minor contribution. Genes in small gaps between LEM-2 associated regions tend to be highly expressed, suggesting that these small gaps are especially amenable to highly efficient transcription. Although our data are derived from an amalgamation of cell types in mixed-stage embryos, the results suggest a model for the spatial arrangement of C. elegans chromosomes within the nucleus