Direct observation of twist mode in electroconvection in I52

I report on the direct observation of a uniform twist mode of the director field in electroconvection in I52. Recent theoretical work suggests that such a uniform twist mode of the director field is responsible for a number of secondary bifurcations in both electroconvection and thermal convection in nematics. I show here evidence that the proposed mechanisms are consistent with being the source of the previously reported SO2 state of electroconvection in I52. The same mechanisms also contribute to a tertiary Hopf bifurcation that I observe in electroconvection in I52. There are quantitative differences between the experiment and calculations that only include the twist mode. These differences suggest that a complete description must include effects described by the weak-electrolyte model of electroconvection

Does STAT5a Have an Effect on BMAL1 Levels in Mammary Epithelial Cells?

The mammary gland is a very important organ for reproduction in mammals because it produces milk which serves as the primary source of nutrients for newly-born offspring. Previous studies suggest that its development is regulated by circadian clocks, biochemical oscillators that generate circadian rhythms (the body’s internal clock). The circadian system plays a major role in homeostasis, coordinating the body’s internal physiology and synchronizing it with the external environment. Our lab showed that levels of the BMAL1 protein, a core clock component, increased in the mammary gland at the onset of lactation. Treatment of mammary epithelial cells (HC11) with the hormone prolactin significantly increased BMAL1 levels. We hypothesize that the secretion of prolactin during lactogenesis induces expression of BMAL1 in the mouse mammary gland through the STAT5a signaling pathway. The objective of the project was to determine the effect of different amounts of STAT5a protein on BMAL1 levels with and without prolactin treatment. For this experiment, western blot analysis was used to measure STAT5a and BMAL1 levels in wild type HC11 cells and in HC11 cell lines that were genetically modified to: 1) express very high levels of STAT5a (STAT5a-OE), 2) express a mutant form of STAT5a that is inactive (STAT5a-dnl), and 3) delete the BMAL1 gene (BMAL1 KO). Our first round of analysis showed that overexpressing STAT5a increased BMAL1 protein levels, especially in cells differentiated by prolactin. Results from this experiment would allow us to better understand the relationship between mammary gland development and the circadian system

Understanding the relationships between the physical environment and physical activity in older adults: a systematic review of qualitative studies

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Repair of a Reinforced Earth Wall

The facing of a Reinforced Earth retaining wall, built at an altitude of 1200 m, was damaged during the winter 1981. The repair was achieved quickly and under traffic. The instrumentation carried out on the repairs and the tests run on the backfill material have revealed the action of the frost and its increase in the fortuitous presence of water

Tuning gaps and phases of a two-subband system in a quantizing magnetic field

In this work we study the properties of a two-subband quasi-two-dimensional electron system in a strong magnetic field when the electron filling factor is equal to four. When the cyclotron energy is close to the intersubband splitting the system can be mapped onto a four-level electron system with an effective filling factor of two. The ground state is either a ferromagnetic state or a spin-singlet state, depending on the values of the inter-level splitting and Zeeman energy. The boundaries between these phases are strongly influenced by the inter-electron interaction. A significant exchange-mediated enhancement of the excitation gap results in the suppression of the electron-phonon interaction. The rate of absorption of non-equilibrium phonons is calculated as a function of Zeeman energy and inter-subband splitting. The phonon absorption rate has two peaks as a function of intersubband splitting and has a step-like structure as a function of Zeeman energy

Quasiparticle properties of a coupled quantum wire electron-phonon system

We study leading-order many-body effects of longitudinal optical (LO) phonons on electronic properties of one-dimensional quantum wire systems. We calculate the quasiparticle properties of a weakly polar one dimensional electron gas in the presence of both electron-phonon and electron-electron interactions. The leading-order dynamical screening approximation (GW approximation) is used to obtain the electron self-energy, the quasiparticle spectral function, and the quasiparticle damping rate in our calculation by treating electrons and phonons on an equal footing. Our theory includes effects (within the random phase approximation) of Fermi statistics, Landau damping, plasmon-phonon mode coupling, phonon renormalization, dynamical screening, and impurity scattering. In general, electron-electron and electron-phonon many-body renormalization effects are found to be nonmultiplicative and nonadditive in our theoretical results for quasiparticle properties.Comment: 21 pages, Revtex, 12 figures enclose

Three-dimensional pattern formation, multiple homogeneous soft modes, and nonlinear dielectric electroconvection

Patterns forming spontaneously in extended, three-dimensional, dissipative systems are likely to excite several homogeneous soft modes ($\approx$ hydrodynamic modes) of the underlying physical system, much more than quasi one- and two-dimensional patterns are. The reason is the lack of damping boundaries. This paper compares two analytic techniques to derive the patten dynamics from hydrodynamics, which are usually equivalent but lead to different results when applied to multiple homogeneous soft modes. Dielectric electroconvection in nematic liquid crystals is introduced as a model for three-dimensional pattern formation. The 3D pattern dynamics including soft modes are derived. For slabs of large but finite thickness the description is reduced further to a two-dimensional one. It is argued that the range of validity of 2D descriptions is limited to a very small region above threshold. The transition from 2D to 3D pattern dynamics is discussed. Experimentally testable predictions for the stable range of ideal patterns and the electric Nusselt numbers are made. For most results analytic approximations in terms of material parameters are given.Comment: 29 pages, 2 figure