Biomedical subjects

R H McKenzie

Publications and source records attributed to R H McKenzie.

4 recordsLinked to original sources

PubMed2005

Measurement-based teleportation along quantum spin chains.

We examine the teleportation of an unknown spin-1/2 quantum state along a quantum spin chain with an even number of sites. Our protocol, using a sequence of Bell measurements, may be viewed as an iterated version of the 2-qubit protocol of C. H. Bennett et al. [Phys. Rev. Lett. 70, 1895 (1993)]. A decomposition of the Hilbert space of the spin chain into 4 vector spaces, called Bell subspaces, is given. It is established that any state from a Bell subspace may be used as a channel to perform unit fidelity teleportation. The space of all spin-0 many-body states, which includes the ground states of many known antiferromagnetic systems, belongs to a common Bell subspace. A channel-dependent teleportation parameter [symbol: see text] is introduced, and a bound on the teleportation fidelity is given in terms of [symbol: see text].

Journal Article↗

PubMed2001

Superconductivity mediated by charge fluctuations in layered molecular crystals.

We consider the competition between superconducting, charge ordered, and metallic phases in layered molecular crystals with the theta and beta(") structures. Applying slave-boson theory to the relevant extended Hubbard model, we show that the superconductivity is mediated by charge fluctuations and the Cooper pairs have d(xy) symmetry. This is in contrast to the kappa-(BEDT-TTF)(2)X family, for which theoretical calculations give superconductivity mediated by spin fluctuations and with d(x(2)-y(2)) symmetry. We predict several materials that should become superconducting under pressure.

Journal Article↗

PubMed2001

Ladder operator for the one-dimensional Hubbard model.

The one-dimensional Hubbard model is integrable in the sense that it has an infinite family of conserved currents. We explicitly construct a ladder operator which can be used to iteratively generate all of the conserved current operators. This construction is different from that used for Lorentz invariant systems such as the Heisenberg model. The Hubbard model is not Lorentz invariant, due to the separation of spin and charge excitations. The ladder operator is obtained by a very general formalism which is applicable to any model that can be derived from a solution of the Yang-Baxter equation.

Journal Article↗

PubMedDate not supplied

Disseminated BCG infection following bone marrow transplantation for X-linked severe combined immunodeficiency.

An 8-month-old boy with X-linked severe combined immunodeficiency (XSCID) developed disseminated bacille Calmette-Guerin (BCG) infection following BCG vaccination at birth. He initially presented with an abscess at the site of BCG vaccination and was begun on three-drug antituberculous treatment (rifampicin, isoniazid, and pyrazinimide). Dissemination was subclinical prior to a human leukocyte antigen (HLA)-identical bone marrow transplant (BMT) from his sister, following which he presented with an acute erythroderma. A skin biopsy specimen revealed granulomas with epithelial histiocytes and giant cells in the reticular dermis, and numerous acid-fast bacilli (AFB) were present on Ziehl-Nielsen stain. A diagnosis of disseminated BCG disease was made. Despite the addition of a fourth antituberculous agent, ethambutol, he did not recover and developed numerous skin abscesses over the following weeks. Examination of pus from these lesions demonstrated numerous AFB. Clarithromycin was added as a fifth antituberculous agent. Despite five-drug antituberculous therapy and monthly intravenous immunoglobulin infusions, recurrent abscesses containing AFB developed intermittently until 7 months posttransplant. At follow-up 1 year post-BMT he showed good general physical improvement. All abscesses had healed with scarring, and no further skin lesions had occurred.

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