Central-Peak-Soft-Mode, Coupling in Ferroelectric Gd\u3csub\u3e2\u3c/sub\u3e(MoO\u3csub\u3e4\u3c/sub\u3e)\u3csub\u3e3\u3c/sub\u3e

Transmission measurements on Gd2(MoO4)3 in the ( 5-50)-cm-1 region were performed with use of tunable backward-wave oscillator sources (5-30 cm\u3e-1) and a Fourier spectrometer (30-50 cm\u3e-1). The resulting dielectric spectra show an additional low-frequency dispersion which was fitted with a standard central-peak model. Its characteristic relaxation frequency is ~20 cm\u3e-1 and the coupling between the soft mode and central mode increases near the transition temperature. This model also accounts very well for the weak anomaly in the clamped permittivity Ec measured at 63 MHz. The same central mode was used to fit earlier Raman soft-mode spectra. All of these data were fitted with a three-coupled-mode model which revealed that the soft-mode spectrum consists of two strongly coupled bare modes: a higher-frequency mode which softens and carries the entire Raman strength and a lower-frequency mode which is hard (59 cm-1) and Raman inactive. Both of these modes are also coupled to the central mode and this coupling increases sharply near the transition. The relatively large width of the central mode indicates its intrinsic nature and suggests partial disorder near the transition

Drosophila TNF modulates tissue tension in the embryo to facilitate macrophage invasive migration

Migrating cells penetrate tissue barriers during development, inflammatory responses, and tumor metastasis. We study if migration in vivo in such three-dimensionally confined environments requires changes in the mechanical properties of the surrounding cells using embryonic Drosophila melanogaster hemocytes, also called macrophages, as a model. We find that macrophage invasion into the germband through transient separation of the apposing ectoderm and mesoderm requires cell deformations and reductions in apical tension in the ectoderm. Interestingly, the genetic pathway governing these mechanical shifts acts downstream of the only known tumor necrosis factor superfamily member in Drosophila, Eiger, and its receptor, Grindelwald. Eiger-Grindelwald signaling reduces levels of active Myosin in the germband ectodermal cortex through the localization of a Crumbs complex component, Patj (Pals-1-associated tight junction protein). We therefore elucidate a distinct molecular pathway that controls tissue tension and demonstrate the importance of such regulation for invasive migration in vivo

Whose Sense of Place? A Political Ecology of Amenity Development

Using a political ecology framework, this chapter examines the ways in which sense of place and amenity migration contribute to alternative residential development, which relies on uneven use of conservation subdivision features in the American West. Using case studies from Central Oregon, this chapter demonstrates how senses of place and developer decision-making are tied to wider political economic changes. It highlights the roles that amenity migrants and developers, two groups that are sometimes identical, play in landscape transformations that simultaneously draw on a particular sense of place and commodify landscapes in new ways

Adducins Regulate Remodeling of Apical Junctions in Human Epithelial Cells

This article identifies membrane skeleton proteins, adducins, as important regulators of epithelial cell–cell adhesions that promote assembly and antagonize stimulus-induced disassembly of adherens and tight junctions

Friction forces position the neural anlage

During embryonic development, mechanical forces are essential for cellular rearrangements driving tissue morphogenesis. Here, we show that in the early zebrafish embryo, friction forces are generated at the interface between anterior axial mesoderm (prechordal plate, ppl) progenitors migrating towards the animal pole and neurectoderm progenitors moving in the opposite direction towards the vegetal pole of the embryo. These friction forces lead to global rearrangement of cells within the neurectoderm and determine the position of the neural anlage. Using a combination of experiments and simulations, we show that this process depends on hydrodynamic coupling between neurectoderm and ppl as a result of E-cadherin-mediated adhesion between those tissues. Our data thus establish the emergence of friction forces at the interface between moving tissues as a critical force-generating process shaping the embryo