A multidisciplinary heart team is considered safe and effective in determining treatment strategies. Indications for transcatheter aortic valve replacement have expanded from high-risk to low-risk ...patients, reducing the role of surgeons as gatekeepers. In recent years, opportunities for heart team meetings have been drastically reduced due to work style reform and avoidance of the three Cs （closed spaces, crowded places, and close-contact settings）. We conducted a questionnaire survey in each department because we were concerned about restrictions affecting heart team communication. According to our findings, most participants felt that the heart team was both necessary and functioning effectively. Although restrictions have increased, it is important to continue maintaining good communication between departments.
Japan has one of the most well-equipped telecommunications infrastructures in the world. The rich Japanese information environment is the result of a long telecommunications infrastructure ...construction process. This paper describes the historical process of the development of Japan’s telecommunications infrastructure from the introduction of telegraph technology in the late 19th century to the recent expansion of mobile broadband. From the early stage of the construction of telegraph networks, an efficient geographical configuration for Japan’s international telecommunications has been sought. First, a westward route to European countries was built at the beginning of telegraph services and then the eastward route connected directly to the United States was opened. During the construction of the international coaxial submarine cables after World War II, the combined use of the westward and eastward telecommunications routes similar to the early international telegraph networks was retained. In the early 2000s, ultra-high-speed trans-Pacific telecommunications networks were constructed corresponding to rapid expansion of Internet use. The main route of Japan’s international communications shifted to the eastward one. In contrast, the geographical configuration of the domestic telecommunications in Japan has been essentially unchanged. The domestic telegraph networks had been steadily expanded from the large metropolises to local cities from the end of the 19th century to the early 20th century. Even the recent optical fiber networks maintain a similar configuration. Although new broadband services, e.g., DSL, optical fiber and mobile telecommunications, were installed corresponding to the expansion of Internet use, the geographical configuration of domestic telecommunications networks has been kept.
Background:The effect of multiple prior percutaneous coronary interventions (PCIs) before subsequent coronary artery bypass grafting (CABG) on long-term outcomes has not been well elucidated.Methods ...and Results:Between 2007 and 2016, 1,154 patients undergoing primary isolated CABG in our institution had no prior PCI (Group N), 225 had a single prior PCI (Group S), and 272 had multiple prior PCIs (Group M). Cumulative incidences of all-cause death, cardiac death and myocardial infarction (MI) at 10 years post-CABG were highest in Group M. After adjusting for confounders, the risk of all-cause death was higher in Group M than in Group N (hazard ratio HR 1.45; 95% confidence interval CI, 1.10–1.91; P<0.01). Between Groups N and S, however, the risk of all-cause death was not different. The risks of cardiac death and MI were likewise higher in Group M than in Group N (HR, 2.39; 95% CI, 1.55–3.71; P<0.01 and HR, 3.65; 95% CI, 1.16–11.5; P=0.03, respectively), but not different between Groups N and S. The risk of repeat revascularization was not different among any of the groups.Conclusions:Multiple prior PCIs was associated with higher risks of long-term death and cardiovascular events. The incidence of repeat revascularization after CABG was low regardless of the history of single/multiple PCIs.
To evaluate the accuracy and consistency of a gradient-based positron emission tomography (PET) segmentation method, GRADIENT, compared with manual (MANUAL) and constant threshold (THRESHOLD) ...methods.
Contouring accuracy was evaluated with sphere phantoms and clinically realistic Monte Carlo PET phantoms of the thorax. The sphere phantoms were 10-37 mm in diameter and were acquired at five institutions emulating clinical conditions. One institution also acquired a sphere phantom with multiple source-to-background ratios of 2:1, 5:1, 10:1, 20:1, and 70:1. One observer segmented (contoured) each sphere with GRADIENT and THRESHOLD from 25% to 50% at 5% increments. Subsequently, seven physicians segmented 31 lesions (7-264 mL) from 25 digital thorax phantoms using GRADIENT, THRESHOLD, and MANUAL.
For spheres <20 mm in diameter, GRADIENT was the most accurate with a mean absolute % error in diameter of 8.15% (10.2% SD) compared with 49.2% (51.1% SD) for 45% THRESHOLD (p < 0.005). For larger spheres, the methods were statistically equivalent. For varying source-to-background ratios, GRADIENT was the most accurate for spheres >20 mm (p < 0.065) and <20 mm (p < 0.015). For digital thorax phantoms, GRADIENT was the most accurate (p < 0.01), with a mean absolute % error in volume of 10.99% (11.9% SD), followed by 25% THRESHOLD at 17.5% (29.4% SD), and MANUAL at 19.5% (17.2% SD). GRADIENT had the least systematic bias, with a mean % error in volume of -0.05% (16.2% SD) compared with 25% THRESHOLD at -2.1% (34.2% SD) and MANUAL at -16.3% (20.2% SD; p value <0.01). Interobserver variability was reduced using GRADIENT compared with both 25% THRESHOLD and MANUAL (p value <0.01, Levene's test).
GRADIENT was the most accurate and consistent technique for target volume contouring. GRADIENT was also the most robust for varying imaging conditions. GRADIENT has the potential to play an important role for tumor delineation in radiation therapy planning and response assessment.
•The work-hardening of AA6061-T6 between room temperature to 500 °C is investigated.•Diffuse necking is observed early on in the elevated temperature tests.•The work-hardening curves are identified ...using a finite element model of necking.•Rate-dependence is necessary for the work-hardening curves at elevated temperatures.•Swift/Voce with Johnson-Cook strain-rate dependence is sufficient and very accurate.
The temperature-dependent work-hardening of AA6061-T6 aluminum alloy is investigated using a combined experimental-numerical approach. Uniaxial tension experiments are performed from room temperature to 500 °C, and the force-displacement curves up to fracture are established. Both the yield strength and the work-hardening rate of the material decrease with increasing temperature. Despite the marked increase in the elongation-to-fracture, the uniform elongation remains limited, indicating the early appearance of diffuse necking in the elevated temperature tests. A simplified technique for identifying the work-hardening curves at elevated temperatures and beyond the limit of uniform deformation in uniaxial tension is proposed. The technique uses an isothermal, rate-dependent, finite element (FE) model of the experiments. The post-necking hardening curve is represented by a hybrid Swift/Voce hardening law combined with a form of Johnson-Cook strain-rate dependence. To identify the material model parameters at each temperature, an objective function that correlates the experimental and FE-predicted force-displacement curves is constructed and minimized. These model parameters are then fit with Fourier series across the temperature range considered here, providing smooth functions suitable for subsequent implementation in FE analyses of forming and structural problems. As an illustration, it is shown that a FE model utilizing these material parameters reproduces the full-field features of the elevated temperature experiments very well.
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The present study proposes a method to predict the burst pressures (BPs) of type III filament winding carbon fiber-reinforced plastic (CFRP) composite pressure vessels considering the inhomogeneity ...of carbon fiber packing through experimental work and simplified mechanical models reflecting the evolution of local damage in the CFRP layers. Vessels that had different carbon fiber volume fractions (Vfs) were prepared and tested to measure their BPs. The inhomogeneity of carbon fiber packing was evaluated using Weibull probability based on the microscopic observation of CFRP cross-sections in the virgin vessels. Detailed stress analyses of pressurized composite vessels considering the carbon Vf were conducted. Unstable fracture of the hoop layer was demonstrated by a simplified mechanical model combined with the inhomogeneity of the carbon Vf and de-bonding between the fiber and matrix. About 20% difference in the BP was measured between tested vessels with and without glass fiber-reinforced plastic layers over CFRP layers. The proposed method for predicting the BP based on the constant stress model enables consideration of the development of local fiber breaking prior to catastrophic fracture and to quantitatively estimate the change in the BP due to the difference in Vf.
Background
Stereotactic radiosurgery (SRS) has become a primary option for management for both newly diagnosed vestibular schwannomas (VS), as well as VS that enlarge after initial observation.
...Methods
A retrospective review of our prospectively maintained data base found 871 patients who underwent Gamma knife® SRS as their initial (primary) management between 1987 and 2008. Follow-up ranged from 1–25 years (median = 5.2 years) Median tumor volume was 0.9 cc (0.02–36) and median margin dose was 13 Gy (12–25).
Results
Progression free survival (PFS) after SRS was 97% at 3 years, 95% at 5 years, and 94% at 10 years. Freedom from delayed surgical resection was found in 98.7% of patients. Smaller tumor volume was significantly associated with improved PFS. There were 326 patients with serviceable hearing (Gardner–Robertson 1 or 2) at the time of SRS with audiological follow-up of ≥ 1 year. Serviceable hearing preservation rates after SRS were 89.8% at 1 year, 76.9% at 3 years, 68.4% at 5 years, 62.5% at 7 years, and 51.4% at 10 years. Factors associated with improved serviceable hearing preservation included younger age, Gardner-Robertson grade 1 at SRS, and absence of subjective complaints of dysequilibrium or vertigo (vestibulopathy). Fifty-one patients (5.8%) developed trigeminal neuropathy. Fourteen (1.6%) developed a transient House-Brackmann grade 2 or 3 facial neuropathy.
Conclusions
In this report with extended follow-up, primary SRS achieved tumor growth control in 94% of patients. Optimization of long- term cranial nerve outcomes remains an important achievement of this management strategy for VS.
The primary objective of this study is to predict the geometric shape and thickness change during multi-pass tube spinning to a hemispherical shape. A computationally efficient, axisymmetric finite ...element model of the tube-spinning experiments is described. Uniaxial tensile tests are conducted for the development of the material model. The post-necking hardening curve is identified using a hybrid experimental-numerical method and represented by a combined Swift-Voce model. For validation of the finite element model, spinning experiments are performed at room temperature on thin-walled cylinders of 6061-O aluminum alloy. The experiments are interrupted after spinning passes 2, 4, 6, and 8 and the shape and thickness are measured. Also, local strain measurements on the final spun tube (pass 8) are accomplished by a scribed grid. By comparing the predictions to the experiments, good agreement is obtained on the shape, thickness, and strain evolution in multi-pass spinning. The deformation mechanism of this process is described by analyzing the history of plastic strain on an element of the numerical model.
This paper investigates the effect of friction on the buckling behavior of a thin, shallow, elastic spherical shell under uniform external pressure based on an axisymmetric model of the finite ...element method. The study examines a combination of different geometric parameters with three different types of boundary conditions: clamped, hinged, and frictional ends with a wide range of friction coefficients. Friction has a significant influence on the buckling response of the spherical shell for all geometric parameters. In general, the critical pressure decreases as the friction coefficient or geometric parameter decreases. The buckling behavior of the frictional end with small friction coefficients presents an obvious difference compared to the results of high coefficients. For certain geometric parameters, the buckling mode of the spherical shell is transited because of changing the friction coefficient. A buckling map that describes the dependence of critical pressure on both friction coefficient and geometric parameter combined with buckling mode is generated. This map can be applied to the design of the spherical shell against buckling.
In this research, the effect of residual stress on the fatigue crack growth behavior in an aluminum alloy-hybrid metal matrix composite (Al alloy-Hybrid MMC) bi- material system has been investigated ...and the fatigue life of the bi-material has been predicted based on the crack closure technique. Conventional three-point bending fatigue test was carried out in a rectangular notched specimen and the plastic replica technique was used to observe the fatigue crack growth (FCG). The residual stress was measured by the strain relieving method. The fatigue life was predicted by classifying the expression of FCG rate and the effective stress intensity factor, ΔKeff. The results show that the crack propagates slowly in the MMC layer side and maximum crack retardation occurs in the boundary region of the bi-material system due to the change of the state of residual stresses around the boundary. A curved crack front is observed in the aluminum alloy side near the boundary of the bi-material which forms a corner crack that decelerates the crack growth in the vicinity of the boundary of the bi-material even at higher ΔK.
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