1,365 research outputs found
Host Resistance to the Khartoum Strain of Leishmania donovani
Talk given by Leslie A. Stauber from the Bureau of Biological Research, Rutgers, The State University, New Brunswick, New Jerse
Graphic representation of salinity in a tidal estuary
In any study of organisms in tidal estuarine areas, such as the oyster and its associates, the salinity of the water is of recognized importance as a factor limiting the distribution and controlling the activity (movement, feeding, spawning) of the various species
Flow equations for Hamiltonians: Contrasting different approaches by using a numerically solvable model
To contrast different generators for flow equations for Hamiltonians and to
discuss the dependence of physical quantities on unitarily equivalent, but
effectively different initial Hamiltonians, a numerically solvable model is
considered which is structurally similar to impurity models. By this we discuss
the question of optimization for the first time. A general truncation scheme is
established that produces good results for the Hamiltonian flow as well as for
the operator flow. Nevertheless, it is also pointed out that a systematic and
feasible scheme for the operator flow on the operator level is missing. For
this, an explicit analysis of the operator flow is given for the first time. We
observe that truncation of the series of the observable flow after the linear
or bilinear terms does not yield satisfactory results for the entire parameter
regime as - especially close to resonances - even high orders of the exact
series expansion carry considerable weight.Comment: 25 pages, 10 figure
Conductivity of suspended and non-suspended graphene at finite gate voltage
We compute the DC and the optical conductivity of graphene for finite values
of the chemical potential by taking into account the effect of disorder, due to
mid-gap states (unitary scatterers) and charged impurities, and the effect of
both optical and acoustic phonons. The disorder due to mid-gap states is
treated in the coherent potential approximation (CPA, a self-consistent
approach based on the Dyson equation), whereas that due to charged impurities
is also treated via the Dyson equation, with the self-energy computed using
second order perturbation theory. The effect of the phonons is also included
via the Dyson equation, with the self energy computed using first order
perturbation theory. The self-energy due to phonons is computed both using the
bare electronic Green's function and the full electronic Green's function,
although we show that the effect of disorder on the phonon-propagator is
negligible. Our results are in qualitative agreement with recent experiments.
Quantitative agreement could be obtained if one assumes water molelcules under
the graphene substrate. We also comment on the electron-hole asymmetry observed
in the DC conductivity of suspended graphene.Comment: 13 pages, 11 figure
Entanglement at the boundary of spin chains near a quantum critical point and in systems with boundary critical points
We analyze the entanglement properties of spins (qubits) attached to the
boundary of spin chains near quantum critical points, or to dissipative
environments, near a boundary critical point, such as Kondo-like systems or the
dissipative two level system. In the first case, we show that the properties of
the entanglement are significantly different from those for bulk spins. The
influence of the proximity to a transition is less marked at the boundary. In
the second case, our results indicate that the entanglement changes abruptly at
the point where coherent quantum oscillations cease to exist. The phase
transition modifies significantly less the entanglement.Comment: 5 pages, 4 figure
Disorder and interaction effects in two dimensional graphene sheets
The interplay between different types of disorder and electron-electron
interactions in graphene planes is studied by means of Renormalization Group
techniques. The low temperature properties of the system are determined by
fixed points where the strength of the interactions remains finite, as in one
dimensional Luttinger liquids. These fixed points can be either stable
(attractive), when the disorder is associated to topological defects in the
lattice or to a random mass term, or unstable (repulsive) when the disorder is
induced by impurities outside the graphene planes. In addition, we analyze
mid-gap states which can arise near interfaces or vacancies.Comment: 4 pages, 3 figure
First Order Superfluid to Bose Metal Transition in Systems with Resonant Pairing
Systems showing resonant superfluidity, driven by an exchange coupling of
strength between uncorrelated pairs of itinerant fermions and tightly bound
ones, undergo a first order phase transition as increases beyond some
critical value . The superfluid phase for is characterized by
a gap in the fermionic single particle spectrum and an acoustic sound-wave like
collective mode of the bosonic resonating fermion pairs inside this gap. For
this state gives way to a phase uncorrelated bosonic liquid with a
spectrum.Comment: 5 pages, 3 figure
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