Program of analytical and experimental study of porous metal ionizers summary report

Cesium ion emission of porous tungsten material

Evidence for multiple structural genes for the γ chain of human fetal hemoglobin

A sequence with a specific residue at each position was proposed for the γ chain of human fetal hemoglobin by Schroeder et al. (1) after a study in which hemoglobin from a number of individual infants was used. We have now examined in part the fetal hemoglobin components of 17 additional infants and have observed that position 136 of the γ chain may be occupied not only by a glycyl residue, as previously reported, but also by an alanyl residue

Genotypic Effects on Condensed Tannins in the Leucaena Genus

One hundred and eighteen accessions of the Leucaena genus were assayed for extractable and bound condensed tannins (CT). Leucaena taxa varied from low or no CT (0-1%) to extremely high levels (\u3e15%). There was considerable intraspecific variation in CT within key taxa. The proportion of bound tannin decreased with increasing total CT content

Coulomb Blockade Regime of a Single-Wall Nanotube

A model of carbon nanotube at half filling is studied. The Coulomb interaction is assumed to be unscreened. It is shown that this allows to develop the adiabatic approximation which leads to considerable simplifications in calculations of the excitation spectrum. We give a detailed analysis of the spectrum and the phase diagram at half filling and discuss effects of small doping. At small doping several phases develop strong superconducting fluctuations corresponding to various types of pairing

Microwave Tube Research

Contains reports on four research projects

One-dimensional spin-liquid without magnon excitations

It is shown that a sufficiently strong four-spin interaction in the spin-1/2 spin ladder can cause dimerization. Such interaction can be generated either by phonons or (in the doped state) by the conventional Coulomb repulsion between the holes. The dimerized phases are thermodynamically undistinguishable from the Haldane phase, but have dramatically different correlation functions: the dynamical magnetic susceptibility, instead of displaying a sharp single magnon peak near $q = \pi$, shows only a two-particle threshold separated from the ground state by a gap.Comment: 9 pages, LaTex, to be published in Phys. Rev. Lett., vol. 78, May 199

The Tropical Grassland Society of Australia Incorporated

The Tropical Grassland Society of Australia was formed in 1962 and became incorporated in 1987 and has the following aims: To publicise information of interest to primary producers and scientists To improve the relevance of research and adoption of technology through the flow of ideas between scientists and producers To publicise the findings of Australian pasture research and development to overseas workers, and to draw on their experience for application in Australi

Superconductivity in a spin liquid - a one dimensional example

We study a one-dimensional model of interacting conduction electrons with a two-fold degenerate band away from half filling. The interaction includes an on-site Coulomb repulsion and Hund's rule coupling. We show that such one-dimensional system has a divergent Cooper pair susceptibility at T = 0, provided the Coulomb interaction $U$ between electrons on the same orbital and the modulus of the Hund's exchange integral $|J|$ are larger than the interorbital Coulomb interaction. It is remarkable that the superconductivity can be achieved for {\it any} sign of $J$. The opening of spectral gaps makes this state stable with respect to direct electron hopping between the orbitals. The scaling dimension of the superconducting order parameter is found to be between 1/4 (small $U$) and 1/2 (large $U$).Comment: 11 pages, Latex, no figure

An Effective Theory for Midgap States in Doped Spin Ladder and Spin-Peierls Systems: Liouville Quantum Mechanics

In gapped spin ladder and spin-Peierls systems the introduction of disorder, for example by doping, leads to the appearance of low energy midgap states. The fact that these strongly correlated systems can be mapped onto one dimensional noninteracting fermions provides a rare opportunity to explore systems which have both strong interactions and disorder. In this paper we show that the statistics of the zero energy midgap wave functions in these models can be effectively described by Liouville Quantum Mechanics. This enables us to calculate the disorder averaged N-point correlation functions of these states (the explicit calculation is performed for N=2,3). We find that whilst these midgap states are typically weakly correlated, their disorder averaged correlation are power law. This discrepancy arises because the correlations are not self-averaging and averages of the wave functions are dominated by anomalously strongly correlated configurations.Comment: 13 page latex fil

Leucaena in Northern Australia: A Forage Tree Legume Success Story

Leucaena leucocephala (leucaena) is a long-lived, perennial forage tree legume of very high nutritive value for ruminant production. In northern Australia, leucaena is direct seeded into hedgerows 5-10m apart, with grass species such as buffel grass (Cenchrus ciliaris) planted in the inter-row to form a highly productive and sustainable grass-legume pasture that cattle graze directly. It generally is grown on deep, fertile soils in sub-humid environments with average rainfall of 600-800mm/year. Steer gains of 275-300kg/head per year are achieved, with short-term daily gains over the main growing season \u3e 1kg/head. Being very deep-rooted, leucaena exploits moisture beyond the reach of grasses and remains productive well into the dry season. Once established, leucaena-grass pastures remain productive for \u3e 40 years