Cr-Triggered Local Structural Change in Cr2Ge2Te6 Phase Change Material.

Cr2Ge2Te6 (CrGT) is a phase change material with higher resistivity in the crystalline phase than in the amorphous phase. CrGT exhibits an ultralow operation energy for amorphization. In this study, the origin of the increased resistance in crystalline CrGT compared to amorphous CrGT and the underlying phase change mechanism were investigated in terms of both local structural change and associated change in electronic state. The density of states at the Fermi level in crystalline CrGT decreased with increasing annealing temperature and became negligible upon annealing at 380 °C. Simultaneously, the Fermi level shifted from the vicinity of the valence band to the band gap center, leading to an increase in resistance. The phase change from amorphous to crystalline CrGT occurred through a metastable crystalline phase with a local structure similar to that of the amorphous phase. Cr nanoclusters were confirmed to exist in both the amorphous and crystalline phases. The presence of Cr nanoclusters induced Cr vacancies in the crystalline phase. These Cr vacancies generated hole carriers, leading to p-type conduction. Photoelectron spectroscopy of the Cr 2s core level clearly indicated a decrease in the fraction of Cr-Cr bonds and an increase in the fraction of Cr-Te bonds in crystalline CrGT upon annealing. Meanwhile, the coordination number of the Cr nanoclusters decreased as the number of Cr-Cr bonds was reduced. Together, these results imply that the origin of the increased resistance in crystalline CrGT is the filling of Cr vacancies by Cr atoms diffusing from Cr nanoclusters.

Inverse Resistance Change Cr2Ge2Te6-Based PCRAM Enabling Ultralow-Energy Amorphization.

Phase-change random access memory (PCRAM) has attracted much attention for next-generation nonvolatile memory that can replace flash memory and can be used for storage-class memory. Generally, PCRAM relies on the change in the electrical resistance of a phase-change material between high-resistance amorphous (reset) and low-resistance crystalline (set) states. Herein, we present an inverse resistance change PCRAM with Cr2Ge2Te6 (CrGT) that shows a high-resistance crystalline reset state and a low-resistance amorphous set state. The inverse resistance change was found to be due to a drastic decrease in the carrier density upon crystallization, which causes a large increase in contact resistivity between CrGT and the electrode. The CrGT memory cell was demonstrated to show fast reversible resistance switching with a much lower operating energy for amorphization than a Ge2Sb2Te5 memory cell. This low operating energy in CrGT should be due to a small programmed amorphous volume, which can be realized by a high-resistance crystalline matrix and a dominant contact resistance. Simultaneously, CrGT can break the trade-off relationship between the crystallization temperature and operating speed.

Implementation of pulse timing discriminator functionality into a GeSbTe/GeCuTe double layer structure.

The functionality of a pulse timing discriminator, which is commonly required in optical communication systems and artificial neuromorphic engineering, was implemented into chalcogenide phase-change materials. GeSbTe (GST) and GeCuTe (GCT), which exhibit opposite refractive index behavior in their respective crystalline and amorphous phases, were employed. A GST/GCT double layer enabled the order of arrival of two counter-propagating femtosecond pulses to be encoded as a difference in the degree of amorphization of the GCT layer, i.e., either a brighter or darker contrast of the amorphized area with respect to the crystalline background. Nonthermal ultrafast amorphization contributed to a picosecond time resolution in the discrimination of the pulse arrival order.

Effects of pitavastatin in Japanese patients with chronic heart failure: the Pitavastatin Heart Failure Study (PEARL Study).

BACKGROUND: Recent clinical trials using rosuvastatin, a hydrophilic statin, did not show beneficial effects on cardiovascular events in patients with heart failure. We examined the cardioprotective effects of pitavastatin, a lipophilic statin, on Japanese patients with chronic heart failure (CHF). METHODS AND RESULTS: A total of 574 Japanese patients with CHF were randomly assigned to the pitavastatin group (n=288) or the control group (n=286). There was no significant difference between the 2 groups for the primary outcome, which was a composite of cardiac death and hospitalization for worsening HF (adjusted hazard ratio (aHR): 0.922, 95% confidence interval (CI): 0.632-1.345, P=0.672). A strongly significant statistical interaction between the effect of pitavastatin and left ventricular ejection fraction (LVEF) was found (P=0.004). In patients with LVEF ≥30%, a significant reduction in the primary outcome (aHR: 0.525, 95% CI: 0.308-0.896, P=0.018) was observed in the pitavastatin group. Pitavastatin did not show any effects on the primary outcome (aHR: 1.582, 95% CI: 0.890-2.813, P=0.118) in the subgroup of patients with LVEF <30%. CONCLUSIONS: Pitavastatin did not reduce cardiac death or hospitalization for worsening HF in Japanese patients with CHF. (UMIN-ID: UMINC000000428).

Rationale and design of a study to evaluate effects of pitavastatin on Japanese patients with chronic heart failure: the pitavastatin heart failure study (PEARL study).

BACKGROUND: HMG-CoA reductase inhibitors (statins) are known to have pleiotropic effects in addition to their lipid-lowering effect. Many studies have suggested cardioprotective effects of statins, however, recent large-scale clinical trials using rosuvastatin, a hydrophilic statin, have failed to show beneficial effects on cardiovascular events in patients with severe heart failure. We have designed the study to evaluate the effects of pitavastatin, a lipophilic statin, on Japanese patients with mild to moderate heart failure. METHODS AND RESULTS: Five hundred seventy-seven patients with chronic heart failure were enrolled. We used a prospective, randomized, open-label, and blinded-endpoint evaluation (PROBE) design. Patients aged 20-79 years old with symptomatic (NYHA functional class II or III) heart failure and a left ventricular ejection fraction of ≤ 45% were randomly allocated to either receive pitavastatin (2mg/day) or not in addition to conventional therapy for heart failure by using the minimization method. Follow-up will be continued until March 2011. The primary endpoint is a composite of cardiac death and hospitalization for worsening heart failure. CONCLUSIONS: The PEARL study will provide important data on the role of pitavastatin in the treatment of Japanese patients with mildly symptomatic heart failure (UMIN-ID: UMINC000000428).

Effects of valsartan and amlodipine on cardiorenal protection in Japanese hypertensive patients: the Valsartan Amlodipine Randomized Trial.

The Valsartan Amlodipine Randomized Trial, a multicenter, prospective, randomized, open-labeled, blinded-end point trial, was designed to compare the beneficial effects of the angiotensin II receptor blocker valsartan and the calcium channel blocker amlodipine on cardiovascular events in Japanese essential hypertensive patients. The primary end point was a composite of all-cause death, sudden death, cerebrovascular death, cardiac events, vascular events and renal events. The secondary endpoints were effects on left ventricular hypertrophy, cardiac sympathetic nerve activity and renal function. A total of 1021 patients were enrolled in the present trial. The mean follow-up period was 3.4 years. There were no significant differences in blood pressure (BP) levels between the valsartan group and the amlodipine group throughout the trial. There was no significant difference in the primary endpoint between the two groups (hazard ratio: 1.0, P = 0.843). No difference in any event category of the primary endpoint was noted for either group. However, we observed a significant reduction of left ventricular mass index, as determined by echocardiography, in the valsartan group compared with the amlodipine group. We also observed a significant decrease in cardiac sympathetic nerve activity in the valsartan group but not in the amlodipine group. Moreover, there was a significant reduction in the urinary albumin to creatinine ratio in the valsartan group but not in the amlodipine group. Therefore, although BP levels were well controlled and remained equal in the two groups, valsartan had more protective effects on the heart and kidney than amlodipine in Japanese hypertensive patients.

Valsartan Amlodipine Randomized Trial (VART): design, methods, and preliminary results.

Antihypertensive therapy has been well established to reduce hypertension related morbidity and mortality, but the optimal therapy for Japanese patients remains unknown. The Valsartan Amlodipine Randomized Trial (VART), a prospective randomized open-label trial, was designed to determine whether treatment with an angiotensin II type 1 receptor blocker (valsartan) or a calcium channel blocker (amlodipine) lowers cardiovascular disease events in essential hypertensives in Japan. Registration, randomization and data entry were performed over the Internet. The minimization method (to control for age, gender, blood pressure level and history) was used at random assignment to ensure that the background factors were equivalent between the groups at baseline. After the registration, patients were followed-up for cardiovascular events (primary endpoints), echocardiography, (123)I-metaiodobenzylguanidine (MIBG) imaging, laboratory tests and blood pressure for 3 years. Currently, 797 patients have been enrolled and assigned to two groups: a valsartan (n=399) and an amlodipine (n=398) group. At baseline, controlled factors (age, gender, blood pressure level, and left ventricular hypertrophy) and the proportions of patients with diabetes and hyperlipidemia were equally allocated. At 12 months, both drugs evenly and significantly lowered blood pressure to the target level (valsartan: 133/79 mmHg; amlodipine: 132/79 mmHg). In conclusion, by combining the data on cardiovascular events with the results of echocardiographic, radionuclide imaging, and blood/urine studies, the VART study will provide mechanistic insights into the clinical outcomes and treatment effects of the trial.

Feasibility and safety of granulocyte colony-stimulating factor treatment in patients with acute myocardial infarction.

BACKGROUND: This study examined feasibility and safety of granulocyte colony-stimulating factor (G-CSF) treatment for patients with acute myocardial infarction (AMI). METHODS: Forty patients with AMI related with the left anterior descending coronary artery, who underwent successful percutaneous coronary intervention (PCI), were randomized into G-CSF group (n=18) or Control group (n=22). G-CSF treatment was started within 24 h after PCI. 99mTc-tetrofosmin single-photon emission computed tomography (SPECT) was performed at 4 days and 6 months after AMI. SPECT data was analyzed for LV end-diastolic volume (LVEDV), LV end-systolic volume (LVESV), LV ejection fraction (LVEF) and myocardial perfusion. RESULTS: LVEF at 6 months was significantly better than that at 4 days in G-CSF group (p=0.013), but not changed in Control group (p=0.245). Although no significant difference was observed for LVEDV between the two groups, LVESV tended to be decreased only in G-CSF group. In G-CSF group, defect score (DS) was significantly decreased from 4 days to 6 months after AMI. Restenosis rate at 6 months after AMI was not significantly different between the two groups. CONCLUSIONS: G-CSF treatment for patients with AMI was effective and did not have any clinical and angiographic adverse effects.