Oscillating chiral currents in nanotubes: a route to nanoscale magnetic test tubes

With a view to optimising the design of carbon-nanotube (CNT) windmills and to maximising the internal magnetic field generated by chiral currents, we present analytical results for the group velocity components of an electron flux through chiral carbon nanotubes. Chiral currents are shown to exhibit a rich behaviour and can even change sign and oscillate as the energy of the electrons is increased. We find that the transverse velocity and associated angular momentum of electrons is a maximum for non-metallic CNTs with a chiral angle of 18$^o$. Such CNTs are therefore the optimal choice for CNT windmills and also generate the largest internal magnetic field for a given longitudinal current. For a longitudinal current of order $10^{-4}$ amps, this field can be of order $10^{-1}$Teslas, which is sufficient to produce interesting spintronic effects and a significant contribution to the self inductance.Comment: 4 pages, 1 figur

Drive mechanism for production of simulated human breath

Simulated breath drive mechanism was developed as subsystem to breathing metabolic simulator. Mechanism reproduces complete range of human breath rate, breath depth, and breath waveform, as well as independently controlled functional residual capacity. Mechanism was found capable of simulating various individual human breathing characteristics without any changes of parts

Suppression of Giant Magnetoresistance by a superconducting contact

We predict that current perpendicular to the plane (CPP) giant magnetoresistance (GMR) in a phase-coherent magnetic multilayer is suppressed when one of the contacts is superconducting. This is a consequence of a superconductivity-induced magneto-resistive (SMR) effect, whereby the conductance of the ferromagnetically aligned state is drastically reduced by superconductivity. To demonstrate this effect, we compute the GMR ratio of clean (Cu/Co)_nCu and (Cu/Co)_nPb multilayers, described by an ab-initio spd tight binding Hamiltonian. By analyzing a simpler model with two orbitals per site, we also show that the suppression survives in the presence of elastic scattering by impurities.Comment: 5 pages, 4 figures. Submitted to PR

Giant Backscattering Peak in Angle-Resolved Andreev Reflection

It is shown analytically and by numerical simulation that the angular distribution of Andreev reflection by a disordered normal-metal -- superconductor junction has a narrow peak at the angle of incidence. The peak is higher than the well-known coherent backscattering peak in the normal state, by a large factor G/G_0 (where G is the conductance of the junction and G_0=2e^2/h). The enhanced backscattering can be detected by means of ballistic point contacts.Comment: Instituut-Lorentz, Leiden, The Netherlands, 4 pages, REVTeX-3.0, 3 figure

On the Inheritance of Resistance to Fowl Typhoid in Chickens

Studies at the Iowa Experiment Station during 1927 and 1928 indicate very clearly that selection is effective in increasing resistance to this disease

Semiclassical theory in Andreev billiards: beyond the diagonal approximation

Recently semiclassical approximations have been successfully applied to study the effect of a superconducting lead on the density of states and conductance in ballistic billiards. However, the summation over classical trajectories involved in such theories was carried out using the intuitive picture of Andreev reflection rather than the semiclassical reasoning. We propose a method to calculate the semiclassical sums which allows us to go beyond the diagonal approximation in these problems. In particular, we address the question of whether the off-diagonal corrections could explain the gap in the density of states of a chaotic Andreev billiard.Comment: 11 page

Random Scattering Matrices and the Circuit Theory of Andreev Conductances

The conductance of a normal-metal mesoscopic system in proximity to superconducting electrode(s) is calculated. The normal-metal part may have a general geometry, and is described as a ``circuit'' with ``leads'' and ``junctions''. The junctions are each ascribed a scattering matrix which is averaged over the circular orthogonal ensemble, using recently-developed techniques. The results for the electrical conductance reproduce and extend Nazarov's circuit theory, thus bridging between the scattering and the bulk approaches. The method is also applied to the heat conductance.Comment: 12 pages, RevTeX, including 2 figures with eps

Dermatofibroma: a curious tumor.

A tumor, such as a dermatofibroma, causes consternation among many patients, but it rarely creates problems on its own. Also called a histiocytoma, it remains one of the most common mesenchymal growths. Its etiology is unknown with the previous theory that it is a dermal response to injury, such as an insect bite, being challenged. As much as patients like to blame spiders or other arthropods for traumatizing an arm or leg, no definitive explanation is available for its etiology

Quantum-limited mass flow of liquid 3^{3}He

We consider theoretically the possibility of observing unusual quantum fluid behavior in liquid $^{3}$He and solutions of $^{3}$He in $^{4}$He systems confined to nano-channels. In the case of pure ballistic flow at very low temperature conductance will be quantized in units of $2m^{2}/h$. We show that these steps should be sensitive to increases in temperature. We also use of a random scattering matrix simulation to study flow with diffusive wall scattering. Universal conductance fluctuations analogous to those seen in electron systems should then be observable. Finally we consider the possibility of the cross-over to a one-dimensional system at sufficiently low temperature where the system could form a Luttinger liquid