The ground state of the two-dimensional Hubbard model

We have studied the ground state of the two-dimensional Hubbard model by using the adaptive sampling quantum monte carlo method. We found enhancement of the d-wave correlation function, the spin gap and the coexistence of both the commensurate and incommensurate peaks in $S(\vec{q})$, which does not contradict a recent experimental finding that both the resonance peak and the incommensurate peaks reside in the same doping level of YBCO and BSCCO.Comment: To be published in Proceedings of Strongly Correlated Electron System (SCES99

The Demise of Bank-centered Economy and Increasing Roles of Credit Rating in Japan

After the burst of the bubble economy, Japanese economy has been changed drastically. Traditionally, Japanese economy was characterized as a bank-centered economy, but the banking system did not function well in the 1990's. Responding to banking problems, the Japanese government initiated the Financial Big Bang in 1996 to strength the capability of capital markets. Also, accounting and disclosure rules have been revised to make more credible and wider information available to market participants. If other things be constant, more extensive and timely disclosure should result in more accurate evaluation of firm's risks. However, there is a lack of research that investigates how effective current disclosure is in evaluating corporate risks. This lack of research is mainly because there are not appropriate data sets and methodology to be used for empirical tests. Fortunately, Morgan (2002) proposed a very useful method. That is, he used the disagreement between credit rating companies (i.e., Moody's and Standard and Poor's) over new issued bonds to measure the difficulty in evaluating firms' risks. In this paper, we follow Morgan (2002) and investigate whether credit rating companies likely agreed on the evaluation on Japanese firms' risks after the financial and accounting Big Bang. If there are still large disagreements among credit rating companies, this fact suggests that the current disclosure is not enough for outsiders to evaluate firms, or that there is an inherent limitation of disclosure usage. Also, we are interested in what sectors credit rating companies more often disagree on. Contrary to Morgan (2002), which pointed out that financial industries, such as banks and insurance companies, are difficult to evaluate, we failed to find that disagreements among credit rating companies over banks and insurance companies are larger than disagreements over other industries. However, consistent with Morgan (2002), we found that public utilities industry is easy to evaluate. This paper is organized as follows. In Section 2, we discuss the current Japanese economic situation and explain the accounting and disclosure reform. In Section 3, we explain data and methodology that are used in this paper. In Section 4, empirical results are provided. Section 5 concludes this paper.

Credit Ratings in the Japanese Bond Market

Recently, credit ratings have been enhancing the influence on issuers as well as the national economy. This paper explains the historical development and several current features of the Japanese bond market, and discusses why credit ratings gained a significant role in the 1990s. We also present empirical research on credit ratings in the Japanese bond market, and discuss how foreign raters tend to assign lower credit ratings than Japanese ones, but that the relative ratings among raters end up being similar. Finally, we clarify the issues that remained to be solved before credit rating companies can be considered truly reliable.

First-principles calculation of the thermoelectric figure of merit for [2,2]paracyclophane-based single-molecule junctions

Here we present a theoretical study of the thermoelectric transport through {[}2,2{]}para\-cyclo\-phane-based single-molecule junctions. Combining electronic and vibrational structures, obtained from density functional theory (DFT), with nonequilibrium Green's function techniques, allows us to treat both electronic and phononic transport properties at a first-principles level. For the electronic part, we include an approximate self-energy correction, based on the DFT+$\Sigma$ approach. This enables us to make a reliable prediction of all linear response transport coefficients entering the thermoelectric figure of merit $ZT$. Paracyclophane derivatives offer a great flexibility in tuning their chemical properties by attaching different functional groups. We show that, for the specific molecule, the functional groups mainly influence the thermopower, allowing to tune its sign and absolute value. We predict that the functionalization of the bare paracyclophane leads to a largely enhanced electronic contribution $Z_{\mathrm{el}}T$ to the figure of merit. Nevertheless, the high phononic contribution to the thermal conductance strongly suppresses $ZT$. Our work demonstrates the importance to include the phonon thermal conductance for any realistic estimate of the $ZT$ for off-resonant molecular transport junctions. In addition, it shows the possibility of a chemical tuning of the thermoelectric properties for a series of available molecules, leading to equally performing hole- and electron-conducting junctions based on the same molecular framework.Comment: 8 pages, 7 figure

Credit Ratings in the Japanese Bond Market

Recently, credit ratings have been enhancing the influence on issuers as well as the national economy. This paper explains the historical development and several current features of the Japanese bond market, and discusses why credit ratings gained a significant role in the 1990s. We also present empirical research on credit ratings in the Japanese bond market, and discuss how foreign raters tend to assign lower credit ratings than Japanese ones, but that the relative ratings among raters end up being similar. Finally, we clarify the issues that remained to be solved before credit rating companies can be considered truly reliable

振電相互作用の機構に関する理論的研究

京都大学0048新制・課程博士工学博士甲第3756号工博第955号新制||工||686(附属図書館)UT51-62-J292京都大学大学院工学研究科石油化学専攻(主査)教授 山邊 時雄, 教授 米澤 貞次郎, 教授 ホール ジョージ・ガーフィールド学位規則第5条第1項該当Kyoto UniversityDFA

Implementation of Do Not Attempt Resuscitate Orders in a Japanese Nursing Home

Objective: To investigate whether do not attempt resuscitation (DNAR) orders can be implemented in a standard nursing home in Japan, where routine DNAR orders are not yet common in many facilities including hospitals. Method: Ninety-eight residents in a 100-bed nursing home were evaluated. All of the eligible residents and/or their family members were asked whether they wanted to receive resuscitation, including mechanical ventilation. Result: The residents were 54 to 101 years of age (mean 83.3), with 27 males and 71 females. After administering the questionnaire, 92 (94%) patients did not want resuscitation and mechanical ventilation. Conclusion: In a nursing home, it was possible to obtain advance directives by which most residents/families rejected resuscitation and mechanical ventilation. This could avoid unnecessary and undesirable resuscitation procedures

Slow and Fast Transitions in the Rising Phase of Outbursts from NS-LMXB transients, AqlX-1 and 4U1608-52

We analyzed the initial rising behaviors of X-ray outbursts from two transient low-mass X-ray binaries (LMXBs) containing a neutron-star (NS), Aql X-1 and 4U 1608-52, which are continuously being monitored by MAXI/GSC in 2--20 keV, RXTE/ASM in 2--10 keV, and Swift/BAT in 15--50 keV. We found that the observed ten outbursts are classified into two types by the patterns of the relative intensity evolutions in the two energy bands below/above 15 keV. One type behaves as the 15--50 keV intensity achieves the maximum during the initial hard-state period and drops greatly at the hard-to-soft state transition. On the other hand, the other type does as both the 2--15 keV and the 15--50 keV intensities achieve the maximums after the transition. The former have the longer initial hard-state ($\gtrsim$ 9 d) than the latter's (\ltsim5 d). Therefore, we named them as slow-type (S-type) and fast-type (F-type), respectively. These two types also show the differences in the luminosity at the hard-to-soft state transition as well as in the average luminosity before the outburst started, where the S-type are higher than the F-type in the both. These results suggest that the X-ray radiation during the pre-outburst period, which heats up the accretion disk and delays the disk transition (i.e., from a geometrically thick disk to a thin one), would determine whether the following outburst becomes S-type or F-type. The luminosity when the hard-to-soft state transition occurs is higher than $\sim 8 \times10^{36}$ erg s$^{-1}$ in the S-type, which corresponds to 4% of the Eddington luminosity for a 1.4 \Mo NS.Comment: 14 pages, 10 figures; Publications of the Astronomical Society of Japan, 201