Unipolar transport in bilayer graphene controlled by multiple p-n interfaces

Unipolar transport is demonstrated in a bilayer graphene with a series of p-n junctions and is controlled by electrostatic biasing by a comb-shaped top gate. The OFF state is induced by multiple barriers in the p-n junctions, where the band gap is generated by applying a perpendicular electric field to the bilayer graphene, and the ON state is induced by the p-p or n-n configurations of the junctions. As the number of the junction increases, current suppression in the OFF state is pronounced. The multiple p-n junctions also realize the saturation of the drain current under relatively high source-drain voltages.Comment: 18 pages, 4 figures, Applied Physics Letters, in printin

Influence of Deposition Condition on Y 2

Y2O3 nanoparticle suspension aqueous solution was prepared using citric acid. Then, Y2O3 film was deposited using this solution with pulsed electrophoretic deposition (EPD). A dense Y2O3 film of 25.7 μm thickness was obtained with deposition conditions of 0.5 wt% Y2O3 concentration, bias voltage of 0.5 V, and bias frequency of 1 kHz. The respective resistivities of the as-deposited film and films heat-treated at 200°C and 400°C were 2.84 × 103 Ω·cm, 5.36 × 104 Ω·cm, and 2.05 × 106 Ω·cm. A 59.8 μm thick dense Y2O3 film was obtained using two-step deposition with change of the bias voltage: a first step of 0.5 V and a second step of 2.0 V

Risk of bleeding and repeated bleeding events in prasugrel-treated patients: a review of data from the Japanese PRASFIT studies

Prasugrel is a third-generation thienopyridine that achieves potent platelet inhibition with less pharmacological variability than other thienopyridines. However, clinical experience suggests that prasugrel may be associated with a higher risk of de novo and recurrent bleeding events compared with clopidogrel in Japanese patients undergoing percutaneous coronary intervention (PCI). In this review, we evaluate the risk of bleeding in Japanese patients treated with prasugrel at the doses (loading/maintenance doses: 20/3.75 mg) adjusted for Japanese patients, evaluate the risk factors for bleeding in Japanese patients, and examine whether patients with a bleeding event are at increased risk of recurrent bleeding. This review covers published data and new analyses of the PRASFIT (PRASugrel compared with clopidogrel For Japanese patIenTs) trials of patients undergoing PCI for acute coronary syndrome or elective reasons. The bleeding risk with prasugrel was similar to that observed with the standard dose of clopidogrel (300/75 mg), including when bleeding events were re-classified using the Bleeding Academic Research Consortium criteria. The pharmacodynamics of prasugrel was not associated with the risk of bleeding events. The main risk factors for bleeding events were female sex, low body weight, advanced age, and presence of diabetes mellitus. Use of a radial puncture site was associated with a lower risk of bleeding during PCI than a femoral puncture site. Finally, the frequency and severity of recurrent bleeding events during continued treatment were similar between prasugrel and clopidogrel. In summary, this review provides important insights into the risk and types of bleeding events in prasugrel-treated patients. Trial registration numbers: JapicCTI-101339 and JapicCTI-111550

Transient left ventricular apical ballooning without coronary artery stenosis: a novel heart syndrome mimicking acute myocardial infarction

AbstractOBJECTIVESTo determine the clinical features of a novel heart syndrome with transient left ventricular (LV) apical ballooning, but without coronary artery stenosis, that mimics acute myocardial infarction, we performed a multicenter retrospective enrollment study.BACKGROUNDOnly several case presentations have been reported with regard to this syndrome.METHODSWe analyzed 88 patients (12 men and 76 women), aged 67 ± 13 years, who fulfilled the following criteria: 1) transient LV apical ballooning, 2) no significant angiographic stenosis, and 3) no known cardiomyopathies.RESULTSThirty-eight (43%) patients had preceding aggravation of underlying disorders (cerebrovascular accident [n = 3], epilepsy [n = 3], exacerbated bronchial asthma [n = 3], acute abdomen [n = 7]) and noncardiac surgery or medical procedure (n = 11) at the onset. Twenty-four (27%) patients had emotional and physical problems (sudden accident [n = 2], death/funeral of a family member [n = 7], inexperience with exercise [n = 6], quarreling or excessive alcohol consumption [n = 5] and vigorous excitation [n = 4]). Chest symptoms (67%), electrocardiographic changes (ST elevation [90%], Q-wave formation [27%] and T-wave inversion [97%]) and elevated creatine kinase (56%) were found. After treatment of pulmonary edema (22%), cardiogenic shock (15%) and ventricular tachycardia/fibrillation (9%), 85 patients had class I New York Heart Association function on discharge. The LV ejection fraction improved from 41 ± 11% to 64 ± 10%. Transient intraventricular pressure gradient and provocative vasospasm were documented in 13/72 (18%) and 10/48 (21%) of the patients, respectively. During follow-up for 13 ± 14 months, two patients showed recurrence, and one died suddenly.CONCLUSIONSA novel cardiomyopathy with transient apical ballooning was reported. Emotional or physical stress might play a key role in this cardiomyopathy, but the precise etiologic basis still remains unclear

Static magnetic order in Na0.75_{0.75}CoO2_2 detected by muon spin rotation and relaxation

The nature of the magnetic transition of the Na-rich thermoelectric Na$_{0.75}$CoO$_2$ at 22K was studied by positive muon-spin-rotation and relaxation ($\mu^+$SR) spectroscopy, using a polycrystalline sample in the temperature range between 300 and 2.5 K. Zero field $\mu$SR measurements indicated the existence of a static internal magnetic field at temperatures below 22 K (= $T_{\rm m}$). The observed muon spin precession signal below $T_{\rm m}$ consisted of three components with different precession frequencies, corresponding to three inequivalent muon$^+$ sites in the Na$_{0.75}$CoO$_2$ lattice. The total volume fraction of the three components was estimated as $\sim$21% at 2.5 K; thus, this magnetic transition was not induced by impurities but is an intrinsic change in the magnetism of the sample, although the sample was magnetically inhomogeneous otherwise. On the other hand, a similar experiment on a Na$_{0.65}$CoO$_2$ sample exhibited no magnetic transition down to 2.5 K; which indicates that the average valence of the Co ions is responsible for inducing the magnetic transition at 22 K.Comment: 5 pages, 4 figures, Phys. Rev. B 68 (2003) in pres