Electron transport in Coulomb- and tunnel-coupled one-dimensional systems

We develop a linear theory of electron transport for a system of two identical quantum wires in a wide range of the wire length L, unifying both the ballistic and diffusive transport regimes. The microscopic model, involving the interaction of electrons with each other and with bulk acoustical phonons allows a reduction of the quantum kinetic equation to a set of coupled equations for the local chemical potentials for forward- and backward-moving electrons in the wires. As an application of the general solution of these equations, we consider different kinds of electrical contacts to the double-wire system and calculate the direct resistance, the transresistance, in the presence of tunneling and Coulomb drag, and the tunneling resistance. If L is smaller than the backscattering length l_P, both the tunneling and the drag lead to a negative transresistance, while in the diffusive regime (L >>l_P) the tunneling opposes the drag and leads to a positive transresistance. If L is smaller than the phase-breaking length, the tunneling leads to interference oscillations of the resistances that are damped exponentially with L.Comment: Text 14 pages in Latex/Revtex format, 4 Postscript figure

Incoherent Transport through Molecules on Silicon in the vicinity of a Dangling Bond

We theoretically study the effect of a localized unpaired dangling bond (DB) on occupied molecular orbital conduction through a styrene molecule bonded to a n++ H:Si(001)-(2x1) surface. For molecules relatively far from the DB, we find good agreement with the reported experiment using a model that accounts for the electrostatic contribution of the DB, provided we include some dephasing due to low lying phonon modes. However, for molecules within 10 angstrom to the DB, we have to include electronic contribution as well along with higher dephasing to explain the transport features.Comment: 9 pages, 5 figure

Long-term reproductive costs of snare injuries in a keystone terrestrial by-catch species

Extensive bushmeat hunting is a major threat to wildlife conservation worldwide, particularly when unselective methods such as wire snares kill target and non-target species (by-catch). Animals that escape from snares have injuries of varying severity, with effects on performance that are largely unknown, as most studies typically focus on immediate mortality caused by snaring. Here, we assessed the life-history costs of debilitating snare injuries in individually known female spotted hyenas Crocuta crocuta in three clans in the Serengeti National Park, Tanzania. This keystone predator is a regular by-catch of illegal bushmeat hunting of herbivores in the Serengeti ecosystem. We monitored individuals which escaped from snares between May 1987 and March 2020 and survived long enough to return to their clan territories from commuting trips in the park and surrounding protected areas. Snares that inflicted debilitating injuries on females did not reduce longevity but did delay age at first reproduction and reduced both litter size and offspring survival to the age of 1 year. This long-term decrease in reproductive performance likely resulted from increased inflammatory and immune responses to the snare injury and/or a decreased ability to travel the long distances necessary to feed on migratory herbivores. While our results are based on a relatively small sample of females with debilitating injuries, they suggest that the total population-level costs of wire snares in terrestrial by-catch species may be underestimated and that future studies may need to account for the potential reproductive costs of sublethal snare injuries

Superfluid drag of two-species Bose-Einstein condensates in optical lattices

We study two-species Bose-Einstein condensates in quasi two-dimensional optical lattices of varying geometry and potential depth. Based on the numerically exact Bloch and Wannier functions obtained using the plane-wave expansion method, we quantify the drag (entrainment coupling) between the condensate components. This drag originates from the (short range) inter-species interaction and increases with the kinetic energy. As a result of the interplay between interaction and kinetic energy effects, the superfluid-drag coefficient shows a non-monotonic dependence on the lattice depth. To make contact with future experiments, we quantitatively investigate the drag for mass ratios corresponding to relevant atomic species.Comment: 6 pages, 4 figures. Accepted in its original form but minor changes have been don

Parasite infections in a social carnivore: Evidence of their fitness consequences and factors modulating infection load

There are substantial individual differences in parasite composition and infection load in wildlife populations. Few studies have investigated the factors shaping this heterogeneity in large wild mammals or the impact of parasite infections on Darwinian fitness, particularly in juveniles. A host's parasite composition and infection load can be shaped by factors that determine contact with infective parasite stages and those that determine the host's resistance to infection, such as abiotic and social environmental factors, and age. Host–parasite interactions and synergies between coinfecting parasites may also be important. We test predictions derived from these different processes to investigate factors shaping infection loads (fecal egg/oocyte load) of two energetically costly gastrointestinal parasites: the hookworm Ancylostoma and the intracellular Cystoisospora, in juvenile spotted hyenas (Crocuta crocuta) in the Serengeti National Park, in Tanzania. We also assess whether parasite infections curtail survival to adulthood and longevity. Ancylostoma and Cystoisospora infection loads declined as the number of adult clan members increased, a result consistent with an encounter‐reduction effect whereby adults reduced encounters between juveniles and infective larvae, but were not affected by the number of juveniles in a clan. Infection loads decreased with age, possibly because active immune responses to infection improved with age. Differences in parasite load between clans possibly indicate variation in abiotic environmental factors between clan den sites. The survival of juveniles (<365 days old) to adulthood decreased with Ancylostoma load, increased with age, and was modulated by maternal social status. High‐ranking individuals with low Ancylostoma loads had a higher survivorship during the first 4 years of life than high‐ranking individuals with high Ancylostoma loads. These findings suggest that high infection loads with energetically costly parasites such as hookworms during early life can have negative fitness consequences

Remarks on Causality in Relativistic Quantum Field Theory

It is shown that the correlations predicted by relativistic quantum field theory in locally normal states between projections in local von Neumann algebras \cA(V_1),\cA(V_2) associated with spacelike separated spacetime regions $V_1,V_2$ have a (Reichenbachian) common cause located in the union of the backward light cones of $V_1$ and $V_2$. Further comments on causality and independence in quantum field theory are made.Comment: 10 pages, Latex, Quantum Structures 2002 Conference Proceedings submission. Minor revision of the order of definitions on p.