1,505 research outputs found
Universal Reduction of Effective Coordination Number in the Quasi-One-Dimensional Ising Model
Critical temperature of quasi-one-dimensional general-spin Ising ferromagnets
is investigated by means of the cluster Monte Carlo method performed on
infinite-length strips, L times infty or L times L times infty. We find that in
the weak interchain coupling regime the critical temperature as a function of
the interchain coupling is well-described by a chain mean-field formula with a
reduced effective coordination number, as the quantum Heisenberg
antiferromagnets recently reported by Yasuda et al. [Phys. Rev. Lett. 94,
217201 (2005)]. It is also confirmed that the effective coordination number is
independent of the spin size. We show that in the weak interchain coupling
limit the effective coordination number is, irrespective of the spin size,
rigorously given by the quantum critical point of a spin-1/2 transverse-field
Ising model.Comment: 12 pages, 6 figures, minor modifications, final version published in
Phys. Rev.
Sequential minimal optimization for quantum-classical hybrid algorithms
We propose a sequential minimal optimization method for quantum-classical
hybrid algorithms, which converges faster, is robust against statistical error,
and is hyperparameter-free. Specifically, the optimization problem of the
parameterized quantum circuits is divided into solvable subproblems by
considering only a subset of the parameters. In fact, if we choose a single
parameter, the cost function becomes a simple sine curve with period ,
and hence we can exactly minimize with respect to the chosen parameter.
Furthermore, even in general cases, the cost function is given by a simple sum
of trigonometric functions with certain periods and hence can be minimized by
using a classical computer. By repeatedly performing this procedure, we can
optimize the parameterized quantum circuits so that the cost function becomes
as small as possible. We perform numerical simulations and compare the proposed
method with existing gradient-free and gradient-based optimization algorithms.
We find that the proposed method substantially outperforms the existing
optimization algorithms and converges to a solution almost independent of the
initial choice of the parameters. This accelerates almost all quantum-classical
hybrid algorithms readily and would be a key tool for harnessing near-term
quantum devices.Comment: 11 pages, 4 figure
Is rejection a diffuse or localized process in small-bowel transplantation?
Utilization of endoscopy to both visualize and selectively biopsy an intestinal allograft has become the standard for early recognition and treatment of intestinal allograft rejection. Despite the widespread acceptance of the need for selective mucosal biopsies, it has not been shown that the histological features of intestinal allograft rejection are either localized or occur as part of a more diffuse phenomenon within a tubular allograft. To resolve these issues, 88 ileoscopies were performed in 12 small-bowel allograft recipients and mucosal biopsy samples were obtained at 5, 10, and 15 cm, respectively, from the ileal stoma. Each mucosal biopsy was labeled, processed, and evaluated individually for the presence and severity of any evidence for allograft rejection. The data obtained suggest that intestinal allograft rejection is a diffuse process, and biopsies obtained randomly from an ileal graft are likely to demonstrate evidence of allograft rejection when such is present. © 1994 Springer-Verlag New York Inc
Aspergillosis of the CNS in a pediatric liver transplant recipient: Case report and review
A 2-month-old infant who had undergone orthotopic liver transplantation at the age of 2 weeks for carbamoyl phosphate synthetase deficiency developed infection of the CNS due to Aspergillus fumigatus. The patient was successfully treated with administration of a combination of antifungal agents (including intraventricular amphotericin B), drainage of the parietal lobe abscess, and cessation of immunosuppression. An intraventricular catheter was used both to obtain ventricular fluid for microbiologic testing and to deliver amphotericin B during nearly 4 months of treatment. We review literature on aspergillosis in solid-organ transplant recipients, especially those in whom the disease involves the CNS, and discuss in particular clinical presentation, diagnosis, treatment, and outcome
Combined immunosuppressive therapy with low dose FK506 and antimetabolites in rat allogeneic heart transplantation
Following rat heterotopic heart allotransplantation, low to lethal doses of the antimetabolites mizoribine (MIZ), RS-61443 (RS), and AZA were given alone or in combination with subtherapeutic doses of FK506 (0.04 mg/kg/day) for 14 days after transplantation. With the median effect analysis of Chou and Kahan for quantitative drug interactions, substantial therapeutic synergism was demonstrated between FK506 and nontoxic doses of MĪZ (2.5, 5, and 10 mg/kg/day) or AZA (5, 30, and 45 mg/kg/day), which was particularly evident with the lowest dose MIZ (2.5 mg/kg/day). When FK506 was used in combination with MIZ or AZA but not with RS, the maximum effect (peak median graft survival) was enhanced significantly from 15 days (MIZ alone) to 26 days (P<0.05), and from 19 days (AZA alone) to 32 days (P<0.0l). In contrast, RS interacted with FK506 no more than additively. Although RS was the most powerful single antimetabolite, the best overall survival was obtained by combining AZA and FK506. The addition of FK506 did not significantly increase the percent mortality and LD50 of the antimetabolites. © 1994 by Williams and Wilkins
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