Preparation of concentrated multilayer graphene dispersions and TiO2-graphene composites for enhanced hydrogen production

Photocatalytic hydrogen (H2) production is an attractive hydrogen production technology. It is initiated by charge-separation in titanium (IV) dioxide (TiO2) upon photoexcitation. Electrons reduce water to generate H2 while holes oxidize hydroxide to generate hydroxyl radicals. TiO2 is widely used because it is inexpensive, chemically stable, nontoxic, and environmentally friendly. The activity of TiO2 is limited, but adding a supporting noble metal nanoparticle such as platinum greatly enhances it. Due to resource risks and cost issues, we consider using graphene as an alternative to noble metal nanoparticles. Herein we report a new method to prepare a concentrated multilayer graphene solution and hydrogen production from an aqueous methanol solution. When we used graphene with different sheet sizes or improved the aggregation of TiO2 (TIO-9), the H2 evolution rate is 1.6 times higher than that of pristine TIO-9. The contact state and the dispersed state of graphene and TiO2 play important roles in improving the activity

A simulation environment to simulate lower-hybrid-wave-driven plasmas efficiently

In this study a hybrid simulation environment to investigate the lower-hybrid-wave-driven tokamak plasmas is presented, and its application to the spherical tokamak TST-2 is described. These plasma are formed and driven by radio-frequency waves without the use of the central solenoid, and are characterized by low density and low magnetic field. A hybrid simulation environment which is divided into two groups, one using magneto-hydrodynamic (MHD) as well as particle-in-cell (PIC) approaches, and the second group using ray-tracing and Fokker–Planck solvers, is applied to describe the behavior of energetic electrons, bulk plasma, wave propagation, and the wave-particle interaction. Both groups of solvers can be coupled via the energetic-particle velocity distribution function and the equilibrium conditions of magnetic field, pressure, and density profiles to obtain a self-consistent solution. First results show the impact of a self-consistent equilibrium on ray trajectories and current density profiles. Therefore, new insights in lower-hybrid-wave-driven plasmas of TST-2 can be obtained using the proposed hybrid simulation environment

Staged hybrid repair for a patient with chronic type B aortic dissection

Vascular prosthesis replacement and thoracic endovascular repair (TEVAR) are used to treat patients with enlarged chronic type B aortic dissection. A case in which thrombosis of the false lumen was achieved by the staged combination of these two methods is presented. A 41-year-old woman with a thoracoabdominal aortic aneurysm (maximum short diameter 44 mm) identified 5 years earlier was being monitored as an outpatient in our department when she presented with back pain. Computed tomography (CT) showed acute type B aortic dissection (DeBakey type IIIa), which was managed conservatively. When CT showed an aortic dissection with a patent false lumen immediately below the left subclavian artery bifurcation, one-debranching TEVAR was performed to close the entry, along with right axillary artery to left axillary artery bypass surgery. Outpatient CT at 3 months postoperatively showed rapid enlargement in the vicinity of the celiac artery. Thoracoabdominal aortic replacement to prevent rupture was performed, and the patient was then monitored as an outpatient. CT at age 43 years showed enlargement of the residual false lumen. Additional TEVAR was successfully performed. Thus, three-stage treatment was conducted to enlarge the residual false lumen, causing successful thrombosis of the false lumen

Long-term results of modified bentall procedures: 18-year experience of the flanged technique

Objectives: To evaluate the early and late outcomes of the modified Bentall procedure with the flanged technique. Methods: We reviewed the medical records of 63 patients who had undergone root replacement by the modified Bentall procedure at our institute between January 2001 and December 2018. In most cases, we adopted a composite graft constructed with a mechanical valve or bioprosthesis and a Dacron graft by the flanged technique. Since 2011, we have used Valsalva grafts. Results: Mean age 57 ± 16 years, range 16-80, male 43 cases. The mean follow-up was 75 ± 56 months (range 0-216). Through April 1, 2020, we could follow up on 61 cases (97%) within a six-month period. Hospital mortality was 7.9% (4.8% in elective cases). In late follow-up, eight deaths were observed. In the bio-Bentall group (n=26), no deaths or major adverse valve-related events (MARVEs) occurred. In the mechanical Bentall group (n=37), seven cases of MARVEs, including two cerebral hemorrhages and one cerebral embolism, were observed. All patients were free from MARVEs at 5 years post procedure in the bio-Bentall group, and 93.8% and 76.8% were event-free at 5 years and 10 years, respectively, in the mechanical Bentall group. Conclusions: The 18-year results of the modified Bentall procedure were acceptable, providing excellent outcomes in the bio-Bentall group. The flanged technique enabled the use of a larger prosthesis, which may have resulted in good durability with the bio-Bentall procedure