63 research outputs found
Effective action and interaction energy of coupled quantum dots
We obtain the effective action of tunnel-coupled quantum dots, by modeling
the system as a Luttinger liquid with multiple barriers. For a double dot
system, we find that the resonance conditions for perfect conductance form a
hexagon in the plane of the two gate voltages controlling the density of
electrons in each dot. We also explicitly obtain the functional dependence of
the interaction energy and peak-splitting on the gate voltage controlling
tunneling between the dots and their charging energies. Our results are in good
agreement with recent experimental results, from which we obtain the Luttinger
interaction parameter .Comment: 5 pgs,latex,3 figs,revised version to be publshed in Phys.Rev.
Transport in Coupled Quantum Dots: Kondo Effect Versus Anti-Ferromagnetic Correlation
The interplay between the Kondo effect and the inter-dot magnetic interaction
in a coupled-dot system is studied. An exact result for the transport
properties at zero temperature is obtained by diagonalizing a cluster, composed
by the double-dot and its vicinity, which is connected to leads. It is shown
that the system goes continuously from the Kondo regime to an
anti-ferromagnetic state as the inter-dot interaction is increased. The
conductance, the charge at the dots and the spin-spin correlation are obtained
as a function of the gate potential.Comment: 4 pages, 3 postscript figures. Submitted to PR
Non Linear Current Response of a Many-Level Tunneling System: Higher Harmonics Generation
The fully nonlinear response of a many-level tunneling system to a strong
alternating field of high frequency is studied in terms of the
Schwinger-Keldysh nonequilibrium Green functions. The nonlinear time dependent
tunneling current is calculated exactly and its resonance structure is
elucidated. In particular, it is shown that under certain reasonable conditions
on the physical parameters, the Fourier component is sharply peaked at
, where is the spacing between
two levels. This frequency multiplication results from the highly nonlinear
process of photon absorption (or emission) by the tunneling system. It is
also conjectured that this effect (which so far is studied mainly in the
context of nonlinear optics) might be experimentally feasible.Comment: 28 pages, LaTex, 7 figures are available upon request from
[email protected], submitted to Phys.Rev.
Hypogene Calcitization: Evaporite Diagenesis in the Western Delaware Basin
Evaporite calcitization within the Castile Formation of the Delaware Basin is more widespread and diverse than originally recognized. Coupled field and GIS studies have identified more than 1000 individual occurrences of calcitization within the Castile Formation outcrop area, which includes both calcitized masses (limestone buttes) and laterally extensive calcitized horizons (limestone sheets). Both limestone buttes and sheets commonly contain a central brecciated zone that we attribute to hypogene dissolution. Lithologic fabric of calcitized zones ranges from little alteration of original varved laminae to fabrics showing extensive laminae distortion as well as extensive vuggy and open cavernous porosity. Calcitization is most abundant in the western portion of the Castile outcrop region where surface denudation has been greatest. Calcitization often forms linear trends, indicating fluid migration along fractures, but also occurs as dense clusters indicating focused, ascending, hydrocarbon-rich fluids. Native sulfur, secondary tabular gypsum (i.e. selenite) and hypogene caves are commonly associated with clusters of calcitization. This assemblage suggests that calcium sulfate diagenesis within the Castile Formation is dominated by hypogene speleogemesis
Selective Depletion of Staphylococcus aureus Restores the Skin Microbiome and Accelerates Tissue Repair after Injury
Our skin is home to a diverse community of commensal microorganisms integral to cutaneous function. However, microbial dysbiosis and barrier perturbation increase the risk of local and systemic infection. Staphylococcus aureus is a particularly problematic bacterial pathogen, with high levels of antimicrobial resistance and direct association with poor healing outcome. Innovative approaches are needed to selectively kill skin pathogens, such as S aureus, without harming the resident microbiota. In this study, we provide important data on the selectivity and efficacy of an S aureus–targeted endolysin (XZ.700) within the complex living skin/wound microbiome. Initial cross-species comparison using Nanopore long-read sequencing identified the translational potential of porcine rather than murine skin for human-relevant microbiome studies. We therefore performed an interventional study in pigs to assess the impact of endolysin administration on the microbiome. XZ.700 selectively inhibited endogenous porcine S aureus in vivo, restoring microbial diversity and promoting multiple aspects of wound repair. Subsequent mechanistic studies confirmed the importance of this microbiome modulation for effective healing in human skin. Taken together, these findings strongly support further development of S aureus–targeted endolysins for future clinical management of skin and wound infections
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Magnetization Reversal Behavior in Cobalt Rare-Earth Thin Films
Cobalt RareEarth (CoR, R = Pr,Sm) thin films on a Cr underlayer have shown promise as future ultra high density magnetic recording media. The activation volume or the magnetic switching volume (v*) is an important consideration for thermal stability and media noise in high density recording media and V* can also provide information about the magnetization reversal behavior in these films. The magnetic switching volume was estimated for the CoPr films with thicknesses from 28 to 639 nm with a Cr underlayer of 80 nm annealed at 500 0C. The measured switching volume ranges from 1.3 to 1.7x10-18 cm3. We have also studied the Cr underlayer thickness and temperature effects on the swithcing volume for the CoSm films
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