The Positions of Hydrogen Atoms in (NH4)2CuCl4 · 2 H2O by Neutron Diffraction

The structure of (NH4)2 CuCl4 · 2 H2O has been determined from two-dimensional neutron data. The R index is 5.6% when unobserved reflections are omitted. Two water oxygen atoms with t he Cu-O distance of 1.98 A and two chlorine atoms with the Cu-Cl distance of 2.30 A form a planar Cu(OH2 ) 2 Cl 2 grouping. Each copper atom also forms two long Cu-Cl bonds of 3.03 A with the other two chlorine atoms and so completes its distorted octahedral configuration. The structure consists of distorted 1[Cu(OH2l2Ch]Ch octahedra connected by hydrogen bonds and NH4 tetrahedra which occupy holes between the three-dimensional network of octahedra

The Positions of Hydrogen Atoms in (NH4)2CuCl4 · 2 H2O by Neutron Diffraction

The structure of (NH4)2 CuCl4 · 2 H2O has been determined from two-dimensional neutron data. The R index is 5.6% when unobserved reflections are omitted. Two water oxygen atoms with t he Cu-O distance of 1.98 A and two chlorine atoms with the Cu-Cl distance of 2.30 A form a planar Cu(OH2 ) 2 Cl 2 grouping. Each copper atom also forms two long Cu-Cl bonds of 3.03 A with the other two chlorine atoms and so completes its distorted octahedral configuration. The structure consists of distorted 1[Cu(OH2l2Ch]Ch octahedra connected by hydrogen bonds and NH4 tetrahedra which occupy holes between the three-dimensional network of octahedra

A Fermi Fluid Description of the Half-Filled Landau Level

We present a many-body approach to calculate the ground state properties of a system of electrons in a half-filled Landau level. Our starting point is a simplified version of the recently proposed trial wave function where one includes the antisymmetrization operator to the bosonic Laughlin state. Using the classical plasma analogy, we calculate the pair-correlation function, the static structure function and the ground state energy in the thermodynamic limit. These results are in good agreement with the expected behavior at $\nu=\frac12$.Comment: 4 pages, REVTEX, and 4 .ps file

Diffusion Thermopower at Even Denominator Fractions

We compute the electron diffusion thermopower at compressible Quantum Hall states corresponding to even denominator fractions in the framework of the composite fermion approach. It is shown that the deviation from the linear low temperature behavior of the termopower is dominated by the logarithmic temperature corrections to the conductivity and not to the thermoelectric coefficient, although such terms are present in both quantities. The enhanced magnitude of this effect compared to the zero field case may allow its observation with the existing experimental techniques.Comment: Latex, 12 pages, Nordita repor

Experimental studies of the fractional quantum Hall effect in the first excited Landau level

We present a spectrum of experimental data on the fractional quantum Hall effect (FQHE) states in the first excited Landau level, obtained in an ultrahigh mobility two-dimensional electron system (2DES) and at very low temperatures and report the following results: For the even-denominator FQHE states, the sample dependence of the nu=5/2 state clearly shows that disorder plays an important role in determining the energy gap at nu=5/2. For the developing nu=19/8 FQHE state the temperature dependence of the Rxx minimum implies an energy gap of ~5mK.The energy gaps of the odd-denominator FQHE states at nu=7/3 and 8/3 also increase with decreasing disorder, similar to the gap at 5/2 state. Unexpectedly and contrary to earlier data on lower mobility samples, in this ultra-high quality specimen, the nu=13/5 state is missing, while its particle-hole conjugate state, the nu=12/5 state, is a fully developed FQHE state. We speculate that this disappearance might indicate a spin polarization of the nu=13/5 state. Finally, the temperature dependence is studied for the two-reentrant integer quantum Hall states around nu=5/2 and is found to show a very narrow temperature range for the transition from quantized to classical value.Comment: to be publishe

Exploration Strategies for Discovery of Interactivity in Visualizations

We investigate how people discover the functionality of an interactive visualization that was designed for the general public. While interactive visualizations are increasingly available for public use, we still know little about how the general public discovers what they can do with these visualizations and what interactions are available. Developing a better understanding of this discovery process can help inform the design of visualizations for the general public, which in turn can help make data more accessible. To unpack this problem, we conducted a lab study in which participants were free to use their own methods to discover the functionality of a connected set of interactive visualizations of public energy data. We collected eye movement data and interaction logs as well as video and audio recordings. By analyzing this combined data, we extract exploration strategies that the participants employed to discover the functionality in these interactive visualizations. These exploration strategies illuminate possible design directions for improving the discoverability of a visualization's functionality

Density Induced Interchange of Anisotropy Axes at Half-Filled High Landau Levels

We observe density induced 90$^{\circ}$ rotations of the anisotropy axes in transport measurements at half-filled high Landau levels in the two dimensional electron system, where stripe states are proposed ($\nu$=9/2, 11/2, etc). Using a field effect transistor, we find the transition density to be $2.9\times10^{11}$cm$^{-2}$ at $\nu$=9/2. Hysteresis is observed in the vicinity of the transition. We construct a phase boundary in the filling factor-magnetic field plane in the regime $4.4<\nu<4.6$. An in-plane magnetic field applied along either anisotropy axis always stabilizes the low density orientation of the stripes.Comment: 1 revtex file, 3 eps figure

Food, Nutrition, Physical Activity, and the Prevention of Cancer: a Global Perspective

This Report has a number of inter-related general purposes. One is to explore the extent to which food, nutrition, physical activity, and body composition modify the risk of cancer, and to specify which factors are most important. To the extent that environmental factors such as food, nutrition, and physical activity influence the risk of cancer, it is a preventable disease. The Report specifies recommendations based on solid evidence which, when followed, will be expected to reduce the incidence of cancer

Principles behind evaluations of national food and beverage taxes and other regulatory efforts

Non-PRIFPRI3; ISIPHN