Juncture stress fields in multicellular shell structures. Vol. IX - Summary of results and recommendations Final report

Juncture stress fields in multicellular shell structures - bending and bucking analyse

Juncture stress fields in multicellular shell structures. Volume III - Stresses and deformations on fixed-edge segmental conical shells Final report

Equations for thin elastic conical shells and digital program for analysis of stress and deformation on fixed edge segmental conical shells - solution by finite difference techniqu

Juncture stress fields in multicellular shell structures. Volume IV - Stresses and deformations of fixed-edge segmental spherical shells Final report

Equations for thin elastic spherical shells and digital program for analysis of stresses and deformation of fixed edge segmental spherical shells - solution by finite difference techniqu

Investigation of juncture stress fields in multicellular shell structures

Discontinuity stress fields in thin elastic multicellular shell structures subject to inertial, pressure, and thermal loadin

Observation of pinning mode in Wigner solid of 1/3 fractional quantum Hall excitations

We report the observation of a resonance in the microwave spectra of the real diagonal conductivities of a two-dimensional electron system within a range of ~ +- .0.015 $from filling factor$\nu=1/3$. The resonance is remarkably similar to resonances previously observed near integer$\nu$, and is interpreted as the collective pinning mode of a disorder-pinned Wigner solid phase of$e/3$-charged carriers .Comment: version with edits for clarity, improved Figure 3 and added referenc

Thermodynamic Study of Excitations in a 3D Spin Liquid

In order to characterize thermal excitations in a frustrated spin liquid, we have examined the magnetothermodynamics of a model geometrically frustrated magnet. Our data demonstrate a crossover in the nature of the spin excitations between the spin liquid phase and the high-temperature paramagnetic state. The temperature dependence of both the specific heat and magnetization in the spin liquid phase can be fit within a simple model which assumes that the spin excitations have a gapped quadratic dispersion relation.Comment: 5 figure

Evidence for Two Different Solid Phases of Two Dimensional Electrons in High Magnetic Fields

We have performed RF spectroscopy on very high quality two dimensional electron systems in the high magnetic field insulating phase, usually associated with a Wigner solid (WS) pinned by disorder. We have found two different resonances in the frequency dependent real diagonal conductivity spectrum and we interpret them as coming from \textit{two} different pinned solid phases (labeled as "WS-A" and "WS-B"). The resonance of WS-A is observable for Landau level filling $\nu$$<$2/9 (but absent around the $\nu$=1/5 fractional quantum Hall effect (FQHE)); it then \textit{crosses over} for $\nu$$<$0.18 to the different WS-B resonance which dominates the spectrum at $\nu$$<$0.125. Moreover, WS-A resonance is found to show dispersion with respect to the size of transmission line, indicating that WS-A has a large correlation length (exceeding $\sim$100 $\mu$m); in contrast no such behavior is found for WS-B. We suggest that quantum correlations such as those responsible for FQHE may play an important role in giving rise to such different solids.Comment: 4 pages, 3 figure

Transverse optical plasmons in layered superconductors

We discuss the possible existance of transverse optical plasma modes in superlattices consisting of Josephson coupled superconducting layers. These modes appear as resonances in the current-current correlation function, as opposed to the usual plasmons which are poles in the density-density channel. We consider both bilayer superlattices, and single layer lattices with a spread of interlayer Josephson couplings. We show that our model is in quantitative agreement with the recent experimental observation by a number of groups of a peak at the Josephson plasma frequency in the optical conductivity of La$_{1.85}$Sr$_{0.15}$CuO$_4$Comment: Proceedings of LT21, in press, 4 pages, Latex with LTpaper.sty and epsfig.sty, 2 postscript figure

A different view of the quantum Hall plateau-to-plateau transitions

We demonstrate experimentally that the transitions between adjacent integer quantum Hall (QH) states are equivalent to a QH-to-insulator transition occurring in the top Landau level, in the presence of an inert background of the other completely filled Landau levels, each contributing a single unit of quantum conductance, $e^{2}/h$, to the total Hall conductance of the system.Comment: 10 pages, 4 figures, Revtex 3.