ABSTRACT
A one-step replica-symmetry-breaking solution for finite-connectivity spin-glass models with K body interaction is constructed at finite temperature using the replica method and thermodynamic constraints. In the absence of external fields, this construction provides a general extension of replica symmetric solution at finite replica number to one-step replica-symmetry-breaking solution. It is found that this result is formally equivalent to that of the one-step replica-symmetry-breaking cavity method. To confirm the validity of the obtained solution, Monte Carlo simulations are performed for K=2 and 3. The thermodynamic quantities of the Monte Carlo results extrapolated to a large-size limit are consistent with those estimated by our solution for K=2 at all simulated temperatures and for K=3 except near the transition temperature.
ABSTRACT
We study the phase transition of a nonequilibrium statistical-mechanical model, in which two degrees of freedom with different time scales separated from each other touch their own heat bath. A general condition for finding anomalous negative latent heat recently discovered is derived from a thermodynamic argument. As a specific example, the phase diagram of a spin-lattice-gas model is studied based on a mean-field analysis with the replica method. While configurational variables are spin and particle in this model, it is found that the negative latent heat appears in a parameter region of the model, irrespective of the order of their time scale. Qualitative differences in the phase diagram are also discussed.
ABSTRACT
The stability of the spin-glass phase against a magnetic field is studied in the three- and four-dimensional Edwards-Anderson Ising spin glasses. Effective couplings J(eff) and effective fields H(eff) associated with length scale L are measured by a numerical domain-wall renormalization-group method. The results obtained by scaling analysis of the data strongly indicate the existence of a crossover length beyond which the spin-glass order is destroyed by field H. The crossover length well obeys a power law of H which diverges as H --> 0 but remains finite for any nonzero H, implying that the spin-glass phase is absent even in an infinitesimal field. These results are well consistent with the droplet theory for short-range spin glasses.
ABSTRACT
From a consideration of high temperature series expansions in ferromagnets and in spin glasses, we propose an extended scaling scheme involving a set of scaling formulas which expresses to leading order the temperature (T) and the system size (L) dependences of thermodynamic observables over a much wider range of T than the corresponding one in the conventional scaling scheme. The extended scaling, illustrated by data on the canonical 2d ferromagnet and on the 3d bimodal Ising spin glass, leads to consistency in the estimates of critical parameters obtained from scaling analyses for different observables.
ABSTRACT
The Néel temperature T(N) of quasi-one- and quasi-two-dimensional antiferromagnetic Heisenberg models on a cubic lattice is calculated by Monte Carlo simulations as a function of interchain (interlayer) to intrachain (intralayer) coupling J(')/J down to J(')/J approximately = 10(-3). We find that T(N) obeys a modified random-phase approximationlike relation for small J(')/J with an effective universal renormalized coordination number, independent of the size of the spin. Empirical formulas describing T(N) for a wide range of J(') and useful for the analysis of experimental measurements are presented.
ABSTRACT
Domain-wall free energy sigmaF, entropy sigmaS, and the correlation function C(temp) of sigmaF are measured independently in the four-dimensional +/-J Edwards-Anderson (EA) Ising spin glass. The stiffness exponent theta, the fractal dimension of domain walls d(s), and the chaos exponent zeta are extracted from the finite-size scaling analysis of sigmaF, sigmaS, and C(temp), respectively, well inside the spin-glass phase. The three exponents are confirmed to satisfy the scaling relation zeta = d(s)/2 - theta derived by the droplet theory within our numerical accuracy. We also study bond chaos induced by random variation of bonds, and find that the bond and temperature perturbations yield the universal chaos effects described by a common scaling function and the chaos exponent. These results strongly support the appropriateness of the droplet theory for the description of chaos effect in the EA Ising spin glasses.
ABSTRACT
Growth of the zero-field-cooled magnetization (ZFCM) under continuous heating with and without an intermittent stop(s) is studied on Ising spin glasses both experimentally and numerically. Despite the large difference between time scales of the experiment and the simulation, the ZFCM behavior observed in the two systems can be quantitatively interpreted by means of a common set of the scaling expressions based on the droplet picture. The results strongly suggest that the spin-glass coherence length reached by the laboratory time scales is about a hundred lattice spacings or less. Within this length scale no signature of the chaos effect (rejuvenation) has been found in the ZFCM measured.
ABSTRACT
Finite-size effects in the mean-field Ising spin glass and the mean-field three-state Potts glass are investigated by Monte Carlo simulations. In the thermodynamic limit, each model is known to exhibit a continuous phase transition into the ordered state with a full and a one-step replica-symmetry breaking (RSB), respectively. In the Ising case, the Binder parameter g calculated for various finite sizes remains positive at any temperature and crosses at the transition point, while in the Potts case g develops a negative dip without showing a crossing in the g>0 region. By contrast, non-self-averaging parameters always remain positive and show a clear crossing at the transition temperature in both cases. Our finding suggests that care should be taken in interpreting the numerical data of the Binder parameter, particularly when the system exhibits a one-step-like RSB.
ABSTRACT
Extensive equilibrium Monte Carlo simulations are performed for a three-dimensional Heisenberg spin glass with the nearest-neighbor Gaussian coupling to investigate its spin-glass and chiral-glass orderings. The occurrence of a finite-temperature chiral-glass transition without the conventional spin-glass order is established. Critical exponents characterizing the transition are different from those of the standard Ising spin glass. The calculated overlap distribution suggests the appearance of a peculiar type of replica-symmetry breaking in the chiral-glass ordered state.
ABSTRACT
An efficient Monte Carlo method is extended to evaluate directly domain-wall free energy for randomly frustrated spin systems. Using the method, critical phenomena of spin-glass phase transition are investigated in the 4d+/-J Ising model under the replica boundary condition. Our values of the critical temperature and exponent, obtained by finite-size scaling, are in good agreement with those of the standard Monte Carlo and the series expansion studies. In addition, two exponents, the stiffness exponent and the fractal dimension of the domain wall, which characterize the ordered phase, are obtained. The latter value is larger than d-1, indicating that the domain wall is really rough in the 4d Ising spin-glass phase.
ABSTRACT
We have been conducting surgical therapy for patients with atypical pulmonary mycobacteriosis (AM) since 1965 and have reported on the outcome of this approach to treatment. We have found that chemotherapy is not adequately efficacious against type III Mycobacterium avium complex (MAC), which suggests that surgical intervention may be the optimum approach for MAC. Among MAC patients who were treated surgically at our hospital in the period between 1966 and 1994, 74 cases on whom postoperative follow-up observation was possible served as the subjects of the present investigation. We report here on the outcome of treatment and related problems in these patients. Thirty-nine patients gave positive results for bacterial discharge on smear tests and all were positive on culture. Operation was performed on the right lung in 46 patients and on the left lung in 16. Pneumonectomy was conducted in 10 patients and lobectomy in 20. Other operative modes used included segmental resection in 9, pyothorax in 7, and thoracoplasty in 5 patients. Postoperative bacterial excretion was observed in 15 patients and was persistent bacterial discharge were advanced cases with lesions in another lobe, cases with a past history of tuberculosis, cases of cavitation with lesions on the contralateral side or cases with massive bacterial discharge prior to surgery. Postoperative death occurred in 5 patients: the cause of death was lung cancer in 1 case, serum hepatitis in 1 case, and respiratory failure evidenced by enlarged shadows in 3 cases. These findings pointed to a marked significance of surgical therapy for MAC patients. However, recurrent bacterial discharge has been observed occasionally in some patients even 5 years after surgery. This suggests the need for careful ongoing assessment of the efficacy of surgical therapy and long-term postoperative follow-up.
Subject(s)
Mycobacterium Infections, Nontuberculous/surgery , Tuberculosis, Pulmonary/surgery , Adult , Aged , Female , Humans , Male , Middle Aged , Postoperative ComplicationsABSTRACT
Intralobar pulmonary sequestration is a congenital disease characterized by nonfunctioning lung tissue with an anomalous blood supply stemming from the systemic circulation. We report a rare case of anomalous systemic arterial supply to the lung without demonstrable pulmonary changes. It is controversial whether this abnormality, systemic arterialization of lung without sequestration, should be a subtype of sequestration complex or not. We discuss the spectrum of sequestration complex.
Subject(s)
Pulmonary Artery/abnormalities , Radiography, Thoracic , Adult , Angiography, Digital Subtraction , Bronchopulmonary Sequestration , Humans , Male , Pulmonary Artery/diagnostic imaging , Pulmonary Artery/pathology , Tomography, X-Ray ComputedABSTRACT
We have reported that the morning mean rate of absorption (ka) in immediate release aminophylline tablet is significantly faster than the evening one without any obvious change in AUC, the distribution (Vd), the rate of elimination (kel) or the elimination half-time (t1/2) and this altered absorption is a cause of circadian variation of theophylline concentrations with sustained-release preparations. Now, we examined the effect of posture on theophylline absorption. Seven asthmatic children were given immediate release aminophylline tablets at the same time in the morning on two separate occasions. On one day they remained standing and on the other lying. Serum theophylline concentration was measured at 0, 0.5, 1, 2, 3, 4, 5 hours after dosing. Mean theophylline levels were higher in the standing position at all time and only the mean rate of absorption (ka) was significantly faster without any obvious change in parameters of pharmacokinetics. This result was almost consistent with differences of day and night theophylline kinetics. We conclude that slowness of absorption in the evening is mainly induced by difference in posture.
