Biomedical subjects

Yuzuru Sato

Publications and source records attributed to Yuzuru Sato.

6 recordsLinked to original sources

PubMed2005

Asymptotically scale-invariant occupancy of phase space makes the entropy Sq extensive.

Phase space can be constructed for N equal and distinguishable subsystems that could be probabilistically either weakly correlated or strongly correlated. If they are locally correlated, we expect the Boltzmann-Gibbs entropy S(BG) identical with -k Sigma(i) p(i) ln p(i) to be extensive, i.e., S(BG)(N) proportional, variant N for N --> infinity. In particular, if they are independent, S(BG) is strictly additive, i.e., S(BG)(N) = NS(BG)(1), for allN. However, if the subsystems are globally correlated, we expect, for a vast class of systems, the entropy S(q) identical with k[1 - Sigma(i) p(q)(i)]/(q - 1) (with S(1) = S(BG)) for some special value of q not equal 1 to be the one which is extensive [i.e., S(q)(N) proportional, variant N for N --> infinity]. Another concept which is relevant is strict or asymptotic scale-freedom (or scale-invariance), defined as the situation for which all marginal probabilities of the N-system coincide or asymptotically approach (for N --> infinity) the joint probabilities of the (N - 1)-system. If each subsystem is a binary one, scale-freedom is guaranteed by what we hereafter refer to as the Leibnitz rule, i.e., the sum of two successive joint probabilities of the N-system coincides or asymptotically approaches the corresponding joint probability of the (N - 1)-system. The kinds of interplay of these various concepts are illustrated in several examples. One of them justifies the title of this paper. We conjecture that these mechanisms are deeply related to the very frequent emergence, in natural and artificial complex systems, of scale-free structures and to their connections with nonextensive statistical mechanics. Summarizing, we have shown that, for asymptotically scale-invariant systems, it is S(q) with q not equal 1, and not S(BG), the entropy which matches standard, clausius-like, prescriptions of classical thermodynamics.

Journal Article↗

PubMed2004

Hypoplasia of the right hepatic lobe associated with portal hypertension and idiopathic retroperitoneal fibrosis.

A 22-year-old man was referred to our hospital because of thrombocytopenia. Abdominal computed tomography (CT) revealed hypoplasia of the right hepatic lobe, the development of porto-systemic collateral vessels, splenomegaly and a periaortic soft-tissue mass. Laboratory tests and needle liver biopsy indicated no evidence of liver cirrhosis. Consequently, a diagnosis of hypoplasia of the right hepatic lobe associated with portal hypertension and idiopathic retroperitoneal fibrosis was established. Portal hypertension and hypersplenism was thought to be the cause of the thrombocytopenia. CT arterioportography revealed that anomalies of the portal venous system could have resulted in the hypoplasia of the right hepatic lobe. This is the first report describing hypoplasia of the right hepatic lobe accompanied by supervening idiopathic retroperitoneal fibrosis.

Abdomen↗

PubMed2003

Coupled replicator equations for the dynamics of learning in multiagent systems.

Starting with a group of reinforcement-learning agents we derive coupled replicator equations that describe the dynamics of collective learning in multiagent systems. We show that, although agents model their environment in a self-interested way without sharing knowledge, a game dynamics emerges naturally through environment-mediated interactions. An application to rock-scissors-paper game interactions shows that the collective learning dynamics exhibits a diversity of competitive and cooperative behaviors. These include quasiperiodicity, stable limit cycles, intermittency, and deterministic chaos-behaviors that should be expected in heterogeneous multiagent systems described by the general replicator equations we derive.

Journal Article↗

PubMed2002

Chaos in learning a simple two-person game.

We investigate the problem of learning to play the game of rock-paper-scissors. Each player attempts to improve her/his average score by adjusting the frequency of the three possible responses, using reinforcement learning. For the zero sum game the learning process displays Hamiltonian chaos. Thus, the learning trajectory can be simple or complex, depending on initial conditions. We also investigate the non-zero sum case and show that it can give rise to chaotic transients. This is, to our knowledge, the first demonstration of Hamiltonian chaos in learning a basic two-person game, extending earlier findings of chaotic attractors in dissipative systems. As we argue here, chaos provides an important self-consistency condition for determining when players will learn to behave as though they were fully rational. That chaos can occur in learning a simple game indicates one should use caution in assuming real people will learn to play a game according to a Nash equilibrium strategy.

Game Theory↗

PubMed2002

Factors affecting complete resection of gastric tumors by the endoscopic mucosal resection procedure.

BACKGROUND: In Japan, endoscopic mucosal resection (EMR) has been widely used as a treatment option for small early gastric cancer (EGC). The present study reviewed 178 cases for the 10-year period 1987-1997 in order to clarify the factors affecting the successful outcome of EMR. METHODS: Logistic regression analysis was used to examine whether complete resection of EGC correlated with the patient's age, gender, the characteristics of the tumor (location, macroscopic form, and size), the duration of the procedure and the experience of the doctor. RESULTS: The location of the tumor and the duration of the procedure correlated with the completeness of the resection (P < 0.01 and P < 0.05, respectively). Endoscopic mucosal resection was more difficult to perform for tumors in the gastric body than in the antrum or incisura region, and the longer the procedure the less complete the resection. CONCLUSION: The outcome of EMR is affected significantly by the location of the EGC.

Aged↗

PubMed2002

Efficacy of Stronger Neo-Minophagen C compared between two doses administered three times a week on patients with chronic viral hepatitis.

BACKGROUND: A daily injection of glycyrrhizin (Stronger Neo-Minophagen C (SNMC) containing 40 mg glycyrrhizin in a 20 mL ampoule) lowers alanine aminotransferase (ALT) levels in patients with chronic viral hepatitis. METHODS: The therapeutic effects of intermittent administration of SNMC three times a week for 12 weeks were evaluated and compared between two doses (40 and 100 mL) in a randomized clinical trial. RESULTS: Overall, the therapeutic response was better in the 53 patients allocated 100 mL than the 59 who were allocated to have 40 mL SNMC (P = 0.0243). At the completion of SNMC treatment, ALT levels decreased more extensively in the patients on 100 mL than those on 40 mL SNMC (-29 vs-50% in comparison with the baseline value, P = 0.0002). Minor side-effects occurred in both the patients on 100 mL (20%) and those on 40 mL (12%), but they did not require any therapies. CONCLUSIONS: Intermittent SNMC would be efficient in suppressing ALT levels in patients with chronic viral hepatitis in a dose-dependent manner. Taken along with infrequent and very mild side-effects, long-term intermittent SNMC would benefit patients with chronic hepatitis by maintaining their quality of life with easier compliance.

Alanine Transaminase↗