Embedded DRAM using c-axis-aligned crystalline In-Ga-Zn oxide FET with 1.8V-power-supply voltage

An embedded memory using c-axis aligned crystalline In-Ga-Zn oxide (CAAC-IGZO) FETs with an extremely low off-state current on the order of yoctoamperes (yA) (yocto- is a metric prefix denoting a factor of 10-24) is known as a potential next-generation memory [1][2]. A dynamic oxide semiconductor RAM (DOSRAM), where each memory cell is composed of one CAAC-IGZO FET and one capacitor, enables long data retention and long interval of refresh operations with an advantage of extremely low off-state current of the CAAC-IGZO FET. However, negative backgate voltage (Vbg) and word-line driving voltages of 0/3.3 V (VSSL/VDDH) had been required for an access transistor of the memory cell to satisfy high on-state current and low off-state current. This work shows that DOSRAM operates with 1.8 V-power supply voltage by using a novel driving method. Figure 1 shows Vg-Id performance of a CAAC-IGZO FET used as a cell transistor. The threshold voltage (Vth) of the CAAC-IGZO FET is controlled by changing a level of Vbg, whereas Vth of the Si FET is controlled by channel doping. Figure 2 shows a block diagram of a prototyped DOSRAM. The refresh rate in DOSRAM mainly depends on the leakage current of cell transistors. To reduce the refresh rate to once an hour, the off-state current of the cell transistors on a non-selected word line needs to be reduced to 200 zeptoamperes (zA) per FET (zepto- is a metric prefix denoting a factor of 10-21) or lower at 85C. The required Vbg is -7.0 V to achieve such an off-state current at Vg 0 V, for example. To obtain approx. 100 MHz-driving frequency, the required on-state current is at least several microamperes. The voltage level difference in the word line, VDDH VSSL, is a factor that determines the on-state current, and in this work is fixed to 3.3 V so that the combination of Vbg and the word line voltage is optimized. The application of negative voltage to the word line enables the leakage current of the cell transistor to be maintained low even when Vbg is increased. For example, whereas the existing driving method meets the above off-state current value with Vbg -7.0 V and the VSSL 0 V, the novel driving method meets the value with Vbg 0 V and VSSL -1.5 V. In the novel driving method, VDDH 1.8 V. There has been a report of a reduction in leakage current of a memory cell by application of negative voltage to a top gate in DRAM using Si CMOS [3]. In contrast to it, DOSRAM including CAAC-IGZO FETs with L 60 nm has a leakage current of 200 zA or lower, which is 7-digit lower than that of the DRAM using Si CMOS, and enables longer data retention. The evaluation results of the prototyped DOSRAM verify that a reduction in power-supply voltage from 3.3 V to 1.8 V is possible in terms of operation and data retention. This suggests a highly compatible and efficient configuration of an embedded DRAM and a logic circuit where signals can be transmitted with low VDD. References [1] S. H. Wu, et al., IEEE Symp. VLSI Tech., pp. 166-167, 2017. [2] T. Ishizu, et al., IEEE Symp. VLSI Cir., pp. 162-163, 2017. [3] F. Hamzaoglu et al., IEEE Journal of Solid-State Circuits, vol. 50, no. 1, pp. 150-157, Jan. 2015

Quadrupolar effect and rattling motion in heavy fermion superconductor PrOs_4Sb_{12}

The elastic properties of a filled skutterudite PrOs_4Sb_{12} with a heavy Fermion superconductivity at T_C=1.85 K have been investigated. The elastic softening of (C_{11}-C_{12})/2 and C_{44} with lowering temperature down to T_C indicates that the quadrupolar fluctuation due to the CEF state plays a role for the Cooper paring in superconducting phase of PrOs_4Sb_{12}. A Debye-type dispersion in the elastic constants around 30 K revealed a thermally activated Gamma_{23} rattling due to the off-center Pr-atom motion obeying tau=tau_{0}exp(E/k_{B}T) with an attempt time tau_0=8.8*10^{-11} sec and an activation energy E=168 K. It is remarkable that the charge fluctuation of the off-center motion with Gamma_{23} symmetry may mix with the quadrupolar fluctuation and enhance the elastic softening of (C_{11}-C_{12})/2 just above T_C.Comment: 5 pages, 4 figures, to be published to Phys. Rev.

Effect of Implantable Cardioverter-defibrillator Therapy for Ventricular Fibrillation Patients with Out-of-hospital Cardiac Arrest

Survivors of ventricular fibrillation out-of-hospital cardiac arrest（VF-OHCA）due to potentially reversible causes such as acute coronary syndrome（ACS）, vasospastic angina and electrolyte abnormalities are considered low risk for recurrent arrhythmia. Accordingly, implantable cardioverter-defibrillator therapy is not routinely recommended in such patients. We investigated the risk of mortality and the value of ICD therapy for VF-OHCA. Among 2,248 cardiopulmonary arrest patients presenting at our hospital, we retrospectively investigated 110 patients with VF-OHCA who were admitted for treatment. We divided the patients based on ICD（n＝71） or No-ICD status（n＝39）, and on reversible cause（n＝70） or irreversible cause（n＝40）. The groups were compared for baseline characteristics, mortality and ICD therapies. Patients with a reversible cause had a significantly lower rate of ICD implantation than those with an irreversible cause（P＝0.03）. Males in the ICD group presented more frequently than those in the No-ICD group, and cardiac mortality in patients with acute coronary syndrome was significantly lower with ICD therapy than without ICD（P＝0.04）. The rate of appropriate ICD therapies with a reversible cause was 28％, and the first ICD therapy was highest within 1 year post-implantation. Patients with VF-OHCA due to a reversible cause remain at high risk of recurrent ventricular arrhythmias, suggesting that ICD implantation is a reasonable approach in such cases

Head-up Tilt Test May Be Useful for Determining Permission of Flight for Regular Passenger Aircraft Pilots with Vasovagal Syncope

To determine the permissibility of piloting an aircraft with vasovagal syncope （VVS） is a complex responsibility, because it is difficult to evaluate VVS quantitatively. There are no clear guidelines for aircraft pilots with VVS. In some facilities, Head-up Tilt Test （HUTT） is used to determine its reproducibility and treatment effect. In most cases, permission is dependent on the strict examinations by specialists and judgement of the committee established for each country. Therefore, we assessed pilots with VVS and designed an algorism of permission for piloting an aircraft. Here, we describe 7 consecutive regular passenger aircraft pilots with VVS who were restricted to fly. All patients were men and their mean age was 37 years. All pilots were permitted to fly after at least two or more tilt-tests. The observation period was two years after flight permission. None of the pilots in the present study fainted after receiving flight permission. We can make a risk stratification to determine hypotensive susceptibility by multiple tilt tests. Based on the results of multiple HUTT, we can more quantitatively make the judgement as to whether the pilot’s VVS is well managed

Epicardial Adipose Tissue in the Right Atrium Is Associated with Progression of Atrial Fibrillation and Recurrence after Pulmonary Vein Catheter Ablation in Patients with Atrial Fibrillation

An increase in epicardial adipose tissue（EAT）in the left atrium（LA）predicts the progression of atrial fibrillation（AF）and AF recurrence after pulmonary vein catheter ablation（CA）. We hypothesized that EAT in the right atrium（RA）is also associated with the progression of AF and post-CA AF recurrence. Using 128-slice multidetector computed tomography, EAT volume and atrial volume were measured 3-dimensionally before CA in 68 patients who had proven AF（paroxysmal AF, 42; persistent AF, 26; mean age, 65±11 years; 42.6％ female）with successful CA and 21 volunteers with sinus rhythm（age, 63±13 years; 52.3％ female）. In both atria, EAT and atrial volumes were largest in patients with persistent AF, followed, in order, by those with paroxysmal AF, and then healthy volunteers（P＜0.001）. Increased EAT and atrial volumes in both atria predicted persistent AF（P＜0.001）. Fifteen patients had AF recurrence（22.1％）during the 2-year period after CA. Increased EAT volume in both atria were independent predictors for AF recurrence, and a RA EAT volume≥6.2ml was an independent predictor, with a hazard ratio of 5.47（95％ confidence interval, 1.2-24.3; P=0.03）. The combination of EAT and atrial volume in both atria was a more powerful independent prognostic factor, with a hazard ratio of 4.8（95％ confidence interval, 1.7-3.7; P=0.003）, and a sensitivity of 60％ in 9 of 15 patients, and specificity of 81.1％ in 43 of 53 patients,（P=0.003）. RA EAT is associated with the progression of AF and post-CA AF recurrence

Recurrence of Atrial Fibrillation within Three Months after Pulmonary Vein Isolation in Patients with Paroxysmal Atrial Fibrillation : Analysis Using an External Loop Recorder with Auto-trigger Function

Pulmonary vein isolation (PVI) via catheter ablation has been shown to be a highly effective option for patients with symptomatic paroxysmal atrial brillation (AF). The recurrence of AF within 3 months after PVI is not considered a failure of the ablation procedure because early recurrence of AF is not always associated with late recurrence. We examined the usefulness of an external loop recorder with auto-trigger function (ELR-AUTO) to detect AF following PVI to characterize early recurrence and determine the implication of AF within 3 months after PVI. The study included 53 consecutive patients with symptomatic paroxysmal AF (age, 61.6 ± 12.6 years ; 77％ male) who underwent PVI, and were fitted with an ELR-AUTO for 7 ± 2 days within 3 months after PVI. Of the 33 patients(62.2％) who did not have AF within the 3-month period, only 1 patient had AF recurrence at 12 months. Seven of 20 patients (35％) who experienced AF within 3 months had symptomatic AF recurrence at 12 months. The sensitivity, specificity, positive predictive value, and negative predictive value of early AF recurrence for late recurrence was 87.5％, 71.1％, 35.0％, and 96.9％, respectively. Thus, AF recurrence detected by ELR-AUTO within 3 months after PVI can predict late AF recurrence. Freedom from AF in the firrst 3 months following ablation significantly predicts long-term freedom from AF. An ELR-AUTO is useful for detecting symptomatic and asymptomatic AF

Four Redox Isomers of a [3 × 3] Copper–Iron Heterometal Grid

A mixed-valence heterometallic nonanuclear [3 × 3] grid complex, [CuI2CuII6FeIII(L)6](BF4)5·MeOH·9H2O (1; MeOH = methanol), was synthesized by a one-pot reaction of copper and iron ions with multidentate ligand 2,6-bis[5-(2-pyridinyl)-1H-pyrazol-3-yl]pyridine (H2L). 1 showed five quasi-reversible one-electron redox processes centered at +0.74, +0.60, +0.39, +0.27, and −0.13 V versus SCE, assignable to four CuI/CuII processes and one FeII/FeIII couple, respectively. The two-electron-oxidized species [CuII8FeIII(L)6](PF6)7·4MeOH·7H2O (12eOx), the two-electron-reduced species [CuI4CuII4FeIII(L)6](PF6)3·2H2O (12eRed), and the three-electron-reduced species [CuI4CuII4FeII(L)6](PF6)2·5MeOH·H2O (13eRed) were isolated electrochemically. The four redox isomers were characterized by single-crystal X-ray analysis, SQUID magnetometry, and Mössbauer spectroscopy