351 research outputs found
Attitude transfer assembly design for MAGSAT
A description is given of a design for an instrument system that will monitor the orientation of a boom-mounted vector magnetometer relative to the main spacecraft body. The attitude of the magnetometer is measured with respect to X and Z axes lateral to the boom length and also a twist axis around the boom center line. These measurements are made in a noncontact optical approach employing a three-axis autocollimator system mounted on the main body of the spacecraft with only passive elements (reflectors) located at the end of the 20-foot boom
Strain-Rate Frequency Superposition in Large-Amplitude Oscillatory Shear
In a recent work, Wyss, {\it et.al.} [Phys. Rev. Lett., {\bf 98}, 238303
(2007)] have noted a property of `soft solids' under oscillatory shear, the
so-called strain-rate frequency superposition (SRFS). We extend this study to
the case of soft solids under large-amplitude oscillatory shear (LAOS). We show
results from LAOS studies in a monodisperse hydrogel suspension, an aqueous
gel, and a biopolymer suspension, and show that constant strain-rate frequency
sweep measurements with soft solids can be superimposed onto master curves for
higher harmonic moduli, with the {\it same} shift factors as for the linear
viscoelastic moduli. We show that the behavior of higher harmonic moduli at low
frequencies in constant strain-rate frequency sweep measurements is similar to
that at large strain amplitudes in strain-amplitude sweep tests. We show
surface plots of the harmonic moduli and the energy dissipation rate per unit
volume in LAOS for soft solids, and show experimentally that the energy
dissipated per unit volume depends on the first harmonic loss modulus alone, in
both the linear and the nonlinear viscoelastic regime.Comment: 10 pages, 25 figures, accepted for publication in Physical Review E.
Incorporates referee comment
Research on physical and physiological aspects of visual optics in space flight
Physical and physiological aspects of visual optics in space fligh
Postmetamorphic ontogenetic allometry and the evolution of skull shape in Nest-building frogs Leptodactylus (Anura: Leptodactylidae)
Allometry constitutes an important source of morphological variation. However, its influence in head development in anurans has been poorly explored. By using geometric morphometrics followed by statistical and comparative methods we analyzed patterns of allometric change during cranial postmetamorphic ontogeny in species of Nest-building frogs Leptodactylus (Leptodactylidae). We found that the anuran skull is not a static structure, and allometry plays an important role in defining its shape in this group. Similar to other groups with biphasic life-cycle, and following a general trend in vertebrates, ontogenetic changes mostly involve rearrangement in rostral, otoccipital, and suspensorium regions. Ontogenetic transformations are paralleled by shape changes associated with evolutionary change in size, such that the skulls of species of different intrageneric groups are scaled to each other, and small and large species show patterns of paedomorphic/peramorphic features, respectively. Allometric trajectories producing those phenotypes are highly evolvable though, with shape change direction and magnitude varying widely among clades, and irrespective of changes in absolute body size. These results reinforce the importance of large-scale comparisons of growth patterns to understand the plasticity, evolution, and polarity of morphological changes in different clades.Fil: Duport Bru, Ana SofĂa. Consejo Nacional de Investigaciones CientĂficas y TĂ©cnicas. Centro CientĂfico TecnolĂłgico - Tucumán. Unidad Ejecutora Lillo; ArgentinaFil: Ponssa, MarĂa Laura. Consejo Nacional de Investigaciones CientĂficas y TĂ©cnicas. Centro CientĂfico TecnolĂłgico - Tucumán. Unidad Ejecutora Lillo; ArgentinaFil: Vera Candioti, MarĂa Florencia. Consejo Nacional de Investigaciones CientĂficas y TĂ©cnicas. Centro CientĂfico TecnolĂłgico - Tucumán. Unidad Ejecutora Lillo; Argentin
Fertility, Living Arrangements, Care and Mobility
There are four main interconnecting themes around which the contributions in this book are based. This introductory chapter aims to establish the broad context for the chapters that follow by discussing each of the themes. It does so by setting these themes within the overarching demographic challenge of the twenty-first century – demographic ageing. Each chapter is introduced in the context of the specific theme to which it primarily relates and there is a summary of the data sets used by the contributors to illustrate the wide range of cross-sectional and longitudinal data analysed
A Southern encounter: maternal body work and low-income mothers in South Africa
This paper explores the maternal body work practices of black low-income mothers from resource-poor urban spaces in South Africa. Using Southern Theory to open our analytical lens, we recognise that location has implications for how we understand the embodiment of gender and the lactating body in the global South. We argue that maternal body work, as one form of gendered embodiment, must be understood in a postcolonial landscape where histories of colonisation and indigenous gender orders continue to shape how women respond to work conditions and how they manage the competing demands of work and breastfeeding. Our analysis from 51 in-depth interviews conducted in Cape Town, demonstrates that maternal body work practices are interpreted through the entanglement of embodiment and work and non-work spaces. By emphasising contextual specificities relating to low-income worker’s living, working and family realities, we advance studies on maternal body work and employment from the global South
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